Radar device, radar signal generating device, and radar signal generating method

Abstract

To improve the detection accuracy of a target object in a radar device.SOLUTION: A radar device includes: a plurality of transmitting antennas including a first transmitting antenna that emits a first polarized wave and a second transmitting antenna that emits a second polarized wave that is different from the first polarized wave; and a transmitting circuit that multiply transmits, from the plurality of transmitting antennas, transmission signals that have been given phase rotations corresponding to the amounts of Doppler shift assigned to the respective transmitting antennas. Doppler multiplexing intervals by the plurality of transmitting antennas are unequal on the Doppler frequency axis. A first pattern of the amount of Doppler shift allocated to the first transmitting antenna and a second pattern of the amount of Doppler shift allocated to the second transmitting antenna are different.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a radar device. [Background technology]

[0002] In recent years, radar devices using short-wavelength radar transmission signals, including microwaves and millimeter waves, which can provide high resolution, have been studied. Furthermore, to improve outdoor safety, there is a demand for the development of radar devices that can detect small objects, such as pedestrians, over a wide angle range (e.g., called wide-angle radar devices).

[0003] A radar device having a wide detection range may be configured to receive reflected waves from a target using an array antenna composed of multiple antennas (also called antenna elements), and estimate the direction of arrival (also called the angle of arrival) of the reflected waves from the target based on the received phase difference relative to the element spacing (antenna spacing) (Direction of Arrival (DOA) estimation). Examples of DOA estimation methods include the Fourier method, or methods that can achieve high resolution, such as the Capon method, MUSIC (Multiple Signal Classification), and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques).

[0004] Furthermore, a radar device has been proposed that includes, for example, a receiver and a transmitter that are equipped with multiple antennas (array antennas), and that performs beam scanning by signal processing using the transmit and receive array antennas (sometimes referred to as MIMO (Multiple Input Multiple Output) radar) (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Publication No. 2019 / 0064337 [Patent Document 2] U.S. Patent Publication No. 2020 / 0363497 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2008 - 304417 [Patent Document 4] Japanese Patent Application Publication No. 2011 - 526371 [Patent Document 5] Japanese Unexamined Patent Application Publication No. 2011 - 119344 [Patent Document 6] Japanese Unexamined Patent Application Publication No. 2019 - 052952 [Patent Document 7] Japanese Unexamined Patent Application Publication No. 2020 - 148754 [Non - Patent Document]

[0006] [Non - Patent Document 1] J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106 - 114, 2007 [Non - Patent Document 2] M. Kronauge, H.Rohling, "Fast two - dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817 - 1823 [Non - Patent Document 3] Direction - of - arrival estimation using signal subspace modeling Cadzow, J.A.; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1 Publication Year: 1992, Page(s): 64 - 79 [Summary of the Invention] [Problem to be solved by the invention]

[0007] However, methods for detecting targets in radar devices (for example, MIMO radars) have not been fully studied.

[0008] Non-limiting examples of the present disclosure contribute to providing a radar device that improves target detection accuracy. [Means for solving the problem]

[0009] A radar device according to an embodiment of the present disclosure includes a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave, and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which phase rotations corresponding to Doppler shift amounts assigned to each of the plurality of transmitting antennas have been imparted, wherein Doppler multiplexing intervals for the plurality of transmitting antennas are unevenly spaced on a Doppler frequency axis, and a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna.

[0010] These comprehensive or specific embodiments may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0011] According to an embodiment of the present disclosure, it is possible to improve the detection accuracy of a target in a radar device.

[0012] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0013] [Figure 1] A diagram showing an example of time division multiplexing (TDM) transmission [Figure 2] A diagram showing an example of Doppler Division Multiplexing (DDM) transmission [Figure 3] FIG. 1 shows an example of non-uniform Doppler multiplex transmission. [Figure 4] FIG. 1 shows an example of Doppler multiplexing. [Figure 5] Block diagram showing an example of the configuration of a radar device [Figure 6] FIG. 10 is a diagram showing an example of a transmission signal when a chirp signal is used. [Figure 7] A diagram showing an example of a chirp signal [Figure 8] FIG. 1 is a diagram showing an example of a transmission signal and a reception signal when a chirp signal is used. [Figure 9] A diagram showing an example of setting the Doppler shift amount [Figure 10] FIG. 10 is a diagram showing an example of a received signal in Doppler multiplex transmission. [Figure 11] A diagram showing an example of setting the Doppler shift amount [Figure 12] FIG. 10 is a diagram showing an example of a received signal in Doppler multiplex transmission. [Figure 13] A diagram showing an example of setting the Doppler shift amount [Figure 14] A diagram showing an example of setting the Doppler shift amount [Figure 15] A diagram showing an example of setting the Doppler shift amount [Figure 16] A diagram showing an example of setting the Doppler shift amount [Figure 17]Flowchart showing an example of the operation of separating Doppler multiplexed signals [Figure 18] Block diagram showing an example of the configuration of a radar receiver [Figure 19] A diagram showing an example of setting the Doppler shift amount [Figure 20] A diagram showing an example of setting the Doppler shift amount [Figure 21] A diagram showing an example of setting the Doppler shift amount [Figure 22] Block diagram showing an example of the configuration of a radar device DETAILED DESCRIPTION OF THE INVENTION

[0014] A MIMO radar transmits signals (radar transmission waves) multiplexed using, for example, time division, frequency division, or code division from multiple transmitting antennas (also called transmitting array antennas), receives signals (radar reflected waves) reflected by surrounding objects using multiple receiving antennas (also called receiving array antennas), and separates and receives the multiplexed transmission signals from each received signal. Through this processing, the MIMO radar can extract a propagation path response expressed as the product of the number of transmitting antennas and the number of receiving antennas, and performs array signal processing on these received signals as a virtual receiving array. In addition, in MIMO radar, by appropriately arranging the element spacing in the transmitting and receiving array antennas, the antenna aperture of the virtual receiving array can be enlarged, thereby improving angular resolution.

[0015] [About polarimetric radar] Furthermore, there is a technology for improving radar detection or discrimination performance by using an antenna that emits radio waves of different polarizations or an antenna that receives radio waves of different polarizations (see, for example, Patent Documents 3 or 4). A radar device that uses multiple polarized waves is also called, for example, a "polarimetric radar."

[0016] For example, Patent Document 1 and Patent Document 2 disclose a method for detecting and identifying an object by transmitting a transmission signal from an antenna using vertical polarization or horizontal polarization and using the signal received by an antenna using vertical polarization or horizontal polarization. Patent Document 2 also discloses a method for detecting and identifying an object by transmitting a transmission signal from an antenna using left-handed circular polarization or right-handed circular polarization and using the signal received by an antenna using left-handed circular polarization or right-handed circular polarization. Antennas that use linear polarization such as vertical polarization or horizontal polarization, or circular polarization such as left-handed circular polarization or right-handed circular polarization are also called "polarized antennas."

[0017] Such polarimetric radars use a number of different types of polarized antennas (eg, polarized transmit antennas or polarized receive antennas).

[0018] In the following, attention will be focused on a multiplexing method in a MIMO radar that uses a plurality of different types of polarized antennas (also called "polarized MIMO radar" for example).

[0019] [About time division multiplexing transmission] For example, time division multiplexing (TDM) is a multiplexing transmission method for MIMO radar using multiple transmitting antennas, in which signals are transmitted by shifting the transmission time for each transmitting antenna. Compared with frequency division multiplexing (FDM) and code division multiplexing (CDM), time division multiplexing can be realized with a simpler configuration, and by sufficiently widening the transmission time interval, it is possible to maintain good orthogonality between transmitted signals.

[0020] For example, a MIMO radar using time division multiplexing disclosed in Patent Document 3 outputs transmission pulses, which are an example of transmission signals, while sequentially switching transmission antennas that transmit transmission signals (e.g., transmission pulses or radar transmission waves) at a specified period. The MIMO radar using time division multiplexing receives signals that are the transmission pulses reflected by an object using multiple receiving antennas, and after correlation processing between the received signals and the transmission pulses, performs, for example, spatial FFT (Fast Fourier Transform) processing (processing to estimate the arrival direction of the reflected waves).

[0021] In a MIMO radar using time division multiplexing, a specified transmission time (or transmission interval) is assigned in advance to each of a plurality of transmitting antennas. Therefore, a polarized MIMO radar using time division multiplexing receives reflections from a target for each transmission time assigned to a plurality of transmitting antennas with different polarizations, thereby separating and receiving reflected waves from the target corresponding to the transmission signals for each transmitting antenna with different polarizations.

[0022] In a MIMO radar using time division multiplexing, the transmitting antennas that transmit radar transmission waves are sequentially switched at regular intervals. Therefore, the time required for transmission from all transmitting antennas to be completed tends to be longer than in a case using frequency division multiplexing or code division multiplexing. Therefore, in a MIMO radar using time division multiplexing, when multiple radar transmission waves are transmitted from each transmitting antenna and Doppler frequency detection (e.g., relative velocity detection) is performed based on the received phase changes of the transmitted waves (e.g., FIG. 4 of Patent Document 4), the time interval for observing the received phase changes when applying Fourier frequency analysis for Doppler frequency detection (e.g., relative velocity detection) becomes longer. If the time interval for observing the received phase changes when applying Fourier frequency analysis becomes longer, the maximum detectable Doppler frequency based on the sampling theorem decreases, and the detectable Doppler frequency range (e.g., relative velocity range) tends to narrow.

[0023] For example, as shown in Figure 1, we will explain a MIMO radar that uses time division multiplexing transmission to output transmission pulses while sequentially switching between transmitting antennas (e.g., Tx#1 and Tx#2) that emit chirp signals as transmitted radar waves at a transmission period Tr.

[0024] For example, in the case of Nt transmitting antennas (Nt=2 in Figure 1), the transmission time required for completing the transmission of radar transmission waves from the Nt transmitting antennas is Tr×Nt (2Tr in Figure 1). In a MIMO radar using time-division multiplexing transmission, if such time-division multiplexing transmission is repeated Nc times and Fourier frequency analysis is applied to Doppler frequency detection (e.g., relative velocity detection), the Doppler frequency range in which Doppler frequencies can be detected without aliasing is ±1 / (2Tr×Nt) according to the sampling theorem. Therefore, the Doppler frequency range in which Doppler frequencies can be detected without aliasing becomes narrower as the number of transmitting antennas Nt increases. Furthermore, in a MIMO radar using time-division multiplexing transmission, when a Doppler frequency is received that exceeds the range in which Doppler frequencies can be detected without aliasing, it is difficult to uniquely determine the Doppler frequency (e.g., relative velocity), and ambiguity is likely to occur.

[0025] In polarized radar using time division multiplexing, as in the MIMO radar using time division multiplexing described above, the Doppler frequency range in which Doppler frequencies can be detected without aliasing tends to narrow as the number of transmitting antennas Nt increases.

[0026] An example of time division multiplexing transmission has been described above.

[0027] Next, as an example, attention will be focused on a method of simultaneously multiplexing and transmitting transmission signals from a plurality of transmission antennas.

[0028] [About Doppler multiplex transmission] As a method for simultaneously multiplexing and transmitting transmission signals from multiple transmission antennas, there is, for example, a method for transmitting signals so that the multiple transmission signals can be separated in the Doppler frequency domain at the receiving unit (hereinafter referred to as "Doppler Division Multiplexing (DDM) transmission") (see, for example, Patent Document 5).

[0029] In Doppler multiplex transmission, the transmitter applies a phase rotation that gives a different Doppler shift to the transmission signal for each transmission antenna, and the transmission signals are simultaneously transmitted from the multiple transmission antennas. In Doppler multiplex transmission, signals received using the multiple receiving antennas (waves reflected from targets) are filtered in the Doppler frequency domain, so that the transmission signals transmitted from each transmission antenna are separated and received.

[0030] In a MIMO radar using Doppler multiplexing, for example, a specified Doppler frequency range (or Doppler shift amount) is assigned in advance to each of a plurality of transmitting antennas. For example, a polarized MIMO radar using Doppler multiplexing receives reflections from a target for each of the Doppler frequency ranges assigned to a plurality of transmitting antennas of different polarizations, thereby separating and receiving reflected waves from the target corresponding to the transmission signals for each of the transmitting antennas of different polarizations.

[0031] In MIMO radar using Doppler multiplexing, by simultaneously transmitting transmission signals from multiple transmitting antennas, the time interval for observing received phase changes when applying Fourier frequency analysis for Doppler frequency detection (e.g., relative velocity detection) can be shortened compared to time division multiplexing. On the other hand, in MIMO radar using Doppler multiplexing, the transmission signals of each transmitting antenna are separated by filtering on the Doppler frequency axis, which limits the effective Doppler frequency bandwidth per transmission signal.

[0032] For example, as shown in FIG. 2(a), we will explain a MIMO radar that uses Doppler multiplexing transmission, in which a chirp signal is output as a transmitted radar wave with a transmission period Tr, and is repeated Nc times, and Fourier frequency analysis is applied to detect the Doppler frequency (e.g., detect relative velocity).

[0033] For example, in Figure 2(b), the Doppler frequency range on the Doppler frequency axis in which Doppler frequency can be detected without aliasing is ±1 / (2Tr) according to the sampling theorem, which is expanded by Nt times (Nt=2 in Figure 2) compared to when time division multiplexing transmission is performed. On the other hand, in MIMO radar using Doppler multiplexing transmission, transmitted signals are separated by filtering on the Doppler frequency axis, so the effective Doppler frequency range per transmitted signal is narrower than the Doppler frequency range ±1 / (2Tr). For example, if Doppler shifts (hereinafter also referred to as "Doppler shift amounts" or "transmission Doppler shift amounts") of 0 [Hz] and -1 / (2Tr) [Hz] that divide the Doppler frequency range ±1 / (2Tr) into Nt equal parts (Nt=2 in the case of FIG. 2) are assigned to Tx#1 and Tx#2, respectively, a MIMO radar using Doppler multiplexing transmission multiplies the chirp signal (cp(t)), which is the transmission signal, by phase rotations Φ1(n)=(n-1)ΔΦ1 and Φ2(n)=(n-1)ΔΦ2 (where ΔΦ1=0 and ΔΦ2=π), for each transmission period Tr. Here, n=1, 2, 3, 4, ..., and is an index representing the number of times the chirp signal is transmitted.

[0034] In this case, as shown in (b) of Fig. 2, a Doppler frequency range is assigned in advance to each of the multiple transmitting antennas Tx#1 and Tx#2. For example, -1 / (4Tr)≦fd1<1 / (4Tr) is assigned to the range of Doppler frequency fd1 of Tx#1 (also referred to as the "Doppler division range"), and -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<-1 / (2Tr) are assigned to the range of Doppler frequency fd2 of Tx#2.

[0035] A MIMO radar using Doppler multiplexing receives, for example, signals transmitted from each transmitting antenna that are reflected by a target and then filters them on the Doppler frequency axis to separate and receive the transmitted signals. For example, in FIG. 2(b), a MIMO radar using Doppler multiplexing receives signals transmitted from transmitting antenna Tx#1 that are reflected by a target by filtering the range of -1 / (4Tr)≦fd1<1 / (4Tr) on the Doppler frequency axis to extract the signals. Similarly, a MIMO radar using Doppler multiplexing receives signals transmitted from transmitting antenna Tx#2 that are reflected by a target by filtering the ranges of -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<-1 / (2Tr) on the Doppler frequency axis to extract the signals.

[0036] In this way, in a MIMO radar using Doppler multiplexing, the reflected wave signals corresponding to the transmitted signals from each transmitting antenna are received and processed assuming that they fall within the Doppler frequency range of ±1 / (2Tr×Nt), resulting in a Doppler frequency range similar to that in the case of time division multiplexing. For example, in a MIMO radar using Doppler multiplexing, the Doppler frequency range in which Doppler frequencies can be detected without aliasing tends to narrow as the number of transmitting antennas Nt increases.

[0037] Furthermore, in a polarized MIMO radar using Doppler multiplexing, as in the MIMO radar using Doppler multiplexing described above, the Doppler frequency range in which Doppler frequencies can be detected without aliasing tends to narrow as the number of transmitting antennas Nt increases.

[0038] [About non-uniform Doppler multiplexing] The above-mentioned time division multiplexing transmission or Doppler multiplexing transmission can separate reflected waves corresponding to transmitted signals from multiple transmitting antennas using the allocated transmission time or Doppler frequency range. On the other hand, in time division multiplexing transmission and Doppler multiplexing transmission, the Doppler frequency detection range tends to narrow as the number of transmitting antennas increases. For example, in time division multiplexing and Doppler multiplexing, the detectable Doppler frequency range is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr), and the Doppler frequency detection range narrows in inverse proportion to the number of transmitting antennas. Here, Nt is the number of transmitting antennas.

[0039] For example, Patent Documents 6 and 7 disclose methods for expanding the detection range of Doppler frequencies in Doppler multiplex transmission. Patent Document 7 (for example, FIG. 4) discloses the following method: For example, the Doppler frequency range ±1 / (2Tr), in which Doppler frequencies can be detected without aliasing, is equally divided into (Nt+1) Doppler shift amounts (or Doppler frequency ranges), and Nt Doppler shift amounts are assigned to Nt transmission signals, and the transmission signals are simultaneously transmitted from Nt transmission antennas.

[0040] In this type of Doppler multiplexing, some of the (Nt+1) equally divided Doppler shift amounts are not assigned to the transmission signals. As a result, in the Doppler frequency domain, the intervals between the Doppler shift amounts assigned to the Doppler-multiplexed transmission signals (hereinafter also referred to as "Doppler multiplexing intervals") are unequal. Hereinafter, this type of Doppler multiplexing will be referred to as "unequal interval Doppler multiplexing (unequal interval DDM)."

[0041] FIG. 3 shows an example of allocation of Doppler multiplexed signals using unequal interval Doppler multiplexed transmission when radar transmission waves (e.g., chirp signals) are sent out every transmission period Tr, using Nt=2 transmitting antennas and setting the unit of Doppler multiplexing interval to Δfd=1 / (3Tr).

[0042] In FIG. 3, the transmission Doppler shift amounts assigned to transmitting antennas Tx#1 and Tx#2 are Δfd1=0 and Δfd2=1 / (3Tr) [Hz], respectively. For example, to impart a transmission Doppler shift amount Δfd1 to transmitting antenna Tx#1 every n-th transmission period, a phase rotation Φ1(n)=ΔΦ1×(n-1) is imparted to the radar transmission wave (chirp signal). Similarly, to impart a transmission Doppler shift amount Δfd2 to transmitting antenna Tx#2 every n-th transmission period, a phase rotation Φ2(n)=ΔΦ2×(n-1) is imparted to the radar transmission wave (chirp signal). Note that no transmitting antenna is assigned to the Doppler shift amount Δfd3 corresponding to the phase rotation Φ3(n)=ΔΦ3×(n-1).

[0043] Here, Fig. 3 shows the transmission Doppler frequencies assigned to transmitting antennas Tx#1 and Tx#2 when Δfd1=0, Δfd2=1 / (3Tr), ΔΦ1=0, and ΔΦ2=2π×Δfd×Tr=2π / 3. In Fig. 3, the transmission Doppler frequency when Δfd3=2 / (3Tr) and ΔΦ3=2π×2Δfd×Tr=4π / 3 (or -2π / 3) is represented by an "x" mark. As shown in Fig. 3, there is no assignment of a transmitting antenna to the Doppler shift amount Δfd3.

[0044] In addition, the phase rotation Φ n is -π≦ΔΦ n <π. For example, it can be written as ΔΦ3 = -2π / 3. The same applies below.

[0045] For example, as shown in Figure 3, consider the case where the Doppler multiplex interval for Tx#1 and Tx#2 is Δfd=1 / (3Tr), the observable Doppler frequency range (area) is -1 / (2Tr)≦fd<1 / Tr, and Doppler frequencies outside this range are included. For example, if the received Doppler frequency of the Doppler multiplexed signal of Tx#1 or Tx#2 exceeds 1 / (2Tr) or is smaller than -1 / (2Tr), as shown in Figure 3, the Doppler multiplex interval for Tx#1 and Tx#2 is Δf alias= 1 / Tr - Δfd = 2 / 3Tr. Hereinafter, when we refer to "Doppler multiple interval" or "Doppler shift interval", we will include Δf in addition to Δfd. alias Includes.

[0046] Next, an example of the demultiplexing and receiving process of Doppler multiplexed signals when non-uniform Doppler multiplexing transmission is used will be described.

[0047] In the process of separating and receiving Doppler multiplexed signals when using non-uniform Doppler multiplexed transmission, the following properties are utilized, for example, to detect the Doppler frequency of the received signal of the radar reflected wave (for example, to detect the relative velocity).

[0048] For example, in the output to which Fourier frequency analysis is applied, of the Doppler shift amounts divided equally into Nt+1, the received power level of the Doppler frequency corresponding to the Doppler shift amount to which the transmission signal is not assigned is sufficiently lower (for example, sufficiently lower than the noise level) than the received power level of the Doppler frequency corresponding to the Doppler shift amount to which the transmission signal is assigned.

[0049] MIMO radars that use non-uniform Doppler multiplexing utilize this property to estimate the received Doppler frequency of the waves reflected from the target and to separate the transmitting antennas.

[0050] For example, the Doppler frequency of the reflected wave from the target is expressed as "fd target In this case, the output of the radar reflected wave reception signal after applying Fourier frequency analysis for Doppler frequency detection (for example, relative velocity detection) is fd target +Δfd1 and fd target The received level of the Doppler frequency where +Δfd2 is observed to be high (for example, above the threshold). On the other hand, in the output where Fourier frequency analysis is applied for Doppler frequency detection (for example, relative velocity detection), fd target The reception level of the Doppler frequency that becomes +Δfd3 is fd target +Δfd1 and fd targetCompared with the reception level of the Doppler frequency +Δfd2, it is observed to be sufficiently low, about the noise level.

[0051] Note that the output to which Fourier frequency analysis is applied for Doppler frequency detection (e.g., relative velocity detection) is observed in the range of -1 / (2Tr)≦fd<1 / (2Tr). Therefore, if this range is exceeded, the output to which Fourier frequency analysis is applied is observed as a signal that is aliased in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0052] Received Doppler frequency fd of the reflected wave from the target target However, -1 / (2Tr)≦fd target < 1 / (2Tr), the received Doppler frequency that satisfies the above relationship is -1 / (2Tr)≦fd target < 1 / (2Tr), MIMO radar using non-uniform Doppler multiplexing can determine the target Doppler frequency fd without ambiguity within this range. target In a MIMO radar using non-uniform Doppler multiplexing, for example, the Doppler frequency fd corresponding to the target can be determined. target When the above equation is determined, the reception Doppler frequency for each transmitting antenna can be determined, and the Doppler multiplexed signals can be separated and received.

[0053] By performing this type of separation and reception processing of Doppler-multiplexed signals, a MIMO radar using non-uniform Doppler multiplexing can estimate the Doppler frequency of radar reflection waves, for example, in the Doppler frequency range of ±1 / (2Tr). Non-uniform Doppler multiplexing expands the detectable Doppler frequency range to ±1 / (2Tr). For example, non-uniform Doppler multiplexing expands the detectable Doppler frequency range by Nt times compared to the method of Patent Document 3.

[0054] [Application of Unequal Doppler Multiplexing to Polarimetric MIMO Radar] As described above, in uneven Doppler multiplexing, unlike, for example, equal-interval Doppler multiplexing, a portion of the Doppler frequency range is not allocated to the transmission signal, and the MIMO radar performs separation processing of the Doppler multiplexed signal to estimate the Doppler frequency of the target based on the received power of the received Doppler frequency of the wave reflected from the target.

[0055] For this reason, when applying non-uniform Doppler multiplexing to a polarized MIMO radar, the following can be expected.

[0056] In a polarized MIMO radar, for example, a phenomenon may occur in which the reception level of a reflected wave varies greatly depending on the polarization of the transmitting and receiving antennas. When transmitting antennas of different polarizations are used in a polarized MIMO radar, the reception level of a reflected wave from a transmitting antenna of one polarization may be significantly attenuated compared to the reception level of a reflected wave from a transmitting antenna of another polarization. Therefore, when multiplexing and transmitting using uneven Doppler multiplexing in a polarized MIMO radar, if there is a large difference in the reception levels of reflected waves between transmitting antennas of different polarizations, Doppler demultiplexing using uneven Doppler multiplexing may become difficult. When Doppler demultiplexing becomes difficult, the target detection performance of the MIMO radar may deteriorate, or Doppler demultiplexing may be erroneously performed, resulting in erroneous Doppler estimation or deterioration of angle measurement performance.

[0057] An example in which Doppler demultiplexing becomes difficult in a polarized MIMO radar that uses non-uniform Doppler multiplexing will be described below.

[0058] Here, as an example, a case will be described in which a MIMO radar is configured using two transmitting antennas for each of left-handed circular polarization (hereinafter also referred to as "LC") and right-handed circular polarization (hereinafter also referred to as "RC") (represented as LC-2Tx and RC-2Tx, respectively) (for example, the number of transmitting antennas Nt=4). For example, a polarized antenna corresponding to left-handed circular polarization is called an "LC polarized antenna" (for example, an LC polarized transmitting antenna or an LC polarized receiving antenna), and a polarized antenna corresponding to right-handed circular polarization is called an "RC polarized antenna" (for example, an RC polarized transmitting antenna or an RC polarized receiving antenna).

[0059] For example, let us consider a case where a MIMO radar receives a single-reflected wave (a wave reflected once by an object) using an LC-polarized receiving antenna. In this case, the reflected wave signal corresponding to the transmission signal from the RC-polarized transmitting antenna (also referred to as a "received signal corresponding to the RC-polarized transmitting antenna") is a received signal as RC polarization, and when the received signal corresponding to the RC-polarized transmitting antenna is received by the LC-polarized receiving antenna, it is received as cross-polarized waves. Therefore, the reception level of the received signal corresponding to the RC-polarized transmitting antenna at the LC-polarized receiving antenna is lower (depending on the cross-polarization discrimination of the antenna, for example, by 10 dB or more) than the reception level of the reflected wave signal corresponding to the transmission signal from the LC-polarized transmitting antenna (also referred to as a "received signal corresponding to the LC-polarized transmitting antenna"). For example, depending on the reception quality (e.g., signal-to-noise ratio (SNR)), the reception level of the received signal corresponding to the RC-polarized transmitting antenna may be below the noise level, making it difficult to detect Doppler frequency peaks in the MIMO radar.

[0060] Fig. 4 is a diagram showing an example of signals that are Doppler-multiplexed and transmitted in a polarized MIMO radar. In Fig. 4, signals assigned to the LC polarized transmitting antennas are represented by "L," and signals assigned to the RC polarized transmitting antennas are represented by "R."

[0061] For example, when a Doppler multiplexed signal is assigned as shown in (a) of Figure 4, if an LC polarized receiving antenna receives a single reflected wave, the reception level of the reception signal (R) corresponding to the RC polarized transmitting antenna may be lower than the reception signal (L) corresponding to the LC polarized transmitting antenna, as shown in (b) of Figure 4.

[0062] Next, for example, a case will be described in which a MIMO radar receives a twice-reflected wave (a wave reflected twice by an object) using an LC-polarized receiving antenna. In this case, the received signal corresponding to the LC-polarized transmitting antenna is converted from an LC-polarized wave to an RC-polarized wave because of the twice-reflected wave. When received by the LC-polarized receiving antenna, the signal is received as a cross-polarized wave, so the level of the received signal corresponding to the LC-polarized transmitting antenna is lower than that of the received signal corresponding to the RC-polarized transmitting antenna (depending on the cross-polarization discrimination of the antenna, for example, the level is 10 dB or more lower). For example, depending on the reception quality (SNR), the received level of the received signal corresponding to the LC-polarized transmitting antenna may be below the noise level, making it difficult to detect Doppler frequency peaks in the MIMO radar.

[0063] For example, when a Doppler multiplexed signal is assigned as shown in (a) of Figure 4, if the LC polarized receiving antenna receives two reflected waves, the reception level of the received signal (L) corresponding to the LC polarized transmitting antenna may be lower than the reception signal (R) corresponding to the RC polarized transmitting antenna, as shown in (c) of Figure 4.

[0064] Here, when the number of reflections is unknown in advance, it is difficult for the MIMO radar to determine, for example, based on the reception levels shown in (b) or (c) of Figure 4, whether the reception level of the reception signal corresponding to the RC polarization transmitting antenna or the reception level of the reception signal corresponding to the LC polarization transmitting antenna has decreased. Furthermore, it is also difficult for the MIMO radar to determine, for example, based on the reception levels shown in (b) or (c) of Figure 4, which transmitting antenna used for unevenly spaced Doppler multiplexing transmission the detected Doppler frequency peak corresponds to. This makes it difficult for the MIMO radar to separate the Doppler multiplexed signals, and to determine the Doppler frequency fd of the reflected wave from the target (e.g., referred to as the "target reflected wave") within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0065] Similarly, when Doppler multiplexed signals are assigned as shown in (d) of FIG. 4, if the MIMO radar receives a single reflected wave using an LC polarized receiving antenna, the received signal (R) corresponding to the RC polarized transmitting antenna is RC polarized, as shown in (e) of FIG. 4, and therefore the received level will be lower (depending on the cross polarization discrimination of the antenna, for example, 10 dB or more lower) than the received signal (L) corresponding to the LC polarized transmitting antenna, which is LC polarized.

[0066] Furthermore, when the MIMO radar receives the twice-reflected waves using an LC-polarized receiving antenna, as shown in (f) of Figure 4, the received signal (L) corresponding to the LC-polarized transmitting antenna is RC-polarized, and therefore the received level is smaller (depending on the cross-polarization discrimination of the antenna, for example, 10 dB or more smaller) than the received signal (R) corresponding to the RC-polarized transmitting antenna, which is LC-polarized.

[0067] In (e) and (f) of Figure 4, the received signal with a reduced reception level may fall below the noise level depending on the reception quality (SNR), making it difficult for the MIMO radar to detect the Doppler frequency peak. Furthermore, it is difficult for the MIMO radar to determine whether the reception level of the transmission signal from the RC-polarized transmitting antenna or the LC-polarized transmitting antenna has decreased based on the reception level shown in (e) or (f) of Figure 4. This makes it difficult for the MIMO radar to separate the Doppler-multiplexed signals and determine the Doppler frequency fd of the target reflection wave within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0068] In this way, in uneven Doppler multiplexing, Doppler demultiplexing processing is performed on the assumption that the reception levels of each transmitting antenna are approximately the same and that the reception levels of the Doppler multiplexing intervals (marked with x) that are not Doppler multiplexed are sufficiently low, approximately the noise level, as shown in (a) of Figure 4. In polarized MIMO radar using uneven Doppler multiplexing, the assumptions for the demultiplexing processing of uneven Doppler multiplexing may not hold, as shown in (b), (c), (e), or (f) of Figure 4, which may result in an error in the Doppler demultiplexing processing.

[0069] In a non-limiting example embodiment of the present disclosure, a method for improving the detection performance of a polarimetric MIMO radar using non-uniform Doppler multiplexing transmission is described.

[0070] Here, an example has been described in which a MIMO radar is configured using two transmitting antennas for each of the left-handed circular polarization (LC) and right-handed circular polarization (RC) (for example, the number of transmitting antennas Nt=4), but the polarizations used in the polarized MIMO radar are not limited to these.

[0071] For example, in a polarized MIMO radar, different linear polarizations that are orthogonal to each other may be used. For example, vertical polarization may be used instead of left-handed circular polarization (LC) and horizontal polarization may be used instead of right-handed circular polarization (RC). When radar transmission waves are transmitted using such vertically and horizontally polarized transmitting antennas, the closer the incident angle of the radar transmission waves reflected by a target is to the Brewster angle, the weaker the reflected wave reception level of either the vertically polarized or horizontally polarized wave may be compared to the other polarized wave. In a MIMO radar, for example, when such reflected waves are received using a polarized receiving antenna corresponding to either vertical or horizontal polarization, the received signal corresponding to either the vertically polarized or horizontally polarized transmitting antenna will be received as a cross-polarized wave and may have a lower reception level (depending on the cross-polarization discrimination of the antenna, for example, 10 dB or more lower) compared to the received signal corresponding to the other polarized transmitting antenna. The received signal whose reception level drops may fall below the noise level depending on the reception quality (SNR), making it difficult to detect the Doppler frequency peak in the MIMO radar.

[0072] For example, when vertical polarization is applied instead of left-handed circular polarization (LC) and horizontal polarization is applied instead of right-handed circular polarization (RC), if a Doppler multiplexed signal is assigned as shown in (a) of Figure 4, the received signal may be as shown in (b) or (c) of Figure 4. Also, when vertical polarization is applied instead of left-handed circular polarization (LC) and horizontal polarization is applied instead of right-handed circular polarization (RC), if a Doppler multiplexed signal is assigned as shown in (d) of Figure 4, the received signal may be as shown in (e) or (f) of Figure 4.

[0073] Even when vertically polarized and horizontally polarized transmitting antennas are used, it is difficult for a MIMO radar to determine whether the reception level of a transmission signal from a horizontally polarized transmitting antenna or a vertically polarized transmitting antenna has decreased, based on the reception levels shown in, for example, (b), (c), (e), or (f) of Figure 4. This makes it difficult for the MIMO radar to separate Doppler multiplexed signals, and to determine the Doppler frequency fd of a target reflected wave within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0074] Hereinafter, an embodiment according to an example of the present disclosure will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and redundant descriptions thereof will be omitted.

[0075] The following describes a configuration (e.g., MIMO radar configuration) in which a radar device transmits different multiplexed transmission signals simultaneously from multiple transmission antennas in a transmission branch, and a reception branch separates the transmission signals and performs reception processing.

[0076] In the following, as an example, a configuration of a radar system using a frequency-modulated pulse wave such as a chirp pulse (also called fast chirp modulation) will be described. However, the modulation system is not limited to frequency modulation. For example, an embodiment of the present disclosure can also be applied to a radar system using a pulse compression radar that transmits a pulse train after phase modulation or amplitude modulation.

[0077] The radar device may perform, for example, Doppler multiplexing (for example, unevenly spaced Doppler multiplexing), and may include, for example, a polarized antenna.

[0078] [Radar device configuration] The radar device 10 in FIG. 5 includes a radar transmitter (transmitting branch) 100 and a radar receiver (receiving branch) 200.

[0079] The radar transmitter 100 generates a radar signal (radar transmission signal) and transmits the radar transmission signal at a specified transmission period (e.g., referred to as a "radar transmission period") using a transmission antenna unit 105 configured with multiple transmission antennas (e.g., Nt antennas).

[0080] The radar receiving unit 200 receives reflected wave signals, which are radar transmission signals reflected by a target (not shown), using a receiving antenna unit 202 including multiple receiving antennas. The radar receiving unit 200 processes the reflected wave signals received by each receiving antenna of the receiving antenna unit 202, and, for example, detects the presence or absence of a target or estimates the arrival distance, Doppler frequency (e.g., relative velocity), and arrival direction of the reflected wave signal, and outputs information related to the estimation result (e.g., positioning information).

[0081] The radar device 10 may be mounted on a moving body such as a vehicle, and the positioning output from the positioning output unit 300 (e.g., information on the estimation result) may be connected to a control device ECU (Electronic Control Unit) (not shown) such as an Advanced Driver Assistance System (ADAS) or an autonomous driving system that improves collision safety, and used for vehicle drive control or alarm call control.

[0082] The radar device 10 may be attached to a relatively high structure (not shown), such as a roadside utility pole or a traffic light. The radar device 10 may be used, for example, as a sensor in an assistance system for improving the safety of passing vehicles or pedestrians or in a system for preventing the intrusion of suspicious individuals (not shown). The positioning output of the radar receiving unit 200 may be connected to a control device (not shown) in the assistance system for improving safety or in the system for preventing the intrusion of suspicious individuals, and used for alarm generation control or abnormality detection control. The uses of the radar device 10 are not limited to these, and the radar device 10 may be used for other purposes.

[0083] Furthermore, a target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including two-wheeled and four-wheeled vehicles), a person, a block, or a curb.

[0084] [Configuration of radar transmitter 100] The radar transmitter 100 includes a radar transmission signal generator 101 , a Doppler shifter 104 , and a transmission antenna 105 .

[0085] The radar transmission signal generation unit 101 generates a radar transmission signal. The radar transmission signal generation unit 101 includes, for example, a modulation signal generation unit 102 and a VCO (Voltage Controlled Oscillator) 103. Each component of the radar transmission signal generation unit 101 will be described below.

[0086] The modulation signal generating section 102 periodically generates a modulation signal, for example, having a sawtooth shape.

[0087] Based on the modulation signal input from the modulation signal generating unit 102, the VCO 103 outputs a frequency modulation signal (hereinafter referred to as a frequency chirp signal or chirp signal, for example) to the Doppler shift unit 104 and the radar receiving unit 200 (mixer unit 204, described later) as a radar transmission signal (radar transmission wave) as shown in FIG. 6, for example.

[0088] In the following description, the modulated signal generator 102 generates a modulated signal so that the chirp signal is transmitted Nc times for each transmission period Tr for one radar positioning. The VCO 103 outputs the chirp signal Nc times for each transmission period Tr based on the operation of the modulated signal generator 102.

[0089] The radar device 10 may detect time fluctuations in the target position by, for example, performing radar positioning multiple times.

[0090] In the following description, each of the Nc transmission periods Tr is represented by an index "m," where m=1 to Nc.

[0091] FIG. 7 shows an example of a chirp signal output from the radar transmission signal generator 101.

[0092] As shown in FIG. 7, modulation parameters for a chirp signal include, for example, a center frequency f c , frequency sweep bandwidth B w , sweep start frequency f cstart , sweep end frequency f cend , frequency sweep time T sw , and frequency sweep rate of change D m may be included. m =B w / T sw Also, B w =f cend -f cstart and f c =(f cstart +f cend ) / 2.

[0093] Also, the frequency sweep time T sw corresponds to, for example, a time range (also called a range gate) for capturing A / D sample data in an AD conversion unit 207 of the radar receiver 200 (described later). sw For example, the time may be set to the entire interval of the chirp signal as shown in FIG. 7(a), or may be set to a partial interval of the chirp signal as shown in FIG. 7(b).

[0094] 6 and 7 show examples of up-chirp waveforms in which the modulation frequency gradually increases over time, but the present invention is not limited to this, and down-chirp waveforms in which the modulation frequency gradually decreases over time may also be used. Similar effects can be obtained regardless of whether the modulation frequency is up-chirp or down-chirp.

[0095] The chirp signals output from the radar transmission signal generation unit 101 are input to the Nt Doppler shift units 104. The chirp signals are also input to the mixer units 204 of the radar reception unit 200.

[0096] The n-th Doppler shifter 104 applies a prescribed Doppler shift amount DOP to the chirp signal input from the radar transmission signal generator 101, for example. n In order to give the chirp signal, the phase rotation Φ n (m). The n-th Doppler shifter 104 applies a phase rotation Φ n The chirp signal to which (m) is assigned is output to the n-th transmitting antenna (for example, Tx#n) of the transmitting antenna unit 105, where n=1 to Nt.

[0097] The transmitting antenna unit 105 may include Nt transmitting antennas Tx#1 to Tx#Nt. The transmitting antennas Tx#1 to Tx#Nt may include transmitting antennas of at least two different types of polarized waves (polarized transmitting antennas) and may form a polarized radar. For example, the Doppler shift unit 104 may apply a phase rotation Φ n (m) may be added to the chirp signal and output to the transmitting antenna unit 105. This enables the radar device 10 to separate the Doppler multiplexed signals even when there is a large difference in reception levels between reception signals corresponding to transmitting antennas of different polarizations (for example, when the difference in reception levels is equal to or greater than a threshold), thereby reducing degradation of positioning performance and radar detection performance (an example of operation will be described later).

[0098] The outputs from the Nt Doppler shift units 104 are amplified to a specified transmission power, and then radiated into space from the respective transmission antennas Tx#1 to Tx#Nt of the transmission antenna unit 105.

[0099] [Configuration of radar receiver 200] 5, the radar receiver 200 includes a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. The radar receiver 200 also includes Na antenna system processors 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 210, a Doppler demultiplexing unit 211, and a direction estimating unit 212.

[0100] The receiving antennas Rx#1 to RxNa of the receiving antenna unit 202 receive reflected wave signals, which are radar transmission signals reflected by targets, and output the received reflected wave signals to the corresponding antenna system processing units 201 as received signals.

[0101] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206 .

[0102] The signals received at the Na receiving antennas Rx#1 to Rx#Na are output to Na receiving radio units 203, respectively. The output signals from the Na receiving radio units 203 are output to Na signal processing units 206, respectively.

[0103] The radio reception unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with a chirp signal, which is a transmission signal, input from the radar transmission signal generation unit 101. The radio reception unit 203, for example, passes the output of the mixer unit 204 through the LPF 205. This outputs a beat signal whose frequency corresponds to the delay time of the reflected wave signal. For example, as shown in FIG. 8, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulated wave), which is the transmission signal (radar transmission wave), and the frequency of the reception chirp signal (reception frequency modulated wave), which is the reception signal (radar reflected wave), is obtained as the beat frequency.

[0104] The signal processing unit 206 of each antenna system processing unit 201-z (where z=1 to Na) has an AD conversion unit 207, a beat frequency analysis unit 208, and a Doppler analysis unit 209.

[0105] The signal (for example, a beat signal) output from the LPF 205 is converted into discrete sample data by the AD conversion unit 207 in the signal processing unit 206, which is discretely sampled.

[0106] The beat frequency analysis unit 208 analyzes N data The discrete sample data is subjected to frequency analysis processing (for example, FFT processing). As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at a beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). During the FFT processing, the beat frequency analysis unit 208 may multiply the signal by a window function coefficient such as a Han window or a Hamming window. By using the window function coefficient, it is possible to suppress side lobes that occur around the beat frequency peak.

[0107] In addition, N data If N is not a power of 2, for example, by including zero-padded data, FFT processing can be performed with a data size (FFT size) that is a power of 2. In such a case, the data size including the zero-padded data is N data It can be treated in the same way as above by regarding it as

[0108] Here, the beat frequency response output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 obtained by transmitting the m-th chirp pulse is referred to as "RFT z (f b , m) where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,~,(N data / 2)-1, z = 1~Na, m = 1~N C The beat frequency index f b The smaller the beat frequency, the shorter the delay time of the reflected wave signal (for example, the closer the distance to the target).

[0109] Also, the beat frequency index f b is calculated by the following equation (1): b ) can be transformed into the beat frequency index f b Let "distance index f b " is called.

number

[0110] where B w represents the frequency modulation bandwidth within the range gate of the chirp signal, and C0 represents the speed of light. Also, in equation (1), C0 / (2B w ) represents the distance resolution.

[0111] The Doppler analysis unit 209 in the z-th signal processing unit 206 calculates the chirp signal by dividing the data of Nc transmission periods (for example, the beat frequency response RFT input from the beat frequency analysis unit 208). z (f b , 1), RFT z (f b , 2), ~, RFT z (f b , Nc)) to obtain the distance index f b Doppler analysis is performed every time.

[0112] For example, when Nc is a power of 2, the Doppler analysis unit 209 can apply FFT processing in the Doppler analysis as shown in the following equation (2).

number

[0113] Here, the FFT size is Nc, and the maximum Doppler frequency at which aliasing does not occur, as derived from the sampling theorem, is ±1 / (2Tr). Also, the Doppler frequency index f s The Doppler frequency interval is 1 / (Nc×Tr), and the Doppler frequency index f s The range of f s= -Nc / 2, ~, 0, ~, (Nc / 2)-1. Also, j is the imaginary unit, and z=1~Na.

[0114] In the following, as an example, a case where Nc is a power of 2 will be described. If Nc is not a power of 2, for example, by including zero-padded data, FFT processing can be performed with a data size (FFT size) that is a power of 2. Furthermore, the Doppler analysis unit 209 may multiply by a window function coefficient such as a Han window or a Hamming window during FFT processing. Applying a window function can suppress side lobes that occur around the Doppler frequency peak.

[0115] The processing in each component of the signal processing unit 206 has been described above.

[0116] 5, the CFAR unit 210 performs CFAR processing (for example, adaptive threshold determination) using the outputs of the Doppler analysis units 209 of the first to Na-th signal processing units 206. For example, in the CFAR processing, local peaks of the reflected wave reception signal of the radar transmission signal sent from the transmitting antenna unit 105 may be selectively extracted, and adaptive threshold determination may be performed. The CFAR unit 210 may select, for example, a distance index f that gives a local peak signal. b_cfar and the Doppler frequency index f s_cfar and outputs it to the Doppler demultiplexing unit 211.

[0117] The Doppler demultiplexing unit 211 separates the radar reflected wave reception signals for each radar transmission signal sent from the multiple transmission antennas using Doppler multiplexing, for example, using the outputs of the Doppler analysis units 209 of the first to Nath signal processing units 206 and the output of the CFAR unit 210 (hereinafter referred to as "Doppler demultiplexing").

[0118] Note that the operation of the Doppler demultiplexing unit 211 is related to, for example, the operation of the Doppler shifting unit 104 of the radar transmitting unit 100. Similarly, the operation of the CFAR unit 210 is related to, for example, the operation of the Doppler shifting unit 104. Below, an example of the operation of the Doppler shifting unit 104 will be described, and then an example of the operation of the CFAR unit 210 and an example of the operation of the Doppler demultiplexing unit 211 will be described.

[0119] [Example of Operation of Doppler Shift Unit 104 in Radar Transmitter 100] The first to Nt-th Doppler shift units 104 apply different Doppler shift amounts DOP to the radar transmission signals input thereto, for example. n is added to perform Doppler multiplexing.

[0120] In the following, an example will be described in which a chirp signal is used as the radar transmission signal.

[0121] For example, the n-th Doppler shift unit 104 sets a prescribed Doppler shift amount DOP for the n-th transmitting antenna Tx#n. n In order to give the chirp signal, the phase rotation Φ n Here, the Doppler shifter 104 applies a phase rotation Φ (m) to the chirp signal, which is different for each transmitting antenna from which the chirp signal is transmitted. n (m) may be added to the chirp signal and output, where n=1 to Nt. For example, the phase rotation Φ n (m) is Φ n (m)=2πDOP n ×Tr.

[0122] For example, the transmitting antennas Tx#1 to Tx#Nt of the transmitting antenna unit 105 may include transmitting antennas of at least two different types of polarization, constituting a polarized radar. For example, the transmitting antennas Tx#1 to Tx#Nt may include transmitting antennas of different polarizations that are orthogonal to each other. Furthermore, there may be multiple transmitting antennas of at least one polarization among the multiple polarizations, and at least one transmitting antenna of the other polarization.

[0123] The radar device 10 may be, for example, a polarized MIMO radar using Nt transmitting antennas Tx#1 to Tx#Nt including transmitting antennas of different polarizations. The radar device 10 may perform uneven Doppler multiplexing transmission using the Nt transmitting antennas Tx#1 to Tx#Nt.

[0124] Furthermore, the radar device 10 may simultaneously multiplex and transmit radar transmission signals from Nt transmitting antennas Tx#1 to Tx#Nt using Doppler multiplex transmission that satisfies the following conditions 1 and 2.

[0125] In the following description, of the multiple polarizations used in the polarized radar, the first polarization will be referred to as "PL1 polarization" and the second polarization will be referred to as "PL2 polarization." For example, the qth polarization will be referred to as "PLq polarization." For example, the PL1 polarization and the PL2 polarization may be combinations of different polarizations that form orthogonal polarizations, such as right-handed circular polarization and left-handed circular polarization, horizontal polarization and vertical polarization, or right-diagonal 45° polarization and left-diagonal 45° polarization.

[0126] In addition, the number of transmitting antennas is set to Nt≧3. For example, the number of Doppler multiplexing N DDM ≧3.

[0127] In addition, in the transmitting antenna unit 105, the number of transmitting antennas corresponding to the PL1 polarization (for example, referred to as "PL1 polarization transmitting antennas") is set to N PL1 Let the number of transmitting antennas corresponding to PL2 polarization (e.g., called "PL2 polarization transmitting antennas") be N PL2 In this case, N PL1+N PL2 =Nt.

[0128] <Condition 1> PL1 polarized transmitting antenna with unequal interval Doppler multiplexing (N PL1 Considering the case of ≧2, N PL1 =1, no consideration required) PL2 polarized transmitting antenna with unequal interval Doppler multiplexing (N PL2 Considering the case of ≧2, N PL2 =1 does not require consideration) Doppler multiplexed signals are assigned to the PL1 polarization and the PL2 polarization, respectively, so that:

[0129] <Condition 2> Any one of the following conditions is satisfied between the Doppler multiplexed signals assigned to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna. (1) Including different Doppler shift intervals. (2) The number of Doppler multiplexing (= number of transmitting antennas) for each polarization is different (N PL1 ≠N PL2 ). (3)N PL1 ≧3, N PL2 In the case where ≧3, when the same Doppler shift interval is included in the Doppler shift intervals for each polarization, the order of the Doppler shift intervals is different.

[0130] For example, under condition 1, the intervals of the Doppler shift amounts assigned to the PL1 polarization transmitting antenna are set to be uneven on the Doppler frequency axis. Similarly, under condition 1, the intervals of the Doppler shift amounts assigned to the PL2 polarization transmitting antenna are set to be uneven on the Doppler frequency axis.

[0131] Furthermore, for example, in condition 2 (1), the intervals of the Doppler shift amounts (Doppler shift intervals or Doppler multiplexing intervals) assigned to the PL1 polarization transmitting antenna may include intervals different from the intervals of the Doppler shift amounts assigned to the PL2 polarization transmitting antenna. Examples of condition 2 (1) include a case where the maximum Doppler shift intervals are different between the Doppler multiplexed signals assigned to the PL1 polarization and the PL2 polarization, a case where the minimum Doppler shift intervals are different, or a case where the Doppler shift intervals are different but are neither maximum nor minimum.

[0132] As an example of condition 2 (2), there is a case where either the PL1 polarized wave transmitting antenna or the PL2 polarized wave transmitting antenna is one, resulting in a SIMO (Single-Input Multiple Output) radar configuration (N PL1 = 1 and N PL2 If ≧2, or N PL1 ≧2 and N PL2 = 1), and when there are two or more PL1 polarized transmitting antennas and two or more PL2 polarized transmitting antennas, each of which forms a MIMO radar configuration (N PL1 ≧2 and N PL2 ≧2).

[0133] Furthermore, for example, in condition 2 (3), the values ​​of each interval of the Doppler shift amount assigned to the PL1 polarized transmitting antenna and the PL2 polarized transmitting antenna (for example, the combination of Doppler shift intervals) are the same, and within the Doppler frequency range, the order of each interval of the Doppler shift amount assigned to the PL1 polarized transmitting antenna is different from the order of each interval of the Doppler shift amount assigned to the PL2 polarized transmitting antenna.

[0134] For example, the combination of intervals included in an array (e.g., a first array) in which the intervals of the Doppler shift amounts assigned to the PL1 polarized transmitting antenna are arranged in ascending order on the Doppler frequency axis matches the combination of intervals included in an array (e.g., a second array) in which the intervals of the Doppler shift amounts assigned to the PL2 polarized transmitting antenna are arranged in ascending order on the Doppler frequency axis, and the first array and the second array are different arrays in terms of circular permutation.

[0135] When Condition 2 (3) is satisfied, the Doppler shift interval of the PL1 polarized antenna and the Doppler shift interval of the PL2 polarized antenna do not match even if one of them is cyclically shifted in the Doppler frequency domain.

[0136] Thus, in the unevenly spaced Doppler multiplexed transmission by the radar device 10, which is a polarized radar, the intervals between the Doppler shift amounts assigned to the multiple transmitting antennas included in the transmitting antenna unit 105 are uneven in the Doppler frequency range of the target of Doppler analysis. Furthermore, for example, the intervals between the Doppler shift amounts assigned to the transmitting antennas corresponding to the multiple polarized waves among the multiple transmitting antennas included in the transmitting antenna unit 105 are uneven (Condition 1). Furthermore, for example, in the Doppler frequency range of the target of Doppler analysis, the patterns of the Doppler shift amounts assigned between the PL1 polarized transmitting antenna and the PL2 polarized transmitting antenna are different (Condition 2). For example,

[0137] As a result, even if the received power levels of reflected waves differ significantly between received signals from transmitting antennas of different polarizations, the radar device 10 can separate Doppler multiplexed signals, thereby suppressing deterioration of positioning performance and radar detection performance.

[0138] Since the Doppler analyzer 209 performs Doppler frequency analysis on the output of the beat frequency analyzer 208 for each distance index at the transmission period Tr, the Doppler frequency f d The range is -1 / (2Tr) ≦fd <1 / (2Tr), and even if the Doppler frequency exceeds this range, the range of the observed Doppler frequency fd is −1 / (2Tr)≦fd<1 / (2Tr).

[0139] For example, if the Doppler shift unit 104 is −1 / (2Tr)≦fd When adding a Doppler shift amount within the range of <1 / (2Tr), the maximum Doppler shift interval for Nt transmitting antennas (=Doppler multiplexing number) is Δfdmax=1 / (TrNt)=1 / (TrN DM ) The Doppler shift unit 104 may set the Doppler shift interval to an interval smaller than Δfdmax, for example. The phase rotation φ that gives such a Doppler shift amount can be set within the range of -π≦φ<π, for example.

[0140] In the following description of the operation of the Doppler shifter 104, when a phase rotation φ0 exceeding the range of -π≦φ<π is applied, a phase rotation φ0+2πα that is in phase within the range of -π to π may be applied, where α is an integer value that satisfies -π≦φ0+2πα<π.

[0141] Furthermore, the Doppler multiplexing interval given to the Doppler multiplexed signal set by the Doppler shift unit 104 may be set in units of, for example, Δfd shown in the following equation (3). Here, δ>0, and δ may be a positive integer or a positive real number. By setting δ to a positive integer, it is possible to obtain the effect of simplifying the processing in the CFAR unit 210, which will be described later. Note that, although the case where δ is a positive integer is shown below, the present invention is not limited to this and a positive real number may also be used.

number

[0142] Furthermore, in equation (3), when δ is a positive integer such that δ>1, there are multiple Doppler shift amounts to which a Doppler multiplexed signal cannot be assigned (for example, Doppler shift amounts indicated by "x" marks in the diagrams used in the following examples of setting the Doppler shift amounts). In this case, for example, by assigning Doppler multiplexed signals whose Doppler shift amounts are not equally spaced, the Doppler frequency range fd that can be detected by the radar device 10 can be set to the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0143] An example of setting the amount of Doppler shift in the Doppler shifter 104 will be described below.

[0144] <Doppler shift amount setting example 1> Figure 9 shows the number of transmit antennas, Nt=3, N PL1 =2, N PL2 9 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .gtoreq.1. In FIG. 9, Tx#1 and Tx#2 are PL1 polarized wave transmission antennas, and Tx#3 is a PL2 polarized wave transmission antenna.

[0145] In the first example of setting the amount of Doppler shift, as shown in FIG. 9, the basic unit of the Doppler shift interval in the Doppler shifter 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (4Tr) and δ=1, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0146] In the example shown in FIG. 9, the first to third Doppler shift sections 104 (or the Doppler shift sections 104-1, 104-2, and 104-3) may perform the following operations.

[0147] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=2πDOP1×Tr=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0148] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=2πDOP2×Tr=-π(m-1) / 2 for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP2=-1 / (4Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0149] The third Doppler shift unit 104 imparts a phase rotation Φ3(m)=2πDOP3×Tr=0 to the third transmitting antenna Tx#3, for example, and outputs the phase rotation Φ3(m)=2πDOP3×Tr=0 for each transmission period Tr of the chirp signal.

[0150] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0151] In FIG. 9, the pattern of the intervals of the Doppler shift amounts (Doppler multiplex intervals) given to the respective transmitting antennas Tx#1, Tx#2, and Tx#3 is Δfd (1, 2) =Δfd, Δfd (2, 3) =Δfd, Δfd (3,1) Therefore, in FIG. 9, the intervals of the Doppler shift amounts given to the three transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (1, 2) =Δfd (2, 3) ≠Δfd (3,1) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0152] In addition, in FIG. 9, the Doppler shift interval between the transmitting antennas Tx#1 and Tx#2, which are PL1 polarized waves, is Δfd (1, 2) =Δfd, Δfd (2, 1) = 3Δfd. Therefore, the number of PL1 polarized antennas N PL1 The intervals of the Doppler shifts given to each of the PL1 polarization antennas of =2 are not all the same, but include unequal intervals (Δfd (1, 2) ≠Δfd (2, 1) ), and unevenly spaced Doppler multiplexing transmission (unevenly spaced DDM transmission) using a PL1 polarized antenna.

[0153] In addition, in FIG. 9, the number of transmitting antennas Tx#3 that are PL2 polarized waves is N PL2 = 1, the SIMO radar configuration is with a PL2 polarized antenna, and the case does not result in Doppler multiplex transmission, so there is no need to consider it.

[0154] From the above, the example shown in FIG. 9 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 1.

[0155] Also, in FIG. 9, N PL1 (=2)≠N PL2 (=1) For example, in the example shown in Fig. 9, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0156] Therefore, the example shown in FIG. 9 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2(2).

[0157] For example, Figure 10 shows an example of the received signal at the output of the Doppler analysis unit 209 when a transmitting antenna unit 105 is used in which the PL1 polarization is left-handed circular polarization (LC) and the PL2 polarization is right-handed circular polarization (RC) according to the Doppler shift amount settings shown in Figure 9, and an LC polarization (PL1 polarization) antenna is used for the receiving antenna unit 202.

[0158] FIG. 10 shows the output of the Doppler analysis unit 209 for a target reflected wave at a certain distance index. For example, the target reflected wave has fd target 10, the radar device 10 calculates the Doppler frequency fd from the Doppler shift amount shown in FIG. target A signal subjected to a minute Doppler shift is received.

[0159] Here, when the reflected wave of the radar transmission wave reflected by the target includes a large number of scattered waves or a large number of reflections, the reflected wave may include a variety of polarized waves. Therefore, the difference in reception level between the received signals corresponding to different polarized wave transmitting antennas (e.g., PL1 polarized wave transmitting antenna and PL2 polarized wave transmitting antenna) at the radar device 10 is unlikely to be large. Therefore, the radar device 10 receives the received signal corresponding to the RC polarized wave (PL2 polarized wave) transmitting antenna and the received signal corresponding to the LC polarized wave (PL1 polarized wave) transmitting antenna at approximately the same reception level.

[0160] For example, when the Doppler shift amount is set as shown in Fig. 9, if the target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)) is not included, a received signal like that shown in Fig. 10(a) is obtained. As shown in Fig. 10(a), the reception levels of the received signals corresponding to the transmitting antennas Tx#1 (PL1 polarization), Tx#2 (PL1 polarization), and Tx#3 (PL2 polarization) are approximately the same.

[0161] Furthermore, for example, when the radar device 10 receives a reflected wave that is specularly reflected by a target (e.g., a smooth surface) from a radar transmission wave (e.g., a single specular reflection), the reception level may differ between polarized transmitting antennas. For example, a received signal corresponding to an LC polarization (PL1 polarization) transmitting antenna is a signal of the same polarization as that of an LC polarization (PL1 polarization) receiving antenna. On the other hand, a received signal corresponding to an RC polarization (PL2 polarization) transmitting antenna is a signal of cross-polarization with that of an LC polarization (PL1 polarization) receiving antenna. Therefore, the received signal corresponding to an RC polarization (PL2 polarization) transmitting antenna may have a lower reception level (depending on the cross-polarization discrimination of the antenna, for example, a reception level that is 10 dB or more lower) than that of a received signal corresponding to an LC polarization (PL1 polarization) transmitting antenna. For example, depending on the reception SNR, the received signal corresponding to an RC polarization (PL2 polarization) transmitting antenna may be below the noise level, making it difficult for the radar device 10 to detect the Doppler frequency peak.

[0162] For example, in the case of the Doppler shift amount setting shown in Fig. 9, if a target reflected wave is included in which the RC polarization (PL2 polarization) is cross-polarized with respect to the polarization of the receiving antenna (for example, the LC polarization (PL1 polarization)), a received signal like that shown in Fig. 10(b) is obtained. As shown in Fig. 10(b), the reception level of the received signal corresponding to transmitting antenna Tx#3 (PL2 polarization) is smaller than the reception levels of the received signals corresponding to transmitting antennas Tx#1 and Tx#2 (PL1 polarization).

[0163] Furthermore, for example, when the radar device 10 receives a reflected wave that is specularly reflected by a target and then specularly reflected by a road surface or the like (e.g., two specular reflections), the reception level may differ between the polarized transmitting antennas. For example, a received signal corresponding to an RC-polarized (PL2) transmitting antenna will be a signal of the same polarization as that of an LC-polarized (PL1) receiving antenna. On the other hand, a received signal corresponding to an LC-polarized (PL1) transmitting antenna will be a signal of cross-polarization with that of an LC-polarized (PL1) receiving antenna. Therefore, the received signal corresponding to an LC-polarized (PL1) transmitting antenna may have a lower reception level (depending on the cross-polarization discrimination of the antenna, for example, 10 dB or more lower) than that of a received signal corresponding to an RC-polarized (PL2) transmitting antenna. For example, depending on the reception SNR, the received signal from the LC-polarized (PL1) transmitting antenna may be below the noise level, making it difficult for the radar device 10 to detect the Doppler frequency peak.

[0164] For example, when the Doppler shift amount is set as shown in Fig. 9, if a target reflected wave is included in which the LC polarization (PL1 polarization) is cross-polarized with respect to the polarization of the receiving antenna (for example, the LC polarization (PL1 polarization)), a received signal such as that shown in Fig. 10(c) is obtained. As shown in Fig. 10(c), the reception levels of the received signals corresponding to the transmitting antennas Tx#1 and Tx#2 (PL1 polarization) are smaller than the reception level of the received signal corresponding to the transmitting antenna Tx#3 (PL2 polarization).

[0165] For example, as shown in (a) of Figure 10, when no target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas are included, the radar device 10 receives signals corresponding to the RC polarization (PL2 polarization) transmitting antenna (Tx#3) and the LC polarization (PL1 polarization) transmitting antennas (Tx#1 and Tx#2) at approximately the same level. Here, in (a) of Figure 10, signals transmitted from Nt transmitting antennas Tx#1, Tx#2, and Tx#3, each consisting of an RC polarization (PL2 polarization) transmitting antenna and an LC polarization (PL1 polarization) transmitting antenna, are Doppler-multiplexed and transmitted using Doppler shift intervals resulting in uneven Doppler multiplexing. Therefore, the radar device 10 can demultiplex a Doppler-multiplexed signal based on the existing demultiplexing operation of a Doppler-multiplexed signal.

[0166] 10(b) and 10(c), when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (e.g., Doppler multiplexed signals that satisfy condition 2-(2)) when the PL2 polarization includes a target reflected wave that is cross-polarized (FIG. 10(b)) and when the PL1 polarization includes a target reflected wave that is cross-polarized (FIG. 10(c)). For example, in FIG. 10(b), the radar device 10 receives a Doppler multiplexed signal that satisfies condition 2-(2) when the Doppler shift interval Δfd (1, 2) or Δfd (2, 1) In FIG. 10(c), a signal with one Doppler frequency component is received.

[0167] In this way, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0168] This enables the radar device 10 to determine, for example, based on the detected Doppler frequency peaks (e.g., the number of peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization (LC polarization) transmitting antenna has occurred or whether a decrease in the reception level of the reception signal corresponding to the PL2 polarization (RC polarization) transmitting antenna has occurred in the Doppler multiplexing separation unit 211 described later.

[0169] For example, the Doppler multiplexed signal of LC polarization (PL1 polarization) is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal is a received signal corresponding to an LC polarization (PL1 polarization) transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0170] In addition, the RC polarized wave (PL2 polarized wave) transmitting antenna is a single antenna transmitting antenna. Therefore, for example, when the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the RC polarized wave (PL2 polarized wave) transmitting antenna, the radar device 10 does not need to perform Doppler multiplexing signal separation processing on the RC polarized wave received signal.

[0171] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), and obtain an output that corresponds to a transmitting antenna for each Doppler multiplexed signal.

[0172] <Doppler shift amount setting example 2> Figure 11 shows the number of transmit antennas, Nt=4, N PL1 =2, N PL2 11 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .gtoreq.2. In FIG. 11, Tx#1 and Tx#2 are PL1 polarized wave transmission antennas, and Tx#3 and Tx#4 are PL2 polarized wave transmission antennas.

[0173] In the second example of setting the amount of Doppler shift, as shown in FIG. 11, the basic unit of the Doppler shift interval in the Doppler shifter 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (5Tr) and δ=1, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0174] In the example shown in FIG. 11, the first to fourth Doppler shift sections 104 (or the Doppler shift sections 104-1 to 104-4) may perform the following operations.

[0175] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0176] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-3π(m-1) / 5 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-3 / (10Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0177] The third Doppler shift unit 104 applies a phase rotation Φ3(m)=-π(m-1) / 5 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP3=-1 / (10Tr) to the third transmitting antenna Tx#3, and outputs the result.

[0178] The fourth Doppler shift unit 104 applies a phase rotation Φ4(m)=3π(m-1) / 5 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=3 / (10Tr) to the fourth transmitting antenna Tx#4, and outputs the result.

[0179] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0180] In FIG. 11, the interval between the Doppler shift amounts (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#4 is Δfd (1, 2) =Δfd, Δfd (2, 3) =Δfd, Δfd (3, 4) =2Δfd, Δfd (4, 1) Therefore, in FIG. 11, the intervals of the Doppler shift amounts given to the four transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (1, 2) =Δfd (2, 3) =Δfd (4, 1) ≠Δfd (3, 4) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0181] In addition, in FIG. 11, the interval of the Doppler shift amount between the transmitting antennas Tx#1 and Tx#2, which are PL1 polarized waves, is Δfd (1, 2) =Δfd, Δfd (2, 1) = 4Δfd. Therefore, the number of PL1 polarized transmitting antennas N PL1 The intervals of the Doppler shifts given to each of the PL1 polarization transmitting antennas of =2 are not all the same interval, but include unequal intervals (Δfd (1, 2) ≠Δfd (2, 1 ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed using a PL1 polarized transmitting antenna.

[0182] In addition, in FIG. 11, the interval of the Doppler shift amount between the transmitting antennas Tx#3 and Tx#4, which are PL2 polarized waves, is Δfd (3, 4) =2Δfd, Δfd (4, 3) = 3Δfd. Therefore, the number of PL2 polarized transmitting antennas N PL2 The intervals of the Doppler shifts given to each of the PL2 polarization transmitting antennas of =2 are not all the same interval, but include unequal intervals (Δfd (3, 4) ≠Δfd (4, 3) ), and unevenly spaced Doppler multiplexing transmission (unevenly spaced DDM transmission) using a PL2 polarized antenna.

[0183] From the above, the example shown in FIG. 11 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 1.

[0184] In addition, in FIG. 11, the interval of the Doppler shift amount between the PL1 polarization transmitting antennas Tx#1 and Tx#2 is Δfd (1, 2) =Δfd, Δfd (2, 1) = 4Δfd, and the interval of the Doppler shift amount between the PL2 polarization transmitting antennas Tx#3 and Tx#4 is Δfd (3, 4) =2Δfd, Δfd (4, 3) =3Δfd. Therefore, the amount of Doppler shift between the PL1 polarized wave transmitting antennas Tx#1 and Tx#2 and the amount of Doppler shift between the PL2 polarized wave transmitting antennas Tx#3 and Tx#4 include different Doppler shift intervals.

[0185] For example, the maximum DDM interval for the Doppler shift between PL1 polarization transmitting antennas Tx#1 and Tx#2 is Δfd (2, 1) = 4Δfd, and the maximum DDM interval of the Doppler shift between PL2 polarization transmitting antennas Tx#3 and Tx#4 is Δfd (4, 3) =3Δfd, which are different from each other.

[0186] Similarly, for example, the minimum DDM interval of the Doppler shift between PL1 polarization transmitting antennas Tx#1 and Tx#2 is Δfd (1, 2) = Δfd, and the minimum DDM interval for the Doppler shift between PL2 polarization transmitting antennas Tx#3 and Tx#4 is Δfd (3, 4) =2Δfd, which are different from each other.

[0187] As described above, in the example shown in FIG. 11, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0188] From the above, the example shown in FIG. 11 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2(1).

[0189] For example, Figure 12 shows an example of the received signal at the output of the Doppler analysis unit 209 when a transmitting antenna unit 105 is used in which the PL1 polarization is left-handed circular polarization (LC) and the PL2 polarization is right-handed circular polarization (RC) according to the Doppler shift amount settings shown in Figure 11, and an LC polarization (PL1 polarization) antenna is used for the receiving antenna unit 202.

[0190] FIG. 12 shows the output of the Doppler analysis unit 209 for a target reflected wave at a certain distance index. For example, the target reflected wave has fd target Therefore, as shown in FIG. 12, the radar device 10 calculates the Doppler frequency fd from the Doppler shift amount shown in FIG. target A signal subjected to a minute Doppler shift is received.

[0191] Here, when the reflected wave of the radar transmission wave reflected by the target includes a large number of scattered waves or a large number of reflections, the reflected wave may include a variety of polarized waves. Therefore, the difference in reception level between the received signals corresponding to different polarized wave transmitting antennas (e.g., PL1 polarized wave transmitting antenna and PL2 polarized wave transmitting antenna) at the radar device 10 is unlikely to be large. Therefore, the radar device 10 receives the received signal corresponding to the RC polarized wave (PL2 polarized wave) transmitting antenna and the received signal corresponding to the LC polarized wave (PL1 polarized wave) transmitting antenna at approximately the same reception level.

[0192] For example, when the Doppler shift amount is set as shown in Fig. 11, if the target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)) is not included, the received signal shown in Fig. 12(a) is obtained. As shown in Fig. 12(a), the reception levels of the received signals corresponding to the transmitting antennas Tx#1, Tx#2 (PL1 polarization), Tx#3, and Tx#4 (PL2 polarization) are approximately the same.

[0193] Furthermore, for example, when the radar device 10 receives a reflected wave that is specularly reflected by a target (e.g., a specular reflection from a smooth surface) from a radar transmission wave (e.g., a single specular reflection), the reception level may differ between polarized transmitting antennas. For example, a received signal corresponding to an LC polarization (PL1 polarization) transmitting antenna is a signal of the same polarization as the receiving antenna. On the other hand, a received signal corresponding to an RC polarization (PL2 polarization) transmitting antenna is a signal of cross-polarization with respect to the LC polarization (PL1 polarization) receiving antenna. Therefore, the received signal corresponding to an RC polarization (PL2 polarization) transmitting antenna may have a lower reception level (depending on the cross-polarization discrimination of the antenna, for example, 10 dB or more lower) than the received signal corresponding to an LC polarization (PL1 polarization) transmitting antenna. For example, depending on the reception SNR, the received signal corresponding to an RC polarization (PL2 polarization) transmitting antenna may be below the noise level, making it difficult for the radar device 10 to detect the Doppler frequency peak.

[0194] For example, when the Doppler shift amount is set as shown in Fig. 11, if a target reflected wave is included in which the RC polarization (PL2 polarization) is cross-polarized with respect to the polarization of the receiving antenna (for example, the LC polarization (PL1 polarization)), a received signal such as that shown in Fig. 12(b) is obtained. As shown in Fig. 12(b), the reception levels of the received signals corresponding to the transmitting antennas Tx#3 and Tx#4 (PL2 polarization) are smaller than the reception levels of the received signals corresponding to the transmitting antennas Tx#1 and Tx#2 (PL1 polarization).

[0195] Furthermore, for example, when the radar device 10 receives a reflected wave that is specularly reflected by a target and then specularly reflected by a road surface or the like (e.g., two specular reflections), the reception level may differ between the polarized transmitting antennas. For example, a received signal corresponding to an RC-polarized (PL2) transmitting antenna will be a signal of the same polarization as that of an LC-polarized (PL1) receiving antenna. On the other hand, a received signal corresponding to an LC-polarized (PL1) transmitting antenna will be a signal of cross-polarization with that of an LC-polarized (PL1) receiving antenna. Therefore, the received signal corresponding to an LC-polarized (PL1) transmitting antenna may have a lower reception level (depending on the cross-polarization discrimination of the antenna, for example, 10 dB or more lower) than that of a received signal corresponding to an RC-polarized (PL2) transmitting antenna. For example, depending on the reception SNR, the received signal from the LC-polarized (PL1) transmitting antenna may be below the noise level, making it difficult for the radar device 10 to detect the Doppler frequency peak.

[0196] For example, when the Doppler shift amount is set as shown in Fig. 11, if a target reflected wave is included in which the LC polarization (PL1 polarization) is cross-polarized with respect to the polarization of the receiving antenna (e.g., LC polarization (PL1 polarization)), a received signal such as that shown in Fig. 12(c) is obtained. As shown in Fig. 12(c), the reception levels of the received signals corresponding to the transmitting antennas Tx#1 and Tx#2 (PL1 polarization) are smaller than the reception levels of the received signals corresponding to the transmitting antennas Tx#3 and Tx#4 (PL2 polarization).

[0197] For example, as shown in (a) of FIG. 12, when no target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas are included, the radar device 10 receives signals corresponding to the RC polarization (PL2 polarization) transmitting antennas (Tx#3 and Tx#4) and the LC polarization (PL1 polarization) transmitting antennas (Tx#1 and Tx#2) at approximately the same level. In (a) of FIG. 12, signals transmitted from Nt transmitting antennas Tx#1, Tx#2, Tx#3, and Tx#4, each consisting of an RC polarization (PL2 polarization) transmitting antenna and an LC polarization (PL1 polarization) transmitting antenna, are Doppler-multiplexed and transmitted using Doppler shift intervals resulting in uneven Doppler multiplexing. Therefore, the radar device 10 can demultiplex a Doppler-multiplexed signal based on the existing demultiplexing operation of a Doppler-multiplexed signal.

[0198] 12(b) and 12(c), when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (e.g., Doppler multiplexed signals that satisfy condition 2(1)) when the PL2 polarization includes a target reflected wave that is cross-polarized (FIG. 12(b)) and when the PL1 polarization includes a target reflected wave that is cross-polarized (FIG. 12(c)). For example, in FIG. 12(b), the radar device 10 receives a Doppler multiplexed signal that satisfies condition 2(1) when the Doppler shift interval Δfd (1, 2) or Δfd (2, 1) In Fig. 12(c), the Doppler shift interval Δfd (3, 4) or Δfd (4, 3) The two Doppler frequency components are received.

[0199] In this way, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0200] This enables the radar device 10 to determine, for example, based on the detected Doppler frequency peaks (e.g., the interval between peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization (LC polarization) transmitting antenna has occurred or whether a decrease in the reception level of the reception signal corresponding to the PL2 polarization (RC polarization) transmitting antenna has occurred in the Doppler multiplexing separation unit 211 described later.

[0201] For example, the Doppler multiplexed signal of LC polarization (PL1 polarization) is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by an LC polarization (PL1 polarization) transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0202] Similarly, for example, a Doppler multiplexed signal of RC polarization (PL2 polarization) is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by an RC polarization (PL2 polarization) transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0203] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), and obtain an output that corresponds to a transmitting antenna for each Doppler multiplexed signal.

[0204] Setting example 1 and setting example 2 of the Doppler shift amount have been described above. Different Doppler setting examples will be described below. Note that in setting example 1 and setting example 2, the PL1 polarization is described as LC polarization and the PL2 polarization is described as RC polarization, but this is not limited to this. For example, when using polarizations in which the PL1 polarization and the PL2 polarization are orthogonal to each other, a phenomenon occurs in which a transmission signal from one of the transmitting polarization antennas includes a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna. In the setting examples below, explanations will be given using PL1 polarization and PL2 polarization.

[0205] <Doppler shift amount setting example 3> Figure 13 shows the number of transmit antennas, Nt=6, N PL1 =3, N PL2 13 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .times. ...

[0206] In the third example of setting the amount of Doppler shift, as shown in FIG. 13, the basic unit of the Doppler shift interval in the Doppler shifter 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (7Tr) and δ=1, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0207] In the example shown in FIG. 13, the first to sixth Doppler shift sections 104 (or the Doppler shift sections 104-1 to 104-6) may perform the following operations.

[0208] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0209] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-5π(m-1) / 7 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-5 / (14Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0210] The third Doppler shift unit 104 applies a phase rotation Φ3(m)=-3π(m-1) / 7 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP3=-3 / (14Tr) to the third transmitting antenna Tx#3, and outputs the result. The fourth Doppler shift unit 104 applies a phase rotation Φ4(m)=-π(m-1) / 7 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=-1 / (14Tr) to the fourth transmitting antenna Tx#4, and outputs the result. The fifth Doppler shift unit 104 applies a phase rotation Φ5(m)=3π(m-1) / 7 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP5=3 / (14Tr) to the fifth transmitting antenna Tx#5, and outputs the result. The sixth Doppler shift unit 104 applies a phase rotation Φ6(m)=5π(m-1) / 7 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP6=5 / (14Tr) to the sixth transmitting antenna Tx#6, and outputs the result.

[0211] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0212] In FIG. 13, the interval between the Doppler shift amounts (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#6 is Δfd (1, 2) =Δfd (2, 3) =Δfd (3, 4) =Δfd (5, 6) =Δfd (6, 1) =Δfd, Δfd (4, 5)Therefore, in FIG. 13, the intervals of the Doppler shift amounts given to the six transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (1, 2) =Δfd (2, 3) =Δfd (3, 4) =Δfd (5, 6) =Δfd (6, 1) ≠Δfd (4, 5) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0213] In addition, in FIG. 13, among the transmitting antennas, the interval of the Doppler shift amount between the transmitting antennas Tx#1, Tx#2, and Tx#4 which are PL1 polarized waves is Δfd (1, 2) =Δfd, Δfd (2, 4) =2Δfd, Δfd (4, 1) = 4Δfd. Therefore, the number of PL1 polarized transmitting antennas N PL1 The intervals of the Doppler shifts given to each of the three PL1 polarization transmitting antennas are not all the same, but include unequal intervals (Δfd (1, 2) ≠Δfd (2, 4) ≠Δfd (4, 1) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed using a PL1 polarized transmitting antenna.

[0214] In addition, in FIG. 13, among the transmitting antennas, the interval of the Doppler shift amount between the transmitting antennas Tx#3, Tx#5, and Tx#6 which are PL2 polarized waves is Δfd (3, 5) =3Δfd, Δfd (5, 6) =Δfd, Δfd (6, 3) = 3Δfd. Therefore, the number of PL2 polarized transmitting antennas N PL2 The intervals of the Doppler shifts given to each of the three PL2 polarization transmitting antennas are not all the same, but include unequal intervals (Δfd (3, 5) =Δfd (6, 3) ≠Δfd (5, 6) ), and unevenly spaced Doppler multiplexing transmission (unevenly spaced DDM transmission) using a PL2 polarized antenna.

[0215] From the above, the example shown in FIG. 13 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 1.

[0216] In addition, in FIG. 13, the intervals of the Doppler shift amounts between the PL1 polarization transmitting antennas Tx#1, Tx#2, and Tx#4 are Δfd (1, 2) =Δfd, Δfd (2, 4) =2Δfd, Δfd (4, 1) = 4Δfd, and the interval of the Doppler shift amount between the PL2 polarization transmitting antennas Tx#3, Tx#5, and Tx#6 is Δfd (3, 5) =3Δfd, Δfd (5, 6) =Δfd, Δfd (6, 3) =3Δfd. Therefore, the amount of Doppler shift between the PL1 polarization transmitting antennas Tx#1, Tx#2, and Tx#4 and the amount of Doppler shift between the PL2 polarization transmitting antennas Tx#3, Tx#5, and Tx#6 include different Doppler shift intervals.

[0217] For example, the intervals between the Doppler shift amounts of PL1 polarized transmitting antennas Tx#1, Tx#2, and Tx#4 include 2Δfd and 4Δfd, but the intervals between the Doppler shift amounts of PL2 polarized transmitting antennas Tx#3, Tx#5, and Tx#6 do not include 2Δfd and 4Δfd.

[0218] Also, for example, the maximum DDM interval of the Doppler shift amount between PL2 polarization transmitting antennas Tx#3, Tx#5 and Tx#6 is 3Δfd, but the interval of the Doppler shift amount between PL1 polarization transmitting antennas Tx#1, Tx#2 and Tx#4 does not include 3Δfd.

[0219] As described above, in the example shown in FIG. 13, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0220] From the above, the example shown in FIG. 13 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2(1).

[0221] For example, if the radar device 10 does not include target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas, the radar device 10 receives signals corresponding to the PL1 polarization transmitting antennas (Tx#1, Tx#2, and Tx#4) and the PL2 polarization transmitting antennas (Tx#3, Tx#5, and Tx#6) at approximately the same level. Here, signals transmitted from the Nt transmitting antennas Tx#1 to Tx#6, which are made up of the PL1 polarization transmitting antennas and the PL2 polarization transmitting antennas, are Doppler-multiplexed and transmitted using Doppler shift intervals resulting in uneven interval Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler-multiplexed signal based on the existing operation of demultiplexing a Doppler-multiplexed signal.

[0222] Furthermore, when a target reflected wave that is cross-polarized relative to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 2 (1)) depending on whether the PL1 polarization includes a target reflected wave that is cross-polarized or the PL2 polarization includes a target reflected wave that is cross-polarized.

[0223] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0224] This allows the radar device 10 to determine, for example, based on the detected Doppler frequency peaks (e.g., the interval between peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization transmitting antenna or a decrease in the reception level of the reception signal corresponding to the PL2 polarization transmitting antenna has occurred in the Doppler demultiplexing unit 211 described later.

[0225] For example, the PL1 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to the signal transmitted by the PL1 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0226] Similarly, for example, a PL2 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by a PL2 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0227] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), and obtain an output that corresponds to a transmitting antenna for each Doppler multiplexed signal.

[0228] <Doppler shift amount setting example 4> Figure 14 shows the number of transmit antennas, Nt=6, N PL1 =3, N PL2 14 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .times. ...

[0229] In the fourth example of setting the amount of Doppler shift, as shown in FIG. 14, the basic unit of the Doppler shift interval in the Doppler shifter 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (8Tr) and δ=2, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0230] In the example shown in FIG. 14, the first to sixth Doppler shift sections 104 (or Doppler shift sections 104-1 to 104-6) may perform the following operations.

[0231] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0232] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-π(m-1) / 2 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-1 / (4Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0233] The third Doppler shift unit 104 applies a phase rotation Φ3(m)=-π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP3=-1 / (8Tr) to the third transmitting antenna Tx#3, and outputs the result.

[0234] The fourth Doppler shift unit 104 imparts a phase rotation Φ4(m)=0 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=0 to the fourth transmitting antenna Tx#4, and outputs the result.

[0235] The fifth Doppler shift unit 104 applies a phase rotation Φ5(m)=π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP5=1 / (8Tr) to the fifth transmitting antenna Tx#5, and outputs the result.

[0236] The sixth Doppler shift unit 104 applies a phase rotation Φ6(m)=π(m-1) / 2 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP6=1 / (4Tr) to the sixth transmitting antenna Tx#6, and outputs the result.

[0237] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0238] In FIG. 14, the interval between the Doppler shift amounts (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#6 is Δfd (1, 2) =2Δfd, Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd (5, 6) =Δfd, Δfd (6, 1) Therefore, in FIG. 14, the intervals of the Doppler shift amounts given to the six transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd (5, 6) ≠Δfd (1, 2) =Δfd (6, 1) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0239] In addition, in FIG. 14, among the transmitting antennas, the interval of the Doppler shift amount between the transmitting antennas Tx#1, Tx#4, and Tx#6 which are PL1 polarized waves is Δfd (1, 4) = 4Δfd, Δfd (4, 6) =2Δfd, Δfd (6, 1) = 2Δfd. Therefore, the number of PL1 polarized transmitting antennas N PL1 The intervals of the Doppler shifts given to each of the three PL1 polarization transmitting antennas are not all the same, but include unequal intervals (Δfd (1, 4) ≠Δfd (4, 6) =Δfd (6, 1) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed using a PL1 polarized transmitting antenna.

[0240] In addition, in FIG. 14, among the transmitting antennas, the interval of the Doppler shift amount between the transmitting antennas Tx#2, Tx#3, and Tx#5 which are PL2 polarized waves is Δfd (2, 3) =Δfd, Δfd (3, 5) =2Δfd, Δfd(5, 2) = 5Δfd. Therefore, the number of PL2 polarized transmitting antennas N PL2 The intervals of the Doppler shifts given to each of the three PL2 polarization transmitting antennas are not all the same, but include unequal intervals (Δfd (2, 3) ≠Δfd (3, 5) ≠Δfd (5, 2) ), and unevenly spaced Doppler multiplexing transmission (unevenly spaced DDM transmission) using a PL2 polarized antenna.

[0241] From the above, the example shown in FIG. 14 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 1.

[0242] In addition, in FIG. 14, the intervals of the Doppler shift amounts between the PL1 polarization transmitting antennas Tx#1, Tx#4, and Tx#6 are Δfd (1, 4) = 4Δfd, Δfd (4, 6) =2Δfd, Δfd (6, 1) = 2Δfd, and the interval of the Doppler shift amount between the PL2 polarization transmitting antennas Tx#2, Tx#3, and Tx#5 is Δfd (2, 3) =Δfd, Δfd (3, 5) =2Δfd, Δfd (5, 2) =5Δfd. Therefore, the amount of Doppler shift between the PL1 polarization transmitting antennas Tx#1, Tx#4, and Tx#6 and the amount of Doppler shift between the PL2 polarization transmitting antennas Tx#2, Tx#3, and Tx#5 include different Doppler shift intervals.

[0243] For example, the interval between the Doppler shift amounts of PL1 polarized transmitting antennas Tx#1, Tx#4, and Tx#6 includes 4Δfd, but the interval between the Doppler shift amounts of PL2 polarized transmitting antennas Tx#2, Tx#3, and Tx#5 does not include 4Δfd.

[0244] Also, for example, the maximum DDM interval for the Doppler shift amount between PL2 polarization transmitting antennas Tx#2, Tx#3, and Tx#5 includes Δfd and 5Δfd, but the Doppler shift amount between PL1 polarization transmitting antennas Tx#1, Tx#4, and Tx#6 does not include Δfd and 5Δfd.

[0245] As described above, in the example shown in FIG. 14, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0246] From the above, the example shown in FIG. 14 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2(1).

[0247] For example, if the radar device 10 does not include target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas, the radar device 10 receives signals corresponding to the PL1 polarization transmitting antennas (Tx#1, Tx#4, and Tx#6) and the PL2 polarization transmitting antennas (Tx#2, Tx#3, and Tx#5) at approximately the same level. Here, signals transmitted from the Nt transmitting antennas Tx#1 to Tx#6, which are made up of the PL1 polarization transmitting antennas and the PL2 polarization transmitting antennas, are Doppler-multiplexed and transmitted using Doppler shift intervals resulting in uneven Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler-multiplexed signal based on the existing operation of demultiplexing a Doppler-multiplexed signal.

[0248] Furthermore, when a target reflected wave that is cross-polarized relative to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 2 (1)) depending on whether the PL1 polarization includes a target reflected wave that is cross-polarized or the PL2 polarization includes a target reflected wave that is cross-polarized.

[0249] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0250] This allows the radar device 10 to determine, for example, based on the detected Doppler frequency peaks (e.g., the interval between peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization transmitting antenna or a decrease in the reception level of the reception signal corresponding to the PL2 polarization transmitting antenna has occurred in the Doppler demultiplexing unit 211 described later.

[0251] For example, the PL1 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to the signal transmitted by the PL1 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0252] Similarly, for example, a PL2 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by a PL2 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0253] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), and obtain an output that corresponds to a transmitting antenna for each Doppler multiplexed signal.

[0254] <Doppler shift amount setting example 5> Figure 15 shows the number of transmit antennas, Nt=6, N PL1 =3, N PL2 15 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .times. ...

[0255] In the fifth example of setting the amount of Doppler shift, as shown in FIG. 15, the basic unit of the Doppler shift interval in the Doppler shifter 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (8Tr) and δ=2, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0256] In the example shown in FIG. 15, the first to sixth Doppler shift sections 104 (or Doppler shift sections 104-1 to 104-6) may perform the following operations.

[0257] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0258] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-3π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-3 / (8Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0259] The third Doppler shift unit 104 applies a phase rotation Φ3(m)=-π(m-1) / 2 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP3=-1 / (4Tr) to the third transmitting antenna Tx#3, and outputs the result.

[0260] The fourth Doppler shift unit 104 applies a phase rotation Φ4(m)=-π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=-1 / (8Tr) to the fourth transmitting antenna Tx#4, and outputs the result.

[0261] The fifth Doppler shifter 104 imparts a Doppler shift amount DOP5=0 to the fifth transmitting antenna Tx#5, for example, by imparting a phase rotation Φ5(m)=0 to the chirp signal for each transmission period Tr and outputting the signal.

[0262] The sixth Doppler shift unit 104 applies a phase rotation Φ6(m)=π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP6=1 / (8Tr) to the sixth transmitting antenna Tx#6, and outputs the result.

[0263] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0264] In FIG. 15, the interval between the Doppler shift amounts (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#6 is Δfd (1, 2) =Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd (5, 6) =Δfd, Δfd (6, 1) Therefore, in FIG. 15, the intervals of the Doppler shift amounts given to the six transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (1, 2) =Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd (5, 6) ≠Δfd (6, 1) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0265] In addition, in FIG. 15, among the transmitting antennas, the interval of the Doppler shift amount between the transmitting antennas Tx#1, Tx#2, and Tx#4 which are PL1 polarized waves is Δfd (1, 2) =Δfd, Δfd (2, 4) =2Δfd, Δfd (4, 1) = 5Δfd. Therefore, the number of PL1 polarized transmitting antennas N PL1The intervals of the Doppler shifts given to each of the three PL1 polarization transmitting antennas are not all the same, but include unequal intervals (Δfd (1, 2) ≠Δfd (2, 4) =Δfd (4, 1) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed using a PL1 polarized transmitting antenna.

[0266] In addition, in FIG. 15, among the transmitting antennas, the interval of the Doppler shift amount between the transmitting antennas Tx#3, Tx#5, and Tx#6 which are PL2 polarized waves is Δfd (3, 5) =2Δfd, Δfd (5, 6) =Δfd, Δfd (6, 3) = 5Δfd. Therefore, the number of PL2 polarized transmitting antennas N PL2 The intervals of the Doppler shifts given to each of the three PL2 polarization transmitting antennas are not all the same, but include unequal intervals (Δfd (3, 5) ≠Δfd (5, 6) ≠Δfd (6, 3) ), and unevenly spaced Doppler multiplexing transmission (unevenly spaced DDM transmission) using a PL2 polarized antenna.

[0267] From the above, the example shown in FIG. 15 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 1.

[0268] In addition, in FIG. 15, the amount of Doppler shift between the PL1 polarization transmitting antennas Tx#1, Tx#2, and Tx#4 is Δfd (1, 2) =Δfd, Δfd (2, 4) =2Δfd, Δfd (4, 1) =5Δfd, and the amount of Doppler shift between the PL2 polarization transmitting antennas Tx#3, Tx#5, and Tx#6 is Δfd (3, 5) =2Δfd, Δfd (5, 6) =Δfd, Δfd (6, 3) =5Δfd. In this way, the Doppler shift amounts between PL1 polarization transmitting antennas Tx#1, Tx#2, and Tx#4 and the Doppler shift amounts between PL2 polarization transmitting antennas Tx#3, Tx#5, and Tx#6 include the same combination of Doppler shift intervals, but the order of the Doppler shift intervals between the PL1 polarization and the PL2 polarization in the Doppler frequency domain is different.

[0269] For example, in FIG. 15, the order of the Doppler shift intervals assigned to each of the PL1 polarization transmitting antennas Tx#1, Tx#2, and Tx#4 is Δfd, 2Δfd, and 5Δfd. Also, in FIG. 15, the order of the Doppler shift intervals assigned to each of the PL2 polarization transmitting antennas Tx#3, Tx#5, and Tx#6 is 2Δfd, Δfd, and 5Δfd. Therefore, in FIG. 15, the same combination of Doppler shift intervals (e.g., Δfd, 2Δfd, and 5Δfd) is included for the PL1 polarization transmitting antennas and the PL2 polarization transmitting antennas, but the order of these intervals is different between the polarizations. For example, in FIG. 15, even if the Doppler shift intervals between the PL1 polarization transmitting antennas or the PL2 polarization transmitting antennas are cyclically shifted in the Doppler frequency domain, the Doppler shift amounts do not match between the polarizations.

[0270] As described above, in the example shown in FIG. 15, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0271] From the above, the example shown in FIG. 15 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2(3).

[0272] For example, if the radar device 10 does not include target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas, the radar device 10 receives signals corresponding to the PL1 polarization transmitting antennas (Tx#1, Tx#2, and Tx#4) and the PL2 polarization transmitting antennas (Tx#3, Tx#5, and Tx#6) at approximately the same level. Here, signals transmitted from the Nt transmitting antennas Tx#1 to Tx#6, which are made up of the PL1 polarization transmitting antennas and the PL2 polarization transmitting antennas, are Doppler-multiplexed and transmitted using Doppler shift intervals resulting in uneven interval Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler-multiplexed signal based on the existing operation of demultiplexing a Doppler-multiplexed signal.

[0273] Furthermore, when a target reflected wave that is cross-polarized relative to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 2 (3)) depending on whether the PL1 polarization includes a target reflected wave that is cross-polarized or the PL2 polarization includes a target reflected wave that is cross-polarized.

[0274] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0275] This allows the radar device 10 to determine, for example, based on the detected Doppler frequency peaks (e.g., the order of Doppler shift intervals), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization transmitting antenna or a decrease in the reception level of the reception signal corresponding to the PL2 polarization transmitting antenna has occurred, in the Doppler demultiplexing unit 211 described later.

[0276] For example, the PL1 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to the signal transmitted by the PL1 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0277] Similarly, for example, a PL2 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by a PL2 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0278] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), and obtain an output that corresponds to a transmitting antenna for each Doppler multiplexed signal.

[0279] <Doppler shift amount setting example 6> Figure 16 shows the number of transmit antennas, Nt=5, N PL1 =3, N PL2 16 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .gtoreq.2. In FIG. 16, Tx#3, Tx#4, and Tx#5 are PL1 polarized wave transmission antennas, and Tx#1 and Tx#2 are PL2 polarized wave transmission antennas.

[0280] In the sixth example of setting the Doppler shift amount, as shown in FIG. 16, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (6Tr) and δ=1, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0281] In the example shown in FIG. 16, the first to fifth Doppler shift sections 104 (or the Doppler shift sections 104-1 to 104-5) may perform the following operations.

[0282] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0283] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-2π(m-1) / 3 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-1 / (3Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0284] The third Doppler shift unit 104 imparts a Doppler shift amount DOP3=-1 / (6Tr) to the third transmitting antenna Tx#3, for example, by imparting a phase rotation Φ3(m)=-π(m-1) / 3 to the chirp signal for each transmission period Tr and outputting the result.

[0285] The fourth Doppler shift unit 104 imparts a phase rotation Φ4(m)=0 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=0 to the fourth transmitting antenna Tx#4, and outputs the result.

[0286] The fifth Doppler shift unit 104 applies a phase rotation Φ5(m)=π(m-1) / 3 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP5=1 / (6Tr) to the fifth transmitting antenna Tx#5, and outputs the result.

[0287] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0288] In FIG. 16, the interval between the Doppler shift amounts (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#5 is Δfd (1, 2) =Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd, Δfd (5, 1) Therefore, in FIG. 16, the intervals of the Doppler shift amounts given to the five transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (1, 2) =Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) ≠Δfd (5, 1) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0289] In addition, in FIG. 16, among the transmitting antennas, the interval of the Doppler shift amount between the transmitting antennas Tx#3, Tx#4, and Tx#5 which are PL1 polarized waves is Δfd(3, 4) =Δfd, Δfd (4, 5) =Δfd, Δfd (5, 3) = 4Δfd. Therefore, the number of PL1 polarized transmitting antennas N PL1 The intervals of the Doppler shifts given to each of the three PL1 polarization transmitting antennas are not all the same, but include unequal intervals (Δfd (3, 4) =Δfd (4, 5) ≠Δfd (5, 3) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed using a PL1 polarized transmitting antenna.

[0290] In addition, in FIG. 16, the interval of the Doppler shift amount between the transmitting antennas Tx#1 and Tx#2 which are PL2 polarized waves is Δfd (1, 2) =Δfd, Δfd (2, 1) = 5Δfd. Therefore, the number of PL2 polarized transmitting antennas N PL2 The intervals of the Doppler shifts given to each of the PL2 polarization transmitting antennas of =2 are not all the same interval, but include unequal intervals (Δfd (1, 2) ≠Δfd (2, 1) ), and unevenly spaced Doppler multiplexing transmission (unevenly spaced DDM transmission) using a PL2 polarized antenna.

[0291] From the above, the example shown in FIG. 16 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 1.

[0292] In addition, in FIG. 16, the intervals of the Doppler shift amounts between the PL1 polarization transmitting antennas Tx#3, Tx#4, and Tx#5 are Δfd (3, 4) =Δfd, Δfd (4, 5) =Δfd, Δfd (5, 3) = 4Δfd, and the interval of the Doppler shift amount between the PL2 polarization transmitting antennas Tx#1 and Tx#2 is Δfd (1, 2) =Δfd, Δfd (2, 1) =5Δfd. Therefore, the amount of Doppler shift between the PL1 polarization transmitting antennas Tx#3, Tx#4, and Tx#5 and the amount of Doppler shift between the PL2 polarization transmitting antennas Tx#1 and Tx#2 include different Doppler shift intervals.

[0293] For example, the interval between the Doppler shift amounts of PL1 polarized transmitting antennas Tx#3, Tx#4, and Tx#5 includes 4Δfd, but the interval between the Doppler shift amounts of PL2 polarized transmitting antennas Tx#1 and Tx#2 does not include 4Δfd.

[0294] Also, for example, the interval between the Doppler shift amounts between PL2 polarization transmitting antennas Tx#1 and Tx#2 includes 5Δfd, but the interval between the Doppler shift amounts between PL1 polarization transmitting antennas Tx#3, Tx#4 and Tx#5 does not include 5Δfd.

[0295] In addition, in FIG. 16, the Doppler multiplexing number (or the number of transmitting antennas) differs between the PL1 polarization and the PL2 polarization (N PL1 ≠N PL2 ).

[0296] As described above, in the example shown in FIG. 16, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0297] From the above, the example shown in FIG. 16 is an example of setting a pattern of the amount of Doppler shift that satisfies (1) and (2) of Condition 2.

[0298] For example, if the radar device 10 does not include target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas, the radar device 10 receives signals corresponding to the PL1 polarization transmitting antennas (Tx#3, Tx#4, and Tx#5) and the PL2 polarization transmitting antennas (Tx#1 and Tx#2) at approximately the same level. Here, signals transmitted from the Nt transmitting antennas Tx#1 to Tx#5, which are made up of the PL1 polarization transmitting antennas and the PL2 polarization transmitting antennas, are Doppler-multiplexed and transmitted using Doppler shift intervals that result in uneven interval Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler-multiplexed signal based on the existing operation of demultiplexing a Doppler-multiplexed signal.

[0299] Furthermore, when a target reflected wave that is cross-polarized relative to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy conditions (1) and (2) of condition 2) depending on whether the PL1 polarization includes a target reflected wave that is cross-polarized or the PL2 polarization includes a target reflected wave that is cross-polarized.

[0300] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0301] This allows the radar device 10 to determine, for example, based on the detected Doppler frequency peaks (e.g., Doppler shift intervals or the number of peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization transmitting antenna or a decrease in the reception level of the reception signal corresponding to the PL2 polarization transmitting antenna has occurred in the Doppler demultiplexing unit 211 described later.

[0302] For example, the PL1 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to the signal transmitted by the PL1 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0303] Similarly, for example, a PL2 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by a PL2 polarized transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0304] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), and obtain an output that corresponds to a transmitting antenna for each Doppler multiplexed signal.

[0305] An example of setting the amount of Doppler shift has been described above.

[0306] The setting of the Doppler shift amount is not limited to the above-mentioned setting examples 1 to 6. For example, the number of transmitting antennas Nt (or the number of Doppler multiplexing), the number of PL1 polarization transmitting antennas N PL1 , PL2 polarized transmitting antenna number N PL2 , and at least one of the Doppler shift intervals may be other values.

[0307] In addition, the Doppler shift unit 104 calculates the Doppler shift amount DOP for the radar transmission signals transmitted from the Nt transmission antennas. n Phase rotation Φ n (m) may be expressed as the following equation (4):

number

[0308] where Φ is the initial phase and ΔΦ is the reference Doppler shift phase.

[0309] For example, when Doppler multiplexing is performed using three transmitting antennas Nt, the first Doppler shifter 104 applies a phase rotation Φ1(m) to the radar transmission signal (e.g., a chirp signal) input from the radar transmission signal generator 101 for each transmission period Tr, as shown in the following equation (5). The output of the first Doppler shifter 104 is output, for example, from the first transmitting antenna (Tx#1). Here, cp(t) represents the chirp signal for each transmission period.

number

[0310] Furthermore, for example, the second Doppler shifter 104 applies a phase rotation Φ2(m) to the radar transmission signal (e.g., a chirp signal) input from the radar transmission signal generator 101 for each transmission period Tr, as shown in the following equation (6). The output of the second Doppler shifter 104 is output from, for example, the second transmitting antenna (Tx#2).

number

[0311] Similarly, for example, the third Doppler shifter 104 applies a phase rotation Φ3(m) to the radar transmission signal (e.g., a chirp signal) input from the radar transmission signal generator 101 for each transmission period Tr, as shown in the following equation (7). The output of the third Doppler shifter 104 is output from, for example, the third transmitting antenna (Tx#3).

number

[0312] An example of setting the amount of Doppler shift has been described above.

[0313] Next, an example of the operation of the CFAR unit 210 and the Doppler demultiplexing unit 211 corresponding to the operation of the Doppler shift unit 104 described above will be described.

[0314] [Example of operation of CFAR unit 210] For example, the CFAR unit 210 may perform the following operation example 1 or operation example 2 to receive a reflected wave signal in response to a radar transmission signal from the radar transmitter 100.

[0315] In the following description, an example of operation of the CFAR unit 210 will be described when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas with the same polarization. An example of operation of the CFAR unit 210 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas with different polarizations will be described later.

[0316] <Example 1 of the Operation of CFAR Unit 210> In Example 1 of the operation, an example of the operation of CFAR unit 210 when the value of δ shown in Equation (3) is set to a positive integer in Doppler shift unit 104 will be described.

[0317] In this case, for the interval of the Doppler shift amount assigned to the Doppler multiplexed signals, an interval of Δfd or an interval that is an integer multiple of Δfd is used. Therefore, each signal that is Doppler multiplexed can be detected as being folded at an interval of Δfd in the output of the Doppler frequency domain of Doppler analysis unit 209. Utilizing such a property, for example, the operation of CFAR unit 210 can be simplified as follows.

[0318] CFAR unit 210, for example, uses a threshold value with respect to the power addition value obtained by adding the received powers of the reflected wave signals for each range (for example, the range of Δfd) that is the unit of each interval of the Doppler shift amount respectively given to the radar transmission signals among the Doppler frequency range of the output of Doppler analysis unit 209 that is the target of CFAR processing, to detect a Doppler peak.

[0319] For example, CFAR unit 210 performs CFAR processing by calculating a power addition value PowerDDM(f Δfd , f b , f s ) obtained by adding the power values PowerqFT(f b , f sddm ) shown in Equation (9) at an interval of Δfd (for example, corresponding to N

Equation

Equation

[0320] Here, f sddm = -N c / 2, ~, -N c / 2 + N Δfdis -1, and N Δfd represents the number of Doppler frequency indices included in the interval of Δfd, and N Δfd = round(Δfd / (1 / (T r N c ))). Also, round(x) is an operator that rounds the real number x and outputs an integer value.

[0321] Note that the operation of the CFAR process may be based on, for example, the operation disclosed in Non - Patent Document 2, and the description of detailed operation examples is omitted.

[0322] As a result, the Doppler frequency range to be processed by the CFAR unit 210 can be narrowed from the entire range of Doppler frequency index range f s (for example, the range of -N c / 2 to N c / 2 - 1) to the range of Δfd, so the calculation amount of the CFAR process can be reduced to 1 / (Nt + δ)=1 / (N DM + δ).

[0323] And the CFAR unit 210 adaptively sets a threshold value, for example, and outputs the distance index f b_cfar at which the received power is greater than the threshold value, the Doppler frequency index f sddm_cfar , and the received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm - 1)×N Δfd )) to the Doppler multiplex separation unit 211. Here, ndm is an integer from 1 to N DM + δ.

[0324] <Operating Example 2 of CFAR Unit 210> In Operating Example 2, an operating example of the CFAR unit 210 when the value of δ shown in Equation (3) is set to a non - positive - integer real number in the Doppler shift unit 104 will be described.

[0325] The CFAR unit 210 may, for example, calculate the power sum of equation (9) based on the outputs of the Doppler analysis units 209 of the first to Nath signal processing units 206, and detect the power peak that matches the Doppler shift interval set in the radar transmission signal for each distance index by adaptive threshold processing (CFAR processing).

[0326] Then, the CFAR unit 210 adaptively sets a threshold value, for example, and calculates the distance index f b_cfar , the Doppler frequency index f at the power peak that matches the Doppler shift interval set in the radar transmission signal s_cfar (ndm), and the Doppler frequency index f s_cfar (ndm) received power information PowerFT(f b_cfar , f s_cfar (ndm)) is output to the Doppler demultiplexing unit 211. Here, ndm = 1 to N DM +δ is an integer.

[0327] An example of the operation of the CFAR unit 210 has been described above.

[0328] In the operation example of the Doppler demultiplexing unit 211 described later, a case where the output according to the operation example 1 in the CFAR unit 210 is used will be described as an example, but the present invention is not limited to this, and the output according to the operation example 2 in the CFAR unit 210 may also be used. When the output according to the operation example 2 in the CFAR unit 210 is used, the Doppler frequency index f sddm_cfar +(ndm-1)×N Δfd Instead of the Doppler frequency index f s_cfar The difference is that it outputs (ndm), but other than that it works in the same way and has the same effect.

[0329] [Example of operation of Doppler demultiplexing unit 211] For example, when the value of δ shown in equation (3) is set to a positive integer in the Doppler shifter 104, the Doppler demultiplexer 211 calculates the distance index f b_cfar, the Doppler frequency index f sddm_cfar , and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) the following operations are performed, where ndm=1 to N DM +δ is an integer.

[0330] In the following description, an example of operation of the Doppler demultiplexing unit 211 will be described when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of the same polarization. An example of operation of the Doppler demultiplexing unit 211 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations will be described later.

[0331] 17 is a flowchart showing an example of the demultiplexing operation of the Doppler multiplexing signal in the Doppler demultiplexing unit 211. In the following, it is assumed that the Doppler velocity of the target is within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0332] <Step A-1> The Doppler demultiplexing unit 211 assumes that no target reflected wave that is a cross-polarized wave with respect to the polarization of the receiving antenna is included, and calculates Nt (=N DM Doppler demultiplexing processing is performed on the Doppler multiplexed signals (number of signals).

[0333] <Step A-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indexes (f sddm_cfar +(ndm-1)×N Δfd ) to N DM It is assumed that the signal contains Doppler multiplexed signals at irregular intervals.

[0334] The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(f b_cfar, f sddm_cfar +(ndm-1)×N Δfd ))(For example, ndm=1~N DM +δ) and compare the top N received powers. DM Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval given at the time of transmission (for example, "N DM This is called "Doppler shift interval match judgment."

[0335] Further, the Doppler demultiplexing unit 211 may demultiplex, for example, the top N signals of the received power. DM The received power levels of the Doppler frequency indexes and the top N received powers DM It is determined whether the difference (or the ratio of the reception levels) between the Doppler frequency indexes and the δ other Doppler frequency indexes is significantly different (for example, whether the difference is equal to or greater than a threshold, or whether the ratio of the reception levels is equal to or greater than a threshold) (for example, whether "N DM This is called "judgment of the difference in the received Doppler multiplexed signal level."

[0336] Based on these determinations, the Doppler demultiplexing unit 211 determines the Doppler frequency and transmitting antenna corresponding to the Doppler multiplexed signal in the range of -1 / (2Tr)≦fd<1 / (2Tr), for example.

[0337] An example of the operation of the Doppler demultiplexing unit 211 that separates the Doppler multiplexed signals at unequal intervals is disclosed in, for example, Patent Document 7, and therefore detailed description of the operation will be omitted here.

[0338] For example, the Doppler demultiplexing unit 211 DM Doppler shift interval match judgment and N DM It is determined whether or not both conditions for determining the difference in the received Doppler multiplexed signal levels (for example, the conditions in step A-2) are met. DM In the Doppler shift interval match judgment, the top N received power DM Doppler frequency index (f sddm_cfar+(ndm-1)×N Δfd ) is determined to match the Doppler shift interval given at the time of transmission, and N DM In the determination of the difference in the Doppler multiplexed signal reception levels, if it is determined that the difference in reception levels is equal to or greater than the threshold, the condition of step A-2 is met.

[0339] If the conditions of step A-2 are met, the Doppler multiplexing separation unit 211 performs processing of step A-3, and if the conditions of step A-2 are not met, the Doppler multiplexing separation unit 211 may perform processing of step B-1, assuming that the signal includes a target reflected wave in which the PL2 polarization is cross-polarized relative to the polarization of the receiving antenna.

[0340] <Step A-3> The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) among them, δ Doppler frequency indexes with small reception levels and the top N with high reception power are DM Based on the relationship with the Doppler frequency indexes, the Doppler shift amounts DOP1, DOP2, ~, DOP Nt and the Doppler frequency index are associated with each other to obtain the separation index information DDM_RXindex(f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as the distance index f b_cfar At the same time, it outputs the result to the direction estimation unit 212.

[0341] where f demul_Tx#n denotes the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the n-th transmitting antenna (Tx#n).

[0342] Furthermore, the Doppler demultiplexing unit 211 outputs, for example, the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes to the direction estimation unit 212 .

[0343] The amount of Doppler shift applied to each transmitting antenna of the transmitting antenna unit 105 in the Doppler shift unit 104 of the radar transmitter 100 is known. b_cfar ) and the Doppler shift amount given to each transmitting antenna in the radar transmitter 100 is the Doppler frequency of the target. Therefore, the Doppler demultiplexer 211 uses, for example, the separation index information DDM_RXindex(f b_cfar ), the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) may be output to the direction estimation unit 212. In this case, the direction estimation unit 212 calculates the separation index information DDM_RXindex(f b_cfar ), similar behavior can be achieved by generating

[0344] <Step B-1> The Doppler demultiplexing unit 211 assumes that the PL2 polarized wave is a cross-polarized wave relative to the polarized wave of the receiving antenna and includes a target reflected wave. PL1 The Doppler multiplexed signals are subjected to Doppler demultiplexing processing.

[0345] <Step B-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indexes (f sddm_cfar +(ndm-1)×N Δfd ) and N from the PL1 polarized transmitting antenna PL1 It is assumed that the signal contains Doppler multiplexed signals.

[0346] The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd) received power (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd ))(For example, ndm=1~N DM +δ) and compare the top N received powers. PL1 Doppler frequency index f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval given to the PL1 polarization transmitting antenna during transmission (for example, this is called "PL1 polarization Doppler shift interval match determination").

[0347] Further, the Doppler demultiplexing unit 211 may demultiplex, for example, the top N signals of the received power. PL1 Doppler frequency indexes and the top N received powers PL1 Doppler frequency indexes (N DM +δ-N PL1 ) other Doppler frequency indexes, the difference (or the ratio of the reception levels) is determined to be significantly different (for example, whether the difference is equal to or greater than a threshold, or whether the ratio of the reception levels is equal to or greater than a threshold) (for example, this is called "PL1 polarization Doppler multiplexed signal reception level difference determination").

[0348] Based on these determinations, the Doppler demultiplexing unit 211 determines the Doppler frequency and transmitting antenna corresponding to the Doppler multiplexed signal in the range of -1 / (2Tr)≦fd<1 / (2Tr), for example.

[0349] An example of the operation of the Doppler demultiplexing unit 211 that separates the Doppler multiplexed signals at unequal intervals is disclosed in, for example, Patent Document 7, and therefore detailed description of the operation will be omitted here.

[0350] For example, the Doppler demultiplexing unit 211 determines whether or not both the conditions for the PL1 polarization Doppler shift interval match determination and the PL1 polarization Doppler multiplexed signal reception level difference determination (for example, the condition in step B-2) are satisfied. PL1 Doppler frequency index (fsddm_cfar +(ndm-1)×N Δfd ) is determined to match the Doppler shift interval given to the PL1 polarization transmitting antenna during transmission, and in the PL1 polarization Doppler multiplexed signal reception level difference determination, the corresponding reception level difference is determined to be equal to or greater than the threshold, the condition of step B-2 is met.

[0351] If the conditions of step B-2 are met, the Doppler multiplexing separation unit 211 performs processing of step B-3, and if the conditions of step B-2 are not met, the Doppler multiplexing separation unit 211 may perform processing of step C-1, assuming that the signal includes a target reflected wave in which the PL1 polarization is cross-polarized relative to the polarization of the receiving antenna.

[0352] In addition, N PL1 If the number=1, the PL1 polarization Doppler shift interval match determination process does not need to be performed.

[0353] <Step B-3> The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with the lowest reception level N DM +δ-N PL1 Doppler frequency indexes and the top N highest received power PL1 Based on the relationship with the Doppler frequency indexes, the Doppler shift amounts DOP1, DOP2, ~, DOP Nt and the Doppler frequency index are associated with each other to obtain the separation index information DDM_RXindex_ PL1 (f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as the distance index f b_cfar At the same time, it outputs the result to the direction estimation unit 212.

[0354] where f demul_Tx#n denotes the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the n-th transmitting antenna (Tx#n).

[0355] Furthermore, the Doppler demultiplexing unit 211 outputs, for example, the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes to the direction estimation unit 212 .

[0356] The amount of Doppler shift applied to each transmitting antenna of the transmitting antenna unit 105 in the Doppler shift unit 104 of the radar transmitter 100 is known. PL1 (f b_cfar ) and the amount of Doppler shift applied to each transmitting antenna in the radar transmitter 100 is the Doppler frequency of the target. PL1 (f b_cfar ), the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) may be output to the direction estimation unit 212. In this case, the direction estimation unit 212 calculates the separation index information DDM_RXindex_ of the Doppler multiplexed signal based on the Doppler frequency of the target input from the Doppler multiplexing separation unit 211 and the amount of Doppler shift applied to each transmitting antenna in the Doppler shift unit 104 of the radar transmitter 100. PL1 (f b_cfar ), similar behavior can be achieved by generating

[0357] Alternatively, the Doppler demultiplexing unit 211 selects Nt transmitting antennas from which PL1 polarized waves are transmitted. PL1 The Doppler shift amount of the Doppler multiplexed signal from each transmitting antenna is associated with the Doppler frequency index, and the PL1 polarization separation index information of the Doppler multiplexed signal is stored as DDM_Rxindex_ PL1 (f b_cfar ) as the distance index f b_cfar At the same time, it may be output to the direction estimation unit 212.

[0358] <Step C-1> The Doppler demultiplexing unit 211 assumes that the PL1 polarization is a cross-polarized wave relative to the polarization of the receiving antenna and includes a target reflected wave. PL2 The Doppler multiplexed signals are subjected to Doppler demultiplexing processing.

[0359] <Step C-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indexes (f sddm_cfar +(ndm-1)×N Δfd ) and N from the PL2 polarized transmitting antenna PL2 It is assumed that the signal contains Doppler multiplexed signals.

[0360] The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd ))(For example, ndm=1~N DM +δ) and compare the top N received powers. PL2 Doppler frequency index f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval given to the PL2 polarization transmitting antenna during transmission (for example, this is called "PL2 polarization Doppler shift interval match determination").

[0361] Further, the Doppler demultiplexing unit 211 may demultiplex, for example, the top N signals of the received power. PL2 Doppler frequency indexes and the top N received powers PL2 Doppler frequency indexes (N DM +δ-N PL2 ) other Doppler frequency indexes, the difference (or the ratio of the reception levels) is determined to be significantly different (for example, whether the difference is equal to or greater than a threshold, or whether the ratio of the reception levels is equal to or greater than a threshold) (for example, this is called "PL2 polarization Doppler multiplexed signal reception level difference determination").

[0362] The Doppler demultiplexing unit 211 determines a Doppler frequency and a transmitting antenna in the range of -1 / (2Tr)≦fd<1 / (2Tr), for example, based on these determinations.

[0363] An example of the operation of the Doppler demultiplexing unit 211 that separates the Doppler multiplexed signals at unequal intervals is disclosed in, for example, Patent Document 7, and therefore detailed description of the operation will be omitted here.

[0364] For example, the Doppler demultiplexing unit 211 determines whether or not both the conditions for the PL2 polarization Doppler shift interval match determination and the PL2 polarization Doppler multiplexed signal reception level difference determination (for example, the condition in step C-2) are satisfied. PL2 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) is determined to match the Doppler shift interval given to the PL2 polarization transmitting antenna during transmission, and in the PL2 polarization Doppler multiplexed signal reception level difference determination, the corresponding reception level difference is determined to be equal to or greater than the threshold, the condition of step C-2 is met.

[0365] If the condition of step C-2 is satisfied, the Doppler demultiplexing unit 211 may perform the process of step C-3. If the condition of step C-2 is not satisfied, the Doppler demultiplexing unit 211 may determine that the received signal is a noise component or an interference component, and may not output the signal to the direction estimation unit 212 (step D).

[0366] In addition, N PL2 If the number=1, the PL2 polarization Doppler shift interval match determination process does not need to be performed.

[0367] <Step C-3> The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with the lowest reception level NDM +δ-N PL2 Doppler frequency indexes and the top N highest received power PL2 Based on the relationship with the Doppler frequency indexes, the Doppler shift amounts DOP1, DOP2, ~, DOP Nt and the Doppler frequency index are associated with each other to generate the separation index information DDM_Rxindex_ PL2 (f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as the distance index f b_cfar At the same time, it outputs the result to the direction estimation unit 212.

[0368] where f demul_Tx#n denotes the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the n-th transmitting antenna (Tx#n).

[0369] Furthermore, the Doppler demultiplexing unit 211 outputs, for example, the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes to the direction estimation unit 212 .

[0370] The amount of Doppler shift applied to each transmitting antenna of the transmitting antenna unit 105 in the Doppler shift unit 104 of the radar transmitter 100 is known. PL2 (f b_cfar ) and the amount of Doppler shift applied to each transmitting antenna in the radar transmitter 100 is the Doppler frequency of the target. PL2 (f b_cfar), the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) may be output to the direction estimation unit 212. In this case, the direction estimation unit 212 calculates the separation index information DDM_RXindex_ of the Doppler multiplexed signal based on the Doppler frequency of the target input from the Doppler multiplexing separation unit 211 and the amount of Doppler shift applied to each transmitting antenna in the Doppler shift unit 104 of the radar transmitter 100. PL2 (f b_cfar ), similar behavior can be achieved by generating

[0371] Furthermore, the Doppler demultiplexing unit 211 detects Nt of the Nt transmitting antennas from which the PL2 polarized waves are transmitted. PL2 The Doppler shift amount of the Doppler multiplexed signal from each transmitting antenna is associated with the Doppler frequency index, and the PL2 polarization separation index information of the Doppler multiplexed signal is stored as DDM_Rxindex_ PL2 (f b_cfar ) as the distance index f b_cfar At the same time, it may be output to the direction estimation unit 212.

[0372] An example of the operation of the Doppler demultiplexing unit 212 has been described above.

[0373] The distance index f input from the CFAR unit 210 b_cfar , the Doppler frequency index f sddm_cfar , and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd When there are a plurality of distance indexes, Doppler frequency indexes, and received power information, the Doppler demultiplexing unit 211 may perform the above-described Doppler demultiplexing operation a plurality of times for each distance index, Doppler frequency index, and received power information.

[0374] [Example of operation of direction estimation unit 212] Next, an example of the operation of the direction estimation unit 212 shown in FIG. 5 will be described.

[0375] In the following description, an example of operation of the direction estimation unit 212 will be described when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas with the same polarization. An example of operation of the direction estimation unit 212 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas with different polarizations will be described later.

[0376] The direction estimation unit 212 uses, for example, information input from the Doppler demultiplexing unit 211 (for example, a distance index f b_cfar , separation index information of Doppler multiplexed signal (DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt ) or DDM_Rxindex_ PLq (f b_cfar )) and the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes, where q=1 or 2, for example.

[0377] Hereinafter, operation example 1 and operation example 2 of the direction estimation unit 212 will be described.

[0378] <Operation Example 1 of Direction Estimation Unit 212> For example, the direction estimation unit 212 uses the distance index f b_cfar and the separation index information of the Doppler multiplexed signal DDM_Rxindex(f b_cfar ), the output of the Doppler analysis unit 209 is extracted, and the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )) and perform direction estimation processing.

[0379] The virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )) includes Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na, as shown in equation (10). The direction estimator 212 calculates the virtual receiving array correlation vector h(f b_cfar, DDM_Rxindex(f b_cfar )) is used to estimate the direction of the reflected wave signal from the target based on the phase difference between each transmitting and receiving antenna.

number

[0380] In equation (10), h cal[b] is an array correction value that corrects the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas, where b is an integer between 1 and (Nt × Na).

[0381] The direction estimation unit 212 performs direction estimation processing for each polarized transmitting antenna, for example, by using a virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )) and extract the received signals corresponding to the transmitting antennas of the same polarization.

[0382] For example, PL1 polarized wave transmitting antennas are Tx#1 and Tx#3, PL2 polarized wave transmitting antennas are Tx#2 and Tx#4, and N PL1 =2, N PL2 =2, N t = 4, and when the number of receiving antennas Na = 4, the transmitting polarization antenna extraction vector SP PL1 , and a transmit polarization antenna extraction vector SP for extracting a received signal corresponding to the PL2 polarized transmit antenna. PL2 is expressed as 16(=N t × Na) may be represented by the following column vector: where the superscript T denotes vector transpose:

number

number

[0383] The direction estimation unit 212 extracts, for example, a transmission polarization antenna extraction vector SPPL1 The virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )), extract the element components of the element index, arrange them in ascending order of the element index, and use the column vector as the virtual receiving array correlation vector h PL1 (f b_cfar , DDM_Rxindex(f b_cfar For example, the transmission polarization antenna extraction vector SP PL2 In this case, the elements at the first to fourth and ninth to twelfth element indexes are 1. In this case, the direction estimator 212 calculates the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )), extract the element components in the order of the 1st to 4th and 9th to 12th element indexes, and calculate the virtual receiving array correlation vector h PL1 (f b_cfar , DDM_Rxindex(f b_cfar )).

[0384] The direction estimation unit 212 also calculates, for example, a transmission polarization antenna extraction vector SP PL2 The virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )) and sort the element components of the element index in ascending order. The column vector is called the virtual receiving array correlation vector h PL2 (f b_cfar , DDM_Rxindex(f b_cfar )) where h PL1 (f b_cfar , DDM_Rxindex(f b_cfar )) is N PL1 ×Na elements, and PL2 (f b_cfar , DDM_Rxindex(f b_cfar)) is N PL2 ×Na elements. For example, the transmission polarization antenna extraction vector SP PL2 In this case, the elements at the 5th to 8th and 13th to 16th element indexes are 1. In this case, the direction estimator 212 calculates the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )), extract the element components in the order of the 5th to 8th and 13th to 16th element indexes, and calculate the virtual receiving array correlation vector h PL2 (f b_cfar , DDM_Rxindex(f b_cfar )).

[0385] The direction estimation unit 212 calculates, for example, a virtual receiving array correlation vector h PL1 (f b_cfar , DDM_Rxindex(f b_cfar )), and the virtual receiving array correlation vector h PL2 (f b_cfar , DDM_Rxindex(f b_cfar )) to obtain the direction estimation evaluation function P H-PLq (θ u , f b_cfar , DDM_Rxindex(f b_cfar )) azimuth direction θ u is varied within a predetermined angle range to calculate the spatial profile for each transmit polarization, where q=1 and 2.

[0386] The direction estimation unit 212 may extract a predetermined number of maximum peaks from the calculated spatial profile for each PLq polarization in descending order, and output the azimuth direction of the maximum peak as an estimated value of the direction of arrival of the PLq polarization (e.g., positioning output), where q=1 and 2.

[0387] The direction estimation evaluation function value P H-PLq (θ u , f b_cfar , DDM_Rxindex(f b_cfarThere are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0388] For example, if the number of virtual receiving antennas by the PLq polarized transmitting antenna is N PLq ×Na and arranged linearly at equal intervals dH, the beamformer method can be expressed as in the following equation (13). In addition to the beamformer method, methods such as Capon and MUSIC can also be applied.

number

[0389] In equation (13), the superscript H is the Hermitian transpose operator. PLq (θ u ) is the azimuth direction θ at the center frequency fc of the radar transmission signal u The direction vector of the virtual receiving array with PLq polarized transmitting antennas for the arriving wave of N is shown as equation (14). PLq ×Na. In equation (14), λ is the center frequency f c is the wavelength of the radar transmission signal (e.g., chirp signal) when λ = C0 / f c is.

number

[0390] Also, the azimuth direction θ u is a vector obtained by varying the azimuth range for estimating the direction of arrival at a predetermined azimuth interval β1. For example, θ u is set as follows: θ u =θ min + uβ1, integer u=0~ NU NU=floor[(θmax-θmin) / β1]+1 Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0391] In the above example, the direction estimation unit 212 calculates the azimuth direction as the direction of arrival estimate, but the present invention is not limited to this, and the direction of arrival can be estimated in the elevation direction, or in the azimuth direction and elevation direction by using MIMO antennas arranged in a rectangular grid. For example, the direction estimation unit 212 may calculate the azimuth direction and elevation direction as the direction of arrival estimate for each different polarized transmitting antenna, and output the calculated values ​​as the positioning output.

[0392] By the above operation, the direction estimation unit 212 of the radar device 10 outputs, for example, a distance index f b_cfar , separation index information of Doppler multiplexed signal DDM_Rxindex(f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) may output an estimated direction of arrival value for each different polarized wave transmitting antenna. The direction estimator 212 may further output a distance index f b_cfar , and the separation index information DDM_Rxindex(f b_cfar ) may be output.

[0393] Furthermore, the direction estimation unit 212 calculates, for example, the separation index information DDM_Rxindex(f b_cfar ), the target's Doppler frequency estimate may be output.

[0394] Also, the distance index f b_cfar may be converted into distance information using equation (1) and output.

[0395] In addition, information input from the Doppler demultiplexing unit 211 (for example, distance index f b_cfar , and the separation index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt)) are present, the direction estimator 212 may calculate estimated arrival directions for them in the same manner as in the above-described processing, and output the positioning results.

[0396] <Operation Example 2 of Direction Estimation Unit 212> For example, the direction estimation unit 212 uses the distance index f b_cfar and the separation index information of the Doppler multiplexed signal DDM_Rxindex_PLq(f b_cfar ), the output of the Doppler analysis unit 209 is extracted, and the virtual receiving array correlation vector h PLq (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) of the Doppler multiplexed signal and performs direction estimation processing. Here, q=1 or 2. The direction estimation unit 212 generates separation index information DDM_Rxindex_PLq(f b_cfar ) and performs direction estimation processing for the polarization (PLq polarization) corresponding to q that matches.

[0397] For example, the direction estimation unit 212 performs direction estimation processing based on a received signal corresponding to a radar transmission signal from a PLq polarization transmitting antenna, and therefore, a transmitting polarization antenna extraction vector SP PLq The virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex_PLq (f b_cfar )) and sort the element components of the element index in ascending order, and the column vector is called h PLq (f b_cfar , DDM_Rxindex_PLq (f b_cfar )) where h PLq (f b_cfar , DDM_Rxindex_PLq (f b_cfar )) is N PLq ×Na elements.

[0398] The direction estimation unit 212 calculates, for example, a virtual receiving array correlation vector h PLq (f b_cfar , DDM_Rxindex_PLq (f b_cfar )) to obtain the direction estimation evaluation function P H-PLq (θ u , f b_cfar , DDM_Rxindex_PLq (f b_cfar )) azimuth direction θ u is varied within a predetermined angle range to calculate the spatial profile for each transmit polarization, where q=1 or 2.

[0399] The direction estimation unit 212 may extract a predetermined number of maximum peaks in the spatial profile based on the calculated received signal corresponding to the PLq polarization transmitting antenna in descending order, and output the azimuth direction of the maximum peaks as an estimated value of the direction of arrival of the PLq polarization transmission (e.g., positioning output).

[0400] The direction estimation evaluation function value P H-PLq (θ u , f b_cfar , DDM_Rxindex_PLq (f b_cfar There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0401] In the above example, the direction estimation unit 212 calculates the azimuth direction as the direction of arrival estimate, but the present invention is not limited to this, and the direction of arrival can be estimated in the elevation direction, or in the azimuth direction and elevation direction by using MIMO antennas arranged in a rectangular grid. For example, the direction estimation unit 212 may calculate the azimuth direction and elevation direction as the direction of arrival estimate for each transmitting antenna of different polarization, and output the calculated values ​​as the positioning output.

[0402] By the above operation, the direction estimation unit 212 of the radar device 10 outputs, for example, a distance index f b_cfar , separation index information of Doppler multiplexed signal DDM_Rxindex_PLq(fb_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) based on the received signal from the PLq polarization transmitting antenna. b_cfar , and the separation index information DDM_Rxindex_PLq (f b_cfar ) may be output.

[0403] Furthermore, the direction estimation unit 212 calculates, for example, the separation index information DDM_Rxindex_PLq(f b_cfar ), the target's Doppler frequency estimate may be output.

[0404] Also, the distance index f b_cfar may be converted into distance information using equation (1) and output.

[0405] In addition, information input from the Doppler demultiplexing unit 211 (for example, distance index f b_cfar , and the separation index information DDM_Rxindex_PLq(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt )) are present, the direction estimator 212 may calculate estimated arrival directions for them in the same manner as in the above-described processing, and output the positioning results.

[0406] Operation example 1 and operation example 2 of the direction estimation unit 212 have been described above.

[0407] By the above-described operation, the direction estimation unit 212 can perform direction estimation processing based on the output corresponding to the separation operation of the Doppler demultiplexing unit 211. For example, the direction estimation unit 212 can perform direction estimation processing based on the output of the Doppler demultiplexing unit 211 corresponding to each of the following cases: when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is not included, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included in PL2, and when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included in PL1.

[0408] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is not included, the direction estimation unit 212 can perform direction estimation processing for each polarization included in the transmitting antenna. Also, for example, when a target reflected wave in PL2 that is cross-polarized with respect to the polarization of the receiving antenna is included, the direction estimation unit 212 can perform direction estimation processing for PL1 polarized wave transmission. Also, for example, when a target reflected wave in PL1 that is cross-polarized with respect to the polarization of the receiving antenna is included, the direction estimation unit 212 can perform direction estimation processing for PL2 polarized wave transmission.

[0409] Such operation of the direction estimation unit 212 obtains a direction estimation process result for each transmission polarization, or a direction estimation result for some transmission polarization depending on the state of the reflected waves, thereby obtaining a direction estimation result that depends on the transmission polarization. Because the response of the reflected wave from the target can vary depending on the transmission polarization, the radar device 10 can improve the target detection performance or identification performance based on such a direction estimation result that depends on the transmission polarization.

[0410] An example of the operation of the direction estimation unit has been described above.

[0411] As described above, in the present embodiment, the radar device 10 is a polarized MIMO radar using uneven Doppler multiplexing, and when using transmitting antennas of different polarizations, even when receiving reflected waves in which the reception level of reflected waves from a transmitting antenna of one polarization is significantly attenuated compared to the reception level of reflected waves from a transmitting antenna of another polarization, the radar device 10 is able to perform Doppler demultiplexing, thereby suppressing deterioration of target detection performance, erroneous estimation of Doppler frequency, or deterioration of angle measurement performance.

[0412] For example, when the above-mentioned conditions 1 and 2 are satisfied, the detectable Doppler frequency range fd of the radar device 10 is -1 / (2Tr)≦fd < 1 / (2Tr), which is wider than the detectable Doppler frequency range -1 / (2Nt×Tr)≦fd < 1 / (2Nt×Tr) in equal-interval Doppler multiplexing.

[0413] Therefore, according to this embodiment, it is possible to improve the detection performance of a polarized MIMO radar using non-uniform Doppler multiplexing transmission.

[0414] In this embodiment, the radar device 10 includes a receiving antenna that receives a reflected wave signal, which is a radar transmission signal reflected by a target, using one of a plurality of polarized waves (e.g., PL1 polarization and PL2 polarization). The radar device 10 then performs direction estimation based on the reflected wave signal received by the receiving antenna. This allows the radar device 10 to identify the transmitting antenna corresponding to the Doppler multiplexed signal, even when the signal includes a reflected wave that is cross-polarized with the polarization of the receiving antenna, thereby resolving the ambiguity of the Doppler frequency. In this embodiment, Doppler demultiplexing is possible even if the receiving antennas are identically polarized, so there is no need to additionally use different types of polarized receiving antennas in the radar receiver 200, and the number of receiving antennas can be reduced.

[0415] (First Modification of First Embodiment) In the embodiment, an example of the operation of the CFAR unit 210, the Doppler demultiplexing unit 211, and the direction estimation unit 212 when the multiple receiving antennas of the receiving antenna unit 202 are receiving antennas of the same polarization has been described.

[0416] The multiple receiving antennas of the receiving antenna unit 202 may include receiving antennas of different polarizations. In Modification 1 of Embodiment 1, an example of the operation of the CFAR unit, Doppler demultiplexing unit, and direction estimation unit when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations will be described.

[0417] For example, if the multiple receiving antennas include receiving antennas with different polarizations, the reception levels of the target reflected waves may differ significantly for each of the different polarizations. For this reason, for example, the radar device 10 may perform CFAR processing, Doppler separation processing, and direction estimation processing separately for the outputs of the Doppler analyzers 209 corresponding to the receiving antennas with different polarizations.

[0418] The direction estimation process may be performed using the output of Doppler separation processing using a plurality of polarized wave receiving antennas.

[0419] In the following, as an example, a case will be described in which the receiving antennas Rx#1 to Rx#Na of the receiving antenna section 202 include receiving antennas of at least two different polarized waves.

[0420] For example, two different polarized waves are expressed as "RxPL1 polarized wave" and "RxPL2 polarized wave." Furthermore, among the Na receiving antennas, the number of receiving antennas for RxPL1 polarized wave is expressed as N RxPL1 The number of RxPL2 polarized receiving antennas is N RxPL2 Here, N RxPL1 +N RxPL2 =Na.

[0421] FIG. 18 is a block diagram showing an example configuration of a CFAR unit 210a, a Doppler demultiplexing unit 211a, and a direction estimating unit 212a of a radar receiving unit 200a in the radar device 10 according to the first modification of the first embodiment.

[0422] In FIG. 18, as an example, receiving antennas Rx#1 to Rx#N RxPL1 is the RxPL1 polarized receiving antenna, and Rx#N RxPL1 +1 to Rx#Na are RxPL2 polarized wave receiving antennas. Note that the relationship between the receiving antenna numbers and the polarized waves is not limited to the example shown in FIG.

[0423] Furthermore, as shown in FIG. 18, Doppler demultiplexing is possible using the peak detection results for each receiving antenna of the same polarization, and power addition calculations between receiving antennas of two different polarizations do not need to be performed, which reduces the amount of calculations in the radar receiving unit 200a.

[0424] For example, among the outputs of Na Doppler analyzers 209, the first to Nth RxPL1 The output of the Doppler analysis unit 209 corresponds to the received signal of the RxPL1 polarized wave receiving antenna, and is input to a first CFAR unit 210a-1 that performs CFAR processing on the received signal of the RxPL1 polarized wave.

[0425] Also, for example, among the outputs of the Na Doppler analyzers 209, the Rx#N RxPL1 The outputs of +1 to Na-th Doppler analyzers 209 correspond to the received signals of the RxPL2 polarized wave receiving antenna, and are input to a second CFAR unit 210a-2 that performs CFAR processing on the RxPL2 polarized wave received signals.

[0426] The operation of the first CFAR unit 210a-1 is, for example, the first to Nth CFAR units 210a-1, as compared with the CFAR unit 210 of FIG. RxPL1 The difference is that the output of the Doppler analysis unit 209 is input to the first CFAR unit 210a-1, and that the power sum is calculated using the following equation (15) instead of equation (9). Other operations may be the same as those of the CFAR unit 210 described above.

number

[0427] The operation of the second CFAR section 210a-2 is, for example, N-th compared to the CFAR section 210 of FIG. RxPL1 The difference is that the outputs of +1 to Nath Doppler analysis units 209 are input to the second CFAR unit 210a-2, and that the power sum is calculated using the following equation (16) instead of equation (9); other operations may be the same as those of the CFAR unit 210 described above.

number

[0428] For example, when δ shown in equation (3) is set to a positive integer, the first Doppler demultiplexing unit 211a-1 demultiplexes the distance index f b_cfar , the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ), and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) based on which the Doppler multiplexed signal is separated from the received signal of the RxPL1 polarized wave receiving antenna. DM +δ is an integer. The operation of first Doppler demultiplexing section 211a-1 differs from Doppler demultiplexing section 211 in FIG. 5 in that it uses received power information based on equation (15), but other operations may be similar to those of Doppler demultiplexing section 211.

[0429] For example, when δ shown in equation (3) is set to a positive integer, the second Doppler demultiplexing unit 211a-2 demultiplexes the distance index f b_cfar , the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ), and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd)) based on which the Doppler multiplexed signal is separated from the received signal of the RxPL2 polarized wave receiving antenna. DM +δ is an integer. The second Doppler demultiplexing unit 211a-2 differs from the Doppler demultiplexing unit 211 in FIG. 5 in that it uses received power information based on equation (16), but other operations may be similar to those of the Doppler demultiplexing unit 211.

[0430] Next, an example of the operation of the first direction estimation unit 212a-1 and the second direction estimation unit 212a-2 will be described.

[0431] In the following description, the first direction estimation unit 212a-1 and the second direction estimation unit 212a-2 will be collectively referred to as the "y-th direction estimation unit 212a," where y=1 or 2.

[0432] The y-th direction estimation unit 212a uses, for example, information input from the y-th Doppler demultiplexing unit 211a (for example, a distance index f b_cfar , and the separation index information of the Doppler multiplexed signal (DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt ) or DDM_Rxindex_ PLq (f b_cfar ), and the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes, where q=1 or 2, is used to perform target direction estimation processing.

[0433] Hereinafter, operation example 1 and operation example 2 of the y-direction estimation unit 212a will be described.

[0434] <Operation Example 1 of the y-direction estimation unit 212a> For example, the y-th direction estimation unit 212a uses the distance index f b_cfar and the separation index information of the Doppler multiplexed signal DDM_Rxindex(f b_cfar), the output of the Doppler analysis unit 209 is extracted, and the virtual receiving array correlation vector h of the y-th direction estimation unit 212a is calculated as shown in the following equations (17) and (18). RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is generated and direction estimation processing is performed, where y=1 or 2.

[0435] The virtual receiving array correlation vector h RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is expressed as the number of transmitting antennas Nt and the number of receiving antennas N for RxPLy polarization, as shown in Equation (17) and Equation (18). RxPLy The product of Nt×N RxPLy The y-th direction estimation unit 212a calculates the virtual receiving array correlation vector h RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is used to estimate the direction of the reflected wave signal from the target based on the phase difference between each transmitting and receiving antenna.

number

number

[0436] In equation (17), h calRxPL1[bRxPL1] is the array correction value that corrects the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas. bRxPL1=1~(Nt×N RxPL1 ) is an integer. Also, in equation (18), h calRxPL2[bRxPL2] is the array correction value that corrects the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas. bRxPL2=1~(Nt×N RxPL2 ) is an integer.

[0437] The y-th direction estimation unit 212a performs direction estimation processing for each polarized transmitting antenna, for example, by using a virtual receiving array correlation vector h RxPLy (f b_cfar, DDM_Rxindex(f b_cfar )), the received signal corresponding to the transmitting antenna of the same polarization is extracted. For the extraction, the following operation is performed. For example, the y-th direction estimation unit 212a extracts the transmitting polarization antenna extraction vector SP PL1,RxPLy The virtual receiving array correlation vector h RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )), extract the element components of the element index, arrange them in ascending order of the element index, and use the column vector as the virtual receiving array correlation vector h PL1, RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) and the y-direction estimation unit 212a generates a transmission polarization antenna extraction vector SP PL2,RxPLy The virtual receiving array correlation vector h RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )), and the column vectors arranged in ascending order of element index are used as the virtual receiving array correlation vector h PL2, RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) where h PL1, RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is N PL1 ×N RxPLy is a column vector with elements, and h PL2, RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is N PL2 ×N RxPLy is a column vector with elements.

[0438] Here, the transmit polarization antenna extraction vector SP extracts the received signal of the receive antenna of RxPLy polarization corresponding to the transmit signal transmitted from the transmit antenna of PLq polarization. PLq,RxPLy is set based on the polarization of each transmit and receive antenna.

[0439] For example, PL1 polarized wave transmitting antennas are Tx#1 and Tx#3, PL2 polarized wave transmitting antennas are Tx#2 and Tx#4, and N PL1 =2, N PL2 =2, N t = 4, and the number of receiving antennas Na = 4, N RxPL1 =2, N RxPL2 = 2, the case where the RxPL1 polarized wave receiving antennas are Rx#1 and Rx#2 and the RxPL2 polarized wave receiving antennas are Rx#3 and Rx#4 will be described.

[0440] In this case, the transmit polarization antenna extraction vector SP that extracts the receive signal corresponding to the PL1 polarized transmit antenna from the receive signal of the RxPL1 polarized receive antenna is PL1, RxPL1 , and a transmit polarization antenna extraction vector SP that extracts the receive signal corresponding to the PL2 polarized transmit antenna from the receive signal of the RxPL1 polarized receive antenna. PL2, RxPL1 is expressed as 16(=N t ×Na) column vector. Also, a transmission polarization antenna extraction vector SP PL1, RxPL2 , and a transmit polarization antenna extraction vector SP that extracts the receive signal corresponding to the PL2 polarized transmit antenna from the receive signal of the RxPL2 polarized receive antenna. PL2, RxPL2 is expressed as 16(=N t × Na) may be represented by the following column vector: where the superscript T denotes vector transpose:

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number

number

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[0441] The y-th direction estimation unit 212a estimates, for example, the virtual receiving array correlation vector h PL1, RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) and the virtual receiving array correlation vector h with PL2 polarized transmitting antenna PL2, RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) to obtain the direction estimation evaluation function P H-PLq, RxPLy (θ u , f b_cfar , DDM_Rxindex(f b_cfar )) azimuth direction θ u is varied within a predetermined angle range to calculate the spatial profile for each transmit polarization, where q=1 and 2.

[0442] The y-direction estimation unit 212a may extract a predetermined number of maximum peaks from the calculated spatial profile for each PLq polarization in descending order, and output the azimuth direction of the maximum peaks as an arrival direction estimate (e.g., positioning output) for each PLq polarization by the receiving antenna of the RxPLy polarization, where q=1 and 2.

[0443] The direction estimation evaluation function value P H-PLq, RxPL1 (θ u , f b_cfar , DDM_Rxindex(f b_cfar There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0444] For example, if the number of virtual receiving antennas by the PLq polarized transmitting antenna is N PLq ×N RxPL1When the number of antennas is equal and they are arranged in a line at equal intervals dH, the beamformer method can be expressed as in the following equation (23): In addition to the beamformer method, methods such as Capon and MUSIC can also be applied.

number

[0445] In equation (23), the superscript H is the Hermitian transpose operator. PLq,RxPLy (θ u ) is the azimuth direction θ at the center frequency fc of the radar transmission signal u The direction vector of the virtual receiving array consisting of PLq polarized transmitting antennas and RxPLy polarized receiving antennas for the arriving wave of N PLq ×N RxPLy In equation (24), λ is the center frequency f c is the wavelength of the radar transmission signal (e.g., chirp signal) when λ = C0 / f c is.

number

[0446] Also, the azimuth direction θ u is a vector obtained by varying the azimuth range for estimating the direction of arrival at a predetermined azimuth interval β1. For example, θ u is set as follows: θ u =θ min + uβ1, integer u=0~ NU NU=floor[(θmax-θmin) / β1]+1 Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0447] In the above example, the y-th direction estimator 212a calculates the azimuth direction as the direction-of-arrival estimated value, but the present invention is not limited to this, and the direction-of-arrival estimation can be performed in the elevation direction, or by using MIMO antennas arranged in a rectangular grid, the direction-of-arrival estimation can be performed in the azimuth direction and the elevation direction. For example, the y-th direction estimator 212a may calculate the azimuth direction and the elevation direction as the direction-of-arrival estimated value by the RxPLy polarization receiving antenna for each different polarization transmitting antenna, and output the calculated values ​​as the positioning output.

[0448] Through the above operation, the y-th direction estimation unit 212a receives, as a positioning output, for example, a distance index f b_cfar , separation index information of Doppler multiplexed signal DDM_Rxindex(f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) for each different polarized transmitting antenna in the y-th direction estimation unit 212a, the y-th direction estimation unit 212a may output an arrival direction estimate value by the RxPLy polarized receiving antenna. b_cfar , separation index information of Doppler multiplexed signal DDM_Rxindex(f b_cfar ) may be output.

[0449] Furthermore, the y-direction estimation unit 212a may, for example, calculate the separation index information DDM_Rxindex(f b_cfar ), the target's Doppler frequency estimate may be output.

[0450] Also, the distance index f b_cfar may be converted into distance information using equation (1) and output.

[0451] In addition, information input from the y-th Doppler demultiplexing unit 211a (for example, distance index f b_cfar , and the separation index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt)) are present, the y-th direction estimation unit 212a may calculate arrival direction estimation values ​​for them in the same manner as in the above-described lower process, and output the positioning results.

[0452] <Operation Example 2 of the y-direction estimation unit 212a> For example, the y-th direction estimation unit 212a estimates the distance index f b_cfar and the separation index information of the Doppler multiplexed signal DDM_Rxindex_PLq(f b_cfar ) and extracts the output of the Doppler analysis unit 209, and calculates the virtual receiving array correlation vector h PLq , RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) and performs direction estimation processing. Here, q=1 or 2. The y-th direction estimation unit 212a generates separation index information DDM_Rxindex_PLq(f b_cfar ) and performs direction estimation processing for the polarization (PLq polarization) corresponding to q that matches.

[0453] For example, the y-direction estimation unit 212a performs direction estimation processing based on the received signal received by the RxPLy polarized wave receiving antenna, which corresponds to the radar transmission signal from the PLq polarized wave transmitting antenna, and therefore, extracts the received signal corresponding to the PLq polarized wave transmitting antenna by using a transmitting polarization antenna extraction vector SP PLq,RxPLy The virtual receiving array correlation vector h RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) (for example, from equation (17) or equation (18)), the element components of the element index are extracted, and the column vectors arranged in ascending order of the element index are used as the virtual receiving array correlation vector h PLq,RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )), where h PLq, RxPLy (f b_cfar , DDM_Rxindex_PLq(fb_cfar )) is N PLq ×N RxPLy is a column vector with elements.

[0454] The y-direction estimation unit 212a calculates a virtual receiving array correlation vector h PLq, RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) to obtain the direction estimation evaluation function P H-PLq,RxPLy (θ u , f b_cfar , DDM_Rxindex_PLq(f b_cfar )) azimuth direction θ u is varied within a predetermined angle range to calculate the spatial profile of the PLq transmission polarization, where q=1 or 2.

[0455] The y-direction estimation unit 212a may extract a predetermined number of maximum peaks of the spatial profile based on the calculated received signal corresponding to the PLq polarization transmitting antenna in descending order, and output the azimuth direction of the maximum peak as a direction of arrival estimate value (e.g., positioning output) when PLq polarization is transmitted and RxPLy polarization is received.

[0456] The direction estimation evaluation function value P H-PLq,RxPLy (θ u , f b_cfar , DDM_Rxindex_PLq(f b_cfar There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0457] In the above example, the y-th direction estimator 212a calculates the azimuth direction as the direction-of-arrival estimated value, but the present invention is not limited to this, and estimation of the direction of arrival in the elevation angle direction, or estimation of the direction of arrival in the azimuth direction and elevation angle direction by using MIMO antennas arranged in a rectangular grid, is also possible. For example, the y-th direction estimator 212a may calculate the azimuth direction and elevation angle direction as the direction-of-arrival estimated value by the RxPLy polarized receiving antenna for each transmitting antenna of different polarization, and use them as the positioning output.

[0458] By the above operation, the y-th direction estimation unit 212a estimates, for example, the distance index f b_cfar , separation index information of Doppler multiplexed signal DDM_Rxindex_PLq(f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) based on the received signal from the PLq polarized wave transmitting antenna in the y direction estimation unit 212a, the y direction estimation unit 212a may output, as a positioning output, an estimated value of the direction of arrival by the RxPLy polarized wave receiving antenna for the PLq polarized wave transmission. b_cfar , separation index information of Doppler multiplexed signal DDM_Rxindex_PLq (f b_cfar ) may be output.

[0459] Furthermore, the direction estimation unit 212a calculates, for example, the separation index information DDM_Rxindex_PLq(f b_cfar ), the target's Doppler frequency estimate may be output.

[0460] Also, the distance index f b_cfar may be converted into distance information using equation (1) and output.

[0461] In addition, information input from the Doppler demultiplexing unit 211 (for example, distance index f b_cfar , and the separation index information DDM_Rxindex_PLq(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2,~,f demul_Tx#Nt )) are present, the y-th direction estimation unit 212a may calculate arrival direction estimation values ​​for them in the same manner as in the above-described processing, and output the positioning results.

[0462] The first and second operation examples of the y-direction estimation unit 212a have been described above.

[0463] By performing the above-described operations, the y-th direction estimation unit 212a can obtain the result of direction estimation processing by the RxPLy polarized receiving antenna for each transmitted polarized wave, or the result of direction estimation by the RxPLy polarized receiving antenna for some transmitted polarized waves depending on the state of reflected waves, and can obtain a direction estimation result that depends on the transmitted polarized antenna and the received polarized antenna. Because the response of the reflected wave from the target can vary depending on the transmitted polarized wave and the received polarized wave, the radar device 10 can improve the target detection performance or identification performance based on the direction estimation result that depends on the transmitted and received polarized waves.

[0464] Here, the y-th direction estimation unit 212a uses information input from the y-th Doppler demultiplexing unit 211a (for example, distance index f b_cfar , and the separation index information of the Doppler multiplexed signal (DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt ) or DDM_Rxindex_ PLq (f b_cfar )) and the case where the target direction estimation process is performed based on the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes has been described, but the present invention is not limited to this.

[0465] For example, the y-direction estimation unit 212a receives information (for example, a distance index f b_cfar , and the separation index information of the Doppler multiplexed signal (DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt ) or DDM_Rxindex_PLq (f b_cfar )), the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes, and information input from the second Doppler multiplex separation unit 211a-2 (for example, distance index f b_cfar , and the separation index information of the Doppler multiplexed signal (DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt ) or DDM_Rxindex_ PLq (f b_cfar )) and the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes, the direction of the target may be estimated.

[0466] For example, the y-direction estimation unit 212a uses information input from the first Doppler demultiplexing unit 211a-1 to calculate a virtual receiving array correlation vector h PL1, RxPL1 (f b_cfar , DDM_Rxindex(f b_cfar )) using the information input from the second Doppler demultiplexing unit 211a-2. The y-direction estimator 212a also calculates a virtual receiving array correlation vector h PL2, RxPL2 (f b_cfar , DDM_Rxindex(f b_cfar Then, the y-th direction estimation unit 212a calculates the virtual receiving array correlation vector h PL1, RxPL1 (f b_cfar , DDM_Rxindex(f b_cfar )) and the virtual receiving array correlation vector h PL2, RxPL2 (f b_cfar , DDM_Rxindex(f b_cfar )) may be used to perform target direction estimation processing.

[0467] Alternatively, for example, the y-direction estimation unit 212a may use information input from the first Doppler demultiplexing unit 211a-1 to calculate a virtual receiving array correlation vector h PL2, RxPL1 (f b_cfar , DDM_Rxindex(f b_cfar )) using the information input from the second Doppler demultiplexing unit 211a-2. The y-direction estimating unit 212a also calculates a virtual receiving array correlation vector h PL1, RxPL2 (f b_cfar , DDM_Rxindex(f b_cfar Then, the y-th direction estimation unit 212a calculates the virtual receiving array correlation vector h PL2, RxPL1 (f b_cfar , DDM_Rxindex(f b_cfar )) and h PL1, RxPL2 (f b_cfar , DDM_Rxindex(f b_cfar )) may be used to perform target direction estimation processing.

[0468] (Modification 2 of Embodiment 1) In the first embodiment, an operation has been described in which the Doppler multiplexed signals are transmitted at uneven intervals using the Nt transmitting antennas of the transmitting antenna unit 105, and the Doppler multiplexed signals to which the Doppler shift amount is added by the Doppler shift unit 104 are simultaneously multiplexed and transmitted from the Nt transmitting antennas using Doppler multiplexing (DDM) that satisfies conditions 1 and 2, but the present invention is not limited to this.

[0469] In a second modification of the first embodiment, for example, the Doppler multiplexed signals are transmitted using the Nt transmitting antennas of the transmitting antenna unit 105 in an unequally spaced Doppler multiplexed manner, and the Doppler multiplexed signals to which the Doppler shift amount is added by the Doppler shift unit 104 may be simultaneously multiplexed and transmitted from the Nt transmitting antennas using Doppler multiplexing (DDM) that does not satisfy the condition 1 but satisfies the condition 2.

[0470] By setting the amount of Doppler shift in the Doppler shifter 104 in this way, for example, the operation of <Step B-1> or <Step C-1> in the Doppler demultiplexer 211 includes a Doppler demultiplexing operation of equally spaced Doppler multiplexed signals.

[0471] Here, if the Doppler frequency range of the assumed target is within the detectable Doppler frequency range described below, the radar device 10 can separate the Doppler multiplexed signal by the existing operation of separating the equally spaced Doppler multiplexed signal.

[0472] For example, the following three cases are examples of cases in which the Doppler multiplexed signal to which the Doppler shift amount is added by the Doppler shift unit 104 does not satisfy Condition 1.

[0473] (Case 1) In the case of equally spaced Doppler multiplexing in both PL1 and PL2 polarizations (however, N PL1 ≧2, N PL2 ≧2). In this case, the detectable Doppler frequency range fd is -1 / (2 max(N PL1 , N PL2 )Tr)≦fd < 1 / (2 max(N PL1 , N PL2 )Tr), where max(N PL1 , N PL2 ) is N PL1 and N PL2 This function returns the largest value of N PL1 and N PL2 are equal, either value may be output).

[0474] (Case 2) In the case where PL1 polarization is non-uniform Doppler multiplexing and PL2 polarization is uniform Doppler multiplexing (however, N PL1 ≧2, N PL2 ≧2). In this case, the detectable Doppler frequency range fd is -1 / (2 N PL2 Tr)≦fd < 1 / (2 N PL2 Tr).

[0475] (Case 3) In the case where PL1 polarization is Doppler multiplexed at equal intervals and PL2 polarization is Doppler multiplexed at unequal intervals (however, N PL1 ≧2, N PL2 ≧2). In this case, the detectable Doppler frequency range fd is -1 / (2 N PL1 Tr)≦fd < 1 / (2 N PL1 Tr ).

[0476] For example, when conditions 1 and 2 are satisfied, the Doppler frequency range fd of a detectable target is -1 / (2Tr)≦fd<1 / (2Tr). On the other hand, when condition 2 is satisfied, the Doppler frequency range fd of a detectable target is narrower than when conditions 1 and 2 are satisfied, but in all of cases 1 to 3, the Doppler detectable range can be expanded beyond the Doppler detection range in existing equal-interval Doppler multiplexing, which is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr).

[0477] In this way, by using Doppler multiplexing (DDM) that satisfies condition 2, it is possible to obtain the same effects as in embodiment 1. For example, in a polarized MIMO radar that uses uneven Doppler multiplexing, when transmitting antennas of different polarizations are used, even in a situation where reflected waves are received in which the received level of a reflected wave from a transmitting antenna of one polarization is significantly attenuated compared to the received level of a reflected wave from a transmitting antenna of another polarization, the radar device 10 can perform Doppler demultiplexing, and can suppress deterioration of target detection performance, erroneous estimation of Doppler frequency, or deterioration of angle measurement performance.

[0478] An example of setting the amount of Doppler shift in the Doppler shifter 104 in the second modification will be described below.

[0479] <Doppler shift amount setting example 7> In setting example 7, a case will be described in which uneven Doppler multiplexing is performed for PL1 polarization and equal Doppler multiplexing is performed for PL2 polarization.

[0480] Figure 19 shows the number of transmit antennas, Nt=4, N PL1 =2, N PL2 19 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .gtoreq.2. In FIG. 19, Tx#1 and Tx#3 are PL1 polarized wave transmission antennas, and Tx#2 and Tx#4 are PL2 polarized wave transmission antennas.

[0481] In the seventh example of setting the amount of Doppler shift, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (6Tr) and δ=2, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0482] In the example shown in FIG. 19, the first to fourth Doppler shift sections 104 (or the Doppler shift sections 104-1 to 104-4) may perform the following operations.

[0483] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0484] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-2π(m-1) / 3 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-1 / (3Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0485] The third Doppler shift unit 104 applies a phase rotation Φ3(m)=-π(m-1) / 3 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP3=-1 / (6Tr) to the third transmitting antenna Tx#3, and outputs the result.

[0486] The fourth Doppler shift unit 104 applies a phase rotation Φ4(m)=π(m-1) / 3 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=1 / (6Tr) to the fourth transmitting antenna Tx#4, and outputs the result.

[0487] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0488] In FIG. 19, the interval between the amounts of Doppler shift (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#4 is Δfd (1, 2) =Δfd (2, 3) =Δfd, Δfd (3, 4) =Δfd (4, 1) Therefore, in FIG. 19, the intervals of the Doppler shift amounts given to the four transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (1, 2) =Δfd (2, 3) ≠Δfd (3, 4) =Δfd (4, 1) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0489] In addition, in FIG. 19, the interval of the Doppler shift amount between the transmitting antennas Tx#1 and Tx#3, which are PL1 polarized waves, is Δfd (1, 3) =2Δfd, Δfd (3, 1) = 4Δfd. Therefore, the number of PL1 polarized transmitting antennas N PL1 The intervals of the Doppler shifts given to each of the PL1 polarization transmitting antennas of =2 are not all the same interval, but include unequal intervals (Δfd (1, 3) ≠Δfd (3, 1) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed using a PL1 polarized transmitting antenna.

[0490] In addition, in FIG. 19, the interval of the Doppler shift amount (Doppler shift interval) between the transmitting antennas Tx#2 and Tx#4, which are the PL2 polarized waves, is Δfd (2, 4)=3Δfd, Δfd (4, 2) = 3Δfd. Therefore, the number of PL2 polarized transmitting antennas N PL2 Since the intervals of the Doppler shifts given to each of the PL2 polarization transmitting antennas of =2 are all the same (Δfd (2, 4) =Δfd (4, 2) ), and uniformly spaced Doppler multiplexed transmission (uniformly spaced DDM transmission) using a PL2 polarized transmitting antenna.

[0491] From the above, the example shown in FIG. 19 is an example of setting a pattern of the amount of Doppler shift that does not satisfy condition 1.

[0492] In addition, in FIG. 19, the interval of the Doppler shift amount between the PL1 polarization transmitting antennas Tx#1 and Tx#3 is Δfd (1, 3) =2Δfd, Δfd (3, 1) = 4Δfd, and the interval of the Doppler shift amount between the PL2 polarization transmitting antennas Tx#2 and Tx#4 is Δfd (2, 4) =Δfd (4, 2) =3Δfd. Therefore, the amount of Doppler shift between the PL1 polarization transmitting antennas Tx#1 and Tx#3 and the amount of Doppler shift between the PL2 polarization transmitting antennas Tx#2 and Tx#4 include different Doppler shift intervals.

[0493] For example, the interval between the Doppler shift amounts between PL1 polarized transmitting antennas Tx#1 and Tx#3 includes 2Δfd and 4Δfd, but the interval between the Doppler shift amounts between PL2 polarized transmitting antennas Tx#2 and Tx#4 does not include 2Δfd and 4Δfd.

[0494] Also, for example, the maximum DDM interval of the Doppler shift amount between PL2 polarization transmitting antennas Tx#2 and Tx#4 is 3Δfd, but the interval of the Doppler shift amount between PL1 polarization transmitting antennas Tx#1 and Tx#3 does not include 3Δfd.

[0495] As described above, in the example shown in FIG. 19, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0496] From the above, the example shown in FIG. 19 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2(1).

[0497] For example, if the radar device 10 does not include target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas, the radar device 10 receives signals corresponding to the PL1 polarization transmitting antennas (Tx#1 and Tx#3) and the PL2 polarization transmitting antennas (Tx#2 and Tx#4) at approximately the same level. Here, signals transmitted from the Nt transmitting antennas Tx#1 to Tx#4, which are made up of the PL1 polarization transmitting antennas and the PL2 polarization transmitting antennas, are Doppler-multiplexed and transmitted using Doppler shift intervals that result in uneven interval Doppler multiplexing. Therefore, the radar device 10 (e.g., the Doppler demultiplexing unit 211) can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of a Doppler-multiplexed signal.

[0498] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd < 1 / (2Tr), and obtain outputs that correspond to the transmitting antennas for each Doppler multiplexed signal.

[0499] Furthermore, when a target reflected wave that is cross-polarized relative to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 2 (1)) depending on whether the PL1 polarization includes a target reflected wave that is cross-polarized or the PL2 polarization includes a target reflected wave that is cross-polarized.

[0500] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0501] This enables the radar device 10 to determine in the Doppler demultiplexing unit 211, for example, based on the detected Doppler frequency peaks (e.g., the interval between peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization transmitting antenna or a decrease in the reception level of the reception signal corresponding to the PL2 polarization transmitting antenna has occurred.

[0502] For example, the PL1 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval resulting in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing separation unit 211 determines that the received signal corresponds to a signal transmitted by a PL1 polarized transmitting antenna, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr) using an existing Doppler multiplexed signal separation operation, and can separate the Doppler multiplexed signal and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0503] Furthermore, for example, the PL2 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in equal-interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexer 211 determines that the received signal corresponds to a signal transmitted by a PL2 polarized transmitting antenna, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (4Tr)≦fd<1 / (4Tr), and can obtain outputs that associate the transmitting antennas with each Doppler multiplexed signal.

[0504] By such an operation of the Doppler multiplexing separation unit 211, the radar device 10 can determine the Doppler frequency fd of the target and obtain outputs that associate the transmitting antennas with the respective Doppler multiplexed signals.

[0505] <Doppler shift amount setting example 8> In setting example 8, a case will be described in which uniform Doppler multiplexing is performed for PL1 polarization and non-uniform Doppler multiplexing is performed for PL2 polarization.

[0506] Figure 20 shows the number of transmit antennas, Nt=4, N PL1 =2, N PL2 20 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when .gtoreq.2. In FIG. 20, Tx#1 and Tx#3 are PL1 polarized wave transmission antennas, and Tx#2 and Tx#4 are PL2 polarized wave transmission antennas.

[0507] In the eighth example of setting the amount of Doppler shift, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (6Tr) and δ=2, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0508] In the example shown in FIG. 20, the first to fourth Doppler shift sections 104 (or the Doppler shift sections 104-1 to 104-4) may perform the following operations.

[0509] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0510] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-2π(m-1) / 3 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-1 / (3Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0511] The third Doppler shift unit 104 imparts a phase rotation Φ3(m)=0 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP3=0 to the third transmitting antenna Tx#3, and outputs the result.

[0512] The fourth Doppler shift unit 104 applies a phase rotation Φ4(m)=2π(m-1) / 3 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=1 / (3Tr) to the fourth transmitting antenna Tx#4, and outputs the result.

[0513] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0514] In FIG. 20, the interval between the Doppler shift amounts (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#4 is Δfd (1, 2) =Δfd (4, 1) =Δfd, Δfd (2, 3) =Δfd (3, 4) Therefore, in FIG. 20, the intervals of the Doppler shift amounts given to the four transmitting antennas Nt are not all the same, but include unequal intervals (for example, Δfd (1, 2) =Δfd (4, 1) ≠Δfd (2, 3) =Δfd (3, 4) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0515] In addition, in FIG. 20, the interval of the Doppler shift amount (Doppler shift interval) between the transmitting antennas Tx#1 and Tx#3 that are PL1 polarized waves is Δfd (1, 3) =3Δfd, Δfd (3, 1) = 3Δfd. Therefore, the number of PL1 polarized transmitting antennas N PL1 Since the intervals of the Doppler shifts given to each of the PL1 polarization transmitting antennas of =2 are all the same (Δfd (1, 3) =Δfd (3, 1) ), and the PL1 polarized transmitting antenna performs equal-interval Doppler multiplexing (equal-interval DDM transmission).

[0516] In addition, in FIG. 20, the interval of the Doppler shift amount (Doppler shift interval) between the transmitting antennas Tx#2 and Tx#4, which are the PL2 polarized waves, is Δfd (2, 4)= 4Δfd, Δfd (4, 2) = 2Δfd. Therefore, the number of PL2 polarized transmitting antennas N PL2 The intervals of the Doppler shifts given to each of the PL2 polarization transmitting antennas of =2 are not all the same interval, but include unequal intervals (Δfd (2, 4) ≠Δfd (4, 2) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) using a PL2 polarized transmitting antenna.

[0517] As described above, the example shown in FIG. 20 is an example of setting a pattern of the amount of Doppler shift that does not satisfy condition 1.

[0518] In addition, in FIG. 20, the interval of the Doppler shift amount between the PL1 polarization transmitting antennas Tx#1 and Tx#3 is Δfd (1, 3) =Δfd (3, 1) = 3Δfd, and the interval of the Doppler shift amount between the PL2 polarization transmitting antennas Tx#2 and Tx#4 is Δfd (2, 4) = 4Δfd, Δfd (4, 2) =2Δfd. Therefore, the amount of Doppler shift between the PL1 polarization transmitting antennas Tx#1 and Tx#3 and the amount of Doppler shift between the PL2 polarization transmitting antennas Tx#2 and Tx#4 include different Doppler shift intervals.

[0519] For example, the interval between the Doppler shift amounts of PL1 polarized wave transmitting antennas Tx#1 and Tx#3 includes 3Δfd, but the interval between the Doppler shift amounts of PL2 polarized wave transmitting antennas Tx#2 and Tx#4 does not include 3Δfd.

[0520] Also, for example, the maximum DDM interval of the Doppler shift amount between PL2 polarization transmitting antennas Tx#2 and Tx#4 includes 2Δfd and 4Δfd, but the interval of the Doppler shift amount between PL1 polarization transmitting antennas Tx#1 and Tx#3 does not include 2Δfd and 4Δfd.

[0521] As described above, in the example shown in FIG. 20, the pattern of the Doppler shift amount assigned to the PL1 polarized wave transmitting antenna is different from the pattern of the Doppler shift amount assigned to the PL2 polarized wave transmitting antenna.

[0522] From the above, the example shown in FIG. 20 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2(1).

[0523] For example, if the radar device 10 does not include target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas, the radar device 10 receives signals corresponding to the PL1 polarization transmitting antennas (Tx#1 and Tx#3) and the PL2 polarization transmitting antennas (Tx#2 and Tx#4) at approximately the same level. Here, signals transmitted from the Nt transmitting antennas Tx#1 to Tx#4, which are made up of the PL1 polarization transmitting antennas and the PL2 polarization transmitting antennas, are Doppler-multiplexed and transmitted using Doppler shift intervals that result in uneven interval Doppler multiplexing. Therefore, the radar device 10 (e.g., the Doppler demultiplexing unit 211) can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of a Doppler-multiplexed signal.

[0524] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd < 1 / (2Tr), and obtain an output that corresponds to the transmitting antenna for each Doppler multiplexed signal.

[0525] Furthermore, when a target reflected wave that is cross-polarized relative to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 2 (1)) depending on whether the PL1 polarization includes a target reflected wave that is cross-polarized or the PL2 polarization includes a target reflected wave that is cross-polarized.

[0526] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0527] This enables the radar device 10 to determine in the Doppler demultiplexing unit 211, for example, based on the detected Doppler frequency peaks (e.g., the interval between peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization transmitting antenna or a decrease in the reception level of the reception signal corresponding to the PL2 polarization transmitting antenna has occurred.

[0528] For example, the PL1 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in equal-interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexer 211 determines that the received signal corresponds to the signal transmitted by the PL1 polarized transmitting antenna, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (4Tr)≦fd<1 / (4Tr) and obtain outputs that associate the transmitting antennas with each Doppler multiplexed signal.

[0529] Furthermore, for example, the PL2 polarized Doppler multiplexed signal is Doppler multiplexed and transmitted using a Doppler shift interval that results in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing separation unit 211 determines that the received signal corresponds to a signal transmitted by a PL2 polarized transmitting antenna, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr) using an existing Doppler multiplexed signal separation operation, thereby separating the Doppler multiplexed signal and obtaining an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0530] (Third Modification of First Embodiment) In the first embodiment, the two polarized waves, PL1 polarized wave and PL2 polarized wave, which are orthogonal to each other, are used as transmission polarized waves of different polarizations. However, the present invention is not limited to this, and the number of polarized waves may be three or more. For example, in addition to the two polarized waves, PL1 polarized wave and PL2 polarized wave, which are orthogonal to each other, a transmission antenna of a polarized wave other than the PL1 polarized wave and the PL2 polarized wave may be used.

[0531] For example, the radar device 10 (for example, a polarized MIMO radar) may use Nt transmitting antennas including transmitting antennas of three or more different polarized waves, including two polarized waves that are orthogonal to each other.

[0532] Hereinafter, the first polarization will be referred to as PL1 polarization, and the second polarization will be referred to as PL2 polarization. The qth polarization will be referred to as PLq polarization. Furthermore, combinations of different polarizations that form orthogonal polarizations may be, for example, PL1 polarization and PL2 polarization, and right-handed circular polarization and left-handed circular polarization, horizontal polarization and vertical polarization, or right-diagonal 45° polarization and left-diagonal 45° polarization.

[0533] In addition, the number of transmitting antennas N t ≧4. For example, the Doppler multiplexing number N DDM ≧4.

[0534] In addition, the transmitting antenna has N PL1 PL1 polarized antennas, and N PL2 In this case, N PL1 + N PL2 <Ntとなる。

[0535] The radar device 10 performs non-uniform Doppler multiplex transmission using, for example, Nt transmitting antennas.

[0536] Furthermore, the radar device 10 performs simultaneous multiplex transmission from Nt transmitting antennas, including transmitting antennas of PL1 polarization and PL2 polarization that are cross-polarized with each other, and transmitting antennas of polarizations different from the PL1 polarization and PL2 polarization, using Doppler multiplex transmission (DDM) that satisfies conditions 1a and 2a described below.

[0537] Conditions 1a and 2a are conditions when, for example, in addition to two polarized waves, PL1 polarization and PL2 polarization, which are orthogonal to each other, a transmitting antenna of a polarized wave different from the PL1 polarization and PL2 polarization is included. For example, if no transmitting antenna of a polarized wave different from the PL1 polarization and PL2 polarization is included in addition to the transmitting antenna of two polarized waves, PL1 polarization and PL2 polarization, which are orthogonal to each other, Conditions 1a and 2a are equivalent to Conditions 1 and 2.

[0538] For example, the reflected waves corresponding to radar transmission signals from the transmitting antennas using PL1 polarization and PL2 polarization, which are orthogonal to each other, are in a cross-polarized relationship with respect to the receiving antenna unit 202, which may result in significantly different reception levels of the received signals. On the other hand, among the Nt transmitting antennas, transmitting antennas using polarizations other than the PL1 polarization and PL2 polarization antennas are not in an orthogonal polarization relationship with the PL1 polarization and PL2 polarization. Therefore, the reflected waves corresponding to radar transmission signals from transmitting antennas using other polarizations are unlikely to have significantly different reception levels from the reception levels of the received signals corresponding to the transmitting antennas using PL1 polarization and PL2 polarization.

[0539] Therefore, for example, in condition 1a, instead of "unequal interval Doppler multiplexing by PL1 polarized antenna" in condition 1, "unequal interval Doppler multiplexing by polarized transmitting antenna excluding PL2 polarized wave (however, N PL1 Considering the case of ≧2, N PL1 Similarly, in condition 1a, instead of "unequal interval Doppler multiplexing by PL2 polarized antenna" in condition 1, "unequal interval Doppler multiplexing by polarized transmitting antenna excluding PL1 polarized wave (however, N PL1 Considering the case of ≧2, N PL2 (No consideration required for 1)" may be applied.

[0540] Also, for example, in condition 2a, instead of "between Doppler multiplexed signals assigned to each of the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna," in condition 2, "between polarized wave transmitting antennas other than the PL2 polarized wave transmitting antenna (for example, (Nt-N PL1) transmit antennas), and polarized transmit antennas other than the PL1 polarized antenna (e.g., (Nt-N PL2 ) transmit antennas) respectively).

[0541] From the above, conditions 1a and 2a may be defined as follows:

[0542] <Condition 1a> Unequally spaced DDM with polarized transmitting antennas excluding PL2 polarization (N PL1 Considering the case of ≧2, N PL1 =1, no consideration required) Unequally spaced DDM with polarized transmitting antennas (excluding PL1 polarization) PL2 Considering the case of ≧2, N PL2 =1 does not require consideration) Doppler multiplexed signals are assigned to the PL1 polarization and the PL2 polarization, respectively, so that:

[0543] <Condition 2a> Polarized transmitting antennas other than PL2 polarization (e.g., (Nt- N PL2 ) transmitting antennas), and polarized transmitting antennas other than PL1 polarization (for example, (Nt-N PL1 ) transmit antennas), any one of the following conditions is satisfied between the Doppler multiplexed signals assigned to each of the transmit antennas. (1) Including different Doppler shift intervals. (2) The Doppler multiplexing number (= number of transmitting antennas) of PL1 polarization and PL2 polarization is different (N PL1 ≠N PL2 ). (3) Nt-N PL1 ≧3, Nt-N PL2 In the case of ≧3, when the same Doppler shift interval is included in the Doppler shift intervals of the polarized transmission antenna excluding PL2 polarization and the polarized transmission antenna excluding PL1 polarization, the order of the Doppler shift intervals is different.

[0544] For example, under condition 1a, the intervals of the Doppler shift amounts assigned to the PL2 polarization transmitting antenna and the different polarization transmitting antenna are set to be uneven on the Doppler frequency axis. Similarly, under condition 1a, the intervals of the Doppler shift amounts assigned to the PL1 polarization transmitting antenna and the different polarization transmitting antenna are set to be uneven on the Doppler frequency axis.

[0545] Furthermore, for example, in condition 2a (1), the intervals of Doppler shift amounts (Doppler shift intervals) assigned to polarized transmitting antennas different from the PL2 polarized transmitting antenna may include intervals different from the intervals of Doppler shift amounts assigned to polarized transmitting antennas different from the PL1 polarized transmitting antenna.Examples of condition 2a (1) include a case where the maximum Doppler shift intervals are different, a case where the minimum Doppler shift intervals are different, or a case where the Doppler shift intervals are neither maximum nor minimum between the Doppler multiplexed signals assigned to polarized transmitting antennas excluding PL2 polarization and polarized transmitting antennas excluding PL1 polarization.

[0546] As an example of condition 2a (2), there is a case where either the PL1 polarized wave transmitting antenna or the PL2 polarized wave transmitting antenna is one, resulting in a SIMO (Single-Input Multiple Output) radar configuration (N PL1 = 1 and N PL2 If ≥ 2, then N PL1 ≧2 and N PL2 = 1), and when there are two or more PL1 polarized transmitting antennas and two or more PL2 polarized transmitting antennas, each of which forms a MIMO radar configuration (N PL1 ≧2 and N PL2 ≧2, N PL1 ≠N PL2 ) are listed.

[0547] Furthermore, for example, in condition 2a (3), the combination of intervals of Doppler shift amounts assigned to the PL2 polarized transmitting antenna and a different polarized transmitting antenna is the same as the combination of intervals of Doppler shift amounts assigned to the PL1 polarized transmitting antenna and a different polarized transmitting antenna, and the order of intervals of Doppler shift amounts assigned to the PL2 polarized transmitting antenna and a different polarized transmitting antenna is different from the order of intervals of Doppler shift amounts assigned to the PL1 polarized transmitting antenna and a different polarized transmitting antenna in the Doppler frequency range.

[0548] For example, the combination of intervals included in an array (e.g., a first array) in which the intervals of Doppler shift amounts assigned to polarized transmitting antennas excluding PL1 polarization are arranged in ascending order on the Doppler frequency axis matches the combination of intervals included in an array (e.g., a second array) in which the intervals of Doppler shift amounts assigned to polarized transmitting antennas excluding PL2 polarization are arranged in ascending order on the Doppler frequency axis, and the first array and the second array are different arrays in terms of circular permutation.

[0549] When condition 2a (3) is satisfied, the Doppler shift interval of the polarized transmitting antenna excluding the PL2 polarization and the Doppler shift interval of the polarized transmitting antenna excluding the PL1 polarization do not match even if either one is cyclically shifted in the Doppler frequency domain.

[0550] An example of setting the amount of Doppler shift in the Doppler shifter 104 will be described below.

[0551] <Doppler shift amount setting example 9> Figure 21 shows the number of transmit antennas, Nt=7, N PL1 =3, N PL2 =3, N PL3 21 shows an example of setting a pattern of the amount of Doppler shift with respect to the transmission Doppler frequency when Tx#1, Tx#4, and Tx#6 are PL1 polarized antennas, Tx#2, Tx#3, and Tx#5 are PL2 polarized antennas, and Tx# 7is a PL3 polarized antenna. For example, PL1 polarized wave and PL2 polarized wave are polarized waves that are orthogonal to each other.

[0552] In the ninth example of setting the amount of Doppler shift, as shown in FIG. 21, the basic unit of the Doppler shift interval in the Doppler shifter 104 is Δfd=1 / (Tr×(N DM +δ))=1 / (8Tr) and δ=1, but the value of δ is not limited to this. δ may be a positive integer or a positive real number.

[0553] In the example shown in FIG. 21, the first to seventh Doppler shift sections 104 (or Doppler shift sections 104-1 to 104-7) may perform the following operations.

[0554] The first Doppler shift unit 104 applies a phase rotation Φ1(m)=-π(m-1) for each transmission period Tr of the chirp signal, for example, to impart a Doppler shift amount DOP1=-1 / (2Tr) to the first transmitting antenna Tx#1, and outputs the result.

[0555] The second Doppler shift unit 104 applies a phase rotation Φ2(m)=-π(m-1) / 2 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP2=-1 / (4Tr) to the second transmitting antenna Tx#2, and outputs the result.

[0556] The third Doppler shift unit 104 applies a phase rotation Φ3(m)=-π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP3=-1 / (8Tr) to the third transmitting antenna Tx#3, and outputs the result.

[0557] The fourth Doppler shift unit 104 imparts a phase rotation Φ4(m)=0 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP4=0 to the fourth transmitting antenna Tx#4, and outputs the result.

[0558] The fifth Doppler shift unit 104 applies a phase rotation Φ5(m)=π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP5=1 / (8Tr) to the fifth transmitting antenna Tx#5, and outputs the result.

[0559] The sixth Doppler shift unit 104 applies a phase rotation Φ6(m)=π(m-1) / 2 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP6=1 / (4Tr) to the sixth transmitting antenna Tx#6, and outputs the result.

[0560] The seventh Doppler shift unit 104 applies a phase rotation Φ7(m)=3π(m-1) / 4 to the chirp signal for each transmission period Tr, for example, to impart a Doppler shift amount DOP7=3 / (8Tr) to the seventh transmitting antenna Tx#7, and outputs the result.

[0561] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval “Δfd (n1, n2) " should be written as ".

[0562] In FIG. 21, the interval between the Doppler shift amounts (Doppler shift interval) given to the respective transmitting antennas Tx#1 to Tx#7 is Δfd (1, 2) =2Δfd, Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd (5, 6) =Δfd (6, 7) =Δfd (7, 1) Therefore, in FIG. 21, the intervals of the Doppler shift amounts given to the transmitting antennas, number of which is Nt=7, are not all the same, but include unequal intervals (for example, Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd (5, 6) =Δfd (6, 7) =Δfd (7, 1) ≠Δfd (1, 2) ), and non-uniform Doppler multiplex transmission (non-uniform DDM transmission).

[0563] In addition, in FIG. 21, among the transmitting antennas, the intervals of the Doppler shift amounts between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7, excluding the PL2 polarization transmitting antenna, are Δfd (1, 4) = 4Δfd, Δfd (4, 6) =2Δfd, Δfd (6, 7) =Δfd (7, 1) =Δfd. Therefore, the number of transmitting antennas excluding the PL2 polarization transmitting antenna (Nt-N PL2 The intervals of the Doppler shifts given to each of the four polarized transmitting antennas are not all the same, but include unequal intervals (Δfd (1, 4) ≠Δfd (4, 6) ≠Δfd (6, 7) =Δfd (7, 1) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed by polarized transmitting antennas other than the PL2 polarized transmitting antenna.

[0564] In addition, in FIG. 21, among the transmitting antennas, the intervals of the Doppler shift amounts (Doppler shift intervals) between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7 excluding the PL1 polarization transmitting antenna are Δfd (2, 3) =Δfd, Δfd (3, 5) =Δfd (5, 7) =2Δfd, Δfd (7, 2) = 3Δfd. Therefore, the number of transmitting antennas excluding the PL1 polarization transmitting antenna (Nt-N PL1 The intervals of the Doppler shifts given to each of the four polarized transmitting antennas are not all the same, but include unequal intervals (Δfd (2, 3) ≠Δfd (3, 5) =Δfd (5, 7) ≠Δfd (7, 2) ), and unevenly spaced Doppler multiplexing (unevenly spaced DDM transmission) is performed by polarized transmitting antennas other than the PL1 polarized transmitting antenna.

[0565] From the above, the example shown in FIG. 21 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 1a.

[0566] In addition, in FIG. 21, the amount of Doppler shift between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7, excluding the PL2 polarization transmitting antenna, is Δfd(1, 4) = 4Δfd, Δfd (4, 5) =2Δfd, Δfd (6, 7) =Δfd (7, 1) =Δfd, and the amount of Doppler shift between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7, excluding the PL1 polarization transmitting antenna, is Δfd (2, 3) =Δfd, Δfd (3, 5) =Δfd (5, 7) =2Δfd, Δfd (7, 2) =3Δfd. Therefore, the amount of Doppler shift between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7, excluding the PL2 polarization transmitting antenna, and the amount of Doppler shift between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7, excluding the PL1 polarization transmitting antenna, include different Doppler shift intervals.

[0567] For example, the interval between the Doppler shift amounts of transmitting antennas Tx#1, Tx#4, Tx#6 and Tx#7, excluding the PL2 polarization transmitting antenna, includes 4Δfd, but the interval between the Doppler shift amounts of transmitting antennas Tx#2, Tx#3, Tx#5 and Tx#7, excluding the PL1 polarization transmitting antenna, does not include 4Δfd.

[0568] Also, for example, the maximum DDM interval of the Doppler shift amount between transmitting antennas Tx#2, Tx#3, Tx#5 and Tx#7 excluding the PL1 polarization transmitting antenna is 3Δfd, but the interval of the Doppler shift amount between transmitting antennas Tx#1, Tx#4, Tx#6 and Tx#7 excluding the PL2 polarization transmitting antenna does not include 3Δfd.

[0569] From the above, the example shown in FIG. 21 is an example of setting a pattern of the amount of Doppler shift that satisfies condition 2a(1).

[0570] For example, if the radar device 10 does not include target reflected waves that are cross-polarized with respect to the polarization of the receiving antennas, the radar device 10 receives signals from the PL1 polarization transmitting antennas (Tx#1, Tx#4, and Tx#6) and the PL2 polarization transmitting antennas (Tx#2, Tx#3, and Tx#5) at approximately the same level. Here, signals transmitted from Nt transmitting antennas Tx#1 to Tx#7, consisting of the PL1 polarization transmitting antennas, PL2 polarization transmitting antennas, and PL3 polarization transmitting antennas, are Doppler-multiplexed and transmitted using Doppler shift intervals resulting in uneven interval Doppler multiplexing. Therefore, the radar device 10 can demultiplex Doppler-multiplexed signals based on the existing operation of demultiplexing Doppler-multiplexed signals.

[0571] Furthermore, when a target reflected wave that is cross-polarized relative to the polarization of the receiving antenna is included, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 2a-(1)) depending on whether the PL1 polarization includes a target reflected wave that is cross-polarized or the PL2 polarization includes a target reflected wave that is cross-polarized.

[0572] For example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal that includes Doppler frequency components with different patterns when the reception level of the received signal corresponding to the PL1 polarization transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarization transmitting antenna decreases.

[0573] This enables the radar device 10 to determine in the Doppler demultiplexing unit 211, for example, based on the detected Doppler frequency peaks (e.g., the interval between peaks), whether a decrease in the reception level of the reception signal corresponding to the PL1 polarization transmitting antenna or a decrease in the reception level of the reception signal corresponding to the PL2 polarization transmitting antenna has occurred.

[0574] For example, Doppler multiplexed signals of polarizations other than the PL2 polarization are Doppler multiplexed and transmitted using Doppler shift intervals that result in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by a polarization transmitting antenna other than the PL2 polarization transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0575] Similarly, for example, Doppler multiplexed signals of polarizations other than the PL1 polarization are Doppler multiplexed and transmitted using Doppler shift intervals that result in unequal interval Doppler multiplexing. Therefore, for example, when the Doppler demultiplexing unit 211 determines that the received signal corresponds to a signal transmitted by a polarization transmitting antenna other than the PL1 polarization transmitting antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using an existing demultiplexing operation for Doppler multiplexed signals.

[0576] By operating the Doppler multiplexing separation unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd < 1 / (2Tr), and obtain an output that corresponds to the transmitting antenna for each Doppler multiplexed signal.

[0577] An example of setting the amount of Doppler shift has been described above.

[0578] [Example of operation of Doppler demultiplexing unit 211] For example, when a transmitting antenna of a polarization other than the PL1 polarization and the PL2 polarization is used in addition to two polarizations of the PL1 polarization and the PL2 polarization which are orthogonal to each other, the Doppler multiplexed signal given in the above-described Doppler shifter 104 can be separated by the following operation of the Doppler demultiplexer 211. The following describes the operation of the Doppler demultiplexer 211 according to the third modification that differs from that of the first embodiment.

[0579] For example, when δ shown in equation (3) is set to a positive integer in the Doppler shifter 104, the Doppler demultiplexer 211 calculates the distance index f b_cfar , the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ), and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) where ndm=1 to N DM +δ is an integer.

[0580] In the third modification, among the operations of separating Doppler multiplexed signals in Doppler demultiplexing section 211 shown in FIG. 17, the operations of step B and step C differ from those of the first embodiment as follows.

[0581] <Step B-1> The Doppler demultiplexing unit 211 assumes that the PL2 polarized wave is a cross-polarized wave relative to the polarized wave of the receiving antenna and includes a target reflected wave. PL2 ) and perform Doppler demultiplexing processing on the Doppler multiplexed signals of the polarizations excluding the PL2 polarization.

[0582] <Step B-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indexes (f sddm_cfar +(ndm-1)×N Δfd ) and Nt-N from the transmitting antennas excluding the PL2 polarization transmitting antenna. PL2 It is assumed that the signal contains Doppler multiplexed signals.

[0583] The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd))(For example, ndm=1~N DM +δ) and compare the top Nt-N PL2 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval given to the transmitting antennas excluding the PL2 polarization transmitting antenna during transmission (for example, "Doppler shift interval match determination excluding the PL2 polarization transmitting antenna").

[0584] Further, the Doppler demultiplexing unit 211 demultiplexes, for example, the most powerful Nt-N PL2 Doppler frequency indexes and the top Nt-N received powers PL2 Doppler frequency indexes (N DM +δ-(Nt-N PL2 )) It is determined whether the difference (or reception level ratio) between the reception levels of the other Doppler frequency indexes is significantly different (for example, whether the difference is equal to or greater than a threshold, or whether the reception level ratio is equal to or greater than a threshold) (for example, this is called "Doppler multiplexed signal reception level difference determination excluding PL2 polarization transmitting antenna").

[0585] Based on these determinations, the Doppler demultiplexing unit 211 determines the Doppler frequency and transmitting antenna corresponding to the Doppler multiplexed signal in the range of -1 / (2Tr)≦fd<1 / (2Tr), for example.

[0586] An example of the operation of the Doppler demultiplexing unit 211 that separates the Doppler multiplexed signals at unequal intervals is disclosed in, for example, Patent Document 7, and therefore a detailed description of the operation will be omitted here.

[0587] For example, the Doppler demultiplexing unit 211 determines whether or not both conditions (e.g., the condition of step B-2) of determining whether the Doppler shift interval matches excluding the PL2 polarization transmitting antenna and determining whether or not the Doppler multiplexed signal reception level difference excluding the PL2 polarization transmitting antenna are satisfied. If the condition of step B-2 is satisfied, the Doppler demultiplexing unit 211 performs the process of step B-3, and if the condition of step B-2 is not satisfied, the Doppler demultiplexing unit 211 may perform the process of step C-1, assuming that a target reflected wave in which the PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is included.

[0588] <Step B-3> The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with the lowest reception level N DM +δ-(Nt-N PL2 ) Doppler frequency indexes and the top Nt-N PL2 Based on the relationship with the Doppler frequency indexes, the Doppler shift amounts DOP1, DOP2, ~, DOP of the Nt Doppler multiplexed signals to be transmitted are calculated. Nt and the Doppler frequency index are associated with each other to obtain the separation index information DDM_RXindex_ PL1 (f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as the distance index f b_cfar At the same time, it outputs the result to the direction estimation unit 212.

[0589] where f demul_Tx#n denotes the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the n-th transmitting antenna (Tx#n).

[0590] Furthermore, the Doppler demultiplexing unit 211 outputs, for example, the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes to the direction estimation unit 212 .

[0591] Alternatively, the Doppler demultiplexing unit 211 selects Nt transmitting antennas from which PL1 polarized waves are transmitted. PL1 The Doppler shift amount of each Doppler multiplexed signal is associated with the Doppler frequency index, and the PL1 polarization separation index information of the Doppler multiplexed signal is stored as DDM_Rxindex_ PL1 (f b_cfar ) as the distance index f b_cfar At the same time, it may be output to the direction estimation unit 212.

[0592] <Step C-1> The Doppler demultiplexing unit 211 assumes that PL1 includes a target reflected wave that is a cross-polarized wave with respect to the polarization of the receiving antenna, and PL1 Doppler demultiplexing processing is performed on the Doppler multiplexed signals of the polarizations excluding the PL1 polarization.

[0593] <Step C-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indexes (f sddm_cfar +(ndm-1)×N Δfd ) and Nt-N from the transmitting antennas excluding the PL1 polarization transmitting antenna. PL1 It is assumed that the signal contains Doppler multiplexed signals.

[0594] The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd ))(For example, ndm=1~N DM +δ) and compare the top Nt-N PL1 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd) during transmission, it is determined whether it matches the Doppler shift interval assigned to the transmitting antennas excluding the PL1 polarization transmitting antenna (for example, this is called "Doppler shift interval match determination excluding the PL1 polarization transmitting antenna").

[0595] Further, the Doppler demultiplexing unit 211 demultiplexes, for example, the most powerful Nt-N PL1 Doppler frequency indexes and the top Nt-N received powers PL1 Doppler frequency indexes (N DM +δ-(Nt-N PL1 )) It is determined whether the difference (or reception level ratio) between the reception levels of the other Doppler frequency indexes is significantly different (for example, whether the difference is equal to or greater than a threshold, or whether the reception level ratio is equal to or greater than a threshold) (for example, this is called "Doppler multiplexed signal reception level difference determination excluding PL1 polarization transmitting antenna").

[0596] The Doppler demultiplexing unit 211 determines a Doppler frequency and a transmitting antenna in the range of -1 / (2Tr)≦fd<1 / (2Tr), for example, based on these determinations.

[0597] An example of the operation of the Doppler demultiplexing unit 211 that separates the Doppler multiplexed signals at unequal intervals is disclosed in, for example, Patent Document 7, and therefore detailed description of the operation will be omitted here.

[0598] The Doppler demultiplexing unit 211 determines whether or not both the conditions for determining whether the Doppler shift interval matches excluding the PL1 polarization transmitting antenna and the conditions for determining whether or not the Doppler multiplexed signal reception level difference excluding the PL1 polarization transmitting antenna (for example, the condition of step C-2) are met. If the condition of step C-2 is met, the Doppler demultiplexing unit 211 may perform the process of step C-3. If the condition of step C-2 is not met, the Doppler demultiplexing unit 211 may determine that the received signal is a noise component or an interference component, and may not output the signal to the direction estimation unit 212 (step D).

[0599] <Step C-3> The Doppler demultiplexing unit 211 uses, for example, a Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with the lowest reception level N DM +δ-(Nt-N PL1 ) Doppler frequency indexes and the top Nt-N PL1 Based on the relationship with the Doppler frequency indexes, the Doppler shift amounts DOP1, DOP2, ~, DOP Nt and the Doppler frequency index are associated with each other to generate the separation index information DDM_Rxindex_ PL2 (f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as the distance index f b_cfar At the same time, it outputs the result to the direction estimation unit 212.

[0600] where f demul_Tx#n denotes the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the n-th transmitting antenna (Tx#n).

[0601] Furthermore, the Doppler demultiplexing unit 211 outputs, for example, the outputs of the Doppler analysis unit corresponding to these distances and Doppler separation indexes to the direction estimation unit 212 .

[0602] Alternatively, the Doppler demultiplexing unit 211 selects Nt transmitting antennas from which PL2 polarized waves are transmitted. PL2 The Doppler shift amount of each Doppler multiplexed signal is associated with the Doppler frequency index, and the PL2 polarization separation index information of the Doppler multiplexed signal is stored as DDM_Rxindex_ PL2 (f b_cfar ) as the distance index f b_cfar At the same time, it may be output to the direction estimation unit 212.

[0603] An example of the operation of the Doppler demultiplexing unit 211 has been described above.

[0604] (Embodiment 2) In the first embodiment, a case has been described in which, in a polarized MIMO radar using Nt transmitting antennas including transmitting antennas of different polarizations, the radar device 10 simultaneously multiplexes using all of the Nt transmitting antennas using uneven Doppler multiplexing, and transmits Doppler multiplexed signals that satisfy at least condition 2 ("condition 1 and condition 2," or "condition 2") using the Doppler shift unit 104. As a result, in the first embodiment, even if the reflected wave reception levels differ greatly between the transmitting polarized antennas, the Doppler multiplexing separation unit 211 can distinguish between the transmitting polarized antennas and separate the Doppler multiplexed signals, thereby suppressing deterioration in the detection performance of the polarized MIMO radar using uneven Doppler multiplexing.

[0605] In this way, when the reflected wave reception levels differ greatly between the transmitting polarization antennas, the method for enabling the Doppler multiplexing separation unit 211 to distinguish the transmitting polarization antenna and separate the Doppler multiplexed signal is not limited to the method described in embodiment 1.

[0606] In this embodiment, a method of unevenly spaced Doppler multiplexing transmission will be described in which transmission signals transmitted from differently polarized transmission antennas are transmitted with transmission periods shifted in time from each other by a plurality of transmission antennas of the same polarization.

[0607] For example, in this embodiment, the timing at which a transmission signal is transmitted from the PL1 polarized wave transmitting antenna may be different from the timing at which a transmission signal is transmitted from the PL2 polarized wave transmitting antenna.

[0608] By using this method, even if the reflected wave reception level differs greatly between the transmitting polarization antennas, the Since the polarization of the transmitted waves is known, the radar device can distinguish between the transmitting polarization antennas. Therefore, the reception levels of reflected waves at multiple transmitting antennas of the same polarization are unlikely to differ significantly, making it possible to separate the Doppler signals from unevenly spaced Doppler multiplexing transmissions and suppressing deterioration in the detection performance of polarized MIMO radars using unevenly spaced Doppler multiplexing transmissions.

[0609] Fig. 22 shows a configuration diagram of a radar device 100c according to this embodiment. An example of the operation of the radar device 100c will be described below with reference to Fig. 22. In Fig. 22, the same components as those in the first embodiment (e.g., Fig. 5) are denoted by the same reference numerals. In this embodiment, the operation different from that in the first embodiment will be mainly described.

[0610] For example, in the radar device 10b shown in FIG. 22, a transmission switching control unit 301 and a transmission switching unit 302 are added to the radar transmitter 100b, and an output switching unit 401 is added to the radar receiver 200b, compared to the radar device 10 shown in FIG.

[0611] 22 shows a polarized MIMO radar that uses Nt transmitting antennas, and the Nt transmitting antennas of the transmitting antenna unit 105 include a PL1 polarized transmitting antenna and a PL2 polarized transmitting antenna that are orthogonal to each other. Hereinafter, the qth polarized wave will be referred to as "PLq polarized wave."

[0612] Combinations of different polarizations that form orthogonal polarizations may be, for example, right-handed circular polarization and left-handed circular polarization, horizontal polarization and vertical polarization, or right-diagonal 45° polarization and left-diagonal 45° polarization as the (PL1, PL2) polarization.

[0613] The transmitting antenna unit 105 includes PL1 polarized wave transmitting antennas N PL1 ≧2, Number of PL2 polarized transmitting antennas N PL2 ≥ 2 transmit antennas. For example, if the number of transmit antennas is N t =N PL1 + N PL2 ≧4 is also acceptable.

[0614] In the following example, N PL1 =N PL2 Let the number of Doppler multiplexing be N DM =N PL1 =N PL2The case will be described in which the amount of Doppler shift applied to each transmitting antenna for each time division transmission is the same, but this is not limited to this, and the amount of Doppler shift applied to each transmitting antenna for each time division transmission may be different.

[0615] Also, N PL1 =N PL2 Not limited to the case of N PL1 ≠N PL2 It's okay. N PL1 ≠N PL2 In this case, the Doppler multiplexing number may change for each time division transmission, and the Doppler multiplexing number N DM1 N DM1 =N PL1 and the Doppler multiplexing number N in the second transmission period DM2 N DM2 =N PL2 This can be considered.

[0616] In the following, the number of time division multiplexes is referred to as "N TM " N TM For example, when the Nt transmitting antennas include a PL1 polarized transmitting antenna and a PL2 polarized transmitting antenna which are orthogonally polarized to each other, N TM For example, the number of time division multiplexes N TM may be set equal to the number of polarizations included in the transmit antenna.

[0617] In the following, as an example, DM =N PL1 =N PL2 and the number Nt of transmitting antennas included in the transmitting antenna unit 105 is Nt=N DM ×N TM The number of Doppler multiplexing N DM and the number of time division multiplexes N TM The case where and are used will be explained.

[0618] [Configuration example of radar transmitter 100b] The transmission switching control unit 301 generates a time division multiplexing index "TM_INDEX" that instructs switching of the transmission antennas in the transmission antenna unit 105 used for time multiplexing for each radar transmission period (Tr), and outputs the time division multiplexing index TM_INDEX to the transmission switching unit 302 and the output switching unit 401.

[0619] where TM_INDEX=1, 2, ~, N TM For example, in the mth transmission period, TM_INDEX=MOD(m-1, N TM ) + 1, where MOD(x, y) is the modulo operator, a function that outputs the remainder after dividing x by y.

[0620] The radar transmitter 100b shown in FIG. 22 may be configured to, for example, set the Doppler multiplexing number to N DM In this case, N DM Doppler shift units 104-1 to 104-N DM The radar transmitter 100b includes N DM The transmission switching unit 302 is provided.

[0621] Each Doppler shifter 104 applies a predetermined Doppler shift amount DOP to the chirp signal input from the radar transmission signal generator 101. ndm To give a given phase rotation φ ndm and outputs the chirp signal with phase rotation to the corresponding transmission switching unit 302. Here, ndm=1, ∼, N DM is.

[0622] The ndm-th transmission switching unit 302 switches the output of the ndm-th Doppler shift unit 104 to the {(ndm-1)×N TM +TM_INDEX}th transmitting antenna and output.

[0623] By the above-described operation of the Doppler shift unit 104 and the transmission switching unit 302, the n-th transmission antenna among the Nt transmission antennas of the transmission antenna unit 105 outputs the floor[(n-1) / N TM ]+Doppler shift DOP by the first Doppler shift unit 104 floor[(n-1) / NTM]+1 The signal with the given value is the floor[(n-1) / N TM ]+1st transmission switch unit 302 modulates the time division multiplexing index TM_INDEX by mod(n-1, N TM )+1.

[0624] Here, the transmission switching unit 302 outputs the signal so that the polarization of the transmission antenna is switched for each time division multiplexing index TM_INDEX. TM When TM_INDEX=2, the transmission switching unit 302 switches the Nt transmitting antennas of the transmitting antenna unit 105 so that the transmission signal is output from the PL1 polarized transmitting antenna when TM_INDEX=1, and so that the transmission signal is output from the PL2 polarized transmitting antenna when TM_INDEX=2.

[0625] Therefore, in the operation of the transmission switching unit 302, N TM When = 2, among the Nt transmitting antennas, a transmitting antenna (e.g., Tx#n) where n is an odd number may represent a PL1 polarized transmitting antenna, and a transmitting antenna where n is an even number may represent a PL2 polarized transmitting antenna.

[0626] For example, Nt=6 transmit antennas, Doppler multiplexing number N DM =3, time division multiplexing number N TM In this case, N DM =N PL1 =N PL2 = 3, and there are three PL1 polarized wave transmitting antennas and three PL2 polarized wave transmitting antennas. DM ) Doppler shift units 104 respectively apply Doppler shift amounts DOP1, DOP2, and DOP3 to the chirp signals.DM The time division multiplexing index TM_INDEX of each of the transmission switching units 302 is 2(=N TM ) elements.

[0627] In this case, for example, the first transmitting antenna (Tx#1) is a PL1 polarized wave transmitting antenna, and outputs the following signal for each transmission period Tr.

number

[0628] Here, cp(t) represents a chirp signal for each transmission period Tr. Also, the phase rotation φ in the Doppler shifter 104 ndm The multiplication value when adding (m) is Λ shown in the following equation (26). ndm It can be written as (m), and can be set to zero if there is no transmission signal.

number

[0629] Similarly, for example, the second transmitting antenna (Tx#2) is a PL2 polarized wave transmitting antenna, and outputs the following signal for each transmission period Tr.

number

[0630] Similarly, for example, the third transmitting antenna (Tx#3) is a PL1 polarized wave transmitting antenna, and outputs the following signal for each transmission period Tr.

number

[0631] Similarly, for example, the fourth transmitting antenna (Tx#4) is a PL2 polarized wave transmitting antenna, and outputs the following signal for each transmission period Tr.

number

[0632] Similarly, for example, the fifth transmitting antenna (Tx#5) is a PL1 polarized wave transmitting antenna, and outputs the following signal for each transmission period Tr.

number

[0633] Similarly, for example, the sixth transmitting antenna (Tx#6) is a PL2 polarized wave transmitting antenna, and outputs the following signal for each transmission period Tr.

number

[0634] Furthermore, the radar transmitter 100b transmits chirp pulses N times. TM For example, N C =N TM ×Ncode.

[0635] [Configuration example of radar receiver 200b] Next, an example of the configuration of the radar receiver 200b shown in FIG. 22 will be described.

[0636] In the z-th signal processing unit 206b, the output switching unit 401 switches the output of the beat frequency analysis unit 208 for each transmission period Tr based on the time division multiplexing index TM_INDEX input from the transmission switching control unit 301, as follows: TM Doppler analysis units 209-1 to 209-N TM , and outputs the signal to the TM_INDEX-th Doppler analyzer 209. For example, the output switching unit 401 selects the TM_INDEX-th Doppler analyzer 209 in the m-th transmission cycle Tr.

[0637] The zth signal processing unit 206b is N TM The Doppler analyzer 209 is provided.

[0638] The ntm-th Doppler analyzer 209 in the z-th signal processor 206b is provided with an N TM Every transmission cycle (N TM Therefore, the ntm-th Doppler analyzer 209 receives data from N C Doppler analysis is performed using data from Ncode transmission periods out of the N transmission periods. Here, ntm=1,~,N TM is.

[0639] Furthermore, when Ncode is a power of 2, the Doppler analysis unit 209 can apply FFT (Fast Fourier Transform) processing as shown in the following equation (32).

number

[0640] Here, the FFT size is Ncode, and the maximum Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is ±1 / (2 N TM ×Tr). Also, the Doppler frequency index f s The Doppler frequency interval is 1 / (Ncode× N TM ×Tr), and the Doppler frequency index f s The range of f s =-Ncode / 2,~,0,~, Ncode / 2-1.

[0641] If Ncode is not a power of 2, for example, by including zero-padded data, FFT processing can be performed with an FFT size that is a power of 2. Furthermore, during FFT processing, a window function coefficient such as a Han window or a Hamming window may be multiplied, and applying the window function can suppress side lobes that occur around the beat frequency peak.

[0642] The CFAR unit 210b is a unit of the first to Nth signals from all the signal processing units 206b. TM The output of the Doppler analyzer 209 is used to perform CFAR processing (for example, adaptive threshold determination) to determine the distance index f that gives the peak signal.b_cfar and the Doppler frequency index f s_cfar Extract.

[0643] The CFAR unit 210b may perform, for example, two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity), or CFAR processing that combines one-dimensional CFAR processing. For the two-dimensional CFAR processing or the CFAR processing that combines one-dimensional CFAR processing, for example, the processing disclosed in Non-Patent Document 1 may be applied.

[0644] In the operation of the Doppler shift unit 104, for example, "Tr" in equation (3) is changed to "(N TM The Doppler shift amount may be set in units of Δfd, which is expressed by the formula in which δ is replaced with "Δfd × Tr". In this case, for example, if δ is set to a positive integer, the interval of the Doppler shift amount is set to an interval of Δfd or an interval that is an integer multiple of Δfd, and each Doppler-multiplexed signal can be detected in the Doppler frequency domain of the output of the Doppler analysis unit 209 as if it were folded over at intervals of Δfd. By utilizing this property, for example, the operation of the CFAR unit 210b can be simplified as follows.

[0645] The CFAR unit 210b detects a Doppler peak by using a threshold value for a power sum obtained by adding up the received power of the reflected wave signal for each range (e.g., range of Δfd) that is a unit of each interval of the Doppler shift amount imparted to each radar transmission signal within the Doppler frequency range to be subjected to CFAR processing output from the Doppler analysis unit 209.

[0646] For example, the CFAR unit 210b calculates the Doppler amplitudes at intervals of Δfd (for example, N Δfd (corresponding to) and the power value PowerqFT shown in equation (34) ntm (f b , f s ) PowerDDM ntm (f b , f sddm) and perform CFAR processing. sddm =-N code / 2,~,-N code / 2+N Δfd -1 and N Δfd = round(Δfd / (1 / (T r N TM N code )) Also, round(x) is an operator that rounds off a real number x to output an integer value.

number

number

[0647] As a result, the range of Doppler frequencies to be subjected to CFAR processing in the CFAR unit 210b is expanded to the entire range of Doppler frequency index range f s (e.g., -N code / 2~N code / 2-1) to the range of Δfd, the amount of calculation required for CFAR processing can be reduced to 1 / (N DM +δ).

[0648] The CFAR unit 210b adaptively sets a threshold value, for example, and calculates a distance index f that provides a received power greater than the threshold value for the output from the ntm-th Doppler analyzer 209 of the first to Na-th signal processors 206b. b_cfar , ntm , the Doppler frequency index f sddm_cfar, ntm , and the received power information (PowerFT) from the ntm-th Doppler analyzer 209 ntm (f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) to the Doppler demultiplexing unit 211b. Here, ndm =1 to N DM +δ are integers, and ntm=1,~, N TM is an integer.

[0649] The Doppler demultiplexing unit 211b receives information (for example, a distance index f b_cfar , ntm , the Doppler frequency index f s_cfar , ntm , and received power information PowerFT ntm (f b_cfar , ntm , f s_cfar , ntm )), the output from the ntm-th Doppler analyzer 209 is used to separate the transmission signals transmitted from each transmission antenna of the transmission antenna unit 105.

[0650] The operation of the Doppler demultiplexing unit 211b will be described below together with the operation of the Doppler shift unit 104.

[0651] 1st~N DM The Doppler shift unit 104 applies different Doppler shift amounts DOP1, DOP2, . . . DOP to the input chirp signal. NDM Here, the Doppler shift amounts DOP1, DOP2, ~, DOP NDM Each interval (Doppler shift interval) may be, for example, not equal intervals obtained by dividing the Doppler frequency range where aliasing does not occur, as in the first embodiment, but may be equal intervals obtained by dividing the range (for example, at least one Doppler interval may be different).

[0652] In the first embodiment, when the number of Doppler multiplexing is equal to the number of transmitting antennas (for example, Nt=N DM ) has been described. In contrast to this, in this embodiment, time division multiplexing is used in addition to Doppler multiplexing, so the Doppler multiplexing number N DM is a multiplexing number that is smaller than the number of transmitting antennas Nt (for example, Nt>N DM ).

[0653] For example, in this embodiment, time division multiplexing is performed, so the transmission period for each transmission antenna is (N TM Therefore, in this embodiment, "Tr" in the formula (3) used in the first embodiment is changed to "(NTM ×Tr) can be used. TM ×Tr), if the same phase rotation is used, the transmission period (N TM ×Tr) with the same phase rotation φ ndm (m) may be output repeatedly.

[0654] For example, the ndm-th Doppler shift unit 104 may perform a different Doppler shift amount DOP on the m-th chirp signal input. ndm The phase rotation φ as shown in the following equation (35) ndm (m) is assigned.

number

[0655] In this embodiment, the Doppler demultiplexing unit 211b performs the Doppler demultiplexing for each TM_INDEX (ntm=1, . . ., N TM ) contains the reflected wave reception signals of the transmission signals that have been Doppler multiplexed using the same polarization transmission antenna, and a Doppler demultiplexing process is performed to separate the Doppler multiplexed signals from the output of the Doppler analysis unit 209 for each TM_INDEX.

[0656] The distance index f input from the CFAR unit 210b b_cfar , ntm N in DM +δ Doppler frequency indexes f sddm_cfar , ntm +(ndm-1)×N Δfd ) includes, for example, N DM The signal includes Doppler multiplexed signals at irregular intervals.

[0657] For example, the Doppler demultiplexing unit 211b uses the Doppler frequency index f sddm_cfar , ntm +(ndm-1)×N Δfd ) received power (PowerFT ntm (f b_cfar , ntm , f sddm_cfar , ntm+(ndm-1)×N Δfd ))(For example, ndm=1~N DM +δ) and compare the top N received powers. DM Doppler frequency index f sddm_cfar , ntm +(ndm-1)×N Δfd ) matches the Doppler shift interval given at the time of transmission (for example, "N DM This is called "Doppler shift interval match judgment."

[0658] Also, for example, the Doppler demultiplexing unit 211b demultiplexes the top N signals of the received power. DM The received power levels of the Doppler frequency indexes and the top N received powers DM It is determined whether the difference (or the ratio of the reception levels) between the Doppler frequency indexes and the δ other Doppler frequency indexes is significantly different (for example, whether the difference is equal to or greater than a threshold, or whether the ratio of the reception levels is equal to or greater than a threshold) (for example, whether "N DM This is called "judgment of the difference in the received Doppler multiplexed signal level."

[0659] The Doppler demultiplexing unit 211b calculates, for example, −1 / (2 N TM Tr) ≦ fd <1 / (2 N TM The Doppler frequency and transmitting antenna corresponding to the Doppler multiplexed signal in the range of Tr are determined.

[0660] An example of the operation of the Doppler multiplexing separation unit 211b that separates the Doppler multiplexed signals at unequal intervals is disclosed in, for example, Patent Document 7, and therefore detailed description of the operation will be omitted here.

[0661] For example, the Doppler demultiplexing unit 211b extracts PL ntm The Doppler demultiplexing unit 211b performs Doppler demultiplexing processing to separate the Doppler multiplexed signals from the polarized wave transmitting antenna. Here, the Doppler demultiplexing unit 211b calculates a Doppler frequency index (f sddm_cfar , ntm+(ndm-1)×N Δfd ) among them, δ Doppler frequency indexes with small reception levels and the top N with high reception power are DM Based on the relationship with the Doppler frequency indexes, the Doppler shift amounts DOP1, DOP2, ~, DOP of the Nt Doppler multiplexed signals to be transmitted are calculated. Nt and the Doppler frequency index are associated with each other to obtain the separation index information DDM_RXindex of the Doppler multiplexed signal. ntm (f b_cfar , ntm )=(f demul_Tx# ntm ,~,f demul_Tx#{(NDM-1)NTM+ntm} ) as the distance index f b_cfar , ntm At the same time, it outputs the result to the direction estimation unit 212b.

[0662] where f demul_Tx#n denotes the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmitting antenna (Tx#n), where ndm = 1 to N DM +δ are integers, and ntm=1,~, N TM is an integer.

[0663] Furthermore, the Doppler demultiplexing unit 211b outputs, for example, the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes to the direction estimation unit 212b.

[0664] The amount of Doppler shift applied to each transmitting antenna of the transmitting antenna unit 105 in the Doppler shift unit 104 of the radar transmitter 100b is known. ntm (f b_cfar ) and the Doppler shift amount given to each transmitting antenna in the radar transmitter 100b is the Doppler frequency of the target. ntm (f b_cfar ) instead of -1 / (2N TM Tr) ≦ fd <1 / (2 NTM Tr) to the direction estimation unit 212b. In this case, the direction estimation unit 212b calculates separation index information DDM_RXindex(f b_cfar ), similar behavior can be achieved by generating

[0665] In this manner, the Doppler demultiplexing unit 211b can demultiplex the Doppler multiplexed signal.

[0666] An example of the operation of the Doppler demultiplexing unit 211b has been described above.

[0667] In FIG. 22, the direction estimation unit 212b receives, for example, information input from the Doppler demultiplexing unit 211b (for example, a distance index f b_cfar , ntm and Doppler multiplex signal separation index information DDM_RXindex ntm (f b_cfar , ntm )), and based on the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indexes, the direction of the target is estimated based on

[0668] For example, the direction estimation unit 212b calculates a distance index f from the output of the ntm-th Doppler analysis unit 209. b_cfar , ntm , and separation index information DDM_RXindex ntm (f b_cfar , ntm ) and extract the output corresponding to PL ntm Virtual receiving array correlation vector h with polarized transmitting antennas PLntm (f b_cfar , ntm , DDM_Rxindex(f b_cfar , ntm )) and perform direction estimation processing.

[0669] where h PLntm (f b_cfar , ntm , DDM_Rxindex(f b_cfar , ntm )) is N PLntm ×Na elements.

[0670] For example, the direction estimation unit 212b calculates a distance index f b_cfar ,1, and separation index information DDM_RXindex1(f b_cfar ,1) is extracted, and the virtual receiving array correlation vector h PL1 (f b_cfar ,1, DDM_Rxindex(f b_cfar , 1)) may be generated. For example, the direction estimation unit 212b may generate a distance index f b_cfar ,2, and separation index information DDM_RXindex2(f b_cfar , 2) and calculate the virtual receiving array correlation vector h PL2 (f b_cfar ,2, DDM_Rxindex(f b_cfar ,2)) may be generated.

[0671] The direction estimation unit 212b calculates, for example, a virtual receiving array correlation vector h PL1 (f b_cfar ,1, DDM_Rxindex(f b_cfar , 1)) and the virtual receiving array correlation vector h PL2 (f b_cfar ,2, DDM_Rxindex(f b_cfar ,2)) is used to calculate the direction estimation evaluation function P H-PLq (θ u , f b_cfar , DDM_Rxindex(f b_cfar )) azimuth direction θ uis varied within a predetermined angle range to calculate the spatial profile for each transmit polarization, where q=1 and 2.

[0672] The direction estimation unit 212b may extract a predetermined number of maximum peaks from the calculated spatial profile for each transmission polarization in descending order, and output the azimuth directions of the maximum peaks as estimated values ​​of the direction of arrival (e.g., positioning outputs) of the PLq polarization transmission, where q=1 and 2.

[0673] The subsequent operation of direction estimation unit 212b is similar to the operation of direction estimation unit 212 in the first embodiment, and therefore an explanation of the operation example will be omitted.

[0674] As described above, in this embodiment, by using both Doppler multiplexing and time division multiplexing, in addition to the same effects as in the first embodiment, the number of signals that can be multiplexed and transmitted simultaneously can be increased, and it becomes possible to apply this to a MIMO array configuration with an increased number of transmitting antennas. Also, in this embodiment, for example, even for transmitting polarization antennas with two or more types of polarization transmitting antennas, TM The increase in σ similarly makes it possible to apply it to MIMO array configurations.

[0675] For example, since the transmission period is different for each polarized transmitting antenna, the radar device 100c can separate Doppler multiplexed signals even when receiving reflected waves that are cross-polarized with the polarization of the receiving antenna. For example, the range of Doppler frequencies that can be detected by the radar device 100c is 1 / N that of the first embodiment. TM However, in either case, the Doppler detection range can be expanded beyond that of the equally spaced DDM, −1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr) (provided Nt≧4 or more).

[0676] The embodiments of the present disclosure have been described above.

[0677] [Other embodiments] In a radar device according to an embodiment of the present disclosure, the radar transmitter and the radar receiver may be located separately in physically separated locations. Also, in a radar receiver according to an embodiment of the present disclosure, the direction estimator and other components may be located separately in physically separated locations.

[0678] In addition, the number of transmitting antennas Nt, the number of receiving antennas Na, and the number of Doppler multiplexing N DM , PLq polarized transmitting antenna number N PLq The numerical values ​​of the parameters such as the number of polarizations, the amount of Doppler shift, and the interval of Doppler shift are merely examples, and the present invention is not limited to these values.

[0679] Although not shown, a radar device according to an embodiment of the present disclosure includes, for example, a central processing unit (CPU), a storage medium such as a read-only memory (ROM) storing a control program, and a working memory such as a random access memory (RAM). In this case, the functions of the above-described units are realized by the CPU executing the control program. However, the hardware configuration of the radar device is not limited to this example. For example, each functional unit of the radar device may be realized as an integrated circuit (IC). Each functional unit may be individually implemented on a single chip, or a single chip may include some or all of the functional units.

[0680] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the disclosure.

[0681] Furthermore, the notation "... section" in the above-described embodiments may be replaced with other notations such as "... circuitry," "... assembly," "... device," "... unit," or "... module."

[0682] In each of the above embodiments, the present disclosure has been described as an example configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

[0683] Furthermore, each functional block used in the description of each of the above embodiments is typically realized as an LSI, which is an integrated circuit. The integrated circuit controls each functional block used in the description of the above embodiments and may have input and output terminals. These may be individually integrated into single chips, or some or all of them may be integrated into a single chip. While the term LSI is used here, it may also be called an IC, system LSI, super LSI, or ultra LSI depending on the level of integration.

[0684] Furthermore, the method of integration is not limited to LSI, but may be realized using a dedicated circuit or a general-purpose processor. It is also possible to use a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections or settings of circuit cells inside the LSI.

[0685] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology may be used to integrate functional blocks. The application of biotechnology, etc. is also a possibility.

[0686] Summary of this disclosure A radar device according to an embodiment of the present disclosure includes a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave, and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which phase rotations corresponding to Doppler shift amounts assigned to each of the plurality of transmitting antennas have been imparted, wherein Doppler multiplexing intervals for the plurality of transmitting antennas are unevenly spaced on a Doppler frequency axis, and a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna.

[0687] In one embodiment of the present disclosure, the first pattern and the second pattern relate to the Doppler multiplexing intervals, and at least one of the Doppler multiplexing intervals by the first transmitting antenna is different from the Doppler multiplexing interval by the second transmitting antenna.

[0688] In one embodiment of the present disclosure, the first pattern and the second pattern are different in number of transmitting antennas, that is, the number of the first transmitting antennas is different from the number of the second transmitting antennas.

[0689] In one embodiment of the present disclosure, the first pattern and the second pattern are related to Doppler multiplexing, and the Doppler multiplexing using the first polarization and the Doppler multiplexing using the second polarization are different.

[0690] In one embodiment of the present disclosure, the first pattern and the second pattern have, with regard to the order of intervals of the Doppler shift amounts, the multiple first Doppler multiplexing intervals by the first transmitting antenna and the multiple Doppler multiplexing intervals by the second transmitting antenna are the same, and the order of the multiple Doppler multiplexing intervals by the first transmitting antenna on the Doppler frequency axis is different from the order of the multiple Doppler multiplexing interva...

Claims

1. a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmission antennas have been applied; Equipped with Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to the number of transmit antennas, the number of the first transmitting antennas is different from the number of the second transmitting antennas; Radar equipment.

2. a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmission antennas have been applied; Equipped with Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to a Doppler multiplex number, a Doppler multiplexing number using the first polarization is different from a Doppler multiplexing number using the second polarization; Radar equipment.

3. a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmission antennas have been applied; Equipped with Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to an order of intervals of the Doppler shift amounts, a plurality of first Doppler multiplexing intervals by the first transmitting antenna and a plurality of Doppler multiplexing intervals by the second transmitting antenna are the same, an order of the plurality of Doppler multiplexing intervals by the first transmitting antenna on the Doppler frequency axis is different from an order of the plurality of Doppler multiplexing intervals by the second transmitting antenna on the Doppler frequency axis; Radar equipment.

4. a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmission antennas have been applied; Equipped with Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; At least one of the Doppler multiplexing intervals by the first transmitting antenna and the Doppler multiplexing intervals by the second transmitting antenna is unequal on the Doppler frequency axis. Radar equipment.

5. the first pattern and the second pattern relate to the Doppler multiplexing interval, At least one of the Doppler multiplexing intervals of the first transmitting antenna is different from the Doppler multiplexing interval of the second transmitting antenna.

5. A radar device according to claim 1.

6. a receiving antenna that receives a reflected wave signal of the transmission signal reflected by a target using either the first polarized wave or the second polarized wave; and a direction estimation circuit that performs direction estimation based on the reflected wave signal.

5. A radar device according to claim 1.

7. a plurality of receiving antennas including a first receiving antenna using the first polarized wave and a second receiving antenna using the second polarized wave, the receiving antennas receiving reflected wave signals of the transmission signals reflected by a target; and a direction estimation circuit that performs direction estimation individually for the reflected wave signals received by the first receiving antenna and the second receiving antenna.

5. A radar device according to claim 1.

8. The timing at which the transmission signal is transmitted from the first transmission antenna is different from the timing at which the transmission signal is transmitted from the second transmission antenna.

5. A radar device according to claim 1.

9. the amount of Doppler shift assigned to the first transmitting antenna includes the same amount of Doppler shift as the amount of Doppler shift assigned to the second transmitting antenna; 5. A radar device according to claim 1.

10. a signal generating circuit that generates a transmission signal; a Doppler shift circuit that multiplexes the transmission signals from a plurality of transmission antennas, the transmission signals having phase rotations corresponding to Doppler shift amounts assigned to the plurality of transmission antennas; Equipped with the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to the number of transmit antennas, the number of the first transmitting antennas is different from the number of the second transmitting antennas; Radar signal generator.

11. a signal generating circuit that generates a transmission signal; a Doppler shift circuit that multiplexes the transmission signals from a plurality of transmission antennas, the transmission signals having phase rotations corresponding to Doppler shift amounts assigned to the plurality of transmission antennas; Equipped with the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to a Doppler multiplex number, a Doppler multiplexing number using the first polarization is different from a Doppler multiplexing number using the second polarization; Radar signal generator.

12. a signal generating circuit that generates a transmission signal; a Doppler shift circuit that multiplexes the transmission signals from a plurality of transmission antennas, the transmission signals having phase rotations corresponding to Doppler shift amounts assigned to the plurality of transmission antennas; Equipped with the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to an order of intervals of the Doppler shift amounts, a plurality of first Doppler multiplexing intervals by the first transmitting antenna and a plurality of Doppler multiplexing intervals by the second transmitting antenna are the same, an order of the plurality of Doppler multiplexing intervals by the first transmitting antenna on the Doppler frequency axis is different from an order of the plurality of Doppler multiplexing intervals by the second transmitting antenna on the Doppler frequency axis; Radar signal generator.

13. a signal generating circuit that generates a transmission signal; a Doppler shift circuit that multiplexes the transmission signals from a plurality of transmission antennas, the transmission signals having phase rotations corresponding to Doppler shift amounts assigned to the plurality of transmission antennas; Equipped with the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; At least one of the Doppler multiplexing intervals by the first transmitting antenna and the Doppler multiplexing intervals by the second transmitting antenna is unequal on the Doppler frequency axis. Radar signal generator.

14. the first pattern and the second pattern relate to the Doppler multiplexing interval, At least one of the Doppler multiplexing intervals of the first transmitting antenna is different from the Doppler multiplexing interval of the second transmitting antenna.

14. A radar signal generating device according to any one of claims 10 to 13.

15. generating a transmission signal; the transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the respective plurality of transmission antennas are applied are multiplexed and transmitted from the plurality of transmission antennas; 1. A method for generating a radar signal, comprising: the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to the number of transmit antennas, the number of the first transmitting antennas is different from the number of the second transmitting antennas; Radar signal generation method.

16. generating a transmission signal; the transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the respective plurality of transmission antennas are applied are multiplexed and transmitted from the plurality of transmission antennas; 1. A method for generating a radar signal, comprising: the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to a Doppler multiplex number, a Doppler multiplexing number using the first polarization is different from a Doppler multiplexing number using the second polarization; Radar signal generation method.

17. generating a transmission signal; the transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the respective plurality of transmission antennas are applied are multiplexed and transmitted from the plurality of transmission antennas; 1. A method for generating a radar signal, comprising: the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; the first pattern and the second pattern relate to an order of intervals of the Doppler shift amounts, a plurality of first Doppler multiplexing intervals by the first transmitting antenna and a plurality of Doppler multiplexing intervals by the second transmitting antenna are the same, an order of the plurality of Doppler multiplexing intervals by the first transmitting antenna on the Doppler frequency axis is different from an order of the plurality of Doppler multiplexing intervals by the second transmitting antenna on the Doppler frequency axis; Radar signal generation method.

18. generating a transmission signal; the transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the respective plurality of transmission antennas are applied are multiplexed and transmitted from the plurality of transmission antennas; 1. A method for generating a radar signal, comprising: the plurality of transmitting antennas include a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; Doppler multiplexing intervals by the plurality of transmitting antennas are unequal intervals on a Doppler frequency axis, a first pattern of Doppler shift amounts assigned to the first transmitting antenna is different from a second pattern of Doppler shift amounts assigned to the second transmitting antenna; At least one of the Doppler multiplexing intervals by the first transmitting antenna and the Doppler multiplexing intervals by the second transmitting antenna is unequal on the Doppler frequency axis. Radar signal generation method.

19. the first pattern and the second pattern relate to the Doppler multiplexing interval, At least one of the Doppler multiplexing intervals of the first transmitting antenna is different from the Doppler multiplexing interval of the second transmitting antenna.

19. A method for generating a radar signal according to any one of claims 15 to 18.

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