Radar device, radar signal generation device, and radar signal generation method

Abstract

To improve the detection accuracy of targets in a radar device.SOLUTION: A radar device includes a plurality of transmitting antennas including a first transmitting antenna forming a first beam and a second transmitting antenna forming a second beam different from the first beam, and a transmitting circuit that multiplexes and transmits from the plurality of transmitting antennas a transmission signal to which a phase rotation corresponding to an amount of Doppler shift assigned to each of the plurality of transmitting antennas is given. Doppler shift intervals by the plurality of transmitting antennas are unequally spaced on a Doppler frequency axis, and a first pattern of the amount of Doppler shift assigned to the first transmitting antenna is different from a second pattern of the amount of Doppler shift assigned to the second transmitting antenna.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This disclosure relates to radar equipment. [Background technology]

[0002] In recent years, research has been progressing on radar systems that use short-wavelength radar transmission signals, including microwaves or millimeter waves, which can achieve high resolution. Furthermore, in order to improve safety outdoors, there is a need for the development of radar systems (for example, called wide-angle radar systems) that can detect small objects such as pedestrians in addition to vehicles over a wide-angle range.

[0003] One configuration for radar systems with a wide detection range is to use an array antenna, which consists of multiple antennas (also called antenna elements), to receive reflected waves from a target and to estimate the direction of arrival of the reflected waves from the target (also called the angle of arrival) based on the received phase difference with respect to the element spacing (antenna spacing). For example, examples of angle of arrival estimation methods include the Fourier method, 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).

[0004] Furthermore, a radar system has been proposed that, for example, includes multiple antennas (array antennas) in both the receiving and transmitting sections, and performs beam scanning by signal processing using the transmitting and receiving array antennas (sometimes called MIMO (Multiple Input Multiple Output) radar) (see, for example, Non-Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-211388 [Patent Document 2] U.S. Patent Application Publication No. 2022 / 0066012 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-304417 [Patent Document 4] Japanese Patent Application Publication No. 2011-526371 [Patent Document 5] Japanese Patent Application Laid-Open No. 2014-119344 [Patent Document 6] Japanese Patent Application Laid-Open No. 2019-052952 [Patent Document 7] Japanese Patent Application Laid-Open No. 2020-148754 [Non-Patent Document]

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

[0007] However, methods for detecting targets in radar systems (e.g., MIMO radar) have not been sufficiently studied.

[0008] Non-limiting embodiments of this disclosure contribute to providing radar devices that improve the accuracy of target detection. [Means for solving the problem]

[0009] A radar system according to one embodiment of the present disclosure comprises a plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam different from the first beam, and a transmitting circuit that multiplexes a transmission signal from the plurality of transmitting antennas, to which a phase rotation corresponding to a Doppler shift amount assigned to each of the plurality of transmitting antennas is applied, wherein the Doppler shift intervals of the plurality of transmitting antennas are unequal on the Doppler frequency axis, and a first pattern of Doppler shift amounts assigned to the first transmitting antenna and a second pattern of Doppler shift amounts assigned to the second transmitting antenna are different.

[0010] These comprehensive or specific embodiments may be implemented as systems, devices, methods, integrated circuits, computer programs, or recording media, or as any combination of systems, devices, methods, integrated circuits, computer programs, and recording media. [Effects of the Invention]

[0011] According to one embodiment of the present disclosure, the accuracy of target detection in a radar system can be improved.

[0012] Further advantages and effects in an embodiment of the present disclosure will be clarified from the specification and the drawings. Such advantages and / or effects are respectively provided by several embodiments and the features described in the specification and the drawings, but not all of them are necessarily provided in order to obtain one or more identical features.

Brief Description of the Drawings

[0013] [Figure 1] Figure showing an example of time division multiplexing (TDM) transmission [Figure 2] Figure showing an example of Doppler division multiplexing (DDM) transmission [Figure 3] Figure showing an example of non-uniform Doppler division multiplexing transmission [Figure 4] Figure showing an example of a multi-beam transmission MIMO radar [Figure 5] Figure showing an example of Doppler division multiplexing transmission in a multi-beam transmission MIMO radar [Figure 6] Figure showing an example of Doppler division multiplexing transmission in a multi-beam transmission MIMO radar [Figure 7] Block diagram showing a configuration example of a radar device [Figure 8] Figure showing an example of a transmission signal when using a chirp signal [Figure 9] Figure showing an example of a chirp signal [Figure 10] Figure showing an example of a transmission signal and a reception signal when using a chirp signal [Figure 11] Figure showing an example of a Doppler shift amount setting [Figure 12] Figure showing an example of a reception signal in Doppler division multiplexing transmission [Figure 13] Figure showing an example of a multi-beam transmission MIMO radar [[ID=FF]] [Figure 14] Figure showing an example of a Doppler shift amount setting [Figure 15] Figure showing an example of a reception signal in Doppler division multiplexing transmission [Figure 16] A diagram showing an example of setting the Doppler shift amount. [Figure 17] A diagram showing an example of setting the Doppler shift amount. [Figure 18] A flowchart illustrating an example of Doppler multiplexing signal separation. [Figure 19] Diagram showing an example of a transmitting antenna configuration. [Figure 20] A diagram showing an example of a multibeam transmitting MIMO radar. [Figure 21] A diagram showing an example of MIMO antenna configuration and virtual receiving antenna configuration. [Figure 22] A diagram showing an example of MIMO antenna configuration and virtual receiving antenna configuration. [Figure 23] A diagram showing an example of MIMO antenna configuration and virtual receiving antenna configuration. [Figure 24] A diagram showing an example of a multibeam transmitting MIMO radar. [Figure 25] A diagram showing an example of MIMO antenna configuration. [Figure 26] A diagram showing an example of setting the Doppler shift amount. [Figure 27] A diagram showing an example of setting the Doppler shift amount. [Figure 28] A diagram showing an example of setting the Doppler shift amount. [Figure 29] A diagram showing an example of a multibeam transmitting MIMO radar. [Figure 30] A diagram showing an example of a multibeam transmitting MIMO radar. [Figure 31] A diagram showing an example of a multibeam transmitting MIMO radar. [Figure 32] A diagram showing an example of a multibeam transmitting MIMO radar. [Figure 33] A diagram showing an example of a multibeam transmitting MIMO radar. [Modes for carrying out the invention]

[0014] MIMO radar transmits multiplexed signals (radar transmission waves) using, for example, time-division, frequency-division, or code-division multiplexing from multiple transmitting antennas (or transmitting array antennas), and receives the signals reflected from surrounding objects (radar reflection waves) using multiple receiving antennas (or receiving array antennas). The multiplexed transmission signals are then separated and received from each received signal. Through this process, MIMO radar can obtain a propagation path response represented by the product of the number of transmitting antennas and the number of receiving antennas, and these received signals are processed as a virtual receiving array for array signal processing. Furthermore, in MIMO radar, the angular resolution can be improved by appropriately arranging the element spacing in the transmitting and receiving array antennas to enlarge the antenna aperture of the virtual receiving array.

[0015] [About multibeam radar] The directional characteristics (or simply referred to as "directivity") of the multiple transmitting or receiving antennas that make up a MIMO radar are preferably equivalent in order to improve angular measurement performance, such as angular measurement accuracy or angular resolution. On the other hand, since the directional characteristics of the transmitting or receiving antennas are set according to the detection distance or detection angle range required by the radar, it may be difficult to cover the required specifications if there is only one type of directional characteristic for the transmitting or receiving antennas.

[0016] For example, in order to satisfy a wide detection angle range while also meeting the required detection distance, it may be necessary to use multiple transmitting or receiving antennas with different directional characteristics in the main beam direction (hereinafter sometimes referred to as "beam direction," "transmitting beam direction," or "receiving beam direction").

[0017] Furthermore, for example, if the required detection distance differs significantly for each detection angle direction, it may be necessary to use multiple transmitting or receiving antennas with different directional characteristics, each having at least one different beam direction and beam width suitable for each angle direction.

[0018] Also, for example, when the detection angle ranges vary significantly for each of a plurality of detection distances (e.g., for each of a long-distance range, a medium-distance range, and a short-distance range), there may be cases where transmission antennas or reception antennas with multiple directivity characteristics having substantially the same beam direction but different beam widths (e.g., 3 dB beam width or 6 dB beam width) according to the detection distance are used.

[0019] For example, when the number of transmission antennas or reception antennas is limited due to restrictions on the size or cost of a radar device, using transmission antennas or reception antennas with different directivity characteristics becomes an effective means to meet the requirements.

[0020] In such cases, it is expected to configure a MIMO radar using a plurality of transmission antennas or reception antennas with different directivity characteristics.

[0021] Examples of the multiple different directivity characteristics of the transmission antenna or reception antenna include directivity characteristics with the same beam width but different beam directions, directivity characteristics with both different beam directions and beam widths, or directivity characteristics with the same beam direction but different beam widths.

[0022] Hereinafter, a MIMO radar that uses a plurality of transmission antennas (e.g., transmission antennas that form different beams) having different directivity characteristics as described above is referred to as a "multi-beam transmission MIMO radar". Here, the multi-beam transmission MIMO radar includes a plurality of transmission antennas having different directivity characteristics. Note that the multi-beam transmission MIMO radar may also have a configuration including one or more transmission antennas with the same directivity.

[0023] Also, hereinafter, a MIMO radar that uses a plurality of reception antennas (e.g., reception antennas that form different beams) having different directivity characteristics as described above is referred to as a "multi-beam reception MIMO radar". Here, the multi-beam reception MIMO radar includes a plurality of reception antennas having different directivity characteristics. Note that the multi-beam reception MIMO radar may also have a configuration including one or more reception antennas with the same directivity.

[0024] Similarly, in the following, a MIMO radar that uses multiple transmitting and receiving antennas with different directional characteristics as described above will be referred to as a "multibeam transceiver-MIMO radar" (or multibeam MIMO radar).

[0025] For example, Patent Document 1 discloses a 3-transmitter MIMO radar configuration that switches between two transmitting antennas with a certain directionality and one transmitting antenna with a different directionality in a time-division manner. Patent Document 1 also discloses a configuration that switches between a time period for code multiplexing transmission using two transmitting antennas with a certain directionality and a time period for code multiplexing transmission using two transmitting antennas with a different directionality.

[0026] Furthermore, for example, Patent Document 2 discloses a MIMO radar configuration that switches between a directional transmitting antenna for long distances and a directional transmitting antenna for medium to short distances using a combination of time-division multiplexing and Doppler multiplexing.

[0027] The following focuses on a multiplexing method in a multibeam MIMO radar that uses multiple transmitting antennas with different directional characteristics (for example, multiple transmitting antennas that form different beams).

[0028] [Regarding time-division multiplexing] For example, one method of multiplexing transmission in MIMO radar using multiple transmitting antennas is time division multiplexing (TDM), which shifts the transmission time for each transmitting antenna to transmit signals. Compared to frequency division multiplexing (FDM) and code division multiplexing (CDM), time division multiplexing can be implemented with a simpler configuration, and by sufficiently widening the transmission time interval, it is possible to maintain good orthogonality between transmitted signals.

[0029] For example, the MIMO radar using time-division multiplexing disclosed in Patent Document 3 outputs a transmission pulse, which is an example of a transmission signal, while sequentially switching the transmitting antenna that transmits the transmission signal (e.g., a transmission pulse or radar transmission wave) at a predetermined period. The MIMO radar using time-division multiplexing receives the signal reflected by the transmission pulse from an object with multiple receiving antennas, and after correlation processing of the received signal and the transmission pulse, it performs, for example, spatial FFT (Fast Fourier Transform) processing (processing to estimate the direction of arrival of the reflected wave).

[0030] In MIMO radar using time-division multiplexing, a predetermined transmission time (or transmission interval) is allocated to each of the multiple transmitting antennas. Therefore, a multi-beam MIMO radar using time-division multiplexing receives reflections from a target at each allocated transmission time using multiple transmitting antennas with different beam direction directivity, thereby separating and receiving the reflected waves from the target corresponding to the transmitted signals of each transmitting antenna with different beam directions.

[0031] MIMO radars using time-division multiplexing sequentially switch the transmitting antennas that transmit radar waves at predetermined intervals. Therefore, the time required for transmission from all transmitting antennas to be completed tends to be longer compared to cases using frequency-division multiplexing or code-division multiplexing. Consequently, in MIMO radars using time-division multiplexing, when multiple radar waves are transmitted from each transmitting antenna and Doppler frequency detection (e.g., relative velocity detection) is performed from the received phase changes (for example, Figure 4 of Patent Document 4), the time interval for observing the received phase changes when applying Fourier frequency analysis for Doppler frequency detection (e.g., relative velocity detection) becomes longer. When the time interval for observing the received phase changes when applying Fourier frequency analysis becomes longer, the maximum detectable Doppler frequency based on the sampling theorem tends to decrease, and the detectable Doppler frequency range (e.g., relative velocity range) tends to narrow.

[0032] For example, as shown in Figure 1, we will describe a MIMO radar that uses time-division multiplexing, which outputs a transmission pulse while sequentially switching between transmitting antennas (e.g., Tx#1 and Tx#2) that send out a chirp signal as a transmitted radar wave, with a transmission period Tr.

[0033] For example, in the case of Nt transmitting antennas (Nt=2 in Figure 1), the transmission time until the transmission of radar waves from Nt transmitting antennas is completed is Tr × Nt (2Tr in Figure 1). In a MIMO radar using time-division multiplexing, if such time-division multiplexing is repeated Nc times and Fourier frequency analysis is applied for Doppler frequency detection (e.g., relative velocity detection), the Doppler frequency range in which the Doppler frequency can be detected without aliasing is ±1 / (2Tr × Nt) according to the sampling theorem. Therefore, the Doppler frequency range in which the Doppler frequency can be detected without aliasing becomes narrower as the number of transmitting antennas Nt increases. Furthermore, in a MIMO radar using time-division multiplexing, when receiving a Doppler frequency that exceeds the range in which the Doppler frequency can be detected without aliasing, it is difficult to uniquely determine the Doppler frequency (e.g., relative velocity), and ambiguity is likely to occur.

[0034] For example, in a multi-beam MIMO radar using time-division multiplexing, as described in Patent Document 1, similar to the MIMO radar using time-division multiplexing described above, the Doppler frequency range in which Doppler frequencies can be detected without aliasing tends to narrow as the number of transmitting antennas Nt increases.

[0035] The above explains an example of time-division multiplexing transmission.

[0036] Next, as an example, let's consider a method of simultaneously multiplexing and transmitting signals from multiple transmitting antennas.

[0037] [About Doppler multiplexing] One method for simultaneously multiplexing and transmitting signals from multiple transmitting antennas is to transmit signals in such a way that the receiving unit can separate multiple transmission signals in the Doppler frequency range (hereinafter referred to as "Doppler Division Multiplexing (DDM) transmission") (see, for example, Patent Document 5).

[0038] In Doppler multiplexing, the transmitting section applies a phase rotation to each transmitting antenna, for example, which gives a different Doppler shift amount to the transmitted signal, and transmits signals simultaneously from multiple transmitting antennas. In Doppler multiplexing, the signals received using multiple receiving antennas (reflected waves from targets) are filtered in the Doppler frequency domain, so that the transmitted signals from each transmitting antenna are separated and received.

[0039] In MIMO radar using Doppler multiplexing, for example, a predetermined Doppler frequency range (or Doppler shift amount) is assigned to each of the multiple transmitting antennas. For example, a multi-beam MIMO radar using Doppler multiplexing receives reflections from a target for each Doppler frequency range assigned to multiple transmitting antennas with different beam directions, thereby separating and receiving the reflected waves from the target that correspond to the transmitted signals of each transmitting antenna with different beam directions.

[0040] In MIMO radar using Doppler multiplexing, the time interval for observing the received phase change when applying Fourier frequency analysis for Doppler frequency detection (e.g., relative velocity detection) can be shortened compared to time-division multiplexing by simultaneously transmitting signals from multiple transmitting antennas. On the other hand, in MIMO radar using Doppler multiplexing, the effective Doppler frequency bandwidth per transmitted signal is limited because the transmitted signals from each transmitting antenna are separated by filtering on the Doppler frequency axis.

[0041] For example, as shown in Figure 2(a), we will describe a MIMO radar that uses Doppler multiplexing, which involves repeatedly transmitting a chirp signal with a transmission period Tr as the transmitted radar wave Nc times, and then applying Fourier frequency analysis for Doppler frequency detection (e.g., relative velocity detection).

[0042] For example, in Figure 2(b), the Doppler frequency range in which the Doppler frequency can be detected without aliasing on the Doppler frequency axis is ±1 / (2Tr) by the sampling theorem, which is Nt times (Nt=2 in the case of Figure 2) larger than when time-division multiplexing is performed. On the other hand, in MIMO radar using Doppler multiplexing, the transmitted signals are separated by filtering on the Doppler frequency axis, so the effective Doppler frequency range per transmitted signal is narrower than the Doppler frequency range ±1 / (2Tr). For example, if Doppler shifts of 0 [Hz] and -1 / (2Tr) [Hz], which divide the Doppler frequency range ±1 / (2Tr) into Nt (Nt=2 in the case of Figure 2) equal parts, are applied to Tx#1 and Tx#2 respectively, then a MIMO radar using Doppler multiplexing multiplies the transmitted chirp signal (cp(t)) by a phase rotation Φ1(n)=(n-1)ΔΦ1 and Φ2(n)=(n-1)ΔΦ2 (where ΔΦ1=0 and ΔΦ2=π) for each transmission period Tr. Here, n=1,2,3,4,... and is an index representing the number of times the chirp signal has been transmitted.

[0043] In this case, as shown in Figure 2(b), a Doppler frequency domain is pre-assigned to each of the multiple transmitting antennas Tx#1 and Tx#2. For example, the domain of Doppler frequency fd1 of Tx#1 (also called the "Doppler division domain") is assigned -1 / (4Tr)≦fd1<1 / (4Tr), and the domain of Doppler frequency fd2 of Tx#2 is assigned -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<1 / (2Tr).

[0044] MIMO radar using Doppler multiplexing receives, for example, the signals reflected from the target by each transmitting antenna and filters them on the Doppler frequency axis to separate and receive the transmitted signals. For example, in Figure 2(b), MIMO radar using Doppler multiplexing receives the signal reflected from the target by transmitting antenna Tx#1 by filtering the range -1 / (4Tr)≦fd1<1 / (4Tr) on the Doppler frequency axis. Similarly, MIMO radar using Doppler multiplexing receives the signal reflected from the target by transmitting antenna Tx#2 by filtering the range -1 / (2Tr)≦fd2<-1 / (4Tr) and 1 / (4Tr)≦fd2<1 / (2Tr) on the Doppler frequency axis.

[0045] Thus, in MIMO radar using Doppler multiplexing, the reflected signal corresponding to the transmitted signal from each transmitting antenna is received and processed assuming that it falls within a Doppler frequency range of ±1 / (2Tr × Nt), resulting in the same Doppler frequency range as in time-division multiplexing. For example, in MIMO radar using Doppler multiplexing, the Doppler frequency range in which the Doppler frequency can be detected without aliasing tends to narrow as the number of transmitting antennas Nt increases.

[0046] Furthermore, in multi-beam MIMO radars using Doppler multiplexing, similar to the MIMO radars using Doppler multiplexing described above, the Doppler frequency range in which Doppler frequencies can be detected without aliasing tends to narrow as the number of transmitting antennas Nt increases.

[0047] [Regarding unequal-interval Doppler multiplexing] The time-division multiplexing (TDS) or Doppler multiplexing (DDS) methods described above can separate reflected waves corresponding to transmitted signals from multiple transmitting antennas using an allocated transmission time or Doppler frequency domain. On the other hand, in both time-division multiplexing and DDS, the detection range of the Doppler frequency tends to narrow as the number of transmitting antennas increases. For example, in both time-division multiplexing and DDS, the detectable Doppler frequency range is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr), meaning the detection range of the Doppler frequency narrows inversely proportional to the number of transmitting antennas. Here, Nt is the number of transmitting antennas.

[0048] For example, Patent Document 6 discloses a method for expanding the detection range of Doppler frequencies in Doppler multiplexing. Patent Document 6 (for example, Figure 8) discloses the following method: For example, a Doppler frequency range ±1 / (2Tr) in which the Doppler frequency can be detected without aliasing is divided into (Nt+1) equal Doppler shift amounts (or Doppler frequency regions), and Nt Doppler shift amounts are assigned to Nt transmission signals, and transmission signals are transmitted simultaneously from Nt transmitting antennas.

[0049] In this type of Doppler multiplexing, a portion of the Doppler shift amount, which is divided equally into (Nt+1) parts, is not allocated to the transmitted signal. Therefore, in the Doppler frequency domain, the intervals of the Doppler shift amounts assigned to the Doppler-multiplexed transmitted signal (hereinafter also referred to as "Doppler multiplexing intervals" or "Doppler shift intervals") are unequal. Hereafter, this type of Doppler multiplexing will be referred to as "unequal-interval Doppler multiplexing (unequal-interval DDM transmission)".

[0050] Figure 3 shows an example of Doppler multiplexing signal allocation using unequal-interval Doppler multiplexing transmission when a radar transmission wave (e.g., a chirp signal) is transmitted at each transmission period Tr, using a transmitting antenna with Nt=2 and a Doppler shift interval of Δfd=1 / (3Tr).

[0051] In Figure 3, the transmit Doppler shift amounts assigned to transmitting antennas Tx#1 and Tx#2 are Δfd1=0 and Δfd2=1 / (3Tr)[Hz], respectively. For example, to assign a transmit Doppler shift amount Δfd1 to transmitting antenna Tx#1 every n transmission cycles, a phase rotation Φ1(n)=ΔΦ1×(n-1) is assigned to the radar transmit wave (chirp signal). Similarly, for example, to assign a transmit Doppler shift amount Δfd2 to transmitting antenna Tx#2 every n transmission cycles, a phase rotation Φ2(n)=ΔΦ2×(n-1) is assigned to the radar transmit wave (chirp signal). Note that there is no assignment of a transmitting antenna for the Doppler shift amount Δfd3 corresponding to the phase rotation Φ3(n)=ΔΦ3×(n-1).

[0052] Here, Figure 3 shows the transmit Doppler frequencies assigned to transmitting antennas Tx#1 and Tx#2 when Δfd1=0, Δfd2=1 / (3Tr), ΔΦ1=0, and ΔΦ2=2π×Δfd×Tr=2π / 3. In Figure 3, the transmit Doppler frequency when Δfd3=2 / (3Tr) and ΔΦ3=2π×2Δfd×Tr=4π / 3 (or -2π / 3) is indicated by the "×" mark. As shown in Figure 3, there is no assignment of transmitting antennas to the Doppler shift amount Δfd3.

[0053] Note that the phase rotation Φ n is -π≦ΔΦ n It may also be written as <π. For example, it may be written as ΔΦ3 = -2π / 3. The same applies hereafter.

[0054] For example, as shown in Figure 3, the Doppler shift interval for Tx#1 and Tx#2 is Δfd = 1 / (3Tr), and the observable Doppler frequency range (domain) is -1 / (2Tr) ≤ fd < 1 / (2Tr), and we consider the case where Doppler frequencies outside this range are included. For example, if the received Doppler frequency of the Doppler multiplexed signal of Tx#1 or Tx#2 exceeds 1 / (2Tr) or is less than -1 / (2Tr), then, as shown in Figure 3, the Doppler shift interval for Tx#1 and Tx#2 is Δf alias=1 / Tr - Δfd = 2 / 3Tr. In the following, when referring to the "Doppler multiplexing interval" or "Doppler shift interval", in addition to Δfd, Δf alias is included.

[0055] Next, an example of the separation reception process of the Doppler multiplexing signal when using unequal interval Doppler multiplexing transmission will be described.

[0056] In the separation reception process of the Doppler multiplexing signal when using unequal interval Doppler multiplexing transmission, for example, for the Doppler frequency detection (e.g., relative velocity detection) of the received signal of the radar reflected wave, the following property is utilized.

[0057] For example, in the output to which Fourier frequency analysis is applied, among the Doppler shift amounts equally divided into Nt + 1, the received power level of the Doppler frequency corresponding to the Doppler shift amount to which the transmission signal is not assigned is sufficiently lower than the received power level of the Doppler frequency corresponding to the Doppler shift amount to which the transmission signal is assigned (e.g., sufficiently low to the noise level).

[0058] The MIMO radar using unequal interval Doppler multiplexing transmission utilizes this property to estimate the received Doppler frequency of the reflected wave from the target and perform the separation process of the transmission antennas.

[0059] For example, let the received Doppler frequency of the reflected wave from the target be "fd target ". In this case, for the radar reflected wave received signal, in the output to which Fourier frequency analysis is applied for Doppler frequency detection (e.g., relative velocity detection), the received levels of the Doppler frequencies of fd target +Δfd1 and fd target +Δfd2 are observed to be high (e.g., above the threshold). On the other hand, in the output to which Fourier frequency analysis is applied for Doppler frequency detection (e.g., relative velocity detection), the received level of the Doppler frequency of fd target +Δfd3 is lower than that of fd target +Δfd1 and fd targetCompared to the received level at the Doppler frequency where +Δfd2 occurs, it is observed to be sufficiently low, about the level of noise.

[0060] Furthermore, the output obtained by applying Fourier frequency analysis for Doppler frequency detection (e.g., relative velocity detection) is observed in the range -1 / (2Tr) ≤ fd < 1 / (2Tr). If this range is exceeded, the output obtained by applying Fourier frequency analysis is observed as a signal folded back in the range -1 / (2Tr) ≤ fd < 1 / (2Tr).

[0061] Received Doppler frequency fd of reflected wave from target target However, -1 / (2Tr)≦fd target Within the range < 1 / (2Tr), the received Doppler frequency that satisfies the above relationship is -1 / (2Tr) ≤ fd target Since it is unique within the range < 1 / (2Tr), MIMO radar using unequal-spacing Doppler multiplexing transmits the target's Doppler frequency fd without ambiguity within this range. target This can be determined. MIMO radar using unequal-spacing Doppler multiplexing can determine, for example, the Doppler frequency fd corresponding to the target. target Once this is determined, the receiving Doppler frequency for each transmitting antenna can be determined, enabling the separate reception of Doppler multiplexed signals.

[0062] By separating and receiving Doppler multiplexed signals in this way, MIMO radars using unequal-interval Doppler multiplexing transmissions can estimate the Doppler frequency of radar reflections within a Doppler frequency range of, for example, ±1 / (2Tr). Unequal-interval Doppler multiplexing transmissions expand the detectable Doppler frequency range to ±1 / (2Tr). For example, with unequal-interval Doppler multiplexing transmissions, the detectable Doppler frequency range is expanded by Nt times compared to the method described in Patent Document 3.

[0063] [Regarding the application of unequal-interval Doppler multiplexing to multi-beam MIMO radar] As mentioned above, in unequal-spacing Doppler multiplexing, unlike equal-spacing Doppler multiplexing, for example, some Doppler frequency ranges are not allocated to the transmitted signal. The MIMO radar performs a Doppler multiplexing signal separation process that estimates the target's Doppler frequency based on the received power of the received Doppler frequency of the reflected wave from the target.

[0064] Therefore, when applying unequal-spacing Doppler multiplexing to a multi-beam MIMO radar, the following may be considered.

[0065] In multi-beam MIMO radar, for example, the received level of reflected waves can vary greatly depending on the beam direction (or the transmitting beam direction) and the target direction. In multi-beam MIMO radar, the received level of reflected waves from the transmitting antenna can vary greatly depending on whether the beam direction and target direction coincide or not. Therefore, when multiplexing using unequal-spacing Doppler multiplexing in a multi-beam MIMO radar, if there is a large difference in the received level of reflected waves between multi-beams with different beam directions, Doppler multiplexing separation by unequal-spacing Doppler multiplexing may become difficult. If Doppler multiplexing separation becomes difficult, the target detection performance of the MIMO radar may deteriorate, or errors in Doppler multiplexing separation may occur, resulting in Doppler misestimation or deterioration of angle measurement performance.

[0066] The following describes examples where Doppler multiplexing separation becomes difficult in multi-beam transmitting MIMO radars that apply unequal-spacing Doppler multiplexing.

[0067] For example, consider a 4Tx MIMO radar that includes two transmitting antennas for each of the two beam directions. For example, if the number of transmitting antennas corresponding to each of the two beam directions is "N TxBeam#1 " and "N TxBeam#2 This is expressed as " (N TxBeam#1 =N TxBeam#2 =2).

[0068] For example, as shown in Figure 4, we will describe the configuration of a multi-beam transmitting MIMO radar that uses two of the four transmitting antennas Tx#1 to #4 to form two different transmitting beams (TxBeam#1, TxBeam#2) in different directions. In Figure 4, the transmitting beam (beam direction) of Tx#1 and Tx#2 is referred to as TxBeam#1, and the transmitting beam (beam direction) of Tx#3 and Tx#4 is referred to as TxBeam#2. Furthermore, for example, the directional characteristics of the receiving antenna may be omnidirectional, or they may be nearly uniform within the field of view (FOV) covered by multiple transmitting antennas with different directional characteristics.

[0069] For example, let's consider the case where unequally spaced Doppler multiplexed signals are assigned to four transmitting antennas Tx#1 to #4, as shown in Figure 5(a). In Figure 5, the unit of the Doppler shift interval is Δfd = 1 / (5Tr), and the transmitted Doppler frequencies (Hz) assigned to transmitting antennas Tx#1 to Tx#4 are Doppler shift amounts Δfd1 = -1 / (2Tr), Δfd2 = -3 / (10Tr), Δfd3 = -1 / (10Tr), and Δfd4 = 1 / (10Tr), respectively. The transmitted Doppler frequency represented by the "×" mark has a Doppler shift amount Δfd5 = 3 / (10Tr), and this shows the case where no transmitting antennas are assigned.

[0070] For example, if the target direction is target direction (1) as shown in Figure 4, the direction of the reflected wave corresponding to the radar transmission waves transmitted from Tx#1 and Tx#2 that form TxBeam#1 coincides with target direction (1). Therefore, as shown in Figure 5(b), the reception level of the received signal corresponding to Tx#1 and Tx#2 that form TxBeam#1 (e.g., the reflected wave reception level) is relatively high. On the other hand, if the target direction is target direction (1) as shown in Figure 4, the direction of the reflected wave corresponding to the radar transmission waves transmitted from Tx#3 and Tx#4 that form TxBeam#2 does not coincide with target direction (1), and target direction (1) corresponds to the directional null direction of TxBeam#2 (hereinafter also referred to as the null direction). Therefore, as shown in Figure 5(b), for example, the received signal levels of the received signals corresponding to Tx#3 and Tx#4 that form TxBeam#2 are lower than the received signal levels of the received signals corresponding to TxBeam#1 (Tx#1 and Tx#2). For example, the received signal level corresponding to TxBeam#2 differs significantly from the received signal level corresponding to TxBeam#1, and depending on the null-direction beam directivity characteristics of TxBeam#2, it may be more than 10 dB lower.

[0071] Furthermore, for example, if the target direction is an intermediate direction between the beam direction of TxBeam#1 and the beam direction of TxBeam#2, and the beam widths of both beams, which are approximately 3dB or 6dB, overlap in the area direction (for example, the target direction (2) shown in Figure 4), then the reflected waves corresponding to the radar transmission waves transmitted from Tx#1 and Tx#2 that form TxBeam#1 and the reflected waves corresponding to the radar transmission waves transmitted from Tx#3 and Tx#4 that form TxBeam#2 will be received at similar levels, as shown in Figure 5(c).

[0072] Furthermore, for example, if the target direction is the target direction (3) shown in Figure 4, the direction of the reflected wave corresponding to the radar transmission waves transmitted from Tx#3 and Tx#4 that form TxBeam#2 coincides with the target direction (3). Therefore, as shown in Figure 5(d), the reception level of the received signal corresponding to Tx#3 and Tx#4 that form TxBeam#2 (e.g., the reflected wave reception level) is relatively high. On the other hand, if the target direction is the target direction (3) shown in Figure 4, the direction of the reflected wave corresponding to the radar transmission waves transmitted from Tx#1 and Tx#2 that form TxBeam#1 does not coincide with the target direction (3), and the target direction (3) corresponds to the null direction of TxBeam#1. For this reason, as shown in Figure 5(d), for example, the reception level of the received signal corresponding to Tx#1 and Tx#2 that form TxBeam#1 is lower than the reception level of the received signal corresponding to TxBeam#2 (Tx#3 and Tx#4). For example, the received level corresponding to TxBeam#1 differs significantly from the received level corresponding to TxBeam#2, and depending on the beam directivity characteristics of TxBeam#1 in the null direction, it can be more than 10dB lower.

[0073] For example, in the case shown in Figure 5(c), the received level of the reflected wave corresponding to the radar transmitted waves from Tx#1 and Tx#2 forming TxBeam#1 is approximately the same as the received level of the reflected wave corresponding to the radar transmitted waves from Tx#3 and Tx#4 forming TxBeam#2. Based on the received levels of these received signals, the multi-beam MIMO radar can determine which transmitting antenna used for unequal-spacing Doppler multiplexing the detected Doppler frequency peak corresponds to. Also, in Figure 5(c), the Doppler frequency fd of the target reflected wave can be determined to be in the range -1 / (2Tr) ≤ fd < 1 / (2Tr).

[0074] On the other hand, in cases like those shown in Figure 5(b) or Figure 5(d), it is difficult for a multi-beam MIMO radar to determine, based on the received signal level, whether the received level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 has decreased (for example, in the case of Figure 5(d)), or whether the received level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 has decreased (for example, in the case of Figure 5(b)), because the Doppler frequency of the target is unknown. For this reason, it is difficult for a multi-beam MIMO radar to determine, based on the received signal level, which transmitting antenna the detected Doppler frequency peak corresponds to in the unequal-spacing Doppler multiplexing transmission. Therefore, multi-beam MIMO radars have difficulty separating Doppler multiplexed signals, making it difficult to determine the Doppler frequency fd of the reflected wave from the target (for example, called the "target reflected wave") within the range of -1 / (2Tr) ≤ fd < 1 / (2Tr).

[0075] Thus, in unequal-spacing Doppler multiplexing, the Doppler multiplexing separation process is performed on the premise that the received levels of the reflected waves corresponding to each transmitting antenna are approximately the same, and that the received levels of the Doppler shift intervals that are not Doppler multiplexed (marked with ×) are sufficiently low, at the level of noise. In multi-beam transmitting MIMO radars that use unequal-spacing Doppler multiplexing, as shown in Figures 5(b) and (d), the premise for the separation process in unequal-spacing Doppler multiplexing may break down (the received levels corresponding to some beams may decrease), which may lead to errors in the Doppler multiplexing separation process.

[0076] As another example, we will describe the case where unequally spaced Doppler multiplexed signals are assigned to four transmitting antennas Tx#1 to #4, as shown in Figure 6(a). In Figure 6(a), the unit of the Doppler shift interval is Δfd = 1 / (6Tr), and the transmitted Doppler frequencies (Hz) assigned to transmitting antennas Tx#1 to Tx#4 are Doppler shift amounts Δfd1 = -1 / (2Tr), Δfd2 = -1 / (3Tr), Δfd3 = -1 / (6Tr), and Δfd4 = 0, respectively. The two "×" marks represent the transmitted Doppler frequencies with Doppler shift amounts Δfd5 = 1 / (6Tr) and Δfd6 = 1 / (3Tr), respectively, and this shows the case where no transmitting antennas are assigned.

[0077] For example, let's assume that the transmission beam (beam direction) for Tx#1 and Tx#4 is TxBeam#1 as shown in Figure 4, and the transmission beam (beam direction) for Tx#2 and Tx#3 is TxBeam#2 as shown in Figure 4. When the target direction is target direction (1) as shown in Figure 4, the received signal level will be as shown in Figure 6(b); when the target direction is target direction (2) as shown in Figure 4, the received signal level will be as shown in Figure 6(c); and when the target direction is target direction (3) as shown in Figure 4, the received signal level will be as shown in Figure 6(d).

[0078] For example, in the case shown in Figure 6(c), the received levels of the reflected waves corresponding to the radar transmission waves transmitted from Tx#1 and Tx#4 of TxBeam#1 are approximately the same as the received levels of the reflected waves corresponding to the radar transmission waves transmitted from Tx#2 and Tx#3 of TxBeam#2. Based on the received levels of these received signals, the multi-beam MIMO radar can determine which transmitting antenna used for unequal-spacing Doppler multiplexing the detected Doppler frequency peak corresponds to. Also, in Figure 6(c), the Doppler frequency fd of the target reflected wave can be determined to be within the range -1 / (2Tr) ≤ fd < 1 / (2Tr).

[0079] On the other hand, in cases like those shown in Figure 6(b) or Figure 6(d), the multibeam MIMO radar has difficulty determining, based on the received signal level, whether the received level of the reflected wave corresponding to the radar transmission waves transmitted from Tx#1 and Tx#4 of TxBeam#1 has decreased, or whether the received level of the reflected wave corresponding to the radar transmission waves transmitted from Tx#2 and Tx#3 of TxBeam#2 has decreased, because the Doppler frequency of the target is unknown. Therefore, the multibeam MIMO radar has difficulty determining, based on the received signal level, which transmitting antenna the detected Doppler frequency peak corresponds to in the unequal-spacing Doppler multiplexing transmission. Consequently, the multibeam MIMO radar has difficulty separating the Doppler multiplexed signals, and it becomes difficult to determine the Doppler frequency fd of the target reflected wave within the range -1 / (2Tr)≦fd<1 / (2Tr).

[0080] Non-limiting embodiments of this disclosure describe a method for improving the detection performance of a multi-beam MIMO radar using unequal-spacing Doppler multiplexing.

[0081] Hereinafter, an embodiment according to one example of the present disclosure will be described in detail with reference to the drawings. In the embodiment, the same reference numerals are used for the same components, and their descriptions will be omitted as they would be redundant.

[0082] The following describes a radar system configuration in which the transmitting branch simultaneously sends out different multiplexed transmission signals from multiple transmitting antennas, and the receiving branch separates each transmission signal for reception processing (for example, a MIMO radar configuration).

[0083] Furthermore, the configuration of a radar system using frequency-modulated pulse waves, such as chirp pulses (also known as fast chirp modulation), will be described below as an example. However, the modulation method is not limited to frequency modulation. For example, one embodiment of this disclosure is also applicable to a radar system using a pulse-compressed radar that transmits pulse trains with phase modulation or amplitude modulation.

[0084] Furthermore, the radar system may perform, for example, Doppler multiplexing (e.g., unequal-spacing Doppler multiplexing). The radar system may also be equipped with, for example, multiple transmitting antennas having different directional characteristics.

[0085] [Radar equipment configuration] The radar device 10 in Figure 7 includes a radar transmitter (transmitting branch) 100 and a radar receiver (receiving branch) 200.

[0086] The radar transmission unit 100 generates a radar signal (radar transmission signal) and transmits the radar transmission signal at a defined transmission period (for example, called the "radar transmission period") using a transmission antenna unit 105 which is composed of multiple transmitting antennas (for example, Nt antennas).

[0087] The radar receiver 200 receives the reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a receiving antenna unit 202 that includes multiple receiving antennas. The radar receiver 200 processes the reflected wave signal received by each receiving antenna of the receiving antenna unit 202 to perform signal processing, for example, detecting the presence or absence of a target or estimating the arrival distance, Doppler frequency (e.g., relative velocity), and direction of arrival of the reflected wave signal, and outputs information related to the estimation results (e.g., positioning information).

[0088] The radar device 10 may be mounted on a moving object such as a vehicle, and the positioning output from the positioning output unit 300 (for example, information regarding the estimation result) may be connected to an electronic control unit (ECU) (not shown) such as an advanced driver assistance system (ADAS) or an autonomous driving system that enhances collision safety, and used for vehicle drive control or alarm call control.

[0089] Furthermore, the radar device 10 may be mounted on a relatively high structure (not shown), such as a roadside utility pole or traffic light. The radar device 10 may also be used as a sensor in a support system to enhance the safety of passing vehicles or pedestrians, or in an intruder prevention system (not shown). The positioning output of the radar receiver 200 may also be connected to a control device (not shown) in a safety support system or intruder prevention system, and used for alarm call control or anomaly detection control. However, the applications of the radar device 10 are not limited to these, and it may be used for other purposes.

[0090] Furthermore, a target is an object detected by the radar device 10, and includes, for example, vehicles (including four-wheeled and two-wheeled vehicles), people, blocks, or curbs.

[0091] [Configuration of radar transmitter 100] The radar transmission unit 100 includes a radar transmission signal generation unit 101, a Doppler shift unit 104, and a transmission antenna unit 105. The radar transmission signal generation unit 101 and the Doppler shift unit 104 may be collectively referred to as the transmission circuit.

[0092] The radar transmission signal generation unit 101 generates radar transmission signals. The radar transmission signal generation unit 101 includes, for example, a modulation signal generation unit 102 and a VCO (Voltage Controlled Oscillator) 103. The components of the radar transmission signal generation unit 101 will be described below.

[0093] The modulation signal generation unit 102 periodically generates, for example, a modulation signal with a sawtooth shape.

[0094] Based on the modulated signal input from the modulated signal generation unit 102, the VCO 103 outputs a frequency modulated signal (hereinafter referred to as, for example, a frequency chirp signal or chirp signal) as a radar transmission signal (radar transmission wave) as shown in Figure 8 to the Doppler shift unit 104 and the radar receiver unit 200 (mixer unit 204, which will be described later).

[0095] In the following, the modulation signal generation unit 102 generates a modulation signal such that it transmits a chirp signal Nc times for each transmission cycle Tr for each radar positioning operation. The VCO 103 outputs a chirp signal Nc times for each transmission cycle Tr based on the operation of the modulation signal generation unit 102.

[0096] The radar device 10 may, for example, detect time variations in the target position by performing multiple radar positioning operations.

[0097] Furthermore, in the following, each transmission period within the Nc transmission periods Tr is represented by the index "m". Here, m = 1 to Nc.

[0098] Figure 9 shows an example of a chirp signal output from the radar transmission signal generation unit 101.

[0099] As shown in Figure 9, the modulation parameters for the chirp signal include, for example, the center frequency f c , frequency sweep bandwidth B w , sweep start frequency f cstart , sweep end frequency f cend , frequency sweep time T sw , and the frequency sweep rate of change D m It may include D. m =B w / T sw That is. Also, B w =f cend -f cstart and f c =( f cstart +fcend ) / 2.

[0100] Also, the frequency sweep time T sw This corresponds, for example, to the time range (or range gate) for acquiring A / D sample data in the AD conversion unit 207 of the radar receiver unit 200, which will be described later. Frequency sweep time T sw This can be set to the entire section of the chirp signal, for example, as shown in Figure 9(a), or to a portion of the chirp signal, as shown in Figure 9(b).

[0101] Figures 8 and 9 show examples of up-chirp waveforms where the modulation frequency gradually increases over time, but the method is not limited to these; down-chirp waveforms where the modulation frequency gradually decreases over time may also be applied. Similar effects can be obtained regardless of whether the modulation frequency is up-chirp or down-chirp.

[0102] The chirp signal output from the radar transmission signal generation unit 101 is input to each of the Nt Doppler shift units 104. The chirp signal is also input to each of the mixer units 204 of the radar reception unit 200.

[0103] The nth Doppler shift unit 104 applies a predetermined Doppler shift amount DOP to the chirp signal input from the radar transmission signal generation unit 101, for example. n To provide this, a phase rotation Φ is applied for each transmission period Tr of the chirp signal. n (m) is assigned. The nth Doppler shift section 104 is phase rotation Φ n The chirp signal with (m) attached is output to the nth transmitting antenna of the transmitting antenna unit 105 (for example, Tx#n). Here, n = 1 to Nt.

[0104] The transmitting antenna section 105 may include Nt transmitting antennas Tx#1 to Tx#Nt. The transmitting antennas Tx#1 to Tx#Nt may constitute a multi-beam transmitting radar including transmitting antennas for at least two different main beam directions (or beam directions). For example, the Doppler shift section 104 applies a different phase rotation Φ to each transmitting antenna from which a chirp signal is transmitted, based on the configuration of the transmitting antennas corresponding to the multiple beam directions in the transmitting antenna section 105. n (m) may be added to the chirp signal and output to the transmitting antenna unit 105. This allows the radar device 10 to separate Doppler multiplexed signals even when the received levels (e.g., the received power level of the reflected wave) differ significantly between received signals corresponding to transmitting antennas with different beam directions (e.g., when the received level difference or received level ratio is above a threshold), thereby reducing the degradation of positioning performance and radar detection performance (an example of operation will be described later).

[0105] The outputs from the Nt Doppler shift units 104 are amplified to a specified transmission power and then radiated into space from each of the transmitting antennas Tx#1 to Tx#Nt of the transmitting antenna unit 105.

[0106] [Configuration of radar receiver 200] In Figure 7, the radar receiver 200 includes a receiving antenna section 202 containing Na receiving antennas Rx#1 to Rx#Na. The radar receiver 200 also includes Na antenna system processing sections 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) section 210, a Doppler multiplexing / decompression section 211, and a direction estimation section 212. The Na antenna system processing sections 201-1 to 201-Na, the CFAR section 210, the Doppler multiplexing / decompression section 211, and the direction estimation section 212 may be collectively referred to as the receiving circuit. The receiving circuit estimates the direction of the target using the reflected wave signal obtained by reflecting the transmitted signal off the target.

[0107] The receiving antennas Rx#1 to Rx#Na of the receiving antenna unit 202 receive reflected wave signals, which are radar transmission signals reflected by a target, and output the received reflected wave signals as received signals to the corresponding antenna system processing unit 201.

[0108] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206.

[0109] Each signal received by the Na receiving antennas Rx#1 to Rx#Na is output to Na receiving radio units 203. The output signals from the Na receiving radio units 203 are then output to Na signal processing units 206.

[0110] The receiving radio 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, which is the transmission signal, input from the radar transmission signal generation unit 101. The receiving radio unit 203 passes the output of the mixer unit 204 through the LPF 205, for example. This outputs a beat signal with a frequency corresponding to the delay time of the reflected wave signal. For example, as shown in Figure 10, the difference frequency between the frequency of the transmitted chirp signal (transmit frequency modulated wave), which is the transmission signal (radar transmission wave), and the frequency of the received chirp signal (receive frequency modulated wave), which is the received signal (radar reflected wave), is obtained as the beat frequency.

[0111] Each antenna system processing unit 201-z (where z=1 to Na) has a signal processing unit 206 comprising an AD conversion unit 207, a beat frequency analysis unit 208, and a Doppler analysis unit 209.

[0112] The signal output from the LPF205 (for example, a beat signal) is converted into discrete sample data by the AD conversion unit 207 in the signal processing unit 206.

[0113] The beat frequency analysis unit 208 analyzes the N obtained within a defined time range (range gate) for each transmission period Tr.data The discrete sample data is subjected to frequency analysis (e.g., FFT). As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). During the FFT processing, the beat frequency analysis unit 208 may multiply by a window function coefficient, such as a Han window or a Hamming window. By using a window function coefficient, side lobes that occur around the peak of the beat frequency can be suppressed.

[0114] Note N data If N is not a power of 2, then, for example, by including zero-padding data, it is possible to perform an FFT with a data size (FFT size) that is a power of 2. In such cases, the data size including zero-padding data is N data By considering it as such, it can be treated in the same way as above.

[0115] Here, the beat frequency response output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 obtained by transmitting the m-th chirp pulse is called "RFT". z (f b It is represented as , m). Here, f b This represents the beat frequency index and corresponds to the index (bin number) of the FFT. For example, f b =0,~,( N data / 2)-1, z=1~Na, and m=1~N C This is the beat frequency index f. b The smaller the value, the smaller the delay time of the reflected wave signal (for example, the closer the distance to the target), indicating a beat frequency.

[0116] Also, the beat frequency index f b The distance information R(f) is calculated using the following equation (1). b It can be converted to ). Therefore, below, the beat frequency index f b to "distance index f b They call it that.

number

[0117] Here, B w represents the frequency modulation bandwidth within the range gate in the chirp signal, and C0 represents the speed of light. Also, in equation (1), C0 / (2B w ) represents the distance resolution.

[0118] The Doppler analysis unit 209 in the z-th signal processing unit 206 processes 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). z (f b 1), RFT z (f b , 2), ~, RFT z (f b Using Nc), the distance index f b Doppler analysis is performed for each step.

[0119] For example, if Nc is a power of 2, the Doppler analysis unit 209 can apply FFT processing in the Doppler analysis as shown in equation (2) below.

number

[0120] Here, the FFT size is Nc, and the maximum Doppler frequency at which no aliasing occurs, derived from the sampling theorem, is ±1 / (2Tr). Also, the Doppler frequency index f s The Doppler frequency interval is 1 / (Nc×Tr), and the Doppler frequency index f s The range is f s = -Nc / 2, ~, 0, ~, (Nc / 2)-1. Also, j is the imaginary unit, and z=1~Na.

[0121] The following describes the case where Nc is a power of 2 as an example. If Nc is not a power of 2, for example, by including zero-padding data, the FFT processing can be performed with a data size (FFT size) that is a power of 2. Furthermore, the Doppler analysis unit 209 may multiply by window function coefficients such as a Han window or a Hamming window during the FFT processing. Applying a window function can suppress side lobes that occur around the Doppler frequency peak.

[0122] The processing in each component of the signal processing unit 206 has been described above.

[0123] In Figure 7, the CFAR unit 210 performs CFAR processing (e.g., adaptive threshold determination) using the output of the Doppler analysis unit 209 of each of the 1st to Nath signal processing units 206. For example, in CFAR processing, local peaks of the reflected wave received signal of the radar transmission signal transmitted from the transmitting antenna unit 105 may be selectively extracted, and adaptive threshold determination may be performed. The CFAR unit 210 may, for example, use a distance index f that gives a local peak signal. b_cfar and Doppler frequency index f s_cfar The data is extracted and output to the Doppler multiplexing unit 211.

[0124] The Doppler multiplexing / decomposition unit 211 uses, for example, the output of the Doppler analysis unit 209 of the first to Na signal processing units 206 and the output of the CFAR unit 210 to separate the radar reflected wave received signal for each radar transmitted signal sent from multiple transmitting antennas using Doppler multiplexing (hereinafter referred to as "Doppler multiplexing / decomposition").

[0125] The operation of the Doppler multiplexing / decoupling unit 211 is related, for example, to the operation of the Doppler shifting unit 104 of the radar transmitting unit 100. Similarly, the operation of the CFAR unit 210 is related, for example, to the operation of the Doppler shifting unit 104. Below, an example of the operation of the Doppler shifting unit 104 will be described, followed by an example of the operation of the CFAR unit 210 and an example of the operation of the Doppler multiplexing / decoupling unit 211.

[0126] [Example of operation of the Doppler shift unit 104 in the radar transmitter unit 100] The first to Nt Doppler shift units 104 each apply different Doppler shift amounts DOP to the radar transmission signal input to them. n The radar device 10 transmits radar transmission signals from Nt transmitting antennas (Doppler multiplex transmission), to which a phase rotation corresponding to the Doppler shift amount assigned to each of the Nt transmitting antennas by the Doppler shift unit 104 is applied.

[0127] The following section describes an example where a chirp signal is used as the radar transmission signal.

[0128] For example, the nth Doppler shift unit 104 applies a specified Doppler shift amount DOP to the nth transmitting antenna Tx#n. n To add this, a phase rotation Φ is applied for each transmission period Tr of the input chirp signal. n The output is given (m). Here, the Doppler shift unit 104 assigns a different Doppler shift to each transmitting antenna to which the chirp signal is transmitted, and performs a phase rotation Φ. n (m) may be added to the chirp signal and output. Here, n = 1 to Nt. For example, the phase rotation Φ added for each transmission period Tr of the chirp signal. n (m) is Φ n (m) = 2πDOP n ×Tr may be used to set it.

[0129] For example, the transmitting antennas Tx#1 to Tx#Nt of the transmitting antenna unit 105 constitute a multi-beam transmitting radar that includes transmitting antennas corresponding to at least two different beam directions (e.g., transmitting antennas that form at least two different beams). For example, the Doppler shift unit 104 takes into account the configuration of transmitting antennas Tx#1 to Tx#Nt with different beam directions and applies a different phase rotation Φ to each transmitting antenna from which a chirp signal is transmitted. n(m) may be added to the chirp signal and output. This allows the radar device 10 to separate Doppler multiplexed signals even when the received power levels of the reflected waves differ significantly between the received signals corresponding to the chirp signals transmitted from transmitting antennas with different beam directions, thereby improving the positioning performance and radar detection performance of the radar device 10.

[0130] Note that the transmitting antennas Tx#1 to Tx#Nt may include multiple transmitting antennas corresponding to different beam directions. Also, the transmitting antennas Tx#1 to Tx#Nt may include multiple transmitting antennas corresponding to the same beam direction.

[0131] The radar device 10 is, for example, a multi-beam transmitting MIMO radar that uses Nt transmitting antennas Tx#1 to Tx#Nt, including transmitting antennas with different beam directions, and may perform unequal-spacing Doppler multiplexing using Nt transmitting antennas Tx#1 to Tx#Nt.

[0132] Furthermore, the radar device 10 may simultaneously multiplex radar transmission signals from Nt transmitting antennas Tx#1 to Tx#Nt using Doppler multiplexing that satisfies the following condition 1.

[0133] In the following description, among the multiple beam directions (or beams) used in a multi-beam transmitting MIMO radar, the first beam direction (or beam) will be referred to as "B1", the second beam direction (or beam) as "B2", and so on. Furthermore, for example, the qth beam direction (or beam) will be referred to as "Bq". q is an integer value within a different number of beam directions (e.g., multi-beam number NB). For example, if multi-beam number NB = 2, then q = 1 or 2.

[0134] Furthermore, the number of transmitting antennas Nt ≥ 3. For example, the number of Doppler multiplexers N DDM Assume Nt ≥ 3. Note that the number of transmitting antennas is not limited to Nt ≥ 3; for example, Nt = 2 is also acceptable. The case where Nt = 2 will be described later in Modification 1.

[0135] Also, in the transmission antenna unit 105, the number of transmission antennas corresponding to the beam direction B1 is N B1 and the number of transmission antennas corresponding to the beam direction B2 is N B2 In this case, N B1 +N B2 = Nt. Also, the radar device 10 may, for example, assign one Doppler multiplexed signal to one transmission antenna.

[0136] <Condition 1> Among the Doppler multiplexed signals assigned to each of the transmission antennas in the beam direction B1 and the transmission antennas in the beam direction B2, any one of the following conditions is satisfied. (1) The Doppler multiplex numbers corresponding to each beam direction are the same (for example, N B1 = N B2 . However, considering the case where N B1 ≧2 and N B2 ≧2, N NB1 = N NB2 = 1 is not considered), and different Doppler shift intervals are included in each beam direction. (2) The Doppler multiplex numbers (or the number of transmission antennas) for each beam direction are different (N B1 ≠ N B2 ). (3) When N B1 ≧3 and N B2 ≧3, the Doppler multiplex numbers corresponding to each beam direction are the same (N B1 = N B2 ), and when the same Doppler shift interval is included in the Doppler shift intervals for each beam direction, the order of the Doppler shift intervals is different.

[0137] Also, the radar device 10 may, for example, further perform simultaneous multiplex transmission of radar transmission signals from Nt transmission antennas Tx#1 to Tx#Nt using Doppler multiplex transmission that satisfies the following Condition 2.

[0138] <Condition 2> Non-uniform interval Doppler multiplexing by the transmission antennas in the beam direction B1 (however, considering the case where N B1 ≧2, N NB1(not considered when =1), Uneven Doppler multiplexing by the transmission antenna in the beam direction B2 (however, N B2 Considered when ≧2, N NB2 (not considered when =1), Doppler multiplexing signals are assigned to each of the beam directions B1 and B2 so that it becomes.

[0139] For example, in (1) of condition 1, the Doppler multiplexing number N by the transmission antenna in the beam direction B1 B1 and the Doppler multiplexing number N by the transmission antenna in the beam direction B2 B2 When they are the same, at least one of the intervals of the Doppler shift amounts (Doppler shift intervals) assigned to the transmission antenna in the beam direction B1 may be different from each of the intervals of the Doppler shift amounts assigned to the transmission antenna in the beam direction B2. As an example of (1) of condition 1, cases where the maximum Doppler shift interval is different, cases where the minimum Doppler shift interval is different, or cases where the Doppler shift interval that is neither the maximum nor the minimum is different among the Doppler multiplexing signals assigned to the transmission antennas in the beam directions B1 and B2 can be cited.

[0140] Also, for example, in (2) of condition 1, the Doppler multiplexing number (for example, the number of transmission antennas) N by the transmission antenna in the beam direction B1 B1 and the Doppler multiplexing number (for example, the number of transmission antennas) N by the transmission antenna in the beam direction B2 B2 may be different.

[0141] Also, for example, in (3) of condition 1, the Doppler multiplexing number N by the transmission antenna in the beam direction B1 B1 and the Doppler multiplexing number N by the transmission antenna in the beam direction B2 B2If the two are the same, and the values ​​of each of the multiple intervals of the Doppler shift amount assigned to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 are the same (for example, combinations of Doppler shift intervals), then the order on the Doppler frequency axis of the multiple Doppler shift intervals corresponding to the transmitting antenna in beam direction B1 and the order on the Doppler frequency axis of the multiple Doppler shift intervals corresponding to the transmitting antenna in beam direction B2 may be different.

[0142] For example, the combination of intervals in an array (e.g., a first array) in which the intervals of the Doppler shift amounts assigned to the transmitting antenna in beam direction B1 are arranged in ascending order of the Doppler frequency axis matches the combination of intervals in an array (e.g., a second array) in which the intervals of the Doppler shift amounts assigned to the transmitting antenna in beam direction B2 are arranged in ascending order of the Doppler frequency axis, and the first array and the second array are different in circular permutations.

[0143] If condition 1(3) is met, the Doppler shift interval of the transmitting antenna in beam direction B1 and the Doppler shift interval of the transmitting antenna in beam direction B2 will not coincide even if either one is cyclically shifted in the Doppler frequency domain.

[0144] Furthermore, for example, under condition 2, the intervals of the Doppler shift amounts assigned to the transmitting antenna in beam direction B1 on the Doppler frequency axis may be set to unequal intervals. Similarly, under condition 2, the intervals of the Doppler shift amounts assigned to the transmitting antenna in beam direction B2 on the Doppler frequency axis may be set to unequal intervals. Note that under condition 2, unequal-interval Doppler multiplexing may be applied to either or both of beam directions B1 and B2.

[0145] Thus, in unequal-spacing Doppler multiplexing by the radar device 10, which is a multi-beam transmitting MIMO radar, the intervals of the Doppler shift amounts assigned to each of the multiple transmitting antennas included in the transmitting antenna unit 105 are unequal on the Doppler frequency axis. Furthermore, for example, the pattern of the Doppler shift amount assigned to the transmitting antenna in beam direction B1 (e.g., the pattern relating to the Doppler shift interval, or the number of transmitting antennas (Doppler multiplexing number), and the order of the Doppler shift amount intervals on the Doppler frequency axis) is different from the pattern of the Doppler shift amount assigned to the transmitting antenna in beam direction B2 (corresponding to condition 1).

[0146] As a result, even when the received power levels of reflected waves differ significantly between received signals from transmitting antennas with different beam directions, the radar device 10 can separate Doppler multiplexed signals, thereby suppressing degradation of positioning performance and radar detection performance.

[0147] Furthermore, for example, the intervals between the Doppler shift amounts assigned to the transmitting antennas corresponding to each of the multiple beam directions among the multiple transmitting antennas included in the transmitting antenna section 105 may be unequal (corresponding to condition 2). By satisfying condition 2, the Doppler frequency range detectable by the radar device 10 becomes the range -1 / (2Tr) ≤ fd < 1 / (2Tr), and the Doppler detection range in the case of equally spaced Doppler multiplex transmission is -1 / (2 N t Tr)≦fd < 1 / (2 N t It can be magnified more than Tr).

[0148] For example, in Doppler multiplexing by radar device 10, both conditions 1 and 2 may be satisfied, or condition 1 may be satisfied but condition 2 may not be satisfied. Three cases can be given in which condition 1 is satisfied but condition 2 is not satisfied.

[0149] (Case 1) Case 1 is a case of equally spaced Doppler multiplexing between transmitting antennas in beam direction B1 and between transmitting antennas in beam direction B2 (where N B1≥2, N B2 Considering ≥2, N NB1 =N NB2 (Consideration is not needed when =1). In Case 1, the detectable Doppler frequency range fd in the radar device 10 depends on the target direction and is in the range of -1 / (2Tr)≦fd < 1 / (2Tr), -1 / (2 N B1 Tr)≦fd < 1 / (2 N B1 The range of Tr), or -1 / (2 N B2 Tr)≦fd < 1 / (2 N B2 This falls within the range of Tr).

[0150] (Case 2) Case 2 is the case where the transmitting antennas in beam direction B1 are connected via unequal spacing Doppler multiplexing, and the transmitting antennas in beam direction B2 are connected via equal spacing Doppler multiplexing (where N B1 ≥2, N B2 Considering ≥2, N NB1 =N NB2 (Consideration is not needed when =1). In case 2, the detectable Doppler frequency range fd in the radar device 10 depends on the direction of the target and is in the range of -1 / (2 Tr) ≤ fd < 1 / (2Tr), or -1 / (2 N B2 Tr)≦fd < 1 / (2 N B2 This falls within the range of Tr).

[0151] (Case 3) Case 3 is the case where the transmitting antennas in beam direction B1 are equally spaced Doppler multiplexed, and the transmitting antennas in beam direction B2 are unequally spaced Doppler multiplexed (where N B1 ≥2, N B2 Considering ≥2, N NB1 =N NB2 (Consideration is not needed if =1). In case 3, the detectable Doppler frequency range fd in the radar device 10 depends on the direction of the target and is in the range of -1 / (2 Tr) ≤ fd < 1 / (2Tr), or -1 / (2 N B1 Tr)≦fd < 1 / (2 N B1 This falls within the range of Tr).

[0152] In any of cases 1 to 3, the detectable Doppler frequency range is the Doppler detection range in the case of equally spaced Doppler multiplexing - 1 / (2 N t Tr)≦fd < 1 / (2 N t It can be magnified more than Tr).

[0153] Furthermore, since the Doppler analysis unit 209 performs Doppler frequency analysis on the output of the beat frequency analysis unit 208 for each distance index at the transmission period Tr, the Doppler frequency f derived from the sampling theorem is obtained without aliasing. d The range is -1 / (2Tr) ≤ fd Since <1 / (2Tr), even for Doppler frequencies exceeding this range, the range of observed Doppler frequencies fd is -1 / (2Tr) ≤ fd < 1 / (2Tr).

[0154] For example, if the Doppler shift section 104 is -1 / (2Tr)≦fd When applying a Doppler shift within the range <1 / (2Tr), the maximum Doppler shift interval for Nt transmitting antennas (= Doppler multiplexing number) is Δfdmax = 1 / (TrNt) = 1 / (TrN DM ) The Doppler shift unit 104 may, for example, set the Doppler shift interval to an interval smaller than Δfdmax. The phase rotation φ that gives such a Doppler shift amount can be set, for example, in the range of -π≦φ<π.

[0155] In the following explanation of the operation of the Doppler shift unit 104, if a phase rotation φ0 exceeding the range -π ≤ φ < π is applied, a phase rotation φ0 + 2πα that is in phase within the range from -π to π may be applied. Here, α is an integer value such that -π ≤ φ0 + 2πα < π.

[0156] Furthermore, the Doppler shift interval applied to the Doppler multiplexed signal set by the Doppler shift unit 104 may be set in units of Δfd, as shown in equation (3) below. Here, δ > 0, and δ may be a positive integer or a positive real number. By setting δ to a positive integer, the processing in the CFAR unit 210, which will be described later, can be simplified. Note that the following shows the case where δ is a positive integer, but it is not limited to this, and a positive real number may also be used.

number

[0157] Furthermore, in equation (3), if δ is a positive integer such that δ > 1, there are multiple Doppler shift amounts to which no Doppler multiplexed signals are assigned (for example, Doppler shift amounts indicated by the "×" mark in the diagram used in the example of setting the Doppler shift amount below). In this case, for example, by assigning Doppler multiplexed signals to which these Doppler shift amounts are not equally spaced, the Doppler frequency range fd that the radar device 10 can detect can be set to the range of -1 / (2Tr) ≤ fd < 1 / (2Tr).

[0158] The following describes examples of setting the Doppler shift amount in the Doppler shift unit 104. Note that the Doppler shift amount for each transmitting antenna may be assigned in ascending order, descending order, or randomly with respect to the transmitting Doppler frequency, and each setting example is merely one example.

[0159] <Example 1 of setting the Doppler shift amount> Figure 11 shows the number of transmitting antennas Nt=3, N B1 =2, N B2 An example of setting the pattern for the Doppler shift amount with respect to the transmit Doppler frequency when = 1 is shown. In Figure 11, Tx#1 and Tx#2 are the transmitting antennas in beam direction B1 (for example, the transmitting antennas that form the transmit beam B1), and Tx#3 is the transmitting antenna in beam direction B2 (for example, the transmitting antennas that form the transmit beam B2).

[0160] In the example of setting the Doppler shift amount 1, as shown in Figure 11, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd = 1 / (Tr × (N DM We set δ = 1 / (4Tr) and δ = 1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0161] In the example shown in Figure 11, the first to third Doppler shift units 104 (or Doppler shift units 104-1, 104-2, and 104-3) may perform the following operations.

[0162] The first Doppler shift unit 104, for example, to apply a Doppler shift amount DOP1 = -1 / (2Tr) to the first transmitting antenna Tx#1, outputs a phase rotation Φ1(m) = 2πDOP1 × (m-1)Tr = -π(m-1) for each transmission period Tr of the chirp signal.

[0163] The second Doppler shift unit 104, for example, to apply a Doppler shift amount DOP2 = -1 / (4Tr) to the second transmitting antenna Tx#2, outputs a phase rotation Φ2(m) = 2πDOP2 × (m-1)Tr = -π(m-1) / 2 for each transmission period Tr of the chirp signal.

[0164] The third Doppler shift unit 104 outputs a phase rotation Φ3(m) = 2πDOP3 × (m-1)Tr = 0 for each transmission period Tr of the chirp signal, for example, in order to apply a Doppler shift amount DOP3 = 0 to the third transmitting antenna Tx#3.

[0165] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is defined as the Doppler shift interval "Δfd (n1, n2) This is written as ". Here, Δfd (n1, n2) This is the Doppler shift amount Δfd assigned to Tx#n1. n1 The Doppler shift amount Δfd assigned to Tx#n2 based on [reference value] n2 interval (Δfd n2 -Δfd n1 ) represents the Doppler shift interval Δfd(n1, n2) When it becomes a negative value (for example, (Δfd n2 -Δfd n1 If )<0, then considering the reflection within the observation range of the Doppler analysis unit 209, which is -1 / (2Tr) or greater and less than 1 / (2Tr), Δfd (n1, n2) = 1 / Tr-Δfd (n1, n2) Using the Doppler shift interval Δfd (n1, n2) The Doppler shift interval Δfd from this point onward is calculated and expressed as a positive value. (n1, n2) The same notation is used for the following descriptions.

[0166] In Figure 11, the pattern of the intervals between the Doppler shift amounts applied to each transmitting antenna Tx#1, Tx#2, and Tx#3 (Doppler shift interval) is Δfd (1, 2) =Δfd, Δfd (2, 3) =Δfd, Δfd (3,1) = 2Δfd. Therefore, in Figure 11, the intervals of the Doppler shift amounts applied to each transmitting antenna with a 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) This results in unequal-interval Doppler multiplexing (unequal-interval DDM transmission).

[0167] Furthermore, in Figure 11, the Doppler shift interval between transmitting antennas Tx#1 and Tx#2 in beam direction B1 is Δfd (1, 2) =Δfd, Δfd (2, 1) = 3Δfd. Therefore, the number of transmitting antennas N in beam direction B1. B1 The intervals of the Doppler shift amounts applied to each transmitting antenna in the Δfd = 2 range are not all the same, but include unequal intervals. (1, 2) ≠Δfd (2, 1) ), this will be unequal-spacing Doppler multiplexing (unequal-spacing DDM transmission) using a transmitting antenna in beam direction B1.

[0168] Furthermore, in Figure 11, the number of transmitting antennas in beam direction B2 is N. B2Since = 1, this is a case where Doppler multiplexing does not occur with a transmitting antenna in beam direction B2.

[0169] Based on the above, the example shown in Figure 11 is an example of setting a pattern for the Doppler shift amount that satisfies condition 2.

[0170] Also, in Figure 11, N B1 (=2) ≠ N B2 (=1). For example, in the example shown in Figure 11, the pattern of Doppler shift assigned to the transmitting antenna in beam direction B1 is different from the pattern of Doppler shift assigned to the transmitting antenna in beam direction B2.

[0171] Therefore, the example shown in Figure 11 is an example of setting a pattern for the Doppler shift amount that satisfies condition 1(2).

[0172] The following describes an example of a received signal at the output of the Doppler analysis unit 209 when the transmitting antenna unit 105 includes transmitting antennas with beam directions B1 and B2 based on the Doppler shift amount setting shown in Figure 11, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with substantially uniform directional characteristics within the field of view covered by both transmitting antennas with beam directions B1 and B2).

[0173] Figure 12 shows an example of the output of the Doppler analysis unit 209 of a target reflected wave at a certain distance index. For example, the target reflected wave has fd target This includes the Doppler frequency. Therefore, as shown in Figure 12, the radar device 10 calculates fd from the Doppler shift amount shown in Figure 11. target It receives a signal that has undergone a Doppler shift of a few minutes.

[0174] Figure 13 also shows an example of a multi-beam transmitting MIMO radar (e.g., radar device 10) that forms transmitting beams in beam direction B1 (Tx Beam #1) and beam direction B2 (Tx Beam #2).

[0175] For example, when the target direction is target direction (1) as shown in Figure 13 (for example, when a target exists around beam direction B1), the radiation direction of the radar transmitted waves sent from Tx#1 and Tx#2 in beam direction B1 coincides with the target direction. Therefore, as shown in Figure 12(a), the reception level of the received signals of the reflected waves from the target corresponding to Tx#1 and Tx#2 in the radar device 10 is relatively high. On the other hand, when the target direction is target direction (1) as shown in Figure 13, the radiation direction of the radar transmitted waves sent from Tx#3 in beam direction B2 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmitting beam B2. Therefore, as shown in Figure 12(a), the reception level of the received signals of the reflected waves from the target corresponding to Tx#3 in the radar device 10 is lower than the reception level of the received signals corresponding to Tx#1 and Tx#2. For example, as shown in Figure 12(a), the received level of the received signal corresponding to Tx#3 differs significantly from the received levels of the received signals corresponding to Tx#1 and Tx#2, and can be 10 dB or more lower depending on the beam directivity characteristics of Tx#3 in the null direction.

[0176] Furthermore, for example, if the target direction is an intermediate direction between beam direction B1 and beam direction B2, and the target direction is the area direction where the beam widths of both beams, which are approximately 3dB or 6dB, overlap (for example, target direction (2) shown in Figure 13), then, as shown in Figure 12(b), the received signal levels corresponding to Tx#1 and Tx#2 in beam direction B1 and the received signal levels corresponding to Tx#3 in beam direction B2 are approximately the same.

[0177] Furthermore, for example, if the target direction is the target direction (3) shown in Figure 13 (for example, if a target exists around beam direction B2), the radiation direction of the radar transmission wave transmitted from Tx#3 in beam direction B2 coincides with the target direction. Therefore, as shown in Figure 12(c), the reception level of the received signal of the reflected wave from the target corresponding to Tx#3 in the radar device 10 is relatively high. On the other hand, if the target direction is the target direction (3) shown in Figure 13, the radiation direction of the radar transmission waves transmitted from Tx#1 and Tx#2 in beam direction B1 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmitting beam B1. Therefore, as shown in Figure 12(c), the reception level of the received signals of the reflected waves from the targets corresponding to Tx#1 and Tx#2 in the radar device 10 is lower than the reception level of the received signal corresponding to Tx#3. For example, as shown in Figure 12(c), the received signal levels corresponding to Tx#1 and Tx#2 differ significantly from those corresponding to Tx#3, and can be 10 dB or more lower, depending on the null beam directivity characteristics of Tx#1 and Tx#2.

[0178] For example, as shown in Figure 12(b), when the target direction is an intermediate direction between beam direction B1 and beam direction B2 (target direction (2) shown in Figure 13), the radar device 10 receives the received signals corresponding to the transmitting antennas in each beam direction at approximately the same reception level. Therefore, the signals transmitted from Nt transmitting antennas, including the transmitting antennas in beam direction B1 and beam direction B2, are Doppler multiplexed using Doppler shift intervals that result in unequal Doppler multiplexing. Thus, the radar device 10 can separate the Doppler multiplexed signals based on existing Doppler multiplexed signal separation operations (existing Doppler multiplexed signal separation operations are disclosed, for example, in Patent Documents 6 and 7. The same applies to the following embodiments).

[0179] Furthermore, as shown in Figure 12(a), when the target direction is beam direction B1 (target direction (1) shown in Figure 13), and as shown in Figure 12(c), when the target direction is beam direction B2 (target direction (3) shown in Figure 13), the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 1(2)) depending on the target direction. For example, in the case of Figure 12(a) (target direction (1) shown in Figure 13), the radar device 10 receives a Doppler shift interval Δfd (1, 2) or Δfd (2, 1) The radar device receives signals with two Doppler frequency components. On the other hand, for example, in the case of (c) in Figure 12 (in the case of the target direction (3) shown in Figure 13), the radar device 10 receives a signal with one Doppler frequency component.

[0180] Thus, when the target direction is beam direction B1 or B2, the radar device 10 receives reflected wave signals containing Doppler frequency components with different patterns depending on whether the received level of the received signal corresponding to the transmitting antenna in beam direction B1 decreases or whether the received level of the received signal corresponding to the transmitting antenna in beam direction B2 decreases.

[0181] As a result, the radar device 10 can determine, for example, based on the detected Doppler frequency peaks (e.g., the number of peaks), whether a decrease in the received signal level of the received signal corresponding to the transmitting antenna in beam direction B1 has occurred (e.g., state (c) in Figure 12), or whether a decrease in the received signal level of the received signal corresponding to the transmitting antenna in beam direction B2 has occurred (e.g., state (a) in Figure 12), in the Doppler multiplexing / decompression unit 211 described later.

[0182] Furthermore, for example, Doppler multiplexed signals transmitted from transmitting antennas Tx#1 and Tx#2 in beam direction B1 are transmitted using Doppler shift intervals that result in unequal Doppler multiplexing. Therefore, for example, if the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the received signal of transmitting antennas Tx#1 and Tx#2 in beam direction B1, the radar device 10 can separate the Doppler multiplexed signals using the existing Doppler multiplexed signal separation operation.

[0183] Furthermore, for example, the transmitting antenna Tx#3 in beam direction B2 is a single-antenna transmitter. Therefore, for example, if the Doppler multiplexing / deselection unit 211 determines that the received signal is the received signal corresponding to the transmitting antenna Tx#3 in beam direction B2, the radar device 10 does not need to perform Doppler multiplexing signal separation processing for the received signal in beam direction B2.

[0184] Through the operation of the Doppler multiplexing / decomposition unit 211, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0185] <Example 2 of setting the Doppler shift amount> Figure 14 shows the number of transmitting antennas Nt=4, N B1 =2, N B2 An example of setting the pattern of the Doppler shift amount with respect to the transmit Doppler frequency when = 2 is shown. In Figure 14, Tx#1 and Tx#2 are the transmitting antennas in beam direction B1 (for example, the transmitting antennas that form the transmit beam B1), and Tx#3 and Tx#4 are the transmitting antennas in beam direction B2 (for example, the transmitting antennas that form the transmit beam B2).

[0186] In the example of setting the Doppler shift amount 2, as shown in Figure 14, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd = 1 / (Tr × (N DM We set δ = 1 / (5Tr) and δ = 1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0187] In the example shown in Figure 14, the first to fourth Doppler shift units 104 (or Doppler shift units 104-1 to 104-4) may perform the following operations.

[0188] The first Doppler shift unit 104 outputs a phase rotation Φ1(m) = -π(m-1) for each transmission period Tr of the chirp signal in order to apply a Doppler shift amount DOP1 = -1 / (2Tr) to the first transmitting antenna Tx#1, for example.

[0189] The second Doppler shift unit 104 outputs a phase rotation Φ2(m) = -3π(m-1) / 5 for each transmission period Tr of the chirp signal in order to apply a Doppler shift amount DOP2 = -3 / (10Tr) to the second transmitting antenna Tx#2, for example.

[0190] The third Doppler shift unit 104 outputs a phase rotation Φ3(m) = -π(m-1) / 5 for each transmission period Tr of the chirp signal in order to apply a Doppler shift amount DOP3 = -1 / (10Tr) to the third transmitting antenna Tx#3, for example.

[0191] The fourth Doppler shift unit 104, for example, to apply a Doppler shift amount DOP4 = 3 / (10Tr) to the fourth transmitting antenna Tx#4, outputs a phase rotation Φ4(m) = 3π(m-1) / 5 for each transmission period Tr of the chirp signal.

[0192] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is defined as the Doppler shift interval "Δfd (n1, n2) It is written as "".

[0193] In Figure 14, the interval between the Doppler shift amounts applied to each transmitting antenna Tx#1 to Tx#4 (Doppler shift interval) is Δfd (1, 2) =Δfd, Δfd (2, 3) =Δfd, Δfd (3, 4) =2Δfd, Δfd (4, 1) =Δfd. Therefore, in Figure 14, the intervals of the Doppler shift amounts applied to each transmitting antenna with a 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)This results in unequal-interval Doppler multiplexing (unequal-interval DDM transmission).

[0194] Furthermore, in Figure 14, the Doppler shift interval between transmitting antennas Tx#1 and Tx#2 in beam direction B1 is Δfd (1, 2) =Δfd, Δfd (2, 1) = 4Δfd. Therefore, the number of transmitting antennas N in beam direction B1. B1 The intervals of the Doppler shift amounts applied to each transmitting antenna in the Δfd = 2 range are not all the same, but include unequal intervals. (1, 2) ≠Δfd (2, 1 ), this will be unequal-spacing Doppler multiplexing (unequal-spacing DDM transmission) using a transmitting antenna in beam direction B1.

[0195] Furthermore, in Figure 14, the Doppler shift interval between transmitting antennas Tx#3 and Tx#4 in beam direction B2 is Δfd (3, 4) =2Δfd, Δfd (4, 3) = 3Δfd. Therefore, the number of transmitting antennas N in beam direction B2. B2 The intervals of the Doppler shift amounts applied to each transmitting antenna in the Δfd = 2 range are not all the same, but include unequal intervals. (3, 4) ≠Δfd (4, 3) ), this will be unequal-spacing Doppler multiplexing (unequal-spacing DDM transmission) using a transmitting antenna with beam direction B2.

[0196] Based on the above, the example shown in Figure 14 is an example of setting a pattern for the Doppler shift amount that satisfies condition 2.

[0197] Furthermore, in Figure 14, the interval of the Doppler shift between transmitting antennas Tx#1 and Tx#2 in beam direction B1 is Δfd (1, 2) =Δfd, Δfd (2, 1) = 4Δfd, and the interval of the Doppler shift between transmitting antennas Tx#3 and Tx#4 in beam direction B2 is Δfd (3, 4) =2Δfd, Δfd (4, 3)= 3Δfd. Therefore, the Doppler shift between transmitting antennas Tx#1 and Tx#2 in beam direction B1, and the Doppler shift between transmitting antennas Tx#3 and Tx#4 in beam direction B2, include different Doppler shift intervals.

[0198] For example, the maximum DDM interval for the Doppler shift between transmitting antennas Tx#1 and Tx#2 in beam direction B1 is Δfd (2, 1) = 4Δfd, and the maximum DDM interval for the Doppler shift between transmitting antennas Tx#3 and Tx#4 in beam direction B2 is Δfd (4, 3) = 3Δfd, and they are different from each other. Similarly, for example, the minimum DDM interval for the Doppler shift between transmitting antennas Tx#1 and Tx#2 in beam direction B1 is Δfd (1, 2) =Δfd, and the minimum DDM interval for the Doppler shift between transmitting antennas Tx#3 and Tx#4 in beam direction B2 is Δfd (3, 4) = 2Δfd, and they are distinct from one another.

[0199] Thus, in the example shown in Figure 14, the Doppler multiplexing number N is achieved by the transmitting antennas Tx#1 and Tx#2 in beam direction B1. B1 And the Doppler multiplexing number N is generated by transmitting antennas Tx#3 and Tx#4 in beam direction B2. B2 These are the same, and the patterns of the Doppler shift amounts assigned to the transmitting antennas Tx#1 and Tx#2 in beam direction B1 and the transmitting antennas Tx#3 and Tx#4 in beam direction B2 are different (for example, the Doppler shift interval).

[0200] Based on the above, the example shown in Figure 14 is an example of setting a pattern for the Doppler shift amount that satisfies condition 1(1).

[0201] The following describes an example of a received signal at the output of the Doppler analysis unit 209 when the transmitting antenna unit 105 includes transmitting antennas with different beam directions B1 and B2 based on the Doppler shift amount setting shown in Figure 14, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with substantially uniform directional characteristics within the field of view covered by both transmitting antennas in beam direction B1 and beam direction B2).

[0202] Figure 15 shows an example of the output of the Doppler analysis unit 209 of a target reflected wave at a certain distance index. For example, the target reflected wave has fd target This includes the Doppler frequency. Therefore, as shown in Figure 15, the radar device 10 calculates fd from the Doppler shift amount shown in Figure 14. target It receives a signal that has undergone a Doppler shift of a few minutes.

[0203] Furthermore, in Example 2 of the configuration, we will describe an example of a multi-beam transmitting MIMO radar (for example, radar device 10) that forms transmitting beams with beam directions B1 (Tx Beam #1) and B2 (Tx Beam #2) similar to those in Figure 13.

[0204] For example, when the target direction is target direction (1) as shown in Figure 13 (for example, when a target exists around beam direction B1), the radiation direction of the radar transmitted waves sent from Tx#1 and Tx#2 in beam direction B1 coincides with the target direction. Therefore, as shown in Figure 15(a), the reception level of the received signals of the reflected waves from the target corresponding to Tx#1 and Tx#2 in the radar device 10 is relatively high. On the other hand, when the target direction is target direction (1) as shown in Figure 13, the radiation direction of the radar transmitted waves sent from Tx#3 and Tx#4 in beam direction B2 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmitting beam B2. Therefore, as shown in Figure 15(a), the reception level of the received signals of the reflected waves from the target corresponding to Tx#3 and Tx#4 in the radar device 10 is lower than the reception level of the received signals corresponding to Tx#1 and Tx#2. For example, as shown in Figure 15(a), the received signal levels corresponding to Tx#3 and Tx#4 differ significantly from those corresponding to Tx#1 and Tx#2, and can be, for example, 10 dB or more lower, depending on the null-direction beam directivity characteristics of Tx#3 and Tx#4.

[0205] Furthermore, for example, if the target direction is an intermediate direction between beam direction B1 and beam direction B2, and the target direction is the area direction where the beam widths of both beams overlap by approximately 3 dB or 6 dB (for example, target direction (2) shown in Figure 13), then, as shown in Figure 15(b), the received signal levels corresponding to Tx#1 and Tx#2 in beam direction B1 and the received signal levels corresponding to Tx#3 and Tx#4 in beam direction B2 are approximately the same.

[0206] Furthermore, for example, if the target direction is target direction (3) as shown in Figure 13, the radiation direction of the radar transmitted waves sent from Tx#3 and Tx#4 in beam direction B2 coincides with the target direction. Therefore, as shown in Figure 15(c), the reception level of the received signals of the reflected waves from the target corresponding to Tx#3 and Tx#4 in the radar device 10 is relatively high. On the other hand, if the target direction is target direction (3) as shown in Figure 13, the radiation direction of the radar transmitted waves sent from Tx#1 and Tx#2 in beam direction B1 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmitting beam B1. Therefore, as shown in Figure 15(c), the reception level of the received signals of the reflected waves from the target corresponding to Tx#1 and Tx#2 in the radar device 10 is lower than the reception level of the received signals corresponding to Tx#3 and Tx#4. For example, as shown in Figure 15(c), the received levels of the received signals corresponding to Tx#1 and Tx#2 differ significantly from those of the received signals corresponding to Tx#3 and Tx#4, and can be, for example, 10 dB or more lower, depending on the null-direction beam directivity characteristics of Tx#1 and Tx#2.

[0207] For example, as shown in Figure 15(b), when the target direction is an intermediate direction between beam direction B1 and beam direction B2 (target direction (2) shown in Figure 13), the radar device 10 receives the received signals corresponding to the transmitting antennas for each beam direction at approximately the same reception level. Therefore, the signals transmitted from Nt transmitting antennas, including the transmitting antennas for beam direction B1 and beam direction B2, are Doppler multiplexed using Doppler shift intervals that result in unequal Doppler multiplexing. Thus, the radar device 10 can separate the Doppler multiplexed signals based on the existing Doppler multiplexed signal separation operation.

[0208] Furthermore, as shown in Figure 15(a), when the target direction is beam direction B1 (target direction (1) shown in Figure 13), and as shown in Figure 15(c), when the target direction is beam direction B2 (target direction (3) shown in Figure 13), the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 1(1)) depending on the target direction. For example, in the case of Figure 15(a) (target direction (1) shown in Figure 13), the radar device 10 receives a Doppler shift interval Δfd (1, 2) or Δfd (2, 1) The radar device 10 receives signals of two Doppler frequency components. On the other hand, for example, in the case of (c) in Figure 15 (in the case of the target direction (3) shown in Figure 13), the Doppler shift interval Δfd (3, 4) or Δfd (4, 3) It receives signals with two Doppler frequency components.

[0209] Thus, when the target direction is beam direction B1 or B2, the radar device 10 receives reflected wave signals containing Doppler frequency components with different patterns depending on whether the received level of the received signal corresponding to the transmitting antenna in beam direction B1 decreases or whether the received level of the received signal corresponding to the transmitting antenna in beam direction B2 decreases.

[0210] As a result, the radar device 10 can determine, for example, based on the detected Doppler frequency peaks (e.g., the interval between peaks), whether a decrease in the received signal level of the received signal corresponding to the transmitting antenna in beam direction B1 has occurred (e.g., state (c) in Figure 15) or whether a decrease in the received signal level of the received signal corresponding to the transmitting antenna in beam direction B2 has occurred (e.g., state (a) in Figure 15), in the Doppler multiplexing / decomposition unit 211 described later.

[0211] Furthermore, for example, Doppler multiplexed signals transmitted from transmitting antennas Tx#1 and Tx#2 in beam direction B1 are transmitted using Doppler shift intervals that result in unequal Doppler multiplexing. Therefore, for example, if the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the received signal of transmitting antennas Tx#1 and Tx#2 in beam direction B1, the radar device 10 can separate the Doppler multiplexed signal using the existing Doppler multiplexed signal separation operation.

[0212] Similarly, for example, Doppler multiplexed signals transmitted from transmitting antennas Tx#3 and Tx#4 in beam direction B2 are transmitted using Doppler shift intervals that result in unequal spacing Doppler multiplexing. Therefore, for example, if the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the received signal of transmitting antennas Tx#3 and Tx#4 in beam direction B2, the radar device 10 can separate the Doppler multiplexed signal using the existing Doppler multiplexed signal separation operation.

[0213] Through the operation of the Doppler multiplexing / decomposition unit 211, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0214] The above explains Doppler shift setting examples 1 and 2. Below, we will explain different Doppler setting examples.

[0215] <Example 3 of setting the Doppler shift amount> Figure 16 shows the number of transmitting antennas Nt=3, N B1 =2, N B2 An example of setting the pattern for the Doppler shift amount with respect to the transmit Doppler frequency when = 1 is shown. In Figure 16, Tx#1 and Tx#2 are the transmitting antennas in beam direction B1 (for example, the transmitting antennas that form the transmit beam B1), and Tx#3 is the transmitting antenna in beam direction B2 (for example, the transmitting antennas that form the transmit beam B2).

[0216] In the example of setting the Doppler shift amount 3, as shown in Figure 16, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd = 1 / (Tr × (N DM We set δ = 1 / (4Tr) and δ = 1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0217] In the example shown in Figure 16, the first to third Doppler shift units 104 (or Doppler shift units 104-1 to 104-3) may perform the following operations.

[0218] The first Doppler shift unit 104, for example, to apply a Doppler shift amount DOP1 = -1 / (2Tr) to the first transmitting antenna Tx#1, outputs a phase rotation Φ1(m) = 2πDOP1 × (m-1)Tr = -π(m-1) for each transmission period Tr of the chirp signal.

[0219] The second Doppler shift unit 104, for example, to apply a Doppler shift amount DOP2=0 to the second transmitting antenna Tx#2, outputs a phase rotation Φ2(m)=2πDOP2×(m-1)Tr=0 for each transmission period Tr of the chirp signal.

[0220] The third Doppler shift unit 104, for example, to apply a Doppler shift amount DOP3 = -1 / (4Tr) to the third transmitting antenna Tx#3, outputs a phase rotation Φ3(m) = 2πDOP3 × (m-1)Tr = -π(m-1) / 2 for each transmission period Tr of the chirp signal.

[0221] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is defined as the Doppler shift interval "Δfd (n1, n2) It is written as "".

[0222] In Figure 16, the pattern of the intervals between the Doppler shift amounts applied to each transmitting antenna Tx#1 to Tx#3 (Doppler shift interval) is Δfd (1, 3) =Δfd (3, 2) =Δfd, Δfd(2, 1) = 2Δfd. Therefore, in Figure 16, the intervals of the Doppler shift amounts applied to each transmitting antenna with a number of transmitting antennas Nt=3 are not all the same, but include unequal intervals (for example, Δfd (1, 3) =Δfd (3, 2) ≠Δfd (2, 1) This results in unequal-interval Doppler multiplexing (unequal-interval DDM transmission).

[0223] Furthermore, in Figure 16, the Doppler shift interval between transmitting antennas Tx#1 and Tx#2 in beam direction B1 is Δfd (1, 2) =2Δfd, Δfd (2, 1) = 2Δfd. Therefore, the number of transmitting antennas N in beam direction B1. B1 The intervals between the Doppler shift amounts applied to each transmitting antenna in the =2 configuration are all the same, resulting in equal-interval Doppler multiplexing (equal-interval DDM transmission).

[0224] Furthermore, in Figure 16, the number of transmitting antennas in beam direction B2 is N. B2 Since = 1, this is a case where Doppler multiplexing does not occur with a transmitting antenna in beam direction B2.

[0225] Also, in Figure 16, N B1 (=2) ≠ N B2 (=1). For example, in the example shown in Figure 16, the pattern of Doppler shift amount assigned to the transmitting antenna in beam direction B1 is different from the pattern of Doppler shift amount assigned to the transmitting antenna in beam direction B2.

[0226] Therefore, the example shown in Figure 16 is an example of setting a pattern for the amount of Doppler shift that satisfies condition 1 (2) but does not satisfy condition 2.

[0227] For example, when the target direction is beam direction B1 (for example, target direction (1) shown in Figure 13), and when the target direction is beam direction B2 (for example, target direction (3) shown in Figure 13), the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 1(2)) depending on the target direction, similar to setting example 1. Therefore, the radar device 10 can determine, for example, based on the detected Doppler frequency peaks (for example, the number of peaks), whether a decrease in the received level of the received signal corresponding to the transmitting antenna in beam direction B1 or a decrease in the received level of the received signal corresponding to the transmitting antenna in beam direction B2 has occurred, using the Doppler multiplexing / decomposition unit 211 described later.

[0228] Furthermore, for example, Doppler multiplexed signals transmitted from transmitting antennas Tx#1 and Tx#2 in beam direction B1 do not satisfy condition 2 and are transmitted using Doppler shift intervals that result in equally spaced Doppler multiplexing. Therefore, for example, if the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the received signal of the transmitting antenna in beam direction B1, the radar device 10 can separate the Doppler multiplexed signals using the existing Doppler multiplexed signal separation operation. In this case, the radar device 10 can determine the Doppler frequency fd of the target in the range -1 / (4Tr) ≤ fd < 1 / (4Tr) and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0229] Furthermore, for example, the transmitting antenna Tx#3 in beam direction B2 is a single-antenna transmitter. Therefore, for example, if the Doppler multiplexing / decoupling unit 211 determines that the received signal corresponds to the received signal of the transmitting antenna Tx#3 in beam direction B2, the radar device 10 does not need to perform the Doppler multiplexing signal separation process for the received signal in beam direction B2. Through this operation of the Doppler multiplexing / decoupling unit 211, the radar device 10 can determine the Doppler frequency fd of the target in the range -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexing signal.

[0230] <Example 4 of setting the Doppler shift amount> Figure 17 shows the number of transmitting antennas Nt=6, N B1 =3, N B2 An example of setting the pattern of the Doppler shift amount with respect to the transmit Doppler frequency when = 3 is shown. In Figure 17, Tx#1, Tx#2, and Tx#4 are the transmitting antennas in beam direction B1 (for example, transmitting antennas that form the transmit beam B1), and Tx#3, Tx#5, and Tx#6 are the transmitting antennas in beam direction B2 (for example, transmitting antennas that form the transmit beam B2).

[0231] In the example of setting the Doppler shift amount 4, as shown in Figure 17, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd = 1 / (Tr × (N DM We set δ = 2, where +δ) = 1 / (8Tr), but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0232] In the example shown in Figure 17, the first to sixth Doppler shift units 104 (or Doppler shift units 104-1 to 104-6) may perform the following operations.

[0233] The first Doppler shift unit 104 outputs a phase rotation Φ1(m) = -π(m-1) for each transmission period Tr of the chirp signal in order to apply a Doppler shift amount DOP1 = -1 / (2Tr) to the first transmitting antenna Tx#1, for example.

[0234] The second Doppler shift unit 104, for example, to apply a Doppler shift amount DOP2 = -3 / (8Tr) to the second transmitting antenna Tx#2, outputs a phase rotation Φ2(m) = -3π(m-1) / 4 for each transmission period Tr of the chirp signal.

[0235] The third Doppler shift unit 104, for example, to apply a Doppler shift amount DOP3 = -1 / (4Tr) to the third transmitting antenna Tx#3, outputs a phase rotation Φ3(m) = -π(m-1) / 2 for each transmission period Tr of the chirp signal.

[0236] The fourth Doppler shift unit 104, for example, to apply a Doppler shift amount DOP4 = -1 / (8Tr) to the fourth transmitting antenna Tx#4, outputs a phase rotation Φ4(m) = -π(m-1) / 4 for each transmission period Tr of the chirp signal.

[0237] The fifth Doppler shift unit 104 outputs a phase rotation Φ5(m)=0 for each transmission period Tr of the chirp signal in order to apply a Doppler shift amount DOP5=0 to the fifth transmitting antenna Tx#5, for example.

[0238] The sixth Doppler shift unit 104, for example, applies a Doppler shift amount DOP6 = 1 / (8Tr) to the sixth transmitting antenna Tx#6 by applying a phase rotation Φ6(m) = π(m-1) / 4 for each transmission period Tr of the chirp signal and outputting it.

[0239] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is defined as the Doppler shift interval "Δfd (n1, n2) It is written as "".

[0240] In Figure 17, the pattern of the intervals between the Doppler shift amounts applied to each transmitting antenna Tx#1 to Tx#6 (Doppler shift interval) is Δfd (1, 2) =Δfd (2, 3) =Δfd (3, 4) =Δfd (4, 5) =Δfd (5, 6) =Δfd, Δfd (6, 1) = 3Δfd. Therefore, in Figure 17, the intervals of the Doppler shift amounts applied to each transmitting antenna with a 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) This results in unequal-interval Doppler multiplexing (unequal-interval DDM transmission).

[0241] Furthermore, in Figure 17, the interval of Doppler shift between the transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1 is Δfd (1, 2) =Δfd, Δfd (2, 4) =2Δfd, Δfd (4, 1) = 5Δfd. Therefore, the number of transmitting antennas in beam direction B1 is N. B1 The intervals of the Doppler shift amounts applied to each transmitting antenna in =3 are not all the same, but include unequal intervals (Δfd (1, 2) ≠Δfd (2, 4) =Δfd (4, 1) ), this will be unequal-spacing Doppler multiplexing (unequal-spacing DDM transmission) using a transmitting antenna in beam direction B1.

[0242] Furthermore, in Figure 17, the interval of Doppler shift between the transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2 is Δfd (3, 5) =2Δfd, Δfd (5, 6) =Δfd, Δfd (6, 3) = 5Δfd. Therefore, the number of transmitting antennas in beam direction B2 is N. B2 The intervals of the Doppler shift amounts applied to each transmitting antenna in =3 are not all the same, but include unequal intervals (Δfd (3, 5) ≠Δfd (5, 6) ≠Δfd (6, 3) ), this will be unequal-spacing Doppler multiplexing (unequal-spacing DDM transmission) using a transmitting antenna with beam direction B2.

[0243] Based on the above, the example shown in Figure 17 is an example of setting a pattern for the Doppler shift amount that satisfies condition 2.

[0244] Furthermore, in Figure 17, the Doppler shift between transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1 is Δfd (1, 2) =Δfd, Δfd (2, 4) =2Δfd, Δfd(4, 1) = 5Δfd, and the Doppler shift between transmitting antennas Tx#3, Tx#5 and Tx#6 in beam direction B2 is Δfd (3, 5) =2Δfd, Δfd (5, 6) =Δfd, Δfd (6, 3) = 5Δfd. Thus, in Figure 17, the Doppler multiplexing number N is determined by the transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1. B1 And the Doppler multiplexing number N is achieved by transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2. B2 These are the same. Also, in Figure 17, the Doppler shift amounts between transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1, and the Doppler shift amounts between transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2 include the same combination of Doppler shift intervals, but the order of the Doppler shift intervals between beam direction B1 and beam direction B2 on the Doppler frequency axis is different.

[0245] For example, in Figure 17, the order of the intervals for the Doppler shift amounts assigned to the transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1 is Δfd, 2Δfd, and 5Δfd. Also in Figure 17, the order of the intervals for the Doppler shift amounts assigned to the transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2 is 2Δfd, Δfd, and 5Δfd. Therefore, Figure 17 includes the same combination of Doppler shift intervals (e.g., Δfd, 2Δfd, 5Δfd) for the transmitting antennas in beam direction B1 and beam direction B2, but the order of these intervals differs between beam directions. For example, in Figure 17, even if the Doppler shift interval between transmitting antennas in beam direction B1, or the Doppler shift interval between transmitting antennas in beam direction B2, is cyclically shifted on the Doppler frequency axis, the amount of Doppler shift will not match between different beam directions.

[0246] Thus, in the example shown in Figure 17, the patterns of Doppler shift amounts assigned to transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1 are different from the patterns of Doppler shift amounts assigned to transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2.

[0247] Based on the above, the example shown in Figure 17 is an example of setting a pattern for the Doppler shift amount that satisfies condition 1 (3).

[0248] The following describes an example of a received signal at the output of the Doppler analysis unit 209 when the transmitting antenna unit 105 includes transmitting antennas with different beam directions B1 and B2 based on the Doppler shift amount setting shown in Figure 17, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with substantially uniform directional characteristics within the field of view covered by both transmitting antennas in beam direction B1 and beam direction B2).

[0249] Furthermore, in Example 4, we will describe an example of a multi-beam transmitting MIMO radar (for example, radar device 10) that forms transmitting beams with beam directions B1 (Tx Beam #1) and B2 (Tx Beam #2) similar to those in Figure 13.

[0250] For example, when the target direction is target direction (1) as shown in Figure 13 (for example, when a target exists around beam direction B1), the radiation direction of the radar transmitted waves sent from Tx#1, Tx#2, and Tx#4 in beam direction B1 coincides with the target direction. Therefore, the reception level of the received signals of the reflected waves from the target corresponding to Tx#1, Tx#2, and Tx#4 in the radar device 10 is relatively high. On the other hand, when the target direction is target direction (1) as shown in Figure 13, the radiation direction of the radar transmitted waves sent from Tx#3, Tx#5, and Tx#6 in beam direction B2 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmitting beam B2. Therefore, the reception level of the received signals of the reflected waves from the target corresponding to Tx#3, Tx#5, and Tx#6 in the radar device 10 is lower than the reception level of the received signals corresponding to Tx#1, Tx#2, and Tx#4. For example, the received signal levels corresponding to Tx#3, Tx#5, and Tx#6 differ significantly from those corresponding to Tx#1, Tx#2, and Tx#4, and can be, for example, 10 dB or more lower, depending on the null-direction beam directivity characteristics of Tx#3, Tx#5, and Tx#6.

[0251] Furthermore, for example, if the target direction is the target direction (3) shown in Figure 13 (for example, if a target exists around beam direction B2), the radiation direction of the radar transmitted waves sent from Tx#3, Tx#5, and Tx#6 in beam direction B2 coincides with the target direction. Therefore, the reception level of the received signals of the reflected waves from the target corresponding to Tx#3, Tx#5, and Tx#6 in the radar device 10 is relatively high. On the other hand, if the target direction is the target direction (3) shown in Figure 13, the radiation direction of the radar transmitted waves sent from Tx#1, Tx#2, and Tx#4 in beam direction B1 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmitting beam B1. Therefore, the reception level of the received signals corresponding to Tx#1, Tx#2, and Tx#4 in the radar device 10 is lower than the reception level of the received signals of the reflected waves from the target corresponding to Tx#3, Tx#5, and Tx#6. For example, the received signal levels corresponding to Tx#1, Tx#2, and Tx#4 differ significantly from those corresponding to Tx#3, Tx#5, and Tx#6, and can be, for example, 10 dB or more lower, depending on the null-direction beam directivity characteristics of Tx#1, Tx#2, and Tx#4.

[0252] Thus, when the target direction is beam direction B1 (target direction (1) shown in Figure 13), and when the target direction is beam direction B2 (target direction (3) shown in Figure 13), the radar device 10 receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 1(3)) depending on the target direction. Therefore, when the target direction is beam direction B1 or B2, the radar device 10 receives reflected wave signals containing Doppler frequency components with different patterns depending on whether the received level of the received signal corresponding to the transmitting antenna in beam direction B1 decreases or whether the received level of the received signal corresponding to the transmitting antenna in beam direction B2 decreases.

[0253] As a result, the radar device 10 can determine, for example, based on the detected Doppler frequency peaks (for example, the order of the peak intervals), whether a decrease in the received signal level of the received signal corresponding to the transmitting antenna in beam direction B1 or a decrease in the received signal level of the transmitting antenna in beam direction B2, using the Doppler multiplexing / decomposition unit 211 described later.

[0254] Furthermore, for example, Doppler multiplexed signals transmitted from transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1 are transmitted using Doppler shift intervals that result in unequal Doppler multiplexing. Therefore, for example, if the Doppler multiplexing / determination unit 211 determines that the received signal corresponds to the received signal of transmitting antennas Tx#1, Tx#2, and Tx#4 in beam direction B1, the radar device 10 can separate the Doppler multiplexed signals using the existing Doppler multiplexed signal separation operation.

[0255] Similarly, for example, Doppler multiplexed signals transmitted from transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2 are transmitted using Doppler shift intervals that result in unequal Doppler multiplexing. Therefore, for example, if the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the received signal of transmitting antennas Tx#3, Tx#5, and Tx#6 in beam direction B2, the radar device 10 can separate the Doppler multiplexed signals using the existing Doppler multiplexed signal separation operation.

[0256] On the other hand, for example, if the target direction is an intermediate direction between beam direction B1 and beam direction B2, and the target direction is an area direction where the beam widths of both beams overlap by approximately 3 dB or 6 dB (for example, target direction (2) shown in Figure 13), then the received signal levels corresponding to Tx#1, Tx#2, and Tx#4 in beam direction B1 are about the same as the received signal levels corresponding to Tx#3, Tx#5, and Tx#6 in beam direction B2. Therefore, when the target direction is an intermediate direction between beam direction B1 and beam direction B2 (target direction (2) shown in Figure 13), the radar device 10 receives the received signals corresponding to the transmitting antennas in each beam direction at approximately the same received level. Consequently, the signals transmitted from Nt transmitting antennas, including the respective transmitting antennas for beam direction B1 and beam direction B2, are Doppler multiplexed using Doppler shift intervals that result in unequal Doppler multiplexing. Therefore, the radar device 10 can separate Doppler multiplexed signals based on the existing Doppler multiplexed signal separation operation.

[0257] Through the operation of the Doppler multiplexing / decomposition unit 211, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0258] The above explains an example of setting the Doppler shift amount.

[0259] Note that the setting of the Doppler shift amount is not limited to the setting examples 1 to 4 described above. For example, the number of transmitting antennas Nt (or Doppler multiplexing number), the number of transmitting antennas in beam direction B1 N B1 Number of transmitting antennas in beam direction B2: N B2 And at least one of the Doppler shift intervals may be any other value.

[0260] Furthermore, in the Doppler shift unit 104, the Doppler shift amount DOP is set for the radar transmission signal transmitted from Nt transmitting antennas. n The phase rotation Φ that imparts n(m) can be expressed as in equation (4) below.

number

[0261] Here, Φ0 is the initial phase and ΔΦ0 is the reference Doppler shift phase.

[0262] For example, when performing Doppler multiplexing using three transmitting antennas (Nt=3), the first Doppler 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 for each transmission period Tr, as shown in equation (5). The output of the first Doppler shift unit 104 is, for example, output from the first transmitting antenna (Tx#1). Here, cp(t) represents the chirp signal for each transmission period.

number

[0263] Furthermore, for example, the second Doppler shift unit 104 applies a phase rotation Φ2(m) to the radar transmission signal (e.g., chirp signal) input from the radar transmission signal generation unit 101 for each transmission period Tr, as shown in equation (6). The output of the second Doppler shift unit 104 is output from, for example, the second transmitting antenna (Tx#2).

number

[0264] Similarly, for example, the third Doppler shift unit 104 applies a phase rotation Φ3(m) to the radar transmission signal (e.g., chirp signal) input from the radar transmission signal generation unit 101 for each transmission period Tr, as shown in equation (7). The output of the third Doppler shift unit 104 is output from, for example, the third transmitting antenna (Tx#3).

number

[0265] The above described the setting example of the Doppler shift amount.

[0266] Next, an operation example of the CFAR unit 210 and the Doppler multiplex separation unit 211 corresponding to the operation of the Doppler shift unit 104 described above will be described.

[0267] [Operation example of CFAR unit 210] For example, the CFAR unit 210 may perform the operation of operation example 1 or operation example 2 below in order to receive the reflected wave signal with respect to the radar transmission signal from the radar transmission unit 100.

[0268] 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 are omnidirectional antennas (or antennas having substantially uniform directivity characteristics within the viewing angle covered by the transmitting antennas in a plurality of different beam directions) will be described.

[0269] <Operation example 1 of CFAR unit 210> In operation example 1, an operation example of the CFAR unit 210 when the value of δ shown in Equation (3) is set to a positive integer in the Doppler shift unit 104 will be described.

[0270] In this case, the interval between the Doppler shift amounts assigned to the Doppler multiplex signals uses the interval of Δfd or an integer multiple of the interval of Δfd. Therefore, each signal to be Doppler multiplexed can be detected as being folded at the interval of Δfd in the output of the Doppler frequency region of the Doppler analysis unit 209. Utilizing such a property, for example, the operation of the CFAR unit 210 can be simplified as follows.

[0271] The CFAR unit 210 detects a Doppler peak, for example, using a threshold value with respect to the power addition value obtained by adding the received powers of the reflected wave signals for each range (for example, the range of Δfd) that is a unit of each interval of the Doppler shift amount respectively given to the radar transmission signals within the Doppler frequency range of the output of the Doppler analysis unit 209 to be subjected to CFAR processing.

[0272] For example, the CFAR unit 210 analyzes the output of the Doppler analysis unit 209 of the 1st to Nath signal processing units 206 at intervals of Δfd (e.g., N) as shown in equation (8). Δfd (corresponding to) the power value shown in equation (9), PowerqFT(f b , f s The power sum value obtained by adding ) PowerDDM(f b , f sddm ) is calculated and CFAR processing is performed.

number

number

[0273] Here, f sddm =-N c / 2,~,-N c / 2+N Δfd -1, N Δfd This represents the number of Doppler frequency indices included in the interval of Δfd, and N Δfd = round(Δfd / (1 / (T r N c )) Also, round(x) is an operator that rounds a real number x to the nearest integer and outputs an integer value.

[0274] The operation of the CFAR processing may be based on the operation disclosed in Non-Patent Document 2, for example, and a detailed explanation of the operation example will be omitted.

[0275] This allows the Doppler frequency range to be processed in the CFAR unit 210 to be the entire Doppler frequency index range f s (For example, -N c / 2~N c Since the range can be narrowed from (2-1) to the range of Δfd, the computational complexity of CFAR processing can be reduced to 1 / (Nt+δ)=1 / (N DM It can be reduced to +δ).

[0276] Then, the CFAR unit 210 adaptively sets a threshold value, for example, and outputs a distance index f at which the received power is greater than the threshold value 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 multiplex separation unit 211. Here, ndm = 1 to N DM is an integer of +δ.

[0277] <Example operation 2 of the CFAR unit 210> In Example operation 2, an example operation of the CFAR unit 210 when the value of δ shown in Equation (3) is set to a non-integer real value in the Doppler shift unit 104 will be described.

[0278] The CFAR unit 210 may calculate, for example, the power addition value of Equation (9) based on the outputs of the Doppler analysis units 209 of the first to Na-th signal processing units 206, and detect a power peak that matches the Doppler shift interval set for the radar transmission signal for each distance index by an adaptive threshold processing (CFAR processing).

[0279] Then, the CFAR unit 210 adaptively sets a threshold value, for example, and a distance index f at which the received power is greater than the threshold value b_cfar , the Doppler frequency index f at the power peak that matches the Doppler shift interval set for the radar transmission signal s_cfar (ndm), and the received power information PowerFT(f s_cfar (ndm)) of the Doppler frequency index f b_cfar , f s_cfar (ndm)) to the Doppler multiplex separation unit 211. Here, ndm = 1 to N DM is an integer of +δ.

[0280] The example operations of the CFAR unit 210 have been described above.

[0281] In the operation example of the Doppler multiplexing unit 211 described later, the case using the output from operation example 1 of the CFAR unit 210 will be explained as an example, but it is not limited to this, and the output from operation example 2 of the CFAR unit 210 may also be used. When using the output from operation example 2 of the CFAR unit 210, the Doppler frequency index f in operation example 1 of the CFAR unit 210 will be used. sddm_cfar +(ndm-1)×N Δfd Instead, Doppler frequency index f s_cfar The only difference is that it outputs (ndm), but otherwise it behaves the same and produces the same effect.

[0282] [Example of operation of the Doppler multiplexing unit 211] The Doppler multiplexing / separation unit 211 receives the distance index f input from the CFAR unit 210 when, for example, the value of δ shown in equation (3) is set to a positive integer in the Doppler shift unit 104. b_cfar , Doppler frequency index f sddm_cfar , and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd Based on ), the following actions are performed. However, ndm = 1 to N DM It is an integer of +δ.

[0283] The following description will explain an example of the operation of the Doppler multiplexing / decoupling unit 211 when the multiple receiving antennas of the receiving antenna unit 202 are omnidirectional antennas (or antennas having substantially uniform directional characteristics within the field of view covered by the transmitting antennas in beam direction B1 and beam direction B2). An example of the operation of the Doppler multiplexing / decoupling unit 211 when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas in different beam directions will be described later.

[0284] Figure 18 is a flowchart illustrating an example of the separation operation of Doppler multiplexed signals in the Doppler multiplexing / decoupling unit 211. In the following, it is assumed that the Doppler velocity of the target is within the range of -1 / (2Tr) ≤ fd < 1 / (2Tr).

[0285] <Step A-1> The Doppler multiplexing unit 211 has Nt units (=N DM Performs Doppler multiplexing and demultiplexing on individual Doppler multiplexed signals.

[0286] <Step A-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indices (f sddm_cfar +(ndm-1)×N Δfd ) to, N DM It is assumed that the signal will contain Doppler multiplexed signals with unequal intervals.

[0287] The Doppler multiplexing unit 211, for example, uses 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~N DM Compare the integers (+δ) and select the top N of the received power. DM The number of Doppler frequency indices (f sddm_cfar +(ndm-1)×N Δfd ) determines whether it matches the Doppler shift interval assigned at the time of transmission (for example, "N DM This is called "individual Doppler shift interval matching determination."

[0288] Furthermore, the Doppler multiplexing and separation unit 211, for example, the upper N of the received power DM The received level of each Doppler frequency index and the top N received powers DM It determines whether the difference (or received level ratio) between the received levels of one Doppler frequency index and δ other different Doppler frequency indices is significantly different (for example, whether the difference is greater than or equal to a threshold, or whether the received level ratio is greater than or equal to a threshold) (for example, "N DM This is called "individual Doppler multiplexed signal reception level difference determination."

[0289] The Doppler multiplexing / decompression unit 211 determines, for example, the Doppler frequency and transmitting antenna corresponding to the Doppler multiplexed signal in the range -1 / (2Tr) ≤ fd < 1 / (2Tr) based on these determinations.

[0290] An example of the operation of the Doppler multiplexing separation unit 211, which separates Doppler multiplexed signals at unequal intervals, is disclosed in, for example, Patent Document 7, so a detailed explanation of its operation will be omitted here.

[0291] For example, the Doppler multiplexing unit 211 is N DM Individual Doppler shift interval matching determination, and N DM Determine whether both conditions for determining the difference in reception levels of individual Doppler multiplexed signals (for example, the conditions in step A-2) are met. For example, N DM In determining the matching of individual Doppler shift intervals, the top N of the received power DM The number of Doppler frequency indices (f sddm_cfar +(ndm-1)×N Δfd ) is determined to match the Doppler shift interval assigned at the time of transmission, and N DM In the individual Doppler multiplexed signal reception level difference determination, if the relevant reception level difference is determined to be above the threshold, the conditions of step A-2 are met.

[0292] The Doppler multiplexing unit 211 may perform the process in step A-3 if the conditions in step A-2 are met, and if the conditions in step A-2 are not met, it may perform the process in step B-1, assuming that the target direction is the beam direction B1.

[0293] <Step A-3> The Doppler multiplexing unit 211, for example, uses the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) of which, δ Doppler frequency indices with low received levels and the top N with high received power DM Based on the relationship with the individual Doppler frequency indices, the Doppler shift amounts of the Nt Doppler multiplexed signals to be transmitted are DOP1, DOP2, ~, DOPNt Then, the Doppler frequency index is associated with the Doppler multiplexed signal separation index information DDM_RXindex(f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as distance index f b_cfar It also outputs to the direction estimation unit 212.

[0294] Here, f demul_Tx#n This indicates the Doppler frequency index of the reflected signal for the radar transmission signal transmitted from the nth transmitting antenna (Tx#n).

[0295] Furthermore, the Doppler multiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indices to the direction estimation unit 212.

[0296] Furthermore, the amount of Doppler shift applied to each transmitting antenna of the transmitting antenna unit 105 in the Doppler shift unit 104 of the radar transmitting unit 100 is known. Therefore, the separation index information of the Doppler multiplexed signal DDM_RXindex(f b_cfar The difference between the Doppler frequency indicated by ) and the Doppler shift amount applied to each transmitting antenna in the radar transmitting unit 100 becomes the Doppler frequency of the target. Therefore, the Doppler multiplexing and separation unit 211 uses, for example, the separation index information DDM_RXindex(f b_cfar Instead of ), the Doppler frequency of the target estimated in the range -1 / (2Tr) ≤ fd < 1 / (2Tr) may be output to the direction estimation unit 212. In this case, the direction estimation unit 212 outputs the separation index information DDM_RXindex(f) of the Doppler multiplexed signal based on the Doppler frequency of the target input from the Doppler multiplexing / separation unit 211 and the amount of Doppler shift applied to each transmitting antenna in the Doppler shifting unit 104 of the radar transmitting unit 100. b_cfar By generating ), similar operation becomes possible.

[0297] <Step B-1> The Doppler multiplexing unit 211 assumes that the target direction is the beam direction B1, and N B1 Doppler multiplexing is performed on each Doppler multiplexed signal.

[0298] <Step B-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indices (f sddm_cfar +(ndm-1)×N Δfd ) from the transmitting antenna in beam direction B1 N B1 It is assumed that this contains multiple Doppler multiplexed signals.

[0299] The Doppler multiplexing unit 211, for example, uses 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~N DM Compare the integers (+δ) and select the top N of the received power. B1 Individual Doppler frequency index f sddm_cfar +(ndm-1)×N Δfd ) determines whether it matches the Doppler shift interval applied to the transmitting antenna in beam direction B1 during transmission (for example, this is called "beam direction B1 Doppler shift interval matching determination").

[0300] Furthermore, the Doppler multiplexing and separation unit 211, for example, the upper N of the received power B1 The number of Doppler frequency indices and the top N of the received power B1 The number of Doppler frequency indices is different (N DM +δ-N B1 It is determined whether the difference (or received level ratio) between the received level of one Doppler frequency index and that of the other Doppler frequency indices is significantly different (for example, whether the difference is greater than or equal to a threshold, or whether the received level ratio is greater than or equal to a threshold) (for example, this is called "beam direction B1 Doppler multiplexed signal received level difference determination").

[0301] The Doppler multiplexing / decompression unit 211 determines, for example, the Doppler frequency and transmitting antenna corresponding to the Doppler multiplexed signal in the range -1 / (2Tr) ≤ fd < 1 / (2Tr) based on these determinations.

[0302] An example of the operation of the Doppler multiplexing separation unit 211, which separates Doppler multiplexed signals at unequal intervals, is disclosed in, for example, Patent Document 7, so a detailed explanation of its operation will be omitted here.

[0303] For example, the Doppler multiplexing / determination unit 211 determines whether both conditions (for example, the conditions in step B-2) are met: the beam direction B1 Doppler shift interval matching determination and the beam direction B1 Doppler multiplexed signal reception level difference determination. For example, in the beam direction B1 Doppler shift interval matching determination, the top N of the received power B1 The number of Doppler frequency indices (f sddm_cfar +(ndm-1)×N Δfd If it is determined that ) matches the Doppler shift interval applied to the transmitting antenna in beam direction B1 during transmission, and if the corresponding received level difference is determined to be greater than or equal to the threshold in the beam direction B1 Doppler multiplexed signal received level difference determination, then the conditions of step B-2 are met.

[0304] The Doppler multiplexing unit 211 may perform the process in step B-3 if the conditions in step B-2 are met, and if the conditions in step B-2 are not met, it may perform the process in step C-1, assuming that the target direction is the beam direction B2.

[0305] Note N B1 If the number of items is 1, the beam direction B1 Doppler shift interval matching determination process does not need to be performed.

[0306] <Step B-3> The Doppler multiplexing unit 211, for example, uses the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) Among them, N with the smallest received level DM +δ-NB1 The Doppler frequency index of each individual and the top N with high received power B1 Based on the relationship with the individual Doppler frequency indices, the Doppler shift amounts of the Nt Doppler multiplexed signals to be transmitted are DOP1, DOP2, ~, DOP Nt This is then associated with the Doppler frequency index, and the Doppler multiplexed signal separation index information DDM_RXindex_ B1 (f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as distance index f b_cfar It also outputs to the direction estimation unit 212.

[0307] Here, f demul_Tx#n This indicates the Doppler frequency index of the reflected signal for the radar transmission signal transmitted from the nth transmitting antenna (Tx#n).

[0308] Furthermore, the Doppler multiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indices to the direction estimation unit 212.

[0309] Furthermore, the amount of Doppler shift applied to each transmitting antenna of the transmitting antenna unit 105 in the Doppler shift unit 104 of the radar transmitting unit 100 is known. Therefore, the separation index information of the Doppler multiplexed signal DDM_RXindex_ B1 (f b_cfar The difference between the Doppler frequency indicated by ) and the Doppler shift amount applied to each transmitting antenna in the radar transmitting unit 100 becomes the Doppler frequency of the target. Therefore, the Doppler multiplexing and separation unit 211, for example, the separation index information DDM_RXindex_ B1 (f b_cfarInstead of ), the Doppler frequency of the target estimated in the range -1 / (2Tr) ≤ fd < 1 / (2Tr) may be output to the direction estimation unit 212. In this case, the direction estimation unit 212 outputs the separation index information DDM_RXindex_ of the Doppler multiplexed signal based on the Doppler frequency of the target input from the Doppler multiplexing / separation unit 211 and the amount of Doppler shift applied to each transmitting antenna in the Doppler shifting unit 104 of the radar transmitting unit 100. B1 (f b_cfar By generating ), similar operation becomes possible.

[0310] Alternatively, the Doppler multiplexing unit 211 selects N of the Nt transmitting antennas in the beam direction B1. B1 The Doppler shift amount of the Doppler multiplexed signal from each transmitting antenna is associated with the Doppler frequency index, and the beam direction B1 separation index information of the Doppler multiplexed signal is determined using DDM_Rxindex_ B1 (f b_cfar ) as distance index f b_cfar It may also be output to the direction estimation unit 212.

[0311] <Step C-1> The Doppler multiplexing unit 211 assumes that the target direction is the beam direction B2, and N B2 Doppler multiplexing is performed on each Doppler multiplexed signal.

[0312] <Step C-2> In this case, for example, the distance index f input from the CFAR unit 210 b_cfar N in DM +δ Doppler frequency indices (f sddm_cfar +(ndm-1)×N Δfd ) from the transmitting antenna in beam direction B2 N B2 It is assumed that this contains multiple Doppler multiplexed signals.

[0313] The Doppler multiplexing unit 211, for example, uses 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~N DM Compare the integers (+δ) and select the top N of the received power. B2 Individual Doppler frequency index f sddm_cfar +(ndm-1)×N Δfd ) determines whether it matches the Doppler shift interval applied to the transmitting antenna in beam direction B2 during transmission (for example, this is called "beam direction B2 Doppler shift interval matching determination").

[0314] Furthermore, the Doppler multiplexing and separation unit 211, for example, the upper N of the received power B2 The number of Doppler frequency indices and the top N of the received power B2 The number of Doppler frequency indices is different (N DM +δ-N B2 It is determined whether the difference (or received level ratio) between the received level of one other Doppler frequency index and the other one is significantly different (for example, whether the difference is greater than or equal to a threshold, or whether the received level ratio is greater than or equal to a threshold) (for example, this is called "beam direction B2 Doppler multiplexed signal received level difference determination").

[0315] The Doppler multiplexing / decoupling unit 211 determines, for example, the Doppler frequency and transmitting antenna in the range -1 / (2Tr) ≤ fd < 1 / (2Tr) based on these determinations.

[0316] An example of the operation of the Doppler multiplexing separation unit 211, which separates Doppler multiplexed signals at unequal intervals, is disclosed in, for example, Patent Document 7, so a detailed explanation of its operation will be omitted here.

[0317] For example, the Doppler multiplexing / detachment unit 211 determines whether both conditions (for example, the conditions in step C-2) are met: the beam direction B2 Doppler shift interval matching determination and the beam direction B2 Doppler multiplexed signal reception level difference determination. For example, in the beam direction B2 Doppler shift interval matching determination, the top N of the received power B2 The number of Doppler frequency indices (fsddm_cfar +(ndm-1)×N Δfd If it is determined that ) matches the Doppler shift interval applied to the transmitting antenna in beam direction B2 during transmission, and if the corresponding received level difference is determined to be greater than or equal to the threshold in the beam direction B2 Doppler multiplexed signal received level difference determination, then the conditions of step C-2 are met.

[0318] The Doppler multiplexing / decoupling unit 211 may perform the processing in step C-3 if the conditions in step C-2 are met. Alternatively, if the conditions in step C-2 are not met, the Doppler multiplexing / decoupling unit 211 may determine that the received signal is a noise component or an interference component and may not output to the direction estimation unit 212 (step D).

[0319] Note N B2 If the number of items is 1, the beam direction B2 Doppler shift interval matching determination process does not need to be performed.

[0320] <Step C-3> The Doppler multiplexing unit 211, for example, uses the Doppler frequency index (f sddm_cfar +(ndm-1)×N Δfd ) Among them, N with the smallest received level DM +δ-N B2 The Doppler frequency index of each individual and the top N with high received power B2 Based on the relationship with the individual Doppler frequency indices, the Doppler shift amounts of the Nt Doppler multiplexed signals to be transmitted are DOP1, DOP2, ~, DOP Nt This is then associated with the Doppler frequency index, and the Doppler multiplexed signal separation index information DDM_Rxindex_ B2 (f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM ) as distance index f b_cfar It also outputs to the direction estimation unit 212.

[0321] Here, f demul_Tx#n This indicates the Doppler frequency index of the reflected signal for the radar transmission signal transmitted from the nth transmitting antenna (Tx#n).

[0322] Furthermore, the Doppler multiplexing unit 211 outputs the output of the Doppler analysis unit 209 corresponding to these distances and Doppler separation indices to the direction estimation unit 212.

[0323] Furthermore, the amount of Doppler shift applied to each transmitting antenna of the transmitting antenna unit 105 in the Doppler shift unit 104 of the radar transmitting unit 100 is known. Therefore, the separation index information of the Doppler multiplexed signal DDM_RXindex_ B2 (f b_cfar The difference between the Doppler frequency indicated by ) and the amount of Doppler shift applied to each transmitting antenna in the radar transmitting unit 100 becomes the Doppler frequency of the target. Therefore, the Doppler multiplexing and separation unit 211, for example, the separation index information DDM_RXindex_ B2 (f b_cfar Instead of ), the Doppler frequency of the target estimated in the range -1 / (2Tr) ≤ fd < 1 / (2Tr) may be output to the direction estimation unit 212. In this case, the direction estimation unit 212 outputs the separation index information DDM_RXindex_ of the Doppler multiplexed signal based on the Doppler frequency of the target input from the Doppler multiplexing / separation unit 211 and the amount of Doppler shift applied to each transmitting antenna in the Doppler shifting unit 104 of the radar transmitting unit 100. B2 (f b_cfar By generating ), similar operation becomes possible.

[0324] Furthermore, the Doppler multiplexing unit 211 has Nt transmitting antennas, and the beam direction B2 is N B2 The Doppler shift amount of the Doppler multiplexed signal from each transmitting antenna is associated with the Doppler frequency index, and the beam direction B2 separation index information of the Doppler multiplexed signal is determined using DDM_Rxindex_ B2 (f b_cfar ) as distance index f b_cfar It may also be output to the direction estimation unit 212.

[0325] The above describes an example of the operation of the Doppler multiplexing unit 211.

[0326] 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 If there are multiple )), the Doppler multiplexing / decomposition unit 211 may perform the above-described Doppler multiplexing / decomposition operation multiple times for each distance index, Doppler frequency index, and received power information.

[0327] Furthermore, although the above-described example of operation of the Doppler multiplexing / decoupling unit 211 explained the case where the number of multi-beams NB = 2, the number of multi-beams NB is not limited to this, and for example, NB may be 3 or more. For example, in the case where the number of multi-beams NB = 3, the Doppler multiplexing / decoupling unit 211 may continue to perform Doppler multiplexing / decoupling processing for beam directions different from beam directions B1 and B2 (or overlapping beam range or different beams; for example, beam direction B3) in step D of Figure 18 (or between step C-2 and step D). This makes it possible to perform similar Doppler multiplexing / decoupling operations even when the number of multi-beams increases further.

[0328] [Example of operation of the direction estimation unit 212] Next, we will explain an example of the operation of the direction estimation unit 212 shown in Figure 7.

[0329] In the following description, we will explain an example of the operation of the direction estimation unit 212 when the multiple receiving antennas of the receiving antenna unit 202 are identical omnidirectional antennas or antennas with substantially uniform directional characteristics within the field of view of multiple transmitting antennas with different beam directions.

[0330] The direction estimation unit 212 receives information input from, for example, the Doppler multiplexing unit 211 (for example, distance index f b_cfar , Doppler multiplexed signal separation index information (DDM_Rxindex(f b_cfar )=(f demul_Tx#1, f demul_Tx#2 ,~,f demul_Tx#Nt ) or DDM_Rxindex_ Bq (f b_cfar Based on these distances and the output of the Doppler analysis unit 209 corresponding to the Doppler separation index, the direction estimation process of the target is performed. Here, for example, q = 1 or 2.

[0331] The following describes two examples of the operation of the direction estimation unit 212.

[0332] <Example of operation of direction estimation unit 212 1> For example, the direction estimation unit 212 uses the distance index f b_cfar and Doppler multiplexed signal separation index information DDM_Rxindex(f b_cfar Based on this, the output of the Doppler analysis unit 209 is extracted, and the virtual received array correlation vector h(f) of the direction estimation unit 212 is obtained as shown in equation (10) below. b_cfar , DDM_Rxindex(f b_cfar Generate )) and perform direction estimation processing.

[0333] Here, the information input from the Doppler multiplexing / decoupling unit 211 is the Doppler multiplexed signal separation index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt If it includes ), it includes Doppler separation information for Nt transmitting antennas. Therefore, the virtual received array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar The )) contains Nt × Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na, as shown in equation (10). The direction estimation unit 212 calculates the virtual received array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar Using this method, direction estimation is performed on the reflected wave signal from the target based on the phase difference between each transmitting and receiving antenna.

number

[0334] In equation (10), h cal[b] This is an array correction value that corrects the phase deviation and amplitude deviation between transmitting and receiving antennas. b is an integer between 1 and (Nt × Na).

[0335] The direction estimation unit 212, for example, calculates the virtual received array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar Using )), the direction estimation evaluation function P H (θ u , f b_cfar , DDM_Rxindex(f b_cfar )) azimuthal direction θ u The spatial profile is calculated by varying the angle within a predetermined range.

[0336] The direction estimation unit 212 may extract a predetermined number of maximum peaks from the calculated spatial profile in descending order, and output the azimuth direction of the maximum peaks as an estimated direction of arrival (for example, a positioning output).

[0337] Note that the direction estimation evaluation function value P H (θ u , f b_cfar , DDM_Rxindex(f b_cfar There are various methods for estimating the direction of arrival, depending on the direction of arrival algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0338] For example, if the number of virtual receiving antennas is Nt × Na and they are arranged in a straight line at equal intervals dH, the beamformer method can be expressed as shown in equation (11). In addition to the beamformer method, other methods such as Capon and MUSIC can also be applied in a similar manner.

number

[0339] In equation (11), the superscript H is the Hermitian transpose operator. Also, in equation (11), a(θu ) is the azimuth direction θ at the center frequency fc of the radar transmission signal. u This shows the direction vector of the virtual receiving array for the incoming wave, and is a column vector with Nt × Na elements, as expressed in equation (12). In equation (12), λ is the center frequency f c In this case, the wavelength of the radar transmission signal (e.g., chirp signal) is λ = C0 / f c That is the case.

number

[0340] Also, the azimuth direction θ u This is a vector obtained by changing the azimuth range used for estimating the direction of arrival by a predetermined azimuth interval β1. For example, θ u It will be set as follows: θ u =θ min + uβ1, integer u=0~ NU NU = floor[(θmax-θmin) / β1]+1 Here, floor(x) is a function that returns the largest integer value not exceeding the real number x.

[0341] Furthermore, while the above example described an example in which the direction estimation unit 212 calculates the azimuth direction as the estimated direction of arrival, it is not limited to this. It is also possible to estimate the direction of arrival in the elevation direction by using virtual receiving antennas arranged in the elevation direction, or to estimate the direction of arrival in both the azimuth and elevation directions by using virtual receiving antennas arranged in the azimuth and elevation directions, such as in a rectangular grid. For example, the direction estimation unit 212 may calculate the azimuth and elevation directions as estimated directions of arrival for each transmitting antenna with a different beam direction and output them as positioning output.

[0342] Through the above operations, the direction estimation unit 212 of the radar device 10 outputs, for example, the distance index f b_cfar , Doppler multiplexed signal separation index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDMThe direction estimation unit 212 may output an estimated direction of arrival value in ). Furthermore, the direction estimation unit 212 may output a distance index f as a positioning output. b_cfar , and the separation index information of Doppler multiplexed signals DDM_Rxindex(f b_cfar You may output ).

[0343] Furthermore, the direction estimation unit 212 uses, for example, the separation index information of the Doppler multiplexed signal DDM_Rxindex(f b_cfar Based on this, the Doppler frequency estimate of the target may be output.

[0344] Also, distance index f b_cfar This may be converted into distance information using equation (1) and output.

[0345] Furthermore, information input from the Doppler multiplexing unit 211 (for example, distance index f b_cfar , and the separation index information of Doppler multiplexed signals DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt If there are multiple )) the direction estimation unit 212 may calculate estimated directions of arrival for them in the same manner as described above and output the positioning result.

[0346] <Example of operation of direction estimation unit 212 2> For example, the direction estimation unit 212 uses the distance index f b_cfar and Doppler multiplexed signal separation index information DDM_Rxindex_Bq(f b_cfar Based on this, the output of the Doppler analysis unit 209 is extracted, and the virtual received array correlation vector h of the direction estimation unit 212 is generated. q (f b_cfar , DDM_Rxindex(f b_cfarThe system generates a DDM_Rxindex_Bq(f) and performs direction estimation based on the received signal corresponding to the transmitting antenna in beam direction Bq. Here, q = 1, ..., NB. For example, if the number of multi-beams NB = 2, then q = 1 or 2. The operation will be described below for the case where NB = 2, but is not limited to this case. The direction estimation unit 212 generates, for example, the separation index information DDM_Rxindex_Bq(f) of the Doppler multiplexed signal. b_cfar The beam direction Bq corresponding to q that matches ) is estimated.

[0347] For example, the direction estimation unit 212 performs direction estimation processing based on the received signal corresponding to the radar transmission signal from the transmitting antenna in beam direction Bq, and extracts a Bq beam antenna extraction vector SP that corresponds to the received signal of the transmitting antenna in beam direction Bq. Bq , and the virtual received array correlation vector h(f b_cfar , DDM_Rxindex_Bq (f b_cfar Based on ), the Bq beam antenna virtual receive array correlation vector h Bq (f b_cfar , DDM_Rxindex_Bq(f b_cfar )) is generated. Here, h Bq (f b_cfar , DDM_Rxindex_Bq (f b_cfar )) is N Bq This is a column vector with ×Na elements.

[0348] For example, the transmitting antennas in beam direction B1 are Tx#1 and Tx#3, and the transmitting antennas in beam direction B2 are Tx#2 and Tx#4, N B1 =2, N B2 =2, N t When = 4 and the number of receiving antennas Na = 4, the B1 beam antenna extraction vector SP extracts the received signal corresponding to the transmitting antenna in beam direction B1. B1 , and a B2 beam antenna extraction vector SP that extracts the received signal corresponding to the transmitting antenna in beam direction B2. B2 This is 16(=N) as shown in equations (13) and (14) below. t×Na) It may be expressed as the following column vector, where the superscript T represents the vector transpose.

number

number

[0349] The direction estimation unit 212, for example, extracts the B1 beam antenna vector SP. B1 Using the element index where an element is 1, the virtual receive array correlation vector h(f b_cfar , DDM_Rxindex_B1(f b_cfar Extract the element component of the element index from )) and arrange the column vector in ascending order of the element index to form the virtual received array correlation vector h by the B1 beam antenna. B1 (f b_cfar , DDM_Rxindex_B1(f b_cfar It is generated as ). For example, the B1 beam antenna extraction vector SP shown in equation (13) B1 In this case, the elements in the 1st to 4th and 9th to 12th element indices are 1. In this case, the direction estimation unit 212 calculates the virtual received array correlation vector h(f b_cfar , DDM_Rxindex_B1(f b_cfar From ), element components are extracted in the order of the 1st to 4th and 9th to 12th element indices, and the B1 beam antenna virtual receive array correlation vector h B1 (f b_cfar , DDM_Rxindex_B1(f b_cfar Generates )).

[0350] Similarly, the direction estimation unit 212 extracts, for example, the B2 beam antenna vector SP B2 Using the element index where an element is 1, the virtual receive array correlation vector h(f b_cfar , DDM_Rxindex_B2(f b_cfarExtract the element component of the element index from )) and arrange the column vector in ascending order of the element index to form the virtual received array correlation vector h by the B2 beam antenna. B2 (f b_cfar , DDM_Rxindex_B2(f b_cfar It is generated as ). For example, the B2 beam antenna extraction vector SP shown in equation (14) B2 In this case, the elements at the 5th to 8th and 13th to 16th element indices are 1. In this case, the direction estimation unit 212 calculates the virtual received array correlation vector h(f b_cfar , DDM_Rxindex_B2(f b_cfar From ), element components are extracted in the order of the 5th to 8th and 13th to 16th element indices, and the B2 beam antenna virtual receive array correlation vector h B2 (f b_cfar , DDM_Rxindex_B2(f b_cfar Generates )).

[0351] The direction estimation unit 212, for example, the Bq beam antenna virtual receiving array correlation vector h Bq (f b_cfar , DDM_Rxindex_Bq(f b_cfar Using )), the direction estimation evaluation function P H-Bq (θ u , f b_cfar , DDM_Rxindex_Bq(f b_cfar )) azimuthal direction θ u The angle is varied within a predetermined range, and the spatial profile for each Bq beam is calculated. Here, q = 1 or 2.

[0352] The direction estimation unit 212 may extract a predetermined number of maximum peaks in descending order of magnitude from the spatial profile based on the received signal corresponding to the transmitting antenna of the calculated beam direction Bq, and output the azimuth direction of the maximum peak as the estimated arrival direction value by the Bq beam (for example, positioning output).

[0353] Note that the direction estimation evaluation function value P H-Bq (θ u , f b_cfar, DDM_Rxindex_Bq(f b_cfar There are various methods for estimating the direction of arrival, depending on the direction of arrival algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0354] Furthermore, while the above example described an example in which the direction estimation unit 212 calculates the azimuth direction as the estimated direction of arrival, it is not limited to this. It is also possible to estimate the direction of arrival in the elevation direction by using virtual receiving antennas arranged in the elevation direction, or to estimate the direction of arrival in both the azimuth and elevation directions by using virtual receiving antennas arranged in the azimuth and elevation directions, such as in a rectangular grid. For example, the direction estimation unit 212 may calculate the azimuth and elevation directions as estimated directions of arrival and output them as positioning output.

[0355] Through the above operations, the direction estimation unit 212 of the radar device 10 outputs, for example, the distance index f b_cfar , Doppler multiplexed signal separation index information DDM_Rxindex_Bq(f b_cfar )=(f demul_Tx#1 ,~,f demul_Tx#NDM Based on the received signal from the transmitting antenna in the beam direction Bq, the direction of arrival estimate for the Bq beam may be output. Furthermore, the direction estimation unit 212 may output the distance index f as a positioning output. b_cfar , and the separation index information of Doppler multiplexed signals DDM_Rxindex_Bq(f b_cfar You may output ).

[0356] Furthermore, the direction estimation unit 212 uses, for example, the separation index information of the Doppler multiplexed signal DDM_Rxindex_Bq(f b_cfar Based on this, the Doppler frequency estimate of the target may be output.

[0357] Also, distance index f b_cfar This may be converted into distance information using equation (1) and output.

[0358] Furthermore, information input from the Doppler multiplexing unit 211 (for example, distance index fb_cfar , and the separation index information of Doppler multiplexed signals DDM_Rxindex_Bq(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt If there are multiple )) the direction estimation unit 212 may calculate estimated directions of arrival for them in the same manner as described above and output the positioning result.

[0359] The above describes the operation examples 1 and 2 of the direction estimation unit 212.

[0360] Next, we will describe examples of MIMO antenna configurations and examples of the operation of the direction estimation unit 212 when using these MIMO antenna configurations. In the following, the transmitting antenna and receiving antenna in a MIMO radar will be collectively referred to as MIMO antennas.

[0361] In the following description, each transmitting antenna included in the transmitting antenna section 105 may be a subarray configuration in which multiple planar patch antennas are arranged vertically and horizontally, as shown in Figure 19. In the example in Figure 19, the transmitting antenna consists of eight planar patch antennas in the vertical direction and four in the horizontal direction. For example, by changing the feeding phase for each patch antenna included in one transmitting antenna, it is possible to form a beam pattern (element pattern of the transmitting antenna) that directs a directional beam in a desired direction. Also, for example, the more horizontal (or vertical) planar patch antennas that make up one transmitting antenna, the sharper the horizontal (or vertical) directional beam can be formed. One transmitting antenna may consist of, for example, a number of planar patches that satisfies the desired beam width.

[0362] Note that the configuration of a single transmitting antenna is not limited to the example shown in Figure 19, and the number of patch antennas constituting a single transmitting antenna (for example, at least one of the total number, the number in the horizontal direction, and the number in the vertical direction) is not limited to the number shown in Figure 19. Also, a single transmitting antenna is not limited to a planar patch antenna, but may be configured with patch antennas arranged in either the vertical or horizontal direction.

[0363] [Layout example A] Configuration example A shows an example of a MIMO antenna configuration where one transmitting antenna corresponds to each transmitting beam. In configuration example A, each transmitting beam may be formed by one transmitting antenna.

[0364] Below, as an example, we will describe the antenna configuration of a MIMO radar with two transmitting antennas (e.g., Tx#1, Tx#2) and three receiving antennas (e.g., Rx#1, Rx#2, Rx#3).

[0365] For example, as shown in Figure 20, transmitting antennas Tx#1 and Tx#2 have different directional patterns for the transmitting beam direction (or directional beam direction). In Figure 20, Tx#1 has a directional pattern for beam direction B1 (beam B1), and Tx#2 has a directional pattern for beam direction B2 (beam B2). In arrangement example A, as shown in Figure 20, there is one transmitting antenna each with a directional pattern for beam direction B1 and beam direction B2, and N B1 =1, N B2 = 1

[0366] Furthermore, in the following, the directivity of the receiving antennas (e.g., Rx#1, Rx#2, Rx#3) may be omnidirectional, or have nearly uniform directivity characteristics within the field of view of the transmitting antennas (e.g., Tx#1 and Tx#2) in multiple beam directions.

[0367] For example, when the number of transmitting antennas Nt = 2 used for multiplex transmission, the radar device 10 sets the Doppler multiplexing number N in the Doppler shift unit 104. DM The radar transmission signal is transmitted using a Doppler multiplexed signal where = 2. In this case, for example, in setting the Doppler shift amount as described above, N B1 =1, N B2 The assignment of Doppler multiplexing signals with =1 can be applied.

[0368] Furthermore, for example, the arrangement of the transmitting antennas Tx#1 and Tx#2, and the receiving antennas Rx#1 to Rx#3, constitutes the arrangement of virtual receiving antennas (or MIMO virtual antennas) VA#1 to VA#6.

[0369] Here, the arrangement of the virtual receiving antenna (virtual receiving array) may be expressed as shown in equation (15) below, based on, for example, the position of the transmitting antenna constituting the transmitting antenna section 105 (for example, the position of the feed point) and the position of the receiving antenna constituting the receiving antenna section 202 (for example, the position of the feed point).

number

[0370] Here, the position coordinates of the transmitting antenna (e.g., Tx#n) that constitutes the transmitting antenna section 105 are (X T_#n ,Y T_#n (For example, n=1,~, Nt) is used to represent the position coordinates of the receiving antenna (for example, Rx#z) that constitutes the receiving antenna section 202, and (X R_#z ,Y R_#z (For example, z=1,~, Na) is used to represent the position coordinates of the virtual antenna VA#b that constitutes the virtual receiving array antenna (X V_#b ,Y V_#b (For example, b=1,~, Nt×Na)

[0371] Note that in equation (15), for example, VA#1 is represented as the position reference (0,0) of the virtual receive array.

[0372] The following describes MIMO antenna configuration examples A-1, A-2, and A-3. Note that X T_#n represents the horizontal position coordinate, Y T_#n This is explained as representing vertical position coordinates, but it is not limited to this.

[0373] <Layout example A-1> Figure 21 shows an example of antenna configuration related to configuration example A-1. Figure 21(a) shows an example of MIMO antenna configuration (Tx#1, Tx#2, Rx#1~Rx#3), and Figure 21(b) shows an example of virtual receiving antenna configuration (VA#1~VA#6) formed by the MIMO antenna configuration in Figure 21(a).

[0374] As shown in Figure 21(a), in arrangement example A-1, the receiving antennas Rx#1 to Rx#3 are arranged horizontally (horizontal direction in Figure 21) at intervals of Dr. Also in arrangement example A-1, the transmitting antennas Tx#1 and Tx#2 are arranged horizontally at intervals of Dr (Dt=Dr) and vertically (vertical direction in Figure 21) at different positions (for example, at intervals of Dv).

[0375] For example, the arrangement of transmitting antennas Tx#1 and Tx#2 shown in Figure 21(a) (X T_#1 ,Y T_#1 )=(0,0),(X T_#2 ,Y T_#2 )=(D r , D V ), and the arrangement of receiving antennas Rx#1~Rx#3 (X R_#1 ,Y R_#1 )=(ax,ay),(X R_#2 ,Y R_#2 ) = (ax + D r ,ay),(X R_#3 ,Y R_#3 )=(ax+2D r In the case of ,ay), the position coordinates of the virtual antennas VA#1 to VA#6 that constitute the virtual receiving antenna are calculated from equation (15). Here, ax and ay are arbitrary constants.

[0376] For example, the position coordinates of virtual antennas VA#1 to VA#6 are, as shown in Figure 21(b), independent of ax and ay, (X V_#1 ,Y V_#1 )=(0,0), (X V_#2 ,Y V_#2 )=(D r , 0), (X V_#3 ,Y V_#3 )=(2D r , 0), (X V_#4 ,YV_#4 )=(D r ,D V ), (X V_#5 ,Y V_#5 )=(2D r , D V ), (X V_#6 ,Y V_#6 )=(3D r , D V )

[0377] For example, in the operation example 1 of the direction estimation unit 212 described above, the direction estimation unit 212 receives information from the Doppler multiplexing / decoupling unit 211 as Doppler multiplexing signal separation index information DDM_Rxindex(f b_cfar )=(f demul_Tx#1 , f demul_Tx#2 ,~,f demul_Tx#Nt If it includes ), the virtual receive array correlation vector h(f) shown in equation (10) b_cfar , DDM_Rxindex(f b_cfar Generate )) and perform direction estimation processing.

[0378] Here, the signal received by the b-th virtual antenna VA#b is the virtual received array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar It is represented by the b-th element of ))

[0379] Furthermore, the separation index information DDM_Rxindex(f b_cfar This includes Doppler separation information for Nt transmitting antennas. This is the case when the target direction is, for example, the target direction (2) shown in Figure 20, and corresponds to the region where the beam directions of transmitting antennas Tx#1 and Tx#2 overlap. In this case, radar transmission signals from both transmitting antennas Tx#1 and Tx#2 are reflected by the target and received by receiving antennas Rx#1 to Rx#3. Therefore, in this case, the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#1 to VA#6 corresponding to both Tx#1 and Tx#2.

[0380] In the MIMO antenna configuration shown in Figure 21(a), Tx#1 has a directional characteristic in beam direction B1, and Tx#2 has a directional characteristic in beam direction B2, corresponding to different beam directions. Furthermore, as shown in Figure 20, the beam directions of Tx#1 and Tx#2 overlap in an angular region approximately equal to the beam width. Here, as shown in Figure 21(a), the arrangement of Tx#1 and Tx#2 is offset vertically (offset value Dv). Therefore, if a target exists in the overlapping region of the beam directions of Tx#1 and Tx#2 (for example, target direction (2) shown in Figure 20), the direction estimation unit 212 can measure angles in the vertical direction in addition to the horizontal direction.

[0381] Furthermore, in the arrangement of Tx#1 and Tx#2 shown in Figure 21(a), the horizontal offset Dt is Dt = Dr. Thus, since Tx#1 and Tx#2 are arranged with an offset in the horizontal direction equal to the element spacing Dr of the receiving antennas Rx#1 to Rx#3, as shown in Figure 21(b), the virtual receiving antenna arrangement includes arrangements in which the horizontal positions of multiple virtual antennas (e.g., VA#2 and VA#4, or VA#3 and VA#5) coincide, but their vertical positions differ by Dv. With such a virtual receiving antenna arrangement, the direction estimation unit 212 can easily measure the vertical angle based, for example, on the received phase difference between two virtual antennas whose horizontal positions coincide (e.g., VA#2 and VA#4, or VA#3 and VA#5).

[0382] In the first example of the operation of the direction estimation unit 212, in Figure 21, Dt and Dr may be set to, for example, one wavelength or more. In this case, as a result of the direction estimation processing in the direction estimation unit 212, grating loops may occur, and ambiguity may arise in the horizontal direction estimation. The direction estimation unit 212 uses, for example, the separation index information of the Doppler multiplexed signal DDM_Rxindex(f b_cfar Based on this, the true direction can be detected even when a grating lobe occurs, by identifying the location of the target in the direction of the overlapping region between beam direction B1 and beam direction B2.

[0383] Furthermore, in the above-described example of the operation of the direction estimation unit 212, the direction estimation unit 212 receives information from the Doppler multiplexing / decoupling unit 211 as the separation index information of the Doppler multiplexed signal DDM_Rxindex_Bq(f b_cfar If it includes ), the virtual receive array correlation vector h(f b_cfar , DDM_Rxindex_Bq (f b_cfar )) and Bq beam antenna extraction vector SP Bq Based on this, the Bq beam antenna virtual receive array correlation vector h Bq (f b_cfar , DDM_Rxindex_Bq(f b_cfar Generate )) and perform direction estimation processing.

[0384] Here, the signal received by the b-th virtual antenna VA#b is the virtual received array correlation vector h(f b_cfar , DDM_Rxindex(f b_cfar It is represented by the b-th element of ))

[0385] Furthermore, the separation index information DDM_Rxindex_Bq(f b_cfar ) is N Bq This includes Doppler separation information for the transmitting antenna in beam direction Bq. This is the case where the target direction is, for example, target direction (1) (e.g., beam direction B1) or target direction (3) (e.g., beam direction B2) as shown in Figure 20, and corresponds to the beam direction region of the transmitting antenna Tx#q. In this case, the radar transmission signal from the transmitting antenna Tx#q is reflected by the target and received by the receiving antennas Rx#1 to Rx#3.

[0386] Therefore, in this case, for example, when q=1 (when the target direction is the target direction (1) shown in Figure 20), the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#1 to VA#3 corresponding to Tx#1. Also, for example, when q=2 (when the target direction is the target direction (3) shown in Figure 20), the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#4 to VA#6 corresponding to Tx#2.

[0387] In the second example of the operation of the direction estimation unit 212, Dr may be set to, for example, 1 wavelength or more in Figure 21. In this case, as a result of the direction estimation processing in the direction estimation unit 212, grating loops may occur, and ambiguity may arise in the horizontal direction estimation. The direction estimation unit 212 uses, for example, the separation index information of the Doppler multiplexed signal DDM_Rxindex_Bq(f b_cfar Based on this, the presence of a target in the direction of beam direction B1 or beam direction B2 can be identified, thus enabling the detection of the true direction even when grating lobes occur.

[0388] <Layout example A-2> Figure 22 shows an example of antenna configuration related to configuration example A-2. Figure 22(a) shows an example of MIMO antenna configuration (Tx#1, Tx#2, Rx#1~Rx#3), and Figure 22(b) shows an example of virtual receiving antenna configuration (VA#1~VA#6) formed by the MIMO antenna configuration in Figure 22(a).

[0389] As shown in Figure 22, in arrangement example A-2, the receiving antennas Rx#1 to Rx#3 are arranged horizontally (horizontal direction in Figure 22) at intervals of Dr. Also in arrangement example A-2, the transmitting antennas Tx#1 and Tx#2 are arranged horizontally at intervals of Dt and are positioned vertically (vertical direction in Figure 22) at the same position (for example, without offset). The difference between the interval Dt and the interval Dr may be a specified value based on the wavelength λ of the radar transmission signal (for example, half a wavelength).

[0390] For example, the arrangement of transmitting antennas Tx#1 and Tx#2 shown in Figure 22(a) (X T_#1,Y T_#1 )=(0,0),(X T_#2 ,Y T_#2 )=(D t , 0), and arrangement of receiving antennas Rx#1~Rx#3 (X R_#1 ,Y R_#1 )=(ax,ay),(X R_#2 ,Y R_#2 ) = (ax + D r ,ay),(X R_#3 ,Y R_#3 )=(ax+2D r In the case of ,ay), the position coordinates of the virtual antennas VA#1 to VA#6 that constitute the virtual receiving antenna are calculated from equation (15). Here, ax and ay are arbitrary constants.

[0391] For example, the position coordinates of virtual antennas VA#1 to VA#6 are, as shown in Figure 22(b), independent of ax and ay, (X V_#1 ,Y V_#1 )=(0,0), (X V_#2 ,Y V_#2 )=(D r , 0), (X V_#3 ,Y V_#3 )=(2D r , 0), (X V_#4 ,Y V_#4 )=(D t ,0), (X V_#5 ,Y V_#5 )=( D t +D r , 0), (X V_#6 ,Y V_#6 )=(D t +2D r , 0).

[0392] For example, the first example of operation of the direction estimation unit 212 described above is the case where the target direction is the target direction (2) shown in Figure 20, and corresponds to the region where the beam directions of transmitting antennas Tx#1 and Tx#2 overlap. In this case, radar transmission signals from both transmitting antennas Tx#1 and Tx#2 are reflected by the target and received by receiving antennas Rx#1 to Rx#3. Therefore, in this case, the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#1 to VA#6 that correspond to both Tx#1 and Tx#2.

[0393] In the MIMO antenna configuration shown in Figure 22(a), Tx#1 has a directional characteristic in beam direction B1, and Tx#2 has a directional characteristic in beam direction B2, corresponding to different beam directions. Furthermore, as shown in Figure 20, the beam directions of Tx#1 and Tx#2 overlap in an angular region approximately equal to the beam width. Here, as shown in Figure 22(a), the arrangement of Tx#1 and Tx#2 is offset horizontally (offset value Dt), so as shown in Figure 22(b), the horizontal aperture length in the virtual receiving antenna configuration is expanded. Therefore, when a target exists in the overlapping region of the beam directions of Tx#1 and Tx#2 (for example, target direction (2) shown in Figure 20), the angular resolution in the direction estimation processing of the direction estimation unit 212 is improved.

[0394] Furthermore, in Figure 22(b), for example, the spacing between virtual antennas VA#2 and VA#4, and the spacing between virtual antennas VA#3 and VA#5 are Dt-Dr if Dt>Dr, and Dr-Dt if Dr>Dt. For example, if the absolute value of the difference between the transmitting antenna spacing Dt and the receiving antenna spacing Dr, |Dt-Dr|, is set to half a wavelength, the radar device 10 can suppress grating lobes within a field of view of ±90°. For example, if Dt=1.5λ and Dr=1λ, then |Dt-Dr|=0.5λ.

[0395] Although the explanation described the case where the difference between Dt and Dr, |Dt-Dr| (default value), is set to half a wavelength (0.5λ), it is not limited to this. For example, |Dt-Dr| may be set to any value in the range of approximately 0.45λ to 0.8λ (for example, any value in the range of 0.5 to 0.8 times the wavelength of the radar transmission signal).

[0396] For example, |Dt-Dr| may be set according to the horizontal field of view of the radar device 10, and grating lobes within the field of view can be suppressed. For example, if the horizontal field of view is wide, in the range of ±70 degrees to ±90 degrees, |Dt-Dr| may be set to about 0.5λ. Alternatively, if the horizontal field of view is narrow, in the range of ±20 degrees to ±40 degrees, |Dt-Dr| may be set to a wider interval, for example, about 0.7λ.

[0397] In addition, Dv in arrangement example A-2 and other arrangement examples may be set to a value of approximately 0.45λ to 0.8λ (for example, any value in the range of 0.5 to 0.8 times the wavelength of the radar transmission signal). Dv may be set according to the vertical field of view of the radar device 10, for example. For example, if the vertical field of view is wide, in the range of ±70 degrees to ±90 degrees, Dv may be set to approximately 0.5λ. Alternatively, if the vertical field of view is narrow, in the range of ±20 degrees to ±40 degrees, Dv may be set to a wider interval, for example, approximately 0.7λ.

[0398] Here, λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, when a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency in the frequency sweep bandwidth of the chirp signal.

[0399] Furthermore, the second example of operation of the direction estimation unit 212 described above is the case where the target direction is, for example, target direction (1) or target direction (3) shown in Figure 20, and corresponds to the region of the beam direction of the transmitting antenna Tx#q. In this case, the radar transmission signal from the transmitting antenna Tx#q is reflected by the target and received by the receiving antennas Rx#1 to Rx#3.

[0400] Therefore, in this case, for example, when q=1 (when the target direction is the target direction (1) shown in Figure 20), the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#1 to VA#3 corresponding to Tx#1. Also, for example, when q=2 (when the target direction is the target direction (3) shown in Figure 20), the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#4 to VA#6 corresponding to Tx#2. In the case of Operation Example 2 of the direction estimation unit 212 in Arrangement Example A-2, the arrangement is the same as in Arrangement Example A-1, and the same effect as in Arrangement Example A-1 is obtained.

[0401] <Layout example A-3> Figure 23 shows an example of antenna configuration related to configuration example A-3. Figure 23(a) shows an example of MIMO antenna configuration (Tx#1, Tx#2, Rx#1~Rx#3), and Figure 23(b) shows an example of virtual receiving antenna configuration (VA#1~VA#6) formed by the MIMO antenna configuration in Figure 23(a).

[0402] As shown in Figure 23, in arrangement example A-3, the receiving antennas Rx#1 to Rx#3 are arranged horizontally (horizontal direction in Figure 23) at intervals of Dr. Also in arrangement example A-3, the transmitting antennas Tx#1 and Tx#2 are arranged horizontally at intervals of Dt, and are positioned vertically (vertical direction in Figure 23) at different positions (for example, with an offset of Dv). The difference between the interval Dt and the interval Dr may be a specified value based on the wavelength λ of the radar transmission signal (for example, half a wavelength).

[0403] For example, the arrangement of transmitting antennas Tx#1 and Tx#2 shown in Figure 23(a) (X T_#1 ,Y T_#1 )=(0,0),(X T_#2 ,Y T_#2 )=(D t , D v ), and the arrangement of receiving antennas Rx#1~Rx#3 (X R_#1 ,Y R_#1 )=(ax,ay),(X R_#2 ,Y R_#2) = (ax + D r ,ay),(X R_#3 ,Y R_#3 )=(ax+2D r In the case of ,ay), the position coordinates of the virtual antennas VA#1 to VA#6 that constitute the virtual receiving antenna are calculated from equation (15). Here, ax and ay are arbitrary constants.

[0404] For example, the position coordinates of virtual antennas VA#1 to VA#6 are, as shown in Figure 23(b), independent of ax and ay, (X V_#1 ,Y V_#1 )=(0,0), (X V_#2 ,Y V_#2 )=(D r , 0), (X V_#3 ,Y V_#3 )=(2D r , 0), (X V_#4 ,Y V_#4 )=(D t , D v ), (X V_#5 ,Y V_#5 )=(D t +D r , D v ), (X V_#6 ,Y V_#6 )=(D t +2D r , D v )

[0405] For example, the first example of operation of the direction estimation unit 212 described above is the case where the target direction is the target direction (2) shown in Figure 20, and corresponds to the region where the beam directions of transmitting antennas Tx#1 and Tx#2 overlap. In this case, radar transmission signals from both transmitting antennas Tx#1 and Tx#2 are reflected by the target and received by receiving antennas Rx#1 to Rx#3. Therefore, in this case, the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#1 to VA#6 that correspond to both Tx#1 and Tx#2.

[0406] In the MIMO antenna configuration shown in Figure 23(a), Tx#1 has a directional characteristic for beam direction B1, and Tx#2 has a directional characteristic for beam direction B2, corresponding to different beam directions. Furthermore, as shown in Figure 20, the beam directions of Tx#1 and Tx#2 overlap in an angular region approximately equal to the beam width. Here, as shown in Figure 23(a), the arrangement of Tx#1 and Tx#2 is offset vertically (offset value Dv), similar to configuration example A-1. Therefore, if a target exists in the overlapping region of Tx#1 and Tx#2 (for example, target direction (2) shown in Figure 20), the direction estimation unit 212 can measure angles in the vertical direction in addition to the horizontal direction.

[0407] Furthermore, as shown in Figure 23(a), the arrangement of Tx#1 and Tx#2 is offset horizontally (offset value Dt), similar to arrangement example A-2. As a result, as shown in Figure 23(b), the horizontal aperture length in the virtual receiving antenna arrangement is expanded. Therefore, when a target exists in the overlapping region of the beam directions of Tx#1 and Tx#2 (for example, the target direction (2) shown in Figure 20), the angular resolution in the direction estimation processing of the direction estimation unit 212 is improved.

[0408] Furthermore, in Figure 23(b), for example, the spacing between virtual antennas VA#2 and VA#4, and the spacing between virtual antennas VA#3 and VA#5, is Dt-Dr if Dt>Dr, and Dr-Dt if Dr>Dt. For example, if the absolute value of the difference between the transmitting antenna spacing Dt and the receiving antenna spacing Dr, |Dt-Dr|, is set to half a wavelength, the radar device 10 can suppress grating lobes within a field of view of ±90°. For example, if Dt=1.5λ and Dr=λ, then |Dt-Dr|=0.5λ. For example, if the field of view for angle detection by the radar device 10 is narrower than the ±90° range, the radar device 10 can suppress grating lobes within the field of view by setting |Dt-Dr| to approximately 0.5~0.8 wavelengths.

[0409] Furthermore, the second example of operation of the direction estimation unit 212 described above is the case where the target direction is, for example, target direction (1) or target direction (3) shown in Figure 20, and corresponds to the region of the beam direction of the transmitting antenna Tx#q. In this case, the radar transmission signal from the transmitting antenna Tx#q is reflected by the target and received by the receiving antennas Rx#1 to Rx#3.

[0410] Therefore, in this case, for example, when q=1 (when the target direction is the target direction (1) shown in Figure 20), the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#1 to VA#3 corresponding to Tx#1. Also, for example, when q=2 (when the target direction is the target direction (3) shown in Figure 20), the direction estimation unit 212 can perform direction estimation using the received signals of virtual antennas VA#4 to VA#6 corresponding to Tx#2. In the case of Operation Example 2 of the direction estimation unit 212 in Arrangement Example A-3, the arrangement is the same as in Arrangement Example A-1, and the same effect as in Arrangement Example A-1 is obtained.

[0411] The above explains arrangement example A.

[0412] [Layout example B] Configuration Example B is an example of a MIMO antenna configuration where two or more transmitting antennas correspond to each transmitting beam. In Configuration Example B, each transmitting beam may be formed by two or more transmitting antennas.

[0413] Below, as an example, we will describe the antenna configuration of a MIMO radar with four transmitting antennas Nt (e.g., Tx#1, Tx#2, Tx#3, Tx#4) and three receiving antennas Na (e.g., Rx#1, Rx#2, Rx#3).

[0414] For example, as shown in Figure 24, transmitting antennas Tx#1 and Tx#3 and transmitting antennas Tx#2 and Tx#4 have different directional patterns for the transmitting beam direction (or directional beam direction). In Figure 25, Tx#1 and Tx#3 have directional patterns for beam direction B1 (beam B1), and Tx#2 and Tx#4 have directional patterns for beam direction B2 (beam B2). In arrangement example B, as shown in Figure 24, there are 2 transmitting antennas each with directional patterns for beam direction B1 and beam direction B2, and N B1 =2, N B2 = 2

[0415] Furthermore, in the following, the directivity of the receiving antennas (e.g., Rx#1, Rx#2, Rx#3) may be omnidirectional, or have nearly uniform directivity characteristics within the field of view of the transmitting antennas (e.g., Tx#1 to Tx#4) in multiple beam directions.

[0416] For example, when the number of transmitting antennas Nt = 4 used for multiplex transmission, the radar device 10 sets the Doppler multiplexing number N in the Doppler shift unit 104. DM The radar transmission signal is transmitted using a Doppler multiplexed signal where =4. In this case, for example, in setting the Doppler shift amount as described above, N B1 =2, N B2 The Doppler multiplexing signal assignment of =2 can be applied.

[0417] Furthermore, for example, the arrangement of the transmitting antennas Tx#1 to Tx#4 and the receiving antennas Rx#1 to Rx#3 constitutes the arrangement of virtual receiving antennas (or MIMO virtual antennas) VA#1 to VA#12 (not shown).

[0418] In arrangement example B, based on the MIMO antenna arrangement example of arrangement example A, the transmitting antenna for each transmitting beam may be further positioned at a horizontally or vertically offset position, or at a position offset in both the horizontal and vertical directions (for example, diagonally).

[0419] Figure 25 shows an example of the MIMO antenna configuration (Tx#1~Tx#4, Rx#1~Rx#3) for configuration example B.

[0420] Figure 25(a) shows an example of a configuration in which transmitting antennas (e.g., Tx#3 and Tx#4) are added horizontally to each of the transmitting beams (e.g., beam directions B1 and B2), based on the MIMO antenna configuration of configuration example A-1 (e.g., Figure 21(a)).

[0421] Furthermore, Figure 25(b) shows an example of a configuration in which, based on the MIMO antenna configuration of configuration example A-1 (for example, Figure 21(a)), transmitting antennas (for example, Tx#3 and Tx#4) are added vertically in each of the transmitting beams (for example, beam directions B1 and B2).

[0422] For example, in Figures 25(a) and 25(b), the arrangement of the transmitting antennas Tx#1 and Tx#2, and the receiving antennas Rx#1 to Rx#3 is the same as the MIMO antenna arrangement in Figure 21.

[0423] In Figure 25(a), transmitting antenna Tx#3 is positioned horizontally offset from transmitting antenna Tx#1 by a distance (e.g., 3Dr) greater than the horizontal aperture length of the receiving antenna (e.g., 2Dr). Similarly, in Figure 25(a), transmitting antenna Tx#4 is positioned horizontally offset from transmitting antenna Tx#2 by a distance (e.g., 3Dr) greater than the horizontal aperture length of the receiving antenna (e.g., 2Dr).

[0424] As shown in Figure 25(a), the aperture length of the virtual receiving antenna (not shown) is increased, thereby improving the horizontal angular resolution of the radar device 10.

[0425] Furthermore, in Figure 25(b), transmitting antenna Tx#3 is positioned with a vertical offset of 2Dv relative to transmitting antenna Tx#1. Similarly, in Figure 25(b), transmitting antenna Tx#4 is positioned with a vertical offset of 2Dv relative to transmitting antenna Tx#2.

[0426] With the arrangement shown in Figure 25(b), the vertical aperture length of the virtual receiving antenna is increased, which improves the vertical angular resolution in, for example, operation example 1 of the direction estimation unit 212. Also, with the arrangement shown in Figure 25(b), even when the target direction is the target direction (1) shown in Figure 24, the arrangement of Tx#1 and Tx#3 is offset vertically, so the direction estimation unit 212 can measure angles in the vertical direction as well as the horizontal direction. Similarly, even when the target direction is the target direction (3) shown in Figure 24, the arrangement of Tx#2 and Tx#4 is offset vertically, so the direction estimation unit 212 can measure angles in the vertical direction as well as the horizontal direction.

[0427] Note that the beam direction and the arrangement of the transmitting antennas are not limited to the examples shown in Figures 24 and 25. For example, the arrangement of Tx#2 and Tx#3 in Figure 25(a) may be swapped, or the arrangement of Tx#2 and Tx#3 in Figure 25(b) may be swapped.

[0428] Furthermore, the number of transmitting antennas for each beam direction is not limited to two; the number of transmitting antennas for at least one of multiple different beam directions may be three or more.

[0429] The above explains arrangement example B.

[0430] In arrangement examples A and B, the arrangement of the receiving antennas (Rx#1 to Rx#3) was described as being in the same position vertically and offset horizontally at equal intervals of Dr. However, the arrangement of the receiving antennas is not limited to this. For example, in the horizontal arrangement of the receiving antennas, the spacing between the receiving antennas may be unequal.

[0431] Furthermore, for example, the vertical positions of the receiving antennas do not all have to be in the same position; some of the receiving antennas may be arranged with an offset vertical position. For example, the arrangement of receiving antennas Rx#1 to Rx#3 may be (X R_#1 ,Y R_#1 )=(ax,ay),(X R_#2 ,Y R_#2 ) = (ax + D r ,ay),(X R_#3 ,Y R_#3 )=(ax+2D r The configuration is as follows: (,ay+Dv_offset). In this case, Rx#3 is positioned vertically offset by Dv_offset (or at a different position) from the vertical positions of Rx#1 and #2. By not making all the receiving antennas the same vertical position, and instead offsetting the vertical positions of some of the receiving antennas, for example, in operation example 2 of the direction estimation unit 212, the direction estimation unit 212 can measure angles in the vertical direction in addition to the horizontal direction.

[0432] Furthermore, for example, the vertical positions of the receiving antennas do not all have to be the same. Instead, the vertical positions of some receiving antennas may be offset, and their horizontal positions may be made the same as the horizontal positions of the other receiving antennas. For example, the arrangement of receiving antennas Rx#1 to Rx#3 may be (X R_#1 ,Y R_#1 )=(ax,ay),(X R_#2 ,Y R_#2 ) = (ax + D r ,ay),(X R_#3 ,Y R_#3 ) = (ax + D r This is done as follows: (,ay+Dv_offset). In this case, Rx#3 is positioned vertically offset by Dv_offset relative to the vertical positions of Rx#1 and #2, and horizontally at the same position as the horizontal position of Rx#2.

[0433] In this way, by not making the vertical positions of all the receiving antennas the same, but offsetting the vertical positions of some of the receiving antennas, and further arranging them so that their horizontal positions are the same as the horizontal positions of the other receiving antennas, for example, in operation example 2 of the direction estimation unit 212, the direction estimation unit 212 becomes capable of measuring angles in the vertical direction as well as the horizontal direction.

[0434] Here, ax and ay are arbitrary constants, and Dv_offset may be set to a value of approximately 0.45λ to 0.8λ (for example, any value in the range of 0.5 to 0.8 times the wavelength of the radar transmission signal). Dv_offset may be set according to the vertical field of view of the radar device 10, for example. For example, if the vertical field of view is wide, in the range of ±70 degrees to ±90 degrees, Dv_offset may be set to approximately 0.5λ. Alternatively, if the vertical field of view is narrow, in the range of ±20 degrees to ±40 degrees, Dv_offset may be set to a wider interval, for example, approximately 0.7λ. In this way, by not setting the vertical positions of all the receiving antennas to the same position, and by arranging some of the receiving antennas with an offset vertical position, for example, in operation example 2 of the direction estimation unit 212, the direction estimation unit 212 can measure angles in the vertical direction in addition to the horizontal direction. Furthermore, for example, the number of receiving antennas is not limited to three; it can be two, four or more, or any number of antennas.

[0435] Furthermore, the MIMO antenna configurations described in Configuration Example A and Configuration Example B are merely examples and are not limiting. For example, a configuration in which other antennas (at least one of a transmitting antenna and a receiving antenna) are further arranged in addition to the MIMO antenna configuration described in Configuration Example A and Configuration Example B is also possible, with the horizontal and vertical directions reversed. Additionally, the spacing between transmitting antennas described in Configuration Example A and Configuration Example B may be applied to the spacing between receiving antennas, and the spacing between receiving antennas described in Configuration Example A and Configuration Example B may be applied to the spacing between transmitting antennas.

[0436] Alternatively, a MIMO antenna configuration combining configuration example A and configuration example B is also acceptable. For example, a transmitting antenna (1 antenna) corresponding to one of several different beam directions may be based on configuration example A, while transmitting antennas (2 or more antennas) corresponding to the other of several different beam directions may be based on configuration example B.

[0437] Through the operations described above, the direction estimation unit 212 can perform direction estimation processing in response to the fact that the separation operation of the Doppler multiplexing / separation unit 211 differs depending on the target direction in multibeam transmission.

[0438] For example, if the Doppler multiplexing separation unit 211 can separate Doppler multiplexed signals from all transmitting antennas (for example, in the case of target direction (2)), the direction estimation unit 212 can improve the angle measurement accuracy and angle measurement resolution by performing direction estimation using the received signals of Nt × Na virtual receiving antennas.

[0439] Furthermore, for example, the direction estimation unit 212 determines N when the Doppler multiplexing / determination unit 211 can separate the Doppler multiplexed signal from the transmitting antenna in the beam direction Bq (for example, in the target direction (1) or (3)). Bq By performing direction estimation using the received signals from ×Na virtual receiving antennas, the angle measurement accuracy and angle measurement resolution can be improved.

[0440] The above describes an example of the operation of the direction estimation unit 212.

[0441] As described above, in this embodiment, the radar device 10, in a multi-beam transmitting MIMO radar using unequal-spacing Doppler multiplexing, assigns different Doppler multiplexed signals (for example, patterns of different Doppler shift amounts) between multi-beams that satisfy at least condition 1 in the Doppler shift unit 104. As a result, even when there is a large difference in the received level between reflected waves corresponding to transmitting antennas having different directional characteristics, the radar device 10 can distinguish the transmitting antenna in the Doppler multiplexing separation unit 211, enabling Doppler multiplexing separation. Therefore, according to this embodiment, deterioration of target detection performance, or misestimation of Doppler frequency or deterioration of angle measurement performance can be suppressed.

[0442] Furthermore, for example, when assigning Doppler multiplexed signals in the Doppler shift unit 104, if conditions 1 and 2 described above are met, the radar device 10 can expand the detectable Doppler frequency range fd to the range -1 / (2Tr) ≤ fd < 1 / (2Tr) even when there is a large difference in the received level between reflected waves corresponding to transmitting antennas with different directional characteristics, thereby expanding the Doppler frequency range to the same extent as when using one transmitting antenna.

[0443] Furthermore, in the radar device 10 of this embodiment, as a multi-beam transceiver MIMO radar configuration, Doppler multiplexing and separation is possible without using beam direction determination processing using a directional receiving antenna (or directional receiving processing using a receiving array antenna), thus reducing the amount of computation required for receiving processing.

[0444] Furthermore, for example, in a multi-beam transceiver MIMO radar configuration, if receiving antennas with different beam directions are used, the number of receiving antennas available during angle measurement may decrease depending on the target direction, which can lead to a decrease in the angle measurement accuracy or angle measurement resolution of the radar device 10. In this embodiment, for example, Doppler multiplexing and separation can be performed regardless of the target direction without using directional receiving antennas, thus suppressing a decrease in angle measurement accuracy and angle measurement resolution.

[0445] Therefore, according to this embodiment, the detection performance of a multi-beam MIMO radar using unequal-interval Doppler multiplexing can be improved.

[0446] (Variation 1) In Modification 1, in multibeam transmission, there is one transmitting antenna corresponding to each of the different beam directions (for example, N B1 =N B2 This explains the case where Nt = 1 and Nt = 2.

[0447] For example, the Doppler shift unit 104 generates multiple Doppler multiplexed signals for any one of the multiple transmitting antennas by performing a phase rotation Φ n (m) may be added. For example, multiple Doppler shift amounts may be set for which one of the multiple transmitting antennas is assigned to a single transmitting antenna.

[0448] Below, N Bq = For a single transmitting antenna with beam direction Bq, the number of Doppler multiplexed signals generated in the Doppler shift unit 104 is "Number of Doppler Multiplexed Signals N". DOP(Bq) This is written as . Here, q = 1 or 2. As an example, the number of transmitting antennas in beam direction B2 in Doppler shift amount setting example 1 is N B2 = 1, and the number of Doppler multiplexed signals is N DOP(B2) = 1

[0449] For example, by satisfying condition 1(4) below, an effect similar to that of condition 1(2) can be obtained.

[0450] <Condition 1> (4) The number of Doppler multiplexed signals differs for each beam direction (N DOP(B1) ≠N DOP(B2) However, N B1 =N B2 (If = 1)

[0451] For example, the number of Doppler multiplexed signals (or the number of Doppler shift amounts assigned) N to be generated for a transmitting antenna with beam direction B1.DOP(B1) The number of Doppler multiplexed signals (or the number of Doppler shift amounts assigned) to be generated for the transmitting antenna in beam direction B2 is N. DOP(B2) These may be different. According to the setting in condition 1 (4), the number of transmitting antennas N t = 2, and the Doppler multiplexing number N DDM Even when = 2, and even when there is a large difference in received levels between reflected waves corresponding to transmitting antennas with different beam directions, Doppler multiplexing and separation are possible, similar to the embodiment described above.

[0452] The following describes an example of setting the Doppler shift amount in the Doppler shift unit 104.

[0453] <Example 5 for setting the Doppler shift amount> Figure 26 shows the number of transmitting antennas Nt=2, N B1 =1, N B2 An example of setting the pattern for the Doppler shift amount with respect to the transmit Doppler frequency when = 1 is shown. In Figure 26, Tx#1 is the transmit antenna in beam direction B1 (for example, the transmit antenna that forms transmit beam B1), and Tx#2 is the transmit antenna in beam direction B2 (for example, the transmit antenna that forms transmit beam B2).

[0454] In addition, in the example of setting the Doppler shift amount 5, as shown in Figure 26, the basic unit of the Doppler shift interval in the Doppler shift unit 104 is Δfd = 1 / (Tr × (N DM We set δ = 1 / (4Tr) and δ = 1, but the value of δ is not limited to this. δ can be a positive integer or a positive real number.

[0455] In the example shown in Figure 26, N B1 = For a single transmitting antenna Tx#1 with beam direction B1, the number of Doppler multiplexed signals generated by the Doppler shift unit 104 is N. DOP(B1) = 1, N B2 = For a single transmitting antenna Tx#2 with beam direction B2, the number of Doppler multiplexed signals generated by the Doppler shift unit 104 is N. DOP(B2) = 2

[0456] In the example shown in Figure 26, the first and second Doppler shift units 104 (or Doppler shift units 104-1 to 104-2) may perform the following operations.

[0457] The first Doppler shift unit 104, for example, to apply a Doppler shift amount DOP1 = -1 / (2Tr) to the first transmitting antenna Tx#1, outputs a phase rotation Φ1(m) = 2πDOP1 × (m-1)Tr = -π(m-1) for each transmission period Tr of the chirp signal.

[0458] The second Doppler shift unit 104 generates two Doppler multiplexed signals for, for example, the second transmitting antenna Tx#2. In the example in Figure 26, the second Doppler shift unit 104 generates a Doppler shift amount DOP 2-1 = -1 / (4Tr) and Doppler shift amount DOP 2-2 =1 / (4Tr) is applied. The second Doppler shift unit 104 applies two Doppler shift amounts DOP to the second transmitting antenna Tx#2. 2-1 and DOP 2-2 To add this, a phase rotation Φ2(m)=phseq[mod(m,4)+1] is added to the output for each transmission period Tr of the chirp signal.

[0459] Here, phseq[ps] represents the ps-th element of PhaseSeq=[0, 0, π, π]. For example, phseq[1]=phseq[2]=0 and phseq[3]=phase[4]=π. Also, mod(x,y) is a modulo operation function that represents the remainder when x is divided by y. Note that since two Doppler multiplexed signals are generated for the transmitting antenna Tx#2, the Doppler shift amount is DOP. 2-1 and Doppler shift amount DOP 2-2 The electricity is then divided into two.

[0460] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is defined as the Doppler shift interval "Δfd (n1, n2) It is written as "".

[0461] Furthermore, as shown in Figure 26, the Doppler shift amount DOP 2-1 The Tx#2 to which the value is assigned is denoted as "Tx#2-1", and the Doppler shift amount DOP 2-2 The Tx#2 to which the prefix is ​​applied will be denoted as "Tx#2-2".

[0462] In Figure 26, the interval between the Doppler shift amounts applied to each transmitting antenna Tx#1 and Tx#2 (e.g., Tx#2-1, Tx#2-2) (Doppler shift interval) is Δfd (1, 2-1) =Δfd, Δfd (2-1, 2-2) =2Δfd, Δfd (2-2,1) =Δfd. Therefore, in Figure 26, the intervals of the Doppler shift amounts applied to each transmitting antenna with a number of transmitting antennas Nt=2 are not all the same, but include unequal intervals (Δfd (1,2-1) =Δfd (2-2,1) ≠Δfd (2-1,2-2) This results in unequal-interval Doppler multiplexing (unequal-interval DDM transmission).

[0463] Furthermore, in Figure 26, the number of transmitting antennas in the beam direction B1 is N. B1 = 1, and the number of Doppler multiplexed signals N DOP(B1) Since = 1, this is a case where Doppler multiplexing does not occur with a transmitting antenna in beam direction B1.

[0464] Furthermore, in Figure 26, the number of transmitting antennas in beam direction B2 is N. B2 = 1, and the number of Doppler multiplexed signals N DOP(B2) = 2. Also, in Figure 26, the interval of the Doppler shift between transmitting antennas Tx#2-1 and Tx#2-2 in beam direction B2 is Δfd (2-1,2-2) =Δfd (2-2,2-1) = 2Δfd. Therefore, the intervals of the Doppler shift amounts applied to the transmitting antenna in beam direction B2 are all the same, resulting in equal-interval Doppler multiplexing (equal-interval DDM transmission).

[0465] Therefore, the example shown in Figure 26 is an example of setting a pattern for the Doppler shift amount that does not satisfy condition 2.

[0466] Furthermore, in the example shown in Figure 26, N DOP(B1) ≠N DOP(B2) And N B1 =N B2 Since = 1, the example shown in Figure 26 is an example of setting a pattern for the Doppler shift amount that satisfies condition 1 (4).

[0467] For example, when the target direction is beam direction B1, and when the target direction is beam direction B2, the radar device 10 receives a different number of Doppler multiplexed signals (for example, the number of Doppler multiplexed signals that satisfy condition 1(4)) depending on the target direction, similar to setting example 1. As a result, the radar device 10 can determine, for example, based on the detected Doppler frequency peaks (for example, the number of peaks), whether a decrease in the received level of the received signal corresponding to the transmitting antenna in beam direction B1 or a decrease in the received level of the received signal corresponding to the transmitting antenna in beam direction B2 has occurred in the Doppler multiplexing / deselection unit 211.

[0468] Also, for example, a transmitting antenna with beam direction B1 is a single-antenna transmitter (N B1 =1), Doppler multiplexing signal count N DOP(B1) = 1. Therefore, for example, if the Doppler multiplexing / decomposition unit 211 determines that the received signal corresponds to the received signal of the transmitting antenna in beam direction B1, the radar device 10 does not need to perform the Doppler multiplexing signal separation process for the received signal in beam direction B1. Through this operation of the Doppler multiplexing / decomposition unit 211, the radar device 10 can determine the Doppler frequency fd of the target in the range -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexing signal.

[0469] Furthermore, for example, the Doppler multiplexed signal transmitted from a transmitting antenna with beam direction B2 has a Doppler multiplexed signal number N. DOP(B2)= 2, and Doppler multiplexing is performed using a Doppler shift interval that results in equally spaced Doppler multiplexing without satisfying condition 2. Therefore, for example, if the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the received signal of the transmitting antenna in beam direction B2, the radar device 10 can separate the Doppler multiplexed signal using the existing Doppler multiplexed signal separation operation. In addition, the radar device 10 can determine the Doppler frequency fd of the target in the range -1 / (4Tr) ≤ fd < 1 / (4Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0470] Furthermore, for example, if the target direction is an intermediate direction between beam direction B1 and beam direction B2, and the target direction is an area direction where the beam widths of both beams overlap by approximately 3dB or 6dB (for example, target direction (2) shown in Figure 13), then the received level of the received signal corresponding to Tx#1 of beam direction B1 and the received level of the received signal corresponding to Tx#2 of beam direction B2 are approximately the same. Therefore, the signals transmitted from Nt transmitting antennas, including the respective transmitting antennas for beam direction B1 and beam direction B2, are Doppler multiplexed using Doppler shift intervals that result in unequal Doppler multiplexing. Thus, the radar device 10 can separate the Doppler multiplexed signals based on the existing Doppler multiplexed signal separation operation. Through this operation of the Doppler multiplexing separation unit 211, the radar device 10 can determine the Doppler frequency fd of the target in the range -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0471] It should be noted that the example of generating two Doppler multiplexed signals for a single transmitting antenna is not limited to the example shown in Figure 26; for example, multiple Doppler multiplexed signals can also be generated in the configuration example shown in Figure 27.

[0472] In the example shown in Figure 27, the first and second Doppler shift units 104 (or Doppler shift units 104-1 to 104-2) may perform the following operations.

[0473] The first Doppler shift unit 104, for example, to apply a Doppler shift amount DOP1 = 1 / (4Tr) to the first transmitting antenna Tx#1, outputs a phase rotation Φ1(m) = 2πDOP1 × (m-1)Tr = π(m-1) / 2 for each transmission period Tr of the chirp signal.

[0474] The second Doppler shift unit 104 generates two Doppler multiplexed signals for, for example, the second transmitting antenna Tx#2. In the example in Figure 27, the second Doppler shift unit 104 generates a Doppler shift amount DOP 2-1 = -1 / (2Tr) and Doppler shift amount DOP 2-2 Assign =0. The second Doppler shift unit 104 assigns two Doppler shift amounts DOP to the second transmitting antenna Tx#2. 2-1 and DOP 2-2 To add this, a phase rotation Φ2(m)=phseq[mod(m,4)+1] is added to the output for each transmission period Tr of the chirp signal.

[0475] Here, phseq[ps] represents the ps-th element of PhaseSeq=[0, π / 2, 0, π / 2]. For example, phseq[1]=phseq[3]=0 and phseq[2]=phase[4]=π / 2. Also, mod(x,y) is a modulo operation function that represents the remainder when x is divided by y. Note that since two Doppler multiplexed signals are generated for the transmitting antenna Tx#2, the Doppler shift amount DOP is used. 2-1 and Doppler shift amount DOP 2-2 The electricity is then divided into two.

[0476] It should be noted that the examples for generating two Doppler multiplexed signals are not limited to those described above. For example, two Doppler multiplexed signals can also be generated using PhaseSeq=[0, -π / 2, 0, -π / 2], [π, -π / 2,π, -π / 2], or [π, π / 2,π, π / 2].

[0477] Furthermore, the Doppler shift unit 104 may, for example, fixedly assign a Doppler shift amount to the transmitting antenna, or it may variably assign a Doppler shift amount depending on the transmission cycle. For example, the Doppler shift unit 104 may assign the Doppler shift amount shown in Figure 27 for odd-numbered transmission cycles and the Doppler shift amount shown in Figure 28 for even-numbered transmission cycles.

[0478] In the example of setting the Doppler shift amount shown in Figure 28, the assignment of the Doppler shift amount to beam direction B1 and the assignment of the Doppler shift amount to beam direction B2 are swapped, as in the setting of the Doppler shift amount shown in Figure 27.

[0479] In such cases, the radar device 10 may perform processing in the Doppler analysis unit 209 using the chirp signal of the odd-numbered transmission period (e.g., VFFT1) and processing in the Doppler analysis unit 209 using the chirp signal of the even-numbered transmission period (e.g., VFFT2). The radar device 10 may, for example, determine whether aliasing occurs in the Doppler range [±1 / (4Tr)] by detecting the phase difference between the FFT peaks obtained by VFFT1 and VFFT2.

[0480] (Modification 2) In the above embodiment, the case where the number of multi-beams NB = 2 was described, but the number of multi-beams NB may be 3 or more. Modification 2 describes the case where the number of multi-beams NB > 2.

[0481] When the number of multi-beams NB > 2, the Doppler shift unit 104 applies conditions 1a and 2a described later, instead of the conditions 1 and 2 described above, to assign a predetermined phase rotation Φ to each transmitting antenna, thereby assigning a different Doppler shift amount. n The (m) may be added to the output. This allows the radar device 10, as in the embodiment described above, to separate Doppler multiplexed signals even when the received power levels between received signals (reflected waves) corresponding to transmitting antennas with different beam directions differ significantly, thereby suppressing deterioration of positioning performance and radar detection performance.

[0482] The following describes conditions 1a and 2a regarding the amount of Doppler shift applied by the Doppler shift unit 104 when the number of multi-beams NB > 2.

[0483] The radar system 10 is, for example, a multi-beam MIMO radar that uses Nt transmitting antennas Tx#1 to Tx#Nt, including transmitting antennas with different beam directions, and may perform unequal-spacing Doppler multiplexing using the Nt transmitting antennas Tx#1 to Tx#Nt. For example, the Doppler shift unit 104 may apply unequal-spacing Doppler shifts to the Nt transmitting antennas.

[0484] Furthermore, the radar device 10 may simultaneously multiplex radar transmission signals from Nt transmitting antennas Tx#1 to Tx#Nt using Doppler multiplexing that satisfies the following condition 1a.

[0485] Here, the number of transmitting antennas N for each beam direction Bq. Bq Assume that ≥ 1. Also, assume that the number of transmitting antennas Nt ≥ 2NB-1, and the number of Doppler multiplexers N DDM Assume ≥ 2NB-1. Note that in the following explanation, the number of transmitting antennas N for each beam direction Bq is... Bq N B(q) It can also be written as (for example, N Bq =N B(q) ).

[0486] For example, the minimum number of transmitting antennas Nt is Nt = 2NB-1, where, among the transmitting antennas in each beam direction Bq, there is one transmitting antenna in one beam direction and two transmitting antennas in the other beam directions.

[0487] Furthermore, the sum of the number of transmitting antennas in each beam direction Bq is Nt. The radar device 10 may, for example, assign one Doppler multiplexed signal to one transmitting antenna. In this case, the number of Doppler multiplexed signals is N. DDM It is equal to Nt.

[0488] <Condition 1a> N of the q-th beam direction B(q) B(q) N are assigned to individual transmitting antennas. B(q) Each Doppler multiplexed signal satisfies one of the following conditions, where q = 1, ~, NB. (1) Among the Doppler multiplexed signals assigned to transmitting antennas in beam directions with the same Doppler multiplexing number, different Doppler intervals are included (1-i), or, if the Doppler multiplexing number is 3 or more, the same Doppler interval is included, but the order of those Doppler shift intervals is different (for example, they do not match even if any of the Doppler shift intervals corresponding to each beam direction are cyclically shifted on the Doppler frequency axis) (1-ii). (2) The Doppler multiplexing number is different for all beam directions.

[0489] For example, if, among NB multibeams, beam directions B(a), B(b), and B(c) have the same Doppler multiplexing number (for example, N B(a) =N B(b) =N B(c) In the case of N B(a) ≥2, N B(b) ≥2, N B(c) Let's explain the case where (≥2). Here, a, b, and c are integers within the range of 1 to NB, representing beam directions with the same Doppler multiplexing number.

[0490] In this case, if there are different Doppler intervals between the Doppler multiplexed signals assigned to beam direction B(a) and beam direction B(b), between the Doppler multiplexed signals assigned to beam direction B(b) and beam direction B(c), and between the Doppler multiplexed signals assigned to beam direction B(c) and beam direction B(a), then condition 1a (1-i) is satisfied. Also, for example, if the number of Doppler multiplexings is 3 or more, and the Doppler intervals assigned to beam directions B(a), B(b), and B(c) are the same, but the order of their Doppler shift intervals is different (for example, if cyclic shifting any of the Doppler shift intervals of B(a), B(b), and B(c) in the Doppler frequency domain does not result in matching the other Doppler shift intervals), then condition 1a (1-ii) is satisfied.

[0491] Furthermore, for example, the Doppler multiplexing number (N) assigned to a transmitting antenna with NB multi-beams in beam directions B(1), B(2), ~, B(NB) B(1) , N B(2) , ~, N B(NB) If all of them are different, then condition 1a (2) is satisfied.

[0492] Furthermore, the radar device 10 may, for example, simultaneously multiplex radar transmission signals from Nt transmitting antennas Tx#1 to Tx#Nt using Doppler multiplexing that satisfies the following condition 2a.

[0493] <Condition 2a> N in beam direction Bq B(q) For each transmitting antenna, unequal-spacing Doppler multiplexing (where N Bq If ≥ 2, the Doppler multiplexed signal is assigned to the transmitting antenna in the beam direction Bq.

[0494] By satisfying condition 2a, the detectable Doppler frequency range fd in the radar device 10 becomes -1 / (2 Tr) ≤ fd < 1 / (2Tr), which is wider than the existing Doppler detection range of equally spaced Doppler multiplexing, which is -1 / (2 Nt Tr) ≤ fd < 1 / (2 Nt Tr).

[0495] Furthermore, even if condition 1a is met but condition 2a is not, the detectable Doppler frequency range fd in the radar device 10 can be expanded beyond the existing Doppler detection range for equally spaced Doppler multiplexing, which is -1 / (2 Nt Tr) ≤ fd < 1 / (2 Nt Tr).

[0496] Furthermore, conditions 1a and 2a apply when there are no beams with overlapping field of view (FOV) between beam directions. If there are beams with overlapping field of view (FOV) between beam directions, the following conditions 1b and 2b may be applied, which include the Doppler multiplexed signal assigned to the transmitting antenna in the beam direction with overlapping field of view (hereinafter referred to as the "overlapping beam direction") (hereinafter referred to as the "overlapping beam direction Doppler multiplexed signal").

[0497] For example, if the field of view angles of beam direction B(1) and beam direction B(2) overlap, the Doppler multiplexed signal for the overlapping beam direction refers to the Doppler multiplexed signals assigned to beam direction B(1) and beam direction B(2), respectively, and the number of Doppler multiplexed signals is N. B(1) +N B(2) This is the result.

[0498] <Condition 1b> N of the q-th beam direction B(q) B(q) N are assigned to individual transmitting antennas. B(q) Each Doppler multiplexed signal satisfies one of the following conditions, where q = 1, ~, NB. (1) Among the Doppler multiplexed signals assigned to transmitting antennas in the beam direction or overlapping beam direction that have the same Doppler multiplexing number, different Doppler intervals are included (1-i), or, if the Doppler multiplexing number is 3 or more, the same Doppler intervals are included, but the order of their Doppler shift intervals is different (for example, they do not match even if one of the Doppler shift intervals corresponding to each beam direction or overlapping beam direction is cyclically shifted on the Doppler frequency axis) (1-ii). (2) The Doppler multiplexing number differs between all beam directions and between overlapping beam directions.

[0499] <Condition 2b> Unequal spacing Doppler multiplexing between transmitting antennas in beam direction Bq and by transmitting antennas in overlapping beam directions (where N Bq Doppler multiplex signals are assigned such that (for the case ≥ 2)

[0500] By satisfying condition 2b, the detectable Doppler frequency range fd in the radar device 10 becomes -1 / (2 Tr) ≤ fd < 1 / (2Tr). Furthermore, even if condition 1b is satisfied but condition 2b is not, the detectable Doppler frequency range fd in the radar device 10 can be expanded beyond the existing Doppler detection range of equally spaced Doppler multiplexing, which is -1 / (2 Nt Tr) ≤ fd < 1 / (2 Nt Tr).

[0501] The following is an example of how it works when NB=3.

[0502] <Example of operation 1> Example 1 describes an example of operation when NB=3 and there are no overlapping beam directions.

[0503] Figure 29 shows an example of beam patterns for beam directions B1, B2, and B3 when the number of multi-beams NB = 3 and there are no overlapping beam directions. As shown in Figure 29, when there are no overlapping parts in the beam patterns (or only small overlapping parts), conditions 1a and 2a may be applied.

[0504] For example, in Figure 29, when the target direction is one of beam direction B1, beam direction B2, or beam direction B3, the Doppler shift unit 104 satisfies condition 1a, allowing the radar device 10 to determine in the Doppler multiplexing / deselection unit 211 whether the received level of the received signal corresponding to the transmitting antenna in beam direction B1 is decreasing, the received level of the received signal corresponding to the transmitting antenna in beam direction B2 is decreasing, or the received level of the received signal corresponding to the transmitting antenna in beam direction B3 is decreasing.

[0505] Furthermore, for example, if the Doppler shift unit 104 satisfies condition 2a, the Doppler multiplexed signals transmitted from the transmitting antenna in beam direction B1 (or B2, B3) are Doppler multiplexed using Doppler shift intervals that result in unequal spacing Doppler multiplexing.

[0506] Therefore, for example, if the Doppler multiplexing / determination unit 211 determines that the received signal corresponds to the transmitted antenna in beam direction B1 (or B2, B3), the radar device 10 can separate the Doppler multiplexed signals using the existing Doppler multiplexed signal separation operation. Through this operation of the Doppler multiplexing / determination unit 211, the radar device 10 can determine the Doppler frequency fd of the target in the range -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0507] <Example of operation 2> Example 2 describes an example of operation when NB=3 and there are overlapping beam directions.

[0508] Figure 30 shows an example of beam patterns for beam directions B1, B2, and B3 when the number of multi-beams NB = 3 and there are overlapping beam directions. As shown in Figure 30, when there are overlapping parts in the beam patterns (or when there are many overlapping parts), conditions 1b and 2b may be applied.

[0509] For example, in Figure 30, if the target direction is one of beam directions B1, B2, or B3, which are different from the overlapping beam range (one of the target directions (1), (3), or (5) shown in Figure 30), the Doppler shift unit 104 will satisfy condition 1b, allowing the radar device 10 to determine in the Doppler multiplexing / deselection unit 211 whether the received signal corresponds to the transmitting antenna in beam direction B1, the transmitting antenna in beam direction B2, or the transmitting antenna in beam direction B3.

[0510] Furthermore, for example, in Figure 30, if the target direction is within the overlapping beam range (in the case of target direction (2) or (4) shown in Figure 30), the Doppler shift unit 104 satisfies condition 1b, allowing the radar device 10 to determine in the Doppler multiplexing / deselection unit 211 whether the received signal corresponds to the transmitted antennas in beam directions B1 and B2, or to the transmitted antennas in beam directions B2 and B3.

[0511] Furthermore, for example, if the Doppler shift unit 104 satisfies condition 2b, the Doppler multiplexed signals transmitted from the transmitting antenna in beam direction B1 (or B2, B3) are Doppler multiplexed using Doppler shift intervals that result in unequal spacing Doppler multiplexing. Therefore, for example, if the Doppler multiplexing / determination unit 211 determines that the received signal corresponds to the received signal of the transmitting antenna in beam direction B1 (or B2, B3), the radar device 10 can separate the Doppler multiplexed signals using the existing Doppler multiplexed signal separation operation. Through this operation of the Doppler multiplexing / determination unit 211, the radar device 10 can determine the Doppler frequency fd of the target within the range -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0512] Furthermore, for example, if the Doppler shift unit 104 satisfies condition 2b, the Doppler multiplexed signals transmitted from the transmitting antennas in beam directions B1 and B2 (or beam directions B2 and B3) are transmitted using Doppler shift intervals that result in unequal Doppler multiplexing. Therefore, for example, if the Doppler multiplexing separation unit 211 determines that the received signal corresponds to the received signal of the transmitting antennas in beam directions B1 and B2 (or beam directions B2 and B3), the radar device 10 can separate the Doppler multiplexed signals using the existing Doppler multiplexed signal separation operation. Through this operation of the Doppler multiplexing separation unit 211, the radar device 10 can determine the Doppler frequency fd of the target within the range -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0513] (Variation 3) In the embodiments and modifications described above, the case in which each beam direction in a multi-beam system is different from the others was explained, as shown in Figures 13, 20, 24, 29, and 30. However, the settings for the multi-beam system (e.g., beam direction and beam width) are not limited to the examples described above.

[0514] For example, each beam constituting a multibeam system may differ in at least one of its beam direction and beam width. Furthermore, the number of multibeams NB may be greater than or equal to 2.

[0515] The following describes an example of a multi-beam configuration.

[0516] <Multibeam configuration example 1> In Example Setting 1, for example, as shown in Figure 31, the beam directions and beam widths may differ in the multi-beam configuration (e.g., beam directions B1, B2, and B3). The beam directions in the horizontal direction (or horizontal plane) may differ in the multi-beam configuration (e.g., beam directions B1, B2, and B3), and the beam widths in the horizontal direction (or horizontal plane) may differ. The beam directions in the vertical direction (or vertical plane) may differ in the vertical direction (or vertical plane), and the beam widths in the vertical direction (or vertical plane) may differ.

[0517] <Multibeam configuration example 2> In the above embodiment, an example was described in which the beam direction differs in the horizontal direction (or horizontal plane), as shown in Figure 13, but the embodiment is not limited to this.

[0518] In example setting 2, for instance, the beam direction may also differ in the vertical direction (or vertical plane).

[0519] For example, as shown in Figure 32(a), in a multi-beam system (e.g., beam directions B1 and B2), the beam directions may be approximately the same in the horizontal direction (or horizontal plane), while they may be different in the vertical direction (or vertical plane).

[0520] Furthermore, as shown in Figure 32(b), for example, in a multi-beam system (e.g., beam directions B1, B2, and B3), the beam directions may differ in both the horizontal (or horizontal plane) and vertical (or vertical surface) directions.

[0521] <Multibeam configuration example 3> In example setting 3, for example, as shown in Figure 33, the beam directions may be the same but the beam widths may be different in the multi-beam configuration (e.g., beam directions B1 and B2). Also, the beam directions in the horizontal direction (or horizontal plane) may be the same but the beam widths in the horizontal direction (or horizontal plane) may be different in the multi-beam configuration (e.g., beam directions B1 and B2). Furthermore, the beam directions in the vertical direction (or vertical plane) may be the same but the beam widths in the vertical direction (or vertical plane) may be different in the multi-beam configuration (e.g., beam directions B1 and B2).

[0522] In Example 3, for example, the same configuration can be applied as in the above embodiment by replacing the "transmitting antennas with different beam directions" described in the above embodiment with "transmitting antennas with different beam widths" (hereinafter referred to as "different beams").

[0523] Below, as an example, we will describe the operation of the radar device 10 when the beam direction is the same but the beam width is different, using Doppler shift amount setting example 1. Note that the setting of the Doppler shift amount is not limited to setting example 1, and the device can operate similarly when using other Doppler shift amount setting examples, and the same effects as in the above embodiment can be obtained.

[0524] For example, if the number of transmitting antennas Nt = 3 (e.g., Tx#1, Tx#2, Tx#3), N B1 =2, N B2 When = 1, the above-described example 1 of setting the Doppler shift amount is applied. For example, Tx#1 and Tx#2 are transmitting antennas with beam width B1 (e.g., beam B1) as shown in Figure 33, and Tx#3 is a transmitting antenna with beam width B2 (e.g., beam B2) as shown in Figure 33. In Figure 33, an example is shown where the beam width of beam B1 is wider than the beam width of beam B2. Here, the beam widths of beam B1 and beam B2 may be in the horizontal direction (or horizontal plane), or in the vertical direction (or vertical plane), or both horizontal (or horizontal plane) and vertical (or vertical plane), and similar effects can be obtained.

[0525] Furthermore, in the radar device 10, the receiving antenna may be an omnidirectional antenna (or an antenna with substantially uniform directional characteristics within the field of view covered by both the transmitting antennas of beam B1 and beam B2).

[0526] For example, if the target position is either target position (1) or target position (3) as shown in Figure 33, the target position is within the beam width of beam B1 and within the field of view, so the received level of the reflected waves corresponding to the radar transmitted waves sent from Tx#1 and Tx#2 of beam B1 will be relatively high. On the other hand, target positions (1) and (3) are outside the beam width of beam B2 and outside the field of view, so the radiation direction of the radar transmitted waves sent from Tx#3 of beam B2 does not coincide with the direction of target positions (1) and (3), and target positions (1) and (3) are in the null direction of the transmitting antenna Tx#3 of beam B2. For this reason, the received level of the received signal corresponding to Tx#3 in the radar device 10 will be lower than the received levels of the received signals corresponding to Tx#1 and Tx#2. For example, the reception level of the received signal corresponding to Tx#3 differs significantly from the reception levels of the received signals corresponding to Tx#1 and Tx#2, and depending on the null beam directivity characteristics of Tx#3, it can be, for example, 10 dB or more lower. In such a case, the received signal received by the radar device 10 will be the received signal shown in Figure 12(a).

[0527] Furthermore, for example, if the target position is in a region where the field of view angles of both beam B1 and beam B2 overlap, as shown in target position (4) in Figure 33 (for example, at close range), the radar device 10 receives reflected waves corresponding to the radar transmitted waves from Tx#1 and Tx#2 of beam B1, and reflected waves corresponding to the radar transmitted waves from Tx#3 of beam B2. In this case, the received signal received by the radar device 10 may be, for example, a received signal like that shown in Figure 12(b). Alternatively, for example, if the directional gain of beam B2 is about 10 dB or more higher than that of beam B1, the received signal received by the radar device 10 may be, for example, a received signal like that shown in Figure 12(c).

[0528] Furthermore, for example, if the target position is within the field of view of beam B2 and outside the field of view of beam B1, as shown in target position (2) in Figure 33 (for example, at a far distance), the received level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 of beam B2 will be relatively high. On the other hand, since the directivity gain of beam B1 is smaller than that of beam B2, the received level of the reflected wave corresponding to the radar transmission waves transmitted from Tx#1 and Tx#2 of beam B1 will be lower compared to the received level of the received signal corresponding to Tx#3. For example, the received levels of the received signals corresponding to Tx#1 and Tx#2 will differ significantly from the received level of the received signal corresponding to Tx#3, and depending on the beam directivity characteristics of Tx#1 and Tx#2, the received level may be, for example, 10 dB or more lower. In such a case, the received signal received by the radar device 10 will be the received signal shown in Figure 12(c).

[0529] For example, as shown in Figure 12(b), when the radar device 10 receives the received signals corresponding to the transmitting antennas of each beam at approximately the same reception level, the signals transmitted from Nt transmitting antennas, including the respective transmitting antennas of beam B1 and beam B2, are Doppler multiplexed using Doppler shift intervals that result in unequal Doppler multiplexing. Therefore, the radar device 10 can separate the Doppler multiplexed signals based on the existing Doppler multiplexed signal separation operation.

[0530] Furthermore, as shown in Figures 12(a) and 12(c), when the radar device 10 receives reflected waves from either beam B1 or beam B2 (when there is a large difference in reception levels), it receives different Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 1) depending on the target position. Therefore, the Doppler multiplexing / decompression unit 211 can determine whether a decrease in the reception level of the received signal corresponding to the transmitting antenna of beam B1 or a decrease in the reception level of the received signal corresponding to the transmitting antenna of beam B2 has occurred.

[0531] For example, the Doppler multiplexed signal transmitted from the transmitting antenna of beam B1 is transmitted using a Doppler shift interval that results in unequal Doppler multiplexing. Therefore, for example, if the Doppler multiplexing / determination unit 211 determines that the received signal corresponds to the received signal of the transmitting antenna of beam B1, the radar device 10 can separate the Doppler multiplexed signal using the existing Doppler multiplexed signal separation operation.

[0532] Furthermore, for example, the transmitting antenna for beam B2 is a single-antenna transmitter. Therefore, for example, if the Doppler multiplexing / decoupling unit 211 determines that the received signal corresponds to the received signal of the transmitting antenna for beam B2, the radar device 10 does not need to perform Doppler multiplexing signal separation processing for the received signal of beam B2.

[0533] Through the operation of the Doppler multiplexing / decomposition unit 211, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr) ≤ fd < 1 / (2Tr), and obtain an output that associates the transmitting antenna with each Doppler multiplexed signal.

[0534] The embodiments of this disclosure have been described above.

[0535] [Other embodiments] In addition, in a radar device according to one embodiment of the present disclosure, the radar transmitter and the radar receiver may be individually arranged in physically separate locations. Furthermore, in a radar receiver according to one embodiment of the present disclosure, the direction estimation unit and the other components may be individually arranged in physically separate locations.

[0536] Furthermore, the number of transmitting antennas Nt, the number of receiving antennas Na, and the number of Doppler multiplexers N used in one embodiment of this disclosure DM NB is the number of beams in a multibeam system, and N is the number of transmitting antennas in each beam direction. BqThe numerical values ​​for parameters such as Doppler shift amount and Doppler shift interval are examples only and are not limited to those values. Furthermore, a portion of the transmitting antennas equipped in the radar system may be used as the number of transmitting antennas Nt.

[0537] Furthermore, the MIMO antenna arrangement examples used in one embodiment of this disclosure (e.g., arrangement example A, arrangement example B) were described as transmitting radar transmission signals from multiple transmitting antennas using Doppler multiplexing, but are not limited to this. For example, the MIMO antenna arrangement can also be applied when transmitting radar transmission signals from multiple transmitting antennas using time-division multiplexing or code-division multiplexing, and the effects of the disclosed MIMO antenna arrangement can be obtained.

[0538] A radar system according to one embodiment of the present disclosure, although not shown, includes, for example, a CPU (Central Processing Unit), a storage medium such as ROM (Read Only Memory) storing a control program, and working memory such as RAM (Random Access Memory). In this case, the functions of each of the above-mentioned parts are realized by the CPU executing the control program. However, the hardware configuration of the radar system is not limited to this example. For example, each functional part of the radar system may be realized as an integrated circuit (IC). Each functional part may be individually integrated into a single chip, or a part or all of them may be integrated into a single chip.

[0539] Although various embodiments have been described above with reference to the drawings, it goes without saying that this disclosure is not limited to such examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the disclosure.

[0540] Furthermore, the notation "...part" in the above-described embodiment may be replaced with other notations such as "...circuitry," "...assembly," "...device," "...unit," or "...module."

[0541] In the embodiments described above, the disclosure has been explained using examples configured with hardware, but the disclosure can also be implemented with software in conjunction with hardware.

[0542] Furthermore, each functional block used in the description of the above embodiments is typically implemented as an integrated circuit (LSI). The integrated circuit controls each functional block used in the description of the above embodiments and may have input and output terminals. These may be individually integrated into a single chip, or some or all of them may be integrated into a single chip. Here, we refer to it as an LSI, but depending on the degree of integration, it may also be called an IC, system LSI, super LSI, or ultra LSI.

[0543] Furthermore, the method of integrated circuit implementation is not limited to LSIs; it may also be implemented using dedicated circuits or general-purpose processors. After LSI manufacturing, FPGAs (Field Programmable Gate Arrays) that can be programmed, or reconfigurable processors that allow for the reconfiguration of the connections or settings of circuit cells inside the LSI, may also be used.

[0544] Furthermore, if advances in semiconductor technology or other derived technologies lead to the emergence of integrated circuit technologies that can replace LSIs, then naturally, functional blocks can be integrated using those technologies. The application of biotechnology, for example, is a possibility.

[0545] <Summary of this disclosure> A radar system according to one embodiment of the present disclosure comprises a plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam different from the first beam, and a transmitting circuit that multiplexes a transmission signal from the plurality of transmitting antennas, to which a phase rotation corresponding to a Doppler shift amount assigned to each of the plurality of transmitting antennas is applied, wherein the Doppler shift intervals of the plurality of transmitting antennas are unequal on the Doppler frequency axis, and a first pattern of Doppler shift amounts assigned to the first transmitting antenna and a second pattern of Doppler shift amounts assigned to the second transmitting antenna are different.

[0546] In one embodiment of the present disclosure, the first pattern and the second pattern are such that, with respect to the Doppler shift interval, the Doppler multiplexing number of the first transmitting antenna and the Doppler multiplexing number of the second transmitting antenna are the same, and at least one of the Doppler shift intervals of the first transmitting antenna is different from the Doppler shift interval of the second transmitting antenna.

[0547] In one embodiment of the present disclosure, the first pattern and the second pattern differ in the number of transmitting antennas, specifically in the number of the first transmitting antennas and the number of the second transmitting antennas.

[0548] In one embodiment of the present disclosure, the first pattern and the second pattern differ in terms of Doppler multiplexing numbers, with respect to the Doppler multiplexing number of the first transmitting antenna and the Doppler multiplexing number of the second transmitting antenna.

[0549] In one embodiment of the present disclosure, the first pattern and the second pattern are such that, with respect to the order of the intervals of the Doppler shift amounts, the Doppler multiplexing number by the first transmitting antenna and the Doppler multiplexing number by the second transmitting antenna are the same, the plurality of first Doppler shift intervals by the first transmitting antenna and the plurality of second Doppler shift intervals by the second transmitting antenna are the same, and the order of the plurality of first Doppler shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler shift intervals on the Doppler frequency axis.

[0550] In one embodiment of the present disclosure, the Doppler shift intervals by the first transmitting antenna are unequal on the Doppler frequency axis.

[0551] In one embodiment of the present disclosure, the Doppler shift intervals by the second transmitting antenna are unequal on the Doppler frequency axis.

[0552] One embodiment of the present disclosure further comprises a plurality of receiving antennas that receive reflected wave signals of the transmitted signal reflected by a target, and a receiving circuit that uses the reflected wave signals to estimate the direction of the target.

[0553] In one embodiment of the present disclosure, a plurality of receiving antennas are further provided, arranged at a first interval in a first direction, wherein the first transmitting antenna and the second transmitting antenna are arranged at a first interval in the first direction and at different positions in a second direction perpendicular to the first direction.

[0554] In one embodiment of the present disclosure, a plurality of receiving antennas are further provided, arranged at a first interval in a first direction, the first transmitting antenna and the second transmitting antenna are arranged at a second interval in the first direction, and the difference between the first interval and the second interval is a specified value based on the wavelength of the transmitted signal.

[0555] In one embodiment of the present disclosure, the specified value is any value in the range of 0.45 to 0.8 times the wavelength.

[0556] In one embodiment of the present disclosure, the first transmitting antenna and the second transmitting antenna are positioned at the same location in a second direction perpendicular to the first direction.

[0557] In one embodiment of the present disclosure, the first transmitting antenna and the second transmitting antenna are positioned at different locations in a second direction perpendicular to the first direction.

[0558] In one embodiment of the present disclosure, among the plurality of receiving antennas, the first receiving antenna and the second receiving antenna are arranged at different positions in the second direction.

[0559] In one embodiment of the present disclosure, the number of the first transmitting antenna and the second transmitting antenna is one, and the number of Doppler shift amounts assigned to the first transmitting antenna is different from the number of Doppler shift amounts assigned to the second transmitting antenna.

[0560] In one embodiment of the present disclosure, the number of Doppler shift amounts assigned to the first transmitting antenna and the number of Doppler shift amounts assigned to the second transmitting antenna are swapped with each transmission cycle of the transmitted signal.

[0561] In one embodiment of the present disclosure, the first beam and the second beam differ in at least one of their beam direction and beam width. [Industrial applicability]

[0562] This disclosure is suitable as a radar device for detecting a wide-angle range. [Explanation of symbols]

[0563] 10 Radar equipment 100 Radar Transmitter 101 Radar transmission signal generation unit 102 Modulated signal generation unit 103 VCO 104 Doppler Shift Section 105 Transmitting antenna section 200 Radar Receiver 201 Antenna System Processing Unit 202 Receiving antenna section 203 Receiving Radio Unit 204 Mixer Section 205 LPF 206 Signal Processing Unit 207 AD Conversion Unit 208 Beat Frequency Analysis Unit 209 Doppler Analysis Department 210 CFAR Department 211 Doppler multiplex separation unit 212 Direction estimation part

Claims

1. A plurality of transmitting antennas, including a first transmitting antenna that forms a first beam, and a second transmitting antenna that forms a second beam with a beam direction different from that of the first beam, A transmitting circuit that multiplexes and transmits from each of the multiple transmitting antennas a transmission signal to which a phase rotation corresponding to a Doppler shift amount assigned to each of the multiple transmitting antennas has been applied, It is equipped with, The Doppler shift intervals of the aforementioned multiple transmitting antennas are unequal on the Doppler frequency axis. The first pattern of Doppler shift amount assigned to the first transmitting antenna and the second pattern of Doppler shift amount assigned to the second transmitting antenna are different. The number of antennas in the first transmitting antenna is multiple, On the Doppler frequency axis, the Doppler shift intervals by the first transmitting antenna, which has multiple antennas, include unequal intervals. Radar device.

2. The first pattern and the second pattern are defined with respect to the Doppler shift interval. The Doppler multiplexing number of the first transmitting antenna and the Doppler multiplexing number of the second transmitting antenna are the same. At least one of the Doppler shift intervals provided by the first transmitting antenna is different from the Doppler shift interval provided by the second transmitting antenna. The radar device according to claim 1.

3. The first and second patterns relate to the number of transmitting antennas, The number of the first transmitting antennas and the number of the second transmitting antennas are different. The radar device according to claim 1.

4. The first and second patterns described above relate to the Doppler multiplexing number, The Doppler multiplexing number of the first transmitting antenna and the Doppler multiplexing number of the second transmitting antenna are different. The radar device according to claim 1.

5. A plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam in a beam direction different from the beam direction of the first beam, A transmitting circuit that multiplexes and transmits from each of the multiple transmitting antennas a transmission signal to which a phase rotation corresponding to a Doppler shift amount assigned to each of the multiple transmitting antennas has been applied, It is equipped with, The Doppler shift intervals of the aforementioned multiple transmitting antennas are unequal on the Doppler frequency axis. The first pattern of Doppler shift amount assigned to the first transmitting antenna and the second pattern of Doppler shift amount assigned to the second transmitting antenna are different. The first pattern and the second pattern relate to the order of the intervals of the Doppler shift amounts, The Doppler multiplexing number of the first transmitting antenna and the Doppler multiplexing number of the second transmitting antenna are the same. The plurality of first Doppler shift intervals by the first transmitting antenna and the plurality of second Doppler shift intervals by the second transmitting antenna are the same, The order of the plurality of first Doppler shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler shift intervals on the Doppler frequency axis. Radar device.

6. The number of antennas of the second transmitting antenna is multiple, On the Doppler frequency axis, the Doppler shift intervals by the second transmitting antenna, which has multiple antennas, include unequal intervals. The radar device according to claim 1.

7. Multiple receiving antennas that receive the reflected wave signal that the transmitted signal has reflected off the target, A receiving circuit that uses the reflected wave signal to estimate the direction of the target, It further possesses, The radar device according to claim 1.

8. The system further comprises a plurality of receiving antennas arranged at first intervals in a first direction, The first transmitting antenna and the second transmitting antenna are arranged at a first interval in the first direction and at different positions in a second direction perpendicular to the first direction. The radar device according to claim 1.

9. The system further comprises a plurality of receiving antennas arranged at first intervals in a first direction, The first transmitting antenna and the second transmitting antenna are arranged in the first direction at a second interval, The difference between the first interval and the second interval is a specified value based on the wavelength of the transmitted signal. The radar device according to claim 1.

10. The specified value is any value within the range of 0.45 to 0.8 times the wavelength. The radar device according to claim 9.

11. The first transmitting antenna and the second transmitting antenna are positioned at the same location in a second direction perpendicular to the first direction. The radar device according to claim 9.

12. The first transmitting antenna and the second transmitting antenna are positioned at different locations in a second direction perpendicular to the first direction. The radar device according to claim 9.

13. Of the plurality of receiving antennas, the first receiving antenna and the second receiving antenna are positioned at different locations in a second direction perpendicular to the first direction. The radar device according to claim 8 or 9.

14. A plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam in a beam direction different from the beam direction of the first beam, A transmitting circuit that multiplexes and transmits from each of the multiple transmitting antennas a transmission signal to which a phase rotation corresponding to a Doppler shift amount assigned to each of the multiple transmitting antennas has been applied, It is equipped with, The Doppler shift intervals of the aforementioned multiple transmitting antennas are unequal on the Doppler frequency axis. The first pattern of Doppler shift amount assigned to the first transmitting antenna and the second pattern of Doppler shift amount assigned to the second transmitting antenna are different. The number of the first transmitting antenna and the second transmitting antenna is one. The number of Doppler shift amounts assigned to the first transmitting antenna is different from the number of Doppler shift amounts assigned to the second transmitting antenna. Radar device.

15. The number of Doppler shift amounts assigned to the first transmitting antenna and the number of Doppler shift amounts assigned to the second transmitting antenna are swapped with each transmission cycle of the transmitted signal. The radar device according to claim 12.

16. The first beam and the second beam have different beam widths. The radar device according to claim 1.

17. A signal generation circuit that generates a transmission signal, A transmitting circuit that applies a phase rotation to the transmitting signal corresponding to a Doppler shift amount assigned to each of a plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam with a beam direction different from the beam direction of the first beam, and multiplexes the transmitted signal to which the phase rotation has been applied from the plurality of transmitting antennas, It is equipped with, The Doppler shift intervals of the aforementioned multiple transmitting antennas are unequal on the Doppler frequency axis. The first pattern of Doppler shift amount assigned to the first transmitting antenna and the second pattern of Doppler shift amount assigned to the second transmitting antenna are different. The first pattern and the second pattern relate to the order of the intervals of the Doppler shift amounts, The Doppler multiplexing number of the first transmitting antenna and the Doppler multiplexing number of the second transmitting antenna are the same. The plurality of first Doppler shift intervals by the first transmitting antenna and the plurality of second Doppler shift intervals by the second transmitting antenna are the same, The order of the plurality of first Doppler shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler shift intervals on the Doppler frequency axis. Radar signal generator.

18. Generate a transmission signal, A phase rotation corresponding to a Doppler shift amount assigned to each of a plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam with a beam direction different from that of the first beam, is applied to the transmitting signal. The transmission signal to which the phase rotation has been applied is multiplexed and transmitted from the plurality of transmitting antennas. The Doppler shift intervals of the aforementioned multiple transmitting antennas are unequal on the Doppler frequency axis. The first pattern of Doppler shift amount assigned to the first transmitting antenna and the second pattern of Doppler shift amount assigned to the second transmitting antenna are different. The first pattern and the second pattern relate to the order of the intervals of the Doppler shift amounts, The Doppler multiplexing number of the first transmitting antenna and the Doppler multiplexing number of the second transmitting antenna are the same. The plurality of first Doppler shift intervals by the first transmitting antenna and the plurality of second Doppler shift intervals by the second transmitting antenna are the same, The order of the plurality of first Doppler shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler shift intervals on the Doppler frequency axis. Radar signal generation method.

19. A signal generation circuit that generates a transmission signal, A transmitting circuit that applies a phase rotation to the transmitting signal corresponding to a Doppler shift amount assigned to each of a plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam with a beam direction different from the beam direction of the first beam, and multiplexes the transmitted signal to which the phase rotation has been applied from the plurality of transmitting antennas, It is equipped with, The Doppler shift intervals of the aforementioned multiple transmitting antennas are unequal on the Doppler frequency axis. The first pattern of Doppler shift amount assigned to the first transmitting antenna and the second pattern of Doppler shift amount assigned to the second transmitting antenna are different. The number of the first transmitting antenna and the second transmitting antenna is one. The number of Doppler shift amounts assigned to the first transmitting antenna is different from the number of Doppler shift amounts assigned to the second transmitting antenna. Radar signal generator.

20. Generate a transmission signal, A phase rotation corresponding to a Doppler shift amount assigned to each of a plurality of transmitting antennas, including a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam with a beam direction different from that of the first beam, is applied to the transmitting signal. The transmission signal to which the phase rotation has been applied is multiplexed and transmitted from the plurality of transmitting antennas. The Doppler shift intervals of the aforementioned multiple transmitting antennas are unequal on the Doppler frequency axis. The first pattern of Doppler shift amount assigned to the first transmitting antenna and the second pattern of Doppler shift amount assigned to the second transmitting antenna are different. The number of the first transmitting antenna and the second transmitting antenna is one. The number of Doppler shift amounts assigned to the first transmitting antenna is different from the number of Doppler shift amounts assigned to the second transmitting antenna. Radar signal generation method.

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