Radar device

Abstract

A radar device is provided with: a plurality of transmission antennas including a first transmission antenna that radiates a first polarized wave and a second transmission antenna that radiates a second polarized wave different from the first polarized wave; and a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, a transmission signal to which a phase rotation corresponding to each of the Doppler shift amounts allocated to each of the plurality of transmission antennas has been imparted, and that is non-equally spaced on the Doppler frequency axis on the basis of the Doppler multiplexing intervals of the plurality of transmission antennas. A first pattern of the Doppler shift amount allocated to the first transmission antenna is different from a second pattern of the Doppler shift amount allocated to the second transmission antenna.

Description

Technical Field

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

[0002] In recent years, research has been progressing on radar devices that use short-wavelength radars including microwaves or millimeter waves that can achieve high resolution to transmit signals. In addition, in order to improve safety when outdoors, it is required to develop radar devices that can detect not only vehicles but also small objects such as pedestrians within a wide angle range (for example, so-called wide-angle radar devices).

[0003] As a structure of a radar device with a wide-angle detection range, for example, there is a structure using the following method (arrival angle estimation method. Direction of Arrival (DOA) estimation), which receives the reflected wave from the target through an array antenna composed of multiple antennas (or also called antenna elements), and estimates the direction of arrival (also called arrival angle) of the reflected wave from the target based on the reception phase difference with respect to the element spacing (antenna spacing). For example, as an arrival angle estimation method, the Fourier method can be listed, or, as a method that can obtain high resolution, the Capon method, MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques, signal parameter estimation based on rotational invariance techniques) can be listed.

[0004] In addition, as a radar device, for example, the following structure has been proposed (sometimes also called "MIMO (Multiple Input Multiple Output) radar"): in addition to the receiving part, the transmitting part also has multiple antennas (array antennas), and beam scanning is performed by signal processing using the transmitting and receiving array antenna (for example, refer to non-patent document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: U.S. Patent Publication No. 2019 / 0064337

[0008] Patent Document 2: U.S. Patent Publication No. 2020 / 0363497

[0009] Patent Document 3: Japanese Patent Application Publication No. 2008-304417

[0010] Patent Document 4: Japanese Patent Application No. 2011-526371

[0011] Patent Document 5: Japanese Patent Application Publication No. 2011-119344

[0012] Patent Document 6: Japanese Patent Application Publication No. 2019-052952

[0013] Patent Document 7: Japanese Patent Application Publication No. 2020-148754

[0014] Non-patent literature

[0015] 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

[0016] Non-patent document 2: M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823

[0017] Non-patent literature 3: Direction-of-arrival estimation using signal subspacemodeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1 Publication Year: 1992, Page (s): 64-79 Summary of the invention

[0018] However, a method for detecting a target (or object) using a radar device (eg, MIMO radar) has not been fully studied.

[0019] The non-limiting embodiments of the present disclosure help provide a radar device that improves the detection accuracy of a target object.

[0020] 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, transmitting signals that are given phase rotations corresponding to Doppler frequency shift amounts assigned to the plurality of transmitting antennas, respectively, wherein a first pattern of the Doppler frequency shift amount assigned to the first transmitting antenna is different from a second pattern of the Doppler frequency shift amount assigned to the second transmitting antenna based on that the Doppler multiplexing intervals of the plurality of transmitting antennas are unequally spaced on the Doppler frequency axis.

[0021] In addition, these broad or specific embodiments may be implemented by systems, devices, methods, integrated circuits, computer programs or recording media, or by any combination of systems, devices, methods, integrated circuits, computer programs and recording media.

[0022] According to an embodiment of the present disclosure, the detection accuracy of a target object of a radar device can be improved.

[0023] Further advantages and effects in one embodiment of the present disclosure will be clearly presented by the description and the drawings. The above advantages and / or effects are provided by several embodiments and the features described in the description and the drawings, but not necessarily all of them are provided in order to obtain one or more of the same features. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram showing an example of time division multiplexing (TDM: Time Division Multiplexing) transmission.

[0025] Figure 2 This is a diagram showing an example of Doppler Division Multiplexing (DDM) transmission.

[0026] Figure 3 This is a diagram showing an example of unequal-interval Doppler multiplexing transmission.

[0027] Figure 4 This is a diagram showing an example of Doppler multiplexing transmission.

[0028] Figure 5 This is a block diagram showing a configuration example of a radar device.

[0029] Figure 6 This is a diagram showing an example of a transmission signal when a chirp signal is used.

[0030] Figure 7 This is a diagram showing an example of a chirp signal.

[0031] Figure 8 This is a diagram showing an example of a transmission signal and a reception signal when a chirp signal is used.

[0032] Fig. 9 It is a diagram showing an example of setting the Doppler shift amount.

[0033] Fig.10 This is a diagram showing an example of a reception signal transmitted by Doppler multiplexing.

[0034] Fig.11 It is a diagram showing an example of setting the Doppler shift amount.

[0035] Fig.12 This is a diagram showing an example of a reception signal transmitted by Doppler multiplexing.

[0036] Fig.13 It is a diagram showing an example of setting the Doppler shift amount.

[0037] Fig.14 It is a diagram showing an example of setting the Doppler shift amount.

[0038] Fig.15 It is a diagram showing an example of setting the Doppler shift amount.

[0039] Fig.16 It is a diagram showing an example of setting the Doppler shift amount.

[0040] Fig.17 This is a flowchart showing an example of the demultiplexing operation of a Doppler multiplexed signal.

[0041] Fig.18 This is a block diagram showing a configuration example of a radar receiving unit.

[0042] Fig.19 It is a diagram showing an example of setting the Doppler shift amount.

[0043] Fig. 20 It is a diagram showing an example of setting the Doppler shift amount.

[0044] Fig.21 It is a diagram showing an example of setting the Doppler shift amount.

[0045] Fig. 22 This is a block diagram showing a configuration example of a radar device. DETAILED DESCRIPTION

[0046] For example, MIMO radar transmits signals (radar transmission waves) multiplexed by time division, frequency division or code division from multiple transmission antennas (or, called "transmission array antennas"), receives signals (radar reflection waves) reflected by surrounding objects using multiple receiving antennas (or, called "receiving array antennas"), and demultiplexes and receives the multiplexed transmission signals from each received signal. Through this processing, MIMO radar can obtain the propagation path response represented by the product of the number of transmission antennas and the number of receiving antennas, and perform array signal processing on these received signals as a virtual receiving array. In addition, in MIMO radar, by appropriately configuring the element spacing in the transmission and reception array antenna, the antenna aperture of the virtual receiving array can be expanded and the angular resolution can be improved.

[0047] [About Polarimetric Radar]

[0048] In addition, there is a technology for improving radar detection performance or recognition performance by using, for example, antennas that radiate radio waves of different polarizations or antennas that receive radio waves of different polarizations (for example, see Patent Document 3 or Patent Document 4). Radar devices that use multiple polarized waves are also called "polarimetric radars".

[0049] For example, Patent Document 1 or Patent Document 2 discloses a method in which a transmission signal is transmitted using an antenna using a vertically polarized wave or a horizontally polarized wave, and an object is detected and identified using a signal received by the antenna using the vertically polarized wave or the horizontally polarized wave. In addition, Patent Document 2 discloses a method in which, for example, a transmission signal is transmitted using an antenna using a left-hand circularly polarized wave or a right-hand circularly polarized wave, and an object is detected and identified using a signal received by the antenna using the left-hand circularly polarized wave or the right-hand circularly polarized wave. In addition, an antenna using a linearly polarized wave such as a vertically polarized wave or a horizontally polarized wave, or a circularly polarized wave such as a left-hand circularly polarized wave or a right-hand circularly polarized wave is also referred to as a "polarized antenna."

[0050] Such a polarization radar uses a plurality of different kinds of polarization antennas (eg, polarization transmission antennas or polarization reception antennas).

[0051] Next, the multiplexing transmission method in a MIMO radar using a plurality of polarization antennas of different types (for example, also referred to as a “polarization MIMO radar”) will be described.

[0052] [About time division multiplexing transmission]

[0053] For example, as a multiplexing transmission method of MIMO radar using multiple transmission antennas, time division multiplexing (TDM) can be cited, which transmits signals by staggering the transmission time for each transmission antenna. Compared with frequency division multiplexing (FDM) and code division multiplexing (CDM), time division multiplexing can be implemented with a simpler structure, and by sufficiently expanding the transmission time interval, the orthogonality between the transmission signals can be well maintained.

[0054] For example, the MIMO radar using time division multiplexing transmission disclosed in Patent Document 3 sequentially switches the transmission antenna that transmits the transmission signal (e.g., transmission pulse or radar transmission wave) at a predetermined period, while outputting the transmission pulse as an example of the transmission signal. The MIMO radar using time division multiplexing transmission receives the signal obtained by the transmission pulse being reflected by an object using multiple receiving antennas, and performs spatial FFT (Fast Fourier Transform) processing (arrival direction estimation processing of the reflected wave) after correlation processing between the received signal and the transmission pulse.

[0055] In a MIMO radar using time division multiplexing transmission, a predetermined transmission time (or transmission interval) is pre-assigned to each of the multiple transmission antennas. Therefore, a polarization MIMO radar using time division multiplexing transmission receives reflections from the target object according to the transmission time assigned to each of the multiple transmission antennas with different polarizations, thereby demultiplexing and receiving the reflected waves from the target object corresponding to the transmission signals of each of the multiple transmission antennas with different polarizations.

[0056] Since the MIMO radar using time division multiplexing transmission sequentially switches the transmission antennas that transmit radar transmission waves at predetermined intervals, the time until transmission from all transmission antennas is completed tends to be longer than when frequency division multiplexing transmission or code division multiplexing transmission is used. Therefore, in the MIMO radar using time division multiplexing transmission, when multiple radar transmission waves are transmitted from each transmission antenna and Doppler frequency detection (for example, relative speed detection) is performed based on the received phase change of these transmission waves (for example, Patent Document 4). Figure 4 ), when Fourier frequency analysis is applied to detect Doppler frequency (for example, relative speed detection), the time interval for observing the reception phase change will be long. If the time interval for observing the reception phase change when Fourier frequency analysis is applied is long, it is easy to cause the maximum detectable Doppler frequency based on the sampling theorem to decrease, and the detectable Doppler frequency range (for example, relative speed range) to become smaller.

[0057] The following MIMO radar using time division multiplexing transmission is described. In this radar, for example, Figure 1 As shown, the transmission pulses are outputted while the transmission antennas (for example, Tx#1 and Tx#2) that transmit the chirp signal as the transmission radar wave are sequentially switched at the transmission cycle Tr.

[0058] For example, when there are Nt transmitting antennas ( Figure 1 In the case of Nt=2), the transmission time until the radar transmission wave from the Nt transmitting antennas is completed is Tr×Nt( Figure 1 In the case of , it is 2Tr). 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 perform Doppler frequency detection (for example, relative speed detection), then according to the sampling theorem, the Doppler frequency range in which the Doppler frequency can be detected without aliasing is ±1 / (2Tr×Nt). Therefore, the larger the number of transmitting antennas Nt, the smaller the Doppler frequency range in which the Doppler frequency can be detected without aliasing. In addition, in a MIMO radar using time division multiplexing transmission, when a Doppler frequency is received that exceeds the range in which the Doppler frequency can be detected without aliasing, it is difficult to uniquely determine the Doppler frequency (for example, relative speed), and ambiguity is likely to occur.

[0059] In the polarization radar using time division multiplexing transmission, similarly to the above-mentioned MIMO radar using time division multiplexing transmission, as the number of transmission antennas Nt increases, the Doppler frequency range in which the Doppler frequency can be detected without aliasing tends to decrease.

[0060] In the above, an example of time division multiplexing transmission has been described.

[0061] Next, as an example, attention will be paid to a method of multiplexing transmission signals and transmitting them simultaneously from a plurality of transmission antennas.

[0062] [About Doppler multiplexing transmission]

[0063] As a method of multiplexing and sending transmission signals simultaneously from multiple transmission antennas, there is, for example, a method of sending signals in a manner that allows a plurality of transmission signals to be demultiplexed in the Doppler frequency domain at a receiving unit (hereinafter referred to as "Doppler multiplexing (DDM) transmission") (for example, refer to Patent Document 5).

[0064] In Doppler multiplexing transmission, the transmitting unit, for example, gives phase rotations that bring different Doppler frequency shift amounts to the transmitted signals according to the transmitting antennas, and transmits the transmitted signals from multiple transmitting antennas simultaneously. In Doppler multiplexing transmission, the signals received by multiple receiving antennas (reflected waves from the target object) are filtered in the Doppler frequency domain, so that the transmitted signals sent from each transmitting antenna are demultiplexed and received.

[0065] In a MIMO radar using Doppler multiplexing transmission, for example, a predetermined Doppler frequency domain (or Doppler frequency shift amount) is pre-assigned to each of a plurality of transmitting antennas. For example, a polarization MIMO radar using Doppler multiplexing transmission receives reflections from a target object according to the Doppler frequency domains to which each of a plurality of transmitting antennas with different polarizations is assigned, thereby demultiplexing and receiving the reflected waves from the target object corresponding to the transmission signals of each of the plurality of transmitting antennas with different polarizations.

[0066] In a MIMO radar using Doppler multiplexing transmission, transmission signals are transmitted simultaneously from a plurality of transmission antennas, thereby making it possible to shorten the time interval for observing the reception phase change when detecting the Doppler frequency (e.g., relative speed detection) by applying Fourier frequency analysis, compared to time division multiplexing transmission. On the other hand, in a MIMO radar using Doppler multiplexing transmission, the transmission signals of each transmission antenna are demultiplexed by filtering on the Doppler frequency axis, so that the effective Doppler frequency bandwidth averaged to each transmission signal is limited.

[0067] The following MIMO radar using Doppler multiplexing transmission is described. In this radar, for example, Figure 2 As shown in (a) of FIG. 1 , the transmission of a chirp signal output as a transmission radar wave with a transmission period Tr is repeated Nc times, and Doppler frequency detection (for example, relative speed detection) is performed by applying Fourier frequency analysis.

[0068] For example, in Figure 2 In (b), according to the sampling theorem, the Doppler frequency range that can detect the Doppler frequency without aliasing on the Doppler frequency axis is ±1 / (2Tr), which is expanded to Nt times (in Figure 2 In the case of Nt=2). On the other hand, in a MIMO radar using Doppler multiplexing transmission, since the transmission signal is demultiplexed by filtering on the Doppler frequency axis, the effective Doppler frequency range averaged per transmission signal is smaller than the Doppler frequency range ±1 / (2Tr). For example, when Tx#1 and Tx#2 are each assigned a Doppler frequency range of ±1 / (2Tr) that is equally divided into Nt ( Figure 2In the case of Nt=2), when the Doppler shift (hereinafter also referred to as "Doppler shift amount" or "transmission Doppler shift amount") is 0 [Hz] and -1 / (2Tr) [Hz], the MIMO radar using Doppler multiplexing transmission multiplies the chirp signal (cp(t)) as the transmission signal by a phase rotation Φ1(n)=(n-1)ΔΦ1, Φ2(n)=(n-1)ΔΦ2 (where ΔΦ1=0, ΔΦ2=π) for each transmission period Tr. Here, n=1, 2, 3, 4, ..., and n is an index indicating the number of times the chirp signal is transmitted.

[0069] In this case, if Figure 2 As shown in (b), Doppler frequency domains are pre-allocated to multiple transmitting antennas Tx#1 and Tx#2. For example, -1 / (4Tr)≦fd1<1 / (4Tr) is allocated to the region of Doppler frequency fd1 of Tx#1 (for example, also called "Doppler division region"), and -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<-1 / (2Tr) are allocated to the region of Doppler frequency fd2 of Tx#2.

[0070] MIMO radar using Doppler multiplexing transmission, for example, receives the signal from each transmission antenna reflected by the target object, performs filtering on the Doppler frequency axis, and thus demultiplexes the transmission signal and receives it. Figure 2 In (b), the MIMO radar using Doppler multiplexing transmission filters and extracts the signal obtained by the transmission signal from the transmission antenna Tx#1 reflected at the target object in the range of -1 / (4Tr)≦fd1<1 / (4Tr) on the Doppler frequency axis, thereby demultiplexing and receiving. Similarly, the MIMO radar using Doppler multiplexing transmission filters and extracts the signal obtained by the transmission signal from the transmission antenna Tx#2 reflected at the target object in the range of -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<-1 / (2Tr) on the Doppler frequency axis, thereby demultiplexing and receiving.

[0071] Thus, in the MIMO radar using Doppler multiplexing transmission, the reception process is performed assuming that the reflected wave signals corresponding to the transmission signals from each transmission antenna are respectively included in the Doppler frequency range of ±1 / (2Tr×Nt), so the Doppler frequency range becomes the same as that when time division multiplexing transmission is performed. For example, in the MIMO radar using Doppler multiplexing transmission, the larger the number of transmission antennas Nt, the smaller the Doppler frequency range that can detect the Doppler frequency without aliasing.

[0072] In addition, in the polarization MIMO radar using Doppler multiplexing transmission, similarly to the above-mentioned MIMO radar using Doppler multiplexing transmission, as the number of transmission antennas Nt increases, the Doppler frequency range in which the Doppler frequency can be detected without aliasing tends to become smaller.

[0073] [About unequally spaced Doppler multiplexing transmission]

[0074] In the above-mentioned time division multiplexing transmission or Doppler multiplexing transmission, the reflected waves corresponding to the transmission signals from multiple transmitting antennas can be demultiplexed using the allocated transmission time or Doppler frequency domain. On the other hand, in time division multiplexing transmission and Doppler multiplexing transmission, if the number of transmitting antennas increases, the detection range of the Doppler frequency tends to become smaller. For example, in time division multiplexing and Doppler division multiplexing, the detectable Doppler frequency range is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr), and the detection range of the Doppler frequency decreases inversely proportional to the number of transmitting antennas. Here, Nt is the number of transmitting antennas.

[0075] For example, Patent Documents 6 and 7 are disclosed as methods for expanding the detection range of Doppler frequency in Doppler multiplexing transmission. Figure 4 ) discloses the following method. For example, in the Doppler frequency shift amounts (or Doppler frequency domain) obtained by equally dividing the Doppler frequency range ±1(2Tr) capable of detecting the Doppler frequency without aliasing into (Nt+1), Nt Doppler frequency shift amounts are allocated to Nt transmission signals, and the transmission signals are simultaneously transmitted from Nt transmission antennas.

[0076] In such Doppler multiplexing transmission, a part of the Doppler frequency shift amounts equally divided into (Nt+1) is not allocated to the transmission signal. Therefore, in the Doppler frequency domain, each interval of the Doppler frequency shift amount assigned to the transmission signal subjected to Doppler multiplexing (hereinafter also referred to as "Doppler multiplexing interval") is unequally spaced. Hereinafter, this type of Doppler multiplexing transmission is referred to as "unequally spaced Doppler multiplexing transmission (unequally spaced DDM)".

[0077] Figure 3 The following shows an example of allocating Doppler multiplexed signals using unequally spaced Doppler multiplexing transmission when a radar transmission wave (e.g., chirp signal) is transmitted at each transmission period Tr, using Nt=2 transmitting antennas and setting the unit of Doppler multiplexing interval to Δfd=1 / (3Tr).

[0078] exist Figure 3, the transmission Doppler shift amounts assigned to the transmission antennas Tx#1 and Tx#2 are Δfd1=0 and Δfd2=1 / (3Tr)[Hz], respectively. For example, in order to assign the transmission Doppler shift amount Δfd1 to the transmission antenna Tx#1 in each n-th transmission cycle, a phase rotation Φ1(n)=ΔΦ1×(n-1) is assigned to the radar transmission wave (chirp signal). Similarly, for example, in order to assign the transmission Doppler shift amount Δfd2 to the transmission antenna Tx#2 in each n-th transmission cycle, a phase rotation Φ2(n)=ΔΦ2×(n-1) is assigned to the radar transmission wave (chirp signal). In addition, no transmission antenna is assigned to the Doppler shift amount Δfd3 corresponding to the phase rotation Φ3(n)=ΔΦ3×(n-1).

[0079] Here, Figure 3 It represents the transmission Doppler frequency allocated to the transmission antennas Tx#1 and Tx#2 when Δfd1=0, Δfd2=1 / (3Tr), ΔΦ1=0, ΔΦ2=2π×Δfd×Tr=2π / 3. Figure 3 In the example, the transmission Doppler frequency when Δfd3 = 2 / (3Tr) and ΔΦ3 = 2π × 2Δfd × Tr = 4π / 3 (or -2π / 3) is indicated by the “×” mark. Figure 3 As shown, no transmission antenna is allocated for the Doppler frequency shift amount Δfd3.

[0080] In addition, the phase rotation Φ n It can also be expressed as -π≦ΔΦ n <π. For example, it can be expressed as ΔΦ3=-2π / 3. The same is true below.

[0081] For example, consider Figure 3 As shown in FIG. 1 , the Doppler multiplexing interval of Tx#1 and Tx#2 is Δfd=1 / (3Tr), and the range (region) of observable Doppler frequencies is -1 / (2Tr)≦fd<1 / Tr, and includes Doppler frequencies outside this range. For example, when the received Doppler frequency of the Doppler multiplexing signal of Tx#1 or Tx#2 exceeds 1 / (2Tr), or is less than -1 / (2Tr), as shown in FIG. Figure 3 As shown, the Doppler multiplexing interval for Tx#1 and Tx#2 is Δf alias =1 / Tr-Δfd=2 / 3Tr. In the following, when “Doppler multiplexing interval” or “Doppler frequency shift interval” is described, in addition to Δfd, Δf alias .

[0082] Next, an example of demultiplexing reception processing of Doppler multiplexed signals in the case of using unequal-interval Doppler multiplexing transmission will be described.

[0083] In the demultiplexing reception process of the Doppler multiplexed signal when the non-uniformly spaced Doppler multiplexed transmission is used, for example, the following properties are used to detect the Doppler frequency (for example, relative speed detection) of the received signal of the radar reflected wave.

[0084] For example, in the output to which Fourier frequency analysis is applied, among the Doppler frequency shift amounts equally divided into Nt+1, the received power level of the Doppler frequency corresponding to the Doppler frequency shift amount to which the transmission signal is not allocated is sufficiently lower than the received power level of the Doppler frequency corresponding to the Doppler frequency shift amount to which the transmission signal is allocated (for example, sufficiently low and as low as the noise level).

[0085] MIMO radar using non-uniformly spaced Doppler multiplexing transmission utilizes this property to estimate the reception Doppler frequency of reflected waves from target objects and perform demultiplexing processing of the transmission antennas.

[0086] For example, the reception Doppler frequency of the reflected wave from the target is set to "fd target In this case, the Doppler frequency fd is observed in the output of Doppler frequency detection (for example, relative speed detection) performed by applying Fourier frequency analysis to the radar reflected wave reception signal. target +Δfd1 and fd target The reception level of +Δfd2 is high (for example, above the threshold). On the other hand, in the output of Doppler frequency detection (for example, relative speed detection) using Fourier frequency analysis, the following is observed: target +Δfd1 and fd target +Δfd2 reception level compared to the Doppler frequency fd target The reception level of +Δfd3 is sufficiently low and is as low as the noise level.

[0087] In addition, in the output of Doppler frequency detection (for example, relative speed detection) performed by applying Fourier frequency analysis, observation is performed within the range of -1 / (2Tr)≦fd<1 / (2Tr). Therefore, when this range is exceeded, it will be observed as a signal aliased within -1 / (2Tr)≦fd<1 / (2Tr) in the output applied with Fourier frequency analysis.

[0088] If the received Doppler frequency fd of the reflected wave from the target target In -1 / (2Tr)≦fd target <1 / (2Tr), then the receiving Doppler frequency that satisfies the above relationship is -1 / (2Tr)≦fd target<1 / (2Tr) is unique, so the MIMO radar using non-uniformly spaced Doppler multiplexing can unambiguously determine the Doppler frequency fd of the target within this range. target MIMO radar using non-uniformly spaced Doppler multiplexing transmission, for example, determines the Doppler frequency fd corresponding to the target target In this case, the receiving Doppler frequency of each transmitting antenna can be determined, thereby enabling demultiplexing reception of Doppler multiplexed signals.

[0089] By adopting such demultiplexing reception processing of Doppler multiplexed signals, a MIMO radar using non-equally spaced Doppler multiplexing transmission can, for example, estimate the Doppler frequency of radar reflected waves in the Doppler frequency range of ±1 / (2Tr). By performing non-equally spaced Doppler multiplexing transmission, the detectable Doppler frequency range is expanded to ±1 / (2Tr). For example, by performing non-equally spaced Doppler multiplexing transmission, the detectable Doppler frequency range is expanded to Nt times compared to the method of Patent Document 3.

[0090] [About the application of non-uniformly spaced Doppler multiplexing transmission in polarization MIMO radar]

[0091] As described above, in non-equally spaced Doppler multiplexing, for example, unlike equally spaced Doppler multiplexing, a portion of the Doppler frequency domain is not allocated to the transmitted signal, and the MIMO radar performs demultiplexing processing on the Doppler multiplexed signal that estimates the Doppler frequency of the target based on the received power of the received Doppler frequency of the reflected wave from the target.

[0092] Therefore, when non-equally spaced Doppler multiplexing is applied to polarization MIMO radar, the following situation can be envisioned.

[0093] In polarization MIMO radar, for example, a phenomenon may occur in which the reception level of reflected waves varies greatly depending on the polarization of the transmitting and receiving antennas. In polarization MIMO radar, when using transmitting antennas of different polarizations, the reception level of reflected waves from transmitting antennas of other polarizations may be greatly attenuated relative to the reception level of reflected waves from transmitting antennas of a certain polarization. Therefore, in polarization MIMO radar, when multiplexing transmission is performed using unequally spaced Doppler multiplexing, if the difference in the reception level of reflected waves between transmitting antennas of different polarizations is large, demultiplexing of Doppler multiplexing based on unequally spaced Doppler multiplexing becomes difficult. If demultiplexing of Doppler multiplexing becomes difficult, degradation of the detection performance of the target object in the MIMO radar, demultiplexing errors of Doppler multiplexing, Doppler misestimation, or degradation of the angle measurement performance may occur.

[0094] Next, an example in which demultiplexing of Doppler multiplexing is difficult in a polarization MIMO radar to which non-uniformly spaced Doppler multiplexing is applied will be described.

[0095] Here, as an example, a case where two transmitting antennas are used for each of left-hand circular polarization (hereinafter, also expressed as "LC") and right-hand circular polarization (hereinafter, also expressed as "RC") to form a MIMO radar (expressed as LC-2Tx and RC-2Tx, respectively) is described (for example, the number of transmitting antennas Nt=4). The polarized antenna corresponding to left-hand circular polarization is called an "LC polarized antenna" (for example, an LC polarized transmitting antenna or an LC polarized receiving antenna), and the polarized antenna corresponding to right-hand circular polarization is called an "RC polarized antenna" (for example, an RC polarized transmitting antenna or an RC polarized receiving antenna).

[0096] For example, the case where a MIMO radar uses an LC polarized receiving antenna to receive a primary reflected wave (a reflected wave that is reflected once by an object) is described. In this case, the reflected wave signal corresponding to the transmitted signal from the RC polarized transmitting antenna (for example, also referred to as "the received signal corresponding to the RC polarized transmitting antenna") becomes a received signal as an RC polarized wave, and when the received signal corresponding to the RC polarized transmitting antenna is received by the LC polarized receiving antenna, it becomes reception under cross-polarization. Therefore, in the LC polarized receiving antenna, the received signal corresponding to the RC polarized transmitting antenna becomes a smaller received level (depending on the cross-polarization discrimination of the antenna, for example, a received level that is 10 dB or more smaller) than the received level of the reflected wave signal corresponding to the transmitted signal from the LC polarized transmitting antenna (for example, also referred to as "the received signal corresponding to the LC polarized transmitting antenna"). For example, depending on the reception quality (eg, signal to noise ratio (SNR)), the reception level of the reception signal corresponding to the RC polarized transmission antenna may become lower than the noise level, making it difficult to detect the Doppler frequency peak in the MIMO radar.

[0097] Figure 4 This is a diagram showing an example of a signal transmitted by Doppler multiplexing in a polarization MIMO radar. Figure 4 In the figure, "L" is used to represent the signal allocated to the LC polarized transmitting antenna, and "R" is used to represent the signal allocated to the RC polarized transmitting antenna.

[0098] For example, in Figure 4 When the Doppler multiplexing signal is distributed as shown in (a), the LC polarized receiving antenna may have the following when receiving the primary reflected wave: Figure 4As shown in (b), the reception level of the reception signal (R) corresponding to the RC polarized transmission antenna is smaller than that of the reception signal (L) corresponding to the LC polarized transmission antenna.

[0099] In addition, the case where the MIMO radar uses an LC polarized receiving antenna to receive, for example, a secondary reflected wave (a reflected wave that is reflected twice by an object) is described. In this case, since the received signal corresponding to the LC polarized transmitting antenna received in the LC polarized receiving antenna is a secondary reflection, the received signal changes from an LC polarized wave to an RC polarized wave, and when received by the LC polarized receiving antenna, it becomes a reception under cross polarization, so the level of the received signal corresponding to the LC polarized transmitting antenna becomes a smaller receiving level (depending on the cross polarization discrimination of the antenna, for example, a receiving level that is 10 dB or more smaller) than the received signal corresponding to the RC polarized transmitting antenna. For example, depending on the reception quality (SNR), the reception level of the received signal corresponding to the LC polarized transmitting antenna may become below the noise level, making it difficult to detect the Doppler frequency peak in the MIMO radar.

[0100] For example, in Figure 4 When the Doppler multiplexing signal is distributed as shown in (a), the LC polarized receiving antenna may have the following problems when receiving the secondary reflected wave: Figure 4 As shown in (c), the reception level of the reception signal (L) corresponding to the LC polarized transmission antenna is smaller than that of the reception signal (R) corresponding to the RC polarized transmission antenna.

[0101] Here, it is difficult for MIMO radar to know the number of reflections in advance, for example, Figure 4 The reception level shown in (b) or (c) of FIG. 1 can be used to determine whether the reception level of the reception signal corresponding to the RC polarized transmission antenna has decreased or the reception level of the reception signal corresponding to the LC polarized transmission antenna has decreased. In addition, for example, it is difficult for MIMO radar to Figure 4 The received level shown in (b) or (c) is used to determine which transmission antenna used in the non-uniformly spaced Doppler multiplexing transmission corresponds to the peak value of the detected Doppler frequency. Therefore, it is difficult for the MIMO radar to demultiplex the Doppler multiplexing signal and to determine the Doppler frequency fd of the reflected wave from the target (e.g., "target reflected wave") within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0102] Similarly, in Figure 4 When the Doppler multiplexed signal is distributed as shown in (d) of FIG. 1 , when the MIMO radar uses the LC polarized receiving antenna to receive the primary reflected wave, as shown in FIG. Figure 4As shown in (e), since the received signal (R) corresponding to the RC polarized transmitting antenna is an RC polarized wave, its received level is a smaller received level (depending on the cross-polarization discrimination of the antenna and, for example, a received level that is 10 dB or more smaller) than the received signal (L) corresponding to the LC polarized transmitting antenna which is an LC polarized wave.

[0103] In addition, when the MIMO radar uses an LC polarized receiving antenna to receive secondary reflected waves, such as Figure 4 As shown in (f), since the received signal (L) corresponding to the LC polarized transmitting antenna is an RC polarized wave, its received level is a smaller received level (depending on the cross-polarization discrimination of the antenna and, for example, a received level that is 10 dB or more smaller) than the received signal (R) corresponding to the RC polarized transmitting antenna which is an LC polarized wave.

[0104] exist Figure 4 In (e) and (f), depending on the reception quality (SNR), the received signal with a reduced reception level may become below the noise level, making it difficult to detect the Doppler frequency peak in the MIMO radar. In addition, it is difficult for the MIMO radar to detect the Doppler frequency peak based on, for example, Figure 4 The reception level shown in (e) or (f) of FIG. 1 can be used to determine whether the reception level of the transmission signal from the RC polarized transmission antenna has decreased or the reception level of the transmission signal from the LC polarized transmission antenna has decreased. Therefore, it is difficult for the MIMO radar to demultiplex the Doppler multiplexed signal and determine the Doppler frequency fd of the target reflection wave within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0105] As described above, in the non-uniformly spaced Doppler multiplexing, the demultiplexing process of the Doppler multiplexing is performed on the premise that: Figure 4 As shown in (a), the reception level of each transmitting antenna is about the same, and the reception level of the Doppler multiplexing interval (× mark) that is not Doppler multiplexing is sufficiently low and is as low as the noise level. In the polarization MIMO radar using unequal interval Doppler multiplexing, sometimes Figure 4 As shown in (b), (c), (e) or (f), the premise of the demultiplexing processing of non-uniformly spaced Doppler multiplexing does not hold, resulting in possible errors in the demultiplexing processing of Doppler multiplexing.

[0106] In a non-limiting embodiment of the present disclosure, a method for improving the detection performance of a polarization MIMO radar using non-equally spaced Doppler multiplexing transmission is described.

[0107] In addition, an example is described here in which a MIMO radar is constructed using two transmitting antennas for each of left-hand circular polarization (LC) and right-hand circular polarization (RC) (for example, the number of transmitting antennas Nt=4), but the polarization used in the polarization MIMO radar is not limited to this.

[0108] For example, in polarization MIMO radar, different linear polarizations that are orthogonal to each other can also be applied. For example, vertical polarization can be applied instead of left-hand circular polarization (LC), and horizontal polarization can be applied instead of right-hand circular polarization (RC), that is, linear polarizations that are orthogonal to each other can be applied. When radar transmission waves are transmitted using such vertically polarized and horizontally polarized transmitting antennas, the closer the incident angle of the radar transmission wave when it is reflected at the target is to the Brewster angle, the more likely it is that the reflected wave of one of the vertical polarization and horizontal polarization has a weaker reception level than the reflected wave of the other polarization. In MIMO radar, for example, when such reflected waves are received using a polarization receiving antenna corresponding to one of the vertical polarization and horizontal polarization, it is possible that the received signal of the polarization transmitting antenna corresponding to one of the vertical polarization and horizontal polarization becomes a reception under cross polarization, so that the received level is a lower received level (depending on the cross polarization discrimination of the antenna and being, for example, a reception level that is 10 dB or more lower) than the received signal of the polarization transmitting antenna corresponding to the other. Depending on the reception quality (SNR), a received signal whose reception level has been reduced may fall below the noise level, making it difficult to detect a Doppler frequency peak in a MIMO radar.

[0109] For example, when vertical polarization is applied instead of left-hand circular polarization (LC), and horizontal polarization is applied instead of right-hand circular polarization (RC), Figure 4 When the Doppler multiplexing signal is allocated as in (a), it is possible to Figure 4 (b) or Figure 4 In addition, for example, when vertical polarization is applied instead of left-hand circular polarization (LC) and horizontal polarization is applied instead of right-hand circular polarization (RC), in the case of Figure 4 When the Doppler multiplexing signal is allocated as in (d), it is possible to Figure 4 (e) or Figure 4 The received signal is like that of (f).

[0110] The same is true when using vertically polarized and horizontally polarized transmitting antennas. For example, it is difficult for MIMO radar to Figure 4The reception level shown in (b), (c), (e) or (f) is used to determine whether the reception level of the transmission signal sent by the horizontal polarization transmission antenna has decreased or the reception level of the transmission signal sent by the vertical polarization transmission antenna has decreased. Therefore, it is difficult for the MIMO radar to demultiplex the Doppler multiplexed signal and determine the Doppler frequency fd of the target reflection wave in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0111] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the embodiments, the same components are given the same reference numerals, and their descriptions are omitted to avoid duplication.

[0112] The following describes a structure (for example, a MIMO radar structure) in which a radar device simultaneously sends out different multiplexed transmission signals from a plurality of transmission antennas in a transmission branch, and demultiplexes each transmission signal in a reception branch to perform reception processing.

[0113] In addition, as an example, the following describes a radar method that uses a frequency-modulated pulse wave such as a chirp pulse (for example, also referred to as "fast chirp modulation"). However, the modulation method is not limited to frequency modulation. For example, one embodiment of the present disclosure may also be applied to a radar method that uses a pulse compression radar that transmits a pulse train by phase modulation or amplitude modulation.

[0114] In addition, the radar device performs, for example, Doppler multiplexing transmission (for example, non-uniformly spaced Doppler multiplexing transmission). In addition, the radar device may include, for example, a polarized antenna.

[0115] [Structure of radar device]

[0116] Figure 5 The radar device 10 includes a radar transmitting unit (transmitting branch) 100 and a radar receiving unit (receiving branch) 200 .

[0117] The radar transmitting unit 100 generates a radar signal (radar transmission signal), and transmits the radar transmission signal at a predetermined transmission cycle (eg, referred to as a “radar transmission cycle”) using a transmission antenna unit 105 including a plurality of transmission antennas (eg, Nt).

[0118] The radar receiving unit 200 receives the radar transmission signal reflected by the target (target, not shown) using the receiving antenna unit 202 including a plurality of receiving antennas, that is, the reflected wave signal. The radar receiving unit 200 performs signal processing on the reflected wave signal received by each receiving antenna of the receiving antenna unit 202, for example, detecting the presence of the target, or estimating the arrival distance, Doppler frequency (for example, relative speed), and arrival direction of the reflected wave signal, and outputs information related to the estimation result (for example, positioning information).

[0119] In addition, the radar device 10 can be mounted on a mobile object such as a vehicle, and the positioning output from the positioning output unit 300 (for example, information related to the estimation result) can also be connected to a control device ECU (Electronic Control Unit) (not shown) such as an advanced driver assistance system (ADAS) or an automatic driving system that improves collision safety, for vehicle drive control or alarm call control.

[0120] In addition, the radar device 10 can be installed on a higher structure such as a roadside electric pole or a traffic light (not shown). In addition, the radar device 10 can also be used as a sensor in an auxiliary system for improving the safety of passing vehicles or pedestrians or a system to prevent suspicious people from breaking into the road (not shown). In addition, the positioning output of the radar receiving unit 200 can also be connected to a control device (not shown) in an auxiliary system for improving safety or a system to prevent suspicious people from breaking into the road, for example, for alarm call control or abnormality detection control. In addition, the use of the radar device 10 is not limited to this, and it can also be used for other purposes.

[0121] The target object is an object to be detected by the radar device 10 , and includes, for example, a vehicle (including four-wheeled and two-wheeled vehicles), a person, a rock, a curb, and the like.

[0122] [Configuration of Radar Transmitting Unit 100]

[0123] The radar transmitting unit 100 includes a radar transmission signal generating unit 101 , a Doppler frequency shifting unit 104 , and a transmitting antenna unit 105 .

[0124] The radar transmission signal generating unit 101 generates a radar transmission signal. The radar transmission signal generating unit 101 includes, for example, a modulation signal generating unit 102 and a VCO (Voltage Controlled Oscillator) 103. Hereinafter, each component of the radar transmission signal generating unit 101 will be described.

[0125] The modulation signal generation unit 102 periodically generates a sawtooth-shaped modulation signal, for example.

[0126] The VCO 103 generates a frequency modulation signal (hereinafter, for example, referred to as a frequency chirp signal or a chirp signal) based on the modulation signal input from the modulation signal generator 102. Figure 6 The radar transmission signal (radar transmission wave) shown is output to the Doppler frequency shift unit 104 and the radar receiving unit 200 (mixer unit 204 described later).

[0127] In the following, the modulation signal generator 102 generates a modulation signal so that the chirp signal is transmitted Nc times in each transmission cycle Tr in one radar positioning. The VCO 103 outputs the chirp signal Nc times in each transmission cycle Tr according to the operation of the modulation signal generator 102.

[0128] The radar device 10 can detect temporal variation in the position of the target object by, for example, performing radar positioning a plurality of times.

[0129] In addition, below, each transmission cycle in the Nc transmission cycles Tr is represented by an index "m". Here, m=1 to Nc.

[0130] Figure 7 An example of a chirp signal output from the radar transmission signal generation unit 101 is shown.

[0131] like Figure 7 As shown, the modulation parameters associated with the chirp signal may include, for example, the center frequency f c , Frequency scanning bandwidth B w , Scan start frequency f cstart , scan end frequency f cend , frequency scanning time T sw And the frequency sweep rate D m In addition, D m =B w / T sw In addition, B w =f cend -f cstart , and f c =(f cstart +f cend ) / 2.

[0132] In addition, the frequency sweep time T sw For example, it corresponds to the time range (or “range gate”) during which the AD (Analog Digital) converter 207 of the radar receiver 200 described later acquires A / D sample data. sw For example, Figure 7 As shown in (a) of FIG. 1 , the entire interval of the chirp signal can also be set as Figure 7As shown in (b), the interval is set as a part of the chirp signal.

[0133] In addition, Figure 6 and Figure 7 , an example of an up-chirp waveform in which the modulation frequency gradually increases over time is shown, but the present invention is not limited thereto, and a down-chirp waveform in which the modulation frequency gradually decreases over time may also be applied. Regardless of whether the modulation frequency is up-chirp or down-chirp, the same effect can be obtained.

[0134] The chirp signal output from the radar transmission signal generation unit 101 is input to each of the Nt Doppler frequency shift units 104. In addition, the chirp signal is also input to each of the mixer units 204 of the radar reception unit 200.

[0135] The n-th Doppler frequency shift unit 104 is used to give a Doppler frequency shift amount DOP to the chirp signal input from the radar transmission signal generation unit 101. n , giving a phase rotation Φ according to the transmission period Tr of the chirp signal n (m). The nth Doppler frequency shift unit 104 gives a phase rotation Φ n The chirp signal (m) is output to the nth transmission antenna (for example, Tx#n) of the transmission antenna unit 105. Here, n=1 to Nt.

[0136] 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 at least two transmitting antennas with different polarizations (polarized transmitting antennas) to form a polarimetric radar. For example, the Doppler frequency shift unit 104 may give a phase rotation Φ with different Doppler frequency shift amounts to the chirp signal according to the structure of the transmitting antennas with different polarizations in the transmitting antenna unit 105, according to the transmitting antennas that transmit the chirp signal. n (m), and outputs it to the transmission antenna unit 105. Thus, even when the reception levels of the reception signals corresponding to the transmission antennas with different polarizations are greatly different (for example, when the reception level difference is equal to or greater than the threshold), the radar device 10 can demultiplex the Doppler multiplexed signal, and can reduce the degradation of the positioning performance and the radar detection performance (an operation example will be described later).

[0137] The outputs from the Nt Doppler frequency shift units 104 are amplified to predetermined transmission power and then radiated into space from the transmission antennas Tx# 1 to Tx#Nt of the transmission antenna unit 105 .

[0138] [Configuration of the radar receiving unit 200]

[0139] exist Figure 5In the embodiment, the radar receiving unit 200 includes a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. In addition, the radar receiving unit 200 includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 210, a Doppler multiplexing and demultiplexing unit 211, and a direction estimation unit 212.

[0140] The receiving antennas Rx# 1 to RxNa of the receiving antenna unit 202 receive reflected wave signals, which are radar transmission signals reflected by a target object (object), and output the received reflected wave signals to the corresponding antenna system processing unit 201 as received signals.

[0141] Each antenna system processing unit 201 includes a reception radio unit 203 and a signal processing unit 206 .

[0142] Each signal received by Na receiving antennas Rx#1 to Rx#Na is output to Na receiving wireless units 203. In addition, output signals from Na receiving wireless units 203 are output to Na signal processing units 206, respectively.

[0143] The receiving wireless 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 the chirp signal input from the radar transmission signal generating unit 101. The receiving wireless unit 203, for example, passes the output of the mixer unit 204 through the LPF 205. As a result, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is output. For example, Figure 8 As shown, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulation wave) as the transmission signal (radar transmission wave) and the frequency of the reception chirp signal (reception frequency modulation wave) as the reception signal (radar reflection wave) is obtained as the beat frequency.

[0144] The signal processing unit 206 in each antenna system processing unit 201 - z (where z=any one of 1 to Na) includes an AD conversion unit 207 , a beat frequency analysis unit 208 , and a Doppler analysis unit 209 .

[0145] The signal (for example, the beat signal) output from the LPF 205 is converted into discrete sample data by the AD converter 207 in the signal processing unit 206 through discrete sampling.

[0146] The beat frequency analysis unit 208 analyzes the N signals obtained within a predetermined time range (range gate) according to the transmission period Tr. dataThe signal processing unit 206 performs frequency analysis processing (e.g., FFT processing) on ​​discrete sample data. As a result, the signal processing unit 206 outputs a frequency spectrum having a peak at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). In addition, when performing FFT processing, the beat frequency analysis unit 208 may also multiply the window function coefficients such as the Han window or the Hamming window. By using the window function coefficients, the side lobes generated around the peak of the beat frequency can be suppressed.

[0147] In addition, in N data When it 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 this case, by considering the data size including zero-padded data as N data , can be processed in the same way as above.

[0148] Here, the beat frequency response obtained by transmitting the m-th chirped pulse and outputted from the beat frequency analysis unit 208 in the z-th signal processing unit 206 is represented by “RFT z (f b , m)”. Here, f b represents the beat frequency index, which corresponds to the index (bin number) of the FFT. b =0, ..., (N data / 2)-1, z=1~Na, m=1~N C . Beat frequency index f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (for example, the closer the distance to the target object).

[0149] In addition, the beat frequency index f b It can be converted into distance information R(f b ). Therefore, in the following, the beat frequency index f b It is called the “distance index f b ”.

[0150] [Formula 1]

[0151]

[0152] Here, B w represents the frequency modulation bandwidth within the range gate of the chirp signal, and C0 represents the speed of light. In addition, in formula (1), C0 / (2B w ) represents the distance resolution.

[0153] The Doppler analysis unit 209 in the z-th signal processing unit 206 uses the data of the Nc transmission cycles of the chirp signal (for example, the beat frequency response RFT input from the beat frequency analysis unit 208) to analyze the chirp signal. z (fb ,1),RFT z (f b , 2), ..., RFT z (f b , Nc)), for each distance index f b Doppler analysis was performed.

[0154] For example, when Nc is a power of 2, the Doppler analysis unit 209 can apply FFT processing to the Doppler analysis as shown in the following equation (2).

[0155] [Formula 2]

[0156]

[0157] Here, the FFT size is Nc, and the maximum Doppler frequency that does not cause aliasing is ±1 / (2Tr) according to the sampling theorem. In addition, the Doppler frequency index f s The Doppler frequency interval is 1 / (Nc×Tr), and the Doppler frequency index f s The range is f s = -Nc / 2, ..., 0, ..., (Nc / 2) - 1. In addition, j is an imaginary unit, and z = 1 to Na.

[0158] As an example, the case where Nc is a power of 2 is described below. In addition, when Nc is not a power of 2, for example, by including zero-filled data, FFT processing can be performed with a power of 2 as the data size (FFT size). In addition, when performing FFT processing, the Doppler analysis unit 209 can also multiply the window function coefficient such as the Hanning window or the Hamming window. By applying the window function, the side lobes generated around the Doppler frequency peak can be suppressed.

[0159] The above describes the processing in each component of the signal processing unit 206.

[0160] exist Figure 5 In the CFAR processing, the CFAR unit 210 uses the outputs of the Doppler analysis units 209 of the first to Nath signal processing units 206 to perform CFAR processing (for example, adaptive threshold determination). For example, in the CFAR processing, the local peak of the reflected wave reception signal of the radar transmission signal sent from the transmission antenna unit 105 can be selectively extracted to perform adaptive threshold determination. The CFAR unit 210 extracts, for example, the distance index f that gives the local peak signal. b_cfar and the Doppler frequency index f s_cfar , and output to the Doppler multiplexing and demultiplexing unit 211.

[0161] The Doppler multiplexing and demultiplexing unit 211 uses, for example, the output of the Doppler analysis unit 209 of the 1st to Nath signal processing units 206 and the output of the CFAR unit 210 to demultiplex the radar reflected wave reception signals of each radar transmission signal sent from multiple transmitting antennas using Doppler multiplexing (hereinafter referred to as "Doppler multiplexing demultiplexing").

[0162] In addition, for example, the operation of the Doppler multiplexing and demultiplexing unit 211 is associated with the operation of the Doppler frequency shift unit 104 of the radar transmitting unit 100. Similarly, for example, the operation of the CFAR unit 210 is associated with the operation of the Doppler frequency shift unit 104. Below, an operation example of the Doppler frequency shift unit 104 is described, and then an operation example of the CFAR unit 210 and an operation example of the Doppler multiplexing and demultiplexing unit 211 are described.

[0163] [Operation Example of Doppler Shifter 104 in Radar Transmitter 100]

[0164] For example, the first to Ntth Doppler shift units 104 give different Doppler shift amounts DOP to the radar transmission signals input thereto. n Doppler multiplexing transmission is performed.

[0165] In addition, an example in which a chirp signal is used as a radar transmission signal will be described below.

[0166] For example, the n-th Doppler frequency shift unit 104 provides a predetermined Doppler frequency shift amount DOP to the n-th transmission antenna Tx#n. n , and a phase rotation Φ is given according to the transmission period Tr of the input chirp signal n Here, the Doppler frequency shift unit 104 may provide a phase rotation φ that causes a different Doppler frequency shift to the chirp signal for each transmitting antenna that transmits the chirp signal. n (m) and output. Here, n = 1 to Nt. For example, the phase rotation Φ given to each transmission period Tr of the chirp signal n (m) can use Φ n (m)=2πDOP n ×Tr to set.

[0167] For example, the transmitting antennas Tx#1 to Tx#Nt of the transmitting antenna unit 105 include at least two transmitting antennas of different polarizations to form a polarimetric radar. For example, as different polarizations, the transmitting antennas Tx#1 to Tx#Nt may include transmitting antennas in a mutually orthogonal polarization relationship. In addition, there may be multiple transmitting antennas for at least one of the multiple polarizations, and there may be at least one transmitting antenna for the other polarizations.

[0168] The radar device 10 may be, for example, a polarization MIMO radar using Nt transmission antennas Tx#1 to Tx#Nt including transmission antennas of different polarizations. The radar device 10 may perform unequally spaced Doppler multiplexing transmission using Nt transmission antennas Tx#1 to Tx#Nt.

[0169] Furthermore, the radar device 10 may employ Doppler multiplexing transmission that satisfies the following conditions 1 and 2, for example, and may perform simultaneous multiplexing transmission of radar transmission signals from Nt transmission antennas Tx#1 to Tx#Nt.

[0170] In the following description, the first polarization among the plurality of polarizations used in the polarization radar is described as "PL1 polarization", and the second polarization is described as "PL2 polarization". In addition, for example, the qth polarization is described as "PLq polarization". As a combination of different polarizations in a mutually orthogonal polarization relationship, for example, right-hand circular polarization and left-hand circular polarization, horizontal polarization and vertical polarization, or right slant 45° polarization and left slant 45° polarization can be used as PL1 polarization and PL2 polarization in the combination.

[0171] In addition, let the number of transmission antennas Nt ≥ 3. For example, let the number of Doppler multiplexing N DDM ≧3.

[0172] In addition, it is assumed that the number of transmission antennas corresponding to PL1 polarization (for example, referred to as “PL1 polarization transmission antennas”) in the transmission antenna unit 105 is N. PL1 , the number of transmitting antennas corresponding to PL2 polarization (eg, referred to as “PL2 polarization transmitting antennas”) is N PL2 In this case, N PL1 +N PL2 =Nt.

[0173] <Condition 1>

[0174] Doppler multiplexing signals are allocated to PL1 polarization and PL2 polarization respectively in such a manner as to achieve the following non-uniformly spaced Doppler multiplexing:

[0175] Non-uniformly spaced Doppler multiplexing based on PL1 polarized transmitting antennas (it should be noted that in N PL1 ≧2, in N PL1 =1, no need to consider)

[0176] Non-uniformly spaced Doppler multiplexing based on PL2 polarized transmitting antennas (it should be noted that in N PL2 ≧2, in N PL2 =1, no need to consider)

[0177] <Condition 2>

[0178] Between the Doppler multiplexed signals respectively allocated to the PL1 polarized transmission antenna and the PL2 polarized transmission antenna, any one of the following conditions is satisfied.

[0179] (1) Contains different Doppler frequency shift intervals.

[0180] (2) The Doppler multiplexing number (= number of transmitting antennas) of each polarization is different (N PL1 ≠N PL2 ).

[0181] (3) In N PL1 ≧3, N PL2 In the case of ≧3, when the Doppler shift intervals of each polarization include the same Doppler shift interval, the order of the Doppler shift intervals is different.

[0182] For example, according to condition 1, the intervals of the Doppler frequency shift amounts assigned to the PL1 polarized transmission antenna are set to be unequal intervals on the Doppler frequency axis. Similarly, according to condition 1, the intervals of the Doppler frequency shift amounts assigned to the PL2 polarized transmission antenna are set to be unequal intervals on the Doppler frequency axis.

[0183] In addition, for example, according to condition 2 (1), the intervals of Doppler frequency shift amounts assigned to the PL1 polarized transmission antenna (Doppler frequency shift interval or Doppler multiplexing interval) may include intervals different from the intervals of Doppler frequency shift amounts assigned to the PL2 polarized transmission antenna. As examples of condition 2 (1), there may be a case where the maximum Doppler frequency shift interval is different between the Doppler multiplexing signals assigned to the PL1 polarization and the PL2 polarization, a case where the minimum Doppler frequency shift interval is different, or a case where the Doppler frequency shift interval that is neither the maximum nor the minimum is different.

[0184] As an example of condition 2 (2), there is a case where one of the PL1 polarized transmission antenna and the PL2 polarized transmission antenna is used as one to form a SIMO (Single-Input Multiple Output) radar structure (N PL1 =1 and N PL2 ≧2, or N PL1 ≧2 and N PL2 = 1), and the case where there are more than two PL1 polarized transmission antennas and two PL2 polarized transmission antennas, and the MIMO radar structure is formed by each polarized transmission antenna (N PL1 ≧2 and N PL2 ≧2).

[0185] In addition, if according to condition 2 (3), for example, the values ​​of the intervals of Doppler frequency shift amounts assigned to the PL1 polarized transmitting antenna and the PL2 polarized transmitting antenna (for example, the combination of Doppler frequency shift intervals) are the same, while the order of the intervals of Doppler frequency shift amounts assigned to the PL1 polarized transmitting antenna in the Doppler frequency range is different from the order of the intervals of Doppler frequency shift amounts assigned to the PL2 polarized transmitting antenna.

[0186] For example, the combination of intervals contained in a sequence (for example, a first sequence) in which the intervals of the Doppler frequency shift amounts allocated to the PL1 polarized transmitting antenna are arranged in sequence from the smaller side on the Doppler frequency axis is consistent with the combination of intervals contained in a sequence (for example, a second sequence) in which the intervals of the Doppler frequency shift amounts allocated to the PL2 polarized transmitting antenna are arranged in sequence from the smaller side on the Doppler frequency axis, and the first sequence and the second sequence are different sequences when arranged in a circle.

[0187] When condition 2 (3) is satisfied, even if one of the Doppler shift interval of the PL1 polarized antenna and the Doppler shift interval of the PL2 polarized antenna is cyclically shifted in the Doppler frequency domain, the two will not match.

[0188] Thus, in the non-equally spaced Doppler multiplexing transmission of the radar device 10 which is a polarization radar, in the Doppler frequency range of the Doppler analysis target, the intervals of the Doppler frequency shift amounts allocated to the plurality of transmission antennas included in the transmission antenna unit 105 are non-equally spaced. In addition, for example, among the plurality of transmission antennas included in the transmission antenna unit 105, the intervals of the Doppler frequency shift amounts allocated to the corresponding transmission antennas of the plurality of polarizations are non-equally spaced (condition 1). In addition, for example, in the Doppler frequency range of the Doppler analysis target, the pattern of the Doppler frequency shift amounts allocated to the PL1 polarization transmission antenna and the PL2 polarization transmission antenna (for example, a pattern related to the interval of the Doppler frequency shift amount, the number of transmission antennas (Doppler multiplexing number), or the order of the interval of the Doppler frequency shift amount on the Doppler frequency axis) is different (condition 2).

[0189] Therefore, even if the reception power levels of reflected waves differ greatly between reception signals corresponding to transmission antennas with different polarizations, the radar device 10 can demultiplex the Doppler multiplexed signal in this case, thereby suppressing the degradation of positioning performance and radar detection performance.

[0190] In addition, the Doppler analysis unit 209 performs Doppler frequency analysis on the output of the beat frequency analysis unit 208 of each distance index according to the transmission period Tr. Therefore, the Doppler frequency f that does not cause aliasing derived according to the sampling theorem is dThe range is -1 / (2Tr)≦fd<1 / (2Tr). Even if the Doppler frequency exceeds this range, the range of the observed Doppler frequency fd is -1 / (2Tr)≦fd<1 / (2Tr).

[0191] For example, when the Doppler frequency shift unit 104 assigns the Doppler frequency shift amount within the range of -1 / (2Tr)≦fd<1 / (2Tr), the maximum Doppler frequency shift interval for Nt transmission antennas (=Doppler multiplexing number) is Δfdmax=1 / (TrNt)=1 / (TrNt) DM ). For example, the Doppler frequency shift unit 104 may set the Doppler frequency shift interval to an interval smaller than Δfdmax. The phase rotation amount given to such a Doppler frequency shift is For example, in is set within the range of

[0192] In the following description of the operation of the Doppler frequency shift unit 104, when a frequency exceeding Phase rotation of the range When , a phase rotation with the same phase in the range of -π to π can be given Here, α satisfies The integer value of .

[0193] In addition, for example, the Doppler multiplexing interval assigned to the Doppler multiplexing signal by the Doppler frequency shift unit 104 may be set in units of 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, the effect of simplifying the processing in the CFAR unit 210 described later can be obtained. In addition, the following shows a case where δ is a positive integer, but it is not limited to this, and a positive real number may also be used.

[0194] [Formula 3]

[0195] Δfd = 1 / (Tr × (N DM + δ)) (3)

[0196] In addition, when δ is set to a positive integer of δ>1 in equation (3), there are a plurality of Doppler frequency shift amounts to which the Doppler multiplexed signal is not allocated (for example, in the following setting example of the Doppler frequency shift amount, the Doppler frequency shift amount indicated by the "×" mark in the figure used). In this case, for example, by allocating the Doppler multiplexed signal in such a manner that these Doppler frequency shift amounts are not equally spaced, the Doppler frequency range fd detectable by the radar device 10 can be set within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0197] Next, an example of setting the Doppler shift amount in the Doppler shift unit 104 will be described.

[0198] <Doppler shift amount setting example 1>

[0199] Fig. 9 Indicates the number of transmitting antennas Nt = 3, N PL1 =2, N PL2 =1 is an example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency. Fig. 9 In the figure, Tx#1 and Tx#2 are PL1 polarized transmitting antennas, and Tx#3 is PL2 polarized transmitting antenna.

[0200] In addition, in the setting example 1 of the Doppler frequency shift amount, if Fig. 9 As shown in FIG. 1 , the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (4Tr), δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0201] exist Fig. 9 In the example shown, the first to third Doppler shift units 104 (or Doppler shift units 104 - 1 , 104 - 2 , and 104 - 3 ) can perform the following operations.

[0202] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = 2πDOP1×Tr = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0203] For example, in order to provide the second transmission antenna Tx#2 with the Doppler shift amount DOP2=-1 / (4Tr), the second Doppler shift unit 104 provides a phase rotation of Φ2(m)=2πDOP2×Tr=-π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0204] For example, in order to give the Doppler shift amount DOP3=0 to the third transmission antenna Tx#3, the third Doppler shift unit 104 gives a phase rotation of Φ3(m)=2πDOP3×Tr=0 according to the transmission period Tr of the chirp signal and outputs it.

[0205] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0206] exist Fig. 9 In the example, the interval (Doppler multiplexing interval) of the Doppler frequency shift amount given to each transmitting antenna Tx#1, Tx#2, and Tx#3 is Δfd (1，2) =Δfd,Δfd(2，3) =Δfd,Δfd (3，1) =2Δfd. Therefore, Fig. 9 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=3 are not all the same, but include unequal intervals (for example, Δfd (1，2) =Δfd (2，3) ≠Δfd (3，1) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0207] In addition, Fig. 9 In the transmission antenna, the Doppler frequency shift interval between the transmitting antennas Tx#1 and Tx#2 with PL1 polarization is Δfd (1，2) =Δfd,Δfd (2，1) =3Δfd. Therefore, the number of PL1 polarized antennas is N PL1 = 2, the intervals of the Doppler frequency shift amounts given by the PL1 polarized antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，1) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL1 polarized antenna.

[0208] In addition, Fig. 9 The number of transmitting antennas Tx#3 with PL2 polarization in the transmitting antenna is N PL2 =1, so the SIMO radar structure based on the PL2 polarized antenna will not constitute a relationship of Doppler multiplexing transmission, so it does not need to be considered.

[0209] therefore, Fig. 9 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1.

[0210] In addition, Fig. 9 In, N PL1 (=2)≠N PL2 (=1). For example, Fig. 9 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0211] therefore, Fig. 9 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2 (2).

[0212] For example, Fig.10 Indicates the use of Fig. 9The setting of the Doppler frequency shift amount shown is an example of a received signal in the output of the Doppler analysis unit 209 when the transmitting antenna unit 105 sets the PL1 polarization to left-hand circular polarization (LC) and the PL2 polarization to right-hand circular polarization (RC), and the LC polarization (PL1 polarization) antenna is used in the receiving antenna unit 202.

[0213] Fig.10 The output of the Doppler analysis unit 209 represents the target object reflected wave of a certain distance index. For example, the target object reflected wave includes fd target This Doppler frequency. Fig.10 As shown, the radar device 10 receives Fig. 9 The amount of Doppler shift shown occurs based on fd target The amount of Doppler shift in the signal.

[0214] Here, when the reflected wave of the radar transmission wave after being reflected by the target object is a reflected wave having multiple reflection times or including multiple scattered waves, the reflected wave may include multiple polarizations. Therefore, the difference in the reception level of the received signal in the radar device 10 is not easy to become large between the received signals corresponding to different polarization transmission antennas (for example, PL1 polarization transmission antenna and PL2 polarization transmission antenna). Therefore, the radar device 10 receives the received signal corresponding to the RC polarization (PL2 polarization) transmission antenna and the received signal corresponding to the LC polarization (PL1 polarization) transmission antenna at substantially the same reception level.

[0215] For example, in Fig. 9 When the Doppler shift amount is set as shown, when the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)) is not included, the following is obtained: Fig.10 The received signal is as shown in (a). Fig.10 As shown in (a), the reception levels of the reception signals corresponding to the transmission antennas Tx#1 (PL1 polarization), Tx#2 (PL1 polarization) and Tx#3 (PL2 polarization) are substantially the same.

[0216] In addition, for example, when the radar device 10 receives a reflected wave (for example, a first regular reflection) of a radar transmission wave reflected normally at a target object (for example, a mirror reflection on a surface with few unevenness), the reception level may be different between polarized transmission antennas. For example, the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna becomes a signal of the same polarization as the LC polarization (PL1 polarization) reception antenna. On the other hand, for example, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna becomes a signal of cross-polarization with the LC polarization (PL1 polarization) reception antenna. Therefore, compared with the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna, the reception level of the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna may be smaller (depending on the cross-polarization discrimination of the antenna, for example, a reception level that is smaller by more than 10 dB). For example, depending on the reception SNR, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna may be below the noise level, so that the peak detection of the Doppler frequency becomes difficult in the radar device 10.

[0217] For example, in Fig. 9 In the case of the Doppler shift amount setting shown in the figure, in the case of a target reflected wave including RC polarization (PL2 polarization) cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)), it is obtained Fig.10 The received signal is as shown in (b). Fig.10 As shown in (b), the reception level of the reception signal corresponding to the transmission antenna Tx#3 (PL2 polarization) is smaller than the reception level of the reception signal corresponding to the transmission antennas Tx#1 and Tx#2 (PL1 polarization).

[0218] In addition, for example, when the radar device 10 receives a reflected wave of the radar transmission wave reflected normally at the target object and further reflected normally on the road surface or the like (for example, 2 regular reflections), the reception level may be different between polarized transmission antennas. For example, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna becomes a signal of the same polarization as the LC polarization (PL1 polarization) reception antenna. On the other hand, for example, the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna becomes a signal of cross-polarization with the LC polarization (PL1 polarization) reception antenna. Therefore, compared with the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna, the reception level of the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna may be smaller (depending on the cross-polarization discrimination of the antenna and, for example, a reception level that is 10 dB or more smaller). For example, depending on the reception SNR, the reception signal from the LC polarization (PL1 polarization) transmission antenna may be below the noise level, so that the peak detection of the Doppler frequency becomes difficult in the radar device 10.

[0219] For example, in Fig. 9 In the case of the Doppler shift amount setting shown in FIG. 1 , in the case of a target reflected wave including LC polarization (PL1 polarization) cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)), the following is obtained: Fig.10 The received signal is as shown in (c). Fig.10 As shown in (c), the reception level of the reception signal corresponding to the transmission antennas Tx#1 and Tx#2 (PL1 polarization) is smaller than the reception level of the reception signal corresponding to the transmission antenna Tx#3 (PL2 polarization).

[0220] For example, Fig.10 As shown in (a), when the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the RC polarization (PL2 polarization) transmission antenna (Tx#3) and the LC polarization (PL1 polarization) transmission antenna (Tx#1 and Tx#2) at approximately the same level. Fig.10 In (a), for the signals transmitted from the Nt transmission antennas Tx#1, Tx#2, and Tx#3 composed of the RC polarization (PL2 polarization) transmission antenna and the LC polarization (PL1 polarization) transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0221] In addition, if Fig.10 (b) and Fig.10 As shown in (c), when the reflected wave of the target object with cross polarization relative to the receiving antenna is included, when the reflected wave of the target object with cross polarization PL2 is included ( Fig.10 (b)) and when the reflected wave of the target containing PL1 polarization is cross-polarized ( Fig.10 (c)), the radar device 10 receives Doppler multiplexed signals that are different from each other (for example, Doppler multiplexed signals that satisfy condition 2 (2)). For example, the radar device 10 receives Doppler multiplexed signals that are different from each other (for example, Doppler multiplexed signals that satisfy condition 2 (2)). Fig.10 (b) The receiving Doppler frequency shift interval Δfd (1，2) or Δfd (2，1) The two Doppler frequency components of the signal are Fig.10 (c) A signal with a Doppler frequency component is received.

[0222] As described above, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0223] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a reduction in the reception level of the reception signal corresponding to the PL1 polarization (LC polarization) transmitting antenna has occurred, or a reduction in the reception level of the reception signal corresponding to the PL2 polarization (RC polarization) transmitting antenna has occurred, based on the peak value of the detected Doppler frequency (for example, the number of peaks).

[0224] For example, for the Doppler multiplexed signal of LC polarization (PL1 polarization), Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the LC polarization (PL1 polarization) transmitting antenna, the radar device 10 can use the existing demultiplexing operation of the Doppler multiplexed signal to demultiplex the Doppler multiplexed signal.

[0225] In addition, the RC polarization (PL2 polarization) transmitting antenna is a single antenna transmission. Therefore, for example, when the Doppler multiplexing and demultiplexing unit 211 determines that the received signal is a received signal corresponding to the RC polarization (PL2 polarization) transmitting antenna, the radar device 10 may not perform the demultiplexing process of the Doppler multiplexing signal of the RC polarization received signal.

[0226] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0227] <Doppler shift amount setting example 2>

[0228] Fig.11 Indicates the number of transmitting antennas Nt = 4, N PL1 =2, N PL2 An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =2. Fig.11 In the figure, Tx#1 and Tx#2 are PL1 polarized transmitting antennas, and Tx#3 and Tx#4 are PL2 polarized transmitting antennas.

[0229] In addition, in the setting example 2 of the Doppler frequency shift amount, if Fig.11As shown in FIG. 1 , the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (5Tr), δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0230] exist Fig.11 In the example shown, the first to fourth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 4 ) can perform the following operations.

[0231] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0232] For example, in order to provide the Doppler shift amount DOP2 = -3 / (10Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -3π(m-1) / 5 according to the transmission period Tr of the chirp signal and outputs it.

[0233] For example, in order to provide the Doppler shift amount DOP3 = -1 / (10Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 5 according to the transmission period Tr of the chirp signal and outputs it.

[0234] For example, in order to provide the Doppler shift amount DOP4=3 / (10Tr) to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 provides a phase rotation of Φ4(m)=3π(m-1) / 5 according to the transmission period Tr of the chirp signal and outputs it.

[0235] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0236] exist Fig.11 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna Tx#1 to Tx#4 is Δfd (1，2) =Δfd,Δfd (2，3) =Δfd,Δfd (3，4) =2Δfd,Δfd (4，1) =Δfd. Therefore, Fig.11 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=4 are not all the same, but include unequal intervals (for example, Δfd (1，2) =Δfd (2，3) =Δfd(4，1) ≠Δfd (3，4) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0237] In addition, Fig.11 In the example, the Doppler frequency shift interval between the transmitting antennas Tx#1 and Tx#2 with PL1 polarization is Δfd. (1，2) =Δfd,Δfd (2，1) =4Δfd. Therefore, the number of PL1 polarized transmitting antennas is N PL1 = 2, the intervals of the Doppler frequency shift amounts given by the PL1 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，1) , so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL1 polarized transmitting antenna.

[0238] In addition, Fig.11 The interval of the Doppler frequency shift between the transmitting antennas Tx#3 and Tx#4 with PL2 polarization is Δfd (3，4) =2Δfd,Δfd (4，3) =3Δfd. Therefore, the number of PL2 polarized transmitting antennas is N PL2 = 2, the intervals of the Doppler frequency shift amounts given by the PL2 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (3，4) ≠Δfd (4，3) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by PL2 polarized antenna.

[0239] therefore, Fig.11 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1.

[0240] In addition, Fig.11 In the example, the Doppler frequency shift interval between the PL1 polarized transmitting antennas Tx#1 and Tx#2 is Δfd (1，2) =Δfd,Δfd (2，1) =4Δfd, the interval of Doppler frequency shift between PL2 polarized transmitting antennas Tx#3 and Tx#4 is Δfd (3，4) =2Δfd,Δfd (4，3) =3Δfd Therefore, the Doppler shift amount between the PL1 polarized transmission antennas Tx#1 and Tx#2 and the Doppler shift amount between the PL2 polarized transmission antennas Tx#3 and Tx#4 include different Doppler shift intervals.

[0241] For example, the maximum DDM interval of the Doppler frequency shift between the PL1 polarized transmitting antennas Tx#1 and Tx#2 is Δfd (2，1) =4Δfd, the maximum DDM interval of the Doppler frequency shift between the PL2 polarized transmitting antennas Tx#3 and Tx#4 is Δfd (4，3) =3Δfd, the two are different.

[0242] Similarly, for example, the minimum DDM interval of the Doppler frequency shift between the PL1 polarized transmitting antennas Tx#1 and Tx#2 is Δfd (1，2) =Δfd, the minimum DDM interval of the Doppler frequency shift between PL2 polarized transmitting antennas Tx#3 and Tx#4 is Δfd (3，4) =2Δfd, the two are different.

[0243] As mentioned above, in Fig.11 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0244] therefore, Fig.11 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2 (1).

[0245] For example, Fig.12 Indicates the use of Fig.11 The setting of the Doppler frequency shift amount shown is an example of a received signal in the output of the Doppler analysis unit 209 when the transmitting antenna unit 105 sets the PL1 polarization to left-hand circular polarization (LC) and the PL2 polarization to right-hand circular polarization (RC), and the LC polarization (PL1 polarization) antenna is used in the receiving antenna unit 202.

[0246] Fig.12 The output of the Doppler analysis unit 209 represents the target object reflected wave of a certain distance index. For example, the target object reflected wave includes fd target This Doppler frequency. Fig.12 As shown, the radar device 10 receives Fig.11 The amount of Doppler shift shown occurs based on fd target The amount of Doppler shift in the signal.

[0247] Here, when the reflected wave of the radar transmission wave after being reflected by the target is a reflected wave having multiple reflection times or including multiple scattered waves, the reflected wave may include multiple polarizations. Therefore, the difference in the reception level of the received signal in the radar device 10 is not easy to become large between the received signals corresponding to different polarization transmission antennas (for example, PL1 polarization transmission antenna and PL2 polarization transmission antenna). Therefore, the radar device 10 receives the received signal corresponding to the RC polarization (PL2 polarization) transmission antenna and the received signal corresponding to the LC polarization (PL1 polarization) transmission antenna at approximately the same reception level.

[0248] For example, in Fig.11 When the Doppler shift amount is set as shown, when the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)) is not included, the following is obtained: Fig.12 The received signal is as shown in (a). Fig.12 As shown in (a), the reception levels of the reception signals corresponding to the transmitting antennas Tx#1, Tx#2 (PL1 polarization), Tx#3, and Tx#4 (PL2 polarization) are substantially the same.

[0249] In addition, for example, when the radar device 10 receives a reflected wave (for example, a first regular reflection) of a radar transmission wave reflected normally at a target object (for example, a mirror reflection on a surface with few bumps and depressions), the reception level may be different between polarized transmission antennas. For example, the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna becomes a signal of the same polarization as the receiving antenna. On the other hand, for example, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna becomes a signal of cross-polarization with the LC polarization (PL1 polarization) receiving antenna. Therefore, compared with the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna, the reception level of the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna may be smaller (depending on the cross-polarization discrimination of the antenna and, for example, a reception level that is 10 dB or more smaller). For example, depending on the reception SNR, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna may be below the noise level, so that the peak detection of the Doppler frequency becomes difficult in the radar device 10.

[0250] For example, in Fig.11 In the case of the Doppler shift amount setting shown in the figure, in the case of a target reflected wave including RC polarization (PL2 polarization) cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)), it is obtained Fig.12 The received signal is as shown in (b). Fig.12As shown in (b), the reception level of the reception signal corresponding to the transmission antennas Tx#3 and Tx#4 (PL2 polarization) is smaller than the reception level of the reception signal corresponding to the transmission antennas Tx#1 and Tx#2 (PL1 polarization).

[0251] In addition, for example, when the radar device 10 receives a reflected wave of the radar transmission wave reflected normally at the target object and further reflected normally on the road surface or the like (for example, 2 regular reflections), the reception level may be different between polarized transmission antennas. For example, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna becomes a signal of the same polarization as the LC polarization (PL1 polarization) reception antenna. On the other hand, for example, the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna becomes a signal of cross-polarization with the LC polarization (PL1 polarization) reception antenna. Therefore, compared with the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna, the reception level of the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna may be smaller (depending on the cross-polarization discrimination of the antenna and, for example, a reception level that is 10 dB or more smaller). For example, depending on the reception SNR, the reception signal from the LC polarization (PL1 polarization) transmission antenna may be below the noise level, so that the peak detection of the Doppler frequency becomes difficult in the radar device 10.

[0252] For example, in Fig.11 In the case of the Doppler shift amount setting shown in FIG. 1 , in the case of a target reflected wave including LC polarization (PL1 polarization) cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)), the following is obtained: Fig.12 The received signal is as shown in (c). Fig.12 As shown in (c), the reception level of the reception signal corresponding to the transmission antennas Tx#1 and Tx#2 (PL1 polarization) is smaller than the reception level of the reception signal corresponding to the transmission antennas Tx#3 and Tx#4 (PL2 polarization).

[0253] For example, Fig.12 As shown in (a), in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the RC polarization (PL2 polarization) transmission antennas (Tx#3 and Tx#4) and the LC polarization (PL1 polarization) transmission antennas (Tx#1 and Tx#2) at approximately the same level. Fig.12In (a), for the signals transmitted from the Nt transmission antennas Tx#1, Tx#2, Tx#3, and Tx#4 composed of the RC polarization (PL2 polarization) transmission antenna and the LC polarization (PL1 polarization) transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0254] In addition, if Fig.12 (b) and Fig.12 As shown in (c), when the reflected wave of the target object with cross polarization relative to the receiving antenna is included, when the reflected wave of the target object with cross polarization PL2 is included ( Fig.12 (b)) and when the reflected wave of the target containing PL1 polarization is cross-polarized ( Fig.12 (c)), the radar device 10 receives Doppler multiplexed signals that are different from each other (for example, Doppler multiplexed signals that satisfy condition 2 (1)). For example, the radar device 10 receives Doppler multiplexed signals that are different from each other (for example, Doppler multiplexed signals that satisfy condition 2 (1)). Fig.12 The receiving Doppler frequency shift interval Δfd in (b) (1，2) or Δfd (2，1) The two Doppler frequency components of the signal are Fig.12 In (c), the receiving Doppler frequency shift interval Δfd (3，4) or Δfd (4，3) The signal of the two Doppler frequency components.

[0255] As described above, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0256] As a result, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a reduction in the reception level of the reception signal corresponding to the PL1 polarization (LC polarization) transmitting antenna has occurred, or a reduction in the reception level of the reception signal corresponding to the PL2 polarization (RC polarization) transmitting antenna has occurred, based on the peak value of the detected Doppler frequency (for example, the interval between the peaks).

[0257] For example, for the Doppler multiplexed signal of LC polarization (PL1 polarization), Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the result of the determination by the Doppler multiplexing demultiplexing unit 211 is that the received signal is a received signal corresponding to the transmission signal transmitted by the LC polarization (PL1 polarization) transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0258] Similarly, for example, for the Doppler multiplexed signal of RC polarization (PL2 polarization), Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the RC polarization (PL2 polarization) transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0259] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0260] In the above, setting examples 1 and 2 of the Doppler frequency shift amount are described. In the following, different Doppler setting examples are described. In addition, in setting examples 1 and 2, the PL1 polarization is set to LC polarization and the PL2 polarization is set to RC polarization for description, but it is not limited to this. For example, when polarizations having an orthogonal relationship with each other are used as PL1 polarization and PL2 polarization, a phenomenon including the following target reflection wave will occur, in which the transmission signal from the transmitting polarization antenna of one side is cross-polarized relative to the polarization of the receiving antenna. In the following setting examples, PL1 polarization and PL2 polarization are used for description.

[0261] <Doppler shift amount setting example 3>

[0262] Fig.13 Indicates the number of transmitting antennas Nt = 6, N PL1 =3, N PL2 An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =3. Fig.13 Among them, Tx#1, Tx#2 and Tx#4 are PL1 polarized transmitting antennas, and Tx#3, Tx#5 and Tx#6 are PL2 polarized transmitting antennas.

[0263] In addition, in the setting example 3 of the Doppler frequency shift amount, Fig.13As shown in FIG. 1 , the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (7Tr), δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0264] exist Fig.13 In the example shown, the first to sixth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 6 ) can perform the following operations.

[0265] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0266] For example, in order to provide the Doppler shift amount DOP2 = -5 / (14Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -5π(m-1) / 7 according to the transmission period Tr of the chirp signal and outputs it.

[0267] For example, in order to provide the Doppler shift amount DOP3 = -3 / (14Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -3π(m-1) / 7 according to the transmission period Tr of the chirp signal and outputs it.

[0268] For example, in order to provide the Doppler shift amount DOP4 = -1 / (14Tr) to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 provides a phase rotation of Φ4(m) = -π(m-1) / 7 according to the transmission period Tr of the chirp signal and outputs it.

[0269] For example, in order to provide the Doppler shift amount DOP5=3 / (14Tr) to the fifth transmission antenna Tx#5, the fifth Doppler shift unit 104 provides a phase rotation of Φ5(m)=3π(m-1) / 7 according to the transmission period Tr of the chirp signal and outputs it.

[0270] For example, in order to provide the Doppler shift amount DOP6=5 / (14Tr) to the sixth transmission antenna Tx#6, the sixth Doppler shift unit 104 provides a phase rotation of Φ6(m)=5π(m-1) / 7 according to the transmission period Tr of the chirp signal and outputs it.

[0271] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0272] exist Fig.13In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna 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) =2Δfd. Therefore, Fig.13 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas of the number of transmitting antennas Nt=6 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) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0273] In addition, Fig.13 In the example, the interval between the Doppler frequency shifts of the transmitting antennas Tx#1, Tx#2, and Tx#4 with PL1 polarization is Δfd. (1，2) =Δfd,Δfd (2，4) =2Δfd,Δfd (4，1) =4Δfd. Therefore, the number of PL1 polarized transmitting antennas is N PL1 =3, the intervals of the Doppler frequency shift amounts given by the PL1 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，4) ≠Δfd (4，1) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL1 polarized transmitting antenna.

[0274] In addition, Fig.13 The interval of the Doppler frequency shift between the transmitting antennas Tx#3, Tx#5, and Tx#6 of PL2 polarization is Δfd (3，5) =3Δfd,Δfd (5，6) =Δfd,Δfd (6，3) =3Δfd. Therefore, the number of PL2 polarized transmitting antennas is N PL2 =3, the intervals of the Doppler frequency shift amounts given by the PL2 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (3，5) =Δfd (6，3) ≠Δfd (5，6) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by PL2 polarized antenna.

[0275] therefore, Fig.13 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1.

[0276] In addition, Fig.13 In the example, the interval of Doppler frequency shift between PL1 polarized transmitting antennas Tx#1, Tx#2, and Tx#4 is Δfd (1，2) =Δfd,Δfd (2，4) =2Δfd,Δfd (4，1) =4Δfd, the interval of Doppler frequency shift between PL2 polarized transmitting antennas Tx#3, Tx#5, and Tx#6 is Δfd (3，5) =3Δfd,Δfd (5，6) =Δfd,Δfd (6，3) =3Δfd. Therefore, the Doppler shift amounts between the PL1 polarized transmission antennas Tx#1, Tx#2, and Tx#4 and the Doppler shift amounts between the PL2 polarized transmission antennas Tx#3, Tx#5, and Tx#6 include different Doppler shift intervals.

[0277] For example, the intervals between the Doppler frequency shift amounts of the PL1 polarized transmitting antennas Tx#1, Tx#2, and Tx#4 include 2Δfd and 4Δfd, but the intervals between the Doppler frequency shift amounts of the PL2 polarized transmitting antennas Tx#3, Tx#5, and Tx#6 do not include 2Δfd and 4Δfd.

[0278] For example, the maximum DDM interval of the Doppler shift amount between PL2 polarized transmission antennas Tx#3, Tx#5, and Tx#6 is 3Δfd, but the interval of the Doppler shift amount between PL1 polarized transmission antennas Tx#1, Tx#2, and Tx#4 does not include 3Δfd.

[0279] As mentioned above, in Fig.13 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0280] therefore, Fig.13 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2 (1).

[0281] For example, in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the PL1 polarization transmission antenna (Tx#1, Tx#2 and Tx#4) and the PL2 polarization transmission antenna (Tx#3, Tx#5 and Tx#6) at approximately the same level. Here, for the signals transmitted from the Nt transmission antennas Tx#1 to Tx#6 composed of the PL1 polarization transmission antenna and the PL2 polarization transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0282] In addition, in the case of a target object reflection wave whose polarization relative to the receiving antenna is cross-polarized, in the case of a target object reflection wave whose PL1 polarization is cross-polarized and in the case of a target object reflection wave whose PL2 polarization is cross-polarized, the radar device 10 receives different Doppler multiplexed signals (for example, a Doppler multiplexed signal that satisfies condition 2 (1)).

[0283] For example, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0284] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a reduction in the reception level of the reception signal corresponding to the PL1 polarized transmitting antenna or a reduction in the reception level of the reception signal corresponding to the PL2 polarized transmitting antenna occurs based on the peak value of the detected Doppler frequency (for example, the interval between the peaks).

[0285] For example, for the Doppler multiplexed signal of PL1 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL1 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0286] Similarly, for example, for the Doppler multiplexed signal of PL2 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL2 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0287] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0288] <Doppler shift amount setting example 4>

[0289] Fig.14 Indicates the number of transmitting antennas Nt = 6, N PL1 =3, N PL2 An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =3. Fig.14 Among them, Tx#1, Tx#4 and Tx#6 are PL1 polarized transmitting antennas, and Tx#2, Tx#3 and Tx#5 are PL2 polarized transmitting antennas.

[0290] In addition, in the setting example 4 of the Doppler frequency shift amount, Fig.14 As shown in FIG. 1 , the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (8Tr), δ=2, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0291] exist Fig.14 In the example shown, the first to sixth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 6 ) can perform the following operations.

[0292] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0293] For example, in order to provide the Doppler shift amount DOP2 = -1 / (4Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0294] For example, in order to provide the Doppler shift amount DOP3 = -1 / (8Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0295] For example, in order to give the Doppler shift amount DOP4=0 to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 gives a phase rotation of Φ4(m)=0 according to the transmission period Tr of the chirp signal and outputs it.

[0296] For example, in order to provide the Doppler shift amount DOP5=1 / (8Tr) to the fifth transmission antenna Tx#5, the fifth Doppler shift unit 104 provides a phase rotation of Φ5(m)=π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0297] For example, in order to provide the Doppler shift amount DOP6=1 / (4Tr) to the sixth transmission antenna Tx#6, the sixth Doppler shift unit 104 provides a phase rotation of Φ6(m)=π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0298] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0299] exist Fig.14 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna 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) =2Δfd. Therefore, Fig.14 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas of the number of transmitting antennas Nt=6 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) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0300] In addition, Fig.14 The interval of Doppler frequency shift between the transmitting antennas Tx#1, Tx#4, and Tx#6 with PL1 polarization is Δfd (1，4) =4Δfd,Δfd(4，6) =2Δfd,Δfd (6，1) =2Δfd. Therefore, the number of PL1 polarized transmitting antennas is N PL1 =3, the intervals of the Doppler frequency shift amounts given by the PL1 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (1，4) ≠Δfd (4，6) =Δfd (6，1) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL1 polarized transmitting antenna.

[0301] In addition, Fig.14 In the example, the interval between the Doppler frequency shifts of the transmitting antennas Tx#2, Tx#3, and Tx#5 with PL2 polarization is Δfd. (2，3) =Δfd,Δfd (3，5) =2Δfd,Δfd (5，2) =5Δfd. Therefore, the number of PL2 polarized transmitting antennas is N PL2 =3, the intervals of the Doppler frequency shift amounts given by the PL2 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (2，3) ≠Δfd (3，5) ≠Δfd (5，2) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by PL2 polarized antenna.

[0302] therefore, Fig.14 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1.

[0303] In addition, Fig.14 In the example, the interval of Doppler frequency shift between PL1 polarized transmitting antennas Tx#1, Tx#4, and Tx#6 is Δfd (1，4) =4Δfd,Δfd (4，6) =2Δfd,Δfd (6，1) =2Δfd, the interval of Doppler frequency shift between PL2 polarized transmitting antennas Tx#2, Tx#3, and Tx#5 is Δfd (2，3) =Δfd,Δfd (3，5) =2Δfd,Δfd (5，2) =5Δfd. Therefore, the Doppler shift amounts between the PL1 polarized transmission antennas Tx#1, Tx#4, and Tx#6 and the Doppler shift amounts between the PL2 polarized transmission antennas Tx#2, Tx#3, and Tx#5 include different Doppler shift intervals.

[0304] For example, the interval between the Doppler shift amounts of PL1 polarized transmission antennas Tx#1, Tx#4, and Tx#6 includes 4Δfd, but the interval between the Doppler shift amounts of PL2 polarized transmission antennas Tx#2, Tx#3, and Tx#5 does not include 4Δfd.

[0305] In addition, for example, the maximum DDM interval of the Doppler frequency shift amount between PL2 polarized transmission antennas Tx#2, Tx#3 and Tx#5 includes Δfd and 5Δfd, but the Doppler frequency shift amount between PL1 polarized transmission antennas Tx#1, Tx#4 and Tx#6 does not include Δfd and 5Δfd.

[0306] As mentioned above, in Fig.14 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0307] therefore, Fig.14 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2 (1).

[0308] For example, in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the PL1 polarization transmission antenna (Tx#1, Tx#4 and Tx#6) and the PL2 polarization transmission antenna (Tx#2, Tx#3 and Tx#5) at approximately the same level. Here, for the signals transmitted from the Nt transmission antennas Tx#1 to Tx#6 composed of the PL1 polarization transmission antenna and the PL2 polarization transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0309] In addition, in the case of a target object reflection wave whose polarization relative to the receiving antenna is cross-polarized, in the case of a target object reflection wave whose PL1 polarization is cross-polarized and in the case of a target object reflection wave whose PL2 polarization is cross-polarized, the radar device 10 receives different Doppler multiplexed signals (for example, a Doppler multiplexed signal that satisfies condition 2 (1)).

[0310] For example, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0311] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a reduction in the reception level of the reception signal corresponding to the PL1 polarized transmitting antenna or a reduction in the reception level of the reception signal corresponding to the PL2 polarized transmitting antenna occurs based on the peak value of the detected Doppler frequency (for example, the interval between the peaks).

[0312] For example, for the Doppler multiplexed signal of PL1 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL1 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0313] Similarly, for example, for the Doppler multiplexed signal of PL2 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL2 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0314] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0315] <Doppler shift amount setting example 5>

[0316] Fig.15 Indicates the number of transmitting antennas Nt = 6, N PL1 =3, N PL2 An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =3. Fig.15 Among them, Tx#1, Tx#2 and Tx#4 are PL1 polarized transmitting antennas, and Tx#3, Tx#5 and Tx#6 are PL2 polarized transmitting antennas.

[0317] In addition, in the setting example 5 of the Doppler frequency shift amount, Fig.15 As shown in FIG. 1 , the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (8Tr), δ=2, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0318] exist Fig.15 In the example shown, the first to sixth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 6 ) can perform the following operations.

[0319] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0320] For example, in order to provide the Doppler shift amount DOP2 = -3(8Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -3π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0321] For example, in order to provide the Doppler shift amount DOP3 = -1 / (4Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0322] For example, in order to provide the Doppler shift amount DOP4 = -1 / (8Tr) to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 provides a phase rotation of Φ4(m) = -π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0323] For example, in order to give the Doppler shift amount DOP5 = 0 to the fifth transmission antenna Tx# 5 , the fifth Doppler shift unit 104 gives a phase rotation Φ5(m) = 0 according to the transmission period Tr of the chirp signal and outputs it.

[0324] For example, in order to provide the Doppler shift amount DOP6=1 / (8Tr) to the sixth transmission antenna Tx#6, the sixth Doppler shift unit 104 provides a phase rotation of Φ6(m)=π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0325] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0326] exist Fig.15 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna 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) =3Δfd. Therefore, Fig.15 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas of the number of transmitting antennas Nt=6 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) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0327] In addition, Fig.15 In the example, the interval between the Doppler frequency shifts of the transmitting antennas Tx#1, Tx#2, and Tx#4 with PL1 polarization is Δfd. (1，2) =Δfd,Δfd (2，4) =2Δfd,Δfd (4，1) =5Δfd. Therefore, the number of PL1 polarized transmitting antennas is N PL1 =3, the intervals of the Doppler frequency shift amounts given by the PL1 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，4) =Δfd (4，1) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL1 polarized transmitting antenna.

[0328] In addition, Fig.15 The interval of the Doppler frequency shift between the transmitting antennas Tx#3, Tx#5, and Tx#6 of PL2 polarization is Δfd (3，5) =2Δfd,Δfd (5，6) =Δfd,Δfd (6，3) =5Δfd. Therefore, the number of PL2 polarized transmitting antennas is N PL2 =3, the intervals of the Doppler frequency shift amounts given by the PL2 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (3，5) ≠Δfd (5，6) ≠Δfd (6，3) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by PL2 polarized antenna.

[0329] therefore, Fig.15 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1.

[0330] In addition, Fig.15 In the example, the Doppler frequency shift between the PL1 polarized transmitting antennas Tx#1, Tx#2, and Tx#4 is Δfd (1，2) =Δfd,Δfd(2，4) =2Δfd,Δfd (4，1) =5Δfd, the Doppler frequency shift between PL2 polarized transmitting antennas Tx#3, Tx#5, and Tx#6 is Δfd (3，5) =2Δfd,Δfd (5，6) =Δfd,Δfd (6，3) =5Δfd. Thus, the Doppler frequency shift amounts between the PL1 polarized transmitting antennas Tx#1, Tx#2, and Tx#4 and the Doppler frequency shift amounts between the PL2 polarized transmitting antennas Tx#3, Tx#5, and Tx#6 include the same combination of Doppler frequency shift intervals, but the order of the Doppler frequency shift intervals between the PL1 polarization and the PL2 polarization in the Doppler frequency domain is different.

[0331] For example, in Fig.15 In the order of the intervals of the Doppler frequency shift amounts respectively allocated to the PL1 polarized transmitting antennas Tx#1, Tx#2, and Tx#4, the order is Δfd, 2Δfd, and 5Δfd. Fig.15 In the example, the order of the intervals of the Doppler frequency shift amounts assigned to the PL2 polarized transmitting antennas Tx#3, Tx#5, and Tx#6 is 2Δfd, Δfd, and 5Δfd. Fig.15 In , for the PL1 polarized transmit antenna and the PL2 polarized transmit antenna, although the same combination of Doppler frequency shift intervals (for example, Δfd, 2Δfd, 5Δfd) is included, the order of these intervals is different between different polarizations. Fig.15 For example, even if the Doppler shift interval between PL1 polarization transmission antennas and the Doppler shift interval between PL2 polarization transmission antennas are cyclically shifted in the Doppler frequency domain, the Doppler shift amounts will not be consistent between different polarizations.

[0332] As mentioned above, in Fig.15 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0333] therefore, Fig.15 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2 (3).

[0334] For example, in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the PL1 polarization transmission antenna (Tx#1, Tx#2 and Tx#4) and the PL2 polarization transmission antenna (Tx#3, Tx#5 and Tx#6) at approximately the same level. Here, for the signals transmitted from the Nt transmission antennas Tx#1 to Tx#6 composed of the PL1 polarization transmission antenna and the PL2 polarization transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0335] In addition, in the case of a target object reflection wave whose polarization relative to the receiving antenna is cross-polarized, in the case of a target object reflection wave whose PL1 polarization is cross-polarized, and in the case of a target object reflection wave whose PL2 polarization is cross-polarized, the radar device 10 receives different Doppler multiplexed signals (for example, a Doppler multiplexed signal that satisfies condition 2 (3)).

[0336] For example, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0337] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a reduction in the reception level of the reception signal corresponding to the PL1 polarized transmitting antenna or a reduction in the reception level of the reception signal corresponding to the PL2 polarized transmitting antenna occurs based on the detected Doppler frequency peak value (for example, the order of the Doppler frequency shift interval).

[0338] For example, for the Doppler multiplexed signal of PL1 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL1 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0339] Similarly, for example, for the Doppler multiplexed signal of PL2 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL2 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0340] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0341] <Doppler shift amount setting example 6>

[0342] Fig.16 Indicates the number of transmitting antennas Nt = 5, N PL1 =3, N PL2 An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =2. Fig.16 Among them, Tx#3, Tx#4 and Tx#5 are PL1 polarized transmitting antennas, and Tx#1 and Tx#2 are PL2 polarized transmitting antennas.

[0343] In addition, in the setting example 6 of the Doppler frequency shift amount, Fig.16 As shown in FIG. 1 , the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (6Tr), δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0344] exist Fig.16 In the example shown, the first to fifth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 5 ) can perform the following operations.

[0345] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0346] For example, in order to provide the Doppler shift amount DOP2 = -1 / (3Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -2π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0347] For example, in order to provide the Doppler shift amount DOP3 = -1 / (6Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0348] For example, in order to give the Doppler shift amount DOP4=0 to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 gives a phase rotation of Φ4(m)=0 according to the transmission period Tr of the chirp signal and outputs it.

[0349] For example, in order to provide the Doppler shift amount DOP5 = 1 / (6Tr) to the fifth transmission antenna Tx#5, the fifth Doppler shift unit 104 provides a phase rotation of Φ5(m) = π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0350] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0351] exist Fig.16 In the example, the interval between the Doppler frequency shift amounts given to the transmission antennas Tx#1 to Tx#5 (Doppler frequency shift interval) is Δfd (1，2) =Δfd (2，3) =Δfd (3，4) =Δfd (4，5) =Δfd,Δfd (5，1) =2Δfd. Therefore, Fig.16 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=5 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) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0352] In addition, Fig.16 The interval of Doppler frequency shift between the transmitting antennas Tx#3, Tx#4, and Tx#5 with PL1 polarization is Δfd (3，4) =Δfd,Δfd (4，5) =Δfd,Δfd (5，3) =4Δfd. Therefore, the number of PL1 polarized transmitting antennas is N PL1 =3, the intervals of the Doppler frequency shift amounts given by the PL1 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (3，4) =Δfd (4，5) ≠Δfd(5，3) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL1 polarized transmitting antenna.

[0353] In addition, Fig.16 In the transmission antenna, the interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#2 with PL2 polarization is Δfd (1，2) =Δfd,Δfd (2，1) =5Δfd. Therefore, the number of PL2 polarized transmitting antennas is N PL2 = 2, the intervals of the Doppler frequency shift amounts given by the PL2 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (1，2) ≠Δfd (2，1) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by PL2 polarized antenna.

[0354] therefore, Fig.16 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 1.

[0355] In addition, Fig.16 In the example, the interval of Doppler frequency shift between PL1 polarized transmitting antennas Tx#3, Tx#4, and Tx#5 is Δfd (3，4) =Δfd,Δfd (4，5) =Δfd,Δfd (5，3) =4Δfd, the interval of Doppler frequency shift between PL2 polarized transmitting antennas Tx#1 and Tx#2 is Δfd (1，2) =Δfd,Δfd (2，1) =5Δfd. Therefore, the Doppler shift amount between the PL1 polarized transmission antennas Tx#3, Tx#4, and Tx#5 and the Doppler shift amount between the PL2 polarized transmission antennas Tx#1 and Tx#2 include different Doppler shift intervals.

[0356] For example, the interval between the Doppler frequency shift amounts of PL1 polarized transmission antennas Tx#3, Tx#4, and Tx#5 includes 4Δfd, but the interval between the Doppler frequency shift amounts of PL2 polarized transmission antennas Tx#1 and Tx#2 does not include 4Δfd.

[0357] For example, the interval between the Doppler shift amounts of the PL2 polarized transmission antennas Tx#1 and Tx#2 includes 5Δfd, but the interval between the Doppler shift amounts of the PL1 polarized transmission antennas Tx#3, Tx#4, and Tx#5 does not include 5Δfd.

[0358] In addition, Fig.16 In the example, the Doppler multiplexing number (or the number of transmitting antennas) of PL1 polarization and PL2 polarization is different (NPL1 ≠N PL2 ).

[0359] As mentioned above, in Fig.16 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0360] therefore, Fig.16 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies (1) and (2) of Condition 2.

[0361] For example, in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the PL1 polarization transmission antenna (Tx#3, Tx#4 and Tx#5) and the PL2 polarization transmission antenna (Tx#1 and Tx#2) at approximately the same level. Here, for the signals transmitted from the Nt transmission antennas Tx#1 to Tx#5 composed of the PL1 polarization transmission antenna and the PL2 polarization transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0362] In addition, in the case of a target object reflection wave whose polarization relative to the receiving antenna is cross-polarized, in the case of a target object reflection wave whose PL1 polarization is cross-polarized, and in the case of a target object reflection wave whose PL2 polarization is cross-polarized, the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals (1) and (2) that satisfy condition 2).

[0363] For example, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0364] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 described later whether a reduction in the reception level of the reception signal corresponding to the PL1 polarized transmitting antenna or a reduction in the reception level of the reception signal corresponding to the PL2 polarized transmitting antenna has occurred based on the detected Doppler frequency peak (for example, the Doppler frequency shift interval or the number of peaks).

[0365] For example, for the Doppler multiplexed signal of PL1 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL1 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0366] Similarly, for example, for the Doppler multiplexed signal of PL2 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL2 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0367] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0368] In the above, an example of setting the Doppler shift amount has been described.

[0369] The setting of the Doppler frequency shift amount is not limited to the above-mentioned setting examples 1 to 6. For example, the number of transmission antennas Nt (or the number of Doppler multiplexing), the number of PL1 polarization transmission antennas Nt, and the number of PL1 polarization transmission antennas Nt may be used. PL1 , PL2 polarization transmitting antenna number N PL2 At least one of and the Doppler shift interval is other value.

[0370] In addition, the Doppler frequency shift unit 104 gives the Doppler frequency shift amount DOP to the radar transmission signal transmitted from the Nt transmission antennas. n The phase rotation Φ n (m) can be expressed as shown in the following formula (4).

[0371] [Formula 4]

[0372] φ n (m)=(2πT r ×DOP n +Δφ0)×(m-1)+φ0 (4)

[0373] Here, Φ0 is the initial phase and ΔΦ0 is the reference Doppler shift phase.

[0374] For example, when Doppler multiplexing transmission is performed using the number of transmission antennas Nt=3, the first Doppler frequency shift unit 104 applies a phase rotation Φ1(m) to the radar transmission signal (e.g., chirp signal) input from the radar transmission signal generation unit 101 according to the transmission period Tr as shown in the following equation (5). The output of the first Doppler frequency shift unit 104 is output from the first transmission antenna (Tx#1), ​​for example. Here, cp(t) represents the chirp signal of each transmission period.

[0375] [Formula 5]

[0376] exp{jφ1(1)}cp(t), exp{jφ1(2)}cp(t),..., exp{jφ1(N c )}cp(t)(5)

[0377] In addition, for example, the second Doppler frequency shift unit 104 applies a phase rotation Φ2(m) to the radar transmission signal (for example, chirp signal) input from the radar transmission signal generation unit 101 according to the transmission period Tr as shown in the following equation (6). The output of the second Doppler frequency shift unit 104 is output from the second transmission antenna (Tx#2), for example.

[0378] [Formula 6]

[0379] exp{jφ2(1)}cp(t), exp{jφ2(2)}cp(t),..., exp{jφ2(N c )}cp(t)(6)

[0380] Similarly, for example, the third Doppler frequency shift unit 104 applies a phase rotation Φ3(m) to the radar transmission signal (for example, chirp signal) input from the radar transmission signal generation unit 101 according to the transmission period Tr as shown in the following equation (7). The output of the third Doppler frequency shift unit 104 is output from the third transmission antenna (Tx#3), for example.

[0381] [Formula 7]

[0382] exp{jφ3(1)}cp(t), exp{jφ3(2)}cp(t),..., exp{jφ3(N c )}cp(t)(7)

[0383] In the above, an example of setting the Doppler shift amount has been described.

[0384] Next, an operation example of the CFAR unit 210 and the Doppler multiplexing / demultiplexing unit 211 corresponding to the operation of the Doppler frequency shift unit 104 described above will be described.

[0385] [Operation Example of CFAR Unit 210]

[0386] For example, in order to receive a reflected wave signal of the radar transmission signal from the radar transmission unit 100, the CFAR unit 210 may perform the operation of Operation Example 1 or Operation Example 2 below.

[0387] In addition, in the following description, an operation example of the CFAR unit 210 in the case where the plurality of receiving antennas of the receiving antenna unit 202 include receiving antennas of the same polarization will be described. An operation example of the CFAR unit 210 in the case where the plurality of receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations will be described later.

[0388] <Operation Example 1 of CFAR Unit 210>

[0389] In Operation Example 1, an operation example of the CFAR unit 210 in the case where the value of δ shown in Equation (3) is set to a positive integer in the Doppler shift unit 104 will be described.

[0390] In this case, as the interval of the Doppler shift amount assigned to the Doppler multiplexed signal, an interval of Δfd or an interval that is an integer multiple of Δfd is used. Therefore, each signal subjected to Doppler multiplexing can be detected as being aliased at intervals of Δfd in the Doppler frequency domain output of the Doppler analysis unit 209. Utilizing such a property, for example, the operation of the CFAR unit 210 can be simplified as follows.

[0391] The CFAR unit 210, for example, uses a threshold value for the power sum value obtained by adding the reception powers of the reflected wave signals in each of the following ranges, and detects a Doppler peak. The range is a range (for example, a range of Δfd) that is a unit of each interval of the Doppler shift amount respectively assigned to the radar transmission signals in the Doppler frequency range that is the object of CFAR processing in the output of the Doppler analysis unit 209.

[0392] For example, the CFAR unit 210 calculates, for the outputs of the Doppler analysis units 209 of the first to Na signal processing units 206, as shown in Equation (8), the power sum value PowerDDM(fqFT, fqFT) obtained by adding the power values PowerqFT(fqFT, fqFT) shown in Equation (9) at intervals of Δfd (for example, corresponding to N Δfd ) to perform CFAR processing. b ,f s ) added together, and performs CFAR processing. b ,f sddm ) added together, and performs CFAR processing.

[0393] [Equation 8]

[0394]

[0395] [Equation 9]

[0396]

[0397] Here, f sddm = -N c / 2,..., -N c / 2 + N Δfd -1, and, N Δfd represents the number of Doppler frequency indices included in the interval of Δfd, N Δfd = round(Δfd / (1 / (T r N c ))). Additionally, round(x) is an operator that rounds the real number x and outputs an integer value.

[0398] Additionally, for example, the operation of the CFAR process can be based on the operation disclosed in Non-Patent Document 2, and the details of the operation example are omitted here.

[0399] Thus, the Doppler frequency range to be the CFAR process target in the CFAR unit 210 can be narrowed from the entire range of the Doppler frequency index range f s (for example, the range from -N c / 2 to N c / 2 - 1) to the range of Δfd, and thus the computational amount of the CFAR process can be reduced to 1 / (Nt + δ) = 1 / (N DM + δ).

[0400] Then, the CFAR unit 210 sets a threshold value in an adaptive manner, for example, and outputs the distance index f b_cfar , Doppler frequency index f sddm_cfar , and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm - 1)×N Δfd )) to the Doppler multiplexing / demultiplexing unit 211. Here, ndm = 1 to N DM + δ is an integer.

[0401] <Example operation 2 of CFAR unit 210>

[0402] In Example operation 2, the operation example of the CFAR unit 210 when the value of δ shown in Equation (3) is set to a real number that is not a positive integer in the Doppler shift unit 104 is described.

[0403] The CFAR unit 210 can calculate the power summation value of Equation (9) based on the outputs of the Doppler analysis units 209 of the first to Na-th signal processing units 206, for example, and detect power peaks that match the Doppler shift intervals respectively set for the radar transmission signals by distance index through adaptive threshold processing (CFAR processing).

[0404] Then, the CFAR unit 210 sets a threshold in an adaptive manner, for example, and indexes the distances where the received power is greater than the threshold. b_cfar , the Doppler frequency index f of the power peak that matches the Doppler frequency shift interval set to send the radar signal s_cfar (ndm), and the Doppler frequency index f s_cfar (ndm) receiving power information PowerFT(f b_cfar , f s_cfar (ndm)) is output to the Doppler multiplexing and demultiplexing unit 211. Here, ndm = 1 to N DM +δ integer.

[0405] The operation example of the CFAR unit 210 has been described above.

[0406] In the operation example of the Doppler multiplexing and demultiplexing unit 211 described later, the case where the output of the operation example 1 in the CFAR unit 210 is used is described as an example, but the present invention is not limited to this, and the output of the operation example 2 in the CFAR unit 210 may be used. When the output of the operation example 2 in the CFAR unit 210 is used, the Doppler frequency index f is output. s_cfar (ndm) is used instead of the Doppler frequency index f in the operation example 1 in the CFAR unit 210. sddm_cfar +(ndm-1)×N Δfd This is a difference, but other than that, it is the same operation and can achieve the same effect.

[0407] [Operation Example of Doppler Multiplexing and Demultiplexing Unit 211]

[0408] For example, when the value of δ shown in equation (3) is set to a positive integer in the Doppler frequency shift unit 104, the Doppler multiplexing and demultiplexing unit 211 performs the multiplication based on the distance index f input from the CFAR unit 210. b_cfar , Doppler frequency index f sddm_cfar , and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )), perform the following actions. It should be noted that ndm = 1 to N DM +δ integer.

[0409] In the following description, an operation example of the Doppler multiplexing and demultiplexing unit 211 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of the same polarization will be described. An operation example of the Doppler multiplexing and demultiplexing unit 211 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations will be described later.

[0410] Fig.17 2 is a flowchart showing an example of the demultiplexing operation of the Doppler multiplexed signal in the Doppler multiplexer demultiplexer 211. In the following, it is assumed that the Doppler velocity of the target object is within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0411] <Step A-1>

[0412] The Doppler multiplexing and demultiplexing unit 211 assumes that the reflected wave of the target object having a cross polarization with respect to the polarization of the receiving antenna is not included, and performs Nt (=N DM The Doppler multiplexed signal is demultiplexed by performing Doppler multiplexing processing.

[0413] <Step A-2>

[0414] In this case, for example, it is assumed that the distance index f is input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) contains N DM Doppler multiplexed signals with non-equal spacing.

[0415] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the 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 to N DM +δ), determine the N with the highest received power DM Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned when transmitting (for example, called "N DM Doppler frequency shift interval matching determination").

[0416] In addition, the Doppler multiplexing and demultiplexing unit 211 determines, for example, that the N DM The received level of the Doppler frequency index is different from the N first received power. DM Is the difference (or reception level ratio) between the reception levels of δ other Doppler frequency indices of the Doppler frequency index of the first Doppler frequency index a large difference (for example, the difference is greater than a threshold, or the reception level ratio is greater than a threshold) (for example, referred to as “N DM Doppler multiplexed signal reception level difference determination").

[0417] The Doppler multiplexing and demultiplexing unit 211 determines, for example, the Doppler frequency and the transmission antenna corresponding to the Doppler multiplexed signal within the range of -1 / (2Tr)≦fd<1 / (2Tr) based on these determinations.

[0418] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0419] For example, the Doppler multiplexing and demultiplexing unit 211 determines whether N DM Doppler frequency shift interval matching judgment and N DM The two conditions (e.g., the conditions of step A-2) are determined by the difference in the received level of the N Doppler multiplexed signals. DM The N received powers ranked first in the Doppler frequency shift interval matching judgment DM Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned when transmitting, and in N DM When it is determined that the corresponding reception level difference is equal to or larger than the threshold value in the Doppler multiplexed signal reception level difference determination, the condition of step A-2 is satisfied.

[0420] It can be that the Doppler multiplexing and demultiplexing unit 211 performs the processing of step A-3 when the condition of step A-2 is met, and performs the processing of step B-1 when the condition of step A-2 is not met, assuming the situation of the target reflection wave containing PL2 polarization that is cross-polarized relative to the polarization of the receiving antenna.

[0421] <Step A-3>

[0422] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with the lowest receiving level, and the N Doppler frequency indices with the highest receiving power. DM The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex(f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0423] Here, fdemul_Tx#n Indicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0424] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0425] In addition, the Doppler frequency shift amount given to each transmission antenna of the transmission antenna unit 105 in the Doppler frequency shift unit 104 of the radar transmission unit 100 is known. Therefore, the demultiplexing index information DDM_RXindex (f b_cfar ) and the difference between the Doppler frequency shift amount given to each transmitting antenna in the radar transmitting unit 100 is the Doppler frequency of the target object. Therefore, the Doppler demultiplexing unit 211 may replace the demultiplexing index information DDM_RXindex(f b_cfar ), the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) is output to the direction estimation unit 212. In this case, the direction estimation unit 212 generates demultiplexing index information DDM_RXindex (f b_cfar ), thereby being able to perform the same action.

[0426] <Step B-1>

[0427] The Doppler multiplexing and demultiplexing unit 211 assumes that the reflected wave of the target object including the PL2 polarization is cross-polarized with the polarization of the receiving antenna, and performs N PL1 Doppler multiplexed signals are demultiplexed.

[0428] <Step B-2>

[0429] In this case, for example, it is assumed that the distance index f is input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) contains N from the PL1 polarized transmitting antenna PL1 Doppler multiplexed signal.

[0430] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) received power (PowerFT(fb_cfar , f sddm_cfar +(ndm-1)×N Δfd ))(For example, ndm = 1 to N DM +δ), and determine the N with the highest received power PL1 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval assigned to the PL1 polarization transmitting antenna during transmission (for example, referred to as "PL1 polarization Doppler shift interval matching judgment").

[0431] In addition, for example, the Doppler multiplexing and demultiplexing unit 211 determines that the N PL1 The received level of the Doppler frequency index is different from the N first received power. PL1 Doppler frequency index (N DM +δ-N PL1 ) is a large difference (for example, the difference is greater than a threshold, or the reception level ratio is greater than a threshold) (for example, referred to as "PL1 polarization Doppler multiplexing signal reception level difference judgment").

[0432] The Doppler multiplexing and demultiplexing unit 211 determines, for example, the Doppler frequency and the transmission antenna corresponding to the Doppler multiplexed signal within the range of -1 / (2Tr)≦fd<1 / (2Tr) based on these determinations.

[0433] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0434] For example, the Doppler multiplexing and demultiplexing unit 211 determines whether the two conditions of PL1 polarization Doppler frequency shift interval matching determination and PL1 polarization Doppler multiplexing signal reception level difference determination (for example, the condition of step B-2) are satisfied. For example, when the N first ranked signal with the highest reception power is determined in the PL1 polarization Doppler frequency shift interval matching determination, PL1 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned to the PL1 polarized transmitting antenna during transmission, and when the corresponding reception level difference is determined to be above the threshold in the PL1 polarization Doppler multiplexed signal reception level difference judgment, the condition of step B-2 is satisfied.

[0435] It can be that the Doppler multiplexing and demultiplexing unit 211 performs the processing of step B-3 when the condition of step B-2 is met, and performs the processing of step C-1 when the condition of step B-2 is not met, assuming the situation of the target reflection wave containing PL1 polarization that is cross-polarized relative to the polarization of the receiving antenna.

[0436] In addition, in N PL1 When the number = 1, the PL1 polarization Doppler shift interval matching determination process may not be performed.

[0437] <Step B-3>

[0438] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with a small receiving level N DM +δ-N PL1 Doppler frequency indexes and received power are ranked first N PL1 The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex_ PL1 (f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0439] Here, f demul_Tx#n Indicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0440] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0441] In addition, the Doppler shift amount given to each transmission antenna of the transmission antenna unit 105 in the Doppler shift unit 104 of the radar transmission unit 100 is known. Therefore, the demultiplexing index information DDM_RXindex_ PL1 (f b_cfar ) and the difference between the Doppler frequency shift amount given to each transmitting antenna in the radar transmitting unit 100 is the Doppler frequency of the target object. Therefore, the Doppler demultiplexing unit 211 may replace the demultiplexing index information DDM_RXindex_ PL1 (fb_cfar ), the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) is output to the direction estimation unit 212. In this case, the direction estimation unit 212 generates demultiplexing index information DDM_RXindex_ PL1 (f b_cfar ), thereby being able to perform the same action.

[0442] Alternatively, the Doppler multiplexing and demultiplexing unit 211 may also multiplex the N t transmitting antennas transmitting PL1 polarized waves. PL1 The Doppler frequency shift of the Doppler multiplexed signal of each transmitting antenna is matched with the Doppler frequency index, and the PL1 polarization demultiplexing index information of the Doppler multiplexed signal is used as DDM_Rxindex_ PL1 (f b_cfar ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0443] <Step C-1>

[0444] The Doppler multiplexing and demultiplexing unit 211 assumes that the reflected wave of the target object whose PL1 polarization is cross-polarized with the polarization of the receiving antenna includes N PL2 Doppler multiplexed signals are demultiplexed.

[0445] <Step C-2>

[0446] In this case, for example, it is assumed that the distance index f is input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) contains N from the PL2 polarized transmitting antenna PL2 Doppler multiplexed signal.

[0447] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the 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 to N DM +δ), and determine the N with the highest received power PL2 Doppler frequency index (f sddm_cfar+(ndm-1)×N Δfd ) matches the Doppler shift interval assigned to the PL2 polarization transmitting antenna during transmission (for example, referred to as "PL2 polarization Doppler shift interval matching judgment").

[0448] In addition, for example, the Doppler multiplexing and demultiplexing unit 211 determines that the N PL2 The received level of the Doppler frequency index is different from the N first received power. PL2 Doppler frequency index (N DM +δ-N PL2 ) is a large difference (for example, the difference is greater than a threshold, or the reception level ratio is greater than a threshold) (for example, referred to as "PL2 polarization Doppler multiplexing signal reception level difference judgment").

[0449] The Doppler multiplexing / demultiplexing unit 211 determines the Doppler frequency and the transmission antenna within the range of -1 / (2Tr)≦fd<1 / (2Tr), for example, based on these determinations.

[0450] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0451] For example, the Doppler multiplexing and demultiplexing unit 211 determines whether the two conditions of PL2 polarization Doppler frequency shift interval matching determination and PL2 polarization Doppler multiplexing signal reception level difference determination (for example, the condition of step C-2) are satisfied. For example, when the N first ranked signal with the highest reception power is determined in the PL2 polarization Doppler frequency shift interval matching determination, PL2 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler frequency shift interval assigned to the PL2 polarized transmitting antenna during transmission, and when the corresponding reception level difference is determined to be above the threshold in the PL2 polarization Doppler multiplexed signal reception level difference judgment, the condition of step C-2 is satisfied.

[0452] If the condition of step C-2 is met, the Doppler multiplexing and demultiplexing unit 211 can perform the processing of step C-3. In addition, if the condition of step C-2 is not met, the Doppler multiplexing and demultiplexing unit 211 can determine that the received signal is a noise component or an interference component and does not output it to the direction estimation unit 212 (step D).

[0453] In addition, in N PL2 When the number = 1, the PL2 polarization Doppler shift interval matching determination process may not be performed.

[0454] <Step C-3>

[0455] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with a small receiving level N DM +δ-N PL2 Doppler frequency indexes and received power are ranked first N PL2 The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex_ PL2 (f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0456] Here, f demul_Tx#n Indicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0457] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0458] In addition, the Doppler shift amount given to each transmission antenna of the transmission antenna unit 105 in the Doppler shift unit 104 of the radar transmission unit 100 is known. Therefore, the demultiplexing index information DDM_RXindex_ PL2 (f b_cfar ) and the difference between the Doppler frequency shift amount given to each transmitting antenna in the radar transmitting unit 100 is the Doppler frequency of the target object. Therefore, the Doppler demultiplexing unit 211 may replace the demultiplexing index information DDM_RXindex_ PL2 (f b_cfar ), the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) is output to the direction estimation unit 212. In this case, the direction estimation unit 212 generates demultiplexing index information DDM_RXindex_ PL2 (fb_cfar ), thereby being able to perform the same action.

[0459] Alternatively, the Doppler multiplexing and demultiplexing unit 211 may multiplex N t transmitting antennas transmitting PL2 polarized waves. PL2 The Doppler frequency shift of the Doppler multiplexed signal of each transmitting antenna is matched with the Doppler frequency index, and the PL2 polarization demultiplexing index information of the Doppler multiplexed signal is used as DDM_Rxindex_ PL2 (f b_cfar ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0460] In the above, an operation example of the Doppler multiplexing and demultiplexing unit 211 has been described.

[0461] In addition, the distance index f input from the CFAR unit 210 b_cfar , Doppler frequency index f sddm_cfar and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) When there are multiple Doppler multiplexing and demultiplexing units 211 can perform the above-mentioned Doppler multiplexing and demultiplexing operations on the distance index, Doppler frequency index and reception power information multiple times.

[0462] [Operation Example of Direction Estimation Unit 212]

[0463] Next, Figure 5 The operation example of the direction estimation unit 212 shown in FIG. 2 is described below.

[0464] In the following description, an operation example of the direction estimation unit 212 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of the same polarization will be described. An operation example of the direction estimation unit 212 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations will be described later.

[0465] The direction estimation unit 212 generates a Doppler multiplexing and demultiplexing signal based on the information input from the Doppler multiplexing and demultiplexing unit 211 (for example, the distance index f b_cfar , demultiplexing 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 demultiplexing indexes, and the direction estimation process of the target object is performed. Here, for example, q=1 or 2.

[0466] Hereinafter, operation example 1 and operation example 2 of the direction estimation unit 212 will be described.

[0467] <Operation Example 1 of Direction Estimation Unit 212>

[0468] For example, the direction estimation unit 212 calculates the distance index f b_cfar And the demultiplexing index information DDM_Rxindex(f b_cfar ), extract the output of the Doppler analysis unit 209, and generate the virtual receiving array correlation vector h(f) of the direction estimation unit 212 shown in the following equation (10): b_cfar , DDM_Rxindex(f b_cfar )) to perform direction estimation processing.

[0469] As shown in equation (10), the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )) contains Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. The direction estimation unit 212 uses the virtual receiving array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )), the direction of the reflected wave signal from the target is estimated based on the phase difference between each transmitting and receiving antenna.

[0470] [Formula 10]

[0471]

[0472] In formula (10), h cal[b] b is an array correction value for correcting the phase deviation and amplitude deviation between the transmission antennas and the reception antennas. b = an integer from 1 to (Nt×Na).

[0473] For example, the direction estimation unit 212 performs direction estimation processing for each polarized transmission antenna from the virtual reception array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar )) extracts the received signal corresponding to the transmitting antenna with the same polarization.

[0474] For example, the PL1 polarized transmitting antennas are Tx#1 and Tx#3, the PL2 polarized transmitting antennas are Tx#2 and Tx#4, and N PL1 =2,N PL2 =2, N t=4, when the number of receiving antennas Na=4, the transmission polarization antenna extraction vector SP corresponding to the received signal of the PL1 polarization transmitting antenna is extracted PL1 , and a transmission polarization antenna extraction vector SP for extracting a received signal of a transmission antenna corresponding to PL2 polarization PL2 It can be expressed as 16(=N) using the following formula (11) and the following formula (12): t Here, the superscript T represents the vector transpose.

[0475] [Formula 11]

[0476] SP PL1 =[1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0] T (11)

[0477] [Formula 12]

[0478] SP PL2 =[0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1] T (12)

[0479] The direction estimation unit 212 uses, for example, the transmission polarization antenna extraction vector SP which extracts the received signal from the PL1 polarization transmission antenna. PL1 The element index of the element with 1 is the element index of the virtual receiving array related vector h(f b_cfar , DDM_Rxindex(f b_cfar )) extract the element components of the element index and arrange them in ascending order according to the element index, and use the arranged column vector as the virtual receiving array correlation vector h based on the PL1 polarized transmitting antenna PL1 (f b_cfar , DDM_Rxindex(f b_cfar For example, the transmitting polarization antenna extraction vector SP shown in equation (11) PL2 The first to fourth and ninth to twelfth elements of the element index of are 1. In this case, the direction estimation unit 212 obtains 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 to generate the virtual receiving array correlation vector h based on the PL1 polarized transmitting antenna PL1 (f b_cfar , DDM_Rxindex(f b_cfar )).

[0480] In addition, the direction estimation unit 212 uses, for example, the transmission polarization antenna extraction vector SP which extracts the received signal from the PL2 polarization transmission antenna. PL2 The element index of the element with 1 is the element index of the virtual receiving array related vector h(f b_cfar , DDM_Rxindex(f b_cfar )) extracts the element components of the element index and arranges them in ascending order according to the element index, and uses the arranged column vector as the virtual receiving array correlation vector h based on the PL2 polarized transmitting antenna PL2 (f b_cfar , DDM_Rxindex(f b_cfar )) is generated. Here, h PL1 (f b_cfar , DDM_Rxindex(f b_cfar )) is included N PL1 ×Na column vector, h PL2 (f b_cfar , DDM_Rxindex(f b_cfar )) is included N PL2 For example, the transmit polarization antenna extraction vector SP shown in equation (12) is PL2 The 5th to 8th and 13th to 16th elements of the element index of are 1. In this case, the direction estimation unit 212 obtains 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 indices to generate the virtual receiving array correlation vector h based on the PL2 polarized transmitting antenna PL2 (f b_cfar , DDM_Rxindex(f b_cfar )).

[0481] The direction estimation unit 212 uses, for example, a virtual receiving array correlation vector h based on the PL1 polarized transmitting antenna. PL1 (f b_cfar , DDM_Rxindex(f b_cfar )) and the virtual receiving array correlation vector h based on the PL2 polarized transmitting antenna PL2 (f b_cfar , DDM_Rxindex(f b_cfar )), change the direction within the specified angle range to estimate the evaluation function P H-PLq (θ u , f b_cfar , DDM_Rxindex(f b_cfar )) in the azimuth direction θ u, to calculate the spatial distribution of each transmit polarization. Here, q = 1 and 2.

[0482] The direction estimation unit 212 can extract a predetermined number of maximum peaks from the calculated maximum peaks of the spatial distribution of each PLq polarization in descending order, and output the azimuth direction of the maximum peak as the estimated value of the arrival direction of the PLq polarization (for example, positioning output).

[0483] In addition, regarding the direction estimation evaluation function value P H-PLq (θ u , f b_cfar , DDM_Rxindex(f b_cfar )), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0484] For example, when the number of virtual receiving antennas based on the PLq polarized transmitting antenna is N PLq When there are ×Na and they are arranged linearly at equal intervals dH, the beamforming method can be expressed as in the following equation (13). In addition to the beamforming method, methods such as Capon and MUSIC can also be applied in the same manner.

[0485] [Formula 13]

[0486]

[0487] In formula (13), the superscript H is the Hermitian transposition operator. In addition, in formula (13), a PLq (θ u ) represents the azimuth direction θ at the center frequency fc of the radar signal u The direction vector of the virtual receiving array based on the PLq polarized transmitting antenna of the arriving wave is, as shown in equation (14), PLq ×Na elements. In equation (14), λ is the center frequency f c The wavelength of the radar signal (e.g., chirp signal) transmitted at the time, λ = C0 / f c .

[0488] [Formula 14]

[0489]

[0490] In addition, the azimuth direction θ u is a vector that changes at a predetermined azimuth interval β1 within the azimuth range for estimating the direction of arrival. For example, θ is set as follows u .

[0491] θ u=θ min +uβ1, integer u=0~NU

[0492] NU=floor[(θmax-θmin) / β1]+1

[0493] Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0494] In addition, in the above example, the direction estimation unit 212 calculates the azimuth direction as an example of an estimated value of the direction of arrival, but it is not limited to this, and the direction of arrival in the elevation direction may be estimated, or the direction of arrival in the azimuth direction and the elevation direction may be estimated by using MIMO antennas arranged in a rectangular grid. For example, the direction estimation unit 212 may calculate the azimuth direction and the elevation direction as the estimated value of the direction of arrival for different polarized transmitting antennas, and output them as positioning.

[0495] Through the above operations, the direction estimation unit 212 of the radar device 10 can output the distance index f as a positioning output, for example. b_cfar , demultiplexing index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ) for each different polarized transmitting antenna. In addition, as a positioning output, the direction estimation unit 212 can also output the distance index f b_cfar And the demultiplexing index information DDM_Rxindex(f b_cfar ).

[0496] In addition, the direction estimation unit 212 may also use the demultiplexing index information DDM_Rxindex(f b_cfar ), and outputs the Doppler frequency estimate of the target.

[0497] Alternatively, the distance index f can be converted to b_cfar Convert it into distance information and output it.

[0498] In addition, the information input from the Doppler multiplexing and demultiplexing unit 211 (for example, the distance index f b_cfar , and demultiplexing index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt )) When there are multiple ones, the direction estimation unit 212 can calculate the arrival direction estimation values ​​for them in the same way as the above processing and output the positioning results.

[0499] <Operation Example 2 of Direction Estimation Unit 212>

[0500] For example, the direction estimation unit 212 calculates the distance index f b_cfar And the demultiplexing index information DDM_Rxindex_PLq(f b_cfar ), extract the output of the Doppler analysis unit 209, and generate the virtual receiving array correlation vector h of the direction estimation unit 212 PLq (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) and perform direction estimation processing. Here, q=1 or 2. For example, the direction estimation unit 212 performs demultiplexing with the Doppler multiplexed signal index information DDM_Rxindex_PLq(f b_cfar ) is used to estimate the direction of the polarization (PLq polarization) corresponding to the consistent q.

[0501] For example, the direction estimation unit 212 uses the transmission polarization antenna extraction vector SP for extracting the reception signal corresponding to the transmission antenna of PLq polarization in order to perform the direction estimation process based on the reception signal corresponding to the radar transmission signal from the PLq polarization transmission antenna. PLq The element index of the element with 1 is the element index of the virtual receiving array related vector h(f b_cfar , DDM_Rxindex_PLq(f b_cfar )) extracts the element components of the element index and arranges them in ascending order according to the element index, and uses the arranged column vector as h PLq (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) is generated. Here, h PLq (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) is a PLq ×Na-element column vector.

[0502] The direction estimation unit 212 uses, for example, a virtual reception array correlation vector h based on the received signal corresponding to the PLq polarized transmission antenna. PLq (f b_cfar , DDM_Rxindex_PLq(f b_cfar )), change the direction within the specified angle range to estimate the evaluation function P H-PLq (θ u , f b_cfar , DDM_Rxindex_PLq(f b_cfar )) in the azimuth direction θ u, to calculate the spatial distribution of each transmit polarization. Here, q = 1 or 2.

[0503] The direction estimation unit 212 can extract a specified number of maximum peaks from the maximum peaks of the spatial distribution of the received signal corresponding to the PLq polarized transmitting antenna calculated in descending order, and output the azimuth direction of the maximum peak as the arrival direction estimation value of the PLq polarized transmission (for example, positioning output).

[0504] In addition, regarding the direction estimation evaluation function value P H-PLq (θ u , f b_cfar , DDM_Rxindex_PLq(f b_cfar )), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0505] In addition, in the above example, the direction estimation unit 212 calculates the azimuth direction as an example of the estimated value of the arrival direction, but it is not limited to this. The arrival direction estimation of the elevation direction can also be performed, or the arrival direction estimation of the azimuth direction and the elevation direction can be performed by using MIMO antennas arranged in a rectangular grid. For example, the direction estimation unit 212 can also calculate the azimuth direction and the elevation direction for different polarized transmission antennas as the estimated value of the arrival direction, and output them as positioning.

[0506] Through the above operation, the direction estimation unit 212 of the radar device 10 can output the positioning result according to the distance index f b_cfar , demultiplexing index information DDM_Rxindex(f b_cfar )_PLq=(f demul_Tx#1 , ..., f demul_Tx#NDM ) from the PLq polarized transmission antenna, and outputs the estimated value of the arrival direction of the PLq polarized transmission. In addition, as a positioning output, the direction estimation unit 212 can also output the distance index f b_cfar And the demultiplexing index information DDM_Rxindex_PLq(f b_cfar ).

[0507] In addition, the direction estimation unit 212 may also use the demultiplexing index information DDM_Rxindex_PLq (f b_cfar ), and outputs the Doppler frequency estimate of the target.

[0508] Alternatively, the distance index f can be converted to b_cfar Convert it into distance information and output it.

[0509] In addition, the information input from the Doppler multiplexing and demultiplexing unit 211 (for example, the distance index f b_cfar , and the demultiplexing index information DDM_Rxindex_PLq(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt )) When there are multiple ones, the direction estimation unit 212 can calculate the arrival direction estimation values ​​for them in the same way as the above processing and output the positioning results.

[0510] In the above, operation example 1 and operation example 2 of the direction estimation unit 212 have been described.

[0511] By performing the above-mentioned operations, the direction estimation unit 212 can perform the direction estimation processing according to the corresponding output of the demultiplexing operation of the Doppler multiplexing and demultiplexing unit 211. For example, the direction estimation unit 212 can perform the direction estimation processing according to the output of the Doppler multiplexing and demultiplexing unit 211 corresponding to the following situations, namely, the situation that does not include the target object reflected wave with the polarization of the receiving antenna being cross-polarized, the situation that includes the target object reflected wave with the polarization of PL2 being cross-polarized with respect to the receiving antenna, and the situation that includes the target object reflected wave with the polarization of PL1 being cross-polarized with respect to the receiving antenna.

[0512] For example, when the reflected wave of the target object whose polarization is cross-polarized with respect to the receiving antenna is not included, the direction estimation unit 212 can perform the direction estimation process for each polarization included in the transmitting antenna. In addition, for example, when the reflected wave of the target object whose polarization is cross-polarized with respect to the receiving antenna is PL2, the direction estimation unit 212 can perform the direction estimation process for the polarized transmission of PL1. In addition, for example, when the reflected wave of the target object whose polarization is cross-polarized with respect to the receiving antenna is PL1, the direction estimation unit 212 can perform the direction estimation process for the polarized transmission of PL2.

[0513] By the operation of the direction estimation unit 212, the direction estimation result for a part of the transmission polarization is obtained according to the direction estimation processing result of each transmission polarization or the state of the reflected wave, and the direction estimation result depending on the transmission polarization is obtained. Since the reflected wave response from the target object may change according to the transmission polarization, based on such a direction estimation result depending on the transmission polarization, the radar device 10 can improve the detection performance or recognition performance of the target object.

[0514] In the above, an operation example of the direction estimation unit has been described.

[0515] As described above, in the present embodiment, when transmitting antennas of different polarizations are used in a polarization MIMO radar using unequally spaced Doppler multiplexing, the radar device 10 can perform Doppler multiplexing demultiplexing even when receiving a reflected wave whose reception level is significantly attenuated compared to the reception level of a reflected wave from a transmitting antenna of a certain polarization, thereby suppressing degradation of target detection performance, misestimation of Doppler frequency, and degradation of angle measurement performance.

[0516] For example, when the above-mentioned conditions 1 and 2 are met, in the radar device 10, the detectable Doppler frequency range fd is in the range of -1 / (2Tr)≦fd<1 / (2Tr), that is, it can be expanded to a larger range than the detectable Doppler frequency range of -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr) in the equally spaced Doppler multiplexing.

[0517] Therefore, according to the present embodiment, the detection performance of the polarization MIMO radar using non-uniformly spaced Doppler multiplexing transmission can be improved.

[0518] In addition, in the present embodiment, the radar device 10 has a receiving antenna that uses one of a plurality of polarizations (for example, PL1 polarization and PL2 polarization) to receive a reflected wave signal formed by the radar transmission signal reflected from the target object. In addition, the radar device 10 estimates the direction based on the reflected wave signal received by the receiving antenna. Thus, even in the case of a reflected wave that includes a cross-polarization relationship with the polarization of the receiving antenna, the radar device 10 can identify the transmitting antenna corresponding to the Doppler multiplexed signal, and can resolve the ambiguity of the Doppler frequency. In addition, in the present embodiment, even if the receiving antennas are all receiving antennas of the same polarization, Doppler multiplexing can be demultiplexed, so there is no need to use different types of polarized receiving antennas in the radar receiving unit 200, and the number of receiving antennas can be reduced.

[0519] (Variation 1 of Implementation Example 1)

[0520] In the embodiment, as an example, an operation example of the CFAR unit 210, the Doppler multiplexing / demultiplexing unit 211, and the direction estimation unit 212 is described when the multiple receiving antennas of the receiving antenna unit 202 are receiving antennas of the same polarization.

[0521] The multiple receiving antennas of the receiving antenna unit 202 may include receiving antennas of different polarizations. In Modification 1 of Embodiment 1, an operation example of the CFAR unit, the Doppler multiplexing / demultiplexing unit, and the direction estimation unit is described when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations.

[0522] For example, when multiple receiving antennas include receiving antennas with different polarizations, the receiving levels of target reflected waves may be greatly different according to the different polarizations. Therefore, for example, the radar device 10 may perform CFAR processing, Doppler demultiplexing processing, and direction estimation processing on the outputs of the Doppler analysis unit 209 corresponding to the receiving antennas with different polarizations.

[0523] Alternatively, the direction estimation process may be performed using the output of the Doppler demultiplexing process using a plurality of polarized receiving antennas.

[0524] Hereinafter, as an example, a case where the receiving antennas Rx#1 to Rx#Na of the receiving antenna unit 202 include at least two receiving antennas with different polarizations will be described.

[0525] For example, two different polarizations are expressed as "RxPL1 polarization" and "RxPL2 polarization". Also, suppose that among Na receiving antennas, the number of receiving antennas for RxPL1 polarization is N. RxPL1 The number of receiving antennas with RxPL2 polarization is N RxPL2 Here, N RxPL1 +N RxPL2 =Na.

[0526] Fig.18 This is a block diagram showing a configuration example of a CFAR unit 210 a , a Doppler multiplexing / demultiplexing unit 211 a , and a direction estimating unit 212 a of a radar receiving unit 200 a in a radar device 10 according to a first modification of the first embodiment.

[0527] exist Fig.18 As an example, receiving antennas Rx#1 to Rx#N RxPL1 RxPL1 polarized receiving antenna, Rx#N RxPL1 +1~Rx#Na are RxPL2 polarized receiving antennas. In addition, the relationship between the number of receiving antennas and polarization is not limited to Fig.18 Example shown.

[0528] In addition, if Fig.18 As shown, the peak detection result of each receiving antenna with the same polarization can be used to perform Doppler multiplexing demultiplexing. In addition, the power addition operation between two receiving antennas with different polarizations does not need to be performed, so the amount of calculation in the radar receiving unit 200a can be reduced.

[0529] For example, among the outputs of the Na Doppler analysis unit 209, the 1st to the Nth RxPL1The output of the Doppler analysis unit 209 corresponds to the reception signal of the RxPL1 polarized reception antenna, and is input to the first CFAR unit 210 a - 1 that performs CFAR processing on the reception signal of the RxPL1 polarization.

[0530] For example, among the outputs of the Na Doppler analysis unit 209, the Rx#N RxPL1 The outputs of the +1st to Nath Doppler analysis units 209 correspond to the reception signal of the RxPL2 polarized reception antenna, and are input to the second CFAR unit 210 a - 2 that performs CFAR processing on the reception signal of the RxPL2 polarization.

[0531] For example, with Figure 5 Compared with the CFAR unit 210 of FIG. 1 , the operation of the first CFAR unit 210a-1 is the same as that of the first to Nth CFAR units. RxPL1 The output of the Doppler analysis unit 209 is input to the first CFAR unit 210a-1, and the power addition value is calculated using the following equation (15) instead of equation (9). Other actions may be the same as those of the above-mentioned CFAR unit 210.

[0532] [Formula 15]

[0533]

[0534] For example, with Figure 5 Compared with the CFAR unit 210 of the first embodiment, the operation of the second CFAR unit 210a-2 is RxPL1 The difference is that the output of the +1 to Na Doppler analysis unit 209 is input to the second CFAR unit 210a-2, and the power addition value is calculated using the following equation (16) instead of equation (9). Other operations can be the same as the above-mentioned CFAR unit 210.

[0535] [Formula 16]

[0536]

[0537] For example, when δ shown in equation (3) is set to a positive integer, the first Doppler demultiplexing unit 211 a - 1 generates a Doppler multiplexing / demultiplexing unit 211 a - 1 based on the distance index f input from the first CFAR unit 210 a - 1. b_cfar , 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)), demultiplexing operation of Doppler multiplexed signal for the received signal of RxPL1 polarized receiving antenna is performed. In addition, ndm = 1 to N DM +δ integer. Figure 5 Compared with the Doppler multiplexing and demultiplexing unit 211, the operation of the first Doppler multiplexing and demultiplexing unit 211a-1 is different in that the reception power information based on the formula (15) is used, and the other operations can be the same as the operation of the Doppler multiplexing and demultiplexing unit 211.

[0538] For example, when δ shown in equation (3) is set to a positive integer, the second Doppler demultiplexing unit 211 a - 2 generates a Doppler multiplexing / demultiplexing unit based on the distance index f input from the second CFAR unit 210 a - 2. b_cfar , 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 )) performs demultiplexing of the Doppler multiplexed signal for the received signal of the RxPL2 polarized receiving antenna. In addition, ndm = 1 to N DM +δ integer. Figure 5 Compared with the Doppler multiplexing and demultiplexing unit 211, the second Doppler multiplexing and demultiplexing unit 211a-2 is different in that it uses the reception power information based on the formula (16), and the other operations can be the same as the operations of the Doppler multiplexing and demultiplexing unit 211.

[0539] Next, an operation example of the first direction estimation unit 212 a - 1 and the second direction estimation unit 212 a - 2 will be described.

[0540] Hereinafter, the first direction estimation unit 212a-1 and the second direction estimation unit 212a-2 will be collectively described as a "y-th direction estimation unit 212a". Here, y=1 or 2.

[0541] The y-th direction estimation unit 212a generates a Doppler signal based on the information (eg, distance index f) input from the y-th Doppler multiplexing / demultiplexing unit 211a. b_cfar , demultiplexing 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 demultiplexing indices, and the target object direction estimation process is performed. Here, q=1 or 2.

[0542] Next, operation examples 1 and 2 of the y-direction estimation unit 212 a will be described.

[0543] <Operation Example 1 of the Y-Direction Estimation Unit 212a>

[0544] For example, the y-th direction estimation unit 212a calculates the distance index f as the information input from the y-th Doppler multiplexing and demultiplexing unit 211a. b_cfar And the demultiplexing index information DDM_Rxindex(f b_cfar ), extract the output of the Doppler analysis unit 209, and generate the virtual receiving array correlation vector h of the y-direction estimation unit 212a shown in the following equations (17) and (18): RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) and perform direction estimation processing. Here, y=1 or 2.

[0545] As shown in equations (17) and (18), the virtual receiving array correlation vector h of the y-direction estimation unit 212a is RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) includes the number of transmitting antennas Nt and the number of receiving antennas N with RxPLy polarization RxPLy The product of Nt×N RxPLy The y-direction estimation unit 212a uses the virtual reception array correlation vector h RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )), the direction of the reflected wave signal from the target is estimated based on the phase difference between each transmitting and receiving antenna.

[0546] [Formula 17]

[0547]

[0548] [Formula 18]

[0549]

[0550] In formula (17), h calRxPL1[bRxPL1] bRxPL1=1~(Nt×N RxPL1 ). In addition, in formula (18), h calRxPL2[bRxPL2] bRxPL2=1~(Nt×N RxPL2 ) is an integer.

[0551] For example, in order to perform the direction estimation process for each polarized transmission antenna, the y-direction estimation unit 212a calculates the virtual reception array correlation vector h RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) extracts the received signal corresponding to the transmitting antenna of the same polarization. To perform the extraction, the following operations are performed. For example, the y-direction estimation unit 212a uses the transmitting polarization antenna extraction vector SP to extract the received signal corresponding to the PL1 polarization transmitting antenna. PL1，RxPLy The element index of the element with element 1, associated vector h from the virtual receiving array RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) extract the element components of the element index and arrange them in ascending order according to the element index, and use the arranged column vector as the virtual receiving array correlation vector h based on the PL1 polarized transmitting antenna PL1，RxPLy (f b_cfar , DDM_Rxindex(f b_cfar For example, the y-direction estimation unit 212a uses the transmission polarization antenna extraction vector SP that extracts the received signal corresponding to the PL2 polarization transmission antenna. PL2，RxPLy The element index of the element with element 1, associated vector h from the virtual receiving array RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) extracts the element components of the element index and arranges them in ascending order according to the element index, and uses the arranged column vector as the virtual receiving array correlation vector h based on the PL2 polarized transmitting antenna PL2，RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is generated. Here, h PL1，RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is a PL1 ×N RxPLy A column vector of elements, h PL2，RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) is a PL2 ×N RxPLy Column vector of elements.

[0552] Here, the transmission polarization antenna extraction vector SP is set according to the polarization of each transmission antenna and the reception antenna. PLq，RxPLy, which extracts the reception signal of the receiving antenna with RxPLy polarization corresponding to the transmission signal transmitted from the transmitting antenna with PLq polarization.

[0553] For example, the transmitting antennas at PL1 polarization are Tx#1 and Tx#3, the transmitting antennas at PL2 polarization are Tx#2 and Tx#4, and N PL1 =2, N PL2 =2, N t =4, number of receiving antennas Na = 4, N RxPL1 =2, N RxPL2 =2, the case where the RxPL1 polarized receiving antennas are Rx#1 and Rx#2, and the RxPL2 polarized receiving antennas are Rx#3 and Rx#4 is described below.

[0554] In this case, the transmission polarization antenna extraction vector SP corresponding to the reception signal of the PL1 polarization transmission antenna is extracted from the reception signal of the RxPL1 polarization reception antenna. PL1，RxPL1 , and extracting the transmission polarization antenna extraction vector SP corresponding to the reception signal of the PL2 polarization transmission antenna from the reception signal of the RxPL1 polarization reception antenna PL2，RxPL1 It can be expressed as 16 (=N) using the following formula (19) and the following formula (20): t In addition, the transmission polarization antenna extraction vector SP corresponding to the reception signal of the PL1 polarization transmission antenna is extracted from the reception signal of the RxPL2 polarization reception antenna PL1，RxPL2 , and extracting the transmission polarization antenna extraction vector SP corresponding to the reception signal of the PL2 polarization transmission antenna from the reception signal of the RxPL2 polarization reception antenna PL2，RxPL2 It can be expressed as 16 (=N) using the following formula (21) and the following formula (22): t Here, the superscript T indicates the vector transpose.

[0555] [Formula 19]

[0556] SP PL1，PxPL1 =[1,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0] T (19)

[0557] [Formula 20]

[0558] SP PL2，RxPL1 =[0,0,0,0,1,1,0,0,0,0,0,0,1,1,0,0] T (20)

[0559] [Formula 21]

[0560] SP PL1，RxPL2=[0,0,1,1,0,0,0,0,0,0,1,1,0,0,0,0] T (twenty one)

[0561] [Formula 22]

[0562] SP PL2，RxPL2 =[0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1] T (twenty two)

[0563] The y-direction estimation unit 212a uses, for example, a virtual reception array correlation vector h based on the PL1 polarized transmission antenna. PL1，RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )) and the virtual receiving array correlation vector h based on the PL2 polarized transmitting antenna PL2，RxPLy (f b_cfar , DDM_Rxindex(f b_cfar )), change the direction within the specified angle range to estimate the evaluation function P H-PLq，RxPLy (θ u , f b_cfar , DDM_Rxindex(f b_cfar )) in the azimuth direction θ u , to calculate the spatial distribution of each transmit polarization. Here, q = 1 and 2.

[0564] The y-direction estimation unit 212a can extract a predetermined number of maximum peaks from the calculated maximum peaks of the spatial distribution of each PLq polarization in descending order, and output the azimuth direction of the maximum peak as the estimated value of the arrival direction of the receiving antenna based on the RxPLy polarization of each PLq polarization (for example, positioning output). Here, q=1 and 2.

[0565] In addition, regarding the direction estimation evaluation function value P H-PLq，RxPL1 (θ u , f b_cfar , DDM_Rxindex(f b_cfar )), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0566] For example, when the number of virtual receiving antennas based on the PLq polarized transmitting antenna is N PLq ×N RxPL1 When the number of φ1 and φ2 is arranged linearly at equal intervals dH, the beam forming method can be expressed as in the following equation (23). In addition to the beam forming method, methods such as Capon and MUSIC can also be applied.

[0567] [Formula 23]

[0568]

[0569] In formula (23), the superscript H is the Hermitian transposition operator. In addition, in formula (23), a PLq，RxPLy (θ u ) represents the azimuth direction θ at the center frequency fc of the radar signal u The direction vector of the virtual receiving array based on the PLq polarized transmitting antenna and the RxPLy polarized receiving antenna of the arriving wave, and as shown in formula (24), it is a virtual receiving array with N PLq ×N RxPLy In equation (24), λ is the center frequency f c The wavelength of the radar signal (e.g., chirp signal) transmitted at the time, λ = C0 / f c .

[0570] [Equation 24]

[0571]

[0572] In addition, the azimuth direction θ u is a vector that changes at a predetermined azimuth interval β1 within the azimuth range for estimating the direction of arrival. For example, θ is set as follows u .

[0573] θ u =θ min +uβ1, integer u=0~NU

[0574] NU=floor[(θmax-θmin) / β1]+1

[0575] Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0576] In addition, in the above example, the y-direction estimation unit 212a calculates the azimuth direction as an example of an estimated value of the direction of arrival, but the present invention is not limited thereto, and the direction of arrival in the elevation direction may be estimated, or the direction of arrival in the azimuth direction and the elevation direction may be estimated by using MIMO antennas arranged in a rectangular grid. For example, the y-direction estimation unit 212a may calculate the azimuth direction and the elevation direction for different polarized transmitting antennas as the estimated value of the direction of arrival of the receiving antenna based on the RxPLy polarization, and output it as positioning.

[0577] Through the above operation, the y-th direction estimation unit 212a can output, as a positioning output, for example, the distance index f that is input from the y-th Doppler multiplexing and demultiplexing unit 211a. b_cfar, demultiplexing index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ) for each different polarized transmitting antenna and the estimated value of the arrival direction based on the receiving antenna with RxPLy polarization. In addition, as the positioning output, the y-direction estimation unit 212a can also output the distance index f b_cfar , demultiplexing index information DDM_Rxindex(f b_cfar ).

[0578] In addition, the y-direction estimation unit 212a may also determine the demultiplexing index information DDM_Rxindex(f b_cfar ), and outputs the Doppler frequency estimate of the target.

[0579] Alternatively, the distance index f can be converted to b_cfar Convert it into distance information and output it.

[0580] In addition, the information input from the y-th Doppler multiplexing and demultiplexing unit 211a (for example, the distance index f b_cfar , and demultiplexing index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt )) When there are multiple y-direction estimation units 212a can calculate the estimated values ​​of the arrival directions for them in the same way as the above processing and output the positioning results.

[0581] <Operation Example 2 of the Y-Direction Estimation Unit 212a>

[0582] For example, the y-th direction estimation unit 212a uses the distance index f input from the y-th Doppler multiplexing and demultiplexing unit 211a. b_cfar And the demultiplexing index information DDM_Rxindex_PLq(f b_cfar ), extract the output of the Doppler analysis unit 209, and generate a virtual receiving array correlation vector h based on the PLq polarized transmitting antenna PLq，RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) and perform direction estimation processing. Here, q=1 or 2. For example, the y-th direction estimation unit 212a performs demultiplexing with the Doppler multiplexed signal index information DDM_Rxindex_PLq(f b_cfar ) is used to estimate the direction of the polarization (PLq polarization) corresponding to the consistent q.

[0583] For example, the y-direction estimation unit 212a can use the transmission polarization antenna extraction vector SP for extracting the reception signal corresponding to the transmission antenna of PLq polarization in order to perform direction estimation processing based on the reception signal received by the reception antenna of RxPLy polarization corresponding to the radar transmission signal from the transmission antenna of PLq polarization. PLq，RxPLy The element index of the element with element 1, associated vector h from the virtual receiving array RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) (for example, in equation (17) or equation (18)), the element components of the element index are extracted and arranged in ascending order according to the element index, and the arranged column vectors are used as the virtual receiving array correlation vector h based on the PLq polarized transmitting antenna PLq，RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) is generated. Here, h PLq，RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )) is a PLq ×N RxPLy Column vector of elements.

[0584] The y-direction estimation unit 212a uses a virtual reception array correlation vector h based on a reception signal transmitted from a transmission antenna of PLq polarization and received by a reception antenna of RxPLy polarization. PLq，RxPLy (f b_cfar , DDM_Rxindex_PLq(f b_cfar )), change the direction within the specified angle range to estimate the evaluation function P H-PLq，RxPLy (θ u , f b_cfar , DDM_Rxindex_PLq(f b_cfar )) in the azimuth direction θ u , to calculate the spatial distribution of PLq transmission polarization. Here, q = 1 or 2.

[0585] The y-direction estimation unit 212a can extract a specified number of maximum peaks from the maximum peaks of the spatial distribution of the received signal corresponding to the PLq polarized transmitting antenna calculated in descending order, and use the azimuth direction of the maximum peak as the arrival direction estimation value (for example, positioning output) when it is received by PLq polarization transmission and RxPLy polarization reception for positioning output.

[0586] In addition, regarding 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 based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0587] In addition, in the above example, the y-direction estimation unit 212a calculates the azimuth direction as an example of an estimated value of the arrival direction, but it is not limited to this, and the arrival direction estimation in the elevation direction may also be performed, or the arrival direction estimation in the azimuth direction and the elevation direction may be performed by using MIMO antennas arranged in a rectangular grid. For example, the y-direction estimation unit 212a may also calculate the azimuth direction and the elevation direction for different polarized transmitting antennas as the estimated value of the arrival direction of the receiving antenna based on the RxPLy polarization, and output them as positioning.

[0588] Through the above operation, the y-th direction estimation unit 212a can output the positioning result according to the distance index f input from the y-th Doppler multiplexing and demultiplexing unit 211a. b_cfar , demultiplexing index information DDM_Rxindex_PLq(f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ) from the PLq polarized transmitting antenna, and outputs the estimated value of the arrival direction based on the RxPLy polarized receiving antenna for the PLq polarized transmission. In addition, as the positioning output, the y-direction estimation unit 212a can also output the distance index f b_cfar , demultiplexing index information DDM_Rxindex_PLq(f b_cfar ).

[0589] In addition, the direction estimation unit 212a may also use the demultiplexing index information DDM_Rxindex_PLq(f b_cfar ), and outputs the Doppler frequency estimate of the target.

[0590] Alternatively, the distance index f can be converted to b_cfar Convert it into distance information and output it.

[0591] In addition, the information input from the Doppler multiplexing and demultiplexing unit 211 (for example, the distance index f b_cfar , and the demultiplexing index information DDM_Rxindex_PLq(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 , ..., f demul_Tx#Nt)) When there are multiple y-direction estimation units 212a can calculate the estimated values ​​of the arrival directions for them in the same way as the above processing and output the positioning results.

[0592] In the above, the operation examples 1 and 2 of the y-direction estimation unit 212 a have been described.

[0593] The y-direction estimation unit 212a can obtain the direction estimation result based on the RxPLy polarized receiving antenna for a part of the transmission polarization according to the result of the direction estimation processing based on the RxPLy polarized receiving antenna for each transmission polarization or the state of the reflected wave through the above-mentioned operation, and can obtain the direction estimation result depending on the transmission polarized antenna and the receiving polarized antenna. Since the reflected wave response from the target object may vary depending on the transmission polarization and the receiving polarization, based on such a direction estimation result depending on the transmission and reception polarizations, the radar device 10 can improve the detection performance or recognition performance of the target object.

[0594] Here, the y-th direction estimation unit 212a performs the multiplication based on the information (for example, the distance index f) input from the y-th Doppler multiplexing / demultiplexing unit 211a. b_cfar , demultiplexing 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 demultiplexing indices, and the direction estimation processing of the target object is performed, but not limited to this.

[0595] For example, the y-direction estimating unit 212a may determine the distance index f according to the information input from the first Doppler multiplexing / demultiplexing unit 211a-1 (for example, the distance index f b_cfar , demultiplexing 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 demultiplexing indices, and the information input from the second Doppler demultiplexing unit 211a-2 (for example, the distance index f b_cfar , demultiplexing 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 demultiplexing indices, perform object direction estimation processing.

[0596] For example, the y-direction estimation unit 212a uses the information input from the first Doppler multiplexing and demultiplexing unit 211a-1 to calculate the virtual reception array correlation vector h based on the reception signal transmitted from the transmission antenna of PL1 polarization and received by the reception antenna of RxPL1 polarization. PL1，RxPL1 (f b_cfar , DDM_Rxindex(f b_cfar )). In addition, the y-direction estimation unit 212a uses the information input from the second Doppler multiplexing and demultiplexing unit 211a-2 to calculate the virtual reception array correlation vector h based on the reception signal transmitted from the transmission antenna of PL2 polarization and received by the reception antenna of RxPL2 polarization. PL2，RxPL2 (f b_cfar , DDM_Rxindex(f b_cfar )). Then, the y-direction estimation unit 212a may be configured to estimate 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 )) to estimate the direction of the target object.

[0597] Alternatively, for example, the y-direction estimation unit 212a uses the information input from the first Doppler multiplexing and demultiplexing unit 211a-1 to calculate a virtual reception array correlation vector h based on a reception signal transmitted from a transmission antenna of PL2 polarization and received by a reception antenna of RxPL1 polarization. PL2，RxPL1 (f b_cfar , DDM_Rxindex(f b_cfar )). In addition, the y-direction estimation unit 212a uses the information input from the second Doppler multiplexing and demultiplexing unit 211a-2 to calculate the virtual reception array correlation vector h based on the reception signal transmitted from the transmission antenna of PL1 polarization and received by the reception antenna of RxPL2 polarization. PL1，RxPL2 (f b_cfar , DDM_Rxindex(f b_cfar )). Then, the y-direction estimation unit 212a may be configured to estimate the virtual receiving array correlation vector h PL2，RxPL1 (f b_cfar , DDM_Rxindex(fb_cfar )) and h PL1，RxPL2 (f b_cfar , DDM_Rxindex(f b_cfar )) to estimate the direction of the target object.

[0598] (Variation 2 of Implementation Example 1)

[0599] In implementation mode 1, the operation of performing unequally spaced Doppler multiplexing transmission using the Nt transmitting antennas of the transmitting antenna unit 105 and the operation of using Doppler multiplexing transmission (DDM) that satisfies conditions 1 and 2 to multiplex and transmit Doppler multiplexed signals to which the Doppler frequency shift amount is assigned by the Doppler frequency shift unit 104 simultaneously from the Nt transmitting antennas is described, but the operation is not limited thereto.

[0600] In variant example 2 of implementation example 1, for example, non-uniformly spaced Doppler multiplexing transmission may be performed using Nt transmitting antennas of the transmitting antenna unit 105, and Doppler multiplexing transmission (DDM) that does not satisfy condition 1 but satisfies condition 2 may be used to multiplex and transmit Doppler multiplexed signals to which Doppler frequency shift amounts are assigned by the Doppler frequency shift unit 104 simultaneously from the Nt transmitting antennas.

[0601] By setting the Doppler shift amount in the Doppler shift unit 104 in this way, for example, the operation in <step B-1> or <step C-1> in the Doppler multiplexing and demultiplexing unit 211 differs in that the demultiplexing operation of Doppler multiplexing of Doppler multiplexed signals at equal intervals is included.

[0602] Here, if the Doppler frequency range of the assumed target object is within the detectable Doppler frequency range as described below, the radar device 10 can demultiplex the Doppler multiplexed signal by the conventional demultiplexing operation of the equally spaced Doppler multiplexed signal.

[0603] For example, as examples of a case where the Doppler multiplexed signal to which the Doppler frequency shift amount is given by the Doppler frequency shift unit 104 does not satisfy the condition 1, the following three cases can be cited.

[0604] (Case 1)

[0605] PL1 polarization and PL2 polarization are the cases of equally spaced Doppler multiplexing (where N PL1 ≧2, N PL2 ≧2). In this case, the detectable Doppler frequency range fd is -1 / (2max(N PL1 , N PL2 )Tr)≦fd<1 / (2max(N PL1 , N PL2 )Tr) This range. Here, max(N PL1 , N PL2) is to return N PL1 and N PL2 The function of the larger value in N PL1 and N PL2 If they are equal, either value can be output).

[0606] (Case 2)

[0607] The case where unequally spaced Doppler multiplexing is used under PL1 polarization and equally spaced Doppler multiplexing is used under PL2 polarization (where N PL1 ≧2, N PL2 ≧2). In this case, the detectable Doppler frequency range fd is -1 / (2N PL2 Tr)≦fd<1 / (2N PL2 Tr) this range.

[0608] (Case 3)

[0609] PL1 polarization is the case of equal-interval Doppler multiplexing, and PL2 polarization is the case of unequal-interval Doppler multiplexing (where N PL1 ≧2, N PL2 ≧2). In this case, the detectable Doppler frequency range fd is -1 / (2N PL1 Tr)≦fd<1 / (2N PL1 Tr) this range.

[0610] For example, when conditions 1 and 2 are satisfied, the Doppler frequency range fd of the detectable target object is -1 / (2Tr)≦fd<1 / (2Tr). On the other hand, when condition 2 is satisfied, although the Doppler frequency range fd of the detectable target object becomes smaller than when conditions 1 and 2 are satisfied, regardless of which of conditions 1 to 3, the Doppler detectable range can be expanded to a larger range than the Doppler detection range of the existing equally spaced Doppler multiplexing, -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr).

[0611] Thus, by using Doppler multiplexing transmission (DDM) that satisfies condition 2, the same effect as that of embodiment 1 can be obtained. For example, when using transmitting antennas of different polarizations in a polarization MIMO radar using unequally spaced Doppler multiplexing, even when receiving a reflected wave whose reception level from a transmitting antenna of another polarization is greatly attenuated compared to the reception level of a reflected wave from a transmitting antenna of a certain polarization, the radar device 10 can perform demultiplexing of the Doppler multiplexing, and can suppress degradation of the target detection performance, misestimation of the Doppler frequency, and degradation of the angle measurement performance.

[0612] Hereinafter, a setting example of the Doppler shift amount of the Doppler shift unit 104 in the second modification will be described.

[0613] <Doppler shift amount setting example 7>

[0614] In setting example 7, a case where non-uniform-interval Doppler multiplexing is used for PL1 polarization and uniform-interval Doppler multiplexing is used for PL2 polarization is described.

[0615] Fig.19 Indicates the number of transmitting antennas Nt = 4, N PL1 =2, N PL2 An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =2. Fig.19 In the figure, Tx#1 and Tx#3 are PL1 polarized transmitting antennas, and Tx#2 and Tx#4 are PL2 polarized transmitting antennas.

[0616] In the seventh setting example of the Doppler frequency shift amount, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (6Tr), δ=2, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0617] exist Fig.19 In the example shown, the first to fourth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 4 ) can perform the following operations.

[0618] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0619] For example, in order to provide the Doppler shift amount DOP2 = -1 / (3Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -2π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0620] For example, in order to provide the Doppler shift amount DOP3 = -1 / (6Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0621] For example, in order to provide the Doppler shift amount DOP4=1 / (6Tr) to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 provides a phase rotation of Φ4(m)=π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0622] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0623] exist Fig.19 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna Tx#1 to Tx#4 is Δfd (1，2) =Δfd (2，3) =Δfd,Δfd (3，4) =Δfd (4，1) =2Δfd. Therefore, Fig.19 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=4 are not all the same, but include unequal intervals (for example, Δfd (1，2) =Δfd (2，3) ≠Δfd (3，4) =Δfd (4，1) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0624] In addition, Fig.19 The interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#3 with PL1 polarization is Δfd (1，3) =2Δfd,Δfd (3，1) =4Δfd. Therefore, the number of PL1 polarized transmitting antennas is N PL1 = 2, the intervals of the Doppler frequency shift amounts given by the PL1 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (1，3) ≠Δfd (3，1) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL1 polarized transmitting antenna.

[0625] In addition, Fig.19 In the example, the interval of the Doppler frequency shift between the transmitting antennas Tx#2 and Tx#4 with PL2 polarization is Δfd. (2，4) =3Δfd,Δfd (4，2) =3Δfd. Therefore, the number of PL2 polarized transmitting antennas is N PL2 = 2, the intervals between the Doppler frequency shift amounts given by the PL2 polarized transmission antennas are all the same (Δfd (2，4) =Δfd (4，2) ), so it is an equally spaced Doppler multiplexing transmission (equally spaced DDM transmission) performed by the PL2 polarized transmitting antenna.

[0626] therefore, Fig.19 The example shown is a setting example of a pattern of the Doppler shift amount that does not satisfy condition 1.

[0627] In addition, Fig.19 In the example, the Doppler frequency shift interval between the PL1 polarized transmitting antennas Tx#1 and Tx#3 is Δfd (1，3) =2Δfd,Δfd (3，1) =4Δfd, the interval of Doppler frequency shift between PL2 polarized transmitting antennas Tx#2 and Tx#4 is Δfd (2，4) =Δfd (4，2) =3Δfd Therefore, the Doppler shift amount between the PL1 polarized transmission antennas Tx#1 and Tx#3 and the Doppler shift amount between the PL2 polarized transmission antennas Tx#2 and Tx#4 include different Doppler shift intervals.

[0628] For example, the interval between the Doppler frequency shift amounts of PL1 polarized transmission antennas Tx#1 and Tx#3 includes 2Δfd and 4Δfd, but the interval between the Doppler frequency shift amounts of PL2 polarized transmission antennas Tx#2 and Tx#4 does not include 2Δfd and 4Δfd.

[0629] For example, the maximum DDM interval of the Doppler shift amount between PL2 polarized transmission antennas Tx#2 and Tx#4 is 3Δfd, but the interval of the Doppler shift amount between PL1 polarized transmission antennas Tx#1 and Tx#3 does not include 3Δfd.

[0630] As mentioned above, in Fig.19 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0631] therefore, Fig.19 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2 (1).

[0632] For example, in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the PL1 polarization transmission antenna (Tx#1 and Tx#3) and the PL2 polarization transmission antenna (Tx#2 and Tx#4) at approximately the same level. Here, for the signals transmitted from the Nt transmission antennas Tx#1 to Tx#4 composed of the PL1 polarization transmission antenna and the PL2 polarization transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 (for example, the Doppler multiplexing demultiplexing unit 211) can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0633] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0634] In addition, in the case of a target object reflection wave whose polarization relative to the receiving antenna is cross-polarized, in the case of a target object reflection wave whose PL1 polarization is cross-polarized and in the case of a target object reflection wave whose PL2 polarization is cross-polarized, the radar device 10 receives different Doppler multiplexed signals (for example, a Doppler multiplexed signal that satisfies condition 2 (1)).

[0635] For example, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0636] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 whether a reduction in the reception level of the reception signal corresponding to the PL1 polarized transmitting antenna or a reduction in the reception level of the reception signal corresponding to the PL2 polarized transmitting antenna has occurred based on the detected Doppler frequency peak value (for example, the interval between the peaks).

[0637] For example, for the Doppler multiplexed signal of PL1 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL1 polarized transmission antenna, the radar device 10 can use the existing demultiplexing operation of the Doppler multiplexed signal to determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), demultiplex the Doppler multiplexed signal, and obtain an output that corresponds to the transmission antenna for each Doppler multiplexed signal.

[0638] In addition, for example, for the Doppler multiplexed signal of PL2 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes an equal interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL2 polarization transmission antenna, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (4Tr)≦fd<1 / (4Tr), and can obtain an output that corresponds to the transmission antenna for each Doppler multiplexed signal.

[0639] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can identify the Doppler frequency fd of the target object and obtain an output in which the transmission antenna is associated with each Doppler multiplexed signal.

[0640] <Doppler shift amount setting example 8>

[0641] In setting example 8, a case where equal-interval Doppler multiplexing is used for PL1 polarization and unequal-interval Doppler multiplexing is used for PL2 polarization is described.

[0642] Fig. 20 Indicates the number of transmitting antennas Nt = 4, N PL1 =2, N PL2 An example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency when =2. Fig. 20 In the figure, Tx#1 and Tx#3 are PL1 polarized transmitting antennas, and Tx#2 and Tx#4 are PL2 polarized transmitting antennas.

[0643] In the eighth setting example of the Doppler frequency shift amount, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (6Tr), δ=2, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0644] exist Fig. 20 In the example shown, the first to fourth Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 4 ) can perform the following operations.

[0645] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0646] For example, in order to provide the Doppler shift amount DOP2 = -1 / (3Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -2π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0647] For example, in order to give the Doppler shift amount DOP3 = 0 to the third transmission antenna Tx# 3 , the third Doppler shift unit 104 gives a phase rotation Φ3(m) = 0 according to the transmission period Tr of the chirp signal and outputs it.

[0648] For example, in order to provide the fourth transmission antenna Tx#4 with the Doppler shift amount DOP4=1 / (3Tr), the fourth Doppler shift unit 104 provides a phase rotation of Φ4(m)=2π(m-1) / 3 according to the transmission period Tr of the chirp signal and outputs it.

[0649] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0650] exist Fig. 20 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna Tx#1 to Tx#4 is Δfd (1，2) =Δfd (4，1) =Δfd,Δfd (2，3) =Δfd (3，4) =2Δfd. Therefore, Fig. 20 In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas when the number of transmitting antennas Nt=4 are not all the same, but include unequal intervals (for example, Δfd (1，2) =Δfd (4，1) ≠Δfd (2，3) =Δfd (3，4) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0651] In addition, Fig. 20 In the example, the interval of the Doppler frequency shift between the transmitting antennas Tx#1 and Tx#3 with PL1 polarization is Δfd. (1，3) =3Δfd,Δfd (3，1) =3Δfd. Therefore, the number of PL1 polarized transmitting antennas is N PL1 = 2, the intervals between the Doppler frequency shift amounts given by the PL1 polarization transmitting antennas are all the same (Δfd (1，3) =Δfd (3，1) ), so it is an equally spaced Doppler multiplexing transmission (equally spaced DDM transmission) performed by the PL1 polarized transmitting antenna.

[0652] In addition, Fig. 20 In the example, the interval of the Doppler frequency shift between the transmitting antennas Tx#2 and Tx#4 with PL2 polarization is Δfd. (2，4) =4Δfd,Δfd (4，2) =2Δfd. Therefore, the number of PL2 polarized transmitting antennas is N PL2 = 2, the intervals of the Doppler frequency shift amounts given by the PL2 polarized transmission antennas are not all the same, but include unequal intervals (Δfd (2，4) ≠Δfd(4，2) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by the PL2 polarization transmitting antenna.

[0653] therefore, Fig. 20 The example shown is a setting example of a pattern of the Doppler shift amount that does not satisfy condition 1.

[0654] In addition, Fig. 20 In the example, the Doppler frequency shift interval between the PL1 polarized transmitting antennas Tx#1 and Tx#3 is Δfd (1，3) =Δfd (3，1) =3Δfd, the interval of Doppler frequency shift between PL2 polarized transmitting antennas Tx#2 and Tx#4 is Δfd (2，4) =4Δfd,Δfd (4，2) =2Δfd Therefore, the Doppler shift amount between the PL1 polarized transmission antennas Tx#1 and Tx#3 and the Doppler shift amount between the PL2 polarized transmission antennas Tx#2 and Tx#4 include different Doppler shift intervals.

[0655] For example, the interval between the Doppler frequency shift amounts of the PL1 polarized transmission antennas Tx#1 and Tx#3 includes 3Δfd, but the interval between the Doppler frequency shift amounts of the PL2 polarized transmission antennas Tx#2 and Tx#4 does not include 3Δfd.

[0656] For example, the maximum DDM interval of the Doppler shift amount between PL2 polarized transmission antennas Tx#2 and Tx#4 includes 2Δfd and 4Δfd, but the interval of the Doppler shift amount between PL1 polarized transmission antennas Tx#1 and Tx#3 does not include 2Δfd and 4Δfd.

[0657] As mentioned above, in Fig. 20 In the example shown, the pattern of the Doppler frequency shift amount assigned to the PL1 polarized transmission antenna is different from the pattern of the Doppler frequency shift amount assigned to the PL2 polarized transmission antenna.

[0658] therefore, Fig. 20 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2 (1).

[0659] For example, in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the PL1 polarization transmission antenna (Tx#1 and Tx#3) and the PL2 polarization transmission antenna (Tx#2 and Tx#4) at approximately the same level. Here, for the signals transmitted from the Nt transmission antennas Tx#1 to Tx#4 composed of the PL1 polarization transmission antenna and the PL2 polarization transmission antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 (for example, the Doppler multiplexing demultiplexing unit 211) can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0660] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0661] In addition, in the case of a target object reflection wave whose polarization relative to the receiving antenna is cross-polarized, in the case of a target object reflection wave whose PL1 polarization is cross-polarized and in the case of a target object reflection wave whose PL2 polarization is cross-polarized, the radar device 10 receives different Doppler multiplexed signals (for example, a Doppler multiplexed signal that satisfies condition 2 (1)).

[0662] For example, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0663] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 whether a reduction in the reception level of the reception signal corresponding to the PL1 polarized transmitting antenna or a reduction in the reception level of the reception signal corresponding to the PL2 polarized transmitting antenna has occurred based on the detected Doppler frequency peak value (for example, the interval between the peaks).

[0664] For example, for the Doppler multiplexed signal of PL1 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes an equally spaced Doppler multiplexed signal. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL1 polarized transmission antenna, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (4Tr)≦fd<1 / (4Tr), and can obtain an output that corresponds to the transmission antenna for each Doppler multiplexed signal.

[0665] In addition, for example, for the Doppler multiplexed signal of PL2 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniform interval Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to the transmission signal transmitted by the PL2 polarization transmission antenna, the radar device 10 can use the existing demultiplexing operation of the Doppler multiplexed signal to determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr), demultiplex the Doppler multiplexed signal, and obtain an output that corresponds to the transmission antenna for each Doppler multiplexed signal.

[0666] (Variation 3 of Implementation Example 1)

[0667] In Embodiment 1, an example of using two polarizations, PL1 polarization and PL2 polarization, which are orthogonal to each other, as different polarization transmission polarizations is described, but the invention is not limited thereto, and the number of polarizations may be more than 3. For example, in addition to the two polarizations, PL1 polarization and PL2 polarization, a transmission antenna with another polarization different from PL1 polarization and PL2 polarization may be used.

[0668] For example, the radar device 10 (for example, a polarization MIMO radar) may use Nt transmission antennas including three or more transmission antennas with different polarizations including two polarizations that are orthogonal to each other.

[0669] Hereinafter, the first polarization is recorded as PL1 polarization, and the second polarization is recorded as PL2 polarization. The qth polarization is recorded as PLq polarization. In addition, it is assumed that the combination of different polarizations in a mutually orthogonal polarization relationship is PL1 polarization and PL2 polarization, for example, right-hand circular polarization and left-hand circular polarization, horizontal polarization and vertical polarization, right slant 45° polarization and left slant 45° polarization can be used.

[0670] In addition, let the number of transmitting antennas N be t ≧4. For example, let the Doppler multiplexing number N DDM ≧4.

[0671] In addition, the transmitting antenna includes N PL1 PL1 polarized antennas and N PL2 PL2 polarized antennas. In this case, N PL1 +N PL2 <Nt。

[0672] The radar device 10 performs unequally spaced Doppler multiplexing transmission using, for example, Nt transmission antennas.

[0673] In addition, the radar device 10 uses Doppler multiplexing transmission (DDM) that satisfies conditions 1a and 2a described later for Nt transmitting antennas, including transmitting antennas with cross-polarized PL1 polarization and PL2 polarization and transmitting antennas with polarization different from PL1 polarization and PL2 polarization, to perform simultaneous multiplexing transmission from the Nt transmitting antennas.

[0674] Conditions 1a and 2a are, for example, conditions in the case where a transmitting antenna having a polarization other than PL1 polarization and PL2 polarization is used in addition to the two polarizations PL1 polarization and PL2 polarization that are orthogonal to each other. For example, in the case where no transmitting antenna having a different polarization is included in addition to the two polarizations PL1 polarization and PL2 polarization that are orthogonal to each other, conditions 1a and 2a become conditions equivalent to conditions 1 and 2.

[0675] For example, the reflected waves corresponding to the radar transmission signals respectively transmitted from the transmission antennas based on the PL1 polarization and PL2 polarization, which are in a mutually orthogonal polarization relationship, are in a mutually cross-polarized relationship with respect to the receiving antenna unit 202, and therefore, there may be a case where the reception levels of the received signals are greatly different. On the other hand, among the Nt transmission antennas, the transmission antennas with other polarizations other than the PL1 polarization antenna and the PL2 polarization antenna are not in an orthogonal polarization relationship with the PL1 polarization and the PL2 polarization. Therefore, the reception level of the received signal of the reflected wave corresponding to the radar transmission signal from the transmission antennas with other polarizations is not likely to be greatly different from the reception level of the received signal corresponding to the transmission antennas with the PL1 polarization and the PL2 polarization.

[0676] Therefore, for example, in condition 1a, instead of "non-uniformly spaced Doppler multiplexing based on PL1 polarized antennas" in condition 1, "non-uniformly spaced Doppler multiplexing based on polarized transmitting antennas other than PL2 polarized antennas" can be applied. PL1 ≧2, in N PL1 = 1, no need to consider)". Similarly, in condition 1a, the "non-uniformly spaced Doppler multiplexing based on PL2 polarized antennas" in condition 1 can be replaced by "non-uniformly spaced Doppler multiplexing based on polarized transmitting antennas other than PL1 polarization (it should be noted that in N PL1 ≧2, in N PL2 =1, no need to consider)" condition.

[0677] In addition, for example, in condition 2a, instead of "between the Doppler multiplexed signals respectively assigned to the PL1 polarized transmission antenna and the PL2 polarized transmission antenna" in condition 2, "between the polarized transmission antennas respectively assigned to the PL2 polarized transmission antenna (for example, (Nt-Nt)" may be applied.PL1 ) transmit antennas) and polarized transmit antennas other than the PL1 polarized antenna (e.g., (Nt-N PL2 ) transmit antennas) between the Doppler multiplexed signals” condition.

[0678] Therefore, Condition 1a and Condition 2a can be defined as follows.

[0679] <Condition 1a>

[0680] Doppler multiplexing signals are allocated to PL1 polarization and PL2 polarization respectively in such a manner as to achieve the following non-uniformly spaced Doppler multiplexing:

[0681] Based on non-uniformly spaced DDM of transmit antennas with polarizations other than PL2 (it should be noted that in N PL1 ≧2, in N PL1 =1, no need to consider)

[0682] Based on non-uniformly spaced DDM of polarization transmitting antennas other than PL1 polarization (it should be noted that in N PL2 ≧2, in N PL2 =1, no need to consider)

[0683] <Condition 2a>

[0684] In the case where the polarizations other than PL2 polarization are respectively assigned to the transmitting antennas (for example, (Nt-N PL2 ) transmit antennas) and transmit antennas with polarizations other than PL1 polarization (e.g., (Nt-N PL1 ) between the Doppler multiplexed signals of the transmitting antennas), one of the following conditions holds.

[0685] (1) Including different Doppler shift intervals.

[0686] (2) The Doppler multiplexing number (= number of transmitting antennas) of PL1 polarization and PL2 polarization is different (N PL1 ≠N PL2 ).

[0687] (3) In Nt-N PL1 ≧3, Nt-N PL2 In the case of ≧3, when the Doppler shift intervals of the polarization transmission antennas other than the PL2 polarization and the polarization transmission antennas other than the PL1 polarization include the same Doppler shift interval, the order of the Doppler shift intervals is different.

[0688] For example, in condition 1a, on the Doppler frequency axis, the intervals of the Doppler frequency shift amounts assigned to the polarized transmission antennas other than the PL2 polarized transmission antennas are set to non-equal intervals. Similarly, in condition 1a, on the Doppler frequency axis, the intervals of the Doppler frequency shift amounts assigned to the polarized transmission antennas other than the PL1 polarized transmission antennas are set to non-equal intervals.

[0689] In addition, for example, according to condition 2a (1), the intervals of Doppler shift amounts assigned to polarized transmission antennas other than PL2 polarized transmission antennas (Doppler shift intervals) may include intervals different from the intervals of Doppler shift amounts assigned to polarized transmission antennas other than PL1 polarized transmission antennas. As examples of condition 2a (1), there may be a case where the maximum Doppler shift intervals are different between Doppler multiplexed signals assigned to polarized transmission antennas other than PL2 polarization and polarized transmission antennas other than PL1 polarization, a case where the minimum Doppler shift intervals are different, or a case where the Doppler shift intervals that are neither the maximum nor the minimum are different.

[0690] As an example of condition 2a (2), there is a case where one of the PL1 polarized transmission antenna and the PL2 polarized transmission antenna is used as one to form a SIMO (Single-Input Multiple Output) radar structure (N PL1 =1 and N PL2 ≧2, N PL1 ≧2 and N PL2 = 1), and the case where there are more than two PL1 polarized transmission antennas and two PL2 polarized transmission antennas, and the MIMO radar structure is formed by each polarized transmission antenna (N PL1 ≧2 and N PL2 ≧2, and N PL1 ≠N PL2 ).

[0691] In addition, if according to condition 2a (3), for example, the combination of the intervals of Doppler frequency shift amounts assigned to the polarized transmitting antenna other than the PL2 polarized transmitting antenna is the same as the combination of the intervals of Doppler frequency shift amounts assigned to the polarized transmitting antenna other than the PL1 polarized transmitting antenna, while the order of the intervals of Doppler frequency shift amounts assigned to the polarized transmitting antenna other than the PL2 polarized transmitting antenna in the Doppler frequency range is different from the order of the intervals of Doppler frequency shift amounts assigned to the polarized transmitting antenna other than the PL1 polarized transmitting antenna.

[0692] For example, a combination of intervals contained in a sequence (for example, a first sequence) in which the intervals of the Doppler frequency shift amounts assigned to polarized transmitting antennas other than PL1 polarization are arranged in sequence from the smaller side on the Doppler frequency axis is consistent with a combination of intervals contained in a sequence (for example, a second sequence) in which the intervals of the Doppler frequency shift amounts assigned to polarized transmitting antennas other than PL2 polarization are arranged in sequence from the smaller side on the Doppler frequency axis, and the first sequence and the second sequence are different sequences when arranged in a circle.

[0693] When condition 2a (3) is satisfied, even if one of the Doppler shift intervals of polarized transmission antennas other than PL2 polarization and the Doppler shift intervals of polarized transmission antennas other than PL1 polarization is cyclically shifted in the Doppler frequency domain, the two will not match.

[0694] Next, an example of setting the Doppler shift amount in the Doppler shift unit 104 will be described.

[0695] <Doppler shift amount setting example 9>

[0696] Fig.21 Indicates the number of transmitting antennas Nt = 7, N PL1 =3, N PL2 =3, N PL3 =1 is an example of setting the pattern of the Doppler shift amount for the transmission Doppler frequency. Fig.21 In the example, Tx#1, Tx#4 and Tx#6 are PL1 polarized antennas, Tx#2, Tx#3 and Tx#5 are PL2 polarized antennas, and Tx#3 is a PL3 polarized antenna. For example, it is assumed that PL1 polarization and PL2 polarization are polarizations that are orthogonal to each other.

[0697] In addition, in the setting example 9 of the Doppler frequency shift amount, Fig.21 As shown, the basic unit of the Doppler frequency shift interval in the Doppler frequency shift unit 104 is set to Δfd=1 / (Tr×(N DM +δ))=1 / (8Tr), δ=1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0698] exist Fig.21 In the example shown, the first to seventh Doppler shift units 104 (or Doppler shift units 104 - 1 to 104 - 7 ) can perform the following operations.

[0699] For example, in order to provide the Doppler shift amount DOP1 = -1 / (2Tr) to the first transmission antenna Tx#1, the first Doppler shift unit 104 provides a phase rotation of Φ1(m) = -π(m-1) according to the transmission period Tr of the chirp signal and outputs it.

[0700] For example, in order to provide the Doppler shift amount DOP2 = -1 / (4Tr) to the second transmission antenna Tx#2, the second Doppler shift unit 104 provides a phase rotation of Φ2(m) = -π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0701] For example, in order to provide the Doppler shift amount DOP3 = -1 / (8Tr) to the third transmission antenna Tx#3, the third Doppler shift unit 104 provides a phase rotation of Φ3(m) = -π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0702] For example, in order to give the Doppler shift amount DOP4=0 to the fourth transmission antenna Tx#4, the fourth Doppler shift unit 104 gives a phase rotation of Φ4(m)=0 according to the transmission period Tr of the chirp signal and outputs it.

[0703] For example, in order to provide the Doppler shift amount DOP5=1 / (8Tr) to the fifth transmission antenna Tx#5, the fifth Doppler shift unit 104 provides a phase rotation of Φ5(m)=π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0704] For example, in order to provide the Doppler shift amount DOP6=1 / (4Tr) to the sixth transmission antenna Tx#6, the sixth Doppler shift unit 104 provides a phase rotation of Φ6(m)=π(m-1) / 2 according to the transmission period Tr of the chirp signal and outputs it.

[0705] For example, in order to provide the Doppler shift amount DOP7=3 / (8Tr) to the seventh transmission antenna Tx#7, the seventh Doppler shift unit 104 provides a phase rotation of Φ7(m)=3π(m-1) / 4 according to the transmission period Tr of the chirp signal and outputs it.

[0706] Hereinafter, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”.

[0707] exist Fig.21 In the example, the interval (Doppler shift interval) of the Doppler frequency shift amount given to each transmitting antenna 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) =Δfd. Therefore, Fig.21In the example, the intervals of the Doppler frequency shift amounts given to the respective transmitting antennas of the number of transmitting antennas 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) ), so it is unequally spaced Doppler multiplexing transmission (unequally spaced DDM transmission).

[0708] In addition, Fig.21 In the example, the interval of the Doppler frequency shift between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7 except the PL2 polarized transmitting antenna is Δfd (1、4) =4Δfd,Δfd (4、6) =2Δfd,Δfd (6、7) =Δfd (7、1) =Δfd. Therefore, for the number of transmitting antennas other than the PL2 polarization transmitting antenna (Nt-N PL2 )=4, the intervals of the Doppler frequency shift amounts given by the polarized transmission antennas are not all the same, but include unequal intervals (Δfd (1，4) ≠Δfd (4，6) ≠Δfd (6，7) =Δfd (7，1) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by polarization transmitting antennas other than the PL2 polarization transmitting antenna.

[0709] In addition, Fig.21 In the example, the interval of the Doppler frequency shift amount (Doppler frequency shift interval) between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7 except the PL1 polarized transmitting antenna is Δfd (2，3) =Δfd,Δfd (3，5) =Δfd (5，7) =2Δfd,Δfd (7，2) =3Δfd. Therefore, for the number of transmitting antennas other than the PL1 polarization transmitting antenna (Nt-N PL1 )=4, the intervals of the Doppler frequency shift amounts given by the polarized transmission antennas are not all the same, but include unequal intervals (Δfd (2，3) ≠Δfd (3，5) =Δfd (5，7) ≠Δfd (7，2) ), so it is non-equally spaced Doppler multiplexing transmission (non-equally spaced DDM transmission) performed by polarization transmitting antennas other than the PL1 polarization transmitting antenna.

[0710] therefore, Fig.21 The example shown is a setting example of the pattern of the Doppler shift amount that satisfies condition 1a.

[0711] In addition, Fig.21 In the example, the Doppler frequency shift between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7 other than the PL2 polarized transmitting antenna is Δfd (1、4) =4Δfd,Δfd (4、5) =2Δfd,Δfd (6、7) =Δfd (7、1) =Δfd, the Doppler frequency shift between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7 other than the PL1 polarized transmitting antenna is Δfd (2、3) =Δfd,Δfd (3、5) =Δfd (5、7) =2Δfd,Δfd (7、2) =3Δfd. Therefore, the Doppler shift amounts between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7 other than the PL2 polarized transmitting antenna and the Doppler shift amounts between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7 other than the PL1 polarized transmitting antenna include different Doppler shift intervals.

[0712] For example, 4Δfd is included in the interval of the Doppler frequency shift amount between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7 except the PL2 polarized transmitting antenna, but 4Δfd is not included in the interval of the Doppler frequency shift amount between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7 except the PL1 polarized transmitting antenna.

[0713] In addition, for example, the maximum DDM interval of the Doppler frequency shift amounts between the transmitting antennas Tx#2, Tx#3, Tx#5, and Tx#7 other than the PL1 polarized transmitting antenna is 3Δfd, but 3Δfd is not included in the interval of the Doppler frequency shift amounts between the transmitting antennas Tx#1, Tx#4, Tx#6, and Tx#7 other than the PL2 polarized transmitting antenna.

[0714] therefore, Fig.21 The example shown is an example of setting the pattern of the Doppler shift amount that satisfies condition 2a (1).

[0715] For example, in the case where the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the received signals from the PL1 polarization transmitting antenna (Tx#1, Tx#4, Tx#6) and the PL2 polarization transmitting antenna (Tx#2, Tx#3, Tx#5) at approximately the same level. Here, for the signals transmitted from the Nt transmitting antennas Tx#1 to Tx#7 composed of the PL1 polarization transmitting antenna, the PL2 polarization transmitting antenna and the PL3 polarization transmitting antenna, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, the radar device 10 can demultiplex the Doppler multiplexed signal based on the existing demultiplexing operation of the Doppler multiplexed signal.

[0716] In addition, in the case of a target object reflection wave whose polarization relative to the receiving antenna is cross-polarized, in the case of a target object reflection wave whose PL1 polarization is cross-polarized and in the case of a target object reflection wave whose PL2 polarization is cross-polarized, the radar device 10 receives different Doppler multiplexed signals (for example, a Doppler multiplexed signal that satisfies condition 2a (1)).

[0717] For example, in the case of a reflected wave from a target object having cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal corresponding to the PL1 polarized transmitting antenna decreases and when the reception level of the received signal corresponding to the PL2 polarized transmitting antenna decreases, the radar device 10 receives reflected wave signals containing Doppler frequency components of different modes.

[0718] Therefore, the radar device 10 can, for example, determine in the Doppler multiplexing and demultiplexing unit 211 whether a reduction in the reception level of the reception signal corresponding to the PL1 polarized transmitting antenna or a reduction in the reception level of the reception signal corresponding to the PL2 polarized transmitting antenna has occurred based on the detected Doppler frequency peak value (for example, the interval between the peaks).

[0719] For example, for Doppler multiplexed signals of polarizations other than PL2 polarization, Doppler multiplexing transmission is performed using a Doppler frequency shift interval that is non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to a transmission signal transmitted by a polarization transmission antenna other than the PL2 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0720] Similarly, for example, for Doppler multiplexed signals of polarizations other than PL1 polarization, Doppler multiplexing transmission is performed using the Doppler frequency shift interval that becomes non-uniformly spaced Doppler multiplexing. Therefore, for example, when the Doppler multiplexing demultiplexing unit 211 determines that the received signal is a received signal corresponding to a transmission signal transmitted by a polarization transmission antenna other than the PL1 polarization transmission antenna, the radar device 10 can demultiplex the Doppler multiplexed signal using the existing demultiplexing operation of the Doppler multiplexed signal.

[0721] By operating the Doppler multiplexing and demultiplexing unit 211 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antennas are associated with each Doppler multiplexed signal.

[0722] In the above, an example of setting the Doppler shift amount has been described.

[0723] [Operation Example of Doppler Multiplexing and Demultiplexing Unit 211]

[0724] For example, when a transmission antenna having a polarization other than PL1 polarization and PL2 polarization is used in addition to the two polarizations PL1 polarization and PL2 polarization that are orthogonal to each other, the Doppler multiplexed signal assigned in the Doppler frequency shift unit 104 can be demultiplexed by the following operation of the Doppler multiplexing and demultiplexing unit 211. The operation of the Doppler multiplexing and demultiplexing unit 211 of the third modification example that is different from that of the first embodiment will be described below.

[0725] The Doppler multiplexing and demultiplexing unit 211, for example, in the Doppler frequency shift unit 104, when δ shown in equation (3) is set to a positive integer, calculates the distance index f input from the CFAR unit 210 based on the distance index f b_cfar , 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 )) to perform demultiplexing of Doppler multiplexing. It should be noted that ndm = 1 to N DM +δ integer.

[0726] In Modification 3, Fig.17 The operation of step B and the operation of step C in the demultiplexing operation of the Doppler multiplexer demultiplexer 211 shown are different from those of the first embodiment as described below.

[0727] <Step B-1>

[0728] The Doppler multiplexing and demultiplexing unit 211 assumes that the reflected wave of the target object whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna includes (Nt-N PL2 ) Doppler multiplexed signals of polarizations other than PL2 polarization are demultiplexed.

[0729] <Step B-2>

[0730] In this case, for example, it is assumed that the distance index f input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ), including Nt-N from transmitting antennas other than the transmitting antenna of PL2 polarization PL2 The case of a Doppler multiplexed signal.

[0731] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the 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 to N DM +δ), and determine the Nt-N with the highest receiving power PL2 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval assigned to the transmitting antennas other than the PL2 polarized transmitting antenna during transmission (for example, "Doppler shift interval matching judgment other than the PL2 polarized transmitting antenna").

[0732] In addition, for example, the Doppler multiplexing and demultiplexing unit 211 determines that the Nt-N PL2 The received level of the Doppler frequency index is different from the Nt-N at the front of the received power. PL2 Doppler frequency index (N DM +δ-(Nt-N PL2 )) whether the difference in reception level (or reception level ratio) of other Doppler frequency indices is a large difference (for example, the difference is greater than a threshold, or the reception level ratio is greater than a threshold) (for example, referred to as "Doppler multiplexing signal reception level difference judgment other than PL2 polarization transmitting antenna").

[0733] The Doppler multiplexing and demultiplexing unit 211 determines, for example, the Doppler frequency and the transmission antenna corresponding to the Doppler multiplexed signal within the range of -1 / (2Tr)≦fd<1 / (2Tr) based on these determinations.

[0734] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0735] For example, the Doppler multiplexing and demultiplexing unit 211 determines whether the two conditions (for example, the condition of step B-2) of the Doppler frequency shift interval matching judgment except for the PL2 polarized transmission antenna and the Doppler multiplexing signal reception level difference judgment except for the PL2 polarized transmission antenna are satisfied. It can be that the Doppler multiplexing and demultiplexing unit 211 performs the processing of step B-3 when the condition of step B-2 is satisfied, and performs the processing of step C-1 when the condition of step B-2 is not satisfied, assuming that the target reflection wave including the PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna.

[0736] <Step B-3>

[0737] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with a small receiving level N DM +δ-(Nt-N PL2 ) Doppler frequency indexes with high receiving power are ranked at the front Nt-N PL2 The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex_ PL1 (f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0738] Here, f demul_Tx#n Indicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0739] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0740] Alternatively, the Doppler multiplexing and demultiplexing unit 211 may also multiplex the N t transmitting antennas transmitting the PL1 polarized waves. PL1 The Doppler frequency shift of each Doppler multiplexed signal is matched to the Doppler frequency index, and the PL1 polarization demultiplexing index information of the Doppler multiplexed signal is used as DDM_Rxindex_ PL1 (f b_cfar ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0741] <Step C-1>

[0742] The Doppler multiplexing and demultiplexing unit 211 assumes that the reflected wave of the target object including PL1 is cross-polarized with respect to the polarization of the receiving antenna, and performs Nt-N PL1 Doppler multiplexed signals of polarizations other than PL1 polarization are demultiplexed.

[0743] <Step C-2>

[0744] At this time, for example, it is assumed that the distance index f input from the CFAR unit 210 b_cfar N DM +δ Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ), including Nt-N from transmitting antennas other than the PL1 polarized transmitting antenna PL1 The case of a Doppler multiplexed signal.

[0745] The Doppler multiplexing and demultiplexing unit 211 compares, for example, the 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 to N DM +δ), and determine the Nt-N with the highest receiving power PL1 Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) matches the Doppler shift interval assigned to the transmitting antennas other than the PL1 polarized transmitting antenna during transmission (for example, referred to as "Doppler shift interval matching judgment other than the PL1 polarized transmitting antenna").

[0746] In addition, for example, the Doppler multiplexing and demultiplexing unit 211 determines that the Nt-N PL1 The received level of the Doppler frequency index is different from the Nt-N at the front of the received power. PL1Doppler frequency index (N DM +δ-(Nt-N PL1 )) whether the difference in reception level (or reception level ratio) of other Doppler frequency indices is a large difference (for example, the difference is above a threshold, or the reception level ratio is above a threshold) (for example, referred to as "Doppler multiplexing signal reception level difference judgment other than PL1 polarization transmitting antenna").

[0747] The Doppler multiplexing / demultiplexing unit 211 determines the Doppler frequency and the transmission antenna within the range of -1 / (2Tr)≦fd<1 / (2Tr), for example, based on these determinations.

[0748] Note that, for example, Patent Document 7 discloses an operation example of the Doppler multiplexing and demultiplexing unit 211 that demultiplexes Doppler multiplexed signals with unequal intervals, and therefore a detailed description of the operation is omitted here.

[0749] The Doppler multiplexing and demultiplexing unit 211 determines whether the two conditions (for example, the condition of step C-2) of the Doppler frequency shift interval matching judgment except for the PL1 polarized transmitting antenna and the Doppler multiplexing signal reception level difference judgment except for the PL1 polarized transmitting antenna are satisfied. If the condition of step C-2 is satisfied, the Doppler multiplexing and demultiplexing unit 211 can perform the processing of step C-3. In addition, if the condition of step C-2 is not satisfied, the Doppler multiplexing and demultiplexing unit 211 can determine that the received signal is a noise component or an interference component, and does not output to the direction estimation unit 212 (step D).

[0750] <Step C-3>

[0751] The Doppler multiplexing and demultiplexing unit 211 performs the multiplexing and demultiplexing based on the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) with a small receiving level N DM +δ-(Nt-N PL1 ) Doppler frequency indexes with high receiving power are ranked at the front Nt-N PL1 The Doppler frequency index relationship of the Nt Doppler multiplexed signals is used to calculate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP Nt , corresponds to the Doppler frequency index, and serves as the demultiplexing index information DDM_RXindex_ PL2 (f b_cfar )=(f demul_Tx#1 , ..., f demul_Tx#NDM ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0752] Here, f demul_Tx#nIndicates the Doppler frequency index of the reflected wave signal for the radar transmission signal transmitted from the nth transmission antenna (Tx#n).

[0753] In addition, the Doppler multiplexing and demultiplexing unit 211 outputs the output of the Doppler analysis unit according to the distances and the Doppler demultiplexing index to the direction estimation unit 212, for example.

[0754] Alternatively, the Doppler multiplexing and demultiplexing unit 211 may also multiplex the N t transmitting antennas transmitting the PL2 polarized waves. PL2 The Doppler frequency shift of each Doppler multiplexed signal is matched to the Doppler frequency index, and the PL2 polarization demultiplexing index information of the Doppler multiplexed signal is used as DDM_Rxindex_ PL2 (f b_cfar ), and the distance index f b_cfar The two signals are outputted together to the direction estimation unit 212 .

[0755] In the above, an operation example of the Doppler multiplexing and demultiplexing unit 211 has been described.

[0756] (Implementation Method 2)

[0757] In the first embodiment, the following case is described, that is, in a polarization MIMO radar using Nt transmission antennas including transmission antennas with different polarizations, the radar device 10 uses non-equally spaced Doppler multiplexing transmission, uses all Nt transmission antennas to perform multiplexing transmission simultaneously, and transmits a Doppler multiplexing signal that satisfies at least condition 2 (satisfies "condition 1 and condition 2" or satisfies "condition 2") by means of the Doppler frequency shift unit 104. As a result, in the first embodiment, even when the reflected wave reception levels are greatly different between the transmission polarization antennas, the transmission polarization antenna can be distinguished in the Doppler multiplexing demultiplexing unit 211, and the Doppler multiplexing signal can be demultiplexed, so that the degradation of the detection performance of the polarization MIMO radar using non-equally spaced Doppler multiplexing transmission can be suppressed.

[0758] When the reflected wave reception levels greatly differ between the transmission polarization antennas as described above, the method of distinguishing the transmission polarization antennas and demultiplexing the Doppler multiplexed signal in the Doppler multiplexing / demultiplexing unit 211 is not limited to the method described in the first embodiment.

[0759] In this embodiment, a method of performing unequally spaced Doppler multiplexing transmission among a plurality of transmission antennas of the same polarization by temporally shifting transmission cycles of transmission signals transmitted from transmission antennas of different polarizations will be described.

[0760] For example, in this embodiment, the timing at which a transmission signal is transmitted from a PL1 polarized transmission antenna and the timing at which a transmission signal is transmitted from a PL2 polarized transmission antenna may be different.

[0761] By adopting such a method, since the polarization of the transmission antenna in each transmission cycle is known, the radar device can distinguish the transmission polarization antenna even when the reflected wave reception levels differ greatly between the transmission polarization antennas.

[0762] Therefore, the reflected wave reception levels of multiple transmitting antennas with the same polarization are unlikely to differ greatly, Doppler demultiplexing of unequally spaced Doppler multiplexing transmission can be performed, and degradation of detection performance of polarization MIMO radar using unequally spaced Doppler multiplexing transmission can be suppressed.

[0763] Fig. 22 The configuration diagram of the radar device 100c according to this embodiment is shown below. Fig. 22 An operation example of the radar device 100c is described. Fig. 22 In the embodiment 1 (for example, Figure 5 ) The same structures are marked with the same figure marks. In addition, this embodiment mainly describes the actions that are different from those of embodiment 1.

[0764] For example, in Fig. 22 In the radar device 10b shown, relative to Figure 5 In the radar device 10 shown, a transmission switching control unit 301 and a transmission switching unit 302 are added to the radar transmitting unit 100b, and an output switching unit 401 is added to the radar receiving unit 200b.

[0765] Fig. 22 This is a polarization MIMO radar using Nt transmission antennas, and the Nt transmission antennas of the transmission antenna unit 105 include a PL1 polarization transmission antenna and a PL2 polarization transmission antenna in a mutually orthogonal polarization relationship. Hereinafter, the qth polarization is referred to as "PLq polarization".

[0766] As a combination of different polarizations in a mutually orthogonal polarization relationship, for example, as the polarization of (PL1, PL2), right-hand circular polarization and left-hand circular polarization, horizontal polarization and vertical polarization, right slant 45° polarization and left slant 45° polarization can be used.

[0767] In addition, the transmitting antenna unit 105 includes the number N of PL1 polarized transmitting antennas. PL1 ≧2, Number of PL2 polarized transmitting antennas N PL2 ≧2 transmitting antennas. For example, the number of transmitting antennas N may be t =N PL1 +N PL2 ≧4.

[0768] In the following example, let N PL1 =N PL2, and set the Doppler multiplexing number to N DM =N PL1 =N PL2 , the case where the same Doppler shift amount is assigned to each transmitting antenna in each time-division transmission is described, but the present invention is not limited to this, and the Doppler shift amount assigned to each transmitting antenna may be different according to the time-division transmission.

[0769] In addition, not limited to N PL1 =N PL2 In the case of PL1 ≠N PL2 In N PL1 ≠N PL2 In the case of time division, the Doppler multiplexing number can be changed by sending in time, and the Doppler multiplexing number N in the first sending cycle DM1 Set to N DM1 =N PL1 , the Doppler multiplexing number N in the second transmission cycle DM2 Set to N DM2 =N PL2 .

[0770] In addition, the time division multiplexing number is represented as "N TM For example, when the Nt transmitting antennas include a PL1 polarized transmitting antenna and a PL2 polarized transmitting antenna that are orthogonal to each other, N TM Can be set to N TM =2. For example, the time division multiplexing number N TM It can be set to be equal to the number of polarizations included in the transmitting antenna.

[0771] As an example, the following Doppler multiplexing number N is used: DM and the number of time division multiplexing N TM Here, N DM =N PL1 =N PL2 , the number Nt of transmitting antennas included in the transmitting antenna unit 105 is Nt=N DM ×N TM .

[0772] [Configuration Example of Radar Transmitter 100b]

[0773] The transmission switching control unit 301 generates a time division multiplexing index “TM_INDEX” indicating switching of transmission antennas within the transmission antenna unit 105 for time division multiplexing for each radar transmission cycle (Tr), and outputs the time division multiplexing index TM_INDEX to the transmission switching unit 302 and the output switching unit 401 .

[0774] Here, TM_INDEX = 1, 2, ..., NTM For example, TM_INDEX of the mth transmission cycle = MOD(m-1, N TM )+1. Here, MOD(x, y) is a modulus operator, which is a function that outputs the remainder after dividing x by y.

[0775] For example, when the Doppler multiplexing number is set to N DM hour, Fig. 22 The radar transmitting unit 100b shown in FIG. DM Doppler frequency shift units 104-1 to 104-N DM In addition, the radar transmitter 100b has the same number of N as the Doppler frequency shift unit 104. DM A transmission switching unit 302 is provided.

[0776] Each Doppler frequency shift unit 104 applies a predetermined phase rotation to the chirp signal input from the radar transmission signal generation unit 101. To give a specified Doppler frequency shift DOP ndm , and outputs the chirp signal with phase rotation to the corresponding transmission switching section 302. Here, ndm=1, ..., N DM .

[0777] The ndmth transmission switching unit 302 switches to the {(ndm-1)×Nth transmission switching unit 302 according to the instruction of the time division multiplexing index TM_INDEX. TM +TM_INDEX} transmitting antennas and output the output of the ndm-th Doppler frequency shift unit 104.

[0778] Through the above-mentioned operations of the Doppler frequency shift unit 104 and the transmission switching unit 302, the floor[(n-1) / N TM ]+1 Doppler frequency shift unit 104 gives a Doppler frequency shift DOP to the output of the radar transmission signal generating unit 101 floor[(n-1) / NTM]+1 The signal after floor[(n-1) / N TM ]+1 transmission switching unit 302, when the time division multiplexing index TM_INDEX is mod(n-1, N TM )+1, the nth transmitting antenna among the Nt transmitting antennas of the transmitting antenna unit 105 is output.

[0779] Here, the transmission switching unit 302 outputs the polarization of the transmission antenna in accordance with the time division multiplexing index TM_INDEX. TM=2, the transmission switching unit 302 switches so that, among the Nt transmission antennas of the transmission antenna unit 105, when TM_INDEX=1, the transmission signal is output from the PL1 polarized transmission antenna, and when TM_INDEX=2, the transmission signal is output from the PL2 polarized transmission antenna.

[0780] Therefore, in the operation of the transmission switching unit 302, TM When =2, it can be that among the Nt transmitting antennas, when n represents the transmitting antenna (for example, Tx#n), the transmitting antenna with odd n represents the PL1 polarization transmitting antenna, and the transmitting antenna with even n represents the PL2 polarization transmitting antenna.

[0781] For example, let Nt = 6 transmitting antennas and Doppler multiplexing number N DM =3, time division multiplexing number N TM =2. In this case, N DM =N PL1 =N PL2 =3, including three PL1 polarization transmitting antennas and three PL2 polarization transmitting antennas. In addition, 3(=N DM ) Doppler frequency shift units 104 give Doppler frequency shift amounts DOP1, DOP2, and DOP3 to the chirp signal, respectively. DM ) The time division multiplexing index TM_INDEX of each transmission switching unit 302 is 2(=N TM ) elements.

[0782] In this case, for example, the first transmission antenna (Tx#1) is a PL1 polarization transmission antenna, and outputs the following signal at the transmission period Tr.

[0783] [Formula 25]

[0784] Λ1(1)cp(t),0,Λ1(2)cp(t),0,Λ1(3)cp(t),0,...(25)

[0785] Here, cp(t) represents the chirp signal of each transmission period Tr. In addition, the phase rotation is given to the Doppler frequency shift unit 104. The multiplication value is expressed as Λ shown in the following formula (26): ndm (m), can be set to zero when no signal is sent.

[0786] [Equation 26]

[0787] Λ ndm (m) = exp[jφ ndm (m)] (26)

[0788] Similarly, for example, the second transmitting antenna (Tx#2) is a PL2 polarized transmitting antenna, and outputs the following signal at the transmission period Tr.

[0789] [Formula 27]

[0790] 0,Λ1(1)cp(t),0,Λ1(2)cp(t),0,Λ1(3)cp(t),...(27)

[0791] Similarly, for example, the third transmitting antenna (Tx#3) is a PL1 polarized transmitting antenna, and outputs the following signal at the transmission period Tr.

[0792] [Equation 28]

[0793] Λ2(1)cp(t),0,Λ2(2)cp(t),0,Λ2(3)cp(t),0,...(28)

[0794] Similarly, for example, the fourth transmitting antenna (Tx#4) is a PL2 polarized transmitting antenna, and outputs the following signal at the transmission period Tr.

[0795] [Formula 29]

[0796] 0,Λ2(1)cp(t),0,Λ2(2)cp(t),0,Λ2(3)cp(t),...(29)

[0797] Similarly, for example, the fifth transmission antenna (Tx#5) is a PL1 polarization transmission antenna, and outputs the following signal at the transmission period Tr.

[0798] [Formula 30]

[0799] Λ3(1)cp(t),0,Λ3(2)cp(t),0,Λ3(3)cp(t),0,...(30)

[0800] Similarly, for example, the sixth transmission antenna (Tx#6) is a PL2 polarization transmission antenna, and outputs the following signal at the transmission period Tr.

[0801] [Equation 31]

[0802] 0,Λ3(1)cp(t),0,Λ3(2)cp(t),0,Λ3(3)cp(t),...(31)

[0803] In addition, the radar transmitter 100b transmits chirped pulses N times. TM The signal is sent in the form of an integer multiple (Ncode times). C =N TM ×Ncode.

[0804] [Configuration Example of Radar Receiver 200b]

[0805] Next, Fig. 22 The configuration example of the radar receiving unit 200b shown in FIG.

[0806] In the z-th signal processing unit 206b, the output switching unit 401 selectively switches to N based on the time division multiplexing index TM_INDEX input from the transmission switching control unit 301. TM Doppler analysis units 209-1~209-N TM The output switching unit 401 selects the TM_INDEX-th Doppler analysis unit 209 in the m-th transmission cycle Tr and outputs the output of the beat frequency analysis unit 208 in each transmission cycle Tr. For example, in the m-th transmission cycle Tr, the output switching unit 401 selects the TM_INDEX-th Doppler analysis unit 209.

[0807] The z-th signal processing unit 206b has N TM A Doppler analysis unit 209 is provided.

[0808] By the operation of the output switching unit 401, the ntm-th Doppler analysis unit 209 in the z-th signal processing unit 206b performs the following operations every N TM The sending cycle (N TM Therefore, the ntm-th Doppler analysis unit 209 uses N C Doppler analysis is performed on the data of Ncode transmission cycles in Ncode transmission cycles. Here, ntm = 1, ..., N TM .

[0809] In addition, when Ncode is a power of 2, the Doppler analysis unit 209 can apply FFT (Fast Fourier Transform) processing represented by the following equation (32).

[0810] [Formula 32]

[0811]

[0812] Here, the FFT size is Ncode, and the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1 / (2N TM ×Tr). In addition, the Doppler frequency index f s The Doppler frequency interval is 1(Ncode×N TM ×Tr), Doppler frequency index f s The range is f s =-Ncode / 2,...,0,...,Ncode / 2-1.

[0813] In addition, when Ncode is not a power of 2, for example, by including zero-filled data, FFT processing can be performed as an FFT size that is a power of 2. In addition, when performing FFT processing, window function coefficients such a...

Claims

1. A radar device, characterized in that: have: A plurality of transmitting antennas, including a first transmitting antenna radiating a first polarized wave and a second transmitting antenna radiating a second polarized wave different from the first polarized wave; as well as a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmitting antennas are applied, respectively; The Doppler multiplexing intervals of the plurality of transmitting antennas are unequally spaced on the Doppler frequency axis, A first pattern of Doppler frequency shift amounts assigned to the first transmission antenna is different from a second pattern of Doppler frequency shift amounts assigned to the second transmission antenna.

2. The radar device according to claim 1, wherein: The first mode and the second mode are related to the Doppler multiplexing interval, At least one of the Doppler multiplexing intervals based on the first transmit antenna is different from the Doppler multiplexing interval based on the second transmit antenna.

3. The radar device according to claim 1, wherein: The first mode and the second mode are related to the number of transmitting antennas. The number of the first transmitting antennas is different from the number of the second transmitting antennas.

4. The radar device according to claim 1, wherein: The first mode and the second mode are related to the Doppler multiplexing number. A Doppler multiplexing number using the first polarized wave is different from a Doppler multiplexing number using the second polarized wave.

5. The radar device according to claim 1, wherein: The first mode and the second mode are related to the order of the intervals of the Doppler frequency shift amounts. A plurality of first Doppler multiplexing intervals based on the first transmitting antenna are the same as a plurality of Doppler multiplexing intervals based on the second transmitting antenna, An order of the plurality of Doppler multiplexing intervals based on the first transmitting antenna on the Doppler frequency axis is different from an order of the plurality of Doppler multiplexing intervals based on the second transmitting antenna on the Doppler frequency axis.

6. The radar device according to claim 1, wherein: On the Doppler frequency axis, the Doppler multiplexing intervals based on the first transmitting antenna are unequally spaced.

7. The radar device according to claim 1, wherein: On the Doppler frequency axis, the Doppler multiplexing intervals based on the second transmitting antenna are unequally spaced.

8. The radar device according to claim 1, wherein: Also available: a receiving antenna, using one of the first polarized wave and the second polarized wave to receive a reflected wave signal of the transmitted signal reflected from the target object; as well as The direction estimation circuit estimates the direction according to the reflected wave signal.

9. The radar device according to claim 1, wherein: Also available: 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, receiving a reflected wave signal of the transmitted signal reflected from a target object; as well as The direction estimation circuit estimates the directions of the reflected wave signals received by the first receiving antenna and the second receiving antenna respectively.

10. A radar device, characterized in that: have: A plurality of transmitting antennas, including a first transmitting antenna radiating a first polarized wave and a second transmitting antenna radiating a second polarized wave different from the first polarized wave; as well as a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmitting antennas are applied, respectively; A timing at which the transmission signal is transmitted from the first transmission antenna is different from a timing at which the transmission signal is transmitted from the second transmission antenna.

11. The radar device according to claim 10, wherein: The Doppler multiplexing intervals based on the first transmitting antenna are unequally spaced on the Doppler frequency axis, and the Doppler multiplexing intervals based on the second transmitting antenna are unequally spaced on the Doppler frequency axis.

12. The radar device according to claim 10, wherein: The Doppler frequency shift amount allocated to the first transmission antenna includes the same Doppler frequency shift amount as the Doppler frequency shift amount allocated to the second transmission antenna.

13. The radar device according to claim 10, wherein: A third pattern of the Doppler frequency shift amount assigned to the first transmission antenna is different from a fourth pattern of the Doppler frequency shift amount assigned to the second transmission antenna.

14. A radar device, characterized in that: have: A plurality of transmitting antennas, including a first transmitting antenna radiating a first polarized wave, a second transmitting antenna radiating a second polarized wave different from the first polarized wave, and a third transmitting antenna having a polarization different from that of the first transmitting antenna and the second transmitting antenna; as well as a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which phase rotations corresponding to the Doppler shift amounts assigned to the plurality of transmitting antennas are applied, respectively; The Doppler multiplexing intervals of the plurality of transmitting antennas are unequally spaced on the Doppler frequency axis, On the Doppler frequency axis, a fifth pattern related to the Doppler frequency shift amounts assigned to the first and third transmitting antennas is different from a sixth pattern related to the Doppler frequency shift amounts assigned to the second and third transmitting antennas.

15. The radar device according to claim 14, wherein: The fifth mode and the sixth mode are related to the Doppler multiplexing interval, At least one of the Doppler multiplexing intervals based on the second transmission antenna and the third transmission antenna is different from the Doppler multiplexing intervals based on the first transmission antenna and the third transmission antenna.

16. The radar apparatus according to claim 14, wherein: The fifth mode and the sixth mode are related to the order of the intervals of the Doppler frequency shift amounts, A plurality of Doppler multiplexing intervals based on the second transmitting antenna and the third transmitting antenna are the same as a plurality of Doppler multiplexing intervals based on the first transmitting antenna and the third transmitting antenna, An order of the Doppler multiplexing intervals based on the second transmitting antenna and the third transmitting antenna on the Doppler frequency axis is different from an order of the Doppler multiplexing intervals based on the first transmitting antenna and the third transmitting antenna on the Doppler frequency axis.

17. The radar apparatus according to claim 14, wherein: On the Doppler frequency axis, the Doppler multiplexing intervals based on the second transmitting antenna and the third transmitting antenna are unequally spaced.

18. The radar apparatus according to claim 14, wherein: On the Doppler frequency axis, the Doppler multiplexing intervals based on the first transmitting antenna and the third transmitting antenna are unequally spaced.

Images