Radar device, radar signal transmission method, and radar signal reception method

Abstract

A radar device is provided with: a plurality of transmission antennas including a first transmission antenna that radiates a first polarized wave and a second transmission antenna that radiates a second polarized wave different from the first polarized wave; and a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, a transmission signal to which a phase rotation amount corresponding to a combination of the Doppler shift amount and the code sequence is applied. For each of the plurality of transmission antennas, a first pattern of the Doppler shift amount and the code sequence allocated to the first transmission antenna differs from a second pattern of the Doppler shift amount and the code sequence allocated to the second transmission antenna, respectively corresponding to a different combination of the Doppler shift amount and at least one of the code sequences.

Description

Technical Field

[0001] The present disclosure relates to a radar device, a method for transmitting a radar signal, and a method for receiving a radar signal. Background Art

[0002] In recent years, research has been progressing on radar devices that use short-wavelength radar transmission signals including microwaves or millimeter waves that can achieve high resolution. For example, the following structure has been proposed as a radar device (sometimes also referred to as "MIMO (Multiple Input Multiple Output) radar"): In addition to the receiving unit, the transmitting unit also has multiple antennas (array antennas), and beam scanning is performed by signal processing using the transmitting and receiving array antennas (for example, refer to Non-Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: U.S. Patent Publication No. 2019 / 0064337

[0006] Patent Document 2: U.S. Patent Publication No. 2020 / 0363497

[0007] Patent Document 3: Japanese Patent Application Publication No. 2008-304417

[0008] Patent Document 4: Japanese Patent Application No. 2011-526371

[0009] Patent Document 5: Japanese Patent Application Publication No. 2011-119344

[0010] Patent Document 6: Japanese Patent Application Publication No. 2020-204603

[0011] Patent Document 7: Japanese Patent Application Publication No. 2020-092247

[0012] Patent Document 8: Japanese Patent Application Publication No. 2020-148754

[0013] Non-patent literature

[0014] 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

[0015] Non-patent document 2: M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823

[0016] Non-patent literature 3: Direction-of-arrival estimation using signal subspacemodeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1 Publication Year: 1992, Page (s): 64-79 Summary of the invention

[0017] However, a method for detecting a target (or object) using a radar device (eg, MIMO radar) has not been fully studied.

[0018] The non-limiting embodiments of the present disclosure are helpful to provide a radar device, a method for transmitting a radar signal, and a method for receiving a radar signal that improve the detection accuracy of a target object.

[0019] A radar device according to an embodiment of the present disclosure includes: a plurality of transmitting antennas, including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmitting signals to which a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and a code sequence is assigned, wherein for each of the plurality of transmitting antennas, there corresponds a different combination of at least one of the Doppler frequency shift amount and the code sequence, and a first pattern of the Doppler frequency shift amount and the code sequence assigned to the first transmitting antenna is different from a second pattern of the Doppler frequency shift amount and the code sequence assigned to the second transmitting antenna.

[0020] In addition, these broad or specific embodiments may be implemented by systems, devices, methods, integrated circuits, computer programs or recording media, or by any combination of systems, devices, methods, integrated circuits, computer programs and recording media.

[0021] According to an embodiment of the present disclosure, the detection accuracy of a target object of a radar device can be improved.

[0022] Further advantages and effects in one embodiment of the present disclosure will be clearly presented by the description and the drawings. The above advantages and / or effects are provided by several embodiments and the features described in the description and the drawings, but not necessarily all of them are provided in order to obtain one or more of the same features. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0024] Figure 2 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing.

[0025] Figure 3 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0026] Figure 4 This is a block diagram showing a configuration example of a radar device.

[0027] Figure 5 This is a diagram showing an example of a transmission signal when a chirp signal is used.

[0028] Figure 6 It is a diagram showing an example of setting the Doppler shift amount and the code sequence.

[0029] Figure 7 FIG. 1 is a diagram showing a setting example of a code Doppler phase rotation amount.

[0030] Figure 8 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing.

[0031] Fig. 9 FIG. 1 is a diagram showing a setting example of a code Doppler phase rotation amount.

[0032] Fig.10 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing.

[0033] Fig.11 FIG. 1 is a diagram showing a setting example of a code Doppler phase rotation amount.

[0034] Fig.12 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing.

[0035] Fig.13 FIG. 1 is a diagram showing a setting example of a code Doppler phase rotation amount.

[0036] Fig.14 This is a flowchart showing an example of the operation of demultiplexing a coded Doppler multiplexed signal.

[0037] Fig.15This is a block diagram showing a configuration example of a radar receiving unit.

[0038] Fig.16 FIG. 1 is a diagram showing a setting example of a code Doppler phase rotation amount.

[0039] Fig.17 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing. DETAILED DESCRIPTION

[0040] [About Polarimetric Radar]

[0041] For example, there is a technology that improves radar detection performance or recognition performance by using antennas that radiate radio waves of different polarizations or antennas that receive radio waves of different polarizations (for example, see Patent Document 1 or Patent Document 2). Radar devices that use multiple polarized waves are also called "polarimetric radars".

[0042] For example, Patent Document 1 or Patent Document 2 discloses a method in which a transmission signal is transmitted using an antenna using a vertically polarized wave or a horizontally polarized wave, and an object is detected and identified using a signal received by the antenna using the vertically polarized wave or the horizontally polarized wave. In addition, Patent Document 1 discloses a method in which, for example, a transmission signal is transmitted using an antenna using a left-hand circularly polarized wave or a right-hand circularly polarized wave, and an object is detected and identified using a signal received by the antenna using the left-hand circularly polarized wave or the right-hand circularly polarized wave. In addition, an antenna using polarized waves such as linearly polarized waves including vertically polarized waves and horizontally polarized waves, or circularly polarized waves including left-hand circularly polarized waves and right-hand circularly polarized waves is also referred to as a "polarized antenna."

[0043] Such a polarization radar uses a plurality of different kinds of polarization antennas (eg, polarization transmission antennas or polarization reception antennas).

[0044] Next, the multiplexing transmission method in a MIMO radar using a plurality of polarization antennas of different types (for example, also referred to as a “polarization MIMO radar”) will be described.

[0045] For example, as examples of multiplexing transmission methods of MIMO radar using multiple transmitting antennas, time division multiplexing (TDM) transmission (for example, refer to Patent Documents 3 and 4) and Doppler multiplexing (DDM) transmission (for example, refer to Patent Document 5) can be cited.

[0046] In time division multiplexing transmission or Doppler multiplexing transmission, the reflected waves corresponding to the transmission signals from multiple transmission antennas can be demultiplexed using the allocated transmission time or Doppler frequency domain. On the other hand, in time division multiplexing transmission and Doppler multiplexing transmission, if the number of transmission antennas increases, the detection range of the Doppler frequency tends to become smaller. For example, in time division multiplexing and Doppler division multiplexing, the detectable Doppler frequency range is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr), and the detection range of the Doppler frequency decreases inversely proportional to the number of transmission antennas. Here, Nt is the number of transmission antennas, and Tr is the transmission period of the transmission signal.

[0047] [About Coded Doppler Multiplexing Transmission]

[0048] Patent Document 6 (for example, Figure 1 ) discloses a multiplexing transmission method that combines Doppler multiplexing and code multiplexing (hereinafter referred to as "coded Doppler multiplexing transmission" or "Coded DDM transmission (abbreviated as CDDM transmission)").

[0049] For example, Figure 1 This shows a case where a radar transmission wave (for example, a chirp signal) is transmitted at a transmission period Tr. Figure 1 An example of the allocation of transmission Doppler frequencies and codes when the signal after code multiplexing with orthogonal codes (e.g., code#1, code#2) of code length Loc=2 is transmitted using two Doppler multiplexing (DDM) signals (e.g., DOP1, DOP2) for three transmitting antennas (e.g., Tx#1 to Tx#3). Figure 1 In the example, the code multiplexing number N CM =2, Doppler multiplexing number N DM =2.

[0050] For example, the code length is times the transmission period Loc×Tr (in Figure 1 The chirp signal is repeatedly assigned in a cycle of 2 transmission cycles (2Tr) to perform phase rotation based on the code. At this time, it is assumed that the code length Loc is assigned in a transmission cycle of code length times (in Figure 1 In the case where the phase rotation based on the DDM signal is constant during the 2 transmission cycles (2Tr), for example, the phase rotation based on the DDM signal may be varied every 2Tr transmission cycle and given.

[0051] For example, in Figure 1In the example, the allocated transmit Doppler frequency shift amounts are set to DOP1=0 and DOP2=-1 / (4Tr)[Hz]. For example, since DOP1 is assigned to each m-th transmit cycle, the radar transmit wave (chirp signal) is assigned a phase rotation of Φ1(m)=ΔΦ1×(floor(m / Loc)+1). In addition, since DOP2 is assigned to each m-th transmit cycle, the radar transmit wave is assigned a phase rotation of Φ2(m)=ΔΦ2×(floor(m / Loc)+1). Here, ΔΦ1=0 and ΔΦ2=-π. Doppler multiplexing interval Δf d =1 / (4Tr). In addition, for example, Code1 = [1, 1] and Code2 = [1, -1] can be used as orthogonal codes with a code length of 2. Figure 1 For example, as a coded Doppler multiplexed signal (CDDM signal) combining a Doppler multiplexed signal and a code, DopCode#1=(DOP2, Code1), DopCode#2=(DOP2, Code2), and DopCode#3=(DOP1, Code1) are assigned to Tx#1 to Tx#3, respectively, and transmitted. In addition, floor[x] is a function that outputs the largest integer that does not exceed the real number x.

[0052] Here, DopCode#n indicates the allocation of the CDDM signal for the nth Tx#n (indicating the use of the Doppler frequency shift amount DOP ndm Code ncm where n=1~Nt, ndm is 1~N DM An integer value in the range of , ncm is 1 to N CM DOP is assigned to Nt transmitting antennas. ndm With Code ncm Combination of different CDDM signals.

[0053] These signals multiplexed and transmitted simultaneously are received in a radar device (e.g., a received signal processing unit). For example, the radar device distinguishes the radar reflected wave received signal according to each received signal of each transmitted code element, performs Doppler frequency analysis in a separate Doppler analysis unit (e.g., V-FFT#1, #2, ..., #Loc), and performs code multiplexing demultiplexing and Doppler multiplexing demultiplexing based on the output of the Doppler frequency analysis, thereby demultiplexing the multiplexed transmission signal and receiving it. For example, when the code length Loc=2, the number of code elements is 2, and the radar device performs code multiplexing demultiplexing and Doppler multiplexing demultiplexing based on the output of the Doppler frequency analysis performed on the received signals of each odd-numbered transmission signal and each even-numbered transmission signal in a separate Doppler analysis unit (V-FFT#1, #2), thereby demultiplexing the multiplexed transmission signal and receiving it.

[0054] Here, the transmission period (in Figure 1 In the example, Loc = 2, so the received signal is 2 transmission cycles (2Tr)), so it exceeds ±1 / (2Loc Tr) (in Figure 1 For example, as disclosed in Patent Document 6, by multiplexing and transmitting from a plurality of transmitting antennas in such a way that the code multiplexing number between DDM signals is uneven, it is possible to detect whether a component of a frequency range of aliasing is included in the radar reflected wave reception signal. As a result, the radar device can expand the Doppler frequency range (maximum Doppler) in which the Doppler frequency can be detected without aliasing to ±1 / (2Tr), and can determine the transmitting antenna.

[0055] For example, in Figure 1 In the example, the code multiplexing number of the Doppler frequency shift amount DOP1 is 1, and the code multiplexing number of DOP2 is 2, and the code multiplexing number is set unevenly between the DDM signals. The radar device uses a CDDM signal (in Figure 1 In the above method, DopCode=(DOP1, Code2) is used to detect whether a component in a frequency range of aliasing is included in the radar reflected wave reception signal based on the demultiplexed reception signal of the multiplexed transmitted signal (hereinafter also referred to as "aliasing determination").

[0056] For example, Figure 2 (a) indicates Figure 1 The CDDM signal shown is at the Doppler frequency f of the target. dtg = 0, the received Doppler signal when demultiplexed with Code1 and Code2 respectively. In the received DDM signal demultiplexed with Code1, the reception level at two Doppler frequencies is detected to be higher, and the interval between the two Doppler frequencies is the same as the Doppler multiplexing interval Δf of DOP1 and DOP2. d The radar device can judge these components as the received signals of Tx#1 and Tx#3. In addition, in the received Doppler signal demultiplexed by Code2, the received Doppler frequency f d = -1 / (4Tr), a Doppler frequency with a high reception level is detected. In addition, the Doppler multiplexing interval Δf with DOP1 and DOP2 is d Doppler frequencies with consistent Doppler frequency spacing (receive Doppler frequency f d =0) is the noise level.

[0057] Therefore, in Figure 2In (a), the radar device can determine that a component of a Doppler frequency with a high reception level detected in the received Doppler signal demultiplexed by Code 2 is the received signal of Tx#2. In addition, since the deviation amount relative to the Doppler frequency shift amount when each transmitting antenna is transmitted is the Doppler frequency of the target object, the radar device can determine the Doppler frequency of the target object.

[0058] In addition, for example, Figure 2 (b) indicates that Figure 1 The CDDM signal shown is at the Doppler frequency f of the target. dtg = -1 / (2Tr), the received Doppler signals when demultiplexed with Code1 and Code2 respectively. In the received Doppler signal demultiplexed with Code2, the received levels at two Doppler frequencies are detected to be higher, and the interval between the two Doppler frequencies is the same as the Doppler multiplexing interval Δf of DOP1 and DOP2. d The radar device can judge these components as the received signals of Tx#1 and Tx#3. In addition, a Doppler frequency with a high reception level is detected in the received Doppler signal demultiplexed with Code1. In addition, with respect to the detected Doppler frequency, the Doppler multiplexing interval Δf of DOP1 and DOP2 is d Doppler frequencies with consistent Doppler frequency spacing (receive Doppler frequency f d =0) is the noise level.

[0059] Therefore, in Figure 2 In (b), the radar device can determine that a component of a Doppler frequency with a high reception level detected in the received Doppler signal demultiplexed by Code 1 is the received signal of Tx#2. In addition, since the deviation amount relative to the Doppler frequency shift amount when each transmitting antenna is transmitted is the Doppler frequency of the target object, the radar device can determine the Doppler frequency of the target object.

[0060] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), aliased Doppler frequencies are observed in the Doppler analysis unit (e.g., V-FFT#1 and V-FFT#2). The actual Doppler frequency has a phase difference of 2π with respect to the Doppler frequency detected in the Doppler analysis unit (V-FFT#1 and V-FFT#2) during the transmission period of 2Tr, so there is a phase rotation of π during the detection time difference Tr between V-FFT#1 and V-FFT#2. Therefore, when the code length Loc=2, in the case of Figure 2As shown in (b) of FIG. 1 , when a received signal corresponding to Code 2 is determined in the demultiplexing of Code 1, the radar apparatus can determine that there is aliasing of the Doppler frequency.

[0061] By performing such demultiplexing reception processing on the CDDM signal, the radar device can estimate the Doppler frequency of the radar reflected wave in the Doppler frequency range of ±1 / (2Tr). In this way, by performing CDDM transmission, the detectable Doppler frequency range is expanded to ±1 / 2Tr. For example, compared with Patent Document 5, the detectable Doppler frequency range is expanded to Nt times.

[0062] [Application of Coded Doppler Multiplexing (CDDM) Transmission in Polarization MIMO Radar]

[0063] As described above, the MIMO radar using coded Doppler multiplexing performs demultiplexing processing (hereinafter referred to as "coded Doppler multiplexing demultiplexing" or "CDDM demultiplexing") of the CDDM signal for estimating the Doppler frequency of the target object based on the received power of the received Doppler frequency after code demultiplexing of the reflected wave from the target object.

[0064] Therefore, in the case of applying CDDM to polarization MIMO radar, the following situation can be envisaged.

[0065] In polarization MIMO radar, for example, a phenomenon may occur in which the reception level of reflected waves varies greatly depending on the polarization of the transmitting and receiving antennas. In polarization MIMO radar, when using transmitting antennas with different polarizations, the reception level of reflected waves from transmitting antennas with other polarizations may be greatly attenuated relative to the reception level of reflected waves from transmitting antennas with a certain polarization. Therefore, in polarization MIMO radar, when CDDM is used for multiplexing transmission, CDDM demultiplexing may become difficult due to the large difference (or ratio of levels) in the reception level of reflected waves between transmitting antennas with different polarizations. If CDDM demultiplexing becomes difficult, the detection performance of the target object in the MIMO radar may be degraded, or CDDM demultiplexing errors, Doppler misestimation, or degraded angle measurement performance may occur.

[0066] Next, an example in which demultiplexing of CDDM is difficult in a polarization MIMO radar to which CDDM is applied will be described.

[0067] Here, as an example, a case where two transmitting antennas are used for each of left-hand circular polarization (hereinafter, also expressed as "LC") and right-hand circular polarization (hereinafter, also expressed as "RC") to form a MIMO radar (expressed as LC-2Tx and RC-2Tx, respectively) is described (for example, the number of transmitting antennas Nt=4). The polarized antenna corresponding to left-hand circular polarization is called an "LC polarized antenna" (for example, an LC polarized transmitting antenna or an LC polarized receiving antenna), and the polarized antenna corresponding to right-hand circular polarization is called an "RC polarized antenna" (for example, an RC polarized transmitting antenna or an RC polarized receiving antenna).

[0068] For example, the case where a MIMO radar uses an LC polarized receiving antenna to receive a primary reflected wave (a reflected wave that is reflected once by an object) is described. The reflected wave signal corresponding to the transmitted signal from the RC polarized transmitting antenna (for example, also referred to as "the received signal corresponding to the RC polarized transmitting antenna") becomes a received signal as an RC polarized wave, and when the received signal corresponding to the RC polarized transmitting antenna is received by the LC polarized receiving antenna, it becomes a reception under cross-polarization. Therefore, in the LC polarized receiving antenna, the received level of the received signal corresponding to the RC polarized transmitting antenna becomes a smaller received level (depending on the cross-polarization discrimination of the antenna, for example, a received level that is smaller by more than 10 dB). For example, depending on the reception quality (for example, signal-to-noise ratio (SNR)), the received level of the received signal corresponding to the RC polarized transmitting antenna may become below the noise level, making it difficult to detect the Doppler frequency peak in the MIMO radar.

[0069] Figure 3 is a diagram showing an example of a signal transmitted by CDDM in a polarization MIMO radar. Figure 3 In the example, as transmitting antennas with different polarizations, two LC polarized transmitting antennas and two RC polarized transmitting antennas are used, for a total of four Tx#1 to #4 to form a MIMO radar. Here, it is assumed that Tx#1 and Tx#2 are transmitting antennas with LC polarization, and Tx#3 and Tx#4 are transmitting antennas with RC polarization. In addition, Figure 3 In the example, the receiving antenna uses an LC polarized receiving antenna for reception.

[0070] For example, Figure 3 As shown in (a), the Doppler multiplexing number N is allocated to the four Tx#1 to #4. DM =3, code multiplexing number N CM= 2. In CDDM, different sets of a DDM signal (one of DOP1, DOP2, and DOP3) and a code (one of Code1 and Code2) are allocated to each transmission antenna.

[0071] In addition, Figure 3 In FIG. 1 , the black circles (●) represent the allocation of CDDM signals to the LC polarized transmitting antennas (Tx#1 and Tx#2), and the groups of DopCode#1=(DOP1, Code1) and DopCode#2=(DOP2, Code1) are allocated to Tx#1 and Tx#2, respectively. Figure 3 In the figure, white circles (○) represent the allocation of CDDM signals of RC polarized transmitting antennas (Tx#3 and Tx#4), and the groups of DopCode#3=(DOP3, Code2) and DopCode#4=(DOP1, Code2) are allocated to Tx#3 and Tx#4 respectively.

[0072] For example, in Figure 3 When the CDDM signal is distributed as shown in (a), the LC polarized receiving antenna may have the following problems when receiving the primary reflected wave: Figure 3 As shown in (b), the reception level of the reception signal (R) corresponding to the RC polarized transmission antenna is smaller than that of the reception signal (L) corresponding to the LC polarized transmission antenna.

[0073] Here, in Figure 3 In the figure, the size of the black circle (●) and the white circle (○) indicates the received power. If the size of the black circle (●) and the white circle (○) is smaller, it means that the received power is smaller (for example, the received power is as small as the noise level).

[0074] In addition, the case where the MIMO radar uses an LC polarized receiving antenna to receive, for example, a secondary reflected wave (a reflected wave that is reflected twice by an object) is described. Since the received signal corresponding to the LC polarized transmitting antenna received in the LC polarized receiving antenna is a secondary reflection, the received signal changes from an LC polarized wave to an RC polarized wave, and the reception by the LC polarized receiving antenna becomes a reception under cross-polarization. Therefore, compared with the received signal corresponding to the RC polarized transmitting antenna, the level of the received signal corresponding to the LC polarized transmitting antenna becomes a smaller receiving level (depending on the cross-polarization discrimination of the antenna and, for example, a receiving level that is 10 dB or more smaller). For example, depending on the reception quality (SNR), the reception level of the received signal corresponding to the LC polarized transmitting antenna may become below the noise level, making it difficult to detect the Doppler frequency peak in the MIMO radar.

[0075] For example, in Figure 3 When the CDDM signal is distributed as shown in (a) of FIG. 1 and the secondary reflected wave is received by the LC polarized receiving antenna, it is possible as shown in FIG. Figure 3 As shown in (c), the reception level of the reception signal (L) corresponding to the LC polarized transmission antenna is smaller than that of the reception signal (R) corresponding to the RC polarized transmission antenna.

[0076] Here, if the Doppler frequency of the reflected wave from the target and the number of reflections are not known in advance, it is difficult to use MIMO radar based on Figure 3 The reception level shown in (b) or (c) of FIG. 1 can be used to determine whether the reception level of the reception signal corresponding to the RC polarized transmission antenna has decreased or the reception level of the reception signal corresponding to the LC polarized transmission antenna has decreased. In addition, for example, it is difficult for MIMO radar to be based on Figure 3 The received level shown in (b) or (c) of FIG. 1 is used to determine which transmitting antenna used in CDDM transmission corresponds to the peak value of the detected Doppler frequency. Therefore, it is difficult for MIMO radar to demultiplex CDDM signals and it is difficult to keep -1 / (2Tr) ≤ f dtg The range of <1 / (2Tr) determines the Doppler frequency f of the reflected wave from the target object (for example, referred to as “target reflected wave”). dtg .

[0077] For example, the target reflected wave is a single reflected wave and the Doppler frequency is f dtg = 0 (the reception level of the received signal corresponding to the RC polarized transmitting antenna is reduced to the level of the noise level Figure 3 (b) in the upper part of the case i), and the target reflected wave is a secondary reflection and the Doppler frequency f dtg = -1 / (2Tr) + Δfd (the case where the reception level of the received signal corresponding to the LC polarized transmission antenna drops to the level of the noise level), in both cases, peak frequencies are observed at DOP1 and DOP2 in the reception Doppler frequency after code demultiplexing with Code 1. Therefore, the results of CDDM demultiplexing in these cases will not be unique responses, and it is difficult for the radar device to distinguish these cases.

[0078] Thus, in the coded Doppler multiplexing MIMO radar, the demultiplexing process of the multiplexed transmission signal is performed on the premise that the reception level of the CDDM signal assigned to each transmission antenna is about the same and the reception level of the coded Doppler signal not assigned to the transmission antenna is sufficiently low and as low as the noise level. Figure 3 As shown in (b) and (c), the premise of CDDM demultiplexing processing does not hold, resulting in possible errors in CDDM demultiplexing processing.

[0079] In a non-limiting embodiment of the present disclosure, a method of improving the detection performance of a polarization MIMO radar using coded Doppler multiplexing (CDDM) transmission is described.

[0080] In addition, an example is described here in which a MIMO radar is constructed using two transmitting antennas for each of left-hand circular polarization (LC) and right-hand circular polarization (RC) (for example, the number of transmitting antennas Nt=4), but the polarization used in the polarization MIMO radar is not limited to this.

[0081] For example, in polarization MIMO radar, different linear polarizations that are orthogonal to each other can also be applied. For example, vertical polarization can be applied instead of left-hand circular polarization (LC), and horizontal polarization can be applied instead of right-hand circular polarization (RC), that is, linear polarizations that are orthogonal to each other can be applied. When radar transmission waves are transmitted using such vertically polarized and horizontally polarized transmitting antennas, the closer the incident angle of the radar transmission wave when it is reflected at the target is to the Brewster angle, the more likely it is that the reflected wave of one of the vertical polarization and horizontal polarization has a weaker reception level than the reflected wave of the other polarization. In MIMO radar, for example, when such reflected waves are received using a polarization receiving antenna corresponding to one of the vertical polarization and horizontal polarization, it is possible that the received signal of the polarization transmitting antenna corresponding to one of the vertical polarization and horizontal polarization becomes a reception under cross polarization, so that the received level is a lower received level (depending on the cross polarization discrimination of the antenna and being, for example, a reception level that is 10 dB or more lower) than the received signal of the polarization transmitting antenna corresponding to the other. Depending on the reception quality (SNR), a received signal whose reception level has been reduced may fall below the noise level, making it difficult to detect a Doppler frequency peak in a MIMO radar.

[0082] For example, vertical polarization is applied instead of left-hand circular polarization (LC), and horizontal polarization is applied instead of right-hand circular polarization (RC), such as Figure 3 If the CDDM signal is distributed as in (a), it is possible that Figure 3 (b) or Figure 3 The received signal is as shown in (c).

[0083] The same is true when using vertically polarized and horizontally polarized transmitting antennas. For example, it is difficult for MIMO radar to Figure 3The reception level shown in (b) or (c) of FIG. 1 can be used to determine whether the reception level of the transmission signal sent by the horizontal polarization transmission antenna has decreased or the reception level of the transmission signal sent by the vertical polarization transmission antenna has decreased. Therefore, it is difficult for MIMO radar to demultiplex CDDM signals, for example, and it is difficult to determine the Doppler frequency fd of the target reflection wave in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0084] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the embodiments, the same components are given the same reference numerals, and their descriptions are omitted to avoid duplication.

[0085] The following describes a structure (for example, a MIMO radar structure) in which a radar device simultaneously sends out different multiplexed transmission signals from a plurality of transmission antennas in a transmission branch, and demultiplexes each transmission signal in a reception branch to perform reception processing.

[0086] In addition, as an example, the following describes a radar method that uses a frequency-modulated pulse wave such as a chirp pulse (for example, also referred to as "fast chirp modulation"). However, the modulation method is not limited to frequency modulation. For example, one embodiment of the present disclosure may also be applied to a radar method that uses a pulse compression radar that transmits a pulse train by phase modulation or amplitude modulation.

[0087] In addition, the radar device performs Doppler multiplexing transmission, for example. In addition, the radar device performs encoding (for example, CDM (Code Division Multiplexing)) of signals to which different phase rotations (for example, phase shifts) equal to the number of Doppler multiplexing (hereinafter also referred to as "Doppler multiplexing (DDM) transmission signals" or "Doppler multiplexing (DDM) signals") are given, and multiplexes and transmits (hereinafter referred to as "Coded Doppler Division Multiplexing (CCDM)").

[0088] [Structure of radar device]

[0089] Figure 4 The radar device 10 includes a radar transmitting unit (transmitting branch) 100 and a radar receiving unit (receiving branch) 200 .

[0090] The radar transmitting unit 100 generates a radar signal (radar transmission signal) and uses a transmitting antenna unit 109 (e.g., a transmitting array antenna) composed of multiple transmitting antennas (e.g., Nt) to transmit the radar transmission signal at a predetermined transmission period (hereinafter referred to as "radar transmission period").

[0091] The radar receiving unit 200 uses a receiving antenna unit 202 (e.g., a receiving array antenna) including a plurality of receiving antennas 202-1 to 202-Na to receive a radar transmission signal, i.e., a reflected wave signal, which is reflected by a target (not shown). The radar receiving unit 200 performs signal processing on the reflected wave signal received by each receiving antenna, such as detecting the presence of a target or estimating the arrival distance, Doppler frequency (e.g., relative speed), and arrival direction of the reflected wave signal, and outputs information related to the estimation result (e.g., positioning information).

[0092] In addition, the radar device 10 can be mounted on a mobile object such as a vehicle, and the positioning output (information related to the estimation result) from the radar receiving unit 200 can also be connected to a control device ECU (Electronic Control Unit) (not shown) such as an advanced driver assistance system (ADAS) or an automatic driving system that improves collision safety, for vehicle drive control or alarm call control.

[0093] In addition, the radar device 10 can be installed on a higher structure such as a roadside electric pole or a traffic light (not shown). In addition, the radar device 10 can also be used as a sensor in an auxiliary system for improving the safety of passing vehicles or pedestrians or a system to prevent suspicious people from breaking into the road (not shown). In addition, the positioning output of the radar receiving unit 200 can also be connected to a control device (not shown) in an auxiliary system for improving safety or a system to prevent suspicious people from breaking into the road, for example, for alarm call control or abnormality detection control. In addition, the use of the radar device 10 is not limited to this, and it can also be used for other purposes.

[0094] The target object is an object to be detected by the radar device 10 , and includes, for example, a vehicle (including four-wheeled and two-wheeled vehicles), a person, a rock, a curb, and the like.

[0095] [Configuration of Radar Transmitting Unit 100]

[0096] The radar transmitting unit 100 includes a radar transmission signal generating unit 101 , a phase rotation amount setting unit 105 , a phase rotation unit 108 , and a transmission antenna unit 109 .

[0097] The radar transmission signal generating unit 101 generates a radar transmission signal. The radar transmission signal generating unit 101 includes, for example, a transmission signal generation control unit 102, a modulation signal generating unit 103, and a VCO (Voltage Controlled Oscillator) 104. The following describes each component of the radar transmission signal generating unit 101.

[0098] The transmission signal generation control unit 102 sets the transmission signal generation timing of each radar transmission cycle, for example, and outputs information related to the set transmission signal generation timing to the modulation signal generation unit 103 and the phase rotation amount setting unit 105 (for example, the Doppler shift setting unit 106). Here, the radar transmission cycle is set to Tr.

[0099] The modulated signal generation unit 103 periodically generates a modulated signal having, for example, a sawtooth shape, based on information on the transmission signal generation timing of each radar transmission cycle Tr input from the transmission signal generation control unit 102 .

[0100] The VCO 104 generates a frequency modulation signal (hereinafter, for example, referred to as a frequency chirp signal or a chirp signal) based on the modulation signal input from the modulation signal generator 103. Figure 5 The radar transmission signal (radar transmission wave) shown is output to the phase rotation unit 108 and the radar reception unit 200 (mixer unit 204 described later).

[0101] The phase rotation amount setting unit 105 sets the phase rotation amount (for example, the phase rotation amount corresponding to CDDM transmission) given to the radar signal in each radar transmission cycle Tr in the phase rotation unit 108 based on the information related to the transmission signal generation timing of each radar transmission cycle Tr input from the transmission signal generation control unit 102. The phase rotation amount setting unit 105 includes, for example, a Doppler shift setting unit 106 and an encoding unit 107.

[0102] The Doppler shift setting unit 106 sets a phase rotation amount corresponding to the Doppler shift amount given to the radar transmission signal (for example, chirp signal) based on information on the transmission signal generation timing of each radar transmission cycle Tr, for example.

[0103] The coding unit 107 sets the phase rotation amount corresponding to the code, for example, based on information related to the transmission signal generation timing of each radar transmission cycle Tr. The coding unit 107 calculates the phase rotation amount for the phase rotation unit 108, for example, based on the phase rotation amount input from the Doppler shift setting unit 106 and the phase rotation amount corresponding to the code, and outputs it to the phase rotation unit 108. In addition, the coding unit 107 outputs information related to the code sequence (for example, each element of the orthogonal code sequence) used in the coding to the radar receiving unit 200 (for example, the output switching unit 209).

[0104] The phase rotation unit 108 gives the chirp signal input from the VCO 104 a phase rotation amount input from the encoding unit 107, and outputs the phase-rotated signal to the transmission antenna unit 109. For example, the phase rotation unit 108 includes a phase shifter and a phase modulator (not shown). The output signal of the phase rotation unit 108 is amplified to a predetermined transmission power and radiated into space from each transmission antenna. For example, a radar transmission signal is given a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and a code sequence, and is multiplexed and transmitted from a plurality of transmission antennas.

[0105] Next, an example of a method of setting the phase rotation amount in the phase rotation amount setting unit 105 will be described.

[0106] The Doppler shift setting unit 106 sets the Doppler shift amount DOP to be given. ndm The phase rotation amount And output to the encoding unit 107. Here, ndm = 1 to N DM . N DM It is the setting number of different Doppler frequency shift amounts, hereinafter referred to as the "Doppler multiplexing number".

[0107] In the radar device 10, since the encoding by the encoding unit 107 is used in combination, the Doppler multiplexing number N may be DM It is set to be smaller than the number of transmission antennas Nt used in multiplex transmission. DM Is 2 or more.

[0108] As DOP1, DOP2, ..., DOP N_DM (“N_DM” can also be expressed as “N DM ”) For example, the Doppler frequency shift amount may be set at equal intervals, or the Doppler frequency shift amount may be set at unequal intervals. In order to use the encoding of the encoding unit 107 described later, for example, each DOP1, DOP2, ..., DOP N_DM Set to satisfy 0≦DOP1, DOP2, ..., DOP N_DM <1 / (TrL oc). Alternatively, you can set DOP1, DOP2, ..., DOP N_DM It is assumed to satisfy equation (1).

[0109] [Formula 1]

[0110]

[0111] In addition, for example, DOP1, DOP2, ..., DOP N_DM The minimum Doppler frequency shift interval Δf MinInterval The following equation (2) is satisfied. In addition, the Doppler shift interval (also recorded as Doppler multiplexing interval, Doppler interval) can be composed of DOP1, DOP2, ..., DOP N_DM Here, Loc represents the number of coding elements. For example, Loc represents the code length of the code used in the coding unit 107.

[0112] [Formula 2]

[0113]

[0114] In addition, it is used to assign each DOP1, DOP2, ..., DOP N_DM The phase rotation amount For example, it can be allocated as shown in the following formula (3).

[0115] [Formula 3]

[0116]

[0117] In addition, the intervals are set to be equal and Δf MinInterval In the case of a Doppler shift amount of equal intervals (hereinafter referred to as "equal interval Doppler shift amount setting"), for example, the values ​​for assigning the DOP are allocated as shown in the following equation (4): ndm The phase rotation amount

[0118] [Formula 4]

[0119]

[0120] In addition, the minimum Doppler frequency shift interval Δf MinInterval The smaller the value, the easier it is for interference between DDM signals to occur, and the higher the possibility of a decrease (e.g., degradation) in target detection accuracy. Therefore, within the range of satisfying the constraints of equation (2), it is preferred to maximize the interval of Doppler frequency shift. For example, when the equal sign in equation (2) holds (e.g., Δf MinInterval =1 / (T r N DM L OC)) can maximize the intervals in the Doppler region between DDM signals (hereinafter referred to as "maximum equal-interval Doppler frequency shift amount setting"). In this case, the phase rotation range greater than 0 and less than 2π is divided into N equal parts. DM DOP1, DOP2, ..., DOP N_DM Different phase rotation amounts are allocated to each. For example, the phase rotation amounts for assigning DOP are allocated as shown in the following equation (5): ndm The phase rotation amount In addition, hereinafter, angles are expressed in radians.

[0121] [Formula 5]

[0122]

[0123] In addition, DOP1, DOP2, ..., DOP N_DM The allocation of the phase rotation amount is not limited to this allocation method. For example, a phase rotation amount allocation table may be used to allocate phase rotation amounts to DOP1, DOP2, ..., DOP N_DM Randomly assign phase rotation (where “N_DM” is equivalent to N DM ).

[0124] Alternatively, in the setting of the Doppler frequency shift amount at equal intervals, by setting Δf in equation (4) MinInterval =1 / (T r (N DM +N int )L OC ), and thus the phase rotation amount is set as shown in the following equation (6). Here, N int Takes an integer value.

[0125] [Formula 6]

[0126]

[0127] The encoding unit 107 assigns N to the Doppler frequency shift setting unit 106. DM The phase rotation amount of the Doppler frequency shift Set based on 1 or N CM In addition, the coding unit 107 sets a phase rotation amount based on both the Doppler frequency shift amount and the code sequence (for example, a "coded Doppler phase rotation amount" (hereinafter referred to as "CDP amount") for generating a coded Doppler multiplexed signal (CDDM signal)), and outputs it to the phase rotation unit 108.

[0128] An example of the operation in the encoding unit 107 is described below.

[0129] For example, preferably, the encoding unit 107 uses the number of codes (for example, the number of code multiplexing) N composed of the code length Loc. CM A plurality of code sequences with low correlation between each other or code sequences that are uncorrelated with each other, for example, an orthogonal code sequence is used. In addition, the code elements constituting the orthogonal code sequence are not limited to real numbers, and may also include complex values.

[0130] Next, N consisting of the code length Loc CM The orthogonal code sequence is expressed as Code ncm ={OC ncm (1), OC ncm (2), ..., OC ncm (Loc)}. OC ncm (noc) represents the ncmth orthogonal code sequence Code ncm Here, noc is the index of the code element, noc = 1 to Loc.

[0131] The orthogonal code sequence used in the encoding unit 107 may be, for example, a Walsh-Hadamard code. The encoding unit 107 uses a Walsh-Hadamard code that can generate N codes. CM The specified code length L of the orthogonal code sequence OC To generate orthogonal code sequences.

[0132] The encoding unit 107 uses the ndm-th Doppler shift amount DOP input from the Doppler shift setting unit 106. ndm The code multiplexing number when encoding the DDM signal (hereinafter referred to as "code Doppler multiplexing number") is expressed as "N CDDM (ndm)". Here, ndm = 1 to N DM .

[0133] The coding unit 107 encodes the DDm signal in such a manner that the coding Doppler multiplexing number N is CDDM (1) N CDDM (2), ..., N CDDM (N DM The coded Doppler multiplexing number N is set so that the sum of the numbers of the transmitting antennas Nt used for multiplexing transmission is equal to CDDM (ndm). Thus, the radar device 10 can perform multiplexing transmission in the Doppler region and the code region (hereinafter referred to as "Coded Doppler Multiplexing Transmission (CDDM Transmission)") using Nt transmission antennas.

[0134] Furthermore, the encoding unit 107 may use, for example, the equally spaced Doppler frequency shift amount setting including the maximum equally spaced Doppler frequency shift amount setting to adjust the coding Doppler multiplexing number N. CDDM(1), N CDDM (2), ..., N CDDM (N DM ), contains more than 1 and N CM For example, the coding unit 107 does not set the code number N for all code Doppler multiplexing numbers. CM Instead, for at least one DOP ndm , the corresponding coded Doppler multiplexing number N CDDM (ndm) is set to be larger than N CM That is, it can be, in DOP ndm Among the multiple combinations with orthogonal code sequences, at least one DOP is as follows ndm , based on the DOP ndm The number of multiplexing of the corresponding orthogonal code sequence (code-Doppler multiplexing number) N CDDM (ndm) is different from the coded Doppler multiplexing number corresponding to other Doppler frequency shift amounts. For example, the coding unit 107 sets the coded Doppler multiplexing number for the DDM signal unevenly. With this setting, the radar device 10 can, for example, demultiplex the signals transmitted by CDDM from multiple transmission antennas into separate signals and receive them over the Doppler range of ±1 / 2Tr through the aliasing determination process in the reception process described in Patent Documents 6 and 7.

[0135] In the m-th transmission cycle Tr, the encoding unit 107 assigns the ndm-th Doppler shift amount DOP ndm The phase rotation amount The CDP amount ψ shown in the following formula (7) is set ndc(ndm)，ndm (m) and output to the phase rotation unit 108.

[0136] [Formula 7]

[0137]

[0138] Here, the subscript "ndc(ndm)" represents the coded Doppler multiplexing number N CDDM The index below (ndm) is the code Doppler multiplexing number for the Doppler frequency shift amount DOP ndm The phase rotation amount The number of coded Doppler multiplexing. For example, ndc(ndm) = 1, ..., N CDDM (ndm) In addition, angle[x] is an operator that outputs the radian phase of the real number x, for example, angle[1]=0, angle[-1]=π, angle[j]=π / 2.

[0139] For example, as shown in formula (7), the CDP amount ψndc(ndm)，ndm (m) is the phase rotation amount that gives the Doppler shift amount DOP during the transmission period of the code length Loc used in the encoding. ndm The phase rotation amount is constant (for example, the first term of equation (7)), and the code Code used in the encoding is given ndc(ndm) Loc of each code element OC ndc(ndm) (1), ..., OC ndc(ndm) (Loc) is the phase rotation amount corresponding to each (the second term of equation (7)).

[0140] In addition, the encoding unit 107 outputs the orthogonal code element index OC_INDEX to the radar receiving unit 200 (output switching unit 209 described later) according to the transmission cycle (Tr). OC_INDEX is an index indicating the orthogonal code sequence Code ndc(ndm) The orthogonal code element index of the element changes cyclically in the range from 1 to Loc according to the transmission period (Tr), as shown in the following equation (8).

[0141] [Formula 8]

[0142] OC_INDEX=mod(m-1,Loc)+1 (8)

[0143] Here, MOD (x, y) is a modulo operator, which is a function that outputs the remainder after dividing x by y. In addition, m = 1 to Nc. Nc is the number of transmission cycles used for radar positioning (hereinafter referred to as "radar transmission signal transmission times"). In addition, the radar transmission signal transmission times Nc is set to an integer multiple of Loc (Ncode times). For example, Nc = Loc × Ncode.

[0144] Next, the coding Doppler multiplexing number N for the DDM signal is set unevenly in the coding unit 107. CDDM An example of the (ndm) method is described below.

[0145] For example, the coding unit 107 sets the number of orthogonal code sequences (for example, the number of code multiplexing or the number of codes) N that satisfies the following conditions: CM For example, the number of orthogonal code sequences Nt is proportional to the number of transmitting antennas used in multiplexing transmission. CM and Doppler multiplexing number N DM The following relationship is satisfied.

[0146] (Number of orthogonal code sequences CM )×(Doppler multiplexing number N DM )>Number of transmit antennas used in multiplexing transmission Nt

[0147] Next, the CDP amount ψ is explained ndc(ndm)，ndm (m) setting example.

[0148] For example, in the encoding unit 107, the number of transmission antennas used for multiplexing transmission is Nt=3, and the Doppler multiplexing number N DM =2, code multiplexing number N CM = 2, using the orthogonal code sequence Code1 = {1, 1}, Code2 = {1, -1} with a code length of Loc = 2. In this case, for example, Figure 6 As shown, when the coded Doppler multiplexing number N is set CDDM (1) = 1, N CDDM When (2)=2, the encoding unit 107 sets the CDP amount ψ 1，1 (m), ψ 1，2 (m), ψ 2，2 (m), and outputs it to the phase rotation unit 108. For example, when the CDP amount ψ is set 1，1 (m), the encoding unit 107 performs the following setting as in equation (9). Figure 6 In FIG. 1 , “○” indicates the Doppler frequency shift amount and orthogonal code being used, and “×” indicates the allocation of the Doppler frequency shift amount and orthogonal code not being used.

[0149] [Formula 9]

[0150]

[0151] The method of setting the phase rotation amount in the phase rotation amount setting unit 105 has been described above.

[0152] exist Figure 4 In the embodiment, the phase rotation unit 108 performs the phase rotation according to the CDP amount ψ set in the phase rotation amount setting unit 105. ndc(ndm)，ndm (m) A phase rotation amount is given to the chirp signal input from the radar transmission signal generation unit 101 at the transmission period Tr. Here, ndm = 1 to N DM , ndc(ndm)=1~N CDDM (ndm).

[0153] The outputs from the Nt phase rotation units 108 (for example, referred to as CDDM signals) are amplified to predetermined transmission power and then radiated into space from the Nt transmission antennas of the transmission antenna unit 109 .

[0154] In addition, the CDP amount ψ is given below ndc(ndm)，ndm The phase rotation unit 108 of (m) is expressed as "phase rotation unit PROT#[ndc(ndm), ndm]". Similarly, the transmitting antenna that radiates the output of the phase rotation unit PROT#[ndc(ndm), ndm] into space is also expressed as "transmitting antenna Tx#[ndc(ndm), ndm]". Here, ndm=1 to N DM, ndc(ndm)=1~N CDDM (ndm). Alternatively, the Nt transmitting antennas are also expressed as Tx#1, Tx#2, ..., Tx#Nt. A known table or the like may be used in advance to establish a relationship with the CDP amount assigned to the radar transmission signal transmitted from Tx#1, Tx#2, ..., Tx#Nt. Thus, for example, it is possible to determine (or detect) the CDP amount ψ ndc(ndm)，ndm (m) to determine (or detect) the transmitting antenna.

[0155] For example, in Figure 6 In the example shown, the CDP amount ψ is input from the encoding unit 107 to the phase rotation unit 108 at each transmission cycle. 1，1 (m), ψ 1，2 (m), ψ 2，2 (m).

[0156] For example, the phase rotation unit PROT#[1,1] outputs the chirp signal cp(t) generated in the radar transmission signal generation unit 101 according to the transmission cycle, and the phase rotation amount ψ is given in the mth transmission cycle. 1，1 (m) signal exp[jψ 1，1 (m)]cp(t). In addition, the output of the phase rotation unit PROT#[1,1] is output from the transmitting antenna Tx#[1,1]. Here, cp(t) represents a chirp signal according to the transmission period. Similarly, the output of the phase rotation unit PROT#[1,2] is output from Tx#[1,2], and the output of the phase rotation unit PROT#[2,2] is output from Tx#[2,2].

[0157] The above shows that the CDP quantity ψ ndc(ndm),ndm (m) setting example.

[0158] In addition, in this embodiment, the coded Doppler multiplexing number N for the DDM signal is set unevenly. CDDM In the case of (ndm), it can be that the Doppler frequency shift amount DOP ndm Orthogonal code sequence Code ncm In the combination of ndm The corresponding orthogonal code sequence Code ncm The multiplexing number (for example, the coded Doppler multiplexing number N CDDM (ndm)) is different.

[0159] In addition, in this embodiment, the coded Doppler multiplexing number N for the DDM signal is uniformly set. CDDM (ndm) case, it can be, in DOP ndm Orthogonal code sequence Code ncmIn the combination of ndm The corresponding orthogonal code sequence Code ncm The multiplexing number (for example, the coded Doppler multiplexing number N CDDM (ndm)) are the same. In this case, DOP ndm The number of combinations of orthogonal code sequences and the number of transmitting antennas Nt may be the same number (for example, Nt may be set to DM ×N CM =Nt).

[0160] In addition, in this embodiment, the transmitting antenna unit 109 Tx#1 to Tx#Nt may include at least two transmitting antennas of different polarizations to form a polarization radar. For example, as different polarizations, Tx#1 to Tx#Nt may include transmitting antennas in a mutually orthogonal polarization relationship. In addition, there may be multiple transmitting antennas for at least one of the multiple polarizations, and there may be at least one transmitting antenna for the other polarizations.

[0161] The radar device 10 (for example, the phase rotation amount setting unit 105) sets different CDP amounts ψ for each transmitting antenna, for example, taking into account transmitting antennas with different polarizations. ndc(ndm),ndm (m) The radar device 10 (for example, the phase rotation unit 108) gives the chirp signal the CDP amount ψ set in this way. ndc(ndm),ndm (m) and output to the transmitting antenna unit 109.

[0162] Therefore, even when the reception levels between the reception signals corresponding to the transmitting antennas with different polarizations are greatly different (for example, the reception level difference or the reception level ratio is above a threshold), the radar device 10 can demultiplex the CDDM signal, thereby suppressing the degradation of the positioning performance and the radar detection performance (an action example will be described later).

[0163] Hereinafter, an operation example of the phase rotation amount setting unit 105 in the radar transmitting unit 100 will be described when a polarization MIMO radar including at least two transmission antennas of different polarizations is configured.

[0164] In addition, for example, it is assumed that the number of transmission antennas Nt≧3 and the number of Doppler multiplexing N DM ≧2, code multiplexing number N CM ≧2, where Nt <N DM ×N CM As described above, the number of transmitting antennas Nt may be greater than the total number of combinations of Doppler frequency shift amounts and code sequences (N DM ×N CM ) is small. In addition, without limitation to this, the total number of combinations of Doppler frequency shift and code sequence (N DM ×N CM) can also be the same number as Nt.

[0165] In addition, the number of different polarizations included in the transmission antenna (hereinafter referred to as "transmission polarization number") is expressed as "NPL". In addition, the qth polarization is expressed as "PLq". q is an integer value within the transmission polarization number (for example, q = one of 1 to NPL).

[0166] In addition, the number of transmitting antennas for PLq polarization is expressed as “N PLq "N PLq ≧1, the total number of transmitting antennas for each PLq polarization is Nt. For example, when NPL=2, the number of transmitting antennas for PL1 polarization is N PL1 ≧1, the number of transmitting antennas for PL2 polarization is N PL2 ≧1, N PL1 +N PL2 =N t .

[0167] In addition, the Doppler multiplexing number assigned to the transmission antenna of PLq polarization is expressed as “N DM_PLq Here, N DM_PLq ≦N DM For example, when NPL = 2, N DM_PL1 、N DM_PL2 ≦N DM .

[0168] The radar device 10 uses at least two polarizations, and includes N transmitting antennas for PL1 polarization and PL2 polarization, which are different therefrom. PL1 、N PL2 The phase rotation amount setting unit 105 in the radar transmitter 100 of the radar device 10 (for example, a polarization MIMO radar) sets the code Doppler multiplexing number N for the DDM signal unevenly, for example. CDDM (ndm), and the CDP amount ψ is set so as to satisfy the following condition 1 ndc(ndm)，ndm (m). Here, ndm = 1 to N DM , ndc(ndm)=1~N CDDM (ndm).

[0169] <Condition 1>

[0170] For example, the pattern of the Doppler frequency shift amount and the code sequence allocated to the transmitting antenna of PL1 polarization (e.g., coded Doppler multiplexing (CDDM) mode) is made different from the CDDM mode allocated to the transmitting antenna of PL2 polarization. For example, the phase rotation amount setting unit 105 sets the CDP amount ψ that satisfies different Doppler frequency shift amount allocation patterns, different code multiplexing (CDM) mode conditions (e.g., different code multiplexing numbers between DDM signals), or different DDM and CDM mode conditions for the transmitting antenna of PL1 polarization and the transmitting antenna of PL2 polarization. ndc(ndm)，ndm (m).

[0171] For example, the different DDM mode condition may be one of the following conditions (eg, also referred to as "condition 1A" or "condition 1 of 1A").

[0172] 1A) Different DDM signal mode conditions:

[0173] (A-1) is the same as the Doppler multiplexing number corresponding to each polarization (for example, the Doppler multiplexing number of the transmission signal transmitted from the transmission antenna of each polarization) (for example, N DM_PL1 =N DM_PL2 , but only for N DM_PL1 =N DM_PL2 ≧2), and each polarization includes a different Doppler shift interval (for example, the interval of the Doppler shift amount corresponding to the transmitting antenna of each polarization).

[0174] (A-2) The Doppler multiplexing number for each polarization (for example, the Doppler multiplexing number of the transmission signal transmitted from the transmission antenna of each polarization) is different (N DM_PL1 ≠N DM_PL2 ).

[0175] (A-3) in N DM_PL1 ≧3, N DM_PL2 When ≧3, when the same Doppler shift interval is included in the Doppler shift intervals of each polarization, the order of the Doppler shift intervals is different (the cycle is inconsistent).

[0176] In addition, for example, the different CDM mode condition may be one of the following conditions (eg, also referred to as "condition 1B").

[0177] (B-1) The code intervals (for example, code index intervals) allocated to the respective DDM signals are different (cyclic inconsistency).

[0178] (B-2) The code multiplexing numbers assigned to the respective DDM signals are different (circular inconsistency).

[0179] In addition, the phase rotation amount setting unit 105 may set the CDP amount ψ that further satisfies the following condition 2, for example: ndc(ndm),ndm (m).

[0180] <Condition 2>

[0181] The signals transmitted from the transmitting antennas of the same polarization are multiplexed and transmitted with a code multiplexing number that is not uniform between the DDM signals, wherein the code multiplexing number may be greater than 1 and N CM A code multiplexing number within the range below -1 (in N CM =2, the code multiplexing number may be 1). For example, with respect to a transmitting antenna of at least one of PL1 polarization and PL2 polarization, among a plurality of combinations of Doppler frequency shift amounts and code sequences, at least one Doppler frequency shift amount is such a Doppler frequency shift amount that the code multiplexing number based on the code sequence corresponding to the Doppler frequency shift amount is different from the code multiplexing number based on the code sequence corresponding to the other Doppler frequency shift amounts.

[0182] For example, according to A-3 of condition 1, when the values ​​of the multiple intervals of Doppler frequency shift amounts allocated between the transmitting antenna of PL1 polarization and the transmitting antenna of PL2 polarization (for example, the combination of Doppler frequency shift intervals) are the same, the order of the multiple Doppler frequency shift intervals corresponding to the transmitting antenna of PL1 polarization on the Doppler frequency axis and the order of the multiple Doppler frequency shift intervals corresponding to the transmitting antenna of PL2 polarization on the Doppler frequency axis may be different. For example, the combination of the intervals included in the sequence in which the intervals of the Doppler frequency shift amounts allocated to the transmitting antenna of PL1 polarization are arranged in order from the smaller side on the Doppler frequency axis is the same as the combination of the intervals included in the sequence in which the intervals of the Doppler frequency shift amounts allocated to the transmitting antenna of PL2 polarization are arranged in order from the smaller side on the Doppler frequency axis, and the first sequence and the second sequence are different sequences when arranged in a circle. When A-3 of condition 1 is satisfied, even if one of the Doppler shift intervals of the transmitting antennas with PL1 polarization and the Doppler shift intervals of the transmitting antennas with PL2 polarization is cyclically shifted in the Doppler frequency domain, the two will not match (circular mismatch).

[0183] In addition, for example, according to B-1 of condition 1, the order of the code sequences corresponding to the transmitting antennas of PL1 polarization on the Doppler frequency axis may be different from the order of the code sequences corresponding to the transmitting antennas of PL2 polarization on the Doppler frequency axis. For example, a sequence in which the indices of the code sequences corresponding to the Doppler frequency shift amounts assigned to the transmitting antennas of PL1 polarization are arranged in order from the smaller side on the Doppler frequency axis and a sequence in which the indices of the code sequences corresponding to the Doppler frequency shift amounts assigned to the transmitting antennas of PL2 polarization are arranged in order from the smaller side on the Doppler frequency axis are different sequences when arranged in a circle. In the case of satisfying B-1 of condition 1, even if one of the indices of the code sequences corresponding to the Doppler frequency shift amounts of the transmitting antennas of PL1 polarization and the indices of the code sequences corresponding to the Doppler frequency shift amounts of the transmitting antennas of PL2 polarization is cyclically shifted in the Doppler frequency domain, the two will not be consistent (cyclic inconsistency).

[0184] In addition, for example, according to B-2 of condition 1, the order of the code multiplexing numbers based on the code sequence corresponding to the transmitting antenna of PL1 polarization and the order of the code multiplexing numbers based on the code sequence corresponding to the transmitting antenna of PL2 polarization on the Doppler frequency axis may be different. For example, a sequence in which the code multiplexing numbers corresponding to the Doppler frequency shift amounts assigned to the transmitting antenna of PL1 polarization are arranged in order from the smaller side on the Doppler frequency axis and a sequence in which the code multiplexing numbers corresponding to the Doppler frequency shift amounts assigned to the transmitting antenna of PL2 polarization are arranged in order from the smaller side on the Doppler frequency axis are different sequences when arranged in a circle. In the case of satisfying B-2 of condition 1, even if one of the code multiplexing numbers corresponding to the Doppler frequency shift amounts of the transmitting antenna of PL1 polarization and the code multiplexing numbers corresponding to the Doppler frequency shift amounts of the transmitting antenna of PL2 polarization is cyclically shifted in the Doppler frequency domain, the two will not be consistent (cyclic inconsistency).

[0185] The radar device 10 provides the CDP amount to the transmission antenna so as to satisfy the above-mentioned condition 1, thereby being able to obtain the following effects.

[0186] For example, in addition to the Doppler phase rotation of the coding during transmission as described above, the Doppler frequency of the unknown target is added to the Doppler frequency of the received signal. Therefore, while the intervals between the DDM signals are maintained, their Doppler frequencies may change in the positive or negative direction. For example, by satisfying 1A of condition 1, when a CDDM signal assigned to a transmitting antenna with PL1 polarization is received but a CDDM signal assigned to a transmitting antenna with PL2 polarization is not received, and when a CDDM signal assigned to a transmitting antenna with PL2 polarization is received but a CDDM signal assigned to a transmitting antenna with PL1 polarization is not received, the interval or Doppler multiplexing number (for example, DDM mode) of the DDM signal is different, and the radar device 10 can distinguish these.

[0187] In addition, for example, by satisfying 1B of condition 1, when a CDDM signal assigned to a transmitting antenna with PL1 polarization is received but a CDDM signal assigned to a transmitting antenna with PL2 polarization is not received, and when a CDDM signal assigned to a transmitting antenna with PL2 polarization is received but a CDDM signal assigned to a transmitting antenna with PL1 polarization is not received, after decode multiplexing each DDM signal, the code interval or code multiplexing number (for example, CDM mode) with a high reception level is different, and the radar device 10 is able to distinguish these.

[0188] Therefore, by making the setting of the CDP amount performed by the phase rotation amount setting unit 105 satisfy condition 1, even if the reception levels between the reception signals corresponding to the transmitting antennas with different polarizations are greatly different, the radar device 10 can demultiplex the CDDM signals in this case, thereby suppressing the degradation of the positioning performance and the radar detection performance.

[0189] In addition, by making the setting of the CDP amount performed by the phase rotation amount setting unit 105 satisfy condition 2 in addition to condition 1, the Doppler frequency range detectable by the radar device 10 reaches the range of -1 / (2Tr)≦fd<1 / (2Tr), which can be expanded to a range equivalent to the Doppler detection range when a single transmitting antenna is used (an example will be described later).

[0190] For example, in CDDM transmission performed by the radar device 10, both condition 1 and condition 2 may be satisfied, or condition 1 may be satisfied but condition 2 may not be satisfied. For example, as a case where condition 1 is satisfied but condition 2 is not satisfied, the following three cases are mentioned.

[0191] Case 1 is the case where both PL1 polarization and PL2 polarization do not meet condition 2. In this case, the detectable Doppler frequency range fd is -1 / (2Tr)≦fd<1 / (2Tr), -1 / (2Loc N DM_PL1 Tr)≦fd<1 / (2Loc NDM_PL1 Tr) or -1 / (2Loc N DM_PL2 Tr)≦fd<1 / (2Loc N DM_PL2 Case 2 is when PL2 polarization does not satisfy condition 2. In this case, the detectable Doppler frequency range fd is -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2Loc N DM_PL2 Tr)≦fd<1 / (2Loc N DM_PL2 Case 3 is the case where PL1 polarization does not satisfy condition 2. In this case, the detectable Doppler frequency range fd is -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2Loc N DM_ PL1 Tr)≦fd<1 / (2Loc N DM_PL1 Tr) this range.

[0192] Regardless of which of the cases 1 to 3, by Nt>Loc N DM_PL1 Satisfy or Nt>Loc N DM_PL2 , the detectable Doppler frequency range can be expanded to a larger range than the Doppler detection range of -1 / (2Nt Tr)≦fd<1 / (2Nt Tr) when the Doppler multiplexing is performed at equal intervals.

[0193] Next, an example of setting the CDP amount in the phase rotation amount setting unit 105 will be described.

[0194] In the following, the interval between the Doppler frequency shift amounts given to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval “Δfd (n1，n2) ”. Here, Δfd (n1，n2) Indicates the Doppler frequency shift DOP given to Tx#n1 n1 The Doppler frequency shift DOP given to Tx#n2 based on the reference n2 The interval (DOP n2 -DOP n1 ). In addition, in the Doppler frequency shift interval Δfd (n1，n2) In the case of negative values ​​(for example, in (DOP n2 -DOP n1 )<0), taking into account the aliasing in the observation range of the Doppler analysis unit 210 described later, that is, the range greater than -1 / (2Loc Tr) and less than 1 / (2Loc Tr), Δfd is used. (n1，n2) =1 / (Loc Tr)-Δfd (n1，n2) To calculate the Doppler frequency shift interval Δfd (n1，n2) , and is expressed as a positive value. In the following description, regarding the Doppler frequency shift interval Δfd(n1，n2) The same expression is also used in the records.

[0195] <Setting Example 1>

[0196] Setting example 1 is a setting example of the CDP amount in the case where condition 1 (satisfying the different CDM mode condition) and condition 2 are satisfied.

[0197] 7 indicates the number of transmitting antennas Nt = 4, N PL1 =2, N PL2 Example of setting the CDP amount in the phase rotation amount setting unit 105 when φ = 2. Figure 7 In the figure, the black circles (●) represent the distribution of CDDM signals of the transmitting antennas (Tx#1 and Tx#2) with PL1 polarization, and the white circles (○) represent the distribution of CDDM signals of the transmitting antennas (Tx#3 and Tx#4) with PL2 polarization.

[0198] In addition, Figure 7 In the Doppler multiplexing number N DM =3, the Doppler shift setting unit 106 can set the three values ​​DOP1 to DOP3 using the maximum equally spaced Doppler shift amount setting shown in, for example, equation (5). Figure 7 The phase rotation amount given to DOP1 = 0 is The phase rotation amount given DOP2 = Δfd The phase rotation amount given DOP3 = -Δfd (You can also set ).like Figure 7 As shown, the interval between DDm signals (also called "Doppler multiplexing interval", "Doppler frequency shift interval", "Doppler interval") Δfd is an equal interval, Δfd = 1 / (6Tr).

[0199] In addition, Figure 7 In the code multiplexing number N CM =2, the encoding unit 107 uses, for example, an orthogonal code sequence Code1={1,1}, Code2={1,-1} with a code length Loc=2. In the following setting examples 2 and 3, the code multiplexing number N is also CM =2, the same code is also used.

[0200] exist Figure 7 In the example, the number of transmitting antennas Nt = 4, the number of Doppler multiplexing N DM =3, code multiplexing number N CM =2, Nt <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the DDM signal unevenly. CDDM (ndm) (here, ndm = 1 to NDM ).

[0201] like Figure 7 As shown, in the coding unit 107, the coding Doppler multiplexing numbers for the DDM signals using the three DOP1 to DOP3 input from the Doppler shift setting unit 106 are N and N, respectively. CDDM (1) = 1, N CDDM (2) = 1, N CDDM (3)=2. In this way, the phase rotation amount setting unit 105 sets the code-Doppler multiplexing number for the DDM signal unevenly.

[0202] In addition, Figure 7 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmitting antennas Tx#1 and Tx#2 of PL1 polarization. DM =3 DDM signal using Doppler shift amounts DOP1 and DOP3 (N DM_PL1 =2). In addition, the coding unit 107 allocates Code 2 and Code 1 to DOP1 and DOP3 using Tx#1 and Tx#2 allocated to PL1 polarization, respectively. Hereinafter, such allocation is expressed as the phase rotation amount setting unit 105 setting the CDP amount ψ to Tx#1 and Tx#2 allocated to PL1 polarization, respectively. 2，1 (m), ψ 1，3 (m). In addition, Figure 7 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmitting antennas Tx#3 and Tx#4 of PL2 polarization. DM =3, for example, a DDM signal using Doppler shift amounts DOP2 and DOP3 (N DM_PL2 =2).

[0203] For example, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#3 and Tx#4 of PL2 polarization. 2，2 (m), ψ 2，3 (m).

[0204] exist Figure 7 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the PL1 polarized transmission antenna and the PL2 polarized transmission antenna is N. DM_PL1 =N DM_PL2 =2, which is the same. In addition, the Doppler frequency shift intervals of the DDM signals assigned to Tx#1~#2 of PL1 polarization are Δfd(1,2)=2Δfd, Δfd(2,1)=Δfd, and the Doppler frequency shift intervals of the DDM signals assigned to Tx#3~#4 of PL2 polarization are Δfd(3,4)=Δfd, Δfd(4,3)=2Δfd, which are the same (cyclically consistent).

[0205] therefore, Figure 7 The setting of the CDP amount shown does not meet any of the DDM mode conditions of condition 1A.

[0206] In addition, Figure 7 In FIG. 1 , for each DDM signal using DOP1 to DOP3, the code allocated to the transmitting antenna of PL1 polarization is [Code2, no allocation, Code1], and the code multiplexing number allocated to each DDM signal is 0 or 1.

[0207] In addition, hereinafter, the code index assigned to the transmitting antenna of PL1 polarization for each DDM signal using Doppler frequency shift amounts DOP1 to DOP3 is recorded as "CiPL1 = (2, *, 1)". In CiPL1, "*" indicates the case where no code is assigned. In addition, when multiple codes are assigned to a DDM signal, "&" is used to express it. For example, when Code1 and Code2 are assigned to a DDM signal, it is expressed as "1&2". The code index is also called the "code interval".

[0208] In addition, the code multiplexing number assigned to the transmission antenna of PL1 polarization for each DDM signal using the Doppler shift amounts DOP1 to DOP3 is described as "NcPL1 = (1, 0, 1)" ( Figure 7 situation).

[0209] exist Figure 7 , the code assigned to each DDM signal using DOP1 to DOP3 and the transmitting antenna with PL2 polarization is [no assignment, Code2, Code2], and the code multiplexing number assigned to each DDM signal is 0 or 1. In addition, similarly to the case of PL1 polarization, the code index assigned to each DDM signal using DOP1 to DOP3 and the transmitting antenna with PL2 polarization is recorded as "CiPL2=(*, 2, 2)". In addition, the code multiplexing number assigned to each DDM signal using DOP1 to DOP3 and the transmitting antenna with PL2 polarization is recorded as "NcPL2=(0, 1, 1)".

[0210] In this way, for the PL1 polarized transmitting antenna and the PL2 polarized transmitting antenna, the code multiplexing numbers allocated to each DDM signal are NcPL1 = (1, 0, 1) and NcPL2 = (0, 1, 1), which are cyclically consistent and therefore do not satisfy B-2 of condition 1.

[0211] On the other hand, for the PL1 polarized transmitting antenna and the PL2 polarized transmitting antenna, the code indexes assigned to each DDM signal are CiPL1 = (2, *, 1) and CiPL2 = (*, 2, 2), which are different (or can be expressed as "cyclically inconsistent". Hereinafter, it is also expressed as "different code index intervals").

[0212] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. The code index at this time is CiPL1 alias =(1, *, 2) and CiPL2 alias =(*, 1, 1), the two are different (circular inconsistency). Therefore, in Figure 7 In the example, when the Doppler frequency of the target is -1 / (2Tr) ≤ f dtg In the range of <-1 / (2Tr), the code index is cyclically inconsistent and the code intervals are different.

[0213] Therefore, the code interval allocated to each DDM signal is different between each polarization, so B-1 of condition 1 is satisfied, which meets the conditions of different CDM modes.

[0214] As mentioned above, Figure 7 The setting of the CDP amount shown is an example of a setting that satisfies condition 1.

[0215] In addition, Figure 7 In the PL1 polarized transmission antenna, the code multiplexing number assigned to each DDM signal is NcPL1 = (1, 0, 1), and in the PL2 polarized transmission antenna, the code multiplexing number assigned to each DDM signal is NcPL2 = (0, 1, 1). Both are multiplexed and transmitted with uneven code multiplexing numbers between DDM signals, and the code multiplexing number is included in 1 or more and N CM In the range below -1.

[0216] Therefore, in Figure 7 In the example, signals transmitted from transmitting antennas of the same polarization (for example, PL1 polarization and PL2 polarization, respectively) are multiplexed and transmitted with a code multiplexing number that is not uniform between DDM signals, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Figure 7 The setting of the CDP amount shown is a setting example that satisfies Condition 2 in both PL1 polarization and PL2 polarization.

[0217] The following is based on Figure 7The setting of the CDP amount in the phase rotation amount setting unit 105 shown is described as an example of a received signal in the output of the Doppler analysis unit 210 in which the transmitting antenna unit 109 is used with the PL1 polarization being left-hand circular polarization (LC) and the PL2 polarization being right-hand circular polarization (RC), and the receiving antenna unit 202 is used with an LC polarization (PL1 polarization) antenna.

[0218] Figure 8 The output of the Doppler analysis unit 210 for the target object reflected wave of a certain distance index is shown. For example, the target object reflected wave includes the Doppler frequency f of the target object. dtg Therefore, the radar device 10 receives the Doppler frequency shift amount set in the radar transmitter 100. dtg The amount of Doppler shift in the signal. Figure 8 As an example, the Doppler frequency f of the reflected wave of the target object is shown. dtg = 0 and f dtg =-1 / (2Tr).

[0219] In addition, Figure 8 In the figure, the size of the black circle (●) and the white circle (○) indicates the received power. If the size of the black circle (●) and the white circle (○) is smaller, it means that the received power is smaller (for example, the received power is as small as the noise level) (the same mark is also used in the following setting examples).

[0220] Here, when the reflected wave of the radar transmission wave after being reflected by the target object is a reflected wave having multiple reflection times or includes multiple scattered waves, the reflected wave may include multiple polarizations. Therefore, the difference in the reception level of the received signal in the radar device 10 is not easy to become large between the received signals corresponding to the different polarization transmission antennas (for example, the transmission antenna of PL1 polarization and the transmission antenna of PL2 polarization). Therefore, the radar device 10 receives the received signal corresponding to the transmission antenna of RC polarization (PL2 polarization) and the received signal corresponding to the transmission antenna of LC polarization (PL1 polarization) at substantially the same reception level.

[0221] For example, in Figure 7 When the CDP amount is set as shown, when the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)) is not included, the following is obtained: Figure 8 The received signal is as shown in (a). Figure 8 As shown in (a), the reception levels of the reception signals corresponding to Tx#1 and Tx#2 (PL1 polarization) and Tx#3 and Tx#4 (PL2 polarization) are substantially the same level.

[0222] In addition, for example, when the radar device 10 receives a reflected wave (for example, a first regular reflection) of a radar transmission wave reflected normally at a target object (for example, a mirror reflection on a surface with few bumps and depressions), the reception level may be different between polarized transmission antennas. For example, the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna becomes a signal of the same polarization as the LC polarization (PL1 polarization) reception antenna. On the other hand, for example, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna becomes a signal of cross-polarization with the LC polarization (PL1 polarization) reception antenna. Therefore, compared with the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna, the reception level of the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna may be smaller (depending on the cross-polarization discrimination of the antenna and, for example, a reception level that is 10 dB or more smaller). For example, depending on the reception SNR, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna may be below the noise level, so that the peak detection of the Doppler frequency becomes difficult in the radar device 10.

[0223] For example, in Figure 7 In the case of the CDP amount setting shown, in the case of a target reflected wave including RC polarization (PL2 polarization) cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)), it is obtained Figure 8 The received signal is as shown in (b). Figure 8 As shown in (b), the reception level of the reception signal corresponding to Tx#3 and Tx#4 (PL2 polarization) is smaller than the reception level of the reception signal corresponding to Tx#1 and Tx#2 (PL1 polarization).

[0224] In addition, for example, when the radar device 10 receives a reflected wave of the radar transmission wave reflected normally at the target object and further reflected normally on the road surface or the like (for example, a second regular reflection), the reception level may be different between polarized transmission antennas. For example, the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna becomes a signal of the same polarization as the LC polarization (PL1 polarization) reception antenna. On the other hand, for example, the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna becomes a signal of cross-polarization with the LC polarization (PL1 polarization) reception antenna. Therefore, compared with the reception signal corresponding to the RC polarization (PL2 polarization) transmission antenna, the reception level of the reception signal corresponding to the LC polarization (PL1 polarization) transmission antenna may be smaller (depending on the cross-polarization discrimination of the antenna and, for example, a reception level that is 10 dB or more smaller). For example, depending on the reception SNR, the reception signal from the LC polarization (PL1 polarization) transmission antenna may be below the noise level, so that in the radar device 10, the peak detection of the Doppler frequency becomes difficult.

[0225] For example, in Figure 7 In the case of the CDP amount setting shown in FIG. 1 , in the case of a target reflected wave including LC polarization (PL1 polarization) cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)), the following is obtained: Figure 8 The received signal is as shown in (c). Figure 8 As shown in (c), the reception level of the reception signal corresponding to Tx#1 and Tx#2 (PL1 polarization) is smaller than the reception level of the reception signal corresponding to Tx#3 and Tx#4 (PL2 polarization).

[0226] For example, Figure 8 As shown in (a), when the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the received signals of the transmitting antennas (Tx#3 and Tx#4) corresponding to the RC polarization (PL2 polarization) and the transmitting antennas (Tx#1 and Tx#2) corresponding to the LC polarization (PL1 polarization) at approximately the same level or in the range of several dB to 6 dB. Figure 8 In (a), for the signals transmitted from Nt Tx#1 to Tx#4 consisting of RC polarized (PL2 polarized) transmitting antennas and LC polarized (PL1 polarized) transmitting antennas, the coded Doppler multiplexing number N for each DDM signal is used. CDDM Therefore, the radar device 10 can demultiplex the CDDM signal based on the existing demultiplexing operation of the CDDM signal (for example, refer to Patent Document 7).

[0227] In addition, if Figure 8 (b) and Figure 8 As shown in (c), when the reflected wave of the target object with cross polarization relative to the receiving antenna is included, when the reflected wave of the target object with cross polarization PL2 is included ( Figure 8 (b)) and when the reflected wave of the target containing PL1 polarization is cross-polarized ( Figure 8 In (c)), the radar device 10 receives CDDM signals that are different from each other (for example, the CDDM signal of B-1 that satisfies condition 1).

[0228] For example, Figure 8 (b) i) indicates that the Doppler frequency of the reflected wave of the target object with PL2 polarization as cross polarization is f dtg = 0. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, the Doppler frequency of the target object is -1 / (4Tr)≦f dtg<-1 / (4Tr), CiPL1=(2,*,1).

[0229] For example, Figure 8 (b) ii) indicates that the Doppler frequency of the reflected wave of the target object with PL2 polarization as cross polarization is f dtg =-1 / (2Tr) received signal. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, the Doppler frequency of the target object is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), CiPL1 alias =(1, *, 2).

[0230] In addition, for example, Figure 8 (c) i) indicates that the Doppler frequency of the reflected wave of the target object with PL1 polarization as cross polarization is f dtg = 0. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, the Doppler frequency of the target object is -1 / (4Tr)≦f dtg <-1 / (4Tr), CiPL2=(*, 2, 2).

[0231] For example, Figure 8 (c) ii) indicates that the Doppler frequency of the reflected wave of the target object with PL1 polarization as cross polarization is f dtg =-1 / (2Tr) received signal. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, the Doppler frequency of the target object is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), CiPL2 alias =(*, 1, 1).

[0232] As described above, in the case of a reflected wave from a target object having a cross-polarization relative to the polarization of the receiving antenna, when the reception level of the received signal of the transmitting antenna corresponding to the PL1 polarization decreases and when the reception level of the received signal of the transmitting antenna corresponding to the PL2 polarization decreases, the reflected wave signal received by the radar device 10 is a CDDM signal of a pattern different from each other (for example, a pattern of code index or code interval) even if each DDM signal is received while being cyclically shifted on the Doppler frequency axis due to the Doppler frequency of the target object.

[0233] Therefore, the radar device 10 can, for example, determine in the coded Doppler multiplexing and demultiplexing unit 212 described later whether a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the PL1 polarization (for example, LC polarization) has occurred, or a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the PL2 polarization (RC polarization) has occurred, based on the peak value of the Doppler frequency detected after code demultiplexing.

[0234] In addition, for example, the DDM signal of PL1 polarization is multiplexed and transmitted with the code multiplexing number NcPL1=(1, 0, 1) which is uneven among the DDM signals (for example, for the three DDM signals, the code multiplexing number is 0 or 1 respectively, so it can be regarded as uneven CDDM transmission). Therefore, for example, when the result of the determination by the coded Doppler multiplexing demultiplexing unit 212 is that the received signal is a received signal corresponding to the transmission antenna of LC polarization (PL1 polarization), the radar device 10 can use the existing demultiplexing operation of the CDDM signal to demultiplex the CDDM signal.

[0235] Similarly, for example, a PL2 polarized DDM signal is multiplexed and transmitted with a code multiplexing number NcPL2=(0, 1, 1) that is not uniform among the DDM signals (for example, the code multiplexing number is 0 or 1 for each of the three DDM signals, and therefore it can be considered as non-uniform CDDM transmission). Therefore, for example, when the coded Doppler multiplexing demultiplexing unit 212 determines that the received signal is a received signal corresponding to a transmitting antenna of PL2 polarization, the radar device 10 can demultiplex the CDDM signal using the existing demultiplexing operation of the CDDM signal.

[0236] By operating the code Doppler multiplexing and demultiplexing unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output corresponding to the transmission antenna for each CDDM signal.

[0237] <Setting Example 2>

[0238] Setting example 2 is a setting example of the CDP amount in a case where condition 1 (a case where different CDM mode conditions (B-1 and B-2) are satisfied) and condition 2 are satisfied. Fig. 9 Indicates the number of transmitting antennas Nt = 6, N PL1 =3,N PL2 Example of setting the CDP amount in the phase rotation amount setting unit 105 when φ = 3. Fig. 9 In the figure, the black circles (●) represent the distribution of CDDM signals of the transmission antennas (Tx#1 to #3) of PL1 polarization, and the white circles (○) represent the distribution of CDDM signals of the transmission antennas (Tx#4 to #6) of PL2 polarization.

[0239] In addition, Fig. 9 In the Doppler multiplexing number N DM =4, the Doppler shift setting unit 106 can set the four values ​​DOP1 to DOP4 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig. 9 In the example, the phase rotation amounts given to DOP1 = 0, DOP2 = Δfd, DOP3 = -2Δfd, and DOP4 = -Δfd are respectively ( Also available). Fig. 9 As shown, the Doppler multiplexing interval Δfd is an equal interval, Δfd=1 / (8Tr).

[0240] exist Fig. 9 In the example, the number of transmitting antennas Nt = 6, the number of Doppler multiplexing N DM =4, code multiplexing number N CM =2, N t <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the DDM signal unevenly. CDDM (ndm) (here, ndm = 1 to N DM ).

[0241] like Fig. 9 As shown, in the coding unit 107, the coding Doppler multiplexing numbers for the DDM signals using the four signals DOP1 to DOP4 input from the Doppler shift setting unit 106 are set to N and N respectively. CDDM (1) = 1, N CDDM (2) = 2, N CDDM (3) = 2, N CDDM (4)=1. In this way, the phase rotation amount setting unit 105 sets the code-Doppler multiplexing number for the DDM signal unevenly.

[0242] In addition, Fig. 9 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1 to Tx#3 of PL1 polarization. DM =4 DDM signal using Doppler shift amounts DOP1 and DOP2 (N DM_PL1 =2) For example, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#1 to Tx#3 of PL1 polarization. 1，1 (m), ψ 1，2 (m), ψ 2，2 (m).

[0243] In addition, Fig. 9 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#4 to Tx#6 of PL2 polarization.DM =4 DDM signal using Doppler shift amounts DOP3 and DOP4 (N DM_PL2 =2). For example, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#4 to Tx#6 of PL2 polarization. 1，3 (m), ψ 2，3 (m), ψ 1，4 (m).

[0244] exist Fig. 9 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the PL1 polarized transmission antenna and the PL2 polarized transmission antenna is N. DM_PL1 =N DM_PL2 =2, which is the same. In addition, the Doppler frequency shift intervals of the DDM signals assigned to Tx#1~#3 of PL1 polarization are Δfd(1,2)=Δfd, Δfd(2,1)=3Δfd, and the Doppler frequency shift intervals of the DDM signals assigned to Tx#4~#6 of PL2 polarization are Δfd(3,4)=Δfd, Δfd(4,3)=3Δfd, which are the same (cyclically consistent).

[0245] therefore, Fig. 9 The setting of the CDP amount shown does not meet any of the DDM mode conditions of condition 1A.

[0246] In addition, Fig. 9 In the figure, the code indices assigned to each DDM signal using DOP1 to DOP4, the transmitting antenna polarized by PL1 and the transmitting antenna polarized by PL2 are CiPL1 = (1, 1&2, *), and CiPL2 = (, *, 1&2, 1), which are cyclically inconsistent and have different code index intervals, thus satisfying B-1 of condition 1.

[0247] In addition, Fig. 9 In the example, the code multiplexing numbers assigned to the DDM signals using DOP1 to DOP4, the PL1 polarized transmission antennas and the PL2 polarized transmission antennas are NcPL1 = (1, 2, 0, 0) and NcPL2 = (0, 0, 2, 1), respectively, which are cyclically inconsistent and have different code multiplexing numbers. Therefore, condition 1 B-2 is satisfied.

[0248] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. The code index at this time is CiPL1 alias =(2,1&2,*) and CiPL2 alias=(*,1&2,2), the two are different (circular inconsistency). Therefore, in Fig. 9 In the example, when the Doppler frequency of the target is -1 / (2Tr) ≤ f dtg <-1 / (2Tr), the code index is cyclically inconsistent and the code interval is different. Therefore, B-1 and B-2 that meet condition 1 meet different CDM mode conditions.

[0249] As mentioned above, Fig. 9 The setting of the CDP amount shown is an example of a setting that satisfies condition 1.

[0250] In addition, Fig. 9 In the PL1 polarized transmission antenna, the code multiplexing number assigned to each DDM signal is NcPL1 = (1, 2, 0, 0), and in the PL2 polarized transmission antenna, the code multiplexing number assigned to each DDM signal is NcPL2 = (0, 0, 2, 1). Both are multiplexed and transmitted with uneven code multiplexing numbers between DDM signals, and the code multiplexing number is included in 1 or more and N CM In the range below -1.

[0251] Therefore, in Fig. 9 In the example, signals transmitted from transmitting antennas of the same polarization (for example, PL1 polarization and PL2 polarization, respectively) are multiplexed and transmitted with a code multiplexing number that is not uniform between DDM signals, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig. 9 The setting of the CDP amount shown is a setting example that satisfies Condition 2 in both PL1 polarization and PL2 polarization.

[0252] For example, by Fig. 9 With the CDP amount setting shown, when the reflected wave of the target object with cross polarization with respect to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the transmission antenna of PL1 polarization and the transmission antenna of PL2 polarization at approximately the same level or within the range of several dB to 6 dB. Fig. 9 In the example, for signals transmitted from Nt (=6) transmission antennas consisting of PL1-polarized transmission antennas and PL2-polarized transmission antennas, CDDM transmission is performed using CDP amounts with non-uniform code Doppler multiplexing numbers for each DDM signal.

[0253] Therefore, the radar device 10 can demultiplex the CDDM signal based on the existing demultiplexing operation of the CDDM signal (for example, refer to Patent Document 7).

[0254] In addition, in Fig. 9Under the setting of the CDP amount shown in FIG. 1 , in the case of a target reflected wave with cross polarization relative to the receiving antenna, Fig.10 When the reflected wave of the target object includes the PL2 polarization as cross polarization as in (a) and Fig.10 When the target object reflected wave whose PL1 polarization is cross-polarized is included as in (b), the radar device 10 receives CDDM signals different from each other (for example, CDDM signals B-1 and B-2 satisfying condition 1).

[0255] For example, Fig.10 (a) indicates that the Doppler frequency of the reflected wave of the target object with PL2 polarization as cross polarization is f dtg = 0. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, when the Doppler frequency of the target object is -1 / (4Tr) ≤ f dtg <-1 / (4Tr), CiPL1=(1, 1&2, *, *). In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the code index assigned to each DDM signal is CiPL1 alias =(2, 1&2, *, *).

[0256] In addition, for example, Fig.10 (b) indicates that the Doppler frequency of the reflected wave of the target object with PL1 polarization as cross polarization is f dtg = 0. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, when the Doppler frequency of the target object is -1 / (4Tr) ≤ f dtg <-1 / (4Tr), CiPL2 = (*, 1 & 2, 1). In addition, when the Doppler frequency of the target is -1 / (2Tr) ≤ f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the code index assigned to each DDM signal is CiPL2 alias =(*,1&2,2).

[0257] As described above, in the case of a reflected wave from a target object that is cross-polarized relative to the polarization (e.g., LC polarization) of a receiving antenna, when the reception level of a received signal at a transmitting antenna corresponding to PL1 polarization decreases and when the reception level of a received signal at a transmitting antenna corresponding to PL2 polarization decreases, the reflected wave signal received by the radar device 10 is a CDDM signal of a pattern different from each other (e.g., a pattern of code index or code interval) even if each DDM signal is received while being cyclically shifted on the Doppler frequency axis due to the Doppler frequency of the target object.

[0258] Therefore, the radar device 10 can, for example, determine in the coded Doppler multiplexing and demultiplexing unit 212 described later whether a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the PL1 polarization (for example, LC polarization) or a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the PL2 polarization (for example, RC polarization) has occurred based on the peak value of the Doppler frequency detected after code demultiplexing.

[0259] In addition, for example, the PL1 polarized DDM signal is multiplexed and transmitted with an uneven code multiplexing number NcPL1 = (1, 2, 0, 0) among the DDM signals (for example, for 4 DDM signals, the code multiplexing numbers are 0, 1 or 2 respectively, so it can be regarded as uneven CDDM transmission).

[0260] Therefore, for example, when the coded Doppler multiplexing and demultiplexing unit 212 determines that the received signal is a received signal of a transmitting antenna corresponding to LC polarization (PL1 polarization), the radar device 10 can use the existing CDDM signal demultiplexing operation to demultiplex the CDDM signal.

[0261] Similarly, for example, PL2 polarized DDM signals are multiplexed and transmitted with an uneven code multiplexing number NcPL2 = (0, 0, 2, 1) among DDM signals (for example, for 4 DDM signals, the code multiplexing numbers are 0, 1 or 2 respectively, so it can be regarded as uneven CDDM transmission).

[0262] Therefore, for example, when the coded Doppler multiplexing and demultiplexing unit 212 determines that the received signal is a received signal of a transmission antenna corresponding to PL2 polarization, the radar device 10 can demultiplex the CDDM signal using the existing CDDM signal demultiplexing operation.

[0263] By operating the code Doppler multiplexing and demultiplexing unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output corresponding to the transmission antenna for each CDDM signal.

[0264] <Setting Example 3>

[0265] Setting example 3 is a setting example of the CDP amount in a case where condition 1 (different CDM mode condition) is satisfied but condition 2 is not satisfied. Fig.11 Indicates the number of transmitting antennas Nt = 3, N PL1 =2,N PL2 Example of setting the CDP amount in the phase rotation amount setting unit 105 when 1 = 1. Fig.11 In the figure, the black circles (●) represent the distribution of CDDM signals of the transmitting antennas (Tx#1 and Tx#2) with PL1 polarization, and the white circles (○) represent the distribution of CDDM signals of the transmitting antenna (Tx#3) with PL2 polarization.

[0266] In addition, Fig.11 In the Doppler multiplexing number N DM =2, the Doppler shift setting unit 106 can set the two DOP1 and DOP2 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig.11 The phase rotation amount given to DOP1 = 0 is The phase rotation amount given DOP2 = -Δfd like Fig.11 As shown, the Doppler multiplexing interval Δfd is an equal interval, Δfd=1 / (4Tr).

[0267] exist Fig.11 In the example, the number of transmitting antennas Nt = 3, the number of Doppler multiplexing N DM =2, code multiplexing number N CM =2, Nt <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the DDM signal unevenly. CDDM (ndm) (here, ndm = 1 to N DM ).

[0268] like Fig.11 As shown, in the coding unit 107, the coding Doppler multiplexing numbers for the DDM signals using both DOP1 and DOP2 input from the Doppler shift setting unit 106 are N and N, respectively. CDDM (1) = 1, N CDDM (2)=2. In this way, the phase rotation amount setting unit 105 sets the code-Doppler multiplexing number for the DDM signal unevenly.

[0269] In addition, Fig.11 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to Tx#1 and Tx#2 of PL1 polarization. DM = 2 DDM signal using Doppler shift amounts DOP1 and DOP2 (N DN_PL1=2). For example, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#1 to Tx#2 of PL1 polarization. 1，1 (m), ψ 1，2 (m).

[0270] In addition, Fig.11 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to Tx#3 of PL2 polarization. DM = 2 DDM signal using Doppler frequency shift amount DOP2 (N DM_PL2 =1), the phase rotation amount setting unit 105 sets the CDP amount ψ for Tx#3 of PL2 polarization. 2，2 (m).

[0271] exist Fig.11 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the PL1 polarized transmission antenna and the PL2 polarized transmission antenna is N. DM_PL1 =2, N DM_PL2 =1, which is a different Doppler multiplexing number. Therefore, Fig.11 The setting of the CDP amount shown corresponds to the different DDM mode conditions of A-2 of condition 1.

[0272] In addition, Fig.11 In the figure, the code indices CiPL1=(1,1) and CiPL2=(*,2) are respectively allocated to each DDM signal using DOP1 and DOP2, and to the transmitting antenna polarized by PL1 and the transmitting antenna polarized by PL2. They are cyclically inconsistent and have different code index intervals.

[0273] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. The code index at this time is CiPL1 alias =(2,2) and CiPL2 alias =(*, 1), the two are different (circular inconsistency). Therefore, in Fig.11 In the example, when the Doppler frequency of the target is -1 / (2Tr) ≤ f dtg <-1 / (2Tr), the code index is cyclically inconsistent and the code interval is different. Therefore, B-1 of condition 1 is satisfied.

[0274] In addition, Fig.11In the example, the code multiplexing numbers assigned to the DDM signals using DOP1 and DOP2, the PL1 polarized transmitting antenna and the PL2 polarized transmitting antenna are NcPL1 = (1, 1) and NcPL2 = (0, 1), respectively. The two cycles are inconsistent and the code multiplexing numbers are different. Therefore, B-2 of condition 1 is satisfied.

[0275] therefore, Fig.11 The setting of the CDP amount shown satisfies B-1 and B-2 of condition 1 and complies with different CDM mode conditions.

[0276] As mentioned above, Fig.11 The setting of the CDP amount shown is an example of a setting that satisfies condition 1.

[0277] In addition, Fig.11 In the PL1 polarized transmitting antenna, the code multiplexing number allocated to each DDM signal is NcPL1=(1,1), and multiplexing and transmission are performed with a uniform code multiplexing number among the DDM signals.

[0278] On the other hand, Fig.11 In the transmitting antenna of PL2 polarization, the code multiplexing number assigned to each DDM signal is NcPL2 = (0, 1), and the DDM signals are multiplexed and transmitted with uneven code multiplexing numbers, and the code multiplexing number is included in 1 or more and N CM In the range below -1.

[0279] Therefore, in Fig.11 In the example, the signal transmitted from the transmitting antenna of PL2 polarization is multiplexed and transmitted with a code multiplexing number that is not uniform between DDM signals, and the code multiplexing number is included in 1 or more and N CM -1 or less, and the code multiplexing number assigned to each DDM signal is uniform for the signal transmitted from the transmitting antenna with PL1 polarization. Fig.11 The setting of the CDP amount shown is a setting example in which condition 2 is satisfied with respect to PL2 polarization and condition 2 is not satisfied with respect to PL1 polarization.

[0280] For example, by Fig.11 With the CDP amount setting shown, when the reflected wave of the target object with cross polarization with respect to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the transmission antenna of PL1 polarization and the transmission antenna of PL2 polarization at approximately the same level or within the range of several dB to 6 dB. Fig.11 In the example, for signals transmitted from Nt (=3) transmission antennas consisting of PL1-polarized transmission antennas and PL2-polarized transmission antennas, CDDM transmission is performed using CDP amounts with non-uniform code Doppler multiplexing numbers for each DDM signal.

[0281] Therefore, the radar device 10 can demultiplex the CDDM signal based on the existing demultiplexing operation of the CDDM signal (for example, refer to Patent Document 7).

[0282] In addition, in Fig.11 Under the setting of the CDP amount shown in FIG. 1 , in the case of a target reflected wave with cross polarization relative to the receiving antenna, Fig.12 When the reflected wave of the target object includes the PL2 polarization as cross polarization as in (a) and Fig.12 When the target reflected wave whose PL1 polarization is cross-polarized is included as in (b), the radar device 10 receives CDDM signals different from each other (for example, CDDM signals 1A and 1B satisfying condition 1).

[0283] For example, Fig.12 (a) indicates that the Doppler frequency of the reflected wave of the target object with PL2 polarization as cross polarization is f dtg = 0. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, when the Doppler frequency of the target object is -1 / (4Tr) ≤ f dtg <-1 / (4Tr), CiPL1=(1,1), and when -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the code index assigned to each DDM signal is CiPL1 alias =(2,2).

[0284] In addition, for example, Fig.12 (b) indicates that the Doppler frequency of the reflected wave of the target object with PL1 polarization as cross polarization is f dtg = 0. In the radar device 10, each DDM signal is received after being cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target object. As for the code index assigned to each DDM signal, when the Doppler frequency of the target object is -1 / (4Tr) ≤ f dtg <-1 / (4Tr), CiPL2=(*,2). In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the code index assigned to each DDM signal is CiPL2 alias =(*,1).

[0285] As described above, in the case of a reflected wave from a target object having a cross-polarization relative to the polarization (e.g., LC polarization) of a receiving antenna, when the reception level of the received signal of the transmitting antenna corresponding to the PL1 polarization decreases and when the reception level of the received signal of the transmitting antenna corresponding to the PL2 polarization decreases, the reflected wave signal received by the radar device 10 is a CDDM signal having a different pattern (e.g., a pattern of Doppler multiplexing number, code interval, or code multiplexing number) even if each DDM signal is received while being cyclically shifted on the Doppler frequency axis due to the Doppler frequency of the target object.

[0286] Therefore, the radar device 10 can, for example, determine in the coded Doppler multiplexing and demultiplexing unit 212 described later whether a reduction in the reception level of the receiving signal of the transmitting antenna corresponding to the PL1 polarization (for example, LC polarization) or a reduction in the reception level of the receiving signal of the transmitting antenna corresponding to the PL2 polarization (for example, RC polarization) has occurred based on the peak value (for example, the number of peaks) of the Doppler frequency after the detected code demultiplexing.

[0287] In addition, for example, the DDM signal of PL1 polarization is multiplexed and transmitted with a uniform code multiplexing number NcPL1=(1, 1) between the DDM signals (for example, for two DDM signals, the code multiplexing number is 1, so it can be regarded as uniform CDDM transmission). Therefore, for example, when the result of the determination by the coded Doppler multiplexing demultiplexing unit 212 is that the received signal is a received signal corresponding to the transmitting antenna of LC polarization (PL1 polarization), the radar device 10 can use the existing DDM signal demultiplexing operation (for example, refer to patent document 5) to demultiplex the DDM signal. In this case, the radar device 10 can demultiplex the DDM signal at -1 / (2Loc N DM_PL1 Tr)≦fd<1 / (2Loc N DM_PL1 The Doppler frequency fd of the target object is determined within the range of Tr), and an output corresponding to the transmission antenna can be obtained for each CDDM signal.

[0288] In addition, for example, the DDM signal of PL2 polarization is multiplexed and transmitted with the code multiplexing number NcPL2=(0, 1) which is not uniform between the DDM signals (for example, the code multiplexing number is 0 or 1 for two DDM signals, respectively, so it can be regarded as non-uniform CDDM transmission). Therefore, for example, when the result of the determination by the coded Doppler multiplexing demultiplexing unit 212 is that the received signal is a received signal corresponding to the transmitting antenna of PL2 polarization, the radar device 10 can use the existing demultiplexing operation of the CDDM signal to demultiplex the CDDM signal.

[0289] By operating the coded Doppler multiplexing and demultiplexing unit 212 in this way, when it is determined that the received signal is a received signal of the transmitting antenna corresponding to the PL1 polarization, the radar device 10 can obtain -1 / (2Loc N DM_PL1 Tr)≦fd<1 / (2Loc N DM_PL1 The Doppler frequency fd of the target object is determined within the range of Tr), and an output corresponding to the transmission antenna can be obtained for each CDDM signal.

[0290] In addition, when a judgment result other than that the received signal is a received signal corresponding to a transmitting antenna with PL1 polarization is obtained, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output that corresponds to the transmitting antenna for each CDDM signal.

[0291] <Setting Example 4>

[0292] In the above setting examples 1 to 3, the number of multiplexing codes used is N. CM = 2 codes are described above, but the code multiplexing number is not limited to N CM =2, or other values. Fig.13 As shown, the code multiplexing number N is set CM =4.

[0293] Example 4 is a setting example in which the code length is 4 and condition 1 (different DDM mode conditions and different CDM mode conditions) is satisfied but condition 2 is not satisfied. CM An example of setting the CDP amount in the phase rotation amount setting unit 105 when φ=4 will be described.

[0294] Fig.13 Indicates the number of transmitting antennas Nt = 6, N PL1 =3,N PL2 Example of setting the CDP amount in the phase rotation amount setting unit 105 when φ = 3. Fig.13 In the figure, the black circles (●) represent the distribution of CDDM signals of the transmission antennas (Tx#1 to #3) of PL1 polarization, and the white circles (○) represent the distribution of CDDM signals of the transmission antennas (Tx#4 to #6) of PL2 polarization.

[0295] In addition, Fig.13 In the Doppler multiplexing number N DM =2, the Doppler shift setting unit 106 can set the two DOP1 and DOP2 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig.13 The phase rotation amount given to DOP1 = 0 is The phase rotation amount given DOP2 = -Δfd like Fig.13 As shown, the intervals Δfd between the DDM signals are equal intervals, Δfd=1 / (4Tr).

[0296] In addition, Fig.13 In the code multiplexing number N CM =4, the encoding unit 107 uses, for example, Code1={1, 1, 1, 1}, Code2={1, -1, 1, -1}, Code3={1, 1, -1, -1}, Code4={1, -1, -1, 1} which are orthogonal code sequences with a code length Loc=4 of the Walsh-Hadamard code.

[0297] exist Fig.13 In the embodiment, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#1 to Tx#3 of PL1 polarization. 1，1 (m), ψ 1，2 (m), ψ 2，2 (m), set the CDP value ψ for Tx#4~Tx#6 of PL2 polarization respectively 2，1 (m), ψ 3，1 (m), ψ 4，1 (m). Therefore, Fig.13 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the PL1 polarized transmission antenna and the PL2 polarized transmission antenna is N. DM _ PL1 =2,N DM _ PL2 =1, which is a different Doppler multiplexing number. Therefore, Fig.13 The setting of the CDP amount shown corresponds to the different DDM mode conditions of A-2 of condition 1.

[0298] In addition, Fig.13 In the example, the code indices CiPL1 = (1, 1 & 2) and CiPL2 = (2 & 3 & 4, *) are respectively assigned to the DDM signals using DOP1 and DOP2, and to the transmitting antennas polarized by PL1 and PL2, which are cyclically inconsistent and have different code index intervals. Fig.13 In the example, the code multiplexing numbers assigned to the DDM signals using DOP1 and DOP2 and the transmitting antennas polarized by PL1 and PL2 are NcPL1=(1,2) and NcPL2=(3,0), respectively, which are cyclically inconsistent and have different code multiplexing numbers. Therefore, Fig.13 The setting of the CDP amount shown satisfies B-1 and B-2 of condition 1 and complies with different CDM mode conditions.

[0299] therefore, Fig.13 The setting of the CDP amount shown is an example of a setting that satisfies condition 1.

[0300] In addition, Fig.13 In the example, the code multiplexing number assigned to each DDM signal in the transmitting antenna of PL1 polarization is NcPL1=(1,2), and the code multiplexing number assigned to each DDM signal in the transmitting antenna of PL2 polarization is NcPL2=(3,0). Both of them are multiplexed and transmitted with uneven code multiplexing numbers between DDM signals, and the code multiplexing number is included in 1 or more and N CM In the range of -1(=3) or less.

[0301] Therefore, in Fig.13 In the example, the signals transmitted from the transmission antennas of PL1 polarization and PL2 polarization are multiplexed and transmitted with a code multiplexing number that is not uniform between the DDM signals, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig.13 The setting of the CDP amount shown is a setting example in which condition 2 is satisfied for both PL1 polarization and PL2 polarization.

[0302] In the above, an example of setting the CDP amount in the phase rotation amount setting unit 105 has been described.

[0303] [Configuration of the radar receiving unit 200]

[0304] exist Figure 4 In the embodiment, the radar receiving unit 200 has a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. In addition, the radar receiving unit 200 includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a coded Doppler multiplexing and demultiplexing unit 212, and a direction estimation unit 213. In addition, the Na antenna system processing units 201-1 to 201-Na, the CFAR unit 211, the coded Doppler multiplexing and demultiplexing unit 212, and the direction estimation unit 213 can be collectively referred to as a "receiving circuit". In addition, the receiving circuit uses the reflected wave signal reflected by the transmission signal at the target (target) to estimate the direction of the target.

[0305] 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 object (object), and output the received reflected wave signals to the corresponding antenna system processing unit 201 as received signals.

[0306] Each antenna system processing unit 201 includes a reception radio unit 203 and a signal processing unit 206 .

[0307] Each signal received by Na receiving antennas Rx#1 to Rx#Na is output to Na receiving wireless units 203. In addition, output signals from Na receiving wireless units 203 are output to Na signal processing units 206, respectively.

[0308] The receiving wireless unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the chirp signal as the transmission signal input from the radar transmission signal generating unit 101 with the received reflected wave signal. The receiving wireless unit 203, for example, passes the output of the mixer unit 204 through the LPF 205. As a result, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is output. For example, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulation wave) as the transmission signal (radar transmission wave) and the frequency of the reception chirp signal (reception frequency modulation wave) as the reception signal (radar reflected wave) is obtained as a beat frequency.

[0309] The signal processing unit 206 in each antenna system processing unit 201 - z (where z=any one of 1 to Na) includes an AD conversion unit 207 , a beat frequency analysis unit 208 , an output switching unit 209 , and a Doppler analysis unit 210 .

[0310] The signal (for example, the beat signal) output from the LPF 205 is converted into discrete sample data by the AD converter 207 in the signal processing unit 206 through discrete sampling.

[0311] The beat frequency analysis unit 208 analyzes the N signals obtained within a predetermined time range (range gate) according to the transmission period Tr. data The signal processing unit 206 performs frequency analysis processing (for example, FFT processing) on ​​discrete sample data. As a result, the signal processing unit 206 outputs a frequency spectrum having a peak at a beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave).

[0312] Here, the beat frequency response obtained by transmitting the m-th chirped pulse and outputted from the beat frequency analysis unit 208 in the z-th signal processing unit 206 is represented by “RFT z (f b , m)”. Here, f b represents the beat frequency index, which corresponds to the index (bin number) of the FFT. b =0, ..., (N data / 2)-1, z=1~Na, m=1~N C . Beat frequency index f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (for example, the closer the distance to the target object).

[0313] In addition, the beat frequency index f b It can be converted into distance information R(f b ). Therefore, in the following, the beat frequency index f b It is called the “distance index f b ”.

[0314] [Formula 10]

[0315]

[0316] Here, B w represents the frequency modulation bandwidth within the range gate of the chirp signal, and C0 represents the speed of light. In addition, in equation (10), C0 / (2B w ) represents the distance resolution.

[0317] The output switching unit 209 selectively switches to the OC_INDEX-th Doppler analysis unit 210 among the Loc Doppler analysis units 210 based on the orthogonal code element index OC_INDEX input from the encoding unit 107 of the phase rotation amount setting unit 105 and outputs the output of the beat frequency analysis unit 208 in each transmission cycle.

[0318] The signal processing unit 206 includes Loc Doppler analysis units 210-1 to 210-Loc. For example, the noc-th Doppler analysis unit 210 receives data once in each Loc-th transmission cycle (Loc×Tr) through the operation of the output switching unit 209. Therefore, the noc-th Doppler analysis unit 210 uses data of the Ncode-th transmission cycle in the Nc-th transmission cycle (for example, the beat frequency response RFT input from the beat frequency analysis unit 208). z (f b , m)), index f by each distance b Doppler analysis is performed. Here, noc is the index of the code element, noc = 1 to Loc.

[0319] For example, when Ncode is a power of 2, FFT processing can be applied to Doppler analysis. Here, the FFT size is Ncode, and the maximum Doppler frequency that does not cause aliasing is ±1 / (2Loc×Tr) derived from the sampling theorem. In addition, the Doppler frequency index f s The Doppler frequency interval is 1 / (Ncode×Loc×Tr), and the Doppler frequency index f s The range is f s =-Ncode / 2,...,0,...,Ncode / 2-1.

[0320] Hereinafter, as an example, a case where Ncode is a power of 2 is described. In addition, when Ncode is not a power of 2, FFT processing can be performed with a power of 2 as the data size (FFT size), for example, by including zero-padding data.

[0321] For example, the output VFT of the Doppler analysis unit 210 of the z-th signal processing unit 206 is z noc (f b , f s ) is represented by the following formula (11). In addition, j is an imaginary unit, and z=1 to Na.

[0322] [Formula 11]

[0323]

[0324] The above describes the processing in each component of the signal processing unit 206.

[0325] [Operation Example of CFAR Unit 211]

[0326] exist Figure 4 In the example, the CFAR unit 211 uses the outputs of the Loc Doppler analysis units 210 of the first to Na signal processing units 206 to perform CFAR processing (for example, threshold determination in an adaptive manner) to extract the distance index (hereinafter referred to as f) that gives the peak signal. b_cf ) and the Doppler frequency index (hereinafter, expressed as f s_cf ) The CFAR unit 211 performs VFT analysis on the outputs of the Doppler analysis units 210 of the first to Na-th signal processing units 206. z noc (f b , f s ) implements power addition, performs two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (equivalent to relative velocity), or performs CFAR processing combined with one-dimensional CFAR processing (for example, the processing disclosed in non-patent document 2 can be applied).

[0327] For example, when using equation (5) as the formula for assigning DOP ndm The phase rotation amount In the case where the intervals of the Doppler frequency shift amounts in the Doppler frequency domain in the output of the Doppler analysis unit 210 are equal intervals, when the intervals of the Doppler frequency indexes, i.e., the intervals of the Doppler frequency shift amounts, are represented by ΔFD, ΔFD=Ncode / N DM Therefore, in the output of the Doppler analysis unit 210, peaks are detected at intervals of ΔFD for each DDM signal in the Doppler frequency domain.

[0328] Therefore, the CFAR unit 211 may divide each output of the Doppler analysis unit 210 into a range of intervals ΔFD of the Doppler frequency shift amount, and for each divided range, perform power addition at each signal peak position of the Doppler multiplexing as shown in the following equation (12) and then perform CFAR processing (for example, called "Doppler region compression CFAR processing"). In the reception processing here, f sc = -ΔFD / 2, ..., -ΔFD / 2-1. For example, when ΔFD = Ncode / N DM When f sc =Ncode / (2N DM ), ..., Ncode / (2N DM )-1. In addition, for example, Patent Document 6 and Patent Document 7 describe the Doppler region compression CFAR process, and the detailed description thereof is omitted here.

[0329] [Formula 12]

[0330]

[0331] The CFAR unit 211 using the Doppler region compression CFAR process sets a threshold in an adaptive manner, for example, and b_cf 、f sc_cf , and N DM The Doppler frequency index (f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) received power information PowerFT(f b_cf , f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD), nfd=1,...,N DM The signal is output to the coded Doppler multiplexing and demultiplexing unit 212 .

[0332] [Operation Example of the Coded Doppler Multiplexing and Demultiplexing Unit 212]

[0333] Next, Figure 4 An operation example of the coded Doppler multiplexing and demultiplexing unit 212 shown in FIG. 1 is described below. In addition, an example of the processing of the coded Doppler multiplexing and demultiplexing unit 212 when the Doppler region compression CFAR processing is used in the CFAR unit 211 is described below. Fig.14 2 is a flowchart showing an example of the demultiplexing operation in the code-Doppler multiplexing and demultiplexing unit 212 .

[0334] <Step A-1>

[0335] The coded Doppler multiplexing demultiplexing unit 212 performs coded Doppler multiplexing demultiplexing processing on the Nt CDDM signals, assuming that the reflected wave of the target object having a cross polarization with respect to the polarization of the receiving antenna is not included.

[0336] For example, the coded Doppler multiplexing and demultiplexing unit 212 uses the f input from the CFAR unit 211 to b_cf 、f sc_cf and N DM The receiving power information of the Doppler frequency index of the DDM signal is obtained, and the output of the Doppler analysis unit 210 is used to demultiplex the Nt signals sent by the CDDM, and to distinguish (for example, determine or identify) the transmitting antenna and the Doppler frequency (for example, Doppler speed or relative speed).

[0337] As described above, when the equal-interval Doppler frequency shift amount setting including the maximum equal-interval Doppler frequency shift amount setting is used, the encoding unit 107 of the phase rotation amount setting unit 105 does not set N DM The number of coded Doppler multiplexing N CDDM (1) N CDDM (2), ..., N CDDM (N DM )All are set to N CM Instead, at least one coded Doppler multiplexing number is set to be less than N. CM The value of (unevenly set).

[0338] For example, (1) the code Doppler multiplexing demultiplexing unit 212 performs code demultiplexing processing and detects that the code Doppler multiplexing number is set to a value greater than N. CM The aliasing determination is performed by detecting a small number of CDDM signals (for example, detecting unused CDDM signals not used in multiplex transmission). Then, (2) the coded Doppler demultiplexing unit 212 performs Doppler code demultiplexing processing on the CDDM signals used in multiplex transmission based on the aliasing determination result.

[0339] The operation of such a coded Doppler multiplexing and demultiplexing unit 212 is the same as the operation of a coded Doppler multiplexing and demultiplexing unit in a MIMO radar using existing coded Doppler multiplexing transmission, and is described in, for example, Patent Document 7, so the detailed operation description is omitted.

[0340] For example, in the case of the equal-interval Doppler frequency shift amount setting including the maximum equal-interval Doppler frequency shift amount setting, N is not set. DM The number of coded Doppler multiplexing N CDDM (1) N CDDM (2), ..., N CDDM (N DM )All are set to N CMInstead, at least one coded Doppler multiplexing number is set to be less than N. CM In the case of the value of fd, the Doppler frequency of the target object estimated in the range of -1 / (2Tr)≦fd<1 / (2Tr) can be detected by the operation of the above-mentioned code-Doppler multiplexing and demultiplexing unit 212 (for example, refer to Patent Document 7).

[0341] <Step A-2>

[0342] The coded Doppler multiplexing and demultiplexing unit 212 determines whether the Nt CDDM signals are detected normally. The coded Doppler multiplexing and demultiplexing unit 212 performs the process of step A-3 if the Nt CDDM signals are detected normally, and performs the process of step B-1 if they are not detected normally.

[0343] For example, in the process of step A-1, when a target object reflected wave is included whose PL1 polarization or PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna, Nt CDDM signals may not be detected normally.

[0344] For example, a polarization MIMO radar is constructed using two types of transmission antennas, PL1 polarization and PL2 polarization, and the phase rotation amount setting unit 105 is set to N DM_PL1 <N DM , or N DM_PL2 <N DM In the case of a target reflected wave containing PL1 polarization or PL2 polarization that is cross-polarized with respect to the polarization of the receiving antenna, N DM The difference in received power between the received powers of the Doppler frequency indices of the DDM signals is greater than a specified value, or a component whose received power is as low as the noise level is included. In this case, the number of CDDM signals detected by the coded Doppler multiplexing and demultiplexing unit 212 is less than N. DM Therefore, it is determined that the detection is not normal, and the processing of step B-1 is performed.

[0345] For example, for the PL1 polarized transmission antenna, the phase rotation amount setting unit 105 is set to N DM_PL1 =N DM In the case of a target reflected wave whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna, or in the case of a PL2 polarized transmitting antenna, the setting of the phase rotation amount setting unit 105 is N DM_PL2 =N DM In the case of a target reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna, N DMThe received power of the Doppler frequency index of each DDM signal is within the specified range. In this case, when the code demultiplexing process is performed, the unused CDDM signal that is not used in the multiplexed transmission is larger than the assumed (N CM ×N DM =Nt) more, the aliasing determination of the coding Doppler multiplexing and demultiplexing unit 212 fails, and it is difficult to normally detect Nt CDDM signals. CM ×N DM -Nt) or more unused CDDM signals that are not used in multiplex transmission are determined to be not normal detection, and the process of step B-1 is performed.

[0346] <Step A-3>

[0347] The coded Doppler multiplexing and demultiplexing unit 212 performs CDDM demultiplexing processing on the CDDM signal used in multiplex transmission based on the aliasing determination result, and then performs CDDM demultiplexing on the received signal Y. z (f b_cf , f sc_cf , ncm, ndm) and f b_cf and f sc_cf The two signals are outputted together to the direction estimation unit 213 .

[0348] Here, Y z (f b_cf , f sc_cf , ndc(ndm), ndm) is the f of the Doppler analysis unit 210 of the z-th antenna system processing unit 201 b_cf and f sc_cf The lieutenant general used DOP ndm and orthogonal code Code ndc(ndm) The output of the CDDM signal after demultiplexing (e.g., the CDDM demultiplexing result). z (f b_cf , f sc_cf , ndc(ndm), ndm) represents the received signal transmitted by the transmitting antenna Tx#[ndc(ndm), ndm] and reflected by the target object, thereby being received by the zth antenna system processing unit 201.

[0349] Here, z = 1 to Na, ncm = 1 to N CM In addition, ndm = 1 to N DM , ndc(ndm)=1~N CDDM (ndm).

[0350] Furthermore, the code-Doppler multiplexing and demultiplexing unit 212 may output information related to the Doppler frequency of the detected target object to the direction estimating unit 213 , for example.

[0351] Furthermore, when condition 2 is satisfied, the code-Doppler multiplexing and demultiplexing unit 212 can detect the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0352] <Step B-1>

[0353] The coded Doppler multiplexing and demultiplexing unit 212 assumes that the reflected wave of the target object including the PL2 polarization is cross-polarized with the polarization of the receiving antenna, and performs the demultiplexing for N PL1 CDDM demultiplexing processing of CDDM signals.

[0354] For example, the coded Doppler multiplexing and demultiplexing unit 212 uses the f input from the CFAR unit 211 to b_cf 、f sc_cf , and N DM The received power information of the Doppler frequency index of the DDM signal is demultiplexed using the output of the Doppler analysis unit 210. PL1 The signal transmitted by the CDDM is detected, and the transmitting antenna is determined (for example, determined or recognized) and the Doppler frequency (for example, Doppler velocity or relative velocity) is determined.

[0355] Here, in N DM There may be a case where the difference in received power between the Doppler frequency indices of the DDM signals is greater than a predetermined value, or there may be a case where (N DM -N DM_PL1 ) The received power is as low as the noise level. It should be noted that when the phase rotation amount setting unit 105 is set to N DM =N DM_PL1 In the case of , components whose received power is as small as the noise level are not included.

[0356] Therefore, the coded Doppler multiplexing and demultiplexing unit 212 receives, for example, N DM Among the received powers of the Doppler frequency indices of the DDM signals, extract the N signals with the highest power. DM_PL1 A DDM signal.

[0357] For example, in the case where the extracted power ranks first, DM_PL1When the Doppler multiplexing interval of the DDM signal coincides with the Doppler multiplexing interval assigned to the transmitting antenna of PL1 polarization, (1) the coded Doppler multiplexing demultiplexing unit 212 performs code demultiplexing processing and detects from the CDDM signal assigned to the transmitting antenna of PL1 polarization that the coded Doppler multiplexing number is set to a value greater than N. CM The aliasing judgment is performed by detecting a small number of CDDM signals (for example, detecting unused CDDM signals not used in multiplexed transmission of the transmitting antenna with PL1 polarization). Then, (2) the coded Doppler demultiplexing unit 212 performs Doppler code demultiplexing processing on the CDDM signals used in multiplexed transmission based on the aliasing judgment result.

[0358] The operation of such a coded Doppler multiplexing and demultiplexing unit 212 is the same as the operation of a coded Doppler multiplexing and demultiplexing unit in a MIMO radar using existing coded Doppler multiplexing transmission, and is described in, for example, Patent Document 7, so the detailed operation description is omitted.

[0359] In addition, by setting the CDP amount to satisfy condition 2, for example, through the operation of the above-mentioned coded Doppler multiplexing and demultiplexing unit 212, the Doppler frequency of the target object estimated in the range of -1 / (2Tr)≦fd<1 / (2Tr) can be detected (for example, Patent Document 7).

[0360] <Step B-2>

[0361] The coded Doppler multiplexing demultiplexing unit 212 determines whether the N-pair allocated to the PL1 polarization is detected normally. PL1 N transmitting antennas PL1 The coded Doppler multiplexing and demultiplexing unit 212 is N PL1 If the CDDM signal is detected normally, the process of step B-3 is performed, and if it is not detected normally, the process of step C-1 is performed. By making the setting of the CDP amount by the phase rotation amount setting unit 105 satisfy condition 1, the following determination process can be performed.

[0362] For example, in the process of step B-1, if the reflected wave of the target object whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna is not included, N may not be detected normally. PL1 A CDDM signal.

[0363] For example, in the case where the extracted power ranks first, DM_PL1 DDM signal and other power ranked later (N DM -N DM_PL1) When the power difference (or power ratio) between the two DDM signals does not reach a specified level or above, the coded Doppler multiplexing and demultiplexing unit 212 determines that the reflected wave of the target object whose PL2 polarization is cross-polarized relative to the polarization of the receiving antenna is not included, and performs processing in step C-1.

[0364] When the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (A-2) of condition 1A, the code-Doppler multiplexing / demultiplexing unit 212 can perform such a determination process.

[0365] In addition, the N with the most extracted power DM_PL1 When the Doppler multiplexing interval of the DDM signal does not match the Doppler multiplexing interval assigned to the transmitting antenna of PL1 polarization, the coded Doppler demultiplexing unit 212 determines that the target object reflected wave with PL2 polarization cross-polarized with respect to the polarization of the receiving antenna is not included, and performs the processing of step C-1.

[0366] When the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (A-1) or (A-3) of condition 1A, the code-Doppler multiplexing / demultiplexing unit 212 can perform such a determination process.

[0367] For example, it is assumed that the setting of the phase rotation amount setting section 105 is N for the PL1 polarized transmission antenna. DM_PL1 =N DM_PL2 At this time, in the case of a target reflected wave including PL1 polarization that is cross-polarized with respect to the polarization of the receiving antenna, N DM The received power of the Doppler frequency index of the DDM signal is within the specified range. In this case, when the code demultiplexing process is performed, the assumed N PL1 The code intervals or code multiplexing numbers of the CDDM signals are different. Therefore, the aliasing determination of the code Doppler multiplexing demultiplexing unit 212 fails, and it is difficult to normally detect N PL1 In this case, the coded Doppler multiplexing and demultiplexing unit 212 determines that it is not for N PL1 When the CDP amount setting by the phase rotation amount setting unit 105 satisfies (B-1) or (B-2) of condition 1B, the coded Doppler demultiplexing unit 212 can perform such a determination process.

[0368] <Step B-3>

[0369] The coded Doppler multiplexing demultiplexing unit 212 performs the processing result of step B-2 on the N corresponding to the PL1 polarization. PL1The CDDM demultiplexed CDDM signal used in the multiplexed transmission of the transmitting antennas is subjected to the CDDM demultiplexing process. z (f b_cf , f sc_cf , ncm, ndm) and f b_cf and f sc_cf The two signals are outputted together to the direction estimation unit 213 .

[0370] Here, YPL1 z (f b_cf , f sc_cf , ndc(ndm), ndm) is the f of the Doppler analysis unit 210 of the z-th antenna system processing unit 201 b_cf and f sc_cf The lieutenant general used DOP ndm and orthogonal code Code ndc(ndm) The output of the CDDM signal after demultiplexing (e.g., CDDM demultiplexing result). For example, YPL1 z (f b_cf , f sc_cf , ndc(ndm), ndm) represents the N corresponding to PL1 polarization PL1 The received signal is transmitted by the zth transmitting antenna Tx#[ndc(ndm), ndm] and reflected by the target object, and then received by the zth antenna system processing unit 201. Here, z=1~Na, ndm=1~N DM , ndc(ndm)=1~N CDDM (ndm), except for N assigned to PL1 polarization PL1 Except for the signal from the transmitting antenna, the output is zero.

[0371] Furthermore, the code-Doppler multiplexing and demultiplexing unit 212 may output the detected Doppler frequency of the target object to the direction estimating unit 213 .

[0372] Furthermore, when condition 2 is satisfied, the code-Doppler multiplexing and demultiplexing unit 212 can detect the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0373] <Step C-1>

[0374] The coded Doppler multiplexing and demultiplexing unit 212 assumes that the reflected wave of the target object whose PL1 polarization is cross-polarized with the polarization of the receiving antenna is included, and performs the demultiplexing for N PL2 CDDM demultiplexing processing of CDDM signals.

[0375] For example, the coded Doppler multiplexing and demultiplexing unit 212 generates the coded Doppler multiplexing and demultiplexing signals based on the f output of the CFAR unit 211. b_cf 、fsc_cf , and N DM The received power information of the Doppler frequency index of the DDM signal is demultiplexed using the output of the Doppler analysis unit 210. PL2 The signal transmitted by the CDDM is detected, and the transmitting antenna is determined (for example, determined or recognized) and the Doppler frequency (for example, Doppler velocity or relative velocity) is determined.

[0376] Here, in N DM There may be a case where the difference in received power between the Doppler frequency indices of the DDM signals is greater than a predetermined value, or there may be a case where (N DM -N DM_PL2 ) The received power is as low as the noise level. It should be noted that when the phase rotation amount setting unit 105 is set to N DM =N DM_PL2 In the case of , components whose received power is as small as the noise level are not included.

[0377] Therefore, the coded Doppler multiplexing and demultiplexing unit 212 receives, for example, N DM Among the received powers of the Doppler frequency indices of the DDM signals, extract the N signals with the highest power. DM_PL2 A DDM signal.

[0378] For example, in the case where the extracted power ranks first, DM_PL2 When the Doppler multiplexing interval of the DDM signal coincides with the Doppler multiplexing interval assigned to the transmitting antenna of PL2 polarization, (1) the coded Doppler multiplexing demultiplexing unit 212 performs code demultiplexing processing and detects that the coded Doppler multiplexing number is set to a value greater than N from the CDDM signal assigned to the transmitting antenna of PL2 polarization. CM The aliasing judgment is performed by detecting a small number of CDDM signals (for example, detecting unused CDDM signals not used in multiplexed transmission of the transmitting antenna of PL2 polarization). Then, (2) the coded Doppler demultiplexing unit 212 performs Doppler code demultiplexing processing on the CDDM signals used in multiplexed transmission based on the aliasing judgment result.

[0379] The operation of such a coded Doppler multiplexing and demultiplexing unit 212 is the same as the operation of a coded Doppler multiplexing and demultiplexing unit in a MIMO radar using existing coded Doppler multiplexing transmission, and is described in, for example, Patent Document 7, so the detailed operation description is omitted.

[0380] In addition, by setting the CDP amount to satisfy condition 2, for example, through the operation of the above-mentioned coded Doppler multiplexing and demultiplexing unit 212, the Doppler frequency of the target object estimated in the range of -1 / (2Tr)≦fd<1 / (2Tr) can be detected (for example, Patent Document 7).

[0381] <Step C-2>

[0382] The coded Doppler multiplexing demultiplexing unit 212 determines whether the N-pair allocated to the PL2 polarization is detected normally. PL2 N transmitting antennas PL2 The coded Doppler multiplexing and demultiplexing unit 212 is N PL2 If the CDDM signal is detected normally, the process of step C-3 is performed, and if it is not detected normally, the process of step D is performed. This is because the coded Doppler multiplexing demultiplexing unit 212 regards this as the received signal having a large noise component (for example, low SNR) or including an interference component.

[0383] For example, in the case where the extracted power ranks first, DM_PL2 DDM signal and other power ranked later (N DM -N DM_PL2 ) When the power difference (or power ratio) between the two DDM signals does not reach a specified level or above, the coded Doppler multiplexing and demultiplexing unit 212 determines that the target reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is not included, and performs processing in step D.

[0384] In addition, the N with the most extracted power DM_PL2 When the Doppler multiplexing interval of the DDM signal does not match the Doppler multiplexing interval assigned to the transmitting antenna of PL2 polarization, the coded Doppler demultiplexing unit 212 determines that the target object reflected wave with PL1 polarization cross-polarized with respect to the polarization of the receiving antenna is not included, and performs the processing of step D.

[0385] In addition, the coded Doppler multiplexing and demultiplexing unit 212 extracts, for example, N of the top power. DM_PL2 DDM signals, based on the received power of the signal obtained by implementing the code demultiplexing process, determine the difference with the assumed N PL2 If they do not match, it is determined that the target reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is not included, and the processing of step D is performed.

[0386] <Step C-3>

[0387] The coded Doppler multiplexing demultiplexing unit 212 performs the processing result of step C-2 on the N corresponding to the PL2 polarization. PL2 The received signal YPL2 obtained by CDDM demultiplexing of the CDDM signal used in the multiplexed transmission of the transmitting antennas z (f b_cf , fsc_cf , ncm, ndm) and f b_cf and f sc_cf The two signals are outputted together to the direction estimation unit 213 .

[0388] Here, YPL2 z (f b_cf , f sc_cf , ndc(ndm), ndm) is the f of the Doppler analysis unit 210 of the z-th antenna system processing unit 201 b_cf and f sc_cf The lieutenant general used DOP ndm and orthogonal code Code ndc(ndm) The output of the CDDM signal after demultiplexing (e.g., CDDM demultiplexing result). For example, YPL2 z (f b_cf , f sc_cf , ndc(ndm), ndm) represents the N corresponding to PL2 polarization PL2 The received signal is transmitted by the zth transmitting antenna Tx#[ndc(ndm), ndm] and reflected by the target object, and then received by the zth antenna system processing unit 201. Here, z=1~Na, ndm=1~N DM , ndc(ndm)=1~N CDDM (ndm), except for N assigned to the PL2 polarization PL2 Except for the signal from the transmitting antenna, the output is zero.

[0389] Furthermore, the code-Doppler multiplexing and demultiplexing unit 212 may output the detected Doppler frequency of the target object to the direction estimating unit 213 .

[0390] Furthermore, when condition 2 is satisfied, the code-Doppler multiplexing and demultiplexing unit 212 can detect the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0391] <Step D>

[0392] When the condition of step C-2 is not satisfied, the coded Doppler multiplexing and demultiplexing unit 212 may determine that the received signal is a noise component or an interference component and may not output it to the direction estimation unit 213 .

[0393] In the above, an operation example of the code-Doppler multiplexing and demultiplexing unit 212 has been described.

[0394] In addition, when f is input from the CFAR unit 211, b_cf , Doppler frequency index f sc_cfWhen there are multiple pieces of received power information, the coded Doppler multiplexing and demultiplexing unit 212 may perform the above-mentioned CDDM demultiplexing operation multiple times on the distance index, the Doppler frequency index and the received power information, for example.

[0395] [Operation Example of Direction Estimation Unit 213]

[0396] Next, Figure 4 The operation example of the direction estimation unit 213 shown in FIG. 2 is described below.

[0397] The direction estimation unit 213 generates a signal (for example, f b_cf , the received signal Y after CDDM demultiplexing z (f b_cf , f sc_cf , ndc(ndm), ndm) or YPLq z (f b_cf , f sc_cf , ndc(ndm), ndm)), and perform the object direction estimation process. Here, q = 1 to NPL.

[0398] In addition, the received signal Y after CDDM demultiplexing processing z (f b_cf , f sc_cf , ndc(ndm), ndm) is derived from the CDP quantity ψ ndc(ndm)，ndm (m), so it can correspond to Tx#1, Tx#2, ..., Tx#Nt. Therefore, in the following, for the received signal Y z (f b_cf , f sc_cf , the CDP amount ψ in ndc(ndm),ndm) ndc(ndm)，ndm (m) It is also possible to use the expression YT corresponding to any one of Tx#1 to Tx#Nt. z (f b_cf , f sc_cf , nt). Here, nt = 1 to Nt.

[0399] Similarly, for the received signal YPLq z (f b_cf , f sc_cf , the CDP amount ψ in ndc(ndm),ndm) ndc(ndm)，ndm (m) It is also possible to use the expression YPLT corresponding to any one of Tx#1 to Tx#Nt. z (f b_cf , f sc_cf , nt).

[0400] Hereinafter, operation example 1 and operation example 2 of the direction estimation unit 213 will be described.

[0401] <Operation Example 1 of Direction Estimation Unit 213>

[0402] In operation example 1, the direction estimation unit 213 estimates the direction of the object according to f. b_cf And the received signal Y after CDDM demultiplexing z (f b_cf , f sc_cf , ndc(ndm), ndm), generates the virtual receiving array correlation vector h(f b_cf , f sc_cf ) and perform direction estimation processing.

[0403] Here, the information input from the code Doppler multiplexing and demultiplexing unit 212 includes the received signal Y after CDDM demultiplexing processing. z (f b_cf , f sc_cf , ndc(ndm), ndm), contains the CDDM demultiplexed receive signals for Nt transmit antennas. Therefore, the virtual receive array correlation vector h(f b_cf , f sc_cf ) contains Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. The direction estimation unit 213 uses the virtual receiving array correlation vector h(f b_cf , f sc_cf ) and estimate the direction of the reflected wave signal from the target based on the phase difference between each transmitting and receiving antenna.

[0404] In order to perform the direction estimation process for each polarized transmitting antenna, the direction estimation unit 213 obtains the virtual receiving array correlation vector h(f b_cf , f sc_cf ) extracts the received signal corresponding to the transmitting antenna with the same polarization to generate the virtual receiving array correlation vector h based on the transmitting antenna with PLq polarization PLq (f b_cf , f sc_cf ). Here, h PLq (f b_cf , f sc_cf ) is included N PLq ×Na-element column vector.

[0405] The direction estimation unit 213 uses, for example, a virtual receiving array correlation vector h of the transmitting antenna based on the PLq polarization. PLq (f b_cf , f sc_cf ), change the direction within the specified angle range to estimate the evaluation function P H-PLq (θu , f b_cf , f sc_cf ) in the azimuth direction θ u , to calculate the spatial distribution of PLq polarization.

[0406] The direction estimation unit 213 can extract a predetermined number of maximum peaks from the calculated maximum peaks of the spatial distribution of each PLq polarization in descending order, and output the azimuth direction of the maximum peak as the arrival direction estimation value of the PLq polarization (for example, positioning output). Here, q=1 to NPL.

[0407] In addition, regarding the direction estimation evaluation function value P H-PLq (θ u , f b_cf , f sc_cf ), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0408] In addition, it is also possible to estimate the direction of arrival in the azimuth direction and the elevation direction by using a MIMO virtual receiving antenna configuration arranged in a rectangular grid. For example, the direction estimation unit 213 can also calculate the azimuth direction and the elevation direction for each different polarized transmitting antenna as the estimated value of the direction of arrival, and output it as positioning. In addition, this point can also be applied to the action example 2 of the direction estimation unit 213 described later.

[0409] Through the above operation, the direction estimation unit 213 of the radar device 10 can output the positioning result according to, for example, f b_cf And the received signal Y after CDDM demultiplexing z (f b_cf , f sc_cf , ndc(ndm), ndm), and outputs the estimated value of the arrival direction. In addition, as the positioning output, the direction estimation unit 213 can also output f b_cf This point can also be applied to the second operation example of the direction estimation unit 213 described later.

[0410] In addition, we can also use formula (10) to convert f b_cf This is converted into distance information and outputted. This point can also be applied to the operation example 2 of the direction estimation unit 213 described later.

[0411] In addition, the information (for example, f b_cf , and the received signal Y after CDDM demultiplexing z (f b_cf , f sc_cf, ndc(ndm), ndm) exist in multiple cases, the direction estimation unit 213 can calculate the estimated value of the arrival direction for them in the same way as the above process, and output the positioning result. In addition, this point can also be applied to the action example 2 of the direction estimation unit 213 described later.

[0412] <Operation Example 2 of Direction Estimation Unit 213>

[0413] In operation example 2, the direction estimation unit 213 estimates the direction of the object according to f b_cf And the received signal YPLq after CDDM demultiplexing z (f b_cf , f sc_cf , ndc(ndm), ndm), generates the virtual receiving array correlation vector hq(f b_cf , f sc_cf , ndc(ndm), ndm), and perform direction estimation processing based on the received signal from the transmitting antenna with PLq polarization.

[0414] The direction estimation unit 213 performs CDDM demultiplexing on the received signal YPLq. z (f b_cf , f sc_cf , ndc(ndm), ndm) are consistent with each other in that the direction estimation process of the PLq polarization corresponding to q is different from the operation in operation example 1. z (f b_cf , f sc_cf , ndc(ndm), ndm) is replaced by the received signal YPLq z (f b_cf , f sc_cf , ndc(ndm), ndm) and the subsequent processing is the same, so the detailed description of this action is omitted.

[0415] Through the above operation, the direction estimation unit 213 of the radar device 10 can output the positioning result according to, for example, f b_cf and the received signal YPLq after CDDM demultiplexing as the received signal from the transmitting antenna polarized at PLq z (f b_cf , f sc_cf , ndc(ndm), ndm), outputs the direction of arrival estimate based on PLq polarization.

[0416] In the above, operation example 1 and operation example 2 of the direction estimation unit 213 have been described.

[0417] Through the above-described operations, the direction estimation unit 213 can perform direction estimation processing based on the output corresponding to the demultiplexing operation of the coded Doppler multiplexing and demultiplexing unit 212 .

[0418] For example, the direction estimation unit 213 can perform direction estimation processing based on the output of the coded Doppler multiplexing and demultiplexing unit 212 corresponding to the following situations, namely, a situation that does not include a target reflection wave with a cross-polarization relative to the polarization of the receiving antenna, a situation that includes a target reflection wave with a PL2 polarization that is cross-polarized relative to the polarization of the receiving antenna, and a situation that includes a target reflection wave with a PL1 polarization that is cross-polarized relative to the polarization of the receiving antenna.

[0419] In addition, for example, when the reflected wave of the target object whose polarization is cross-polarized with respect to the receiving antenna is not included, the direction estimation unit 213 can perform the direction estimation processing for each polarization included in the transmitting antenna. In addition, for example, when the reflected wave of the target object whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna is included, the direction estimation unit 213 can perform the direction estimation processing of the PL1 polarized transmission. In addition, for example, when the reflected wave of the target object whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is included, the direction estimation unit 213 can perform the direction estimation processing of the PL2 polarized transmission.

[0420] By the operation of the direction estimation unit 213, the direction estimation result for a part of the transmission polarization is obtained according to the direction estimation processing result of each transmission polarization or the state of the reflected wave, and the direction estimation result depending on the transmission polarization is obtained. Since the reflected wave response from the target object may change according to the transmission polarization, based on such a direction estimation result depending on the transmission polarization, the radar device 10 can improve the detection performance or recognition performance of the target object.

[0421] In the above, an operation example of the direction estimation unit 213 has been described.

[0422] As described above, in the present embodiment, the radar device 10 allocates CDDM signals that satisfy at least condition 1 and that are different between polarizations (for example, signals that are different in at least one of the DDM mode and the CDM mode) in the phase rotation amount setting unit 105 in the polarization transmission MIMO radar using CDDM. As a result, in the radar device 10, even when the reception levels of reflected waves corresponding to transmission antennas of different polarizations are greatly different, the transmission antenna can be identified in the coded Doppler multiplexing demultiplexing unit 212, and CDDM demultiplexing can be performed. Therefore, according to the present embodiment, it is possible to suppress degradation of target detection performance, misestimation of Doppler frequency, or degradation of angle measurement performance.

[0423] In addition, for example, when the aforementioned conditions 1 and 2 are satisfied in the allocation of the CDDM signal in the phase rotation amount setting unit 105, in the radar device 10, even when the reception levels of the reflected waves corresponding to the transmitting antennas with different polarizations are greatly different, the detectable Doppler frequency range fd is within the range of -1 / (2Tr)≦fd<1 / (2Tr), and can be expanded to the same Doppler frequency range as that when a single transmitting antenna is used.

[0424] Therefore, according to the present embodiment, the detection performance of the polarization MIMO radar using coded Doppler multiplexing transmission can be improved.

[0425] In addition, in the present embodiment, the radar device 10 has a receiving antenna that uses one of a plurality of polarizations (e.g., PL1 polarization and PL2 polarization) to receive a reflected wave signal formed by the radar transmission signal reflected from the target object. Furthermore, the radar device 10 estimates the direction based on the reflected wave signal received by the receiving antenna. Thus, even in the case of a reflected wave that includes a cross-polarization relationship with the polarization of the receiving antenna, the radar device 10 can identify the transmitting antenna corresponding to the DDM signal, and can resolve the ambiguity of the Doppler frequency. In addition, in the present embodiment, even if the receiving antennas are all receiving antennas of the same polarization, CDDM demultiplexing can be performed, so there is no need to use different types of polarized receiving antennas in the radar receiving unit 200, and the number of receiving antennas can be reduced.

[0426] (Variant 1)

[0427] In the above embodiment, as an example, an operation example of the CFAR unit 211, the coded Doppler multiplexing / demultiplexing unit 212, and the direction estimation unit 213 is described when the multiple receiving antennas of the receiving antenna unit 202 are receiving antennas of the same polarization.

[0428] The multiple receiving antennas of the receiving antenna unit 202 may include receiving antennas of different polarizations. In Modification 1, an operation example of the CFAR unit, the coded Doppler multiplexing and demultiplexing unit, and the direction estimation unit when the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations is described.

[0429] For example, when multiple receiving antennas include receiving antennas with different polarizations, there may be a situation where the reception levels of the target reflected waves are greatly different according to the different polarizations. Therefore, for example, the radar device 10 may perform CFAR processing, Doppler demultiplexing processing, and direction estimation processing on the outputs of the Doppler analysis unit 210 corresponding to the receiving antennas with different polarizations (for example, the reflected wave signals respectively received by the receiving antennas with each polarization). In addition, the direction estimation processing may also be performed using the output of the following Doppler demultiplexing processing, which is based on the Doppler demultiplexing processing of the receiving antennas with multiple polarizations.

[0430] Hereinafter, as an example, a case where the receiving antennas Rx#1 to Rx#Na of the receiving antenna unit 202 include at least two receiving antennas with different polarizations will be described.

[0431] For example, two different polarizations are expressed as "RxPL1 polarization" and "RxPL2 polarization". Also, suppose that among Na receiving antennas, the number of receiving antennas for RxPL1 polarization is N. RxPL1 The number of receiving antennas with RxPL2 polarization is N RxPL2 Here, N RxPL1 +N RxPL2 =Na.

[0432] Fig.15 1 is a block diagram showing a configuration example of a CFAR unit 211a, a coded Doppler multiplexing / demultiplexing unit 212a, and a direction estimation unit 213a of a radar receiving unit 200a in a radar device 10 according to Modification 1. Fig.15 As an example, receiving antennas Rx#1 to Rx#N RxPL1 The receiving antenna is polarized with RxPL1, Rx#N RxPL1 +1 to Rx#Na are the receiving antennas of RxPL2 polarization. Fig.15 Example shown.

[0433] In addition, if Fig.15 As shown, Doppler multiplexing can be demultiplexed using peak detection results of receiving antennas with the same polarization. In addition, power addition operations between two receiving antennas with different polarizations do not need to be performed, thereby achieving an effect of reducing the amount of calculation in the radar receiving unit 200a.

[0434] For example, among the outputs of the Na Doppler analysis unit 210, the 1st to the Nth RxPL1 The output of the Doppler analysis unit 210 corresponds to the reception signal of the reception antenna of RxPL1 polarization, and is input to the first CFAR unit 211 a - 1 that performs CFAR processing on the reception signal of RxPL1 polarization.

[0435] For example, among the outputs of the Na Doppler analysis unit 210, the Rx#N RxPL1 The outputs of the +1st to Nath Doppler analysis units 210 correspond to the reception signal of the reception antenna of RxPL2 polarization, and are input to the second CFAR unit 211 a - 2 that performs CFAR processing on the reception signal of RxPL2 polarization.

[0436] The first coded Doppler multiplexing / demultiplexing unit 212a-1 generates a first coded Doppler multiplexing / demultiplexing unit 212a-1 based on, for example, the f input from the first CFAR unit 211a-1. b_cf 、f sc_cf , and N DM The Doppler frequency index (f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) received power information PowerFT RxPL1 (f b_cf , f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD)(where nfd=1~N DM ), using the 1st to Nth receiving signals of the receiving antenna with RxPL1 polarization RxPL1 The output of the Doppler analysis unit 210 is converted into N t The signal transmitted by the CDDM is demultiplexed, and the transmitting antenna is determined (e.g., determined or identified) and the Doppler frequency (e.g., Doppler velocity or relative velocity) is determined. Figure 4 Compared with the coded Doppler multiplexing and demultiplexing unit 212, the operation of the first coded Doppler multiplexing and demultiplexing unit 212a-1 is based on the 1st to Nth RxPL1 The Doppler analysis unit 210 differs in that it outputs reception power information, and other operations may be the same as those of the coded Doppler multiplexing / demultiplexing unit 212 .

[0437] The second coded Doppler multiplexing / demultiplexing unit 212a-2 is based on, for example, the output of the second CFAR unit 211a-2. b_cf 、f sc_cf , and N DM The Doppler frequency index (f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) received power information PowerFT RxPL2 (f b_cf , f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD)(where nfd=1~N DM), using the Nth receiving signal of the receiving antenna with RxPL2 polarization RxPL1 +1~Nth a The output of the Doppler analysis unit 210 is converted into N t The signal transmitted by the CDDM is demultiplexed, and the transmitting antenna is determined (e.g., determined or identified) and the Doppler frequency (e.g., Doppler velocity or relative velocity) is determined. Figure 4 Compared with the coded Doppler multiplexing and demultiplexing unit 212, the second coded Doppler multiplexing and demultiplexing unit 212a-2 uses the N-based RxPL1 ~Nth a The Doppler analysis unit 210 differs in that it outputs reception power information, and other operations may be the same as those of the coded Doppler multiplexing / demultiplexing unit 212 .

[0438] Next, an operation example of the first direction estimation unit 213a-1 and the second direction estimation unit 213a-2 is described. Below, the first direction estimation unit 213a-1 and the second direction estimation unit 213a-2 are described as "y-th direction estimation unit 213a" for a general description. Here, y=1 or 2. The y-th direction estimation unit 213a performs a direction estimation process of the target object based on the input signal from the y-th coded Doppler multiplexing and demultiplexing unit 212a.

[0439] Next, operation examples 1 and 2 of the y-direction estimation unit 213 a will be described.

[0440] <Operation Example 1 of the Y-Direction Estimation Unit 213a>

[0441] For example, the y-th direction estimation unit 213a uses the f of the signal input from the y-th coded Doppler multiplexing and demultiplexing unit 212a. b_cf and the received signal Y after CDDM demultiplexing z (f b_cf , f sc_cf , ndc(ndm), ndm), generates the virtual receiving array correlation vector h of the y-direction estimation unit 213a RxPLy (f b_cf , f b_comp_cf ), and perform direction estimation processing. Here, y=1 or 2.

[0442] Virtual receiving array correlation vector h RxPLy (f b_cf , f b_comp_cf ) includes the number of transmitting antennas Nt and the number of receiving antennas N of RxPLy polarization RxPLy The product of Nt×N RxPLy The y-direction estimation unit 213a uses the virtual reception array correlation vector h RxPLy (fb_cf , f b_comp_cf ) and estimate the direction of the reflected wave signal from the target based on the phase difference between each transmitting and receiving antenna.

[0443] For example, in order to perform the direction estimation process for each polarized transmission antenna, the y-direction estimation unit 213a calculates the virtual reception array correlation vector h RxPLy (f b_cf , f sc_cf ) to extract the received signal corresponding to the transmitting antenna of the same polarization, and generate the virtual receiving array correlation vector h based on the transmitting antenna of PLq polarization PLq，RxPLy (f b_cf , f sc_cf ). Here, h PLq，RxPLy (f b_cf , f sc_cf ) is a PLq ×N RxPLy Column vector of elements.

[0444] The y-direction estimation unit 213a can use, for example, a virtual receiving array correlation vector h of the transmitting antenna based on the PLq polarization. PLq，RxPLy (f b_cf , f sc_cf ) performs direction estimation processing and outputs it as an estimated value of the arrival direction of the receiving antenna based on the RxPLy polarization for each PLq polarization (for example, a positioning output).

[0445] Through the above operation, the y-th direction estimation unit 213a can output, as a positioning output, for example, the signal f input from the y-th coded Doppler multiplexing and demultiplexing unit 212a. b_cf and the received signal Y after CDDM demultiplexing z (f b_cf , f sc_cf , ndc(ndm), ndm), for each different polarized transmitting antenna, based on the estimated value of the receiving antenna of RxPLy polarization. In addition, as the positioning output, the y-direction estimation unit 213a can also output f b_cf .

[0446] <Operation Example 2 of the Y-Direction Estimation Unit 213a>

[0447] For example, the y-th direction estimation unit 213a uses the f input from the y-th coded Doppler multiplexing and demultiplexing unit 212a. b_cf and the received signal YPLq subjected to CDDM demultiplexing processing z (f b_cf , f sc_cf, ndc(ndm), ndm), generates the virtual receiving array correlation vector h based on the transmit antenna of Plq polarization PLq，RxPLy (f b_cf , f sc_cf ), and performs direction estimation processing. The y-direction estimation unit 213a performs, for example, CDDM processing on the received signal YPLq z (f b_cf , f sc_cf , ndc(ndm), ndm) corresponding to the direction estimation processing of the polarization (PLq polarization).

[0448] The y-direction estimation unit 213a performs CDDM processing on the received signal YPLq. z (f b_cf , f sc_cf , ndc(ndm), ndm) are consistent with the operation example 1 in that the direction estimation process of the polarization corresponding to q (PLq polarization) is different from the operation example 1. The operation in this case is different from the operation in the operation example 1 in that the received signal Y z (f b_cf , f sc_cf , ndc(ndm), ndm) is replaced by the received signal YPLq z (f b_cf , f sc_cf , ndc(ndm), ndm) is the same as the case where processing is performed, so detailed description of the action is omitted.

[0449] Through the above operation, the y-th direction estimation unit 213a can, for example, calculate the f input from the y-th coded Doppler multiplexing and demultiplexing unit 212a. b_cf and the received signal YPLq subjected to CDDM demultiplexing processing z (f b_cf , f sc_cf The received signal from the transmitting antenna of PLq polarization in ndc(ndm), ndm) is output as the positioning output. In addition, the y-direction estimation unit 213a can also output f b_cf .

[0450] In the above, the operation example 1 and the operation example 2 of the y-direction estimation unit 213 a have been described.

[0451] The y-direction estimation unit 213a can obtain the direction estimation result of the receiving antenna based on the RxPLy polarization for part of the transmission polarization according to the result of the direction estimation processing of the receiving antenna based on the RxPLy polarization of each transmission polarization or the state of the reflected wave through the above-mentioned operation, and can obtain the direction estimation result depending on the transmission polarization antenna and the reception polarization antenna. Since the reflected wave response from the target object may change according to the transmission polarization and the reception polarization, based on such a direction estimation result depending on the transmission and reception polarization, the radar device 10 can improve the detection performance or recognition performance of the target object.

[0452] Here, the y-direction estimation unit 213a performs the multiplication of the y-direction signals based on the signal (for example, f b_cf , the received signal Y after CDDM demultiplexing z (f b_cf , f sc_cf , ndc(ndm), ndm) or f sc_cf ), and the output of the Doppler analysis unit 210 corresponding to these distances and Doppler demultiplexing indices, to perform object direction estimation processing, but is not limited to this.

[0453] For example, the y-direction estimating unit 213a may perform a target object direction estimation process based on the signal input from the first code-Doppler multiplexing / demultiplexing unit 212a-1 and the signal input from the second code-Doppler multiplexing / demultiplexing unit 212a-2.

[0454] For example, the y-direction estimation unit 213a uses the signal input from the first coded Doppler multiplexing and demultiplexing unit 212a-1 to calculate the virtual reception array correlation vector h based on the reception signal transmitted from the transmission antenna of PL1 polarization and received by the reception antenna of RxPL1 polarization. PL1，RxPL1 (f b_cf , f sc_cf ). In addition, the y-direction estimation unit 213a uses the signal input from the second coded Doppler multiplexing and demultiplexing unit 212a-2 to calculate the virtual reception array correlation vector h based on the reception signal transmitted from the transmission antenna of PL2 polarization and received by the reception antenna of RxPL2 polarization. PL2，RxPL2 (f b_cf , f sc_cf ). Then, the y-direction estimation unit 213a may be configured to calculate the virtual receiving array correlation vector h PL1，RxPL1 (f b_cf , f sc_cf ) and the virtual receiving array correlation vector h PL2，RxPL2 (f b_cf , f sc_cf ), and perform the object direction estimation process.

[0455] Alternatively, for example, the y-direction estimation unit 213a uses the signal input from the first coded Doppler multiplexing and demultiplexing unit 212a-1 to calculate a virtual reception array correlation vector h based on a reception signal transmitted from a transmission antenna of PL2 polarization and received by a reception antenna of RxPL1 polarization. PL2，RxPL1 (f b_cf , f sc_cf ). In addition, the y-direction estimation unit 213a uses the signal input from the second coded Doppler multiplexing and demultiplexing unit 212a-2 to calculate the virtual reception array correlation vector h based on the reception signal transmitted from the transmission antenna of PL1 polarization and received by the reception antenna of RxPL2 polarization. PL1，RxPL2 (f b_cf , f sc_cf ). Then, the y-direction estimation unit 213a may be configured to calculate the virtual receiving array correlation vector h PL2，RxPL1 (f b_cf , f sc_cf ) and h PL1，RxPL2 (f b_cf , f sc_cf ), and perform the object direction estimation process.

[0456] (Variant 2)

[0457] In the above-mentioned embodiment, the example of using two polarizations, PL1 polarization and PL2 polarization, which are orthogonal to each other, as the transmission polarizations of different polarizations is described, but it is not limited to this, and the number of polarizations may be more than 3. For example, in addition to the two polarizations, PL1 polarization and PL2 polarization, a transmission antenna with other polarizations different from PL1 polarization and PL2 polarization may be used.

[0458] For example, the radar device 10 (for example, a polarization MIMO radar) may use Nt transmission antennas including three or more transmission antennas with different polarizations including two polarizations that are orthogonal to each other.

[0459] Hereinafter, the first polarization is described as "PL1 polarization", and the second polarization is described as "PL2 polarization". The qth polarization is described as "PLq polarization". In addition, it is assumed that the combination of different polarizations in a mutually orthogonal polarization relationship is PL1 polarization and PL2 polarization, for example, right-hand circular polarization and left-hand circular polarization, horizontal polarization and vertical polarization, right slant 45° polarization and left slant 45° polarization can be used.

[0460] In addition, let the number of transmitting antennas N be t ≧3. For example, let the Doppler multiplexing number N DM ≧2, code multiplexing number N CM≧2. For example, Nt < N DM ×N CM . In addition, the number of transmission antennas with PLq polarization is denoted as "N PLq ". Here, the number of PLq polarization antennas N PLq ≧1, N PL1 +N PL2 +...+N PL_NPL =N t , q = 1 to NPL. For example, the transmission antennas include N PL1 PL1 polarization antennas and N PL2 PL2 polarization antennas, N PL1 +N PL2 <Nt). In addition, the Doppler multiplexing number assigned to the transmission antennas with PLq polarization is denoted as "N DM_PLq ". Here, N DM_PLq ≦N DM .

[0461] The radar device 10 performs CDDM transmission using, for example, Nt transmission antennas.

[0462] In addition, the radar device 10 performs CDDM transmission that satisfies the following condition 1a and condition 2a for Nt transmission antennas including transmission antennas with PL1 polarization and PL2 polarization that are cross-polarized with each other and transmission antennas with a polarization different from PL1 polarization and PL2 polarization, and performs simultaneous multiplexing transmission from the Nt transmission antennas.

[0463] Condition 1a and condition 2a are, for example, conditions in the case of using transmission antennas with a polarization different from PL1 polarization and PL2 polarization in addition to the two polarizations of PL1 polarization and PL2 polarization that are in an orthogonally polarized relationship with each other. For example, in the case where there are no other transmission antennas with different polarizations other than the transmission antennas with PL1 polarization and PL2 polarization that are in an orthogonally polarized relationship with each other, condition 1a and condition 2a become conditions equivalent to condition 1 and condition 2.

[0464] For example, since the reflected waves corresponding to the radar transmission signals respectively transmitted from the transmission antennas with PL1 polarization and PL2 polarization that are in an orthogonally polarized relationship with each other become cross-polarized with respect to the receiving antenna unit 202, there may be a situation where the received levels of the received signals are very different. On the other hand, among the Nt transmission antennas, the transmission antennas with a polarization different from PL1 polarization and PL2 polarization antennas do not form an orthogonally polarized relationship with PL1 polarization and PL2 polarization. Therefore, the received level of the received signal corresponding to the radar transmission signal from the transmission antenna with a different polarization is not likely to be significantly different from the received levels of the received signals corresponding to the transmission antennas with PL1 polarization and PL2 polarization.

[0465] Therefore, for example, in condition 1a, instead of the "transmitting antenna of PL1 polarization" in condition 1, it is possible to use "a transmitting antenna of polarization other than PL2 polarization (for example, (Nt-Nt)". PL2 Similarly, in condition 1a, instead of "transmitting antennas with PL2 polarization" in condition 1, "transmitting antennas with polarization other than PL1 polarization (for example, (Nt-N PL1 ) transmitting antennas)” condition.

[0466] For example, in condition 2a, instead of "the same polarized transmission antenna" in condition 2, the condition of "one of the polarized transmission antennas other than the PL2 polarized antenna and the polarized transmission antenna other than the PL1 polarized antenna" may be applied.

[0467] For example, Condition 1a and Condition 2a may be defined as follows.

[0468] <Condition 1a>

[0469] The phase rotation amount setting unit 105 sets a CDP amount ψ that satisfies a different DDM mode (e.g., a Doppler frequency shift amount allocation mode), a different CDM mode (e.g., a different code multiplexing number between DDM signals), or a different Doppler multiplexing and code multiplexing mode condition for each of the polarized transmission antennas other than the PL2 polarization and the polarized transmission antennas other than the PL1 polarization. ndc(ndm)，ndm (m).

[0470] <Condition 2a>

[0471] The signals transmitted from the polarized transmission antennas other than the PL2 polarized antenna and the polarized transmission antennas other than the PL1 polarized antenna are multiplexed and transmitted respectively with the code multiplexing number that is not uniform between the DDM signals, wherein the code multiplexing number may be greater than 1 and N CM A code multiplexing number within the range below -1.

[0472] The radar device 10 can obtain the following effects by providing the CDP amount to the transmission antenna so as to satisfy the above-mentioned condition 1a.

[0473] For example, in addition to the Doppler phase rotation of the code during transmission as described above, the Doppler frequency of the unknown target is added to the Doppler frequency of the received signal. Therefore, while the intervals between the DDM signals are maintained, their Doppler frequencies may change in the positive direction or the negative direction. For example, by satisfying 1A of condition 1a (for example, at least one of A-1, A-2, and A-3), when the CDDM signal assigned to the transmitting antenna of PL1 polarization is not received and when the CDDM signal assigned to the transmitting antenna of PL2 polarization is not received, the interval or Doppler multiplexing number of the DDM signal is different, and the radar device 10 can distinguish these.

[0474] In addition, for example, by satisfying 1B of condition 1a (for example, at least one of B-1 and B-2), when a CDDM signal assigned to a transmitting antenna with PL1 polarization is not received, and when a CDDM signal assigned to a transmitting antenna with PL2 polarization is not received, after decode multiplexing each DDM signal, the code interval or code multiplexing number with a high reception level is different, and the radar device 10 is able to distinguish these.

[0475] Therefore, by making the setting of the CDP amount performed by the phase rotation amount setting unit 105 satisfy condition 1a, even if the reception levels between the reception signals corresponding to the transmitting antennas with different polarizations are greatly different, the radar device 10 can demultiplex the CDDM signals in this case, thereby suppressing the degradation of the positioning performance and the radar detection performance.

[0476] In addition, by making the setting of the CDP amount performed by the phase rotation amount setting unit 105 satisfy condition 2a in addition to condition 1a, the detectable Doppler frequency range in the radar device 10 becomes the range of -1 / (2Tr)≦fd<1 / (2Tr), which can be expanded to a range equivalent to the Doppler detection range when using a single transmitting antenna.

[0477] Hereinafter, an example of setting the CDP amount in the phase rotation amount setting unit 105 will be described.

[0478] <Setting Example 5>

[0479] Fig.16 Indicates the number of transmitting antennas Nt = 6, N PL1 =2,N PL2 =2,N PL3 An example of setting the CDP amount in the phase rotation amount setting unit 105 when φ=3.

[0480] exist Fig.16In the figure, the black circles represent the distribution of CDDM signals of the transmitting antennas (Tx#1 and Tx#2) of PL1 polarization, the white circles represent the distribution of CDDM signals of the transmitting antennas (Tx#3 and Tx#4) of PL2 polarization, and the shaded circles represent the distribution of CDDM signals of the transmitting antennas (Tx#5 and Tx#6) of PL3 polarization (for example, vertical (V) polarization). For example, it is assumed that PL1 polarization and PL2 polarization are polarizations that are orthogonal to each other. For example, PL1 polarization may be LC polarization and PL2 polarization may be RC polarization. In addition, PL3 polarization may be a polarization that is not orthogonal to PL1 polarization and PL2 polarization (for example, vertical (V) polarization).

[0481] In addition, Fig.16 In the Doppler multiplexing number N DM =4, the Doppler shift setting unit 106 can set the four values ​​DOP1 to DOP4 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig.16 In the example, the phase rotation amount DOP1=0 is given. The phase rotation amount given DOP2 = Δfd The phase rotation amount given DOP3 = -2Δfd The phase rotation amount given to DOP4 = -Δfd ( Also available). Fig.16 As shown, the interval between DDM signals (also called "Doppler multiplexing interval", "Doppler frequency shift interval" or "Doppler interval") Δfd is equally spaced, Δfd=1 / (8Tr).

[0482] In addition, Fig.16 In the code multiplexing number N CM =2, the encoding unit 107 uses, for example, Code1={1, 1} and Code2={1, -1} of an orthogonal code sequence with a code length Loc=2.

[0483] exist Fig.16 In the example, the number of transmitting antennas Nt = 6, the number of Doppler multiplexing N DM =4, code multiplexing number N CM =2, Nt <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the DDM signal unevenly. CDDM (ndm) (here, ndm = 1 to N DM ).

[0484] like Fig.16As shown, in the coding unit 107, the coding Doppler multiplexing numbers for the DDM signals using the four signals DOP1 to DOP4 input from the Doppler shift setting unit 106 are N and N, respectively. CDDM (1) = 2, N CDDM (2) = 1, N CDDM (3) = 2, N CDDM (4)=1. In this way, the phase rotation amount setting unit 105 sets the code-Doppler multiplexing number for the DDM signal unevenly.

[0485] In addition, Fig.16 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1 and Tx#2 of PL1 polarization. DM =4 DDM signal using Doppler shift amounts DOP2 and DOP3 (N DM_PL1 =2), for example, the Doppler multiplexing number N is allocated to Tx#3 and Tx#4 of PL2 polarization. DM =4 DDM signal using Doppler shift amounts DOP3 and DOP4 (N DM_PL2 =2), and, for example, the Doppler multiplexing number N is allocated to Tx#5 and Tx#6 of PL3 polarization. DM =4 DDM signal using Doppler shift amount DOP1 (N DM_PL2 =1).

[0486] For example, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#1 and Tx#2 of PL1 polarization. 2，2 (m), ψ 1，3 (m), set the CDP value ψ for Tx#3 and Tx#4 of PL2 polarization respectively 2，3 (m), ψ 2，4 (m), set the CDP value ψ for Tx#5 and Tx#6 of PL3 polarization respectively 1，1 (m), ψ 2，1 (m).

[0487] For example, in Fig.16 In the figure, for the transmitting antennas other than the transmitting antenna with PL2 polarization (the transmitting antennas with PL1 polarization and PL3 polarization), the Doppler multiplexing number allocated by the Doppler frequency shift setting unit 106 is 3, and for the transmitting antennas other than the transmitting antenna with PL1 polarization (the transmitting antennas with PL2 polarization and PL3 polarization), the Doppler multiplexing number allocated by the Doppler frequency shift setting unit 106 is 3, which is the same.

[0488] In addition, the Doppler frequency shift intervals of the DDM signals allocated to the transmitting antennas other than the transmitting antennas with PL2 polarization are Δfd(1,2)=Δfd, Δfd(2,3)=Δfd, Δfd(3,1)=2Δfd, and the Doppler frequency shift intervals of the DDM signals allocated to the transmitting antennas other than the transmitting antennas with PL1 polarization are Δfd(1,3)=2Δfd, Δfd(3,4)=Δfd, Δfd(4,1)=Δfd. The two are cyclically consistent and identical, and therefore do not meet the different DDM mode conditions of 1A of condition 1a.

[0489] In addition, the code index assigned to the transmission antennas other than the transmission antenna of PL2 polarization (transmission antennas of PL1 polarization and PL3 polarization) for each of DOP1 to DOP4 is expressed as "CiNoPL2". Fig.16 In this case, CiNoPL2 = (2, 1, 1, *) In addition, the code index assigned to the transmission antennas other than the transmission antenna of PL1 polarization (transmission antennas of PL2 polarization and PL3 polarization) for DOP1 to DOP4 is expressed as "CiNoPL1". Fig.16 The case is that CiNoPL1 = (2, *, 1, 1).

[0490] In addition, the code multiplexing number allocated to the transmission antennas other than the transmission antenna of PL2 polarization (transmission antennas of PL1 polarization and PL3 polarization) for each of DOP1 to DOP4 is expressed as "NcNoPL2". Fig.16 In this case, NcNoPL2 = (2, 1, 1, 0) Further, the code multiplexing number allocated to the transmission antennas other than the transmission antenna of PL1 polarization (transmission antennas of PL2 polarization and PL3 polarization) for each of DOP1 to DOP4 is expressed as "NcNoPL1". Fig.16 The case is that NcNoPL1 = (2, 0, 1, 1).

[0491] In this way, for the transmitting antennas other than the transmitting antennas with PL2 polarization and the transmitting antennas other than the transmitting antennas with PL1 polarization, the code indexes assigned to each DDM signal are CiNoPL2 = (2, 1, 1, *) and CiNoPL1 = (2, *, 1, 1), which are cyclically inconsistent and have different code index intervals, and therefore satisfy B-1 of condition 1a.

[0492] In addition, in this way, for the transmitting antennas other than the transmitting antennas with PL2 polarization and the transmitting antennas other than the transmitting antennas with PL1 polarization, the code multiplexing numbers allocated to each DDM signal are NcNoPL2 = (2, 1, 1, 0) and NcNoPL1 = (2, 0, 1, 1), which are cyclically inconsistent and therefore satisfy B-2 of condition 1a.

[0493] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210. The code index at this time is CiNoPL2 alias =(1,2,2,*),CiNoPL1 alias =(1, *, 2, 2), are different (circular inconsistency). Therefore, in Fig.16 In the example, when the Doppler frequency of the target is -1 / (2Tr) ≤ f dtg In the range of <-1 / (2Tr), the code index is cyclically inconsistent and the code intervals are different.

[0494] Therefore, 1B that meets condition 1a meets the conditions of different CDM modes.

[0495] therefore, Fig.16 The setting of the CDP amount shown is an example of a setting that satisfies the condition 1a.

[0496] In addition, Fig.16 In the example, the code multiplexing number assigned to each DDM signal in the transmitting antennas other than the transmitting antennas of PL2 polarization is NcNoPL2=(2, 1, 1, 0), and the code multiplexing number assigned to each DDM signal in the transmitting antennas other than the transmitting antennas of PL1 polarization is NcNoPL1=(2, 0, 1, 1), both of which are multiplexed and transmitted with uneven code multiplexing numbers between DDM signals, and the code multiplexing number is included in 1 or more and N CM In the range below -1.

[0497] Therefore, in Fig.16 In the example, both the signals transmitted from the transmitting antennas other than the transmitting antennas with PL2 polarization and the signals transmitted from the transmitting antennas other than the transmitting antennas with PL1 polarization are multiplexed and transmitted with a code multiplexing number that is not uniform between the DDM signals, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig.16 The setting of the CDP amount shown is an example of a setting that satisfies the condition 2a.

[0498] By setting the CDP amount as shown in 16, when the reflected wave of the target object with cross polarization relative to the polarization of the receiving antenna is not included, the radar device 10 receives the received signals corresponding to the transmission antennas (Tx#1 and Tx#2) with PL1 polarization, the transmission antennas (Tx#3 and Tx#4) with PL2 polarization, and the transmission antennas (Tx#5 and Tx#6) with PL3 polarization at approximately the same level or in the range of several dB to 6 dB. Fig.16In the example, for signals transmitted from Nt (=6) Tx#1 to Tx#6 consisting of PL1 polarized transmitting antennas, PL2 polarized transmitting antennas, and PL3 polarized transmitting antennas, CDDM transmission is performed using a non-uniform CDP amount for the coded Doppler multiplexing number of each DDM signal.

[0499] Therefore, the radar device 10 can demultiplex the CDDM signal based on the existing demultiplexing operation of the CDDM signal.

[0500] In addition, for example, in Fig.16 Under the setting of the CDP amount shown in FIG. 1 , in the case of a target reflected wave with cross polarization relative to the receiving antenna, Fig.17 When the reflected wave of the target object includes the PL2 polarization as cross polarization as in (a) and Fig.17 When the target reflected wave whose PL1 polarization is cross-polarized is included as in (b), the radar device 10 receives CDDM signals different from each other (for example, CDDM signals 1B satisfying condition 1a).

[0501] As described above, in the case of a target reflected wave including a cross-polarization with respect to the polarization of the receiving antenna, Fig.17 When the reception level of the received signal corresponding to the transmission antenna of PL2 polarization decreases as in (a) of FIG. 1 (for example, it corresponds to the case where the reflected wave corresponding to the transmission antenna other than the transmission antenna of PL2 polarization is received) and when Fig.17 When the reception level of the reception signal corresponding to the transmitting antenna with PL1 polarization is reduced as in (b) (for example, equivalent to the case where a reflected wave corresponding to a transmitting antenna other than the transmitting antenna with PL1 polarization is received), the radar device 10 receives reflected wave signals having Doppler frequency components having different patterns.

[0502] Therefore, the radar device 10 can, for example, determine in the coded Doppler multiplexing and demultiplexing unit 212 described later whether a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the PL1 polarization (for example, LC polarization) or a reduction in the reception level of the reception signal of the transmitting antenna corresponding to the PL2 polarization (for example, RC polarization) has occurred based on the peak value of the Doppler frequency detected after code demultiplexing.

[0503] For example, a DDM signal with polarization other than PL2 is transmitted at N DM The uneven code multiplexing numbers among the DDM signals are multiplexed and transmitted (the code multiplexing number is included in 1 or more and N CM -1 or less).

[0504] Therefore, for example, when the coded Doppler multiplexing and demultiplexing unit 212 determines that the received signal corresponds to a transmitted signal transmitted by a polarized transmitting antenna other than a PL2 polarized transmitting antenna, the radar device 10 can use the existing CDDM signal demultiplexing operation to demultiplex the CDDM signal.

[0505] Likewise, for example, a DDM signal of a polarization other than PL1 polarization is transmitted at N DM The uneven code multiplexing numbers among the DDM signals are multiplexed and transmitted (the code multiplexing number is included in 1 or more and N CM -1 or less).

[0506] Therefore, for example, when the coded Doppler multiplexing and demultiplexing unit 212 determines that the received signal is a received signal corresponding to a transmitted signal transmitted by a polarized transmitting antenna other than a transmitting antenna polarized with PL1, the radar device 10 can use the existing demultiplexing operation of the CDDM signal to demultiplex the CDDM signal.

[0507] By operating the code-Doppler multiplexing and demultiplexing unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output corresponding to the transmission antenna for each DDM signal.

[0508] In the above, an example of setting the CDP amount in the phase rotation amount setting unit 105 has been described.

[0509] [Operation Example of the Coded Doppler Multiplexing and Demultiplexing Unit 212]

[0510] For example, when a transmitting antenna having a polarization other than PL1 polarization and PL2 polarization (for example, PL3 polarization) is used in addition to the two polarizations of PL1 polarization and PL2 polarization which are orthogonal to each other, the DDM signal to which the CDP amount set in the above-mentioned phase rotation amount setting unit 105 is given can be demultiplexed by the following operation of the coded Doppler multiplexing and demultiplexing unit 212. The operation of the coded Doppler multiplexing and demultiplexing unit 212 of the second modification example which is different from the above-mentioned embodiment will be described below.

[0511] In Modification 2, regarding Fig.14 The operation of step B and the operation of step C in the demultiplexing operation of the CDDM signal by the code-Doppler multiplexing and demultiplexing unit 212 shown are different from the operations of the above-described embodiment in the following points.

[0512] <Step B-1>

[0513] exist Fig.14In the demultiplexing operation of the CDDM signal of the coded Doppler multiplexing demultiplexing unit 212 shown in FIG. PL1 CDDM demultiplexing processing of PL1 polarization, in variant 2, for (Nt-N PL2 The two devices differ in that the DDM signals of the polarization transmitting antennas other than the PL2 polarization are subjected to CDDM demultiplexing processing. Other than this, the operations are the same, so the description of the operations is omitted.

[0514] <Step B-2>

[0515] The coded Doppler multiplexing and demultiplexing unit 212 determines whether (Nt-Nt) assigned to the transmission antennas other than the PL2 polarization is detected normally. PL2 ) transmitting antennas (Nt-N PL2 ) CDDM signals. The coded Doppler multiplexing and demultiplexing unit 212 is (Nt-N PL2 ) When the CDDM signal is detected normally, the process of step B-3 is performed, and when it is not detected normally, the process of step C-1 is performed.

[0516] For example, in the process of step B-1, if there is no target reflected wave whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna, (Nt-N PL2 ) CDDM signals.

[0517] For example, in the case where the extracted power ranks first, DM_NotPL2 DDM signal and other power ranked later (N DM -N DM_NotPL2 ) When the power difference (or power ratio) between the two DDM signals does not reach a specified level or above, the coded Doppler multiplexing and demultiplexing unit 212 determines that the reflected wave of the target object whose PL2 polarization is cross-polarized relative to the polarization of the receiving antenna is not included, and performs processing in step C-1.

[0518] When the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (A-2) of the condition 1a, the code-Doppler multiplexing / demultiplexing unit 212 can perform such a determination process.

[0519] Here, N DM_NotPL2 is the number of DDM signals to which CDDM signals are assigned to transmit antennas other than the transmit antennas of PL2 polarization. DM_NotPL2 The transmission antennas other than the PL2 polarization transmission antennas are assigned to N DM The number of DDM signals with a code multiplexing number of 1 or more. Fig.16 In the setting example, NcNoPL2=(2,1,1,0), NDM_NotPL2 =3.

[0520] In addition, the N with the most extracted power DM_NotPL2 When the Doppler multiplexing interval of the DDM signal does not match the Doppler multiplexing interval assigned to the polarization transmitting antenna other than PL2 polarization, the coded Doppler demultiplexing unit 212 determines that the target object reflected wave whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna is not included, and performs the processing of step C-1.

[0521] When the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (A-1) or (A-3) of the condition 1a, the code-Doppler multiplexing / demultiplexing unit 212 can perform such a determination process.

[0522] In addition, for example, it is assumed that for the transmission antennas other than the PL2 polarization (Nt-N PL2 ) transmitting antennas, the phase rotation amount setting unit 105 is set to N DM_NotPL1 =N DM_NotPL2 At this time, in the case of a target reflected wave including PL1 polarization that is cross-polarized with respect to the polarization of the receiving antenna, N DM The Doppler frequency index (f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cf , f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) is within the specified range. In this case, when the code demultiplexing process is performed, the received power obtained is the same as the assumed N DM_NotPL2 The code intervals or code multiplexing numbers of the CDDM signals are different. Therefore, the aliasing determination of the code Doppler multiplexing demultiplexing unit 212 fails, and it is difficult to normally detect N DM_NotPL2 In this case, the coded Doppler multiplexing and demultiplexing unit 212 determines that it is not for N DM_NotPL2 The normal detection of a CDDM signal is performed and the processing of step C-1 is performed.

[0523] When the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (B-1) or (B-2) of the condition 1a, the code-Doppler multiplexing / demultiplexing unit 212 can perform such a determination process.

[0524] <Step B-3>

[0525] The coded Doppler multiplexing demultiplexing unit 212 performs the processing result of step B-2 on the transmission antennas other than the PL2 polarization (Nt-NPL2 ) receiving signal YPL1 after CDDM demultiplexing of the CDDM signal used in the multiplexed transmission of the transmitting antennas z (f b_cf , f sc_cf , ncm, ndm) and f b_cf and f sc_cf The two signals are outputted together to the direction estimation unit 213 .

[0526] Here, YPL1 z (f b_cf , f sc_cf , ndc(ndm), ndm) is the f of the Doppler analysis unit 210 of the z-th antenna system processing unit 201 b_cf and f sc_cf The lieutenant general used DOP ndm and orthogonal code Code ndc(ndm) The output of the CDDM signal after demultiplexing (e.g., CDDM demultiplexing result). For example, YPL1 z (f b_cf , f sc_cf , ndc(ndm), ndm) represents the number of antennas other than the PL2 polarization transmitting antenna (Nt-N PL2 ) Tx#[ndc(ndm), ndm] sends the received signal and reflects at the target object, thereby receiving the received signal at the zth antenna system processing unit 201.

[0527] Here, z = 1 to Na, ndm = 1 to N DM , ndc(ndm)=1~N CDDM (ndm), except for N assigned to the PL2 polarization PL2 Except for the signal from the transmitting antenna, the output is zero.

[0528] <Step C-1>

[0529] The coded Doppler multiplexing and demultiplexing unit 212 assumes that the reflected wave of the target object including the PL1 polarization is cross-polarized with the polarization of the receiving antenna, and performs (Nt-Nt) demultiplexing on the signals other than the PL1 polarization. PL1 ) CDDM demultiplexing processing of the CDDM signals of the polarized transmitting antennas.

[0530] exist Fig.14 In the demultiplexing operation of the CDDM signal of the coded Doppler multiplexing demultiplexing unit 212 shown in FIG. PL2 CDDM demultiplexing processing of PL2 polarization, in variant 2, for (Nt-N PL1The two devices differ in that the DDM signals of the polarization transmitting antennas other than the PL2 polarization are subjected to CDDM demultiplexing processing. Other than this, the operations are the same, so the description of the operations is omitted.

[0531] <Step C-2>

[0532] The coded Doppler multiplexing and demultiplexing unit 212 determines whether (Nt-Nt) assigned to the transmission antennas other than the PL1 polarization is detected normally. PL1 ) transmitting antennas (Nt-N PL1 ) CDDM signals. The coded Doppler multiplexing and demultiplexing unit 212 is (Nt-N PL1 ) When the CDDM signal is detected normally, step C-3 is performed. When it is not detected normally, it is regarded as a signal with a large noise component (for example, low SNR) or containing an interference component, and step D is performed.

[0533] For example, in the case where the extracted power ranks first, DM_NotPL1 DDM signal and other power ranked later (N DM -N DM_NotPL1 ) When the power difference (or power ratio) between the two DDM signals does not reach a specified level or above, the coded Doppler multiplexing and demultiplexing unit 212 determines that the target reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is not included, and performs processing in step D.

[0534] Here, N DM_NotPL1 is the number of DDM signals to which CDDM signals are assigned to transmit antennas other than the transmit antennas polarized at PL1. DM_NotPL1 The transmission antennas other than the PL1 polarization transmission antennas are assigned to N DM The number of DDM signals with a code multiplexing number of 1 or more. Fig.16 In the setting example, NcNoPL1=(2,0,1,1), N DM_NotPL1 =3.

[0535] In addition, the N with the most extracted power DM_NotPL1 When the Doppler multiplexing interval of the DDM signal does not match the Doppler multiplexing interval assigned to the polarization transmitting antenna other than PL1 polarization, the coded Doppler demultiplexing unit 212 determines that the target object reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is not included, and performs the processing of step D.

[0536] In addition, the coded Doppler multiplexing and demultiplexing unit 212 extracts, for example, N of the top power. DM_NotPL1DDM signal, according to the received power of the signal obtained by implementing the code demultiplexing process, determines the difference with the assumed (Nt-N PL1 If they are not consistent, the coded Doppler multiplexing and demultiplexing unit 212 determines that the target reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is not included, and performs the processing of step D.

[0537] <Step C-3>

[0538] The coded Doppler multiplexing and demultiplexing unit 212 performs the processing result of step C-2 on the transmission antennas other than the PL1 polarization (Nt-N PL1 ) receiving signal YPL2 after CDDM demultiplexing of the CDDM signal used in the multiplexed transmission of the transmitting antennas z (f b_cf , f sc_cf , ncm, ndm) and f b_cf and f sc_cf The two signals are outputted together to the direction estimation unit 213 .

[0539] Here, YPL2 z (f b_cf , f sc_cf , ndc(ndm), ndm) is the f of the Doppler analysis unit 210 of the z-th antenna system processing unit 201 b_cf and f sc_cf The lieutenant general used DOP ndm and orthogonal code Code ndc(ndm) The output of the CDDM signal after demultiplexing (e.g., CDDM demultiplexing result). For example, YPL2 z (f b_cf , f sc_cf , ndc(ndm), ndm) represents the number of transmitting antennas other than PL1 polarization (Nt-N PL1 ) Tx#[ndc(ndm), ndm] sends the received signal and reflects at the target object, thereby receiving the received signal at the zth antenna system processing unit 201.

[0540] Here, z = 1 to Na, ndm = 1 to N DM , ndc(ndm)=1~N CDDM (ndm), except for N assigned to PL1 polarization PL1 Except for the signal from the transmitting antenna, the output is zero.

[0541] Furthermore, the code-Doppler multiplexing and demultiplexing unit 212 may output the detected Doppler frequency of the target object to the direction estimating unit 213 .

[0542] Furthermore, when condition 2a is satisfied, the code-Doppler multiplexing / demultiplexing unit 212 can detect the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0543] In the above, an operation example of the code-Doppler multiplexing and demultiplexing unit 212 has been described.

[0544] [Operation Example of Direction Estimation Unit 213]

[0545] As in the above-described embodiment, the direction estimation unit 213 may perform direction estimation processing based on the output corresponding to the demultiplexing operation of the coded Doppler multiplexing and demultiplexing unit 212 .

[0546] For example, the direction estimation unit 213 can perform direction estimation processing based on the output of the coded Doppler multiplexing and demultiplexing unit 212 corresponding to the following situations, namely, a situation that does not include a target reflection wave with a cross-polarization relative to the polarization of the receiving antenna, a situation that includes a target reflection wave with a PL2 polarization that is cross-polarized relative to the polarization of the receiving antenna, and a situation that includes a target reflection wave with a PL1 polarization that is cross-polarized relative to the polarization of the receiving antenna.

[0547] By the operation of the direction estimation unit 213, the direction estimation result for a part of the transmission polarization is obtained according to the direction estimation processing result of each transmission polarization or the state of the reflected wave, and the direction estimation result depending on the transmission polarization is obtained. Since the reflected wave response from the target object may change according to the transmission polarization, based on such a direction estimation result depending on the transmission polarization, the radar device 10 can improve the detection performance or recognition performance of the target object.

[0548] Modification Example 2 has been described above.

[0549] In the above, each embodiment of the present disclosure has been described.

[0550] [Other embodiments]

[0551] (1) In the above embodiment, in order to expand the detectable Doppler frequency range for Nt transmitting antennas including transmitting antennas with different polarizations to the range of ±1 / (2Tr), it is assumed that the code multiplexing number between DDM signals is set unevenly and CDDM transmission is performed from multiple transmitting antennas. In the above embodiment, a method for improving the detection performance of the polarization MIMO radar by applying CDDM transmission that satisfies conditions 1 and 2 is further described. For example, when the moving speed of the assumed target object is a relatively low speed, or when the relative speed between the radar device and the target object is limited to a relatively small range, the above premise may not be applied.

[0552] For example, the coding unit 107 may use an evenly spaced Doppler frequency shift setting with a smaller interval than the maximum evenly spaced Doppler frequency shift setting interval (for example, equation (6)) to set the coded Doppler multiplexing number N to CDDM (1), N CDDM (2), ..., N CDDM (N DM ) is set to be included in 1 or more and N CM For example, the coding unit 107 may set the code number N to be the same in all settings of the code Doppler multiplexing number. CM Therefore, it can be that in DOP ndm In multiple combinations of orthogonal code sequences, about each DOP ndm The orthogonal code sequences corresponding to each other are based on the multiplexing number (coded Doppler multiplexing number) N of these orthogonal code sequences. CDDM (ndm) are the same. For example, the coding unit 107 can uniformly set the coded Doppler multiplexing number for the DDM signal. By setting it in this way, when the DDM signal is non-uniformly spaced Doppler multiplexed, for example, the aliasing judgment in patent document 8 can be applied, and the radar device 10 can demultiplex the signals sent by CDDM from multiple transmitting antennas into separate signals and receive them over the Doppler range of ±1 / (2×Loc×Tr). By applying such a setting for CDDM transmission, and then applying CDDM transmission that satisfies condition 1, the effect based on condition 1 described in embodiment 1 can be obtained, and the detection performance of the polarization MIMO radar can be improved.

[0553] Alternatively, the coding unit 107 may use, for example, the maximum equally spaced Doppler frequency shift setting to set the coded Doppler multiplexing number N to CDDM (1), N CDDM (2), ..., N CDDM (N DM ) is set to be included in 1 or more and N CMFor example, the coding unit 107 may set the code number N to be the same in all settings of the code Doppler multiplexing number. CM In this case, DOP ndm The number of combinations of orthogonal code sequences and the number of transmitting antennas Nt may be the same (for example, N DM ×N CM =Nt). For example, the coding unit 107 may uniformly set the coded Doppler multiplexing number for the DDM signal. When this setting is adopted, the aliasing determination process in the reception process of the radar device 10 is not applied. In addition, the radar device 10 may, for example, cover ±1 / (2Loc×N DM ×Tr), the signals sent by CDDM from multiple transmitting antennas are demultiplexed into separate signals and received. By applying such CDDm transmission settings and then applying CDDm transmission that satisfies condition 1, the effect based on condition 1 described in embodiment 1 can be obtained, and the detection performance of polarization MIMO radar can be improved.

[0554] (2) In one embodiment of the present disclosure, instead of using all Nt transmission antennas included in the radar device 10 , only a part of them may be used to perform code multiplexing transmission in one embodiment of the present disclosure.

[0555] In addition, when the code multiplexing transmission of the above embodiment is applied using only a part of the Nt transmitting antennas possessed by the radar device 10, the radar device 10 may also set (or change) at least one of the combination of transmitting antennas and the number of multiplexed transmissions for code Doppler multiplexing transmission to time division and transmit. In this case, for example, the radar device 10 may time-division switch the combination of transmitting antennas for each transmission cycle or each code transmission cycle (for example, a cycle corresponding to the code length of the code sequence). Or, for example, the radar device 10 may switch the combination of transmitting antennas or the number of multiplexed transmitting antennas for each measurement cycle (every Nc radar transmission signal transmissions). Even if such an action is applied, the same effect as the above embodiment can be obtained.

[0556] In addition, when the code multiplexing transmission of the above embodiment is applied by using only a part of the Nt transmission antennas provided by the radar device 10 instead of all of them, the radar device 10 may set (e.g., change) the combination of transmission antennas used for code Doppler multiplexing transmission in a time division manner and use different chirp signals for transmission. For example, the radar device 10 may change at least one of the transmission frequency band, frequency scanning time, and center frequency of the chirp signal, or combine a plurality of these parameters and use different chirp signals for transmission.

[0557] (3) In the radar device of one embodiment of the present disclosure, the radar transmitter and the radar receiver may be respectively arranged at physically separate locations. In addition, in the radar receiver of one embodiment of the present disclosure, the direction estimation unit and other components may also be independently arranged at physically separate locations.

[0558] (4) The number of transmitting antennas Nt, the number of receiving antennas Na, and the number of Doppler multiplexing N used in one embodiment of the present disclosure DM , the number of transmitting antennas N for PLq polarization PLq , polarization number, Doppler frequency shift, Doppler frequency shift interval, code multiplexing number N CM , code interval (code index) and other parameters are examples and are not limited to these values. In addition, for example, a part of the transmitting antennas of the radar device can be used as the number of transmitting antennas Nt, and a part of the receiving antennas of the radar device can be used as the number of receiving antennas Na.

[0559] Although not shown in the figure, the radar device of one embodiment of the present disclosure has, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, and a working memory such as a RAM (Random Access Memory). In this case, the functions of the above-mentioned parts are realized by the CPU executing the control program. However, the hardware structure of the radar device is not limited to this example. For example, each functional part of the radar device can also be realized as an integrated circuit, that is, an IC (Integrated Circuit). Each functional part can be independently monolithic or monolithic in a manner that includes part or all of it.

[0560] Various embodiments have been described above with reference to the accompanying drawings, but the present disclosure is of course not limited to these examples. As long as one is skilled in the art, it is obvious that various variations or modifications can be thought of within the scope described in the claims, and it should be understood that these variations or modifications also belong to the technical scope of the present disclosure. In addition, the constituent elements of the above-mentioned embodiments can be arbitrarily combined within the scope of the disclosure purpose.

[0561] In addition, the expression "part" in the above-mentioned embodiments can also be replaced by other expressions such as "...circuitry", "...component (assembly)", "device (device)", "unit (unit)" or "module (module)".

[0562] In the above-mentioned embodiments, an example in which the present disclosure is configured using hardware has been described. However, the present disclosure may also be implemented by software in cooperation with hardware.

[0563] In addition, each functional block used in the description of the above-mentioned embodiments is typically implemented as an integrated circuit, i.e., LSI (Large Scale Integration). The integrated circuit can also control each functional block used in the description of the above-mentioned embodiments, and includes input terminals and output terminals. These functional blocks can be independently monolithic, or can be monolithic in a manner that includes a part or all. It is referred to as "LSI" here, but it can also be referred to as "IC", "system LSI (system LSI)", "super LSI (super LSI)", "ultra-large LSI (ulira LSI)" depending on the degree of integration.

[0564] In addition, the method of integrated circuitization is not limited to LSI, and it can also be realized using a dedicated circuit or a general-purpose processor. It is also possible to use an FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connection or setting of the circuit blocks inside the LSI.

[0565] Furthermore, if integrated circuit technology that replaces LSI emerges as semiconductor technology advances or other derived technologies emerge, it is of course possible to use this technology to integrate functional blocks. There is also the possibility of applying biotechnology, etc.

[0566] <Summary of the present disclosure>

[0567] A radar device according to an embodiment of the present disclosure includes: a plurality of transmitting antennas, including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmitting signals to which a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and a code sequence is assigned, wherein for each of the plurality of transmitting antennas, there corresponds a different combination of at least one of the Doppler frequency shift amount and the code sequence, and a first pattern of the Doppler frequency shift amount and the code sequence assigned to the first transmitting antenna is different from a second pattern of the Doppler frequency shift amount and the code sequence assigned to the second transmitting antenna.

[0568] In one embodiment of the present disclosure, the number of the plurality of transmitting antennas is less than the total number of the combinations.

[0569] In one embodiment of the present disclosure, the first mode and the second mode are related to the interval of Doppler frequency shift amount, the Doppler multiplexing number of the transmission signal sent by the first transmitting antenna is the same as the Doppler multiplexing number of the transmission signal sent by the second transmitting antenna, and at least one of the intervals of Doppler frequency shift amount corresponding to the first transmitting antenna is different from the intervals of Doppler frequency shift amount corresponding to the second transmitting antenna.

[0570] In one embodiment of the present disclosure, the first mode and the second mode are related to a Doppler multiplexing number, and the Doppler multiplexing number of the transmission signal sent by the first transmission antenna is different from the Doppler multiplexing number of the transmission signal sent by the second transmission antenna.

[0571] In one embodiment of the present disclosure, the first mode and the second mode are related to the order of the intervals of the Doppler frequency shift amounts, and a plurality of first Doppler frequency shift intervals between the Doppler frequency shift amounts corresponding to the first transmitting antenna and a plurality of second Doppler frequency shift intervals between the Doppler frequency shift amounts corresponding to the second transmitting antenna are the same, and the order of the plurality of first Doppler frequency shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler frequency shift intervals on the Doppler frequency axis.

[0572] In one embodiment of the present disclosure, the first mode and the second mode are related to the code sequence, and in the multiple combinations, the order of the code sequence corresponding to the first transmitting antenna on the Doppler frequency axis is different from the order of the code sequence corresponding to the second transmitting antenna on the Doppler frequency axis.

[0573] In one embodiment of the present disclosure, the first mode and the second mode are related to the code multiplexing number based on the code sequence, and in the multiple combinations, the order of the code multiplexing number based on the code sequence corresponding to the first transmitting antenna on the Doppler frequency axis is different from the order of the code multiplexing number based on the code sequence corresponding to the second transmitting antenna on the Doppler frequency axis.

[0574] In one embodiment of the present disclosure, with respect to at least one of the first transmitting antenna and the second transmitting antenna, in the multiple combinations, at least one of the Doppler frequency shift amounts is such that a code multiplexing number based on the code sequence corresponding to the Doppler frequency shift amount is different from a code multiplexing number based on the code sequence corresponding to other Doppler frequency shift amounts.

[0575] In one embodiment of the present disclosure, it also includes: a receiving antenna, which uses one of the first polarized wave and the second polarized wave to receive a reflected wave signal reflected by the transmitted signal from the target object; and a direction estimation circuit, which estimates the direction of the target object based on the reflected wave signal.

[0576] In one embodiment of the present disclosure, the device further comprises: a plurality of receiving antennas, including a first receiving antenna for receiving the first polarized wave and a second receiving antenna for receiving the second polarized wave, for receiving a reflected wave signal of the transmitted signal reflected from the target object; and a direction estimation circuit for separately estimating the direction of the target object for the reflected wave signals received by the first receiving antenna and the second receiving antenna respectively.

[0577] In one embodiment of the present disclosure, a combination of transmitting antennas among the multiple transmitting antennas used for multiplexed transmission of the transmitting signal is switched according to each transmission period of the transmitting signal, each period corresponding to the code length of the code sequence, or each measurement period in the radar device.

[0578] In one embodiment of the present disclosure, there are: multiple transmitting antennas, including a first transmitting antenna that radiates a first polarized wave, a second transmitting antenna that radiates a second polarized wave different from the first polarized wave, and a third transmitting antenna that radiates a third polarized wave different from the first polarized wave and the second polarized wave; and a transmitting circuit that multiplexes and transmits transmission signals assigned phase rotation amounts corresponding to a combination of a Doppler frequency shift amount and a code sequence from the multiple transmitting antennas, and for each of the multiple transmitting antennas, there corresponds a different combination of at least one of the Doppler frequency shift amount and the code sequence, and a third pattern of the Doppler frequency shift amount and the code sequence assigned to the first transmitting antenna and the third transmitting antenna is different from a fourth pattern of the Doppler frequency shift amount and the code sequence assigned to the second transmitting antenna and the third transmitting antenna.

[0579] The disclosure contents of the specification, drawings and abstract contained in the Japanese patent application No. 2022-202052 filed on December 19, 2022 are all cited in this application.

[0580] Industrial Applicability

[0581] The present disclosure is suitable as a radar device that detects a wide-angle range.

[0582] Description of Reference Numerals

[0583] 10 Radar device

[0584] 100 Radar Transmitter

[0585] 101 Radar transmission signal generating unit

[0586] 102 transmission signal generation control unit

[0587] 103 Modulation signal generation unit

[0588] 104 VCO

[0589] 105 Phase rotation amount setting unit

[0590] 106 Doppler frequency shift setting unit

[0591] 107 Coding Department

[0592] 108 Phase rotation unit

[0593] 109 Transmitting antenna unit

[0594] 200, 200a Radar receiving unit

[0595] 201 Antenna System Processing Department

[0596] 202 Receiving antenna unit

[0597] 203 Receiving wireless unit

[0598] 204 Mixer Department

[0599] 205 LPF

[0600] 206 Signal Processing Department

[0601] 207 AD conversion unit

[0602] 208 Beat Frequency Analysis Department

[0603] 209 Output switching unit

[0604] 210 Doppler Analysis Department

[0605] 211, 211a CFAR Department

[0606] 212, 212a Coded Doppler multiplexing and demultiplexing unit

[0607] 213, 213a Direction estimation unit

Claims

1. A radar device, characterized in that: have: a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave; and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and a code sequence is applied, For each of the plurality of transmitting antennas, there is a different combination of at least one of the Doppler frequency shift amount and the code sequence, A first pattern of a Doppler frequency shift amount and a code sequence assigned to the first transmitting antenna is different from a second pattern of a Doppler frequency shift amount and a code sequence assigned to the second transmitting antenna.

2. The radar device according to claim 1, wherein: The number of the plurality of transmitting antennas is less than the total number of the combinations.

3. The radar device according to claim 1, wherein: The first mode and the second mode are related to the interval of the Doppler frequency shift amount, The Doppler multiplexing number of the transmission signal transmitted by the first transmission antenna is the same as the Doppler multiplexing number of the transmission signal transmitted by the second transmission antenna. At least one of the intervals of Doppler frequency shift amounts corresponding to the first transmitting antenna is different from the intervals of Doppler frequency shift amounts corresponding to the second transmitting antenna.

4. The radar device according to claim 1, wherein: The first mode and the second mode are related to the Doppler multiplexing number. The Doppler multiplexing number of the transmission signal transmitted by the first transmission antenna is different from the Doppler multiplexing number of the transmission signal transmitted by the second transmission antenna.

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

6. The radar device according to claim 1, wherein: The first mode and the second mode are related to the code sequence, In the plurality of combinations, the order of the code sequences corresponding to the first transmitting antenna on the Doppler frequency axis is different from the order of the code sequences corresponding to the second transmitting antenna on the Doppler frequency axis.

7. The radar device according to claim 1, wherein: The first mode and the second mode are related to the code multiplexing number based on the code sequence, In the plurality of combinations, the order of the code multiplexing numbers based on the code sequence corresponding to the first transmitting antenna on the Doppler frequency axis is different from the order of the code multiplexing numbers based on the code sequence corresponding to the second transmitting antenna on the Doppler frequency axis.

8. The radar device according to claim 1, wherein: With respect to at least one of the first transmitting antenna and the second transmitting antenna, in the plurality of combinations, at least one Doppler frequency shift amount is such that a code multiplexing number based on the code sequence corresponding to the Doppler frequency shift amount is different from a code multiplexing number based on the code sequence corresponding to other Doppler frequency shift amounts.

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

10. The radar device according to claim 1, wherein: Also available: A plurality of receiving antennas, including a first receiving antenna for receiving the first polarized wave and a second receiving antenna for receiving the second polarized wave, receiving a reflected wave signal of the transmitted signal reflected from a target object; as well as The direction estimation circuit estimates the direction of the target object based on the reflected wave signals received by the first receiving antenna and the second receiving antenna respectively.

11. The radar device according to claim 1, wherein: A combination of transmission antennas used for multiplexed transmission of the transmission signal among the plurality of transmission antennas is switched for each transmission cycle of the transmission signal, each cycle corresponding to the code length of the code sequence, or each measurement cycle in the radar device.

12. A radar device, characterized in that: have: a plurality of transmitting antennas, including a first transmitting antenna radiating a first polarized wave, a second transmitting antenna radiating a second polarized wave different from the first polarized wave, and a third transmitting antenna radiating a third polarized wave different from the first polarized wave and the second polarized wave; as well as a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, transmission signals to which a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and a code sequence is applied, For each of the plurality of transmitting antennas, there is a different combination of at least one of the Doppler frequency shift amount and the code sequence, A third pattern of Doppler frequency shift amounts and code sequences assigned to the first transmitting antenna and the third transmitting antenna is different from a fourth pattern of Doppler frequency shift amounts and code sequences assigned to the second transmitting antenna and the third transmitting antenna.

13. A method for transmitting a radar signal, characterized in that: The following steps are involved: giving a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and a code sequence to the radar signal; and multiplexing and transmitting the radar signals to which the phase rotation amount is applied from a plurality of transmitting antennas, The plurality of transmitting antennas include a first transmitting antenna that radiates a first polarized wave and a second transmitting antenna that radiates a second polarized wave different from the first polarized wave, For each of the plurality of transmitting antennas, there is a different combination of at least one of the Doppler frequency shift amount and the code sequence, A first pattern of a Doppler frequency shift amount and a code sequence assigned to the first transmitting antenna is different from a second pattern of a Doppler frequency shift amount and a code sequence assigned to the second transmitting antenna.

14. The method for transmitting a radar signal according to claim 13, wherein: The number of the plurality of transmitting antennas is less than the total number of the combinations.

15. The method for transmitting a radar signal according to claim 13, wherein: The first mode and the second mode are related to the interval of the Doppler frequency shift amount, The Doppler multiplexing number of the radar signal transmitted by the first transmitting antenna is the same as the Doppler multiplexing number of the radar signal transmitted by the second transmitting antenna. At least one of the intervals of Doppler frequency shift amounts corresponding to the first transmitting antenna is different from the intervals of Doppler frequency shift amounts corresponding to the second transmitting antenna.

16. The method for transmitting a radar signal according to claim 13, wherein: The first mode and the second mode are related to the Doppler multiplexing number. A Doppler multiplexing number of the radar signal transmitted by the first transmitting antenna is different from a Doppler multiplexing number of the radar signal transmitted by the second transmitting antenna.

17. The method for transmitting a radar signal according to claim 13, wherein: The first mode and the second mode are related to the order of the intervals of the Doppler frequency shift amounts. A plurality of first Doppler frequency shift intervals between the Doppler frequency shift amounts corresponding to the first transmitting antenna and a plurality of second Doppler frequency shift intervals between the Doppler frequency shift amounts corresponding to the second transmitting antenna are the same, An order of the plurality of first Doppler frequency shift intervals on the Doppler frequency axis is different from an order of the plurality of second Doppler frequency shift intervals on the Doppler frequency axis.

18. A method for transmitting a radar signal, characterized in that: The following steps are involved: giving a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and a code sequence to the radar signal; and multiplexing and transmitting the radar signals to which the phase rotation amount is applied from a plurality of transmitting antennas, The plurality of transmitting antennas include a first transmitting antenna that radiates a first polarized wave, a second transmitting antenna that radiates a second polarized wave different from the first polarized wave, and a third transmitting antenna that radiates a third polarized wave different from the first polarized wave and the second polarized wave, For each of the plurality of transmitting antennas, there is a different combination of at least one of the Doppler frequency shift amount and the code sequence, A third pattern of Doppler frequency shift amounts and code sequences assigned to the first transmitting antenna and the third transmitting antenna is different from a fourth pattern of Doppler frequency shift amounts and code sequences assigned to the second transmitting antenna and the third transmitting antenna.

19. A method for receiving a radar signal, characterized in that: The following steps are involved: Receiving, by a receiving antenna, a reflected wave signal of a radar signal transmitted by the radar signal transmitting method according to claim 13 and reflected by a target object; as well as Estimating the direction of the target object according to the reflected wave signal, The receiving antenna receives the reflected wave signal using one of the first polarized wave and the second polarized wave.

20. A method for receiving a radar signal, characterized in that: The following steps are involved: Receiving, using a receiving antenna, a reflected wave signal of a radar signal transmitted by the radar signal transmitting method according to claim 13 and reflected from an object, wherein the receiving antenna comprises a first receiving antenna for receiving the first polarized wave and a second receiving antenna for receiving the second polarized wave; as well as The direction of the target object is estimated for the reflected wave signals respectively received by the first receiving antenna and the second receiving antenna.

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