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

Abstract

To improve target detection accuracy in a radar system.SOLUTION: A radar system comprises: a plurality of transmission antennas including a first transmission antenna emitting a first polarization and a second transmission antenna emitting a second polarization different from the first polarization; and a transmission circuit for conducting multiple transmissions of a transmission signal to which a phase rotation amount corresponding to a combination of a Doppler shift amount and a code series are added, from the plurality of transmission antennas. For each of the plurality of transmission antennas, a combination in which at least one of the Doppler shift amount and the code sequence is different is associated, and a first pattern of the Doppler shift amount and the code series assigned to the first transmission antenna and a second pattern of the doppler shift amount and the code sequence assigned to the second transmission antenna are different.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] In recent years, radar devices using radar transmission signals with short wavelengths, including microwaves or millimeter waves, which can provide high resolution, have been studied. For example, radar devices have been proposed that have multiple antennas (array antennas) in the transmitter as well as the receiver, and perform beam scanning by signal processing using the transmitting and receiving array antennas (sometimes called MIMO (Multiple Input Multiple Output) radar) (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Publication No. 2019 / 0064337 [Patent Document 2] US Patent Publication No. 2020 / 0363497 [Patent Document 3] JP 2008-304417 A [Patent Document 4] Special Publication No. 2011-526371 [Patent Document 5] JP 2011-119344 A [Patent Document 6] JP 2020-204603 A [Patent Document 7] JP 2020-092247 A [Patent Document 8] JP 2020-148754 A [Non-patent literature]

[0004] [Non-Patent Document 1] J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 [Non-Patent Document 2] M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 [Non-Patent Document 3] Direction-of-arrival estimation using signal subspace modeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28 , Issue: 1 Publication Year: 1992 , Page(s): 64 - 79 Summary of the Invention [Problem to be solved by the invention]

[0005] However, a method for detecting a target in a radar device (eg, a MIMO radar) has not been fully considered.

[0006] A non-limiting embodiment of the present disclosure contributes to providing a radar device that improves the accuracy of detecting a target. [Means for solving the problem]

[0007] 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 polarization and a second transmitting antenna that radiates a second polarization different from the first polarization, and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, a transmission signal to which a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence is imparted, wherein each of the plurality of transmitting antennas is associated with the combination in which at least one of the Doppler shift amount and the code sequence is different, and a first pattern of the Doppler shift amount and the code sequence assigned to the first transmitting antenna is different from a second pattern of the Doppler shift amount and the code sequence assigned to the second transmitting antenna.

[0008] In addition, these comprehensive or specific embodiments may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0009] According to an embodiment of the present disclosure, it is possible to improve the detection accuracy of a target in a radar device.

[0010] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows an example of coded Doppler multiplexing. [Diagram 2] FIG. 1 shows an example of a received signal in coded Doppler multiplex transmission. [Diagram 3] FIG. 1 shows an example of coded Doppler multiplexing. [Figure 4]A block diagram showing a configuration example of a radar device. [Diagram 5] FIG. 1 is a diagram showing an example of a transmission signal when a chirp signal is used; [Figure 6] FIG. 1 shows an example of setting the amount of Doppler shift and the code sequence. [Figure 7] FIG. 13 is a diagram showing an example of setting the amount of coded Doppler phase rotation; [Figure 8] FIG. 1 shows an example of a received signal in coded Doppler multiplex transmission. [Figure 9] FIG. 13 is a diagram showing an example of setting the amount of coded Doppler phase rotation; [Figure 10] FIG. 1 shows an example of a received signal in coded Doppler multiplex transmission. [Figure 11] FIG. 13 is a diagram showing an example of setting the amount of coded Doppler phase rotation; [Figure 12] FIG. 1 shows an example of a received signal in coded Doppler multiplex transmission. [Figure 13] FIG. 13 is a diagram showing an example of setting the amount of coded Doppler phase rotation; [Figure 14] Flowchart showing an example of an operation for separating a coded Doppler multiplexed signal [Figure 15] Block diagram showing a configuration example of a radar receiver [Figure 16] FIG. 13 is a diagram showing an example of setting the amount of coded Doppler phase rotation; [Figure 17] FIG. 1 shows an example of a received signal in coded Doppler multiplex transmission. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [About polarimetric radar] For example, there is a technology for improving radar detection or identification performance by using an antenna that emits radio waves of different polarizations or an antenna that receives radio waves of different polarizations (see, for example, Patent Document 1 or Patent Document 2). A radar device that uses multiple polarizations is also called, for example, a "polarimetric radar."

[0013] For example, Patent Document 1 or Patent Document 2 discloses a method for detecting and identifying an object by transmitting a transmission signal from an antenna using vertical polarization or horizontal polarization and using the signal received by the antenna using vertical polarization or horizontal polarization. Patent Document 1 also discloses a method for detecting and identifying an object by transmitting a transmission signal from an antenna using left-handed circular polarization or right-handed circular polarization and using the signal received by an antenna using left-handed circular polarization or right-handed circular polarization. Note that an antenna using polarization such as linear polarization including vertical polarization or horizontal polarization, or circular polarization including left-handed circular polarization or right-handed circular polarization is also called a "polarized antenna."

[0014] Such polarimetric radars use a number of different types of polarized antennas (eg, polarized transmitting antennas or polarized receiving antennas).

[0015] In the following, attention will be focused on a multiplexing method in a MIMO radar that uses multiple different types of polarized antennas (for example, also called a "polarized MIMO radar").

[0016] For example, examples of multiplexing transmission methods for MIMO radar using multiple transmitting antennas include time division multiplexing (TDM) transmission (see, for example, Patent Documents 3 and 4) and Doppler division multiplexing (DDM) transmission (see, for example, Patent Document 5).

[0017] Time division multiplexing or Doppler multiplexing can separate reflected waves corresponding to transmission signals from multiple transmission antennas using the allocated transmission time or Doppler frequency range. On the other hand, in time division multiplexing and Doppler multiplexing, the detection range of the Doppler frequency tends to narrow as the number of transmission antennas increases. For example, in time division multiplexing and Doppler multiplexing, the detectable Doppler frequency range is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr), and the detection range of the Doppler frequency narrows in inverse proportion to the number of transmission antennas. Here, Nt is the number of transmission antennas, and Tr is the transmission period of the transmission signal.

[0018] [About coded Doppler multiplex transmission] Patent Document 6 (for example, FIG. 1 of Patent Document 6) discloses a multiplex transmission method that combines Doppler multiplexing and code multiplexing (hereinafter referred to as "Coded Doppler multiplexing" or "Coded DDM transmission (abbreviated as CDDM transmission)").

[0019] For example, Fig. 1 shows a case where a radar transmission wave (e.g., a chirp signal) is sent out every transmission period Tr. Fig. 1 shows an example of the allocation of transmission Doppler frequencies and codes when signals code-multiplexed with orthogonal codes (e.g., code#1, code#2) with a code length Loc=2 are transmitted to three transmission antennas (e.g., Tx#1 to Tx#3) using two Doppler multiplexed (DDM) signals (e.g., DOP1, DOP2). In the example of Fig. 1, the code multiplexing number N CM = 2, Doppler multiplex number N DM =2.

[0020] The phase rotation based on the code is performed, for example, by cyclically repeating the operation of imparting the chirp signal in a transmission period of the code length Loc×Tr (two transmission periods (2Tr) in FIG. 1). In this case, the phase rotation based on the DDM signal is constant in the transmission period of the code length in which the code of code length Loc is imparted (two transmission periods (2Tr) in FIG. 1). For example, the phase rotation based on the DDM signal may be imparted while being changed every 2Tr transmission period.

[0021] For example, in FIG. 1, the amounts of transmission Doppler shift to be assigned are set to DOP1=0 and DOP2=-1 / (4Tr) [Hz]. For example, since DOP1 is imparted to every m-th transmission period, a phase rotation Φ1(m)=ΔΦ1×(floor(m / Loc)+1) is imparted to the radar transmission wave (chirp signal). Also, since DOP2 is imparted to every m-th transmission period, a phase rotation Φ2(m)=ΔΦ2×(floor(m / Loc)+1) is imparted to the radar transmission wave. Here, ΔΦ1=0 and ΔΦ2=-π. The Doppler multiplex interval is Δf d=1 / (4Tr). For example, Code1=[1, 1] and Code2=[1, -1] may be used as the orthogonal code of code length 2. In FIG. 1, for example, DopCode#1=(DOP2, Code1), DopCode#2=(DOP2, Code2), and DopCode#3=(DOP1, Code1) are assigned to Tx#1 to Tx#3 as coded Doppler multiplexed signals (CDDM signals) combining Doppler multiplexed signals and codes, and are transmitted. Note that floor[x] is a function that outputs the maximum integer not exceeding the real number x.

[0022] Here, DopCode#n represents the allocation of a CDDM signal to the nth Tx#n (the amount of Doppler shift DOP ndm and Code ncm (n=1 to Nt, ndm is 1 to N DM is an integer value in the range of 1 to N CM For Nt transmit antennas, the DOP ndm and Code ncm The combination of these allocates different CDDM signals.

[0023] These simultaneously multiplexed signals are received by a radar device (e.g., a received signal processing unit). The radar device, for example, performs Doppler frequency analysis on the radar reflected wave received signals for each element of the transmitted code in an individual Doppler analysis unit (e.g., V-FFT#1, #2, ~, #Loc), and performs code demultiplexing and Doppler demultiplexing based on the output of the Doppler frequency analysis, thereby separating and receiving the multiplexed transmission signals. For example, when the code length Loc=2, the number of elements of the code is 2, and the radar device separates and receives the multiplexed transmission signals by performing code demultiplexing and Doppler demultiplexing based on the output of Doppler frequency analysis in individual Doppler analysis units (V-FFT#1, #2) for the received signals for each odd-numbered transmission signal and each even-numbered transmission signal.

[0024] Here, the radar device (for example, the Doppler analysis unit) uses a received signal with a transmission period of the code length Loc (in FIG. 1, Loc=2, so two transmission periods (2Tr)), and therefore Doppler frequencies exceeding ±1 / (2 Loc Tr) (±1 / (4Tr) in FIG. 1) are detected as aliased. Whether or not the radar reflected wave received signal contains components in the aliased frequency range can be detected by multiplexing the signals from multiple transmitting antennas with the code multiplexing number between DDM signals being non-uniform, as disclosed in Patent Document 6, for example. This enables the radar device to expand the Doppler frequency range (maximum Doppler) in which Doppler frequency can be detected without aliasing to ±1 / (2Tr), and also makes it possible to determine the transmitting antenna.

[0025] 1, for example, the code multiplexing number for Doppler shift amount DOP1 is 1, and the code multiplexing number for DOP2 is 2, and the code multiplexing numbers are set unevenly among the DDM signals. The radar device detects whether or not the radar reflected wave reception signal contains components in the aliasing frequency range based on the separated reception signals for the multiplexed signals using a CDDM signal (DopCode=(DOP1, Code2) in FIG. 1) that is a combination of an unused code that is not assigned to a transmitting antenna and a Doppler signal (hereinafter, also referred to as "aliasing judgment").

[0026] For example, (a) of FIG. 2 shows the Doppler frequency f dtg The received Doppler signals are shown when Code1 and Code2 are separated when Δf is 0. The received DDM signal separated by Code1 has a Doppler multiplexing interval Δf d The received Doppler frequency f is detected as high, and the radar device can determine that these components are the received signals of Tx#1 and Tx#3. Also, the received Doppler signal separated by Code2 contains the received Doppler frequency f d At =-1 / (4Tr), one Doppler frequency with a high reception level is detected. Note that the Doppler multiplex interval Δf dThe Doppler frequency of the Doppler frequency interval that matches the received Doppler frequency f d =0) is at the noise level.

[0027] 2(a), the radar device can determine that one Doppler frequency component with a high reception level detected in the received Doppler signal separated by Code 2 is the received signal of Tx#2. Also, the radar device can determine the Doppler frequency of the target because the deviation from the Doppler shift amount at the time of transmission for each transmitting antenna is the Doppler frequency of the target.

[0028] For example, in FIG. 2(b), the Doppler frequency f dtg The received Doppler signals are shown when separated by Code1 and Code2, respectively, in the case of =-1 / (2Tr). The received Doppler signal separated by Code2 has a Doppler multiplex interval Δf d The received levels at two Doppler frequencies with a Doppler frequency interval that matches the Doppler frequency interval Δf are detected as high, and the radar device can determine that these components are the received signals of Tx#1 and Tx#3. Also, one Doppler frequency with a high received level is detected in the received Doppler signal separated by Code1. Note that the Doppler multiple interval Δf between DOP1 and DOP2 for the detected Doppler frequency is d The Doppler frequency of the Doppler frequency interval that matches the received Doppler frequency f d =0) is at the noise level.

[0029] 2(b), the radar device can determine that one Doppler frequency component with a high reception level detected in the received Doppler signal separated by Code1 is the received signal of Tx#2. Also, the radar device can determine the Doppler frequency of the target because the deviation from the Doppler shift amount at the time of transmission for each transmitting antenna is the Doppler frequency of the target.

[0030] In addition, the Doppler frequency of the target is -1 / (2Tr)≦fdtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg When Loc<1 / (2Tr), the Doppler analysis unit (e.g., V-FFT#1 and V-FFT#2) observes an aliased Doppler frequency. Since the actual Doppler frequency differs in phase by 2π between 2Tr transmission periods from the Doppler frequency detected in the Doppler analysis units (V-FFT#1 and V-FFT#2), a phase rotation of π is added during the detection time difference Tr between V-FFT#1 and V-FFT#2. Therefore, when the code length Loc=2, the radar device can determine that there is Doppler frequency aliasing when a received signal corresponding to Code2 is determined in the separation of Code1, as shown in FIG. 2(b).

[0031] This separation and reception process of the CDDM signal enables the radar device to estimate the Doppler frequency of the radar reflection wave in the Doppler frequency range of ±1 / (2Tr). In this way, by transmitting CDDM signals, the detectable Doppler frequency range is expanded to ±1 / 2Tr. For example, compared to Patent Document 5, the detectable Doppler frequency range is expanded by Nt times.

[0032] [Application of Coded Doppler Multiplexing (CDDM) Transmission to Polarimetric MIMO Radar] As described above, in a MIMO radar using coded Doppler multiplexing, for example, a separation process of a coded Doppler multiplexed signal is performed (hereinafter referred to as "coded Doppler multiplexing separation" or "CDDM separation") to estimate the Doppler frequency of a target based on the received power of the received Doppler frequency after code separation of the reflected wave from the target.

[0033] For this reason, when CDDM is applied to a polarized MIMO radar, the following can be expected.

[0034] In a polarized MIMO radar, for example, a phenomenon may occur in which the reception level of a reflected wave varies greatly depending on the polarization of the transmitting and receiving antennas. When transmitting antennas of different polarizations are used in a polarized MIMO radar, the reception level of a reflected wave from a transmitting antenna of one polarization may be significantly attenuated compared to the reception level of a reflected wave from a transmitting antenna of another polarization. Therefore, when multiplexing is performed using CDDM in a polarized MIMO radar, CDDM separation may become difficult due to a large difference (or ratio) in the reception level of the reflected wave between transmitting antennas of different polarizations. When CDDM separation becomes difficult, the target detection performance of the MIMO radar may deteriorate, or CDDM separation may be erroneous, resulting in erroneous Doppler estimation or deterioration of angle measurement performance.

[0035] Below, an example will be described in which CDDM separation becomes difficult in a polarized MIMO radar that applies CDDM.

[0036] Here, as an example, a case will be described in which a MIMO radar is configured using two transmitting antennas for each of left-handed circular polarization (hereinafter also referred to as "LC") and right-handed circular polarization (hereinafter also referred to as "RC") (respectively denoted as LC-2Tx and RC-2Tx) (e.g., the number of transmitting antennas Nt=4). For example, a polarized antenna corresponding to left-handed circular polarization is called an "LC polarized antenna" (e.g., an LC polarized transmitting antenna or an LC polarized receiving antenna), and a polarized antenna corresponding to right-handed circular polarization is called an "RC polarized antenna" (e.g., an RC polarized transmitting antenna or an RC polarized receiving antenna).

[0037] For example, a case will be described in which a MIMO radar receives a single reflected wave (a reflected wave reflected once by an object) using an LC polarized receiving antenna. A reflected wave signal corresponding to a transmission signal from an RC polarized transmitting antenna (also called, for example, a "received signal corresponding to an RC polarized transmitting antenna") becomes a received signal as RC polarization, and when a received signal corresponding to an RC polarized transmitting antenna is received by an LC polarized receiving antenna, it is received in cross polarization. For this reason, the reception level of a received signal corresponding to an RC polarized transmitting antenna at an LC polarized receiving antenna is lower (depending on the cross polarization discrimination of the antenna, for example, a reception level lower by 10 dB or more) than the reception level of a reflected wave signal corresponding to a transmission signal from an LC polarized transmitting antenna (also called, for example, a "received signal corresponding to an LC polarized transmitting antenna"). For example, the reception level of a received signal corresponding to an RC polarized transmitting antenna may be lower than the noise level depending on the reception quality (for example, Signal to Noise Ratio (SNR)), and it may be difficult to detect a Doppler frequency peak in a MIMO radar.

[0038] Fig. 3 is a diagram showing an example of signals transmitted by CDDM in a polarized MIMO radar. In Fig. 3, the MIMO radar is configured using a total of four antennas Tx#1 to #4, including two LC-polarized transmitting antennas and two RC-polarized transmitting antennas as differently polarized transmitting antennas. Here, Tx#1 and Tx#2 are LC-polarized transmitting antennas, and Tx#3 and Tx#4 are RC-polarized transmitting antennas. In the example of Fig. 3, signals are received using an LC-polarized receiving antenna.

[0039] For example, for four Tx#1 to #4, as shown in FIG. 3(a), the Doppler multiplexing number N DM =3, code multiplex number N CM = 2 is assigned to each transmit antenna. CDDM assigns a set of a mutually different DDM signal (any of DOP1, DOP2, and DOP3) and a code (any of Code1 and Code2) to each transmit antenna.

[0040] Also in Fig. 3, black circles (●) indicate the allocation of CDDM signals to the LC polarized transmitting antennas (Tx#1 and Tx#2), with Tx#1 and Tx#2 being assigned the set of DopCode#1=(DOP1, Code1) and DopCode#2=(DOP2, Code1). Also in Fig. 3, white circles (○) indicate the allocation of CDDM signals to the RC polarized transmitting antennas (Tx#3 and Tx#4), with Tx#3 and Tx#4 being assigned the set of DopCode#3=(DOP3, Code2) and DopCode#4=(DOP1, Code2).

[0041] For example, when a CDDM signal is assigned as shown in (a) of Figure 3 and an LC polarized receiving antenna receives a single reflected wave, the receiving level of the receiving signal (R) corresponding to the RC polarized transmitting antenna may be lower than the receiving signal (L) corresponding to the LC polarized transmitting antenna, as shown in (b) of Figure 3. Here, in Figure 3, the size of the black circles (●) and white circles (○) represents the receiving power. The smaller the size of the black circles (●) and white circles (○), the lower the receiving power (e.g., the lower the receiving power is, approximately at the noise level).

[0042] Also, for example, a case will be described in which a MIMO radar receives a wave reflected twice (a wave reflected twice by an object) using an LC polarized receiving antenna. Since the received signal corresponding to the LC polarized transmitting antenna is reflected twice, the received signal becomes a RC polarized wave instead of an LC polarized wave, and the LC polarized receiving antenna receives a cross-polarized wave. Therefore, the level of the received signal corresponding to the LC polarized transmitting antenna is a lower reception level (depending on the cross-polarized discrimination degree of the antenna, for example, a reception level lower by 10 dB or more) compared with the received signal corresponding to the RC polarized transmitting antenna. For example, depending on the reception quality (SNR), the reception level of the received signal corresponding to the LC polarized transmitting antenna may be below the noise level, making it difficult to detect a Doppler frequency peak in the MIMO radar.

[0043] For example, when a CDDM signal is assigned as shown in (a) of Figure 3 and the LC polarized receiving antenna receives two reflected waves, the reception level of the received signal (L) corresponding to the LC polarized transmitting antenna may be lower than the received signal (R) corresponding to the RC polarized transmitting antenna, as shown in (c) of Figure 3.

[0044] Here, when the Doppler frequency of the reflected wave from the target and the number of reflections are unknown in advance, it is difficult for the MIMO radar to determine whether the reception level of the received signal corresponding to the RC polarized transmitting antenna or the reception level of the received signal corresponding to the LC polarized transmitting antenna has decreased, for example, based on the reception level shown in (b) or (c) of FIG. 3. Also, for example, it is difficult for the MIMO radar to determine which transmitting antenna used for CDDM transmission the detected Doppler frequency peak corresponds to, based on the reception level shown in (b) or (c) of FIG. For this reason, it becomes difficult for the MIMO radar to separate the CDDM signal, and it becomes difficult to determine the Doppler frequency f of the reflected wave from the target (for example, called the "target reflected wave") dtg -1 / (2Tr)≦f dtg < 1 / (2Tr) range, it becomes difficult to determine.

[0045] For example, if the target reflected wave is a single reflected wave and the Doppler frequency is f dtg = 0 (case i in the upper part of Fig. 3(b) where the reception level of the reception signal corresponding to the RC polarized transmission antenna drops to the noise level), and the target reflected wave is reflected twice and the Doppler frequency f dtg =-1 / (2Tr)+Δfd (the case where the reception level of the reception signal corresponding to the LC polarized transmitting antenna drops to about the noise level), the same peak frequency is observed for DOP1 and DOP2 at the reception Doppler frequency after code separation in Code1. Therefore, the result of CDDM separation in these cases does not become a unique response, and it becomes difficult for the radar device to distinguish between these cases.

[0046] In this way, in a coded Doppler multiplexed MIMO radar, the separation of multiplexed transmission signals is performed on the premise that the received levels of the CDDM signals assigned to each transmitting antenna are approximately the same, and that the received levels of coded Doppler signals to which no transmitting antenna is assigned are sufficiently low, approximately the noise level. In a polarized MIMO radar using CDDM, the assumptions in the CDDM separation process may not hold, as shown in (b) and (c) of Figure 3, and the CDDM separation process may fail.

[0047] In a non-limiting embodiment of the present disclosure, a method for improving the detection performance of a polarimetric MIMO radar using coded Doppler multiplexing (CDDM) transmission is described.

[0048] Note that, here, an example has been described in which a MIMO radar is constructed using two transmitting antennas for each of the left-handed circular polarization (LC) and right-handed circular polarization (RC) (e.g., the number of transmitting antennas Nt=4), but the polarizations used in the polarized MIMO radar are not limited to these.

[0049] For example, in a polarized MIMO radar, different linear polarizations that are orthogonal to each other may be applied. For example, vertical polarization may be applied instead of left-handed circular polarization (LC) and horizontal polarization may be applied instead of right-handed circular polarization (RC), and polarizations that are orthogonal to each other may be applied in a straight line. When a radar transmission wave is transmitted using such a vertically polarized and horizontally polarized transmission antenna, the closer the incident angle at which the radar transmission wave is reflected on a target is to the Brewster angle, the weaker the reflected wave reception level of either the vertically polarized or horizontally polarized wave may be compared to the other polarized wave. In a MIMO radar, for example, when such a reflected wave is received using a polarized reception antenna corresponding to either the vertically polarized or horizontally polarized wave, the received signal corresponding to either the vertically polarized or horizontally polarized transmission antenna is received in cross polarization, and may have a smaller reception level (depending on the cross polarization discrimination of the antenna, for example, a reception level that is 10 dB or more lower) compared to the received signal corresponding to the other polarized transmission antenna. Depending on the reception quality (SNR), the received signal with a reduced reception level may fall below the noise level, making it difficult to detect the Doppler frequency peak in the MIMO radar.

[0050] For example, if vertical polarization is applied instead of left-handed circular polarization (LC) and horizontal polarization is applied instead of right-handed circular polarization (RC), and a CDDM signal is assigned as shown in Figure 3(a), the received signal may be as shown in Figure 3(b) or Figure 3(c).

[0051] Even when vertically and horizontally polarized transmitting antennas are used, it is difficult for the MIMO radar to determine whether the receiving level of the transmission signal from the horizontally polarized transmitting antenna has decreased or the receiving level of the transmission signal from the vertically polarized transmitting antenna has decreased, based on, for example, the receiving levels shown in (b) or (c) of Fig. 3. This makes it difficult for the MIMO radar to separate the CDDM signal, for example, and to determine the Doppler frequency fd of the target reflected wave within the range of -1 / (2Tr)≦fd < 1 / (2Tr).

[0052] Hereinafter, an embodiment according to an example of the present disclosure will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and the description thereof will be omitted to avoid duplication.

[0053] The following describes a configuration (e.g., a MIMO radar configuration) in which a radar device transmits different transmit signals simultaneously multiplexed from multiple transmit antennas in a transmit branch, and a receive branch separates each transmit signal for receiving processing.

[0054] In addition, the following describes, as an example, the configuration of a radar system using a frequency-modulated pulse wave such as a chirp pulse (also called fast chirp modulation). However, the modulation system is not limited to frequency modulation. For example, an embodiment of the present disclosure is also applicable to a radar system using a pulse compression radar that transmits a pulse train after phase modulation or amplitude modulation.

[0055] The radar device also performs, for example, Doppler multiplexing. Furthermore, the radar device encodes (for example, CDM (Code Division Multiplexing)) signals (hereinafter referred to as "Doppler multiplexing (DDM) transmission signals") to which different phase rotations (for example, phase shifts) corresponding to the number of Doppler multiplexes are applied in the Doppler multiplexing, and transmits the signals multiplexed (hereinafter referred to as "Coded Doppler Division Multiplexing (CDDM)").

[0056] [Radar device configuration] The radar device 10 in FIG. 4 includes a radar transmitter (transmitting branch) 100 and a radar receiver (receiving branch) 200.

[0057] The radar transmitter 100 generates a radar signal (radar transmission signal) and transmits the radar transmission signal at a specified transmission period (hereinafter referred to as the "radar transmission period") using a transmitting antenna unit 109 (e.g., a transmitting array antenna) consisting of multiple transmitting antennas (e.g., Nt antennas).

[0058] The radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a receiving antenna unit 202 (e.g., a receiving array antenna) including multiple receiving antennas 202-1 to 202-Na. The radar receiver 200 processes the reflected wave signal received by each receiving antenna, for example, to detect the presence or absence of a target or estimate 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).

[0059] The radar device 10 may be mounted on a moving object such as a vehicle, and the positioning output (information on the estimation result) of the radar receiver 200 may be connected to a control device ECU (Electronic Control Unit) (not shown) such as an Advanced Driver Assistance System (ADAS) that improves collision safety or an autonomous driving system, and may be used for vehicle drive control or alarm call control.

[0060] The radar device 10 may be attached to a relatively high structure (not shown), such as a roadside utility pole or a traffic light. The radar device 10 may be used, for example, as a sensor in a support system for improving the safety of passing vehicles or pedestrians or a system for preventing intrusion of suspicious persons (not shown). The positioning output of the radar receiving unit 200 may be connected to a control device (not shown) in the support system for improving safety or the system for preventing intrusion of suspicious persons, and used for alarm generation control or abnormality detection control. The uses of the radar device 10 are not limited to these, and the radar device 10 may be used for other uses.

[0061] Moreover, a target 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 block, a curb, and the like.

[0062] [Configuration of radar transmitter 100] The radar transmitter 100 includes a radar transmission signal generator 101 , a phase rotation amount setting unit 105 , a phase rotation unit 108 , and a transmitting antenna unit 109 .

[0063] 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. Each component of the radar transmission signal generating unit 101 will be described below.

[0064] The transmission signal generation control unit 102 sets, for example, a transmission signal generation timing for each radar transmission cycle, and outputs information on the set transmission signal generation timing to the modulation signal generating unit 103 and the phase rotation amount setting unit 105 (for example, the Doppler shift setting unit 106). Here, the radar transmission cycle is denoted as Tr.

[0065] The modulation signal generating unit 103 periodically generates, for example, a sawtooth modulation signal based on information about the timing of transmission signal generation for each radar transmission period Tr input from the transmission signal generation control unit 102 .

[0066] Based on the modulation signal input from the modulation signal generating unit 103, the VCO 104 outputs a frequency modulation signal (hereinafter, referred to as a frequency chirp signal or chirp signal, for example) as a radar transmission signal (radar transmission wave) as shown in FIG. 5 to the phase rotation unit 108 and the radar receiving unit 200 (mixer unit 204, described later).

[0067] The phase rotation amount setting unit 105 sets an amount of phase rotation (e.g., an amount of phase rotation corresponding to CDDM transmission) to be applied to the radar signal for each radar transmission period Tr in the phase rotation unit 108, based on information related to the timing of transmission signal generation for each radar transmission period Tr input from the transmission signal generation control unit 102. The phase rotation amount setting unit 105 has, for example, a Doppler shift setting unit 106 and an encoding unit 107.

[0068] The Doppler shift setting unit 106 sets an amount of phase rotation corresponding to an amount of Doppler shift to be applied to a radar transmission signal (for example, a chirp signal) based on information relating to the timing of transmission signal generation for each radar transmission period Tr, for example.

[0069] The encoding unit 107 sets the amount of phase rotation corresponding to the encoding, for example, based on information on the timing of transmission signal generation for each radar transmission cycle Tr. The encoding unit 107 calculates the amount of phase rotation for the phase rotation unit 108, for example, based on the amount of phase rotation input from the Doppler shift setting unit 106 and the amount of phase rotation corresponding to the encoding, and outputs the amount of phase rotation to the phase rotation unit 108. The encoding unit 107 also outputs information on the code sequence (for example, each element of the orthogonal code sequence) used for the encoding to the radar receiving unit 200 (for example, the output switching unit 209).

[0070] The phase rotation unit 108 imparts the phase rotation amount input from the encoding unit 107 to the chirp signal input from the VCO 104, and outputs the phase-rotated signal to the transmitting antenna unit 109. For example, the phase rotation unit 108 includes a phase shifter, a phase modulator, and the like (not shown). The output signal from the phase rotation unit 108 is amplified to a specified transmission power and radiated into space from each transmitting antenna. For example, a radar transmission signal is imparted with a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence, and is then multiplexed and transmitted from a plurality of transmitting antennas.

[0071] Next, an example of a method for setting the amount of phase rotation in phase rotation setting section 105 will be described.

[0072] The Doppler shift setting unit 106 determines the amount of Doppler shift DOP ndm The amount of phase rotation φ for adding ndm and output to the encoding unit 107. Here, ndm=1 to N DM N DM is the number of different Doppler shift amounts set, which will be referred to as the "Doppler multiplex number" below.

[0073] In the radar device 10, in order to use the coding unit 107 for coding, the Doppler multiplexing number N DM may be set to be smaller than the number of transmitting antennas Nt used for multiplex transmission. DM must be 2 or more.

[0074] DOP1, DOP2, ~, DOP N_DM ("N_DM" is "N DM For example, the Doppler shift amounts may be set at equal intervals, or the Doppler shift amounts may be set at unequal intervals. N_DM In order to use the encoding by the encoding unit 107 described later, for example, 0≦DOP1,DOP2,~,DOP N_DM <1 / (TrL oc ) may be set to satisfy DOP1, DOP2, ~, DOP N_DM may be set to satisfy, for example, equation (1).

number

[0075] Also, for example, DOP1, DOP2, ~, DOP N_DM The minimum Doppler shift interval Δf MinInterval may satisfy the following formula (2). Note that the Doppler shift intervals (also written as Doppler multiple intervals or Doppler intervals) are DOP1, DOP2, ..., DOP N_DMHere, Loc represents the number of code elements. For example, Loc represents the code length of the code used in the encoding unit 107.

number

[0076] Also, for each DOP1, DOP2, ~, DOP N_DM The amount of phase rotation φ for adding ndm may be assigned, for example, as shown in the following equation (3).

number

[0077] In addition, the intervals are equal to Δf MinInterval When the Doppler shift amount is set to be equal to the Doppler shift amount (hereinafter referred to as "equally spaced Doppler shift amount setting"), DOP ndm The amount of phase rotation φ for adding ndm is assigned, for example, as shown in the following equation (4).

number

[0078] The minimum Doppler shift interval Δf MinInterval The narrower the interval between the Doppler shift amounts, the more likely it is that interference between DDM signals will occur, and the more likely it is that the target detection accuracy will decrease (e.g., deteriorate). Therefore, it is preferable to widen the interval between the Doppler shift amounts within a range that satisfies the constraints of equation (2). For example, when the equality sign is established in equation (2) (e.g., Δf MinInterval =1 / (T r N DM L OC )) can maximize the interval between DDM signals in the Doppler domain (hereinafter referred to as "maximum equal interval Doppler shift amount setting"). In this case, DOP1, DOP2, ..., DOP N_DM The phase rotation range is from 0 to less than 2π. DMEach of the two is assigned a different phase rotation. For example, DOP ndm The amount of phase rotation φ for adding ndm is assigned as shown in the following formula (5). Note that in the following, angles are expressed in radians.

number

[0079] In addition, DOP1, DOP2, ~, DOP N_DM The allocation of the phase rotation amount to be applied is not limited to the above allocation method. For example, the phase rotation amount allocation table may be used to allocate DOP1, DOP2, ..., DOP N_DM Phase rotation amount φ1,φ2,~,φ N_DM (However, "N_DM" is N DM ) may be randomly assigned.

[0080] In addition, when setting the amount of Doppler shift at equal intervals, Δf MinInterval =1 / (T r (N DM +N int )L OC ), the amount of phase rotation may be set as in the following equation (6). int takes an integer value.

number

[0081] The encoding unit 107 receives the N DM The phase rotation amount φ1,~,φ that gives the Doppler shift amount N_DM For each of the above, one or N CM The encoding unit 107 sets a phase rotation amount based on a plurality of code sequences up to 1000. The encoding unit 107 also sets a phase rotation amount based on both the Doppler shift amount and the code sequence, for example, an "encoded Doppler phase rotation amount" (hereinafter abbreviated as CDP amount) for generating an encoded Doppler multiplexed signal (CDDM signal), and outputs the amount to the phase rotation unit 108.

[0082] An example of the operation of the encoding unit 107 will now be described.

[0083] For example, the encoding unit 107 may generate a code number (for example, a code multiplexing number) N CM It is preferable to use code sequences that are low in correlation with each other or uncorrelated, for example, an orthogonal code sequence. Note that the code elements that make up the orthogonal code sequence are not limited to real numbers and may include complex values.

[0084] In the following, N CM The orthogonal code sequences are ncm ={OC ncm (1), O.C. ncm (2), ~, O.C. ncm (Loc)). ncm (noc) is the ncmth orthogonal code sequence Code ncm represents the noc-th code element in, where noc is the index of the code element, noc=1 to Loc.

[0085] The orthogonal code sequence used in the encoding unit 107 may be, for example, a Walsh-Hadamard code. CM A predetermined code length L capable of generating orthogonal code sequences OC An orthogonal code sequence is generated using

[0086] In the encoding unit 107, the ndm-th Doppler shift amount DOP input from the Doppler shift setting unit 106 is ndm The number of code multiplexes when encoding DDM signals using CDDM (ndm)" where ndm=1~N DM It is.

[0087] The encoding unit 107 encodes the DDM signal with a coding Doppler multiplexing number N CDDM (1), N CDDM (2), ~, and NCDDM (N DM ) is equal to the number of transmit antennas used for multiplex transmission, Nt. CDDM (ndm) is set. This enables the radar device 10 to perform multiplex transmission in the Doppler domain and the code domain (hereinafter referred to as coded Doppler multiplex transmission (CDDM transmission)) using Nt transmitting antennas.

[0088] Furthermore, the encoding unit 107 uses the uniform Doppler shift amount setting including the maximum uniform Doppler shift amount setting to determine the number of coded Doppler multiplexes N CDDM (1), N CDDM (2), ~, N CDDM (N DM ) for 1 or more N CM For example, the encoding unit 107 may set the code number N for all the coded Doppler multiplex numbers. CM At least one DOP ndm The number of coded Doppler multiplexes N CDDM (ndm) to N CM Therefore, DOP ndm In multiple combinations of the orthogonal code sequence and the DOP ndm The number of multiplexes (coded Doppler multiplexes) N CDDM (ndm) may be different from the coded Doppler multiplexing numbers associated with other Doppler shift amounts. For example, the coding unit 107 sets the coded Doppler multiplexing numbers for the DDM signals non-uniformly. With this setting, the radar device 10 can individually separate and receive the signals transmitted by CDDM from the multiple transmitting antennas over a Doppler range of ±1 / 2Tr by aliasing determination processing in the reception processing described in Patent Documents 6 and 7, for example.

[0089] The encoding unit 107 encodes the ndm-th Doppler shift amount DOP ndm The amount of phase rotation φ ndm For this, the CDP amount ψ ndc(ndm), ndm(m) and outputs it to phase rotation section 108.

number

[0090] Here, the subscript "ndc (ndm)" represents the Doppler shift DOP ndm The amount of phase rotation φ ndm Number of coded Doppler multiplexes N for CDDM (ndm) represents the index below. For example, ndc(ndm)=1,~, N CDDM (ndm). Also, 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.

[0091] For example, as shown in equation (7), the CDP amount ψ ndc(ndm),ndm (m) is the amount of Doppler shift DOP during the period of the transmission cycle of the code length Loc used for encoding. ndm The amount of phase rotation to be applied is kept constant (for example, the first term of equation (7)), and the code Code ndc(ndm) Each of the Loc code elements OC ndc(ndm) (1),~,OC ndc(ndm) (Loc) is assigned a corresponding phase rotation amount (the second term of equation (7)).

[0092] The encoding unit 107 also outputs an orthogonal code element index OC_INDEX to the radar receiver 200 (the output switching unit 209, which will be described later) for each transmission period (Tr). ndc(ndm) and varies cyclically within the range from 1 to Loc for each transmission period (Tr), as shown in the following equation (8).

number

[0093] Here, mod(x, y) is a modulo operator, which is a function that outputs the remainder after dividing x by y. Also, m=1 to Nc. Nc is the number of transmission periods used for radar positioning (hereinafter, referred to as the "radar transmission signal transmission count"). Also, the radar transmission signal transmission count Nc is set to be an integer multiple (Ncode multiple) of Loc. For example, Nc=Loc×Ncode.

[0094] Next, in the encoding unit 107, the number of encoded Doppler multiplexes N CDDM An example of a method for setting (ndm) non-uniformly will be described.

[0095] For example, the encoding unit 107 determines the number of orthogonal code sequences (for example, the number of code multiplexes or the number of codes) N CM For example, the number of orthogonal code sequences N CM and the number of Doppler multiplexes N DM satisfies the following relationship for the number Nt of transmit antennas used for multiplex transmission. (Number of orthogonal code sequences N CM ) × (Doppler multiplex number N DM )> Number of transmitting antennas used for multiplex transmission Nt

[0096] Next, the CDP amount ψ ndc(ndm), ndm An example of setting (m) will be explained.

[0097] For example, in the encoding unit 107, the number of transmitting antennas used for multiplex transmission is Nt=3, and the number of Doppler multiplexing N DM =2, code multiplex number N CM = 2, and an orthogonal code sequence Code1 = {1, 1} and Code2 = {1, -1} with a code length Loc = 2 is used. In this case, for example, as shown in FIG. CDDM (1)=1, N CDDM If (2)=2, the encoding unit 107 calculates the CDP amount ψ 1, 1 (m), ψ 1, 2 (m), ψ 2, 2 (m) and output it to the phase rotation unit 108. For example, the CDP amount ψ 1, 1When setting (m), the encoding unit 107 performs setting as in the following equation (9). Note that in Fig. 6, "◯" indicates the amount of Doppler shift and the orthogonal code that are used, and "×" indicates the allocation of the amount of Doppler shift and the orthogonal code that are not used.

number

[0098] The method for setting the amount of phase rotation in phase rotation setting section 105 has been described above.

[0099] In FIG. 4, the phase rotation unit 108 rotates the CDP amount ψ set in the phase rotation amount setting unit 105. ndc(ndm), ndm Based on (m), a phase rotation amount is applied to the chirp signal input from the radar transmission signal generator 101 for each transmission period Tr. Here, ndm=1 to N DM and ndc(ndm)=1~N CDDM (ndm).

[0100] The outputs from the Nt phase rotation units 108 (for example, called coded Doppler multiplexed signals (CDDM signals)) are amplified to a prescribed transmission power and then radiated into space from the Nt transmission antennas of the transmission antenna unit 109, respectively.

[0101] In the following, the CDP amount ψ ndc(ndm), ndm The phase rotation unit 108 that adds (m) is also written as "phase rotation unit PROT#[ndc(ndm), ndm]". Similarly, the transmission antenna that radiates the output of the phase rotation unit PROT#[ndc(ndm), ndm] into space is also written as "transmission antenna Tx#[ndc(ndm), ndm]". Here, ndm=1 to N DM and ndc(ndm) = 1~N CDDM (ndm). Alternatively, the Nt transmitting antennas are also denoted as Tx#1, Tx#2, ..., Tx#Nt. The CDP amounts given to the radar transmission signals transmitted from Tx#1, Tx#2, ..., Tx#Nt can be related in advance using a known table or the like. For example, the CDP amount ψ ndc(ndm), ndmBy determining (or detecting) (m), it becomes possible to determine (or detect) the transmitting antenna.

[0102] For example, in the example shown in FIG. 6, the encoding unit 107 transmits the CDP amount ψ 1, 1 (m), ψ 1, 2 (m), ψ 2, 2 (m) is input for each transmission period.

[0103] For example, the phase rotation unit PROT#[1, 1] rotates the chirp signal cp(t) generated by the radar transmission signal generator 101 for each transmission period by a phase rotation amount ψ 1, 1 The signal exp[jψ 1, 1 (m)]cp(t). The output of phase rotation unit PROT#[1,1] is output from transmitting antenna Tx#[1,1]. Here, cp(t) represents the chirp signal for each transmission period. Similarly, the output of phase rotation unit PROT#[1,2] is output from Tx#[1,2], and the output of phase rotation unit PROT#[2,2] is output from Tx#[2,2].

[0104] Above, CDP amount ψ ndc(ndm), ndm An example of the setting (m) was explained.

[0105] In this embodiment, the number of coded Doppler multiplexes N CDDM When (ndm) is set to non-uniform, the Doppler shift amount DOP ndm and orthogonal code sequence Code ncm In combination with each Doppler shift DOP ndm The orthogonal code sequence ncm The number of multiplexes (for example, the number of coded Doppler multiplexes N CDDM (ndm)) may vary.

[0106] In this embodiment, the number of coded Doppler multiplexes N CDDM If (ndm) is set uniformly, DOP ndm and orthogonal code sequence Codencm In combination with DOP ndm The corresponding orthogonal code sequence Code ncm The number of multiplexes (for example, the number of coded Doppler multiplexes N CDDM (ndm)) can be the same. In this case, DOP ndm The number of combinations of the orthogonal code sequence and the number of transmitting antennas may be the same as Nt (for example, N DM ×N CM =Nt).

[0107] In this embodiment, for example, Tx#1 to Tx#Nt of the transmitting antenna unit 109 include transmitting antennas of at least two different types of polarization, constituting a polarized radar. For example, Tx#1 to Tx#Nt may include transmitting antennas of different polarizations that are orthogonal to each other. Also, there may be a plurality of transmitting antennas of at least one of the multiple polarizations, and at least one transmitting antenna of the other polarization.

[0108] The radar device 10 (for example, the phase rotation amount setting unit 105) may set a different CDP amount ψ for each transmitting antenna, taking into account transmitting antennas of different polarizations, for example. ndc(ndm), ndm The radar device 10 (for example, the phase rotation unit 108) sets the CDP amount ψ ndc(ndm), ndm (m) may be added to a chirp signal and output to the transmitting antenna unit 105.

[0109] As a result, even if the reception levels of received signals corresponding to transmitting antennas of different polarizations differ greatly (for example, when the reception level difference or reception level ratio is equal to or greater than a threshold), the radar device 10 is able to separate the coded Doppler multiplexed signals, preventing degradation of positioning performance and radar detection performance (an example of operation will be described later).

[0110] An example of the operation of the phase rotation setting unit 105 in the radar transmitter 100 in a case where a polarized MIMO radar including at least two different types of transmitting antennas of different polarizations is configured will be described below.

[0111] In addition, the number of transmitting antennas Nt ≥ 3, and the number of Doppler multiplexing N DM ≧2, code multiplex number N CM ≧2, Nt <N DM ×N CM In this way, the number of transmitting antennas Nt is the total number of combinations of the Doppler shift amount and the code sequence (N DM ×N CM ) However, this is not limiting, and Nt may be smaller than the total number of combinations of the Doppler shift amount and the code sequence (N DM ×N CM ) may be the same number.

[0112] The number of different polarizations included in the transmitting antenna (hereinafter referred to as the number of transmission polarizations) is denoted as "NPL." The qth polarization is denoted as "PLq." q is an integer value within the number of transmission polarizations NPL (for example, q=1 to NPL).

[0113] In addition, the number of transmitting antennas for PLq polarization is set to "N PLq " is written as ". PLq ≧1, and 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 N PL1 ≧1, Number of PL2 polarized transmitting antennas N PL2 ≧1, and N PL1 +N PL2 =N t It is.

[0114] In addition, the number of Doppler multiplexes assigned to the PLq polarization transmission antenna is set to "N DM_PLq " where N DM_PLq ≦N DM For example, when NPL=2, N DM_PL1 , N DM_PL2 ≦N DM It is.

[0115] The radar device 10 has N transmission antennas for different PL1 and PL2 polarizations. PL1 , N PL2The phase rotation amount setting unit 105 in the radar transmitter 100 of the radar device 10 (for example, a polarized MIMO radar) determines the coded Doppler multiplexing number N CDDM (ndm) is set unevenly and the CDP amount ψ satisfies the following condition 1. ndc(ndm), ndm Set (m), where ndm=1~N DM and ndc(ndm)=1~N CDDM (ndm).

[0116] <Condition 1> For example, the Doppler shift amount and code sequence pattern (e.g., a coded Doppler multiplexing (CDDM) pattern) assigned to the PL1 polarized wave transmitting antenna is made different from the CDDM pattern assigned to the PL2 polarized wave transmitting antenna. For example, the phase rotation amount setting unit 105 sets a CDP amount ψ that satisfies different Doppler multiplexing (DDM) pattern conditions (e.g., a Doppler shift amount assignment pattern), different code multiplexing (CDM) pattern conditions (e.g., different code multiplexing numbers between DDM signals), or different DDM and CDM pattern conditions, for each of the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna. ndc(ndm), ndm Set (m).

[0117] For example, the condition for the different DDM pattern may be any one of the following conditions (also referred to as, for example, "Condition 1A" or "Condition 1 of 1A"). 1A) Different Doppler multiplex signal pattern conditions: (A-1) The Doppler multiplexing number corresponding to each polarization (for example, the Doppler multiplexing number of the transmission signal transmitted from the transmitting antenna of each polarization) is the same (for example, N DM_PL1 =N DM_PL2 However, N DM_PL1 =N DM_PL2 ≧2), including a different Doppler shift interval for each polarization (eg, an interval of Doppler shift amounts associated with the transmit antennas for each polarization). (A-2) The Doppler multiplexing number for each polarization (for example, the Doppler multiplexing number of the transmission signal transmitted from the transmitting antenna of each polarization) is different (N DM_PL1 ≠NDM_PL2 ). (A-3)N DM_PL1 ≧3, N DM_PL2 In the case where ≧3, when the same Doppler shift interval is included in the Doppler shift intervals for each polarization, the order of the Doppler shift intervals is different (cyclic mismatch).

[0118] Also, for example, the condition for the different CDM pattern may be any one of the following conditions (also referred to as "condition 1B," for example). (B-1) The code intervals (for example, code index intervals) assigned to each Doppler multiplexed signal are different (cyclic mismatch). (B-2) The code multiplexing numbers assigned to each Doppler multiplexed signal are different (cyclic mismatch).

[0119] Furthermore, the phase rotation amount setting unit 105 further sets the CDP amount ψ so as to satisfy, for example, the following condition 2. ndc(ndm), ndm (m) may be set.

[0120] <Condition 2> Signals transmitted from the same polarized transmitting antenna are multiplexed by a code multiplexing number that is unequal between Doppler multiplexed signals, and the code multiplexing number ranges from 1 to N. CM -1 or less (N CM (In the case of = 2, the code multiplexing number is 1.) For example, in a plurality of combinations of Doppler shift amounts and code sequences, for at least one of the transmitting antennas for PL1 polarization and PL2 polarization, the code multiplexing number by the code sequence associated with at least one Doppler shift amount is different from the code multiplexing number by the code sequence associated with the other Doppler shift amounts.

[0121] For example, in A-3 of Condition 1, when the values ​​of the multiple intervals of the Doppler shift amount assigned to the transmitting antenna of PL1 polarization and the transmitting antenna of PL2 polarization (e.g., combinations of Doppler shift intervals) are the same, the order on the Doppler frequency axis of the multiple Doppler shift intervals corresponding to the transmitting antenna of PL1 polarization may be different from the order on the Doppler frequency axis of the multiple Doppler shift intervals corresponding to the transmitting antenna of PL2 polarization. For example, a combination of intervals included in an array in which the intervals of the Doppler shift amount assigned to the transmitting antenna of PL1 polarization are arranged in ascending order on the Doppler frequency axis matches a combination of intervals included in an array in which the intervals of the Doppler shift amount assigned to the transmitting antenna of PL2 polarization are arranged in ascending order on the Doppler frequency axis, and the first array and the second array are different arrays in the circular permutation. When A-3 of Condition 1 is satisfied, the Doppler shift interval of the transmitting antenna for PL1 polarization and the Doppler shift interval of the transmitting antenna for PL2 polarization do not match (cyclic mismatch) even if either one is cyclically shifted in the Doppler frequency domain.

[0122] Also, for example, in B-1 of condition 1, the order on the Doppler frequency axis of the code sequences associated with the PL1 polarized transmitting antennas may be different from the order on the Doppler frequency axis of the code sequences associated with the PL2 polarized transmitting antennas. For example, an array in which the indexes of the code sequences corresponding to the Doppler shift amounts assigned to the PL1 polarized transmitting antennas are arranged in ascending order on the Doppler frequency axis is a different array in terms of circular permutation from an array in which the indexes of the code sequences corresponding to the Doppler shift amounts assigned to the PL2 polarized transmitting antennas are arranged in ascending order on the Doppler frequency axis. When B-1 of condition 1 is satisfied, the indexes of the code sequences corresponding to the Doppler shift amounts of the PL1 polarized transmitting antennas and the indexes of the code sequences corresponding to the Doppler shift amounts of the PL2 polarized transmitting antennas do not match (cyclic mismatch) even if one of them is cyclically shifted in the Doppler frequency domain.

[0123] Also, for example, in B-2 of Condition 1, the order on the Doppler frequency axis of the code multiplex numbers by the code sequence associated with the PL1 polarized transmitting antenna may be different from the order on the Doppler frequency axis of the code multiplex numbers by the code sequence associated with the PL2 polarized transmitting antenna. For example, an arrangement in which the code multiplex numbers corresponding to the Doppler shift amounts assigned to the PL1 polarized transmitting antenna are arranged in ascending order on the Doppler frequency axis is different from an arrangement in which the code multiplex numbers corresponding to the Doppler shift amounts assigned to the PL2 polarized transmitting antenna are arranged in ascending order on the Doppler frequency axis. When B-2 of Condition 1 is satisfied, the code multiplex numbers corresponding to each Doppler shift amount of the PL1 polarized transmitting antenna and the code multiplex numbers corresponding to each Doppler shift amount of the PL2 polarized transmitting antenna do not match (cyclic mismatch) even if one of them is cyclically shifted in the Doppler frequency domain.

[0124] By providing the transmitting antenna with a CDP amount that satisfies the above condition 1, the radar device 10 can obtain the following effects.

[0125] For example, the Doppler frequency of the received signal is subject to the coded Doppler phase rotation at the time of transmission as described above, as well as the Doppler frequency of the unknown target. Therefore, while maintaining the interval between each Doppler multiplexed signal, the Doppler frequency of each Doppler multiplexed signal may change in the positive or negative direction. For example, by satisfying 1A of Condition 1, the radar device 10 can distinguish between a case where the radar device 10 receives a coded Doppler multiplexed signal assigned to the transmitting antenna of PL1 polarization and does not receive a CDDM signal assigned to the transmitting antenna of PL2 polarization, and a case where the radar device 10 receives a CDDM signal assigned to the transmitting antenna of PL2 polarization and does not receive a CDDM signal assigned to the transmitting antenna of PL1 polarization, because the interval between the Doppler multiplexed signals or the Doppler multiplex number (e.g., DDM pattern) is different between the cases.

[0126] Furthermore, for example, by satisfying 1B of condition 1, the radar device 10 is able to distinguish between a case in which it receives a CDDM signal assigned to a transmitting antenna of PL1 polarization but does not receive a CDDM signal assigned to a transmitting antenna of PL2 polarization, and a case in which it receives a CDDM signal assigned to a transmitting antenna of PL2 polarization but does not receive a CDDM signal assigned to a transmitting antenna of PL1 polarization, because the code interval or the code multiplexing number (e.g., CDM pattern) at which the reception level is high after code separation of each Doppler multiplexed signal is different.

[0127] Therefore, by setting the CDP amount by the phase rotation amount setting unit 105 so as to satisfy condition 1, even if the reception levels of the reception signals corresponding to the transmitting antennas of different polarizations differ greatly, the radar device 10 can separate the CDDM signals and prevent deterioration of the positioning performance and radar detection performance.

[0128] Furthermore, by setting the CDP amount by the phase rotation amount setting unit 105 so as to satisfy condition 2 in addition to condition 1, the Doppler frequency range detectable by 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 in the case of one transmitting antenna (an example will be described later).

[0129] For example, in CDDM transmission by the radar device 10, both conditions 1 and 2 may be satisfied, or condition 1 may be satisfied but condition 2 may not be satisfied. For example, the following three cases are given as cases in which condition 1 is satisfied but condition 2 is not satisfied.

[0130] In case 1, neither the PL1 nor the PL2 polarization satisfies condition 2. The detectable Doppler frequency range fd is in the range of -1 / (2Tr)≦fd <1 / (2Tr) or -1 / (2Loc N DM_PL1 Tr)≦fd <1 / (2Loc N DM_PL1 Tr) range or -1 / (2Loc N DM_PL2 Tr)≦fd <1 / (2Loc N DM_PL2In case 2, the PL2 polarization does not satisfy condition 2, and the detectable Doppler frequency range fd is in the range of -1 / (2Tr)≦fd <1 / (2Tr) or -1 / (2Loc N DM_PL2 Tr)≦fd < 1 / (2Loc N DM_PL2 In case 3, the PL1 polarization does not satisfy condition 2, and the detectable Doppler frequency range fd is in the range of -1 / (2 Tr) ≦ fd < 1 / (2Tr) or -1 / (2Loc N DM_PL1 Tr)≦fd <1 / (2 Loc N DM_PL1 Tr) range.

[0131] In all cases 1 to 3, Nt>Loc N DM_PL1 Or Nt>Loc N DM_PL2 By satisfying the above, the detectable Doppler frequency range can be expanded beyond the Doppler detection range −1 / (2NtTr)≦fd<1 / (2NtTr) in the case of uniformly spaced Doppler multiplexing.

[0132] An example of setting the CDP amount in phase rotation amount setting section 105 will be described below.

[0133] In the following, the interval between the Doppler shift amounts applied to Tx#n1 and Tx#n2 is referred to as the Doppler shift interval "Δfd (n1, n2) " where Δfd (n1, n2) is the amount of Doppler shift DOP given to Tx#n1 n1 The amount of Doppler shift DOP given to Tx#n2 based on n2 Distance between (DOP n2 -DOP n1 ) where the Doppler shift interval Δfd (n1, n2) If the value of is negative (e.g., (DOP n2 -DOP n1 )<0), taking into consideration aliasing in the range of -1 / (2 Loc Tr) or more and less than 1 / (2 Loc Tr), which is the observation range of the Doppler analysis unit 210 described later, Δfd (n1, n2) =1 / Loc Tr-Δfd (n1, n2)Using the Doppler shift interval Δfd (n1, n2) The Doppler shift interval Δfd in the following explanation is calculated and expressed as a positive value. (n1, n2) The same notation is used for the descriptions of

[0134] <Setting example 1> Setting example 1 is a setting example of the CDP amount when condition 1 (satisfying different CDM pattern conditions) and condition 2 are satisfied. PL1 =2, N PL2 7 shows an example of setting the CDDM amount in phase rotation amount setting section 105 when = 2. In Fig. 7, black circles (●) indicate allocation of CDDM signals to the transmitting antennas (Tx #1 and Tx #2) of PL1 polarization, and white circles (○) indicate allocation of CDDM signals to the transmitting antennas (Tx #3 and Tx #4) of PL2 polarization.

[0135] In addition, in FIG. 7, the Doppler multiplexing number N DM = 3, and the Doppler shift setting unit 106 may set the three DOP1 to DOP3 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5), where the phase rotation amount φ1 = 0 for imparting DOP1 = 0, the phase rotation amount φ2 = 2π / 3 for imparting DOP2 = Δfd, and the phase rotation amount φ3 = 4π / 3 for imparting DOP3 = -Δfd (φ3 = -2π / 3 may also be used). As shown in Fig. 7, the intervals between DDM signals (also called Doppler multiplex intervals, Doppler shift intervals, or Doppler intervals) Δfd are equal, and Δfd = 1 / (6Tr).

[0136] In addition, in FIG. 7, the number of code multiplexes N CM = 2, and the encoding unit 107 uses orthogonal code sequences Code1 = {1, 1} and Code2 = {1, -1} with a code length Loc = 2. Also, in setting examples 2 and 3 described later, the code multiplexing number N CM =2 and similar signs may be used.

[0137] In FIG. 7, the number of transmitting antennas is Nt=4, and the number of Doppler multiplexing is N DM =3, code multiplex number N CM = 2, and Nt <N DM×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N CDDM (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0138] As shown in FIG. 7, in the encoding unit 107, the number of coded Doppler multiplexes for the DDM signals using the three DOP1 to DOP3 input from the Doppler shift setting unit 106 is N CDDM (1)=1, N CDDM (2)=1, N CDDM (3)=2. In this way, phase rotation amount setting section 105 sets the coded Doppler multiplexing numbers for the DDM signals non-uniformly.

[0139] In addition, in FIG. 7, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the DDM signals with DOP=3, for example, DDM signals using DOP1 and DOP3 are assigned (N DM_PL1 =2). Moreover, the encoding unit 107 assigns Code2 and Code1 to DOP1 and DOP3 assigned to Tx#1 and Tx#2 of the PL1 polarization, respectively. Hereinafter, such assignment will be referred to as the phase rotation amount setting unit 105 setting the CDP amount ψ 2, 1 (m), ψ 1, 3 7, the Doppler shift setting unit 106 sets the Doppler multiplex number N DM Of the Doppler multiplexed signals of =3, for example, Doppler multiplexed signals using Doppler shift amounts DOP2 and DOP3 are assigned (N DM_PL2 For example, the phase rotation amount setting unit 105 sets the CDP amount ψ 2, 2 (m), ψ 2, 3 Set (m).

[0140] In FIG. 7, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna is N DM_PL1 =N DM_PL2 = 2, which are the same. In addition, the Doppler shift intervals of the DDM signals assigned to Tx #1 and Tx #2 of the PL1 polarization are Δfd(1,2) = Δ2fd and Δfd(2,1) = Δfd, and the Doppler shift intervals of the DDM signals assigned to Tx #3 and Tx #4 of the PL2 polarization are Δfd(3,4) = Δfd and Δfd(4,3) = 2Δfd, which are the same.

[0141] Therefore, the setting of the CDP amount shown in FIG. 7 does not match any of the DDM pattern conditions of condition 1A.

[0142] In addition, in FIG. 7, the codes assigned to the PL1 polarization transmitting antenna for each of the DDM signals using DOP1 to DOP3 are [Code 2, no assignment, Code 1], and the code multiplexing number assigned to each DDM signal is 0 or 1.

[0143] In the following, the code index assigned to the transmitting antenna of PL1 polarization for each DDM signal using Doppler shift amounts DOP1 to DOP3 will be written as "CiPL1 = (2, *, 1)". In CiPL1, "*" indicates that no code is assigned. Also, when multiple codes are assigned to one DDM signal, it is expressed using "&". For example, when Code1 and Code2 are assigned to one DDM signal, it will be expressed as "1&2". The code index is also called the "code interval".

[0144] Moreover, hereinafter, the code multiplexing number assigned to the transmitting antenna of the PL1 polarization for each of the DDM signals using the Doppler shift amounts DOP1 to DOP3 will be written as "NcPL1=(1,0,1)" (in the case of FIG. 7).

[0145] 7, the codes assigned to the PL2 polarized transmitting antennas for each of the DDM signals using DOP1 to DOP3 are [no assignment, Code2, Code2], and the code multiplexing number assigned to each DDM signal is 0 or 1. As with the PL1 polarized signal, the code index assigned to the PL2 polarized transmitting antennas for each of the DDM signals using DOP1 to DOP3 is written as "CiPL2=(*,2,2)". Also, the code multiplexing number assigned to the PL2 polarized transmitting antennas for each of the DDM signals using DOP1 to DOP3 is written as "NcPL2=(0,1,1)".

[0146] In this way, the code multiplexing numbers assigned to each DDM signal for the PL1 polarization transmitting antenna and the PL2 polarization transmitting antenna are NcPL1 = (1, 0, 1) and NcPL2 = (0, 1, 1), which is a cyclic match and does not satisfy B-2 of condition 1.

[0147] On the other hand, for the transmitting antenna of PL1 polarization and the transmitting antenna of PL2 polarization, the code indexes assigned to each DDM signal are CiPL1 = (2, *, 1) and CiPL2 = (*, 2, 2), which are different (or cyclically inconsistent; hereinafter, this is also referred to as the code index intervals being different).

[0148] In addition, the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg If <1 / (2Tr), the Doppler frequency is aliased and observed by the Doppler analysis unit 210, which will be described later. In this case, the code index is CiPL1. alias =(1,*,2), and CiPL2 alias =(*,1,1), which is different (cyclic mismatch). Therefore, in the example of FIG. 7, the Doppler frequency of the target is -1 / (2Tr)≦f dtgIn the range of <-1 / (2Tr), the code index is cyclically inconsistent and the code intervals are different. Therefore, the code intervals assigned to each DDM signal are different between the polarizations, which satisfies B-1 of condition 1 and matches the different CDM pattern conditions.

[0149] From the above, the setting of the CDP amount shown in FIG.

[0150] In addition, in FIG. 7, the code multiplexing number assigned to each DDM signal in the PL1 polarization transmitting antenna is NcPL1=(1,0,1), and the code multiplexing number assigned to each DDM signal in the PL2 polarization transmitting antenna is NcPL2=(0,1,1). Both DDM signals are multiplexed and transmitted with code multiplexing numbers that are uneven between the DDM signals, and the code multiplexing number ranges from 1 to N. CM Included in the range of -1 or less.

[0151] Therefore, in the example of FIG. 7, signals transmitted from transmitting antennas of the same polarization (for example, PL1 polarization and PL2 polarization) are multiplexed with a code multiplexing number that is uneven between DDM signals, and the code multiplexing number ranges from 1 to N. CM 7 is included in the range of −1 or less. Therefore, the setting of the CDP amount shown in FIG.

[0152] Below, we will explain an example of the received signal at the output of the Doppler analysis unit 210 when, for example, a transmitting antenna unit 109 is used in which the PL1 polarization is left-handed circular polarization (LC) and the PL2 polarization is right-handed circular polarization (RC) based on the CDP amount setting in the phase rotation amount setting unit 105 as shown in Figure 7, and the receiving antenna unit 202 is an LC polarized (PL1 polarized) antenna.

[0153] FIG. 8 shows an example of the output of the Doppler analysis unit 210 for a target reflected wave at a certain distance index. For example, dtg Therefore, the radar device 10 calculates the Doppler frequency of the target from the amount of Doppler shift set in the radar transmitter 100 by f dtgIn FIG. 8, as an example, the Doppler shift of the reflected wave from the target is f dtg If f = 0, and dtg This shows the case where =-1 / (2Tr).

[0154] In Fig. 8, the size of the black circle (●) and the white circle (○) represents the received power. The smaller the size of the black circle (●) and the white circle (○), the smaller the received power (for example, the received power is as small as the noise level) (similar notations are used in the following setting examples).

[0155] Here, when the reflected wave of the radar transmission wave reflected by the target includes many scattered waves or is a reflected wave that is reflected many times, the reflected wave may include various polarized waves. Therefore, the difference in reception level of the received signal at the radar device 10 between the received signals corresponding to different polarized transmitting antennas (for example, the transmitting antenna of PL1 polarization and the transmitting antenna of PL2 polarization) is unlikely to be large. Therefore, the radar device 10 receives the received signal corresponding to the transmitting antenna of RC polarization (PL2 polarization) and the received signal corresponding to the transmitting antenna of LC polarization (PL1 polarization) at approximately the same reception level.

[0156] For example, in the CDP amount setting shown in Fig. 7, if the target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna (for example, LC polarization (PL1 polarization)) is not included, a received signal like that shown in Fig. 8(a) is obtained. As shown in Fig. 8(a), the reception levels of the received signals corresponding to Tx#1 and Tx#2 (PL1 polarization), and Tx#3 and Tx#4 (PL2 polarization) are almost the same.

[0157] Furthermore, for example, when the radar device 10 receives a reflected wave that is specularly reflected by a target (for example, specular reflection from a surface with few irregularities), the reception level may differ between polarized transmitting antennas. For example, a reception signal corresponding to an LC polarization (PL1 polarization) transmitting antenna will be a signal of the same polarization as that of an LC polarization (PL1 polarization) receiving antenna. On the other hand, for example, a reception signal corresponding to an RC polarization (PL2 polarization) transmitting antenna will be a signal of cross polarization with that of an LC polarization (PL1 polarization) receiving antenna. Therefore, the reception signal corresponding to an RC polarization (PL2 polarization) transmitting antenna may have a lower reception level (depending on the cross polarization discrimination of the antenna, for example, a reception level lower by 10 dB or more) compared to the reception signal corresponding to an LC polarization (PL1 polarization) transmitting antenna. For example, depending on the reception SNR, the reception signal corresponding to the transmitting antenna of the RC polarization (PL2 polarization) may be below the noise level, making it difficult for the radar device 10 to detect the peak of the Doppler frequency.

[0158] For example, in the CDP amount setting shown in Fig. 7, when a target reflected wave is included in which the RC polarization (PL2 polarization) is cross-polarized with respect to the polarization of the receiving antenna (for example, the LC polarization (PL1 polarization)), a received signal like that shown in Fig. 8(b) is obtained. As shown in Fig. 8(b), the reception levels of the received signals corresponding to Tx#3 and Tx#4 (PL2 polarization) are smaller than the reception levels of the received signals corresponding to Tx#1 and Tx#2 (PL1 polarization).

[0159] Furthermore, for example, when the radar device 10 receives a reflected wave that is specularly reflected by a target and then specularly reflected by a road surface or the like (for example, two specular reflections), the reception level may differ between the polarized transmitting antennas. For example, a reception signal corresponding to an RC polarized (PL2 polarized) transmitting antenna will be a signal of the same polarization as an LC polarized (PL1 polarized) receiving antenna. On the other hand, for example, a reception signal corresponding to an LC polarized (PL1 polarized) transmitting antenna will be a cross-polarized signal with respect to the LC polarized (PL1 polarized) receiving antenna. Therefore, the reception signal corresponding to an LC polarized (PL1 polarized) transmitting antenna may have a lower reception level (depending on the cross-polarized discrimination of the antenna, for example, 10 dB or more lower reception level) than the reception signal corresponding to an RC polarized (PL2 polarized) transmitting antenna. For example, depending on the reception SNR, the reception signal from the transmission antenna of the LC polarization (PL1 polarization) may be below the noise level, making it difficult for the radar device 10 to detect the peak of the Doppler frequency.

[0160] For example, in the CDP amount setting shown in Fig. 7, when a target reflected wave is included in which the LC polarization (PL1 polarization) is cross-polarized with respect to the polarization of the receiving antenna (e.g., LC polarization (PL1 polarization)), a received signal like that shown in Fig. 8(c) is obtained. As shown in Fig. 8(c), the reception levels of the received signals corresponding to Tx#1 and Tx#2 (PL1 polarization) are smaller than the reception levels of the received signals corresponding to Tx#3 and Tx#4 (PL2 polarization).

[0161] For example, as shown in (a) of Fig. 8, when there is no target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna, the radar device 10 receives reception signals corresponding to the RC polarization (PL2 polarization) transmitting antennas (Tx#3 and Tx#4) and the LC polarization (PL1 polarization) transmitting antennas (Tx#1 and Tx#2) at approximately the same level or within a range of about several dB to 6 dB. Here, in (a) of Fig. 8, the signals transmitted from Nt Tx#1 to Tx#4 consisting of the RC polarization (PL2 polarization) transmitting antennas and the LC polarization (PL1 polarization) transmitting antennas are divided by the coded Doppler multiplexing number N for each DDM signal. CDDMThe coded Doppler multiplexed signals are transmitted in CDDM using CDP amounts that make (ndm) non-uniform. Thus, the radar device 10 can separate the coded Doppler multiplexed signals based on the existing operation of separating coded Doppler multiplexed signals (see, for example, Patent Document 7).

[0162] Furthermore, as shown in Figures 8(b) and 8(c), when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives different CDDM signals (e.g., a CDDM signal that satisfies B-1 of condition 1) when the PL2 polarization includes a target reflected wave that is cross-polarized (Figure 8(b)) and when the PL1 polarization includes a target reflected wave that is cross-polarized (Figure 8(c)).

[0163] For example, in Fig. 8(b) i), the Doppler frequency of the target reflected wave, which is a cross-polarized wave of PL2 polarization, is f dtg = 0. In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (4Tr)≦f dtg <-1 / (4Tr), so CiPL1=(2,*,1).

[0164] In addition, in Fig. 8(b) ii), the Doppler frequency of the target reflected wave, which is a cross-polarized wave of PL2 polarization, is f dtg =-1 / (2Tr). In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr) and CiPL1 alias =(1,*,2).

[0165] For example, in FIG. 8(c) i), the Doppler frequency of the target reflected wave, which is a cross-polarized wave of the PL1 polarization, is f dtg= 0. In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (4Tr)≦f dtg <-1 / (4Tr), and so CiPL2 = (*,2,2).

[0166] In addition, in Fig. 8(c) ii), the Doppler frequency of the target reflected wave, which is a cross-polarized wave of the PL1 polarization, is f dtg =-1 / (2Tr). In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg <1 / (2Tr) and CiPL2 alias =(*,1,1).

[0167] In this way, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives reflected wave signals that are CDDM signals with different patterns (e.g., code index or code interval patterns) when the reception level of the receiving signal corresponding to the transmitting antenna of PL1 polarization decreases and when the reception level of the receiving signal corresponding to the transmitting antenna of PL2 polarization decreases, even if each DDM signal is received cyclically shifted on the Doppler frequency axis by the Doppler frequency of the target.

[0168] This enables the radar device 10 to determine, for example, based on the detected Doppler frequency peak after code separation, in the coded Doppler multiplex separation unit 212 (described later) whether a decrease in the reception level of the reception signal corresponding to the transmitting antenna of PL1 polarization has occurred or a decrease in the reception level of the reception signal corresponding to the transmitting antenna of PL2 polarization has occurred.

[0169] Also, for example, the PL1 polarized DDM signals are multiplexed and transmitted with a code multiplexing number NcPL1=(1,0,1) that is non-uniform between the DDM signals (for example, the code multiplexing number is 0 or 1 for three DDM signals, and therefore can be considered as non-uniform CDDM transmission). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal is a received signal corresponding to a transmitting antenna of LC polarization (PL1 polarization), the radar device 10 can separate the CDDM signal by using an existing separation operation of coded Doppler multiplexed signals.

[0170] Similarly, for example, the PL2 polarized DDM signals are multiplexed and transmitted with a code multiplexing number NcPL2=(0,1,1) that is non-uniform between the DDM signals (for example, the code multiplexing number for three DDM signals is either 0 or 1, and therefore can be regarded as non-uniform CDDM transmission). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal is a received signal corresponding to a PL2 polarized transmitting antenna, the radar device 10 can separate the CDDM signal by using an existing separation operation for coded Doppler multiplexed signals.

[0171] By operating the coded Doppler multiplexing separation unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output that associates a transmitting antenna with each CDDM signal.

[0172] <Setting example 2> Setting example 2 is a setting example of the CDP amount when condition 1 (satisfying different CDM pattern conditions (B-1 and B-2)) and condition 2 are satisfied. PL1 =3, N PL2 9 shows an example of setting the CDDM amount in phase rotation amount setting section 105 when the Doppler multiplexing number N is 3. In FIG. 9, black circles (●) indicate allocation of CDDM signals to the PL1 polarized wave transmitting antennas (Tx #1 to #3), and white circles (◯) indicate allocation of CDDM signals to the PL2 polarized wave transmitting antennas (Tx #4 to #6). Also, in FIG. 9, DM= 4, and the Doppler shift setting unit 106 may set the four DOP1 to DOP4 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 9, the phase rotation amounts for imparting DOP1 = 0, DOP2 = Δfd, DOP3 = -2Δfd, and DOP4 = -Δfd are φ1 = 0, φ2 = π / 2, φ3 = -π, and φ4 = 3π / 2 (φ4 = -π / 2 may also be used). As shown in Fig. 9, the Doppler multiplex intervals Δfd are equal, and Δfd = 1 / (8Tr).

[0173] In FIG. 9, the number of transmitting antennas is Nt=6, and the number of Doppler multiplexing is N DM =4, code multiplex number N CM = 2, and Nt <N DM ×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N CDDM (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0174] As shown in FIG. 9, in the encoding unit 107, the coding Doppler multiplexing numbers for the DDM signals using the four DOP1 to DOP4 input from the Doppler shift setting unit 106 are set as follows: CDDM (1)=1, N CDDM (2)=2, N CDDM (3)=2, N CDDM (4)=1. In this way, phase rotation amount setting section 105 sets the coded Doppler multiplexing numbers for the DDM signals non-uniformly.

[0175] In FIG. 9, the Doppler shift setting unit 106 sets the Doppler multiplex number N DM Of the Doppler multiplexed signals of =4, for example, Doppler multiplexed signals using Doppler shift amounts DOP1 and DOP2 are assigned (N DM_PL1 = 2). The phase rotation amount setting unit 105 sets the CDP amount ψ 1, 1 (m), ψ 1,2 (m), ψ 2, 2 Set (m).

[0176] In FIG. 9, the Doppler shift setting unit 106 sets the Doppler multiplex number N DM Of the Doppler multiplexed signals of =4, for example, Doppler multiplexed signals using Doppler shift amounts DOP3 and DOP4 are assigned (N DM_PL2 For example, the phase rotation amount setting unit 105 sets the CDP amount ψ 1, 3 (m), ψ 2, 3 (m), ψ 1, 4 Set (m).

[0177] In FIG. 9, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the transmission antennas of the PL1 polarization and the PL2 polarization is N DM_PL1 =N DM_PL2 = 2, which are identical. Additionally, the Doppler shift intervals of the DDM signals assigned to Tx #1 to #3 of PL1 polarization are Δfd(1,2) = Δfd, Δfd(2,1) = 3Δfd, and the Doppler shift intervals of the DDM signals assigned to Tx #4 to #6 of PL2 polarization are Δfd(3,4) = Δfd, Δfd(4,3) = 3Δfd, which are identical (cyclically coincident).

[0178] Therefore, the setting of the CDP amount shown in FIG. 9 does not match any of the DDM pattern conditions of condition 1A.

[0179] In addition, in FIG. 9, the code indexes assigned to the PL1 polarization transmitting antenna and the PL2 polarization transmitting antenna for each of the DDM signals using DOP1 to DOP4 are CiPL1=(1,1&2,*,*) and CiPL2=(*,*,1&2,1), which results in a cyclic mismatch and the code index intervals are different, thereby satisfying B-1 of condition 1.

[0180] In addition, in FIG. 9, the code multiplexing numbers assigned to the PL1 polarization transmitting antenna and the PL2 polarization transmitting antenna for each of the DDM signals using DOP1 to DOP4 are NcPL1=(1,2,0,0) and NcPL2=(0,0,2,1), which results in a cyclic mismatch and the code multiplexing numbers are different, thereby satisfying B-2 of condition 1.

[0181] In addition, the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg If <1 / (2Tr), the Doppler frequency is observed by the Doppler analysis unit 210 described later. In this case, the code index is CiPL1. alias =(2,1&2,*,*), CiPL2 alias =(*,*,1&2,2), which is different (cyclic mismatch). Therefore, in the example of Figure 9, 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. Therefore, B-1 and B-2 of condition 1 are satisfied, and different CDM pattern conditions are met.

[0182] From the above, the setting of the CDP amount shown in FIG.

[0183] In FIG. 9, the code multiplexing number assigned to each DDM signal in the PL1 polarization transmitting antenna is NcPL1=(1,2,0,0), and the code multiplexing number assigned to each DDM signal in the PL2 polarization transmitting antenna is NcPL2=(0,0,2,1). Both DDM signals are multiplexed and transmitted with code multiplexing numbers that are uneven between the DDM signals, and the code multiplexing number ranges from 1 to N CM Included in the range of -1 or less.

[0184] Therefore, in the example of FIG. 9, signals transmitted from transmitting antennas of the same polarization (for example, PL1 polarization and PL2 polarization) are multiplexed with a code multiplexing number that is uneven between DDM signals, and the code multiplexing number ranges from 1 to N. CM9 is included in the range of −1 or less. Therefore, the setting of the CDP amount shown in Fig. 9 is an example of a setting that satisfies condition 2 for both the PL1 polarization and the PL2 polarization.

[0185] When the CDP amount setting shown in Fig. 9 does not include a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna, the radar device 10 receives the received signals corresponding to the PL1 polarization transmitting antenna and the PL2 polarization transmitting antenna at approximately the same level or within a range of about several dB to 6 dB. Here, in Fig. 9, signals transmitted from Nt (=6) transmitting antennas consisting of the PL1 polarization transmitting antenna and the PL2 polarization transmitting antenna are CDDM transmitted using a CDP amount that makes the coded Doppler multiplexing number for each DDM signal non-uniform. Therefore, the radar device 10 can separate the coded Doppler multiplexed signal based on an existing coded Doppler multiplexed signal separation operation (see Patent Document 7, for example).

[0186] Furthermore, for example, in the CDP amount setting shown in FIG. 9, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives different CDDM signals (e.g., CDDM signals that satisfy B-1 and B-2 of condition 1) when the target reflected wave includes a cross-polarized PL2 polarization as shown in FIG. 10(a) and when the target reflected wave includes a cross-polarized PL1 polarization as shown in FIG. 10(b).

[0187] For example, in (a) of FIG. 10, the Doppler frequency of the target reflected wave, which is a cross-polarized wave of PL2 polarization, is f dtg = 0. In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (4Tr)≦f dtg <-1 / (4Tr), CiPL1=(1,1&2,*,*). Also, if 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 CiPL1. alias =(2,1&2,*,*).

[0188] For example, in FIG. 10(b), the Doppler frequency of the target reflected wave, which is a cross-polarized wave of the PL1 polarization, is f dtg = 0. In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (4Tr)≦f dtg <-1 / (4Tr), CiPL2=(*,*,1&2,1). Also, if 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).

[0189] In this way, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna (e.g., LC polarization) is included, the radar device 10 receives reflected wave signals that are CDDM signals with different patterns (e.g., code index or code interval patterns) when the reception level of the receiving signal corresponding to the transmitting antenna of PL1 polarization decreases and when the reception level of the receiving signal corresponding to the transmitting antenna of PL2 polarization decreases, even if each DDM signal is received cyclically shifted on the Doppler frequency axis by the Doppler frequency of the target.

[0190] This enables the radar device 10 to determine, for example, based on the peak of the Doppler frequency after the detected code separation, in the coded Doppler multiplex separation unit 212 described later whether a decrease in the reception level of the reception signal corresponding to the transmitting antenna of the PL1 polarization (e.g., LC polarization) has occurred or whether a decrease in the reception level of the reception signal corresponding to the transmitting antenna of the PL2 polarization (e.g., RC polarization) has occurred.

[0191] Also, for example, the PL1 polarized DDM signals are multiplexed and transmitted with a code multiplexing number NcPL1=(1,2,0,0) that is uneven between Doppler multiplexes (for example, for four DDM signals, the code multiplexing number is 0, 1 or 2, and therefore can be considered as uneven CDDM transmission). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal is a received signal corresponding to the PL1 polarized transmitting antenna, the radar device 10 can separate the coded Doppler multiplexed signal by using an existing coded Doppler multiplexed signal separation operation.

[0192] Similarly, for example, the PL2 polarized DDM signal is multiplexed and transmitted with a code multiplexing number NcPL2=(0,0,2,1) that is uneven between Doppler multiplexes (for example, for four DDM signals, the code multiplexing number is 0, 1 or 2, and therefore it can be considered as uneven CDDM transmission). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal is a received signal corresponding to a PL2 polarized transmitting antenna, the radar device 10 can separate the CDDM signal by using an existing separation operation of coded Doppler multiplexed signals.

[0193] By operating the coded Doppler multiplexing separation unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output that associates a transmitting antenna with each CDDM signal.

[0194] <Setting example 3> Setting example 3 is a setting example of the CDP amount when condition 1 (different CDM pattern condition) is satisfied but condition 2 is not satisfied. PL1 =2, N PL2 11 shows an example of setting the CDDM amount in phase rotation amount setting section 105 when = 1. In Fig. 11, black circles (●) indicate the allocation of CDDM signals to the PL1 polarized transmitting antennas (Tx #1 and Tx #2), and white circles (○) indicate the allocation of CDDM signals to the PL2 polarized transmitting antenna (Tx #3).

[0195] In addition, in FIG. 11, the Doppler multiplexing number N DM = 2, and the Doppler shift setting unit 106 may set two DOP1 and DOP2 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 11, the phase rotation amount φ1 that imparts DOP1 = 0 is φ1 = 0, and the phase rotation amount φ2 that imparts DOP2 = -Δfd is φ2 = -π. As shown in Fig. 11, the Doppler multiplex interval Δfd is equal, and Δfd = 1 / (4Tr).

[0196] In FIG. 11, the number of transmitting antennas is Nt=3, and the number of Doppler multiplexing is N DM =2, code multiplex number N CM = 2, and Nt <N DM ×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N CDDM (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0197] As shown in FIG. 11, in the encoding unit 107, the number of coded Doppler multiplexing for the DDM signals using the two DOP1 and DOP2 input from the Doppler shift setting unit 106 is N CDDM (1)=1, N CDDM (2)=2. In this way, phase rotation amount setting section 105 sets the coded Doppler multiplexing numbers for the DDM signals non-uniformly.

[0198] In FIG. 11, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the DDM signals with DOP=2, for example, DDM signals using DOP1 and DOP2 are assigned (N DN_PL1 For example, the phase rotation amount setting unit 105 sets the CDP amount ψ 1, 1 (m), ψ 1, 2 (m) are set respectively.

[0199] In FIG. 11, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DMFor example, among the DDM signals with DOP=2, the DDM signal with DOP2 is assigned (N DM_PL2 =1), the phase rotation amount setting unit 105 sets the CDP amount ψ 2, 2 Set (m).

[0200] In FIG. 11, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna is N DM_PL1 =2, N DM_PL2 = 1, which is a different Doppler multiplexing number. Therefore, the setting of the CDP amount shown in FIG.

[0201] In addition, in FIG. 11, the code indexes assigned to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna for the DDM signals using DOP1 and DOP2 are CiPL1=(1,1) and CiPL2=(*,2), respectively, which are cyclically inconsistent and have different code index intervals. Also, when the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg If <1 / (2Tr), the Doppler frequency is observed by the Doppler analysis unit 210 described later. In this case, the code index is CiPL1. alias =(2,2), CiPL2 alias =(*,1), which results in a circular mismatch. Therefore, if the Doppler frequency of the target is -1 / (2Tr)≦f dtg Within the range of <-1 / (2Tr), the code index is cyclically inconsistent and the code intervals are different, so B-1 of condition 1 is satisfied.

[0202] 11, the code multiplexing numbers assigned to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna for each of the DDM signals using DOP1 and DOP2 are NcPL1=(1,1), NcPL2=(0,1), resulting in a cyclic mismatch, the code multiplexing numbers are different, and satisfy B-2 of condition 1. Therefore, the setting of the CDP amount shown in FIG. 11 satisfies B-1 and B-2 of condition 1, and matches different CDM pattern conditions.

[0203] From the above, the setting of the CDP amount shown in FIG.

[0204] Also, in FIG. 11, in the transmission antenna for PL1 polarization, the code multiplexing number assigned to each DDM signal is NcPL1=(1,1), and the DDM signals are multiplexed and transmitted with a uniform code multiplexing number.

[0205] On the other hand, in FIG. 11, the code multiplexing number assigned to each DDM signal in the PL2 polarization transmission antenna is NcPL2=(0,1), and the DDM signals are multiplexed with non-uniform code multiplexing numbers, and the code multiplexing number ranges from 1 to N CM Included in the range of -1 or less.

[0206] Therefore, in the example of FIG. 11, the signals transmitted from the PL2 polarization transmitting antenna are multiplexed with a code multiplexing number that is uneven between DDM signals, and the code multiplexing number ranges from 1 to N. CM In the signal transmitted from the PL1 polarization transmitting antenna, the code multiplexing number assigned to each DDM signal is uniform. Therefore, the CDP amount setting shown in Fig. 11 is an example of a setting that satisfies condition 2 in the PL2 polarization but does not satisfy condition 2 in the PL1 polarization.

[0207] When the CDP amount setting shown in Fig. 11 does not include a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna, the radar device 10 receives the received signals corresponding to the PL1 polarization transmitting antenna and the PL2 polarization transmitting antenna at approximately the same level or within a range of about several dB to 6 dB. Here, in Fig. 11, signals transmitted from Nt (=3) transmitting antennas consisting of the PL1 polarization transmitting antenna and the PL2 polarization transmitting antenna are CDDM transmitted using a CDP amount that makes the coded Doppler multiplexing number for each DDM signal non-uniform. Therefore, the radar device 10 can separate the coded Doppler multiplexed signal based on an existing coded Doppler multiplexed signal separation operation (see Patent Document 7, for example).

[0208] Furthermore, for example, in the CDP amount setting shown in FIG. 11, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives different CDDM signals (e.g., CDDM signals that satisfy 1A and 1B of condition 1) when the PL2 polarization includes a target reflected wave that is cross-polarized as shown in FIG. 12(a) and when the PL1 polarization includes a target reflected wave that is cross-polarized as shown in FIG. 12(b).

[0209] For example, in (a) of FIG. 12, the Doppler frequency of the target reflected wave, which is a cross-polarized wave of PL2 polarization, is f dtg = 0. In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (4Tr)≦f dtg <-1 / (4Tr), CiPL1=(1,1), and -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).

[0210] For example, in FIG. 12(b), the Doppler frequency of the target reflected wave, which is a cross-polarized wave of the PL1 polarization, is fdtg = 0. In the radar device 10, each DDM signal is cyclically shifted on the Doppler frequency axis according to the Doppler frequency of the target and received. The code Index assigned to each DDM signal is determined when the Doppler frequency of the target is -1 / (4Tr)≦f dtg <-1 / (4Tr), CiPL2=(*,2), and -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).

[0211] In this way, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna (e.g., LC polarization) is included, the radar device 10 receives reflected wave signals that are CDDM signals with different patterns (e.g., Doppler multiplexing number, code interval, or code multiplexing number pattern) when the reception level of the receiving signal corresponding to the transmitting antenna of PL1 polarization decreases and when the reception level of the receiving signal corresponding to the transmitting antenna of PL2 polarization decreases, even if each DDM signal is received cyclically shifted on the Doppler frequency axis by the Doppler frequency of the target.

[0212] This enables the radar device 10 to determine, for example, based on the peak (e.g., the number of peaks) of the Doppler frequency after the detected code separation, in the coded Doppler multiplex separation unit 212 described later, whether a decrease in the reception level of the reception signal corresponding to the transmitting antenna of the PL1 polarization (e.g., the LC polarization) has occurred or whether a decrease in the reception level of the reception signal corresponding to the transmitting antenna of the PL2 polarization (e.g., the RC polarization) has occurred.

[0213] Furthermore, for example, the PL1 polarized DDM signal is multiplexed and transmitted with a code multiplexing number NcPL1=(1,1) that is uniform between Doppler multiplexes (for example, since the code multiplexing number is 1 for two DDM signals, it can be considered as uniform CDDM transmission). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal corresponds to a PL1 polarized transmitting antenna, the radar device 10 can separate the Doppler multiplexed signal using an existing separation operation for Doppler multiplexed signals (for example, see Patent Document 5). In this case, the radar device 10 calculates the Doppler frequency fd of the target as -1 / (2 Loc N DM_PL1 Tr)≦fd<1 / (2 Loc N DM_PL1 Tr), and outputs corresponding to the transmitting antennas for each CDDM signal can be obtained.

[0214] Also, for example, the PL2 polarized DDM signal is multiplexed and transmitted with a code multiplexing number NcPL2=(0,1) that is uneven between Doppler multiplexes (for example, the code multiplexing number for two DDM signals is 0 or 1, and therefore can be regarded as uneven CDDM transmission). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal is a received signal corresponding to a PL2 polarized transmitting antenna, the radar device 10 can separate the CDDM signal by using an existing separation operation of a coded Doppler multiplexed signal.

[0215] When the radar device 10 determines that the received signal corresponds to the PL1 polarization transmitting antenna by the operation of the coded Doppler demultiplexing unit 212, the radar device 10 calculates the Doppler frequency fd of the target as −1 / (2 Loc N DM_PL1 Tr)≦fd<1 / (2 Loc N DM_PL1In addition, in cases other than when the received signal is determined to be a received signal corresponding to a PL1 polarization transmitting antenna, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr) and can obtain outputs corresponding to the transmitting antennas for each CDDM signal.

[0216] <Setting example 4> In the above-mentioned setting examples 1 to 3, the code multiplexing number N CM We have explained a setting example using the code of N = 2, but the code multiplexing number is N CM For example, the code multiplexing number N CM =4 may be set.

[0217] Setting example 4 is a setting example that satisfies condition 1 (different DDM pattern condition and CDM pattern condition) and condition 2 with code length 4. CM An example of setting the CDP amount in phase rotation amount setting section 105 when .DELTA..times ...

[0218] Figure 13 shows the number of transmit antennas, Nt=6, N PL1 =3, N PL2 13 shows an example of setting the CDDM amount in phase rotation amount setting section 105 when = 3. In Fig. 13, black circles (●) indicate allocation of CDDM signals to the transmitting antennas (Tx #1 to #3) of PL1 polarization, and white circles (○) indicate allocation of CDDM signals to the transmitting antennas (Tx #4 to #6) of PL2 polarization.

[0219] In addition, in FIG. 13, the Doppler multiplexing number N DM = 2, and the Doppler shift setting unit 106 may set two DOP1 and DOP2 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 13, the phase rotation amount φ1 = 0 for applying DOP1 = 0, and the phase rotation amount φ2 = -π for applying DOP2 = -Δfd. As shown in Fig. 13, the Doppler multiplex interval Δfd is equal, and Δfd = 1 / (4Tr).

[0220] In addition, in FIG. 13, the number of code multiplexes N CM = 4, and encoding section 107 uses, for example, orthogonal code sequences Code1 = {1, 1, 1, 1}, Code2 = {1, -1, 1, -1}, Code3 = {1, 1, -1, -1}, and Code4 = {1, -1, -1, 1} of the Walsh-Hadamard code with code length Loc = 4.

[0221] In FIG. 13, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#1 to Tx#3 of the PL1 polarization. 1, 1 (m), ψ 1, 2 (m), ψ 2, 2 (m), and for each of Tx#4 to Tx#6 of PL2 polarization, the CDP amount ψ 2, 1 (m), ψ 3, 1 (m), ψ 4, 1 13, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna is set to N DM_PL1 =2, N DM_PL2 = 1, which is a different Doppler multiplexing number. Therefore, the setting of the CDP amount shown in FIG.

[0222] In addition, in Fig. 13, the code indexes assigned to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna for the DDM signals using DOP1 and DOP2, respectively, are CiPL1 = (1, 1 & 2) and CiPL2 = (2 & 3 & 4, *), which are cyclically inconsistent and the code index intervals are different. In addition, in Fig. 13, the code multiplexing numbers assigned to the PL1 polarized wave transmitting antenna and the PL2 polarized wave transmitting antenna for the DDM signals using DOP1 and DOP2, respectively, are NcPL1 = (1, 2) and NcPL2 = (3, 0), which are cyclically inconsistent and the code multiplexing numbers are different. Therefore, the setting of the CDP amount shown in Fig. 13 satisfies B-1 and B-2 of condition 1 and matches different CDM pattern conditions.

[0223] From the above, the setting of the CDP amount shown in FIG.

[0224] In addition, in FIG. 13, the code multiplexing number assigned to each DDM signal in the PL1 polarization transmission antenna is NcPL1=(1,2), and the code multiplexing number assigned to each DDM signal in the PL2 polarization transmission antenna is NcPL2=(3,0). Both are multiplexed and transmitted with code multiplexing numbers that are uneven between DDM signals, and the code multiplexing number ranges from 1 to N CM Included in the range below -1 (=3).

[0225] Therefore, in FIG. 13, the signals transmitted from the PL1 polarized wave and the PL2 polarized wave transmitting antenna are multiplexed with a code multiplexing number that is uneven between the DDM signals, and the code multiplexing number ranges from 1 to N. CM 13 is an example of a setting that satisfies condition 2 for both the PL1 polarization and the PL2 polarization.

[0226] An example of setting the CDP amount in phase rotation amount setting section 105 has been described above.

[0227] [Configuration of radar receiver 200] 4, the radar receiver 200 includes a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. The radar receiver 200 also includes Na antenna system processors 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a coded Doppler demultiplexing unit 212, and a direction estimating unit 213. The Na antenna system processors 201-1 to 201-Na, the CFAR unit 211, the coded Doppler demultiplexing unit 212, and the direction estimating unit 213 may be collectively referred to as a receiving circuit. The receiving circuit estimates the direction of a target by using a reflected wave signal that is a transmission signal reflected by the target.

[0228] The receiving antennas Rx#1 to Rx#Na of the receiving antenna unit 202 receive reflected wave signals that are radar transmission signals reflected by targets, and output the received reflected wave signals to the corresponding antenna system processors 201 as received signals.

[0229] Each antenna system processing unit 201 includes a radio reception unit 203 and a signal processing unit 206 .

[0230] The signals received at the Na receiving antennas Rx#1 to Rx#Na are output to Na receiving radio units 203, respectively. In addition, the output signals from the Na receiving radio units 203 are output to Na signal processing units 206, respectively.

[0231] The radio reception unit 203 has a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with a chirp signal, which is a transmission signal, input from the radar transmission signal generation unit 101. The radio reception unit 203, for example, passes the output of the mixer unit 204 through the LPF 205. This outputs a beat signal with a frequency corresponding to the delay time of the reflected wave signal. For example, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulated wave), which is the transmission signal (radar transmission wave), and the frequency of the reception chirp signal (reception frequency modulated wave), which is the reception signal (radar reflected wave), is obtained as the beat frequency.

[0232] The signal processing unit 206 of each antenna system processing unit 201-z (where z=any of 1 to Na) has an AD conversion unit 207, a beat frequency analysis unit 208, an output switching unit 209, and a Doppler analysis unit 210.

[0233] The signal (eg, beat signal) output from the LPF 205 is converted by the AD conversion unit 207 in the signal processing unit 206 into discrete sample data that has been discretely sampled.

[0234] The beat frequency analysis unit 208 calculates Ndata The discrete sample data is subjected to frequency analysis processing (for example, FFT processing), whereby the signal processing unit 206 outputs a frequency spectrum in which a peak appears at a beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave).

[0235] Here, the beat frequency response output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 obtained by transmitting the m-th chirp pulse is called “RFT z (f b , m) where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,~,(N data / 2)-1, z = 1 to Na, m = 1 to N C The beat frequency index f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (e.g., the closer the distance to the target).

[0236] Also, the beat frequency index f b is calculated by the following equation (10): b ) can be transformed into the beat frequency index f b Let "distance index f b " It is called.

number

[0237] 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.

[0238] The output switching unit 209 selectively switches the output of the beat frequency analysis unit 208 for each transmission period to the OC_INDEX-th Doppler analysis unit 210 out of 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 setting unit 105.

[0239] The signal processing unit 206 has Loc Doppler analysis units 210-1 to 210-Loc. For example, data is input to the noc-th Doppler analysis unit 210 every Loc transmission periods (Loc×Tr) by the output switching unit 209. Therefore, the noc-th Doppler analysis unit 210 receives data (for example, beat frequency response RFT input from the beat frequency analysis unit 208) for Ncode transmission periods out of the Nc transmission periods. z (f b , m) to obtain the distance index f b Doppler analysis is performed for each Loc, where noc is the index of the code element, noc=1 to Loc.

[0240] For example, if Ncode is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is Ncode, and the maximum Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is ±1 / (2Loc×Tr). Also, the Doppler frequency index f s The Doppler frequency interval of is 1 / (Ncode×Loc×Tr), and the Doppler frequency index f s The range of f s = -Ncode / 2,~, 0,~,Ncode / 2-1.

[0241] In the following, as an example, a case where Ncode is a power of 2 will be described. If Ncode is not a power of 2, for example, by including zero-padded data, FFT processing is possible with a data size (FFT size) of a power of 2.

[0242] For example, the output VFT of the Doppler analysis unit 210 of the z-th signal processing unit 206z noc (f b , f s ) is expressed by the following formula (11), where j is the imaginary unit and z=1 to Na.

number

[0243] The processing in each component of the signal processing unit 206 has been described above.

[0244] [Example of operation of CFAR section 211] In FIG. 4, the CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the outputs of the Loc Doppler analyzers 210 of each of the first to Na-th signal processors 206, and calculates the distance index (hereinafter, f b_cf ) and the Doppler frequency index (f s_cf The CFAR unit 211 extracts, for example, the output VFT of the Doppler analysis unit 210 of the first to Na-th signal processing units 206. z noc (f b , f s ) are power-added, and two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity) or CFAR processing combining one-dimensional CFAR processing is performed (for example, the processing disclosed in Non-Patent Document 2 may be applied).

[0245] DOP ndm The amount of phase rotation φ for adding ndm For example, when equation (5) is used, the intervals of the Doppler shift amount in the Doppler frequency domain in the output of the Doppler analysis unit 210 are equal, and if the interval ΔFD of the Doppler shift amount is expressed by the interval of the Doppler frequency index, then ΔFD=Ncode / N DM Therefore, in the output of Doppler analysis section 210, peaks are detected at intervals of ΔFD for each DDM signal in the Doppler frequency domain.

[0246] Therefore, the CFAR unit 211 may divide each output of the Doppler analysis unit 210 into ranges of intervals ΔFD of the amount of Doppler shift, and perform CFAR processing (for example, called "Doppler domain compression CFAR processing") after adding power of each signal peak position that is Doppler multiplexed, as shown in the following formula (12). sc =-ΔFD / 2,…,-ΔFD / 2-1. For example, ΔFD=Ncode / N DM If f sc =Ncode / (2N DM ),…,Ncode / (2N DM )-1. The Doppler domain compression CFAR processing is described in, for example, Patent Document 6 and Patent Document 7, and a detailed description thereof will be omitted.

number

[0247] The CFAR unit 211 using the Doppler domain compression CFAR process adaptively sets a threshold value, for example, and selects f b_cf , f sc_cf , and N DM The Doppler frequency index (f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) b_cf , f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD), nfd=1,…,N DM to the coded Doppler demultiplexing unit 212.

[0248] [Example of operation of the coded Doppler demultiplexing unit 212] Next, an example of the operation of the coded Doppler demultiplexing unit 212 shown in Fig. 4 will be described. Note that, hereinafter, an example of the processing of the coded Doppler demultiplexing unit 212 in the case where Doppler domain compression CFAR processing is used in the CFAR unit 211 will be described. Fig. 14 is a flowchart showing an example of the demultiplexing operation in the coded Doppler demultiplexing unit 212.

[0249] <Step A-1> The coded Doppler demultiplexing section 212 performs coded Doppler demultiplexing processing on the Nt CDDM signals, assuming that the signals do not include any target reflected waves that are cross-polarized with respect to the polarization of the receiving antenna.

[0250] For example, the coded Doppler demultiplexing unit 212 receives f b_cf , f sc_cf , and N DM Based on the received power information at the Doppler frequency index of the Nt DDM signals, the output of Doppler analysis unit 210 is used to separate the Nt CDDM transmitted signals and determine (e.g., determine or identify) the transmitting antenna and the Doppler frequency (e.g., Doppler velocity or relative velocity).

[0251] As described above, when the encoding unit 107 of the phase rotation amount setting unit 105 uses the setting of the uniform Doppler shift amount including the setting of the maximum uniform Doppler shift amount, for example, N DM Number of coded Doppler multiplexes N CDDM (1), N CDDM (2),…, N CDDM (N DM ) to N CM At least one coded Doppler multiplex number is set to N CM Set it to a value smaller than 1 (set unevenly).

[0252] For example, the coded Doppler demultiplexing unit 212 (1) performs code demultiplexing processing to set the number of coded Doppler multiplexes to N CMThe coded Doppler demultiplexing unit 212 then detects a CDDM signal with a set number less than 1 (for example, an unused CDDM signal not used for multiplex transmission) and performs aliasing determination. (2) Based on the result of the aliasing determination, the coded Doppler demultiplexing unit 212 performs Doppler code demultiplexing processing of the CDDM signal used for multiplex transmission.

[0253] The operation of such coded Doppler demultiplexing unit 212 is similar to that of a coded Doppler demultiplexing unit in a MIMO radar using existing coded Doppler multiplex transmission, and is described in, for example, Patent Document 7, so a detailed description of the operation will be omitted.

[0254] In addition, as the setting of the uniform Doppler shift amount including the maximum uniform Doppler shift amount setting, for example, N DM Number of coded Doppler multiplexes N CDDM (1), N CDDM (2), ~, N CDDM (N DM ) to N CM At least one coded Doppler multiplex number is set to N CM When the value fd is set to a value smaller than 1 / (2Tr), the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) can be detected by the operation of the coded Doppler demultiplexing unit 212 described above (see, for example, Patent Document 7).

[0255] <Step A-2> The coded Doppler demultiplexing unit 212 judges whether or not the Nt CDDM signals have been normally detected. If the Nt CDDM signals have been normally detected, the coded Doppler demultiplexing unit 212 performs the process of step A-3, and if the signals have not been normally detected, the coded Doppler demultiplexing unit 212 performs the process of step B-1.

[0256] For example, in the process of step A-1, if a target reflected wave in which the PL1 polarization or the PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna is included, there is a possibility that the Nt CDDM signals will not be detected normally.

[0257] For example, a polarized MIMO radar is configured using two transmitting antennas of PL1 polarization and PL2 polarization, and the setting of the phase rotation amount setting unit 105 is N DM_PL1 <N DM , or N DM_PL2 <N DM If the reflected wave from the target is cross-polarized with respect to the polarization of the receiving antenna, N DM The received powers of the DDM signals at the Doppler frequency indexes differ by a predetermined value or more, or a component with a received power as small as the noise level is included. In such a case, the coded Doppler demultiplexing unit 212 DM Since fewer than 1 CDDM signal are detected, it is determined that the detection is not normal, and the process of step B-1 is carried out.

[0258] For example, for a PL1 polarization transmission antenna, the setting of the phase rotation amount setting unit 105 is N DM_PL1 =N DM When the PL2 polarized wave includes a target reflected wave that is a cross-polarized wave with respect to the polarized wave of the receiving antenna, or when the setting of the phase rotation amount setting unit 105 is N DM_PL2 =N DM If the PL1 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, N DM The received power is within a predetermined range between the received powers at the Doppler frequency indexes of the DDM signals. In this case, the unused CDDM signals not used for multiplexing are received at the time of code separation processing. CM ×N DM Since the number of CDDM signals is greater than the number of CDDM signals assumed (N −Nt), coded Doppler demultiplexing section 212 fails to detect aliasing, making it difficult to correctly detect the Nt CDDM signals. CM ×N DM If more than Nt (-Nt) are detected, it is determined that the detection is not normal, and the process of step B-1 is carried out.

[0259] <Step A-3> The coded Doppler demultiplexing unit 212 performs CDDM demultiplexing processing on the CDDM signal used for multiplex transmission based on the aliasing determination result to obtain a received signal Y z (f b_cf ,f sc_cf ,ncm,ndm) to f b_cf and f sc_cf At the same time, it outputs the result to the direction estimation unit 213.

[0260] Here, Y z (f b_cf ,f sc_cf , ndc(ndm), ndm) is the f of the Doppler analyzer 210 in the z-th antenna system processor 201. b_cf and f sc_cf , in,DOP ndm and orthogonal code ndc(ndm) For example, Y z (f b_cf ,f sc_cf , ndc(ndm), ndm) represents a signal transmitted from a transmitting antenna Tx#[ndc(ndm), ndm], reflected by a target, and received by the z-th antenna system processor 201. Note that z=1 to Na, and ncm=1 to N CM In addition, ndm=1~N DM and ndc(ndm)=1~N CDDM (ndm).

[0261] Furthermore, the coded Doppler demultiplexing unit 212 may output, for example, information on the Doppler frequency of the detected target to the direction estimating unit 213.

[0262] When condition 2 is satisfied, the coded Doppler demultiplexing unit 212 can detect the Doppler frequency of the target estimated within the range of −1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0263] <Step B-1> The coded Doppler demultiplexing unit 212 assumes a case in which the PL2 polarized wave is a cross-polarized wave with respect to the receiving antenna polarized wave and includes a target reflected wave. PL1 The CDDM separation process is performed on each CDDM signal.

[0264] For example, the coded Doppler demultiplexing unit 212 receives f b_cf , f sc_cf , and N DM Based on the received power information at the Doppler frequency indexes of the DDM signals, the output of the Doppler analysis unit 210 is used to calculate N PL1 The CDDM transmitted signals are separated and transmit antenna discrimination (eg, determination or identification) and Doppler frequency (eg, Doppler velocity or relative velocity) discrimination is performed.

[0265] Here, N DM When the received powers of the DDM signals at the Doppler frequency indexes differ by a predetermined value or more, or when the received powers of the components are as small as the noise level (N DM -N DM_PL1 ) may be included. Note that the setting of the phase rotation amount setting unit 105 may be N DM =N DM_PL1 If so, the signal does not include any component whose received power is as small as the noise level.

[0266] Therefore, the coded Doppler demultiplexing unit 212 receives, for example, N DM Among the received powers at the Doppler frequency indexes of the DDM signals, the N highest power DM_PL1 Extract DDM signals.

[0267] For example, the top N powers extracted DM_PL1 When the Doppler multiplexing interval of the DDM signals matches the Doppler multiplexing interval assigned to the PL1 polarization transmission antenna, the coded Doppler multiplexing separation unit 212 (1) performs code separation processing and extracts the coded Doppler multiplexing number N from the CDDM signals assigned to the PL1 polarization transmission antenna. CMThe coded Doppler demultiplexing unit 212 detects a CDDM signal with a set number less than 1 (for example, an unused CDDM signal not used for multiplexing of the PL1 polarization transmission antenna) and performs aliasing determination. (2) Based on the aliasing determination result, the coded Doppler demultiplexing unit 212 performs Doppler code demultiplexing processing of the CDDM signal used for multiplexing.

[0268] The operation of such coded Doppler demultiplexing unit 212 is similar to that of a coded Doppler demultiplexing unit in a MIMO radar using existing coded Doppler multiplex transmission, and is described in, for example, Patent Document 7, so a detailed description of the operation will be omitted.

[0269] In addition, by setting the CDP amount to satisfy condition 2, for example, the operation of the above-mentioned coded Doppler demultiplexing unit 212 makes it possible to detect the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) (for example, see Patent Document 7).

[0270] <Step B-2> The coded Doppler demultiplexing unit 212 demultiplexes N PL1 N PL1 The coded Doppler demultiplexing unit 212 judges whether N CDDM signals are normally detected. PL1 If the CDDM signals are detected normally, the process of step B-3 is performed, and if they are not detected normally, the process of step C-1 is performed. When the setting of the CDP amount by phase rotation amount setting section 105 satisfies condition 1, the following judgment process becomes possible.

[0271] For example, in the process of step B-1, if the PL2 polarization does not include a target reflected wave that is a cross-polarized wave with respect to the polarization of the receiving antenna, N PL1 There is a possibility that the CDDM signal will not be detected correctly.

[0272] The coded Doppler demultiplexing unit 212 extracts, for example, the N highest power components DM_PL1 DDM signals and other low power (N DM -NDM_PL1 ) DDM signals, it is determined that the signal does not include a target reflected wave in which the PL2 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and processing of step C-1 is performed (such a determination processing is possible when the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (A-2) of condition 1A).

[0273] In addition, the top N of the extracted power DM_PL1 If the Doppler multiplexing interval of this DDM signal does not match the Doppler multiplexing interval assigned to the transmitting antenna of the PL1 polarization, the coded Doppler multiplexing separation unit 212 determines that it does not contain a target reflected wave in which the PL2 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and performs processing of step C-1 (such a determination processing is possible if the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (A-1) or (A-3) of condition 1A).

[0274] For example, for a PL1 polarization transmission antenna, the setting of the phase rotation amount setting unit 105 is N DM_PL1 =N DM_PL2 In this case, if the PL1 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, N DM The received power is within a predetermined range between the received powers at the Doppler frequency indexes of the DDM signals. In such a case, when the code separation process is performed, PL1 Since a signal different from the code interval or code multiplexing number of the CDDM signal is obtained, the coded Doppler demultiplexing unit 212 fails to determine whether the signal has been aliased. PL1 In such a case, it becomes difficult to detect N CDDM signals. PL1 The detection unit 104 determines that the detection is not normal for this CDDM signal and performs processing in step C-1 (such a determination process is possible if the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (B-1) or (B-2) of condition 1B).

[0275] <Step B-3> The coded Doppler demultiplexing unit 212 extracts N PL1 The received signal YPL1 is the result of coded Doppler demultiplexing of the CDDM signal used for multiplexing transmission from the four transmitting antennas. z (f b_cf ,f sc_cf ,ncm,ndm) to f b_cf and the Doppler frequency index f sc_cf At the same time, it outputs the result to the direction estimation unit 213.

[0276] Here, YPL1 z (f b_cf ,f sc_cf , ndc(ndm), ndm) is the f of the Doppler analyzer 210 in the z-th antenna system processor 201. b_cf and f sc_cf In DOP ndm and orthogonal code ndc(ndm) This is the output of a separated CDDM signal (e.g., the CDDM separation result) using YPL1. z (f b_cf ,f sc_cf ,ndc(ndm),ndm) is the N PL1 represents a received signal transmitted from a number of transmitting antennas Tx#[ndc(ndm), ndm], reflected by a target, and received by the z-th antenna system processor 201. Note that z=1 to Na, and ndm=1 to N DM and ndc(ndm)=1~N CDDM (ndm), and N PL1 Signals other than those assigned to the transmitting antennas are output as zero.

[0277] In addition, the coded Doppler demultiplexing unit 212 may output the Doppler frequency of the detected target to the direction estimating unit 213.

[0278] When condition 2 is satisfied, the coded Doppler demultiplexing unit 212 can detect the Doppler frequency of the target estimated within the range of −1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0279] <Step C-1> The coded Doppler demultiplexing unit 212 assumes a case in which the PL1 polarized wave is a cross-polarized wave with respect to the polarized wave of the receiving antenna and includes a target reflected wave. PL2 The CDDM signals are subjected to CDDM separation processing.

[0280] For example, the coded Doppler demultiplexing unit 212 receives f b_cf , f sc_cf , and N DM Based on the received power information at the Doppler frequency indexes of the DDM signals, the output of the Doppler analysis unit 210 is used to calculate N PL2 The CDDM transmitted signals are separated and transmit antenna discrimination (eg, decision or identification) and Doppler frequency (eg, Doppler velocity or relative velocity) discrimination is performed.

[0281] Here, N DM If the received powers of the DDM signals at the Doppler frequency indexes differ by more than a certain value, or if there are components whose received power is as small as the noise level (N DM -N DM_PL2 ) may be included. Note that the setting of the phase rotation amount setting unit 105 is DM =N DM_PL2 If so, the signal does not include any component whose received power is as small as the noise level.

[0282] Therefore, the coded Doppler demultiplexing unit 212 receives, for example, N DM Among the received powers at the Doppler frequency indexes of the DDM signals, the N highest power DM_PL2 Extract DDM signals.

[0283] For example, the top N powers extracted DM_PL2 When the Doppler multiplexing interval of the DDM signals matches the Doppler multiplexing interval assigned to the PL2 polarization transmission antenna, the coded Doppler multiplexing separation unit 212 (1) performs code separation processing and extracts the coded Doppler multiplexing number N from the CDDM signals assigned to the PL2 polarization transmission antenna.CM The coded Doppler demultiplexing unit 212 detects a CDDM signal with a set number less than 1 (for example, an unused CDDM signal not used for multiplexing of the PL2 polarization transmission antenna) and performs aliasing determination. (2) Based on the result of the aliasing determination, the coded Doppler demultiplexing unit 212 performs Doppler code demultiplexing processing of the CDDM signal used for multiplexing.

[0284] The operation of such coded Doppler demultiplexing unit 212 is similar to that of a coded Doppler demultiplexing unit in a MIMO radar using existing coded Doppler multiplex transmission, and is described in, for example, Patent Document 7, so a detailed description of the operation will be omitted.

[0285] In addition, by setting the CDP amount to satisfy condition 2, for example, the operation of the above-mentioned coded Doppler demultiplexing unit 212 makes it possible to detect the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) (for example, see Patent Document 7).

[0286] <Step C-2> The coded Doppler demultiplexing unit 212 demultiplexes N PL2 N PL2 The coded Doppler demultiplexing unit 212 judges whether N CDDM signals are normally detected. PL2 If the CDDM signals are detected normally, processing of step C-3 is performed. If the signals are not detected normally, the received signal is assumed to have a large amount of noise (e.g., a low SNR) or to contain interference components, and processing of step D is performed.

[0287] The coded Doppler demultiplexing unit 212 extracts, for example, the N highest power components DM_PL2 DDM signals and other low power (N DM -N DM_PL2 ) DDM signals, it is determined that the signal does not contain a target reflected wave in which the PL1 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and processing of step D is performed.

[0288] In addition, the top N of the extracted power DM_PL2 If the Doppler multiplex interval of the DDM signals does not match the Doppler multiplex interval assigned to the transmitting antenna of the PL2 polarization, the coded Doppler demultiplexing unit 212 determines that the signal does not include a target reflected wave in which the PL1 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and performs the process of step D. In addition, the coded Doppler demultiplexing unit 212 may, for example, DM_PL2 Based on the received power of the signal obtained by performing code separation processing on the DDM signals, PL2 If they do not match, it is determined that the signal does not include a target reflected wave in which the PL1 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and the process proceeds to step D.

[0289] <Step C-3> The coded Doppler demultiplexing unit 212 extracts N PL2 Received signal YPL2 after CDDM separation processing of the CDDM signal used for multiplexed transmission of 1 transmit antenna z (f b_cf ,f sc_cf ,ncm,ndm) to f b_cf and f sc_cf At the same time, it outputs the result to the direction estimation unit 213.

[0290] Here, YPL2 z (f b_cf ,f sc_cf , ndc(ndm), ndm) is the f of the Doppler analyzer 210 in the z-th antenna system processor 201. b_cf and f sc_cf In DOP ndm and orthogonal code ndc(ndm) This is the output of a separated CDDM signal (e.g., the CDDM separation result) using YPL2. z (f b_cf ,f sc_cf ,ndc(ndm),ndm) is the N PL2represents a received signal transmitted from a number of transmitting antennas Tx#[ndc(ndm), ndm], reflected by a target, and received by the z-th antenna system processor 201. Note that z=1 to Na, and ndm=1 to N DM and ndc(ndm)=1~N CDDM (ndm), and N PL2 Signals other than those assigned to the transmitting antennas are output as zero.

[0291] In addition, the coded Doppler demultiplexing unit 212 may output the Doppler frequency of the detected target to the direction estimating unit 213.

[0292] When condition 2 is satisfied, the coded Doppler demultiplexing unit 212 can detect the Doppler frequency of the target estimated within the range of −1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0293] <Step D> If the condition of step C- 2 is not satisfied, the coded Doppler demultiplexing unit 212 determines that the received signal is a noise component or an interference component, and does not need to output the signal to the direction estimation unit 213 .

[0294] An example of the operation of the coded Doppler demultiplexing unit 212 has been described above.

[0295] In addition, f b_cf , the Doppler frequency index f sc_cf , and when there are a plurality of pieces of reception power information, the coded Doppler demultiplexing unit 212 may perform the above-mentioned CDDM demultiplexing operation a plurality of times for each of the distance index, the Doppler frequency index, and the reception power information.

[0296] [Example of operation of direction estimation unit 213] Next, an example of the operation of the direction estimator 213 shown in FIG. 4 will be described.

[0297] The direction estimation unit 213 estimates, for example, a signal (e.g., f b_cf , the received signal Y after CDDM separation processing z (f b_cf ,f sc_cf ,ndc(ndm),ndm) or YPLq z (f b_cf ,f sc_cf , ndc(ndm), ndm), where q=1 to NPL, is used to estimate the direction of the target.

[0298] The received signal Y z (f b_cf ,f sc_cf ,ndc(ndm),ndm) is the CDP amount ψ ndc(ndm), ndm Since the received signal is a signal from a transmitting antenna using (m), it can be associated with Tx#1, Tx#2, . . . , Tx#Nt. Therefore, in the following, the received signal Y z (f b_cf ,f sc_cf , ndc(ndm),ndm) CDP amount ψ ndc(ndm), ndm For (m), "YT z (f b_cf ,f sc_cf It can also be written as "(1, nt)", where nt = 1 to Nt.

[0299] Similarly, the received signal YPLq z (f b_cf ,f sc_cf , ndc(ndm),ndm) CDP amount ψ ndc(ndm), ndm For (m), "YPLT z (f b_cf ,f sc_cf ,nt)".

[0300] Hereinafter, operation example 1 and operation example 2 of the direction estimation unit 213 will be described.

[0301] <Operation Example 1 of Direction Estimation Unit 213> In the operation example 1, for example, the direction estimation unit 213 b_cf and the received signal Y after CDDM separation processing z (f b_cf ,f sc_cf , ndc(ndm), ndm), the virtual receiving array correlation vector h(f b_cf , f sc_cf ) is generated and direction estimation processing is performed.

[0302] Here, the information input from the coded Doppler demultiplexing unit 212 is the received signal Y z (f b_cf ,f sc_cf , ndc(ndm),ndm), the virtual receiving array correlation vector h(f b_cf , f sc_cf ) includes Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. The direction estimator 213 calculates the virtual receiving array correlation vector h(f b_cf , f sc_cf ) is used to estimate the direction of the reflected wave signal from the target based on the phase difference between the transmitting and receiving antennas.

[0303] The direction estimation unit 213 performs direction estimation processing for each polarized transmitting antenna, for example, by calculating a virtual receiving array correlation vector h(f b_cf , f sc_cf ) and extract the received signal corresponding to the transmitting antenna of the same polarization, and calculate the virtual receiving array correlation vector h PLq (f b_cf , f sc_cf ), where h PLq (f b_cf , f sc_cf ) is N PLq ×Na elements.

[0304] The direction estimation unit 213 estimates, for example, a virtual receiving array correlation vector h PLq (f b_cf , f sc_cf) to obtain the direction estimation evaluation function P H-PLq (θ u , f b_cf , f sc_cf ) in the azimuth direction θ u is varied within a predetermined angle range to calculate the spatial profile of the PLq polarization.

[0305] The direction estimator 213 may extract a predetermined number of maximum peaks in the calculated spatial profile for each PLq polarization in descending order, and output the azimuth direction of the maximum peak as an estimated value of the direction of arrival of the PLq polarization (for example, positioning output), where q=1 to NPL.

[0306] In addition, the direction estimation evaluation function value P H-PLq (θ u , f b_cf , f sc_cf There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0307] In addition, by using a MIMO virtual receiving antenna arrangement arranged in a rectangular grid, it is also possible to estimate the direction of arrival in the azimuth direction and the elevation angle direction. For example, the direction estimator 213 may calculate the azimuth direction and the elevation angle direction as the direction of arrival estimation value for each transmitting antenna of different polarization, and output the calculated values ​​as the positioning output. Note that the same application is possible in the operation example 2 of the direction estimator 213 described later.

[0308] By the above operation, the direction estimator 213 of the radar device 10 outputs, for example, f b_cf and the received signal Y after CDDM separation processing z (f b_cf ,f sc_cf , ndc(ndm), ndm) as a positioning output. b_cf , and the estimated Doppler frequency of the target. The same can be applied to a second operation example of the direction estimator 213 described later.

[0309] Also, fb_cf may be converted into distance information using equation (10) and output. Note that the same application is possible in operation example 2 of the direction estimation unit 213 described later.

[0310] In addition, information input from the coded Doppler demultiplexing unit 212 (for example, f b_cf , and the received signal Y after CDDM separation processing z (f b_cf ,f sc_cf , ndc(ndm), ndm)), the direction estimator 213 may calculate arrival direction estimates for them in the same manner as in the above-mentioned process and output the positioning result. Note that the same application is possible in the operation example 2 of the direction estimator 213 described later.

[0311] <Operation Example 2 of Direction Estimation Unit 213> In the second operation example, for example, the direction estimation unit 213 b_cf and the received signal YPLq after CDDM separation processing z (f b_cf ,f sc_cf , ndc(ndm), ndm), the virtual receiving array correlation vector hq(f b_cf , f sc_cf , ndc(ndm), ndm) is generated, and direction estimation processing is performed based on the received signal from the transmitting antenna of PLq polarization.

[0312] The direction estimation unit 213 estimates the received signal YPLq after the CDDM separation process. z (f b_cf ,f sc_cf , ndc(ndm), ndm) is performed. The operation in this case is different from the operation in the first operation example in that the direction estimation process of the PLq polarization corresponding to q that coincides with Y z (f b_cf ,f sc_cf ,ndc(ndm),ndm) is the received signal YPLq z (f b_cf ,f sc_cf , ndc(ndm), ndm) is replaced with the processing described above, so a detailed explanation of the operation will be omitted.

[0313] By the above operation, the direction estimator 213 of the radar device 10 outputs, for example, f b_cf , the received signal YPLq after CDDM separation processing, which is the received signal from the transmitting antenna of PLq polarization z (f b_cf ,f sc_cf , ndc(ndm), ndm) may be used to output an estimated direction of arrival value for the PLq polarization.

[0314] Operation example 1 and operation example 2 of direction estimation unit 213 have been described above.

[0315] By the above-mentioned operation, the direction estimation unit 213 can perform direction estimation processing based on the output corresponding to the separation operation of the coded Doppler demultiplexing unit 212. For example, the direction estimation unit 213 can perform direction estimation processing based on the output of the coded Doppler demultiplexing unit 212 corresponding to each of the cases where the target reflected wave does not include a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna, the target reflected wave includes a target reflected wave whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna, and the target reflected wave includes a target reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna.

[0316] Also, for example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is not included, the direction estimation unit 213 can perform direction estimation processing for each polarization included in the transmitting antenna. Also, for example, when a target reflected wave in which the PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna is included, the direction estimation unit 213 can perform direction estimation processing for the PL1 polarization transmission. Also, for example, when a target reflected wave in which the PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna is included, the direction estimation unit 213 can perform direction estimation processing for the PL2 polarization transmission.

[0317] Such an operation of the direction estimation unit 213 obtains a direction estimation process result for each transmission polarization, or a direction estimation result for some transmission polarization depending on the state of the reflected wave, and obtains a direction estimation result that depends on the transmission polarization. Since the response of the reflected wave from the target may vary depending on the transmission polarization, the radar device 10 can improve the detection performance or identification performance of the target based on the direction estimation result that depends on the transmission polarization.

[0318] An example of the operation of the direction estimator 213 has been described above.

[0319] As described above, in this embodiment, the radar device 10, in a polarized transmission MIMO radar using CDDM, assigns different CDDM signals (e.g., signals having different DDM and / or CDM patterns) between polarizations that satisfy at least condition 1 in the phase rotation amount setting unit 105. As a result, even if the reception levels of reflected waves corresponding to transmitting antennas of different polarizations differ greatly, the radar device 10 can distinguish the transmitting antennas in the coded Doppler multiplexing separation unit 212 and perform CDDM separation. Therefore, according to this embodiment, it is possible to suppress deterioration of target detection performance, erroneous estimation of Doppler frequency, or deterioration of angle measurement performance.

[0320] Furthermore, for example, by satisfying the above-mentioned conditions 1 and 2 in the allocation of CDDM signals in the phase rotation setting unit 105, in the radar device 10, even if the reception levels of reflected waves corresponding to transmitting antennas of different polarizations differ significantly, the detectable Doppler frequency range fd becomes −1 / (2Tr)≦fd<1 / (2Tr), and the Doppler frequency range can be expanded to the same range as in the case of using one transmitting antenna.

[0321] Therefore, according to this embodiment, it is possible to improve the detection performance of a polarized MIMO radar using coded Doppler multiplexing transmission.

[0322] Moreover, in this embodiment, the radar device 10 includes a receiving antenna that receives a reflected wave signal of a radar transmission signal reflected by a target using one of a plurality of polarized waves (for example, PL1 polarized wave and PL2 polarized wave). The radar device 10 performs direction estimation based on the reflected wave signal received by the receiving antenna. As a result, even if a reflected wave that is in a cross-polarized relationship with the polarization of the receiving antenna is included, the radar device 10 can identify the transmitting antenna corresponding to the DDM signal and resolve the ambiguity of the Doppler frequency. Furthermore, in this embodiment, even if the receiving antenna is an antenna with the same polarization, CDDM separation is possible, and there is no need to additionally use a different type of polarized receiving antenna in the radar receiver 200, and the number of receiving antennas can be reduced.

[0323] (Variation 1) In the above-described embodiment, as an example, an example of operation of the CFAR unit 211, the coded Doppler demultiplexing unit 212, and the direction estimation unit 213 in a case where the multiple receiving antennas of the receiving antenna unit 202 are receiving antennas of the same polarization has been described.

[0324] The multiple receiving antennas of the receiving antenna unit 202 may include receiving antennas of different polarizations. In Modification 1, an example of the operation of the CFAR unit, the coded Doppler demultiplexing unit, and the direction estimation unit in a case where the multiple receiving antennas of the receiving antenna unit 202 include receiving antennas of different polarizations will be described.

[0325] For example, when the multiple receiving antennas include receiving antennas of different polarizations, the receiving level of the target reflected wave may differ significantly for each different polarization. For this reason, for example, the radar device 10 may perform CFAR processing, Doppler separation processing, and direction estimation processing individually for the output of the Doppler analysis unit 210 corresponding to the receiving antennas of different polarizations (for example, the reflected wave signal received by each receiving antenna of each polarization). Note that the direction estimation processing may be performed using the output of the Doppler separation processing by the receiving antennas of multiple polarizations.

[0326] In the following, as an example, a case will be described in which the receiving antennas Rx#1 to Rx#Na of the receiving antenna section 202 include at least two receiving antennas with different polarizations.

[0327] For example, two different polarized waves are expressed as "RxPL1 polarized wave" and "RxPL2 polarized wave". In addition, among the Na receiving antennas, the number of receiving antennas for RxPL1 polarized wave is expressed as N RxPL1 The number of RxPL2-polarized receiving antennas is N RxPL2 Here, N RxPL1 +N RxPL2 =Na.

[0328] 15 is a block diagram showing an example of the configuration of a CFAR unit 211a, a coded Doppler demultiplexing unit 212a, and a direction estimating unit 213a of a radar receiver 200a in a radar device 10 according to the first modification. In FIG. 15, as an example, receiving antennas Rx#1 to Rx#N RxPL1 is the receiving antenna for RxPL1 polarization, and Rx#N RxPL1 +1 to Rx#Na are receiving antennas for RxPL2 polarization. Note that the relationship between the receiving antenna numbers and the polarization is not limited to the example shown in FIG.

[0329] Furthermore, as shown in FIG. 15, Doppler demultiplexing is possible using the peak detection results for each receiving antenna of the same polarization, and power addition calculations between receiving antennas of two different polarizations are not required, resulting in an effect of reducing the amount of calculations in the radar receiver 200a.

[0330] For example, among the outputs of the Na Doppler analyzers 210, the first to Nth RxPL1 The output of the Doppler analysis unit 210 corresponds to the received signal of the RxPL1 polarized wave receiving antenna, and is input to a first CFAR unit 211a-1 that performs CFAR processing on the received signal of the RxPL1 polarized wave.

[0331] Also, for example, among the outputs of the Na Doppler analyzers 210, the Rx#N RxPL1The outputs of +1 to Nath Doppler analyzers 210 correspond to the received signals of the RxPL2 polarized receiving antenna, and are input to a second CFAR unit 211a-2 that performs CFAR processing on the RxPL2 polarized received signals.

[0332] The first coded Doppler demultiplexing unit 212a-1 receives, for example, f b_cf , f sc_cf , and N DM The Doppler frequency index (f sc_cf + (nfd-ceil(N DM / 2)-1)×ΔFD) RxPL1 (f b_cf , f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) (where nfd=1~N DM ) based on the first to Nth signals that are received by the RxPL1 polarization receiving antenna. RxPL1 Using the output of the Doppler analysis unit 210, t 4, the first coded Doppler demultiplexing unit 212a-1 separates the first to Nth CDDM-transmitted signals, and discriminates (for example, referred to as judgment or identification) the transmitting antenna 109 and discriminates the Doppler frequency (for example, Doppler velocity or relative velocity). RxPL1 The difference is that it uses reception power information based on the output of the Doppler analysis unit 210, and other operations may be similar to those of the coded Doppler demultiplexing unit 212.

[0333] The second coded Doppler demultiplexing unit 212a-2 receives, for example, f b_cf , f sc_cf , and N DM The Doppler frequency index (f sc_cf +(nfd-ceil(N DM / 2)-1)×ΔFD) RxPL2 (f b_cf , f sc_cf +(nfd-ceil(NDM / 2)-1)×ΔFD) (where nfd=1~N DM ) based on the Nth signal that is the received signal of the RxPL2 polarization receiving antenna RxPL1 +1~Nth a Using the output of the Doppler analysis unit 210, t The second coded Doppler demultiplexing unit 212a-2 separates the Nth CDDM-transmitted signals, and discriminates (for example, referred to as judgment or identification) the transmitting antenna 109 and discriminates the Doppler frequency (for example, Doppler velocity or relative velocity). RxPL1 +1~Nth a The difference is that it uses reception power information based on the output of the Doppler analysis unit 210, and other operations may be similar to those of the coded Doppler demultiplexing unit 212.

[0334] Next, an example of the operation of the first direction estimation unit 213a-1 and the second direction estimation unit 213a-2 will be described. In the following, the first direction estimation unit 213a-1 and the second direction estimation unit 213a-2 will be collectively described as the "y-th direction estimation unit 213a". Here, y=1 or 2. The y-th direction estimation unit 213a performs a target direction estimation process based on, for example, a signal input from the y-th coding Doppler multiplex separation unit 212a.

[0335] Hereinafter, operation example 1 and operation example 2 of the y-direction estimation unit 213a will be described.

[0336] <Operation Example 1 of the y-direction estimation unit 213a> For example, the y-th direction estimation unit 213a estimates f b_cf and the received signal Y after CDDM separation processing z (f b_cf ,f sc_cf , ndc(ndm), ndm), the virtual receiving array correlation vector h RxPLy (f b_cf , f b_comp_cf ) is generated and direction estimation processing is performed, where y=1 or 2.

[0337] Virtual receiving array correlation vector h RxPLy (f b_cf , f b_comp_cf ) is the number of transmitting antennas Nt and the number of receiving antennas for RxPLy polarization N RxPLy and the product Nt×N RxPLy The y-th direction estimation unit 213a calculates the virtual receiving array correlation vector h RxPLy (f b_cf , f b_comp_cf ) is used to estimate the direction of the reflected wave signal from the target based on the phase difference between the transmitting and receiving antennas.

[0338] The y-th direction estimation unit 213a performs direction estimation processing for each polarized transmitting antenna, for example, by using a virtual receiving array correlation vector h RxPLy (f b_cf , f sc_cf ) and extract the received signal corresponding to the transmitting antenna of the same polarization, and calculate the virtual receiving array correlation vector h PLq, RxPLy (f b_cf , f sc_cf ), where h PLq, RxPLy (f b_cf , f sc_cf ) is N PLq ×N RxPLy is a column vector with elements.

[0339] The y-th direction estimation unit 213a estimates, for example, a virtual receiving array correlation vector h PLq, RxPLy (f b_cf , f sc_cf ) to perform direction estimation processing and output as an arrival direction estimate (for example, positioning output) by the receiving antennas of the RxPLy polarization for each PLq polarization.

[0340] Through the above operations, the y-th direction estimation unit 213a receives, as a positioning output, for example, a signal f b_cf , and the received signal Y after CDDM separation processing z (f b_cf ,f sc_cf, ndc(ndm), ndm), the y-direction estimator 213a may output an arrival direction estimation value by the y-polarized receiving antenna of RxPLy for each of the different polarized transmitting antennas in the y-direction estimator 213a. b_cf may be output.

[0341] <Operation Example 2 of the y-direction estimation unit 213a> For example, the y-th direction estimation unit 213a estimates f b_cf , and the received signal YPLq after CDDM separation processing z (f b_cf ,f sc_cf , ndc(ndm),ndm), the virtual receiving array correlation vector h PLq , RxPLy (f b_cf , f sc_cf ) and performs direction estimation processing. The y-th direction estimation unit 213a generates a received signal YPLq z (f b_cf ,f sc_cf , ndc(ndm),ndm) and the direction of the polarization (PLq polarization) corresponding to q that matches is estimated.

[0342] The y-direction estimation unit 213a estimates the received signal YPLq z (f b_cf ,f sc_cf , ndc(ndm),ndm) is performed. z (f b_cf ,f sc_cf ,ndc(ndm),ndm) is the received signal YPLq z (f b_cf ,f sc_cf , ndc(ndm), ndm) is replaced with the processing described above. Therefore, detailed explanation of the operation will be omitted.

[0343] Through the above operations, the y-th direction estimation unit 213a estimates, for example, f b_cf , and the received signal YPLq after CDDM separation processing z (f b_cf ,f sc_cf , ndc(ndm), ndm), the y-direction estimator 213a may output, as a positioning output, an estimated value of the direction of arrival by the RxPLy polarized receiving antenna for the PLq polarized transmission. b_cf may be output.

[0344] The above describes the operation example 1 and operation example 2 of the y-direction estimation unit 213a.

[0345] By the above-mentioned operation, the y-th direction estimation unit 213a can obtain the result of the direction estimation process by the receiving antenna of the RxPLy polarization for each transmitting polarization, or the direction estimation result by the receiving antenna of the RxPLy polarization for some transmitting polarization depending on the state of the reflected wave, and can obtain the direction estimation result depending on the transmitting polarization antenna and the receiving polarization antenna. Since the response of the reflected wave from the target may vary depending on the transmitting polarization and the receiving polarization, the radar device 10 can improve the detection performance or identification performance of the target based on the direction estimation result depending on the transmitting and receiving polarization.

[0346] Here, the y-th direction estimation unit 213a estimates the signal (for example, f b_cf , the received signal Y after CDDM separation processing 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 the Doppler separation index, the target direction estimation process is performed based thereon, but the present invention is not limited to this.

[0347] For example, the y-direction estimation unit 213a may perform target direction estimation processing based on the signal input from the first encoded Doppler multiplex separation unit 212a-1 and the signal input from the second encoded Doppler multiplex separation unit 212a-2.

[0348] For example, the y-direction estimation unit 213a uses the signal input from the first coded Doppler demultiplexing unit 212a-1 to calculate a virtual receiving array correlation vector h PL1, RxPL1 (f b_cf , f sc_cf In addition, the y-direction estimation unit 213a calculates a virtual receiving array correlation vector h PL2, RxPL2 (f b_cf , f sc_cf Then, the y-th direction estimation unit 213a calculates 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 ) may be used to perform target direction estimation processing.

[0349] Alternatively, for example, the y-direction estimation unit 213a uses the signal input from the first coded Doppler demultiplexing unit 212a-1 to calculate a virtual receiving array correlation vector h PL2, RxPL1 (f b_cf , f sc_cf In addition, the y-direction estimation unit 213a calculates a virtual receiving array correlation vector h PL1, RxPL2 (f b_cf , f sc_cfThen, the y-th direction estimation unit 213a calculates 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 ) may be used to perform target direction estimation processing.

[0350] (Variation 2) In the above-described embodiment, the two polarized waves, the PL1 polarized wave and the PL2 polarized wave, which are orthogonal to each other, are used as transmission polarized waves of different polarizations, but the present invention is not limited to this, and the number of polarized waves may be three or more. For example, in addition to the two polarized waves, the PL1 polarized wave and the PL2 polarized wave, which are orthogonal to each other, a transmission antenna of a polarized wave other than the PL1 polarized wave and the PL2 polarized wave may be used.

[0351] For example, the radar device 10 (eg, a polarized MIMO radar) may use Nt transmitting antennas including transmitting antennas of three or more different polarized waves, including two polarized waves that are orthogonal to each other.

[0352] Hereinafter, the first polarization will be referred to as "PL1 polarization", and the second polarization will be referred to as "PL2 polarization". The qth polarization will be referred to as "PLq polarization". In addition, the combination of different polarizations that are orthogonal to each other may be, for example, PL1 polarization and PL2 polarization, and right-handed circular polarization and left-handed circular polarization, horizontal polarization and vertical polarization, or right-diagonal 45° polarization and left-diagonal 45° polarization.

[0353] In addition, the number of transmitting antennas N t ≧3. For example, the Doppler multiplex number N DM ≧2, code multiplex number N CM ≧2. For example, Nt <N DM ×N CM In addition, the number of transmitting antennas for PLq polarization is set to "N PLq " where PLq is the number of polarized antennas, N PLq ≧1, and N PL1 +N PL2 +~+N PL_NPL =N t, q = 1 to NPL. For example, the transmitting antenna includes N PL1 PL1 polarized antennas and N PL2 PL2 polarized antennas, and N PL1 +N PL2 <Nt. Also, the Doppler multiplicity assigned to the transmitting antenna of PLq polarization is denoted as "N DM_PLq ". Here, N DM_PLq ≤N DM .

[0354] The radar device 10 performs CDDM transmission using, for example, Nt transmitting antennas.

[0355] Also, the radar device 10 performs simultaneous multiplex transmission from Nt transmitting antennas using CDDM transmission that satisfies the following condition 1a and condition 2a for Nt transmitting antennas including transmitting antennas of PL1 polarization and PL2 polarization that are cross-polarized with each other and transmitting antennas of a polarization different from PL1 polarization and PL2 polarization.

[0356] Condition 1a and condition 2a are conditions in the case where, for example, in addition to two polarizations of PL1 polarization and PL2 polarization that are in an orthogonal polarization relationship, there are transmitting antennas of other polarizations different from PL1 polarization and PL2 polarization. For example, when there are no transmitting antennas of other different polarizations in addition to the transmitting antennas of the two polarizations of PL1 polarization and PL2 polarization that are in an orthogonal polarization relationship, condition 1a and condition 2a are conditions equivalent to condition 1 and condition 2.

[0357] For example, the reflected waves corresponding to the radar transmission signals from the transmitting antennas of the PL1 polarization and the PL2 polarization, which are in an orthogonal polarization relationship, are in a cross-polarized relationship with respect to the receiving antenna unit 202, and therefore the reception levels of the received signals may differ significantly. On the other hand, among the Nt transmitting antennas, transmitting antennas of other polarizations than the PL1 polarization and PL2 polarization antennas are not in an orthogonal polarization relationship with the PL1 polarization and the PL2 polarization. For this reason, the reflected waves corresponding to the radar transmission signals from the transmitting antennas of other polarizations are unlikely to differ significantly in reception level from the reception levels of the received signals corresponding to the transmitting antennas of the PL1 polarization and the PL2 polarization.

[0358] Therefore, for example, in condition 1a, instead of the "PL1 polarized wave transmitting antenna" in condition 1, a "polarized wave transmitting antenna other than PL2 polarized wave (e.g., (Nt-N PL2 Similarly, in condition 1a, instead of the "PL2 polarized transmitting antenna" in condition 1, "polarized transmitting antennas other than PL1 polarized (for example, (Nt-N PL1 ) transmit antennas).

[0359] Also, for example, in condition 2a, instead of the "same polarized transmitting antenna" in condition 2, the condition "each of the polarized transmitting antennas excluding the PL2 polarized antenna, and each of the polarized transmitting antennas excluding the PL1 polarized antenna" may be applied.

[0360] For example, conditions 1a and 2a may be defined as follows:

[0361] <Condition 1a> For example, the phase rotation amount setting unit 105 sets a CDP amount ψ that satisfies different DDM pattern conditions (e.g., Doppler shift amount allocation pattern), different CDM pattern conditions (e.g., different code multiplexing numbers between DDM signals), or different patterns of Doppler multiplexing and code multiplexing, for each of the polarized transmission antennas excluding the PL2 polarized wave and the polarized transmission antennas excluding the PL1 polarized wave. ndc(ndm), ndm Set (m).

[0362] <Condition 2a> The signals transmitted from the polarized transmitting antennas other than the PL2 polarized antenna and the polarized transmitting antennas other than the PL1 polarized antenna are multiplexed by a code multiplexing number that is uneven between the DDM signals, and the code multiplexing number is from 1 to N. CM Any value in the range below -1, inclusive.

[0363] The radar device 10 provides the following effects by imparting a CDP amount to the transmitting antenna that satisfies the above condition 1a.

[0364] For example, the Doppler frequency of the received signal is subject to the Doppler frequency of the unknown target in addition to the coded Doppler phase rotation at the time of transmission as described above. Therefore, there is a possibility that the Doppler frequency of each DDM signal changes in the positive or negative direction while maintaining the interval between them. For example, by satisfying 1A of condition 1a (e.g., at least one of A-1, A-2, and A-3), the radar device 10 can distinguish between the case where the CDDM signal assigned to the transmitting antenna of PL1 polarization is not received and the case where the CDDM signal assigned to the transmitting antenna of PL2 polarization is not received, because the interval between the DDM signals or the Doppler multiplex number differs.

[0365] Furthermore, for example, by satisfying condition 1B of 1a (for example, at least one of B-1 or B-2), the radar device 10 is able to distinguish between a case where a CDDM signal assigned to a transmitting antenna of PL1 polarization is not received and a case where a CDDM signal assigned to a transmitting antenna of PL2 polarization is not received, because the code interval or the code multiplexing number at which the reception level is high after code separation of each DDM signal differs.

[0366] Therefore, by setting the CDP amount by the phase rotation amount setting unit 105 so as to satisfy condition 1a, even if the reception levels of the reception signals corresponding to the transmitting antennas of different polarizations differ greatly, the radar device 10 can separate the CDDM signals and prevent deterioration of the positioning performance and radar detection performance.

[0367] Furthermore, by setting the CDP amount by the phase rotation amount setting unit 105 so as to satisfy condition 2a in addition to condition 1a, the Doppler frequency range detectable by the radar device 10 becomes the range of -1 / (2Tr)≦fd<1 / (2Tr), which can be expanded to the same range as the Doppler detection range in the case of one transmitting antenna.

[0368] An example of setting the CDP amount in phase rotation amount setting section 105 will be described below.

[0369] <Setting example 5> Figure 16 shows the number of transmit antennas, Nt=6, N PL1 =2, N PL2 =2, N PL3 13 shows an example of setting the CDP amount in phase rotation amount setting section 105 when .times. ...

[0370] In FIG. 16, black circles indicate the allocation of CDDM signals to the transmitting antennas (Tx#1 and Tx#2) of PL1 polarization, white circles indicate the allocation of CDDM signals to the transmitting antennas (Tx#3 and Tx#4) of PL2 polarization, and shaded circles indicate the allocation of CDDM signals to the transmitting antennas (Tx#5 and Tx#6) of PL3 polarization (e.g., vertical (V) polarization). For example, the PL1 polarization and the PL2 polarization are orthogonal to each other. For example, the PL1 polarization may be LC polarization, and the PL2 polarization may be RC polarization. Furthermore, the PL3 polarization may be a polarization (e.g., vertical (V) polarization) that is not orthogonal to the PL1 polarization and the PL2 polarization.

[0371] In addition, in FIG. 16, the Doppler multiplexing number N DM= 4, and the Doppler shift setting unit 106 may set the four DOP1 to DOP4 using, for example, the maximum equal interval Doppler shift amount setting shown in formula (5). In Fig. 16, the phase rotation amount φ1 = 0 for adding DOP1 = 0, the phase rotation amount φ2 = π / 2 for adding DOP2 = Δfd, the phase rotation amount φ3 = π for adding DOP3 = -2Δfd, and the phase rotation amount φ4 = 3π / 2 for adding DOP4 = -Δfd (φ4 = -π / 2 may also be used). As shown in Fig. 16, the intervals (Doppler multiplex intervals) Δfd between DDM signals are equal, and Δfd = 1 / (8Tr).

[0372] In addition, in FIG. 16, the number of code multiplexes N CM = 2, and the encoding unit 107 uses, for example, Code1 = {1, 1} and Code2 = {1, -1}, which are orthogonal code sequences with a code length Loc = 2.

[0373] In FIG. 16, the number of transmitting antennas is Nt=6, and the number of Doppler multiplexing is N DM =4, code multiplex number N CM = 2, and Nt <N DM ×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N CDDM (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0374] As shown in FIG. 16, in the encoding unit 107, the number of coded Doppler multiplexes for the DDM signals using the four DOP1 to DOP4 input from the Doppler shift setting unit 106 is N CDDM (1)=2, N CDDM (2)=1, N CDDM (3)=2, N CDDM (4)=1. In this way, phase rotation amount setting section 105 sets the coded Doppler multiplexing numbers for the DDM signals non-uniformly.

[0375] In FIG. 16, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DMOf the Doppler multiplexed signals of =4, for example, Doppler multiplexed signals using Doppler shift amounts DOP2 and DOP3 are assigned (N DM_PL1 =2), for Tx#3 and Tx#4 of PL2 polarization, Doppler multiplexing number N DM Of the Doppler multiplexed signals of =4, for example, Doppler multiplexed signals using Doppler shift amounts DOP3 and DOP4 are assigned (N DM_PL2 =2), and for Tx#5 and Tx#6 of PL3 polarization, the Doppler multiplex number N DM Of the Doppler multiplexed signals of =4, for example, a Doppler multiplexed signal using a Doppler shift amount DOP1 is assigned (N DM_PL2 =1).

[0376] For example, the phase rotation amount setting unit 105 sets the CDP amount ψ for each of Tx#1 and Tx#2 of the PL1 polarization. 2, 2 (m), ψ 1, 3 (m) for each of Tx#3 and Tx#4 of PL2 polarization, and 2, 3 (m), ψ 2, 4 (m), and for each of Tx#5 and Tx#6 of the PL3 polarization, the CDP amount ψ 1, 1 (m), ψ 2, 1 Set (m).

[0377] For example, in FIG. 16, the Doppler multiplex number assigned by the Doppler shift setting unit 106 to the transmitting antennas excluding the PL2 polarization transmitting antenna (the transmitting antennas for PL1 polarization and PL3 polarization) is 3, and the Doppler multiplex number assigned by the Doppler shift setting unit 106 to the transmitting antennas excluding the PL1 polarization transmitting antenna (the transmitting antennas for PL2 polarization and PL3 polarization) is 3, which is the same.

[0378] In addition, the Doppler shift intervals of the DDM signals assigned to the transmitting antennas other than the transmitting antenna of PL2 polarization are Δfd(1,2) = Δfd, Δfd(2,3) = Δfd, and Δfd(3,1) = 2Δfd, and the Doppler shift intervals of the DDM signals assigned to the transmitting antennas other than the transmitting antenna of PL1 polarization are Δfd(1,3) = 2Δfd, Δfd(3,4) = Δfd, and Δfd(4,1) = Δfd, which are cyclically consistent and identical, and therefore do not match the different DDM pattern conditions of 1A in condition 1a.

[0379] For DOP1 to DOP4, the code index assigned to the transmitting antennas (PL1 polarized and PL3 polarized transmitting antennas) excluding the PL2 polarized transmitting antenna is denoted as "CiNoPL2". In the case of Fig. 16, CiNoPL2 = (2, 1, 1, *). For DOP1 to DOP4, the code index assigned to the transmitting antennas (PL2 polarized and PL3 polarized transmitting antennas) excluding the PL1 polarized transmitting antenna is denoted as "CiNoPL1". In the case of Fig. 16, CiNoPL1 = (2, *, 1, 1).

[0380] Moreover, for DOP1 to DOP4, the code multiplex number assigned to the transmitting antennas (PL1 polarized wave and PL3 polarized wave transmitting antennas) excluding the PL2 polarized wave transmitting antenna is denoted as "NcNoPL2". In the case of Fig. 16, NcNoPL2 = (2, 1, 1, 0). Moreover, for DOP1 to DOP4, the code multiplex number assigned to the transmitting antennas (PL2 polarized wave and PL3 polarized wave transmitting antennas) excluding the PL1 polarized wave transmitting antenna is denoted as "NcNoPL1". In the case of Fig. 16, NcNoPL1 = (2, 0, 1, 1).

[0381] In this way, for transmitting antennas other than the PL2 polarization transmitting antenna and transmitting antennas other than the PL1 polarization transmitting antenna, the code indexes assigned to each DDM signal are CiNoPL2=(2,1,1,*) and CiNoPL1=(2,*,1,1), which results in a cyclic mismatch and different code index intervals, thereby satisfying B-1 of condition 1a.

[0382] In addition, for transmitting antennas other than the PL2 polarization transmitting antenna and transmitting antennas other than the PL1 polarization transmitting antenna, the code multiplexing numbers assigned to each DDM signal are NcNoPL2=(2,1,1,0), NcNoPL1=(2,0,1,1), which results in a cyclic mismatch and satisfies B-2 of condition 1a.

[0383] In addition, the Doppler frequency of the target is -1 / (2Tr)≦f dtg <-1 / (4Tr) or 1 / (4Tr)≦f dtg If <1 / (2Tr), the Doppler analysis unit 210 observes the aliased Doppler frequency. In this case, the code index is CiNoPL2 alias =(1,2,2,*), CiNoPL1 alias = (1, *, 2, 2), which is different (cyclic mismatch). Therefore, in the example of FIG. 16, 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 interval is different. Therefore, condition 1B of condition 1a is satisfied, and a different CDM pattern condition is met.

[0384] From the above, the setting of the CDP amount shown in FIG. 16 is a setting example that satisfies condition 1a.

[0385] In addition, in FIG. 16, the code multiplexing number assigned to each DDM signal in the transmitting antennas other than the PL2 polarization transmitting antenna is NcNoPL2=(2,1,1,0), and the code multiplexing number assigned to each DDM signal in the transmitting antennas other than the PL1 polarization transmitting antenna is NcNoPL1=(2,0,1,1). In both cases, the DDM signals are multiplexed and transmitted with code multiplexing numbers that are uneven between the DDM signals, and the code multiplexing number ranges from 1 to N. CM Included in the range of -1 or less.

[0386] Therefore, in the example of FIG. 16, the signals transmitted from each of the transmitting antennas other than the PL2 polarization transmitting antenna and the PL1 polarization transmitting antenna are multiplexed and transmitted with a code multiplexing number that is uneven between the DDM signals, and the code multiplexing number ranges from 1 to N.CM This is within the range of -1 or less. Therefore, the setting of the CDP amount shown in Fig. 16 is an example of a setting that satisfies condition 2a.

[0387] When the CDP amount is set as shown in Fig. 16 and the target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is not included, the radar device 10 receives the reception signals corresponding to the PL1 polarization transmitting antenna (Tx#1 and Tx#2), the PL2 polarization transmitting antenna (Tx#3 and Tx#4), and the PL3 polarization transmitting antenna (Tx#5 and Tx#6) at approximately the same level or within a range of several dB to 6 dB. Here, in Fig. 16, the signals transmitted from Nt (=6) Tx#1 to Tx#6 consisting of the PL1 polarization transmitting antenna, the PL2 polarization transmitting antenna, and the PL3 polarization transmitting antenna are multiplexed and transmitted using the CDP amount that makes the coded Doppler multiplexing number for each DDM signal non-uniform. Therefore, the radar device 10 can separate the coded Doppler multiplexed signal based on the existing separation operation of the coded Doppler multiplexed signal.

[0388] In addition, in the CDP amount setting shown in FIG. 16, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives different CDDM signals (e.g., CDDM signals that satisfy 1B of condition 1a) depending on whether the target reflected wave includes a cross-polarized PL2 polarization as shown in FIG. 17(a) or a cross-polarized PL1 polarization as shown in FIG. 17(b).

[0389] In this way, for example, when a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna is included, the radar device 10 receives a reflected wave signal containing Doppler frequency components with different patterns in a case where the reception level of the received signal corresponding to the transmitting antenna of PL2 polarization decreases as shown in (a) of Figure 17 (equivalent to, for example, the case where a reflected wave corresponding to a transmitting antenna other than the transmitting antenna of PL2 polarization is received) and a case where the reception level of the received signal corresponding to the transmitting antenna of PL1 polarization decreases as shown in (b) of Figure 17 (equivalent to, for example, the case where a reflected wave corresponding to a transmitting antenna other than the transmitting antenna of PL1 polarization is received).

[0390] This enables the radar device 10 to determine, for example, based on the detected Doppler frequency peak, in the coded Doppler demultiplexing unit 212 whether a decrease in the reception level of the reception signal corresponding to the transmitting antenna of PL1 polarization has occurred or a decrease in the reception level of the reception signal corresponding to the transmitting antenna of PL2 polarization has occurred.

[0391] For example, the DDM signal of the polarization other than PL2 polarization is DM The DDM signals are multiplexed with unequal code multiplexing numbers (the code multiplexing number ranges from 1 to N CM (Inclusive of the range of −1). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal corresponds to a transmission signal transmitted by a polarized transmitting antenna other than the PL2 polarization transmitting antenna, the radar device 10 can separate the coded Doppler multiplexed signal by using an existing coding Doppler multiplexed signal separation operation.

[0392] Similarly, for example, the DDM signals of polarizations other than PL1 polarization are DM The DDM signals are multiplexed with unequal code multiplexing numbers (the code multiplexing number ranges from 1 to N CM (Inclusive of the range of −1). Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal corresponds to a transmission signal transmitted by a polarized transmitting antenna other than the PL1 polarization transmitting antenna, the radar device 10 can separate the coded Doppler multiplexed signal by using an existing coding Doppler multiplexed signal separation operation.

[0393] By operating the coded Doppler multiplexing separation unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd < 1 / (2Tr) and obtain an output that associates a transmitting antenna with each DDM signal.

[0394] An example of setting the CDP amount in phase rotation amount setting section 105 has been described above.

[0395] [Example of operation of the coded Doppler demultiplexing unit 212] For example, when using a transmission antenna of another polarization (e.g., PL3 polarization) different from the PL1 polarization and the PL2 polarization in addition to the two polarizations of orthogonal polarization, the DDM signal to which the CDP amount set in the above-mentioned phase rotation amount setting unit 105 is added can be separated by the following operation of the coded Doppler demultiplexing unit 212. The following describes the operation of the coded Doppler demultiplexing unit 212 according to the second modification that differs from the above-mentioned embodiment.

[0396] In the second modification, among the operations of separating CDDM signals in coded Doppler demultiplexing section 212 shown in FIG. 14, the operations of steps B and C differ from those of the above-described embodiment as follows.

[0397] <Step B-1> In the demultiplexing operation of the CDDM signal in the coded Doppler demultiplexing unit 212 shown in FIG. PL1 In the second modification, the CDDM separation process is performed on the PL1 polarization. PL2 ) of the polarized transmitting antennas excluding the PL2 polarized wave, the CDDM separation process is performed. Other than that, the operation is similar, so the explanation of the operation is omitted.

[0398] <Step B-2> The coded Doppler demultiplexing unit 212 is configured to transmit the PL2 polarized wave except for the antenna (Nt-N PL2 ) transmit antennas (Nt-N PL2 The coded Doppler multiplexing separation unit 212 determines whether the (Nt-N PL2 ) coded Doppler multiplexed signals are normally detected, the process of step B-3 is carried out, and if they are not normally detected, the process of step C-1 is carried out.

[0399] For example, in the process of step B-1, if the PL2 polarization does not include a target reflected wave that is a cross-polarized wave with respect to the polarization of the receiving antenna, (Nt-N PL2 ) coded Doppler multiplex signals may not be detected correctly.

[0400] The coded Doppler demultiplexing unit 212 extracts, for example, the N highest power components DM_NotPL2 DDM signals and other low power (N DM -N DM_NotPL2 ) DDM signals, it is determined that the PL2 polarization does not include a target reflected wave that is a cross-polarized wave with respect to the polarization of the receiving antenna, and the process of step C-1 is performed (such a determination process is possible when the setting of the CDP amount by the phase rotation amount setting unit 105 satisfies (A-2) of condition 1a). DM_NotPL2 is the number of Doppler multiplexed signals to be assigned to the transmitting antennas excluding the PL2 polarization transmitting antenna. For example, N DM_NotPL2 is N for transmitting antennas other than the PL2 polarization transmitting antenna. DM This is the number of Doppler multiplexed signals such that the code multiplexing number assigned to the Doppler multiplexed signals is 1 or more. For example, in the setting example of FIG. 16, NcNoPL2=(2,1,1,0), and N DM_NotPL2 =3.

[0401] In addition, the top N of the extracted power DM_NotPL2 If the Doppler multiplexing interval of this DDM signal does not match the Doppler multiplexing interval assigned to the polarized transmitting antenna excluding the PL2 polarization, the coded Doppler multiplexing separation unit 212 determines that the signal does not include a target reflected wave in which the PL2 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and performs processing of step C-1 (such a determination processing is possible if the CDP amount setting by the phase rotation amount setting unit 105 satisfies (A-1) or (A-3) of condition 1a).

[0402] Also, for example, excluding the PL2 polarization transmitting antenna (Nt-N PL2 ) transmitting antennas, the phase rotation amount setting unit 105 is set to NDM_NotPL1 =N DM_NotPL2 In this case, if the PL1 polarization is a cross-polarized wave 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), the received power is within a predetermined range. In such a case, when the code separation process is performed, the assumed N DM_NotPL2 Since a signal different from the code interval or code multiplexing number of the CDDM signal is obtained, the coded Doppler demultiplexing unit 212 fails to determine whether the signal has been aliased. DM_NotPL2 In this case, it becomes difficult to correctly detect N CDDM signals. DM_NotPL2 It is determined that this is not a normal detection of the CDDM signal, and processing of step C-1 is performed (such determination processing is possible when the CDP amount setting by phase rotation amount setting section 105 satisfies (B-1) or (B-2) of condition 1a).

[0403] <Step B-3> Based on the processing result of step B-2, the coded Doppler demultiplexing unit 212 excludes the PL2 polarization transmitting antenna (Nt-N PL2 ) The received signal YPL1 after CDDM separation processing of the CDDM signal used for multiplexing transmission from the transmit antennas z (f b_cf ,f sc_cf ,ncm,ndm) to f b_cf and f sc_cf At the same time, it outputs the result to the direction estimation unit 213.

[0404] Here, YPL1 z (f b_cf ,f sc_cf , ndc(ndm), ndm) is the f of the Doppler analyzer 210 in the z-th antenna system processor 201. b_cf and f sc_cf In DOPndm and orthogonal code ndc(ndm) This is the output of a separated CDDM signal (e.g., the CDDM separation result) using YPL1. z (f b_cf ,f sc_cf ,ndc(ndm),ndm) excludes the PL2 polarization transmitting antenna (Nt-N PL2 ) Tx#[ndc(ndm), ndm], reflected by a target, and received by the z-th antenna system processor 201. Note that z=1 to Na, and ndm=1 to N DM and ndc(ndm)=1~N CDDM (ndm), and N PL2 The signals assigned to the transmit antennas are output as zeros.

[0405] <Step C-1> The coded Doppler demultiplexing unit 212 assumes that the PL1 polarized wave includes a target reflected wave that is a cross-polarized wave with respect to the polarized wave of the receiving antenna, and calculates (Nt-N PL1 ) of the CDDM signals of the polarized transmitting antennas excluding the PL1 polarized waves. In the CDDM signal demultiplexing operation in the coded Doppler demultiplexing unit 212 shown in FIG. PL2 In the second modification, the CDDM separation process is performed on the PL2 polarizations. PL1 ) of the polarized transmitting antennas excluding the PL2 polarized wave, the CDDM separation process is performed. Other than that, the operation is similar, so the explanation of the operation is omitted.

[0406] <Step C-2> The coded Doppler demultiplexing unit 212 is configured to transmit the PL1 polarized wave except for the transmitting antenna (Nt-N PL1 ) transmit antennas (Nt-N PL1 The coded Doppler demultiplexing unit 212 determines whether (Nt-N PL1) CDDM signals are detected normally, processing in step C-3 is performed; if they are not detected normally, the received signal is deemed to have a large amount of noise (e.g., a low SNR) or to contain interference components, and processing in step D is performed.

[0407] The coded Doppler demultiplexing unit 212 extracts, for example, the N highest power components DM_NotPL1 DDM signals and other low power (N DM -N DM_NotPL1 ) DDM signals, it is determined that the PL1 polarization does not include a target reflected wave that is a cross-polarized wave with respect to the polarization of the receiving antenna, and the process of step D is performed. DM_NotPL1 is the number of Doppler multiplexed signals to which coded Doppler multiplexed signals are assigned to the transmitting antennas excluding the transmitting antenna of the PL1 polarization. For example, N DM_NotPL1 is N for transmitting antennas other than the PL1 polarization transmitting antenna. DM This is the number of Doppler multiplexed signals such that the code multiplexing number assigned to the Doppler multiplexed signals is 1 or more. For example, in the setting example of FIG. 16, NcNoPL1=(2,0,1,1), and N DM_NotPL1 =3.

[0408] In addition, the top N of the extracted power DM_NotPL1 If the Doppler multiplex interval of the DDM signals does not match the Doppler multiplex interval assigned to the polarized transmission antenna excluding the PL1 polarization, the coded Doppler demultiplexing unit 212 determines that the signal does not include a target reflected wave in which the PL1 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and performs the process of step D. In addition, the coded Doppler demultiplexing unit 212 may, for example, DM_NotPL1 The assumption is based on the received power of the signal obtained by performing code separation processing on the DDM signals (Nt-N PL1 If they do not match, coded Doppler demultiplexing section 212 determines that the signal does not include a target reflected wave in which the PL1 polarization is a cross-polarized wave with respect to the polarization of the receiving antenna, and performs processing in step D.

[0409] <Step C-3> Based on the processing result of step C-2, the coded Doppler demultiplexing unit 212 excludes the PL1 polarization transmitting antenna (Nt-N PL1 ) The received signal YPL2 after CDDM separation processing of the CDDM signal used for multiplexing transmission from the transmit antennas z (f b_cf ,f sc_cf ,ncm,ndm) to f b_cf and f sc_cf At the same time, it outputs the result to the direction estimation unit 213.

[0410] Here, YPL2 z (f b_cf ,f sc_cf , ndc(ndm), ndm) is the f of the Doppler analysis unit 210 in the z-th antenna system processing unit 201 b_cf and f sc_cf In DOP ndm and orthogonal code ndc(ndm) This is the output of a separated CDDM signal (e.g., the CDDM separation result) using YPL2. z (f b_cf ,f sc_cf ,ndc(ndm),ndm) excludes the PL1 polarization transmitting antenna (Nt-N PL1 ) Tx#[ndc(ndm), ndm], reflected by a target, and received by the z-th antenna system processor 201. Note that z=1 to Na, and ndm=1 to N DM and ndc(ndm)=1~N CDDM (ndm), and N corresponding to polarization PL1 PL1 The signals assigned to the transmit antennas are output as zeros.

[0411] In addition, the coded Doppler demultiplexing unit 212 may output the Doppler frequency of the detected target to the direction estimating unit 213.

[0412] When condition 2a is satisfied, the coded Doppler demultiplexing unit 212 can detect the Doppler frequency of the target estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0413] An example of the operation of the coded Doppler demultiplexing unit 212 has been described above.

[0414] [Example of operation of direction estimation unit 213] The direction estimating section 213 may perform direction estimation processing based on the output corresponding to the demultiplexing operation of the coded Doppler demultiplexing section 212, as in the above-described embodiment.

[0415] For example, the direction estimation unit 213 can perform direction estimation processing based on the output of the coded Doppler multiplex separation unit 212 corresponding to each of the following cases: when the target reflected wave does not include a target reflected wave that is cross-polarized with respect to the polarization of the receiving antenna, when the target reflected wave includes a target reflected wave whose PL2 polarization is cross-polarized with respect to the polarization of the receiving antenna, and when the target reflected wave includes a target reflected wave whose PL1 polarization is cross-polarized with respect to the polarization of the receiving antenna.

[0416] Such an operation of the direction estimation unit 213 obtains a direction estimation process result for each transmission polarization, or a direction estimation result for some transmission polarization depending on the state of the reflected wave, and obtains a direction estimation result that depends on the transmission polarization. Since the response of the reflected wave from the target may vary depending on the transmission polarization, the radar device 10 can improve the detection performance or identification performance of the target based on the direction estimation result that depends on the transmission polarization.

[0417] The second modification has been described above.

[0418] The embodiments of the present disclosure have been described above.

[0419] [Other embodiments] (1) In the above-described embodiment, in a polarized MIMO radar using CDDM transmission, in order to expand the detectable Doppler frequency range to ±1 / (2Tr) range for Nt transmitting antennas including different polarized transmitting antennas, the code multiplexing number between DDM signals is set unevenly, and CDDM transmission is performed from multiple transmitting antennas. In the above-described embodiment, a method for improving the detection performance of a polarized MIMO radar by applying CDDM transmission that satisfies conditions 1 and 2 has been described. For example, when the moving speed of an assumed target is relatively slow, or when the relative speed between the radar device and the target is limited to a narrow range, the above-described preconditions do not need to be applied.

[0420] For example, the encoding unit 107 uses a uniform Doppler shift amount setting (for example, equation (6)) that is narrower than the maximum uniform Doppler shift amount setting to determine the number of coded Doppler multiplexes N CDDM (1) , N CDDM (2),~,N CDDM (N DM ) for 1 to N CM For example, the encoding unit 107 may set the code number N CM Therefore, DOP ndm In multiple combinations of and orthogonal code sequences, DOP ndm The number of multiplexes (coded Doppler multiplexes) corresponding to each orthogonal code sequence is N. CDDM (ndm) may be the same. For example, the encoding unit 107 may uniformly set the number of coded Doppler multiplexing for the DDM signal. With such a setting, when the DDM signal is non-uniformly Doppler multiplexed, for example, the aliasing determination in Patent Document 8 can be applied, and the radar device 10 can individually separate and receive signals transmitted by CDDM from multiple transmitting antennas over a Doppler range of ±1 / (2×Loc×Tr). By applying such a CDDM transmission setting and further applying CDDM transmission that satisfies Condition 1, the effect of Condition 1 described in the first embodiment can be obtained, and the detection performance of the polarized MIMO radar can be improved.

[0421] Alternatively, the encoding unit 107 may use, for example, the maximum uniform Doppler shift amount setting to determine the number of encoded Doppler multiplexes N CDDM (1), N CDDM (2),~,N CDDM (N DM ) for 1 to N CM For example, the encoding unit 107 may set the code number N CM In this case, DOP ndm The number of combinations of the orthogonal code sequence and the number of transmitting antennas may be the same as Nt (for example, N DM ×N CM =Nt). For example, the encoding unit 107 may set the number of coded Doppler multiplexes for the DDM signals to be uniform. In this case, aliasing determination processing is not applied in the reception processing of the radar device 10. In addition, the radar device 10 may set, for example, ±1 / (2Loc×N DM ×Tr), signals transmitted via CDDM from multiple transmitting antennas 109 can be individually separated and received. By applying such CDDM transmission settings and further applying CDDM transmission that satisfies condition 1, the effect of condition 1 described in the first embodiment can be obtained, and the detection performance of the polarized MIMO radar can be improved.

[0422] (2) In the embodiment of the present disclosure, code-multiplexed transmission in the embodiment of the present disclosure may be performed using only some of the Nt transmitting antennas included in the radar device 10 rather than using all of them.

[0423] Furthermore, when the code multiplexing transmission in the above-described embodiment is applied using some of the Nt transmitting antennas of the radar device 10, the radar device 10 may set (or change) at least one of the combination of transmitting antennas used for code Doppler multiplexing and the number of multiplexing transmissions in a time-division manner for transmission. In this case, for example, the radar device 10 may switch the combination of transmitting antennas in a time-division manner for each transmission period or each code transmission period (for example, a period corresponding to the code length of the code sequence). Alternatively, for example, the radar device 10 may switch the combination of transmitting antennas or the number of transmitting antennas to be multiplexed for each measurement period (for each Nc number of radar transmission signal transmissions). Even when such an operation is applied, the effects of the above-described embodiment can be obtained in an equivalent manner.

[0424] Furthermore, when applying the code multiplexing transmission in the above-mentioned embodiment by using some but not all of the Nt transmitting antennas provided in the radar device 10, the radar device 10 may set (for example, change) the combination of transmitting antennas used for code Doppler multiplexing in a time division manner and transmit using different chirp signals. For example, the radar device 10 may transmit using different chirp signals by changing at least one of the transmission band, frequency sweep time, and center frequency of the chirp signal, or by combining a plurality of these parameters.

[0425] (3) In a radar device according to an embodiment of the present disclosure, the radar transmitter and the radar receiver may be disposed separately in physically separate locations. Also, in a radar receiver according to an embodiment of the present disclosure, the direction estimator and other components may be disposed separately in physically separate locations.

[0426] (4) The number of transmitting antennas Nt, the number of receiving antennas Na, and the number of Doppler multiplexing N DM , PLq polarized wave transmitting antenna number N PLq , number of polarizations, amount of Doppler shift, Doppler shift interval, number of code multiplexes N CMThe numerical values ​​of parameters such as code interval (code index) are merely examples and are not limited to these values. In addition, for example, some of the transmitting antennas equipped in the radar device may be used as the number of transmitting antennas Nt, and some of the receiving antennas equipped in the radar device may be used as the number of receiving antennas Na.

[0427] Although not shown, the radar device according to an embodiment of the present disclosure includes, for example, a central processing unit (CPU), a storage medium such as a read only memory (ROM) storing a control program, and a working memory such as a random access memory (RAM). In this case, the functions of each of the above-mentioned units are realized by the CPU executing the control program. However, the hardware configuration of the radar device is not limited to this example. For example, each functional unit of the radar device may be realized as an integrated circuit (IC). Each functional unit may be individually implemented as a single chip, or may be implemented as a single chip that includes some or all of the functional units.

[0428] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or amended examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure. In addition, the components in the above embodiments may be arbitrarily combined within the scope of the disclosure.

[0429] In addition, the notation "... part" in the above-mentioned embodiments may be replaced with other notations such as "... circuitry", "... assembly", "... device", "... unit", or "... module".

[0430] In each of the above embodiments, the present disclosure has been described as an example configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

[0431] Moreover, each functional block used in the description of each of the above embodiments is typically realized as an LSI, which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiments and may have input terminals and output terminals. These may be individually integrated into one chip, or may be integrated into one chip that includes some or all of them. Here, the term LSI is used, but depending on the degree of integration, it may also be called an IC, a system LSI, a super LSI, or an ultra LSI.

[0432] The method of integration is not limited to LSI, but may be realized using a dedicated circuit or a general-purpose processor. A field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections or settings of circuit cells inside the LSI may also be used.

[0433] Furthermore, if a new integrated circuit technology that can replace LSI appears due to the progress of semiconductor technology or a derivative technology, it is possible to integrate the functional blocks using that technology. The application of biotechnology is also a possibility.

[0434] <Summary of this disclosure> A radar device according to an embodiment of the present disclosure includes a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarization and a second transmitting antenna that radiates a second polarization different from the first polarization, and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, a transmission signal to which a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence is imparted, wherein each of the plurality of transmitting antennas is associated with the combination in which at least one of the Doppler shift amount and the code sequence is different, and a first pattern of the Doppler shift amount and the code sequence assigned to the first transmitting antenna is different from a second pattern of the Doppler shift amount and the code sequence assigned to the second transmitting antenna.

[0435] In one embodiment of the present disclosure, the number of the plurality of transmitting antennas is less than the total number of the combinations.

[0436] In one embodiment of the present disclosure, the first pattern and the second pattern have a Doppler shift amount interval in which the Doppler multiplexing number of the transmission signal transmitted by the first transmitting antenna is the same as the Doppler multiplexing number of the transmission signal transmitted by the second transmitting antenna, and at least one of the Doppler shift amount intervals associated with the first transmitting antenna is different from the Doppler shift amount interval associated with the second transmitting antenna.

[0437] In one embodiment of the present disclosure, the first pattern and the second pattern relate to a Doppler multiplexing factor, and the Doppler multiplexing factor of the transmission signal transmitted by the first transmitting antenna is different from the Doppler multiplexing factor of the transmission signal transmitted by the second transmitting antenna.

[0438] In one embodiment of the present disclosure, the first pattern and the second pattern are arranged such that, with respect to the order of the intervals of the Doppler shift amounts, a plurality of first Doppler shift intervals between the Doppler shift amounts corresponding to the first transmitting antenna are the same as a plurality of second Doppler shift intervals between the Doppler shift amounts corresponding to the second transmitting antenna, and the order of the plurality of first Doppler shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler shift intervals on the Doppler frequency axis.

[0439] In one embodiment of the present disclosure, the first pattern and the second pattern, with respect to the code sequences, in a plurality of the combinations, the order of the code sequences on the Doppler frequency axis associated with the first transmitting antenna is different from the order of the code sequences on the Doppler frequency axis associated with the second transmitting antenna.

[0440] In one embodiment of the present disclosure, the first pattern and the second pattern relate to the number of code multiplexes by the code sequence, and in a plurality of the combinations, the order of the number of code multiplexes by the code sequence associated with the first transmitting antenna on the Doppler frequency axis is different from the order of the number of code multiplexes by the code sequence associated with the second transmitting antenna on the Doppler frequency axis.

[0441] In one embodiment of the present disclosure, in a plurality of the combinations, for at least one of the first transmitting antenna and the second transmitting antenna, the number of code multiplexes by the code sequence corresponding to at least one of the Doppler shift amounts is different from the number of code multiplexes by the code sequence corresponding to the other Doppler shift amounts.

[0442] In one embodiment of the present disclosure, the antenna further includes a receiving antenna that receives a reflected wave signal of the transmitted signal reflected by a target using either the first polarized wave or the second polarized wave, and a direction estimation circuit that estimates a direction of the target based on the reflected wave signal.

[0443] In one embodiment of the present disclosure, the radio wave receiving apparatus further includes 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, the receiving antennas receiving reflected wave signals of the transmitted signal reflected by a target, and a direction estimation circuit for individually estimating a direction of the target for the reflected wave signals received by the first receiving antenna and the second receiving antenna, respectively.

[0444] In one embodiment of the present disclosure, a combination of transmitting antennas among the multiple transmitting antennas used for multiplexing the transmission signal is switched every transmission period of the transmission signal, every period corresponding to the code length of the code sequence, or every measurement period in the radar device.

[0445] In one embodiment of the present disclosure, the present invention includes a plurality of transmitting antennas including a first transmitting antenna that radiates a first polarization, a second transmitting antenna that radiates a second polarization different from the first polarization, and a third transmitting antenna that radiates a third polarization different from the first polarization and the second polarization, and a transmitting circuit that multiplexes and transmits a transmission signal, to which a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence is imparted, from the plurality of transmitting antennas, wherein each of the plurality of transmitting antennas is associated with the combination in which at least one of the Doppler shift amount and the code sequence is different, and a third pattern of the Doppler 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 shift amount and the code sequence assigned to the second transmitting antenna and the third transmitting antenna. [Industrial Applicability]

[0446] The present disclosure is suitable for a radar device that detects a wide angle range. [Explanation of symbols]

[0447] 10 Radar Equipment 100 Radar transmitter 101 Radar transmission signal generator 102 Transmission signal generation control section 103 Modulation signal generator 104 VCO 105 Phase rotation amount setting section 106 Doppler shift setting section 107 Encoding section 108 Phase Rotation Unit 109 Transmitting antenna section 200,200a Radar receiver 201 Antenna system processing unit 202 Receiving antenna section 203 Receiving Radio Unit 204 Mixer section 205 LPF 206 Signal Processing Section 207 AD conversion section 208 Beat Frequency Analysis Section 209 Output switching unit 210 Doppler analysis unit 211,211a CFAR section 212,212a Coded Doppler demultiplexer 213,213a Direction estimation part

Claims

1. A plurality of transmission antennas including a first transmission antenna that radiates a first polarization wave and a second transmission antenna that radiates a second polarization wave different from the first polarization wave, A transmission circuit that multiplex-transmits a transmission signal to which a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence is applied from the plurality of transmission antennas, Comprising, For each of the plurality of transmission antennas, a combination in which at least one of the Doppler shift amount and the code sequence is different is associated, A first pattern of a Doppler shift amount and a code sequence assigned to the first transmission antenna and a second pattern of a Doppler shift amount and a code sequence assigned to the second transmission antenna are different, Radar device.

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

3. The first pattern and the second pattern relate to the interval of the Doppler shift amount, The Doppler multiplicity of the transmission signal transmitted by the first transmission antenna and the Doppler multiplicity of the transmission signal transmitted by the second transmission antenna are the same, At least one of the intervals of the Doppler shift amount associated with the first transmission antenna is different from the interval of the Doppler shift amount associated with the second transmission antenna, The radar device according to claim 1.

4. The first pattern and the second pattern relate to Doppler multiplicity, The Doppler multiplicity of the transmission signal transmitted by the first transmission antenna and the Doppler multiplicity of the transmission signal transmitted by the second transmission antenna are different, The radar device according to claim 1.

5. The first pattern and the second pattern relate to the order of the intervals of the Doppler shift amount, A plurality of first Doppler shift intervals between the Doppler shift amounts associated with the first transmission antenna and a plurality of second Doppler shift intervals between the Doppler shift amounts associated with the second transmission antenna are the same, The order of the plurality of first Doppler shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler shift intervals on the Doppler frequency axis, The radar device according to claim 1.

6. The first pattern and the second pattern relate to the code sequence, In a plurality of the combinations, the order of the code sequences associated with the first transmission antenna on the Doppler frequency axis is different from the order of the code sequences associated with the second transmission antenna on the Doppler frequency axis. The radar apparatus according to claim 1.

7. The first pattern and the second pattern relate to the code multiplexing by the code sequences. In a plurality of the combinations, the order of the code multiplexing by the code sequences associated with the first transmission antenna on the Doppler frequency axis is different from the order of the code multiplexing by the code sequences associated with the second transmission antenna on the Doppler frequency axis. The radar apparatus according to claim 1.

8. In a plurality of the combinations, for at least one of the first transmission antenna and the second transmission antenna, the code multiplexing by the code sequences associated with at least one of the Doppler shift amounts is different from the code multiplexing by the code sequences associated with the other Doppler shift amounts. The radar apparatus according to claim 1.

9. A receiving antenna that receives a reflected wave signal obtained by reflecting the transmission signal by a target using either one of the first polarization wave and the second polarization wave, A direction estimation circuit that estimates the direction of the target based on the reflected wave signal. The radar apparatus according to claim 1.

10. A plurality of receiving antennas including a first receiving antenna that receives the first polarization wave and a second receiving antenna that receives the second polarization wave, and that receive a reflected wave signal obtained by reflecting the transmission signal by a target, A direction estimation circuit that individually estimates the direction of the target for the reflected wave signals received by the first receiving antenna and the second receiving antenna, respectively. The radar apparatus according to claim 1.

11. Among the plurality of transmission antennas, the combination of the transmission antennas used for multiplex transmission of the transmission signal is switched every transmission period of the transmission signal, a period corresponding to the code length of the code sequence, or a measurement period in the radar apparatus. The radar apparatus according to claim 1.

12. The plurality of transmission antennas further includes a third transmission antenna that emits a third polarization wave different from the first polarization wave and the second polarization wave. The Doppler shift amount and the third pattern of the code sequence assigned to the third transmission antenna are different from the first pattern and the second pattern. The radar apparatus according to claim 1.

13. Applying a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence to a radar signal, Multiplying and transmitting the radar signal to which the phase rotation amount is applied from a plurality of transmission antennas. A method for transmitting a radar signal, The plurality of transmission antennas include a first transmission antenna that emits a first polarization wave and a second transmission antenna that emits a second polarization wave different from the first polarization wave. For each of the plurality of transmission antennas, a combination in which at least one of the Doppler shift amount and the code sequence is different is associated. The first pattern of the Doppler shift amount and the code sequence assigned to the first transmission antenna is different from the second pattern of the Doppler shift amount and the code sequence assigned to the second transmission antenna. A method for transmitting a radar signal.

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

15. The first pattern and the second pattern relate to the interval of the Doppler shift amount. The Doppler multiplicity of the radar signal transmitted by the first transmission antenna is the same as the Doppler multiplicity of the radar signal transmitted by the second transmission antenna. At least one of the intervals of the Doppler shift amount associated with the first transmission antenna is different from the interval of the Doppler shift amount associated with the second transmission antenna. The method for transmitting a radar signal according to claim 13.

16. The first pattern and the second pattern relate to the Doppler multiplicity. The Doppler multiplicity of the radar signal transmitted by the first transmission antenna is different from the Doppler multiplicity of the radar signal transmitted by the second transmission antenna. The method for transmitting a radar signal according to claim 13.

17. The first pattern and the second pattern relate to the order of the intervals of the Doppler shift amount. A plurality of first Doppler shift intervals between the Doppler shift amounts associated with the first transmission antenna and a plurality of second Doppler shift intervals between the Doppler shift amounts associated with the second transmission antenna are the same, wherein an order of the plurality of first Doppler shift intervals on a Doppler frequency axis is different from an order of the plurality of second Doppler shift intervals on the Doppler frequency axis, The method for transmitting a radar signal according to claim 13.

18. The plurality of transmission antennas further include a third transmission antenna that radiates a third polarization wave different from the first polarization wave and the second polarization wave, wherein a third pattern of a Doppler shift amount and a code sequence assigned to the third transmission antenna is different from the first pattern and the second pattern, The method for transmitting a radar signal according to claim 13.

19. A reflected wave signal obtained by reflecting a radar signal transmitted by the method for transmitting a radar signal according to claim 13 from a target is received by a receiving antenna, and a direction of the target is estimated based on the reflected wave signal. A method for receiving a radar signal, wherein the receiving antenna receives the reflected wave signal using either the first polarization wave or the second polarization wave. The method for receiving a radar signal.

20. A phase rotation circuit that imparts a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence to a radar signal, and a transmission circuit that multiplex-transmits the radar signal having the phase rotation amount imparted thereto from a plurality of transmission antennas, comprising: wherein the plurality of transmission antennas include a first transmission antenna that radiates a first polarization wave and a second transmission antenna that radiates a second polarization wave different from the first polarization wave, wherein a combination in which at least one of the Doppler shift amount and the code sequence is different is associated with each of the plurality of transmission antennas, wherein a first pattern of a Doppler shift amount and a code sequence assigned to the first transmission antenna is different from a second pattern of a Doppler shift amount and a code sequence assigned to the second transmission antenna, A radar signal generation device.

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