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

Abstract

To improve the detection accuracy of a target in a radar device.SOLUTION: A radar device includes: multiple transmission antennas which include a first transmission antenna that forms a first beam, and a second transmission antenna that forms a second beam that is different from the first beam; and a transmission circuit which performs multiple transmission of a transmission signal applied with a phase rotation amount corresponding to the combination of a Doppler shift amount and a code series from the multiple transmission antennas. Combinations in which at least one of the Doppler shift amount and the code series is different are associated with the multiple transmission antennas respectively. The first pattern of the Doppler shift amount and the code series assigned to the first transmission antenna is different from the second pattern of the Doppler shift amount and the code series assigned to the second transmission antenna.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] In recent years, radar devices using 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] JP 2019-211388 A [Patent Document 2] US Patent Publication No. 2022 / 0066012 [Patent Document 3] JP 2008-304417 A [Patent Document 4] JP 2014-119344 A [Patent Document 5] JP 2020-204603 A [Patent Document 6] Patent Publication No. 2022-92247 [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 forms a first beam and a second transmitting antenna that forms a second beam different from the first beam, and a transmitting circuit that multiplexes 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 a 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] A diagram showing an example of time division multiplexing (TDM) transmission [Diagram 2] A diagram showing an example of Doppler Division Multiplexing (DDM) transmission. [Diagram 3] FIG. 1 shows an example of non-uniform Doppler multiplex transmission. [Figure 4] A diagram showing an example of a multi-beam transmitting MIMO radar [Diagram 5] A diagram showing an example of Doppler multiplexing in a multi-beam transmitting MIMO radar. [Figure 6] A diagram showing an example of Doppler multiplexing in a multi-beam transmitting MIMO radar. [Figure 7] A block diagram showing a configuration example of a radar device. [Figure 8] FIG. 1 is a diagram showing an example of a transmission signal when a chirp signal is used; [Figure 9] A diagram showing an example of a chirp signal. [Figure 10] FIG. 1 is a diagram showing an example of a transmission signal and a reception signal when a chirp signal is used; [Figure 11] A diagram showing an example of setting the Doppler shift amount [Figure 12] FIG. 1 is a diagram showing an example of a received signal in Doppler multiplex transmission. [Figure 13] A diagram showing an example of a multi-beam transmitting MIMO radar [Figure 14] A diagram showing an example of setting the Doppler shift amount [Figure 15] FIG. 1 is a diagram showing an example of a received signal in Doppler multiplex transmission. [Figure 16] A diagram showing an example of setting the Doppler shift amount [Figure 17] A diagram showing an example of setting the Doppler shift amount [Figure 18] Flowchart showing an example of an operation for separating a Doppler multiplexed signal [Figure 19] A diagram showing an example of the configuration of a transmitting antenna. [Figure 20] A diagram showing an example of a multi-beam transmitting MIMO radar [Figure 21] FIG. 1 shows an example of a MIMO antenna arrangement and a virtual receiving antenna arrangement. [Figure 22] FIG. 1 shows an example of coded Doppler multiplexing. [Diagram 23] A diagram showing an example of a multi-beam transmitting MIMO radar [Figure 24] A diagram showing an example of a multi-beam transmitting MIMO radar [Diagram 25] A diagram showing an example of a multi-beam transmitting MIMO radar DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [About multi-beam radar] For example, there is a method of constructing a MIMO radar using transmitting antennas or receiving antennas with multiple different directional characteristics (or simply called "directivity") with different main beam directions (hereinafter sometimes referred to as "beam directions," "transmitting beam directions," or "receiving beam directions") (see, for example, Patent Document 1 or Patent Document 2).

[0013] Examples of different directional characteristics of a transmitting antenna or a receiving antenna include directional characteristics with the same beam width but different beam directions, directional characteristics with both different beam directions and beam widths, or directional characteristics with the same beam direction but different beam widths.

[0014] Hereinafter, a MIMO radar that uses multiple transmitting antennas with different directional characteristics (for example, transmitting antennas that form different beams) as described above will be referred to as a "multi-beam transmitting MIMO radar." Here, a multi-beam transmitting MIMO radar includes multiple transmitting antennas with different directional characteristics. Note that a multi-beam transmitting MIMO radar may be configured to include one or more transmitting antennas with the same directivity.

[0015] In the following, a MIMO radar that uses multiple receiving antennas with different directional characteristics (for example, receiving antennas that form different beams) as described above is called a "multi-beam receiving MIMO radar." Here, a multi-beam receiving MIMO radar includes multiple receiving antennas with different directional characteristics. Note that a multi-beam receiving MIMO radar may be configured to include one or more receiving antennas with the same directivity.

[0016] Similarly, hereinafter, a MIMO radar that uses a plurality of transmitting antennas and receiving antennas having different directional characteristics as described above will be referred to as a "multi-beam transmitting / receiving MIMO radar" (or a multi-beam MIMO radar).

[0017] For example, examples of multiplexing transmission methods for MIMO radar using multiple transmitting antennas include time division multiplexing (TDM) transmission (e.g., Patent Document 3) and Doppler division multiplexing (DDM) transmission (e.g., Patent Document 4).

[0018] 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.

[0019] [About coded Doppler multiplex transmission] Patent Document 5 (for example, FIG. 1 of Patent Document 5) discloses a multiplexing method that combines Doppler multiplexing and code multiplexing (hereinafter referred to as "Coded Doppler multiplexing" or "Coded DDM").

[0020] For example, FIG. 1 shows an example of the allocation of transmission Doppler frequencies and codes when a radar transmission wave (e.g., a chirp signal) is sent out every transmission period Tr, and a signal multiplexed with an orthogonal code (e.g., code#1, code#2) of code length Loc=2 is transmitted to three transmitting antennas (e.g., Tx#1 to Tx#3) using two Doppler multiplexed signals (e.g., Δfd1, Δfd2).

[0021] The phase rotation based on the code is performed, for example, by cyclically repeating the operation of imparting the chirp signal in a code length transmission period Loc×Tr (two transmission periods (2Tr) in FIG. 1). At this time, the phase rotation based on the Doppler multiplexed signal is constant in the code length transmission period in which a code of code length 2 is imparted (two transmission periods (2Tr) in FIG. 1). For example, the phase rotation based on the Doppler multiplexed signal may be imparted while being changed every 2Tr transmission period.

[0022] For example, in FIG. 1, the amounts of transmission Doppler shift to be assigned are set to Δfd1=-1 / (4Tr) and Δfd2=0 [Hz]. For example, since the amount of transmission Doppler shift Δfd1 is imparted to every n-th transmission period, a phase rotation Φ1(n)=ΔΦ1×(floor(n / Loc)+1) is imparted to the radar transmission wave (chirp signal). Also, since the amount of transmission Doppler shift Δfd2 is imparted to every n-th transmission period, a phase rotation Φ2(n)=ΔΦ2×(floor(n / Loc)+1) is imparted to the radar transmission wave (chirp signal). Here, ΔΦ1=-π and ΔΦ2=0. The Doppler multiplex interval is Δf d =1 / (4Tr). For example, code#1=[1, 1] and code#2=[1, -1] may be used as the orthogonal code of code length 2. In FIG. 1, for example, DopCode#1=(Δfd1, code#1), DopCode#2=(Δfd1, code#2), and DopCode#3=(Δfd2, code#1) are assigned to the transmitting antennas Tx#1 to Tx#3 as coded Doppler multiplexed signals that combine Doppler multiplexed signals and codes, and are transmitted. Furthermore, floor[x] is an operator that outputs the maximum integer not exceeding the real number x.

[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 signal in a transmission period of the code length, for example, the received signal for every odd-numbered transmission period and the received signal for every even-numbered transmission period, in separate Doppler analysis units (e.g., V-FFT#1 and V-FFT#2), and performs code demultiplexing and Doppler demultiplexing based on the output of the Doppler frequency analysis, thereby separating and receiving the multiplexed transmission signals.

[0024] Here, since the radar device (for example, the Doppler analysis unit) uses a received signal of a transmission period (two transmission periods (2Tr) in FIG. 1) of code length times (Loc=2 in FIG. 1), a Doppler frequency exceeding ±1 / (2 Loc Tr) (±1 / (4Tr) in FIG. 1) is detected as aliasing. Whether or not the radar reflected wave received signal contains a component in the aliasing frequency range is determined, for example, as disclosed in Patent Document 5, using a coded Doppler multiplexed signal (DopCode#4=(Δfd2,code#1) in FIG. 1) that is a combination of an unused code that is not assigned to a transmitting antenna and a Doppler multiplexed signal. For example, whether or not the radar reflected wave received signal contains a component in the aliasing frequency range is determined by utilizing the fact that the received power of a signal that has been code-multiplexed and Doppler-multiplexed for a coded Doppler multiplexed signal that is a combination of an unused code that is not assigned to a transmitting antenna and a Doppler multiplexed signal is about the noise level.

[0025] In this way, the radar device makes the code multiplexing number between Doppler multiplexed signals uneven, multiplexes the signals from multiple transmitting antennas, and detects the received signal levels, thereby making it possible to detect the presence or absence of a aliasing signal, expand the Doppler frequency range (maximum Doppler) in which Doppler frequency can be detected without aliasing to ±1 / (2Tr), and also make it possible to determine the transmitting antenna.

[0026] For example, FIG. 2(a) shows the received Doppler signals when the coded Doppler multiplexed signal shown in FIG. 1 is separated into code#1 and code#2 when the target Doppler frequency fdtarget=0. As shown in FIG. 2(a), the received Doppler multiplexed signal separated into code#1 has a Doppler multiplexing interval Δfd1 and Δfd2. d The received levels at two Doppler frequencies with a Doppler frequency interval that matches the Doppler frequency interval Δfd1 and Δfd2 are detected as high, and the radar device can determine that these components are the received signals of Tx#1 and Tx#3. Also, as shown in FIG. 2(a), one Doppler frequency with a high received level is detected in the received Doppler signal separated by code#2, and the Doppler multiple interval Δfd1 and Δfd2 for the detected Doppler frequency is detected as high. d The reception level of the Doppler frequency of the Doppler frequency interval that matches is approximately the noise level. Therefore, the radar device can determine that one Doppler frequency component with a high reception level is the received signal of Tx#2. In addition, the radar device can determine the Doppler frequency of the target because the deviation from the Doppler shift amount at the time of transmission to each transmitting antenna is the Doppler frequency of the target.

[0027] Also, for example, Fig. 2(b) shows the received Doppler signals when the coded Doppler multiplexed signal shown in Fig. 1 is separated into code#1 and code#2 when the target Doppler frequency fdtarget=-1 / (2Tr). As shown in Fig. 2(b), the received Doppler signal separated into code#2 has a Doppler multiplexing interval Δfd1 and Δfd2. d In addition, as shown in FIG. 2B, one Doppler frequency with a high reception level is detected in the received Doppler signal separated by code#1, and the Doppler multiple interval Δfd1 and Δfd2 for the detected Doppler frequency is also detected. dThe reception level of the Doppler frequency of the Doppler frequency interval that matches is approximately the noise level. Therefore, the radar device can determine that one Doppler frequency component with a high reception level is the received signal of Tx#2. In addition, the radar device can determine the Doppler frequency of the target because the deviation from the Doppler shift amount at the time of transmission to each transmitting antenna is the Doppler frequency of the target.

[0028] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit (e.g., V-FFT#1 and V-FFT#2) observes the aliased Doppler frequency. In this case, the actual Doppler frequency differs from the Doppler frequency detected in the Doppler analysis unit (V-FFT#1 and V-FFT#2) by a phase difference of 2π between the transmission periods of 2Tr, so that a phase rotation of π is added between the detection time difference Tr between V-FFT#1 and V-FFT#2. Therefore, the radar device can determine that aliasing exists when the received signal of Tx#2 is determined in the separation of code#1, as shown in FIG. 2(b).

[0029] By performing such a process of separating and receiving the coded Doppler multiplexed signal, the radar device can estimate the Doppler frequency of the radar reflection wave in the Doppler frequency range of ±1 / (2 Tr). In this way, by performing coded Doppler multiplexing transmission, the detectable Doppler frequency range is expanded to ±1 / 2 Tr. For example, compared to Patent Documents 3 and 4, the detectable Doppler frequency range is expanded by Nt times.

[0030] [Application of coded Doppler multiplexing to multi-beam transmitting MIMO radar] As described above, a MIMO radar using coded Doppler multiplexing (also referred to as "coded DDM") differs from a MIMO radar using Doppler multiplexing transmission (DDM) in that a portion of the Doppler frequency range is not assigned to the transmission signal, and the MIMO radar performs a separation process of a Doppler multiplexed signal (hereinafter referred to as "coded Doppler demultiplexing") that estimates the Doppler frequency of the target based on the received power of the received Doppler frequency of the reflected wave from the target after code demultiplexing.

[0031] For this reason, when applying coded Doppler multiplexing to a multi-beam transmission MIMO radar, the following can be expected.

[0032] In a multi-beam transmission MIMO radar, for example, a phenomenon may occur in which the reception level of the reflected wave varies greatly depending on the beam direction (or transmission beam direction) and the target direction. In a multi-beam transmission MIMO radar, the reception level of the reflected wave from the transmitting antenna may vary greatly between when the beam direction and the target direction match and when the beam direction and the target direction do not match. For this reason, in a multi-beam transmission MIMO radar, when multiplexing is performed using coded Doppler multiplexing, the difference in the reception level of the reflected wave between multiple beams with different beam directions ( If the ratio (ratio) is large, Doppler demultiplexing by coded Doppler multiplexing may become difficult. If Doppler demultiplexing becomes difficult, the target detection performance of the MIMO radar may deteriorate, or coded Doppler demultiplexing may be erroneous, resulting in erroneous Doppler estimation or deterioration of angle measurement performance.

[0033] Hereinafter, an example will be described in which Doppler demultiplexing becomes difficult in a multi-beam transmission MIMO radar that employs coded Doppler multiplexing.

[0034] For example, a 4Tx MIMO radar in which two transmitting antennas are included in each of two beam directions will be described. For example, the number of transmitting antennas corresponding to each of the two beam directions is set to "N TxBeam#1 " and "N TxBeam#2 " (N TxBeam#1 =N TxBeam#2=2).

[0035] For example, as shown in Fig. 3, a multi-beam transmission MIMO radar that forms transmission beams (TxBeam#1, TxBeam#2) in two different directions using two transmission antennas out of four transmission antennas Tx#1 to #4 will be described. In Fig. 3, the transmission beams (beam direction) of Tx#1 and Tx#2 are TxBeam#1, and the transmission beams (beam direction) of Tx#3 and Tx#4 are TxBeam#2. In addition, for example, the directional characteristics of the receiving antennas may be omnidirectional, or may be substantially uniform within a field of view (FOV) covered by a plurality of transmitting antennas with different directivities.

[0036] For example, for four transmitting antennas Tx#1 to #4, as shown in FIG. 4(a), the Doppler multiplexing number N DM =3, code multiplex number N CM A case will be described in which a Doppler multiplexed signal coded using =2 is assigned.

[0037] For example, when the target direction is the target direction (1) shown in Fig. 3, the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 coincides with the target direction (1), so that the reception level (e.g., the reflected wave reception level) of the reception signal corresponding to Tx#1 and Tx#2 forming TxBeam#1 becomes relatively high as shown in Fig. 4(b). On the other hand, when the target direction is the target direction (1) shown in Fig. 3, the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 does not coincide with the target direction (1), and the target direction (1) corresponds to the directional null direction (hereinafter also referred to as the null direction) of TxBeam#2. For this reason, for example, as shown in (b) of Fig. 4, the reception level of the reception signal corresponding to Tx#3 and Tx#4 forming TxBeam#2 is lower than the reception level of the reception signal corresponding to TxBeam#1 (Tx#1 and Tx#2). For example, the reception level corresponding to TxBeam#2 is significantly different from the reception level corresponding to TxBeam#1, and may be 10 dB or more lower depending on the beam directivity characteristics in the null direction of TxBeam#2.

[0038] Furthermore, for example, when the target direction is intermediate between the beam direction of TxBeam#1 and the beam direction of TxBeam#2 and is in the direction of an area where the beam widths of both beams, which are approximately 3 dB or 6 dB, overlap with each other (for example, in the case of target direction (2) shown in Figure 3), the reflected waves corresponding to the radar transmission waves transmitted from Tx#1 and Tx#2 forming TxBeam#1 and the reflected waves corresponding to the radar transmission waves transmitted from Tx#3 and Tx#4 forming TxBeam#2 are received at similar levels, as shown in (c) of Figure 4.

[0039] Also, for example, when the target direction is the target direction (3) shown in FIG. 3, the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 coincides with the target direction (3), so as shown in FIG. 4(d), the reception level (e.g., the reflected wave reception level) of the reception signal corresponding to Tx#3 and Tx#4 forming TxBeam#2 becomes relatively high. On the other hand, when the target direction is the target direction (3) shown in FIG. 3, the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 does not coincide with the target direction (3), and the target direction (3) corresponds to the null direction of TxBeam#1. For this reason, for example, as shown in FIG. 4(d), the reception level of the reception signal corresponding to Tx#1 and Tx#2 forming TxBeam#1 becomes lower than the reception level of the reception signal corresponding to TxBeam#2 (Tx#3 and Tx#4). For example, the reception level corresponding to TxBeam#1 differs significantly from the reception level corresponding to TxBeam#2, and may be 10 dB or more lower depending on the beam directivity characteristics in the null direction of TxBeam#1.

[0040] For example, in the case of (c) of FIG. 4, the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 is approximately the same as the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2. Since the code multiplexing number between the Doppler multiplexed signals is non-uniform, the multi-beam transmitting MIMO radar can determine which transmitting antenna used for coded Doppler multiplexing transmission the detected Doppler frequency peak corresponds to based on the reception levels of these received signals. Also, in (c) of FIG. 4, the Doppler frequency fd of the target reflected wave can be determined within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0041] On the other hand, in the case of FIG. 4(b) or FIG. 4(d), since the Doppler frequency of the target is unknown, it is difficult for the multi-beam transmission MIMO radar to determine whether the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 has decreased (for example, the case of FIG. 4(d)) or whether the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 has decreased (for example, the case of FIG. 4(b)). For this reason, it is difficult for the multi-beam transmission MIMO radar to determine which transmission antenna used for coded Doppler multiplex transmission the detected Doppler frequency peak corresponds to based on the reception level of the reception signal. For this reason, it becomes difficult for a multi-beam transmitting MIMO radar to separate Doppler multiplexed signals, and it becomes difficult to determine the Doppler frequency fd of the wave reflected from the target (for example, called the "target reflected wave") within the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0042] In this way, in coded Doppler multiplexing, coded Doppler demultiplexing is performed on the assumption that the reception levels of reflected waves corresponding to each transmitting antenna are approximately the same, and that the reception levels of the Doppler multiplexing intervals that are not Doppler multiplexed are sufficiently low, approximately the noise level. In a multi-beam transmission MIMO radar using coded Doppler multiplexing, the assumptions in the demultiplexing of coded Doppler multiplexing may not hold (the reception levels corresponding to some beams may decrease), as shown in (b) and (d) of Figure 4, and coded Doppler demultiplexing may fail.

[0043] In a non-limiting embodiment of the present disclosure, a method for improving the detection performance of a multi-beam transmitting MIMO radar using coded Doppler multiplexing is described.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The radar device also performs, for example, Doppler multiplexing. Furthermore, the radar device encodes (for example, CDM (Code Division Multiplexing)) signals to which different phase rotations (for example, phase shifts) corresponding to the number of Doppler multiplexes are applied in the Doppler multiplexing (hereinafter, referred to as "Doppler multiplexing signals"), and multiplexes and transmits the signals (hereinafter, referred to as "Coded Doppler Multiplexing").

[0048] [Radar device configuration] The radar device 10 in FIG. 5 includes a radar transmitter (transmitting branch) 100 and a radar receiver (receiving branch) 200.

[0049] 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).

[0050] 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).

[0051] 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.

[0052] 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.

[0053] 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.

[0054] [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 .

[0055] 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.

[0056] 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.

[0057] 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 .

[0058] 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, for example, a frequency chirp signal or a chirp signal) to the phase rotation unit 108 and the radar receiving unit 200 (a mixer unit 204 described later) as, for example, a radar transmission signal (radar transmission wave) as shown in FIG. 6.

[0059] The phase rotation amount setting unit 105 sets an amount of phase rotation (e.g., an amount of phase rotation corresponding to coded Doppler multiplex transmission) to be applied to the radar signal for each radar transmission period Tr in the phase rotation unit 108, based on information relating 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.

[0060] 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.

[0061] 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).

[0062] 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 multiplexed and transmitted from a plurality of transmitting antennas by being imparted with a phase rotation amount corresponding to a combination of a Doppler shift amount and an orthogonal code sequence.

[0063] Next, an example of a method for setting the amount of phase rotation in phase rotation setting section 105 will be described.

[0064] 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.

[0065] 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.

[0066] Doppler shift amount DOP1, DOP2, ~, DOP N_DM ("N_DM" is "N DM For example, the Doppler shift amounts DOP1, DOP2, . . . , DOP may be set to equal intervals, or may be set to 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 the Doppler shift amounts DOP1, DOP2, ~, DOP N_DM may be set to satisfy, for example, equation (1).

number

[0067] Also, for example, the Doppler shift amounts DOP1, DOP2, ..., DOP N_DM The minimum Doppler shift interval Δf MinInterval may satisfy the following formula (2). Note that the Doppler shift interval (also written as Doppler multiple interval or Doppler interval) is the Doppler shift amount DOP1, DOP2, ..., DOP N_DM Here, Loc represents the number of code elements. For example, Loc represents the code length of the code used in the encoding unit 107.

number

[0068] In addition, each Doppler shift amount DOP1, DOP2, ~, DOP N_DM The amount of phase rotation φ for addingndm may be assigned, for example, as shown in the following equation (3).

number

[0069] In addition, the intervals are equal to Δf MinInterval When the Doppler shift amount is set so that ndm The amount of phase rotation φ for adding ndm is assigned, for example, as shown in the following equation (4).

number

[0070] The minimum Doppler shift interval Δf MinInterval The narrower the interval between the Doppler multiplex signals, the more likely it is that interference between the Doppler multiplex signals will occur, and the higher the possibility that the target detection accuracy will decrease (for example, deteriorate). Therefore, it is preferable to widen the interval between the Doppler shift amounts within the range that satisfies the constraints of formula (2). For example, when the equality sign is established in formula (2) (for example, Δf MinInterval =1 / (T r N DM L OC )) can maximize the interval between the Doppler multiplexed signals in the Doppler region (hereinafter, referred to as "maximum equal interval Doppler shift amount setting"). In this case, the Doppler shift amounts DOP1, DOP2, ..., DOP N_DM The phase rotation range is from 0 to less than 2π. DM Each of the two is assigned a different phase rotation amount. For example, the Doppler shift amount 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

[0071] In the formula (5), for example, the Doppler multiplexing number N DM In the case of φ=2, the phase rotation amount φ1 for imparting the Doppler shift amount DOP1 is 0, and the phase rotation amount φ2 for imparting the Doppler shift amount DOP2 is π. For example, ndm The amount of phase rotation φ ndm are equally spaced.

[0072] The Doppler shift amounts 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 Doppler shift amounts DOP1, DOP2, ..., DOP N_DM The phase rotation amount φ1,φ2,~, φ N_DM (However, "N_DM" is N DM ) may be randomly assigned.

[0073] 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

[0074] 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 orthogonal code sequences not exceeding 100. The encoding unit 107 also sets a phase rotation amount based on both the Doppler shift amount and the orthogonal code sequence, for example, an "encoded Doppler phase rotation amount" for generating an encoded Doppler multiplexed signal, and outputs the same to the phase rotation unit 108.

[0075] An example of the operation of the encoding unit 107 will now be described.

[0076] For example, the encoding unit 107 encodes the number of codes (for example, the number of code multiplexes) 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.

[0077] In the following, N CM The orthogonal code sequences are ncm ={OC ncm (1), O.C. ncm (2), ~, O.C. ncm (Loc)}. OC ncm (noc) is the ncmth orthogonal code sequence Code ncm Here, noc is the index of the code element, and noc=1 to Loc.

[0078] 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

[0079] For example, N CM In the case where Loc=2, the code length of the Walsh-Hadamard code is Loc=2, and the orthogonal code sequence is Code1={1,1} and Code2={1,-1}.

[0080] 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 a Doppler multiplexed signal using DOP_CODE (ndm)" where ndm=1~N DM It is.

[0081] The encoding unit 107 encodes the Doppler multiplexed signal by, for example, DOP_CODE (1), N DOP_CODE (2), ~, and N DOP_CODE (N DM ) is equal to the number of transmit antennas used for multiplex transmission, Nt. DOP_CODE (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) using Nt transmitting antennas.

[0082] 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 DOP_CODE (1), N DOP_CODE (2), ~, N DOP_CODE (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 Doppler shift DOP ndm The number of coded Doppler multiplexes N DOP_CODE (ndm) to N CM Therefore, the Doppler shift amount DOP ndm In a plurality of combinations of the orthogonal code sequence and the Doppler shift amount DOP ndm The number of multiplexes (coded Doppler multiplexes) N DOP_CODE (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 Doppler multiplexed signals non-uniformly. With this setting, the radar device 10 can individually separate and receive the signals that are coded Doppler multiplexed from the multiple transmitting antennas over a Doppler range of ±1 / 2Tr, for example, by aliasing determination processing in the receiving processing described later.

[0083] The encoding unit 107 encodes the ndm-th Doppler shift amount DOP ndm The amount of phase rotation φ ndm For this, the coded Doppler phase rotation amount ψ ndop_code(ndm), ndm (m) and outputs it to phase rotation section 108.

number

[0084] Here, the subscript "ndop_code(ndm)" represents the Doppler shift DOP ndm The amount of phase rotation φ ndm Number of coded Doppler multiplexes N for DOP_CODE (ndm) represents the index below. For example, ndop_code(ndm)=1,~, N DOP_CODE (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, where j is the imaginary unit.

[0085] For example, as shown in equation (7), the coded Doppler phase rotation amount ψ ndop_code(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 ndop_code(ndm) Each of the Loc code elements OC ndop_code(ndm) (1),~,OC ndop_code(ndm) (Loc) is assigned a corresponding phase rotation amount (the second term of equation (7)).

[0086] 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). ndop_code(ndm) and varies cyclically within the range from 1 to Loc for each transmission period (Tr), as shown in the following equation (8).

number

[0087] 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.

[0088] Next, in the encoding unit 107, the number of encoded Doppler multiplexes N DOP_CODE An example of a method for setting (ndm) non-uniformly will be described.

[0089] 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

[0090] Next, the coded Doppler phase rotation amount ψ ndop_code(ndm), ndm An example of setting (m) will be explained.

[0091] 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. DOP_CODE (1)=1, N DOP_CODE If (2)=2, the encoding unit 107 calculates the amount of encoded Doppler phase rotation ψ1, 1 (m), ψ 1, 2 (m), ψ 2, 2 (m) and output it to the phase rotation unit 108. For example, the coded Doppler phase rotation amount ψ 1, 1 When setting (m), the encoding unit 107 performs setting as in the following equation (9). Note that in Fig. 7, "◯" 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

[0092] Here, as an example, the Doppler shift amount DOP ndm The amount of phase rotation to be added is expressed as φ ndm =2π(ndm-1) / N DM Then, using the phase rotation amount φ1=0 for imparting the Doppler shift amount DOP1 and the phase rotation amount φ2=π for imparting the Doppler shift amount DOP2, the encoding unit 107 calculates the encoded Doppler phase rotation amount ψ 1, 1 (m), ψ 1, 2 (m), ψ 2, 2 (m) and output to phase rotation section 108. Note that the amount of phase rotation may be expressed in the range of radians equal to or greater than 0 and less than 2π by performing a modulo arithmetic with 2π.

[0093] For example, regardless of the value of the number of transmitting antennas Nt, the number of phases used for the phase rotation amount may be set to be less than the number of transmitting antennas Nt used for multiplex transmission. DM may be made equal to

[0094] In the above example, the setting of the phase rotation amount shown in the maximum equal-interval Doppler shift amount setting has been described, but the setting of the phase rotation amount is not limited to this. For example, the setting of the phase rotation amount shown in the equal-interval Doppler shift amount setting, for example, Equation (6), may be used.

[0095] The method for setting the amount of phase rotation in phase rotation setting section 105 has been described above.

[0096] In FIG. 1, a phase rotation unit 108 rotates the coded Doppler phase rotation amount ψ set in a phase rotation amount setting unit 105. ndop_code(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 ndop_code(ndm)=1~N DOP_CODE (ndm).

[0097] The outputs from the Nt phase rotation units 108 (for example, called coded Doppler multiplexed 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.

[0098] In the following, the coded Doppler phase rotation amount ψ ndop_code(ndm), ndm The phase rotation unit 108 that adds (m) is expressed as "phase rotation unit PROT#[ndop_code(ndm), ndm]". Similarly, the transmission antenna that radiates the output of the phase rotation unit PROT#[ndop_code(ndm), ndm] into space is also expressed as "transmission antenna Tx#[ndop_code(ndm), ndm]". Here, ndm=1 to N DM and ndop_code(ndm)=1~N DOP_CODE (ndm). Alternatively, the Nt transmitting antennas are also denoted as Tx#1, Tx#2, ~, Tx#Nt. The coded Doppler phase rotation amounts imparted to the radar transmission signals transmitted from the transmitting antennas Tx#1, Tx#2, ~, Tx#Nt can be related in advance using a known table or the like. For example, the coded Doppler phase rotation amount ψ ndop_code(ndm), ndm By determining (or detecting) (m), it becomes possible to determine (or detect) the transmitting antenna.

[0099] For example, in the example shown in FIG. 7, the encoding unit 107 transmits to the phase rotation unit 108 an encoded Doppler phase rotation amount ψ 1, 1 (m), ψ1, 2 (m), ψ 2, 2 (m) is input for each transmission period.

[0100] 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 the phase rotation unit PROT#[1,1] is output from the transmitting antenna Tx#[1,1]. Here, cp(t) represents the chirp signal for each transmission period. Similarly, the output of the phase rotation unit PROT#[1,2] is output from the transmitting antenna Tx#[1,2], and the output of the phase rotation unit PROT#[2,2] is output from the transmitting antenna Tx#[2,2].

[0101] The above is the amount of coded Doppler phase rotation ψ ndop_code(ndm), ndm An example of the setting (m) was explained.

[0102] In this embodiment, the number of coded Doppler multiplexes N DOP_CODE 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 DOP_CODE (ndm)) may vary.

[0103] In this embodiment, the number of coded Doppler multiplexes N DOP_CODE When (ndm) is set uniformly, the Doppler shift amount DOP ndm and orthogonal code sequence Code ncm In combination with the Doppler shift DOP ndm The corresponding orthogonal code sequence Code ncm The number of multiplexes (for example, the number of coded Doppler multiplexes N DOP_CODE(ndm)) can be the same. In this case, the Doppler shift amount 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).

[0104] In this embodiment, the transmitting antennas Tx#1 to Tx#Nt may configure a multi-beam transmitting radar including transmitting antennas with at least two different main beam directions (or beam directions). The transmitting antennas Tx#1 to Tx#Nt may include a plurality of transmitting antennas corresponding to different beam directions. The transmitting antennas Tx#1 to Tx#Nt may also include a plurality of transmitting antennas corresponding to the same beam direction.

[0105] For example, the phase rotation amount setting unit 105 sets a different coded Doppler phase rotation amount ψ for each transmitting antenna from which a chirp signal is transmitted, taking into consideration the configurations of transmitting antennas Tx#1 to Tx#Nt with different beam directions. ndop_code(ndm), ndm (m) may be added to the chirp signal and output. This enables the radar device 10 to separate the coded Doppler multiplexed signal even when the received power levels of the reflected waves differ greatly between received signals corresponding to the chirp signals transmitted from transmitting antennas with different beam directions, thereby improving the positioning performance and radar detection performance of the radar device 10.

[0106] An example of the operation of the phase rotation amount setting unit 105 in the radar transmitter 100 in a case where a multi-beam transmitting radar including a transmitting antenna with at least two different beam directions is configured will be described below.

[0107] In the following description, among the multiple beam directions (or multiple beams) used in the multi-beam transmission MIMO radar, the first beam direction (or beam) is written as "B1" and the second beam direction (or beam) is written as "B2". Also, for example, the number of multi-beams with different beam directions is written as "NB", and the qth beam direction (or beam) is written as "Bq". q is an integer value within the number of different beam directions (for example, the number of multi-beams NB). For example, when the number of multi-beams NB=2, q=1 or 2.

[0108] For example, when the number of transmitting antennas is Nt≧3 and the number of Doppler multiplexing N DM ≧2, code multiplex number N CM ≧2, Nt <N DM ×N CM It is.

[0109] In addition, in the transmitting antenna unit 109, the number of transmitting antennas corresponding to the beam direction B1 is set to N B1 Let the number of transmitting antennas corresponding to the beam direction B2 be N B2 In this case, N B1 +N B2 = Nt. In addition, the number of transmitting antennas corresponding to the beam direction Bq is N Bq Let us assume that N Bq ≧1, and the total number of transmitting antennas in each beam direction Bq is Nt.

[0110] In addition, the number of Doppler multiplexes assigned to the transmitting antenna in the beam direction B1 is N DM_B1 The number of Doppler multiplexes assigned to the transmitting antenna in the beam direction B2 is N DM_B2 Here, N DM_B1 , N DM_B2 ≦N DM It is.

[0111] The phase rotation amount setting unit 105 determines, for example, the number of coded Doppler multiplexes N DOP_CODE (ndm) is set to be non-uniform, and the coded Doppler phase rotation amount ψ is set to satisfy the following <Condition 1>. ndop_code(ndm), ndm Set (m), where ndm=1~NDM and ndop_code(ndm)=1~N DOP_CODE (ndm).

[0112] <Condition 1> For example, the Doppler shift amount and code sequence pattern (e.g., coded Doppler multiplexing pattern) assigned to the transmitting antenna of beam direction B1 is made different from the coded Doppler multiplexing pattern assigned to the transmitting antenna of beam direction B2. For example, the phase rotation amount setting unit 105 sets a coded Doppler phase rotation amount ψ that satisfies a different Doppler multiplexing pattern condition (e.g., a Doppler shift amount assignment pattern), a different code multiplexing pattern condition (e.g., a different code multiplexing number between Doppler multiplexed signals), or a different pattern condition of Doppler multiplexing and code multiplexing, for each of the transmitting antenna of beam direction B1 and the transmitting antenna of beam direction B2. ndop_code(ndm), ndm Set (m).

[0113] For example, the different Doppler multiple pattern condition may be any one of the following conditions (eg, also referred to as "Condition 1A"). (A-1) The Doppler multiplexing number corresponding to each beam direction (for example, the Doppler multiplexing number of the transmission signal transmitted from the transmission antenna in each beam direction) is the same (for example, N DM_B1 =N DM_B2 However, N DM_B1 =N DM_B2 ≧2), including a different Doppler shift interval in each beam direction (eg, an interval of Doppler shift amounts associated with the transmitting antennas in each beam direction). (A-2) The number of Doppler multiplexes for each beam direction is different (N DM_B1 ≠N DM_B2 ). (A-3)N DM_B1 ≧3, N DM_B2 In the case where ≧3, when the same Doppler shift interval is included in the Doppler shift intervals for each beam direction, the order of the Doppler shift intervals is different (cyclic mismatch).

[0114] Also, for example, the different code multiplexing pattern condition may be any one of the following conditions (for example, also referred to as "condition 1B"). (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).

[0115] Furthermore, the phase rotation amount setting unit 105 further sets the coded Doppler phase rotation amount ψ so as to satisfy, for example, the following condition 2: ndop_code(ndm), ndm (m) may be set.

[0116] <Condition 2> Signals transmitted from transmitting antennas in the same beam direction are multiplexed by a code multiplexing number that is unequal between Doppler multiplexed signals. The code multiplexing number is 1 or more and N CM For example, in a plurality of combinations of Doppler shift amounts and code sequences, for at least one transmitting antenna in beam direction B1 and beam direction B2, the number of code multiplexes by the code sequence associated with at least one Doppler shift amount is different from the number of code multiplexes by the code sequence associated with the other Doppler shift amounts.

[0117] 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 the beam direction B1 and the transmitting antenna of the beam direction B2 (for example, the combination of the 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 the beam direction B1 may be different from the order on the Doppler frequency axis of the multiple Doppler shift intervals corresponding to the transmitting antenna of the beam direction B2. 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 the beam direction B1 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 the beam direction B2 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 in beam direction B1 and the Doppler shift interval of the transmitting antenna in beam direction B2 do not match (cyclic mismatch) even if either one is cyclically shifted in the Doppler frequency domain.

[0118] Also, for example, in B-1 of condition 1, the order on the Doppler frequency axis of the code sequence associated with the transmitting antenna of beam direction B1 may be different from the order on the Doppler frequency axis of the code sequence associated with the transmitting antenna of beam direction B2. For example, an array in which the indexes of the code sequence corresponding to the Doppler shift amounts assigned to the transmitting antenna of beam direction B1 are arranged in ascending order on the Doppler frequency axis is different from an array in which the indexes of the code sequence corresponding to the Doppler shift amounts assigned to the transmitting antenna of beam direction B2 are arranged in ascending order on the Doppler frequency axis. When B-1 of condition 1 is satisfied, the indexes of the code sequence corresponding to each Doppler shift amount of the transmitting antenna of beam direction B1 and the indexes of the code sequence corresponding to each Doppler shift amount of the transmitting antenna of beam direction B2 do not match (cyclic mismatch) even if one of them is cyclically shifted in the Doppler frequency domain.

[0119] 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 transmitting antenna of the beam direction B1 may be different from the order on the Doppler frequency axis of the code multiplex numbers by the code sequence associated with the transmitting antenna of the beam direction B2. For example, an arrangement in which the code multiplex numbers corresponding to the Doppler shift amounts assigned to the transmitting antenna of the beam direction B1 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 transmitting antenna of the beam direction B2 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 transmitting antenna of the beam direction B1 and the code multiplex numbers corresponding to each Doppler shift amount of the transmitting antenna of the beam direction B2 do not match (cyclic mismatch) even if one of them is cyclically shifted in the Doppler frequency domain.

[0120] By setting the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 so as to satisfy condition 1, even if the received power levels of the reflected waves differ significantly between received signals from transmitting antennas with different beam directions, the radar device 10 can separate the Doppler multiplexed signals and suppress deterioration of the positioning performance and radar detection performance (an example will be described later).

[0121] Furthermore, by setting the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 so as to satisfy condition 2, 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).

[0122] For example, in coded Doppler multiplex 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.

[0123] (Case 1) Case 1 is a case where neither beam direction B1 nor beam direction B2 satisfies condition 2. In case 1, the detectable Doppler frequency range fd is in the range of -1 / (2Tr)≦fd <1 / (2Tr), -1 / (2Loc N DM_B1 Tr)≦fd < 1 / (2Loc N DM_B1 Tr) range or -1 / (2Loc N DM_B2 Tr)≦fd < 1 / (2Loc N DM_B2 Here, if the Doppler multiplexed signals allocated between the transmitting antennas in the beam direction B1 do not include unused codes, N DM_B1 =N B1 / Loc, and the detectable Doppler frequency range fd is -1 / (2 N B1 Tr)≦fd < 1 / (2 N B1 Similarly, if the Doppler multiplexed signals allocated between the transmitting antennas in the beam direction B2 do not include unused codes, the range is N DM_B2 =N B2 / Loc, and the detectable Doppler frequency range fd is -1 / (2 N B2 Tr)≦fd <1 / (2 N B2 Tr).

[0124] (Case 2) Case 2 is a case where the beam direction B2 does not satisfy condition 2. In case 2, the detectable Doppler frequency range fd is in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) or -1 / (2Loc N DM_B2 Tr)≦fd < 1 / (2Loc N DM_B2 For example, if the Doppler multiplexed signal allocated between the transmitting antennas in the beam direction B2 does not include unused codes, the range is N DM_B2 =N B2 / Loc, and the detectable Doppler frequency range fd is -1 / (2 N B2 Tr)≦fd < 1 / (2 N B2 Tr).

[0125] (Case 3) Case 3 is a case where the beam direction B1 does not satisfy condition 2. In case 3, the detectable Doppler frequency range fd is in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) or -1 / (2Loc N DM_B1 Tr)≦fd < 1 / (2Loc N DM_B1 For example, if the Doppler multiplexed signal allocated between the transmitting antennas in the beam direction B1 does not include unused codes, the range is N DM_B1 =N B1 / Loc, and the detectable Doppler frequency range fd is -1 / (2 N B1 Tr)≦fd < 1 / (2 N B1 Tr).

[0126] In all cases 1 to 3, the detectable Doppler frequency range is the Doppler detection range in the case of uniformly spaced Doppler multiplexing -1 / (2 N t Tr)≦fd < 1 / (2 N t Tr).

[0127] An example of setting the amount of coded Doppler phase rotation in the phase rotation setting unit 105 will be described below. Note that, below, the interval between the amounts of Doppler shift applied to Tx#n1 and Tx#n2 is expressed as a Doppler shift interval "Δfd(n1, n2)". Here, Δfd(n1, n2) is the Doppler shift amount DOP applied to Tx#n1. n1 The amount of Doppler shift DOP given to Tx#n2 based on n2 Interval (DOP n2 -DOP n1 ). Note that if the Doppler shift interval Δfd(n1, n2) is a negative value (for example, (DOP n2 -DOP n1 )<0), taking into account 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, the Doppler shift interval Δfd(n1, n2) is calculated using Δfd(n1, n2)=1 / (Loc Tr)-Δfd(n1, n2) and expressed as a positive value.

[0128] <Setting example 1> Setting example 1 is a setting example of the amount of coded Doppler phase rotation when condition 1 (when different code multiplexing pattern conditions are satisfied) and condition 2 are satisfied.

[0129] Figure 8 shows the number of transmit antennas, Nt=4, N B1 =2, N B2 13 shows an example of how the coded Doppler phase rotation amount is set in phase rotation amount setting section 105 when .DELTA..times ...

[0130] In Fig. 8, Tx#1 and Tx#2 are transmitting antennas in beam direction B1, and Tx#3 and Tx#4 are transmitting antennas in beam direction B2. In Fig. 8, shaded circles indicate the allocation of coded Doppler multiplexed signals to transmitting antennas (Tx#1 and Tx#2) in beam direction B1, and white circles indicate the allocation of coded Doppler multiplexed signals to transmitting antennas (Tx#3 and Tx#4) in beam direction B2.

[0131] In addition, in FIG. 8, the Doppler multiplexing number N DM = 3, and the Doppler shift setting unit 106 may set the three Doppler shift amounts DOP1, DOP2, and DOP3 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 8, the phase rotation amount φ1 = 0 that imparts Doppler shift amount DOP1 = 0, the phase rotation amount φ2 = 2π / 3 that imparts Doppler shift amount DOP2 = Δfd, and the phase rotation amount φ3 = 4π / 3 that imparts Doppler shift amount DOP3 = -Δfd (φ3 = -2π / 3 may also be used). As shown in Fig. 8, the intervals between Doppler multiplexed signals (also called Doppler multiplex intervals, Doppler shift intervals, or Doppler intervals) Δfd are equal intervals, and Δfd = 1 / (6Tr).

[0132] In addition, in FIG. 8, 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 of the Walsh-Hadamard code with a code length Loc = 2. Note that in the following setting examples 2 to 5, the code multiplexing number N CM= 2, with similar signs.

[0133] In FIG. 8, 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 DOP_CODE (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0134] As shown in FIG. 8, in the encoding unit 107, the coding Doppler multiplexing number for the Doppler multiplexed signal using the three Doppler shift amounts DOP1, DOP2, and DOP3 input from the Doppler shift setting unit 106 is set as N DOP_CODE (1)=1, N DOP_CODE (2)=1, N DOP_CODE (3)=2. In this way, the phase rotation amount setting unit 105 sets the number of coded Doppler multiplexing for the Doppler multiplexed signal to N DOP_CODE (1)=N DOP_CODE (2) ≠ N DOP_CODE (3) is set as non-uniform.

[0135] In FIG. 8, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =3, for example, Doppler multiplexed signals using Doppler shift amounts DOP1 and DOP3 are assigned (N DM_B1 =2). The encoding unit 107 also assigns Code2 and Code1 to the Doppler multiplexed signals using the Doppler shift amounts DOP1 and DOP3 assigned to the transmitting antennas Tx#1 and Tx#2 in the beam direction B1. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 2, 1 (m), ψ 1, 3 Set (m).

[0136] In FIG. 8, the Doppler shift setting unit 106 sets the Doppler multiplexing 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_B2 =2). The encoding unit 107 also assigns Code2 and Code2 to the Doppler multiplexed signals using the Doppler shift amounts DOP2 and DOP3 assigned to the transmitting antennas Tx#3 and Tx#4 in the beam direction B2. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 2, 2 (m), ψ 2, 3 Set (m).

[0137] In FIG. 8, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the transmitting antenna of the beam direction B1 and the transmitting antenna of the beam direction B2 is N DM_B1 =N DM_B2 = 2, which are the same. In addition, the Doppler intervals of the Doppler multiplexed signals assigned to the transmitting antennas Tx#1 and Tx#2 in the beam direction B1 are Δfd(1,2) = 2Δfd, Δfd(2,1) = Δfd, and the Doppler intervals of the Doppler multiplexed signals assigned to the transmitting antennas Tx#3 and Tx#4 in the beam direction B2 are Δfd(3,4) = Δfd, Δfd(4,3) = 2Δfd, which are the same.

[0138] Therefore, the settings of the coded Doppler phase rotation amount shown in FIG. 8 do not match any of the different Doppler multiplex pattern conditions of condition 1A.

[0139] Also, in FIG. 8, the codes assigned to the transmitting antenna in beam direction B1 for each of the Doppler multiplexed signals using Doppler shift amounts DOP1, DOP2, and DOP3 are [Code 2, no assignment, Code 1], and the number of code multiplexes assigned to each Doppler multiplexed signal is 0 or 1.

[0140] In the following, the code index assigned to the transmitting antenna in beam direction B1 for each of the Doppler multiplexed signals using Doppler shift amounts DOP1, DOP2, and DOP3 will be written as "CodeIndex_B1=(2,*,1)". In CodeIndex_B1, "*" indicates that no code is assigned. Also, when multiple codes are assigned to one Doppler multiplexed signal, it is expressed using "&". For example, when Code1 and Code2 are assigned to one Doppler multiplexed signal, it will be expressed as "1&2". The code index is also called the "code interval".

[0141] In addition, hereinafter, the code multiplexing number assigned to the transmitting antenna in the beam direction B1 for each of the Doppler multiplexed signals using the Doppler shift amounts DOP1, DOP2, and DOP3 will be written as "N_Code_B1=(1,0,1)" (in the case of FIG. 8).

[0142] 8, the codes assigned to the transmitting antennas in the beam direction B2 for each of the Doppler multiplexed signals using Doppler shift amounts DOP1, DOP2, and DOP3 are [no assignment, Code2, Code2], and the number of code multiplexes assigned to each Doppler multiplexed signal is 0 or 1. As with the beam direction B1, the code index assigned to the transmitting antennas in the beam direction B2 for each of the Doppler multiplexed signals using Doppler shift amounts DOP1, DOP2, and DOP3 is written as "CodeIndex_B2=(*,2,2)". Also, the number of code multiplexes assigned to the transmitting antennas in the beam direction B2 for each of the Doppler multiplexed signals using Doppler shift amounts DOP1, DOP2, and DOP3 is written as "N_Code_B2=(0,1,1)".

[0143] Thus, for the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2, the code multiplexing numbers assigned to each Doppler multiplexed signal are N_Code_B1 = (1, 0, 1) and N_Code_B2 = (0, 1, 1), which results in cyclic consistency and does not satisfy B-2 of condition 1.

[0144] On the other hand, for the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2, the code indexes assigned to each Doppler multiplexed signal are CodeIndex_B1 = (2, *, 1) and CodeIndex_B2 = (*, 2, 2), which are different (or cyclically inconsistent; hereinafter, this is also expressed as the code index intervals being different).

[0145] Also, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit 210 described later observes the folded Doppler frequency. In this case, the code indexes are CodeIndex_B1_alias=(1,*,2) and CodeIndex_B2_alias=(*,1,1), which are different (cyclic mismatch). Therefore, in the example of FIG. 8, when the Doppler frequency of the target is in the range of -1 / (2Tr)≦fdtarget<-1 / (2Tr), the code indexes are cyclic mismatch and the code intervals are different. Therefore, the code intervals assigned to each Doppler multiplexed signal are different between the multi-beams, so B-1 of Condition 1 is satisfied and the different code multiplexing pattern conditions are met.

[0146] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG.

[0147] In FIG. 8, the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna in the beam direction B1 is N_Code_B1=(1,0,1), and the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna in the beam direction B2 is N_Code_B2=(0,1,1). Both are multiplexed and transmitted with code multiplexing numbers that are uneven between the Doppler multiplexed signals, and the code multiplexing number ranges from 1 to N. CM Included in the range of -1 or less.

[0148] Therefore, in the example of FIG. 8, signals transmitted from transmitting antennas in the same beam direction (for example, beam directions B1 and B2) are multiplexed and transmitted with a code multiplexing number that is uneven between Doppler multiplexed signals, and the code multiplexing number is from 1 to N. CM The coded Doppler phase rotation amount is within the range of -1 or less. Therefore, the setting of the coded Doppler phase rotation amount shown in Fig. 8 is a setting example that satisfies condition 2 in both beam direction B1 and beam direction B2.

[0149] Below, we will explain an example of the received signal at the output of the Doppler analysis unit 210 when the transmitting antenna unit 109 includes transmitting antennas with beam directions B1 and B2 based on the setting of the coded Doppler phase rotation amount shown in Figure 8, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with approximately uniform directional characteristics within the field of view covered by both the transmitting antennas in beam direction B1 and beam direction B2).

[0150] FIG. 9 shows an example of the output of the Doppler analysis unit 210 for a target reflected wave at a certain distance index. For example, the target reflected wave has fd target Therefore, the radar device 10 calculates fd from the Doppler shift amount set in the radar transmitter 100. target In FIG. 9, as an example, the Doppler frequency fd of the reflected wave from the target is target If = 0, and fd target This shows the case where =1 / (2Tr).

[0151] FIG. 10 illustrates an example of a multi-beam transmitting MIMO radar (for example, the radar device 10) that forms transmission beams in a beam direction B1 (Tx Beam#1) and a beam direction B2 (Tx Beam#2).

[0152] For example, when the target direction is the target direction (1) shown in FIG. 10 (for example, when a target exists around the beam direction B1), the radiation direction of the radar transmission waves transmitted from Tx#1 and Tx#2 in the beam direction B1 coincides with the target direction. Therefore, as shown in FIG. 9(a), the reception level of the reception signal of the reflected wave from the target corresponding to Tx#1 and Tx#2 in the radar device 10 is relatively high. On the other hand, when the target direction is the target direction (1) shown in FIG. 10, the radiation direction of the radar transmission waves transmitted from Tx#3 and Tx#4 in the beam direction B2 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmission beam B2. Therefore, as shown in FIG. 9(a), the reception level of the reception signal of the reflected wave from the target corresponding to Tx#3 and Tx#4 in the radar device 10 is lower than the reception level of the reception signal corresponding to each transmission antenna (for example, Tx#1, Tx#2) in the beam direction B1. For example, as shown in Fig. 9(a), the reception level of the reception signal corresponding to Tx#3 and Tx#4 is significantly different from the reception level of the reception signal corresponding to Tx#1 and Tx#2, and depending on the beam directivity characteristics in the null direction of Tx#3 and Tx#4, the reception level may be 10 dB or more lower. Here, in Fig. 9, the size of the shaded or white circles represents the reception power. Smaller circles represent smaller reception power (e.g., reception power as low as the noise level) than larger circles.

[0153] Furthermore, for example, when the target direction is an intermediate direction between beam direction B1 and beam direction B2 and the target direction is an area direction where the beam widths of both beams, each of which is approximately 3 dB or 6 dB, overlap each other (for example, target direction (2) shown in Figure 10), as shown in (b) of Figure 9, the reception level of the received signals (reflected waves of the radar transmission wave) corresponding to Tx#1 and Tx#2 in beam direction B1 is approximately the same as the reception level of the received signals (reflected waves of the radar transmission wave) corresponding to Tx#3 and Tx#4 in beam direction B2.

[0154] Also, for example, when the target direction is the target direction (3) shown in FIG. 10 (for example, when a target exists around the beam direction B2), the radiation direction of the radar transmission waves transmitted from Tx#3 and Tx#4 in the beam direction B2 coincides with the target direction. Therefore, as shown in FIG. 9(c), the reception level of the reception signal of the reflected wave from the target corresponding to Tx#3 and Tx#4 in the radar device 10 becomes relatively high. On the other hand, when the target direction is the target direction (3) shown in FIG. 10, the radiation direction of the radar transmission waves transmitted from Tx#1 and Tx#2 in the beam direction B1 does not coincide with the target direction, and the target direction corresponds to the null direction of the transmission beam B1. Therefore, as shown in FIG. 9(c), the reception level of the reception signal of the reflected wave from the target corresponding to Tx#1 and Tx#2 in the radar device 10 becomes lower than the reception level of the reception signal corresponding to each transmission antenna (for example, Tx#3, Tx#4) in the beam direction B2. For example, as shown in (c) of Figure 9, the reception level of the reception signals corresponding to Tx#1 and Tx#2 is significantly different from the reception level of the reception signals corresponding to Tx#3 and Tx#4, and depending on the beam directivity characteristics in the null direction of Tx#1 and Tx#2, the reception level may be 10 dB or more lower.

[0155] For example, as shown in FIG. 9(b), when the target direction is an intermediate direction between beam direction B1 and beam direction B2 (target direction (2) shown in FIG. 10), the radar device 10 receives signals corresponding to the transmitting antennas of each beam direction at approximately the same reception level. Therefore, signals transmitted from Nt transmitting antennas including the transmitting antennas of beam direction B1 and beam direction B2 are coded Doppler multiplexed using a known coded Doppler multiplexed signal setting. Therefore, the radar device 10 can separate the coded Doppler multiplexed signal based on the existing coding Doppler multiplexed signal separation operation. The existing coding Doppler multiplexed signal separation operation is disclosed in, for example, Patent Documents 5 and 6. The same applies to the following embodiments.

[0156] Furthermore, when the target direction is beam direction B1 as shown in FIG. 9(a) (target direction (1) shown in FIG. 10) and when the target direction is beam direction B2 as shown in FIG. 9(c) (target direction (3) shown in FIG. 10), the radar device 10 receives two Doppler multiplexed signals with similar Doppler intervals. This makes it difficult for the radar device 10 to distinguish between Doppler multiplexed signals based on the amount of Doppler shift. On the other hand, as shown in FIG. 9(a) and (c), the code multiplexed signals for the Doppler multiplexed signals are different (for example, the code intervals are different and B-1 of condition 1 is satisfied), so the radar device 10 receives coded Doppler multiplexed signals that are different between FIG. 9(a) and FIG. 9(c).

[0157] As a result, when the target direction is beam direction B1 or B2, the radar device 10 can distinguish between a case where the reception level of the reception signal corresponding to the transmitting antenna in beam direction B1 decreases and a case where the reception level of the reception signal corresponding to the transmitting antenna in beam direction B2 decreases in the coded Doppler multiplex separation unit 212 described later.

[0158] Furthermore, if it is determined from this determination result that the signal is a reception signal of the transmitting antennas (Tx#1, Tx#2) in the beam direction B1, the settings of the coded Doppler multiplexed signals for Tx#1, Tx#2 in the beam direction B1 are known, so the radar device 10 can separate the multiplexed signals, for example, by the operations disclosed in Patent Documents 5 and 6. Also, if it is determined that the signal is a reception signal of the transmitting antennas (Tx#3, Tx#4) in the beam direction B2, the settings of the coded Doppler multiplexed signals for Tx#3, Tx#4 in the beam direction B2 are known, so the radar device 10 can similarly separate the multiplexed signals.

[0159] Furthermore, by setting the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 so as to satisfy condition 2 in addition to condition 1, the Doppler detection range can be expanded to a range equivalent to that in the case of one transmitting antenna (a range of ±1 / (2Tr)) (an example will be described later).

[0160] By operating the coded Doppler multiplex 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 coded Doppler multiplex signal.

[0161] <Setting example 2> Setting example 2 is a setting example of the amount of coded Doppler phase rotation when condition 1 (when different code multiplexing pattern conditions are satisfied) and condition 2 are satisfied.

[0162] Figure 11 shows the number of transmit antennas, Nt=6, N B1 =3, N B2 13 shows an example of how the coded Doppler phase rotation amount is set in phase rotation amount setting section 105 when .DELTA..times ...

[0163] In Fig. 11, Tx #1 to #3 are transmitting antennas in beam direction B1, and Tx #4 to #6 are transmitting antennas in beam direction B2. In Fig. 11, hatched circles indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx #1 to #3) in beam direction B1, and white circles indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx #4 to #6) in beam direction B2.

[0164] In addition, in FIG. 11, the Doppler multiplexing number N DM = 4, and the Doppler shift setting unit 106 may set four Doppler shift amounts DOP1 = 0, DOP2 = Δfd, DOP3 = -2Δfd, and DOP4 = -Δfd, for example, by using the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 11, the phase rotation amounts for imparting the Doppler shift amounts DOP1 to DOP4 are φ1 = 0, φ2 = π / 4, φ3 = π / 2, and φ2 = 3π / 4, respectively. As shown in Fig. 11, the Doppler multiple intervals Δfd are equal, and Δfd = 1 / (8Tr).

[0165] In FIG. 11, 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 N t <NDM ×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N DOP_CODE (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0166] As shown in FIG. 11, in the encoding unit 107, the coding Doppler multiplexing number for the Doppler multiplexed signal using the four Doppler shift amounts DOP1 to DOP4 input from the Doppler shift setting unit 106 is set as N DOP_CODE (1)=2, N DOP_CODE (2)=1, N DOP_CODE (3)=2, N DOP_CODE (4)=1. In this way, the phase rotation amount setting unit 105 sets the number of coded Doppler multiplexing for the Doppler multiplexed signal to N DOP_CODE (1) ≠ N DOP_CODE (2) or N DOP_CODE (3) ≠ N DOP_CODE (4) is set as non-uniform.

[0167] In FIG. 11, 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, DOP3, and DOP4 are assigned (N DM_B1 =3). Furthermore, the encoding unit 107 assigns Code1, Code1, and Code2 to the Doppler multiplexed signals using the Doppler shift amounts DOP1, DOP3, and DOP4, respectively. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 1, 1 (m), ψ 1,3 (m), ψ 2, 4 Set (m).

[0168] In FIG. 11, for the transmitting antennas Tx#4 to #6 in the beam direction B2, the Doppler shift setting unit 106 sets the Doppler multiplex number N DMOf the four Doppler multiplexed signals, for example, Doppler multiplexed signals using Doppler shift amounts DOP1, DOP2, and DOP3 are assigned (N DM_B2 =3). Furthermore, the encoding unit 107 assigns Code2, Code2, and Code2 to the Doppler multiplexed signals using the Doppler shift amounts DOP1, DOP2, and DOP3, respectively. For example, the phase rotation amount setting unit 105 assigns the encoded Doppler phase rotation amount ψ 2, 1 (m), ψ 2, 2 (m), ψ 2, 3 Set (m).

[0169] In FIG. 11, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the transmitting antenna of the beam direction B1 and the transmitting antenna of the beam direction B2 is N DM_B1 =N DM_B2 = 3, which are identical. Furthermore, the Doppler intervals of Doppler multiplexed signals assigned to transmitting antennas Tx #1 to #3 in beam direction B1 are Δfd(1,3) = 2Δfd, Δfd(3,4) = Δfd, and Δfd(4,1) = Δfd, and the Doppler intervals of Doppler multiplexed signals assigned to transmitting antennas Tx #4 to #6 in beam direction B2 are Δfd(1,2) = Δfd, Δfd(2,3) = Δfd, and Δfd(3,1) = 2Δfd, which are identical (cyclic coincidence).

[0170] Therefore, the settings of the coded Doppler phase rotation amount shown in FIG. 11 do not match any of the different Doppler multiplex pattern conditions of condition 1A.

[0171] Also, in FIG. 11, the code indexes assigned to the transmitting antennas in beam direction B1 and the transmitting antennas in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 to DOP4 are CodeIndex_B1=(1,*,1,2) and CodeIndex_B2=(2,2,2,*), which results in a cyclic mismatch and the code index intervals are different, thereby satisfying B-1 of condition 1.

[0172] Also, in FIG. 11, the code multiplexing numbers assigned to the transmitting antennas in beam direction B1 and the transmitting antennas in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 to DOP4 are N_Code_B1=(1,0,1,1) and N_Code_B2=(1,1,0,1), which is a cyclic match and the code multiplexing numbers are the same, so B-2 of condition 1 is not satisfied.

[0173] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit 210 described later observes the folded Doppler frequency. In this case, the code indexes are CodeIndex_B1_alias=(2,*,2,1) and CodeIndex_B2_alias=(1,1,1,*), which are different (cyclic mismatch). Therefore, in the example of FIG. 11, when the Doppler frequency of the target is in the range of -1 / (2Tr)≦fdtarget<-1 / (2Tr), the code indexes are cyclic mismatch and the code intervals are different. Therefore, B-1 of condition 1 is satisfied, and the different code multiplexing pattern conditions are met.

[0174] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG.

[0175] In FIG. 11, the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna in the beam direction B1 is N_Code_B1=(1,0,1,1), and the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna in the beam direction B2 is N_Code_B2=(1,1,0,1). Both are multiplexed and transmitted with code multiplexing numbers that are uneven between the Doppler multiplexed signals, and the code multiplexing number ranges from 1 to N. CM Included in the range of -1 or less.

[0176] Therefore, in the example of FIG. 11, signals transmitted from transmitting antennas in the same beam direction (for example, beam directions B1 and B2) are multiplexed and transmitted with a code multiplexing number that is uneven between Doppler multiplexed signals, and the code multiplexing number is from 1 to N. CM The coded Doppler phase rotation amount is within the range of -1 or less. Therefore, the setting of the coded Doppler phase rotation amount shown in Fig. 11 is a setting example that satisfies condition 2 in both beam direction B1 and beam direction B2.

[0177] Below, we will explain an example of the received signal at the output of the Doppler analysis unit 210 when the transmitting antenna unit 109 includes a transmitting antenna with different beam directions B1 and B2 based on the setting of the Doppler shift amount shown in Figure 11, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with approximately uniform directional characteristics within the field of view covered by both the transmitting antennas in beam direction B1 and beam direction B2).

[0178] For example, when the target direction is target direction (1) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B1), or when the target direction is target direction (3) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B2), the number of Doppler multiplexed signals, the code interval, and the code multiplexing number are different between the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B1. Therefore, the radar device 10 can distinguish, in the coded Doppler multiplex separation unit 212 described later, between a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B1 decreases and a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B2 decreases.

[0179] Furthermore, if it is determined from this determination result that the signal is a reception signal of a transmitting antenna (Tx #1 to #3) in beam direction B1, the settings of the coded Doppler multiplexed signals for Tx #1 to #3 in beam direction B1 are known, so the radar device 10 can separate the multiplexed signals, for example, by the operations disclosed in Patent Documents 5 and 6. If it is determined that the signal is a reception signal of a transmitting antenna (Tx #4 to #6) in beam direction B2, the settings of the coded Doppler multiplexed signals for Tx #4 to #6 in beam direction B2 are known, so the radar device 10 can similarly separate the multiplexed signals.

[0180] Furthermore, by setting the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 so as to satisfy condition 2 in addition to condition 1, the Doppler detection range can be expanded to a range equivalent to that in the case of one transmitting antenna (a range of ±1 / (2Tr)) (an example will be described later).

[0181] By operating the coded Doppler multiplex 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 coded Doppler multiplex signal.

[0182] <Setting example 3> Setting example 3 is a setting example of the coded Doppler phase rotation amount when condition 1 (when different code multiplexing pattern conditions and Doppler multiplexing pattern conditions are satisfied) and when condition 2 is satisfied.

[0183] Figure 12 shows the number of transmit antennas, Nt=6, N B1 =3, N B2 4 shows an example of how the coded Doppler phase rotation amount is set in phase rotation amount setting section 105 when .DELTA..times ...

[0184] In Fig. 12, Tx #1 to #3 are transmitting antennas in beam direction B1, and Tx #4 to #6 are transmitting antennas in beam direction B2. In Fig. 12, hatched circles indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx #1 to #3) in beam direction B1, and white circles indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx #4 to #6) in beam direction B2.

[0185] In addition, in FIG. 12, the Doppler multiplexing number N DM = 4, and the Doppler shift setting unit 106 may set the four Doppler shift amounts DOP1 to DOP4 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 12, the phase rotation amounts for imparting the Doppler shift amounts DOP1 = 0, DOP2 = Δfd, DOP3 = -2Δfd, and DOP4 = -Δfd are φ1 = 0, φ2 = π / 4, φ3 = π / 2, and φ2 = 3π / 4, respectively. As shown in Fig. 12, the Doppler multiplex intervals Δfd are equal, and Δfd = 1 / (8Tr).

[0186] In FIG. 12, 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 N t <N DM ×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N DOP_CODE (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0187] As shown in FIG. 12, in the encoding unit 107, the coding Doppler multiplexing number for the Doppler multiplexed signal using the four Doppler shift amounts DOP1 to DOP4 input from the Doppler shift setting unit 106 is set as N DOP_CODE (1)=2, N DOP_CODE (2)=1, N DOP_CODE (3)=2, N DOP_CODE (4)=1. In this way, the phase rotation amount setting unit 105 sets the number of coded Doppler multiplexing for the Doppler multiplexed signal to N DOP_CODE (1) ≠ NDOP_CODE (2) or N DOP_CODE (3) ≠ N DOP_CODE (4) is set as non-uniform.

[0188] In FIG. 12, 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 DOP3 are assigned (N DM_B1 =2). Furthermore, the encoding unit 107 assigns Code1, Code1, and Code2 to the Doppler multiplexed signals using the Doppler shift amounts DOP1 and DOP3, respectively (for example, two codes are used). For example, the phase rotation amount setting unit 105 sets the encoded Doppler phase rotation amount ψ 1, 1 (m), ψ 1,3 (m), ψ 2, 3 Set (m).

[0189] In FIG. 12, for the transmitting antennas Tx#4 to #6 in the beam direction B2, 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, DOP2, and DOP4 are assigned (N DM_B2 =3). Furthermore, the encoding unit 107 assigns Code2, Code2, and Code2 to the Doppler multiplexed signals using the Doppler shift amounts DOP1, DOP2, and DOP4, respectively (for example, one code is used). For example, the phase rotation amount setting unit 105 assigns the encoded Doppler phase rotation amount ψ 2, 1 (m), ψ 2, 2 (m), ψ 2, 4 Set (m).

[0190] In FIG. 12, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the transmitting antenna of the beam direction B1 and the transmitting antenna of the beam direction B2 is N DM_B1 =2, N DM_B2= 3, which is a different Doppler multiplex number, and therefore satisfies A-2 of Condition 1.

[0191] Also, in FIG. 12, the code indexes assigned to the transmitting antennas in beam direction B1 and the transmitting antennas in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 to DOP4 are CodeIndex_B1=(1,*,1&2,*) and CodeIndex_B2=(2,2,*,2), which results in a cyclic mismatch and the code index intervals are different, thereby satisfying B-1 of condition 1.

[0192] Also, in FIG. 12, the code multiplexing numbers assigned to the transmitting antennas in beam direction B1 and the transmitting antennas in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 to DOP4 are N_Code_B1=(1,0,2,0) and N_Code_B2=(1,1,0,1), and since the code multiplexing numbers are different, B-2 of condition 1 is satisfied.

[0193] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit 210 described later observes the folded Doppler frequency. In this case, the code index is CodeIndex_B1_alias=(2,*,1&2,*) and CodeIndex_B2_alias=(1,1,*,1), which is different (cyclic mismatch). Therefore, in the example of FIG. 12, when the Doppler frequency of the target is in the range of -1 / (2Tr)≦fdtarget<-1 / (2Tr), the code index is cyclic mismatch and the code interval is different. Therefore, B-1 of condition 1 is satisfied, and the different code multiplexing pattern condition is met.

[0194] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG.

[0195] In addition, in Fig. 12, the code multiplexing numbers assigned to each Doppler multiplexed signal in each transmitting antenna of beam direction B1 and beam direction B2 are N_Code_B1 = (1, 0, 2, 0) and N_Code_B2 = (1, 1, 0, 1). Therefore, in the example of Fig. 12, signals transmitted from transmitting antennas in the same beam direction are multiplexed and transmitted with code multiplexing numbers that are uneven between Doppler multiplexed signals, and the code multiplexing number ranges from 1 to N. CM 12 is a setting example that satisfies condition 2 in both beam direction B1 and beam direction B2.

[0196] Below, we will explain an example of the received signal at the output of the Doppler analysis unit 210 when the transmitting antenna unit 109 includes a transmitting antenna with different beam directions B1 and B2 based on the setting of the Doppler shift amount shown in Figure 12, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with approximately uniform directional characteristics within the field of view covered by both the transmitting antennas in beam direction B1 and beam direction B2).

[0197] For example, when the target direction is target direction (1) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B1), or when the target direction is target direction (3) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B2), the number of Doppler multiplexed signals, the code interval, and the code multiplexing number are different between the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B1. Therefore, the radar device 10 can distinguish, in the coded Doppler multiplex separation unit 212 described later, between a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B1 decreases and a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B2 decreases.

[0198] Furthermore, if it is determined from this determination result that the signal is a reception signal of a transmitting antenna (Tx #1 to #3) in beam direction B1, the settings of the coded Doppler multiplexed signals for Tx #1 to #3 in beam direction B1 are known, so the radar device 10 can separate the multiplexed signals, for example, by the operations disclosed in Patent Documents 5 and 6. Furthermore, if it is determined that the signal is a reception signal of a transmitting antenna (Tx #4 to #6) in beam direction B2, the settings of the coded Doppler multiplexed signals for Tx #4 to #6 in beam direction B2 are known, so the radar device 10 can similarly separate the multiplexed signals.

[0199] Furthermore, by setting the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 so as to satisfy condition 2 in addition to condition 1, the Doppler detection range can be expanded to a range equivalent to that in the case of one transmitting antenna (a range of ±1 / (2Tr)) (an example will be described later).

[0200] By operating the coded Doppler multiplex 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 coded Doppler multiplex signal.

[0201] <Setting example 4> Setting example 4 is an example of setting the amount of coded Doppler phase rotation when condition 1 (different code multiplexing pattern condition) is satisfied but condition 2 is not satisfied.

[0202] Figure 13 shows the number of transmit antennas, Nt=3, N B1 =2, N B2 4 shows an example of how the coded Doppler phase rotation amount is set in phase rotation amount setting section 105 when .times. ...

[0203] In Fig. 13, Tx#1 and Tx#2 are transmitting antennas in beam direction B1, and Tx#3 is a transmitting antenna in beam direction B2. In Fig. 13, shaded circles indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx#1 and Tx#2) in beam direction B1, and white circles indicate the allocation of coded Doppler multiplexed signals to the transmitting antenna (Tx#3) in beam direction B2.

[0204] In addition, in FIG. 13, the Doppler multiplexing number N DM = 2, and the Doppler shift setting unit 106 may set the two Doppler shift amounts 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 that imparts the Doppler shift amount DOP1 = 0 is φ1 = 0, and the phase rotation amount φ2 that imparts the Doppler shift amount DOP2 = -Δfd is φ2 = π. As shown in Fig. 13, the Doppler multiple intervals Δfd are equal, and Δfd = 1 / (4Tr).

[0205] In FIG. 13, 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 N t <N DM ×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N DOP_CODE (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0206] As shown in FIG. 13, in the encoding unit 107, the number of coded Doppler multiplexes for the Doppler multiplexed signals using the two Doppler shift amounts DOP1 and DOP2 input from the Doppler shift setting unit 106 is set to N DOP_CODE (1)=1, N DOP_CODE (2)=2. In this way, the phase rotation amount setting unit 105 determines the coded Doppler multiplexing number N DOP_CODE (1) ≠ N DOP_CODE (2) is set as uneven.

[0207] In FIG. 13, for the transmitting antennas Tx#1 and Tx#2 in the beam direction B1, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =2, for example, Doppler multiplexed signals using Doppler shift amounts DOP1 and DOP2 are assigned (N DM_B1 =2). The encoding unit 107 also assigns Code1 and Code1 to the Doppler multiplexed signals using the Doppler shift amounts DOP1 and DOP2 assigned to the transmitting antennas Tx#1 and Tx#2 in the beam direction B1. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 1, 1 (m), ψ 1, 2 Set (m).

[0208] In FIG. 13, for the transmitting antenna Tx#3 in the beam direction B2, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =2, for example, a Doppler multiplexed signal using a Doppler shift amount DOP2 is assigned (N DM_B2 =1). Furthermore, the encoding unit 107 assigns Code2 to the Doppler multiplexed signal using the Doppler shift amount DOP2 assigned to the transmitting antenna Tx#3 in the beam direction B2. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 2, 2 Set (m).

[0209] In FIG. 13, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the transmitting antenna of the beam direction B1 and the transmitting antenna of the beam direction B2 is N DM_B1 =2, N DM_B2 = 1, A-2 of Condition 1 is satisfied.

[0210] In addition, in FIG. 13, the code indexes assigned to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 and DOP2 are CodeIndex_B1=(1,1) and CodeIndex_B2=(*,2), which results in a cyclic mismatch and the code index intervals are different, thereby satisfying B-1 of condition 1.

[0211] In addition, in FIG. 13, the code multiplexing numbers assigned to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 and DOP2 are N_Code_B1=(1,1) and N_Code_B2=(0,1), and since the code multiplexing numbers are different, B-2 of condition 1 is satisfied.

[0212] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit 210 described later observes the folded Doppler frequency. In this case, the code indexes are CodeIndex_B1_alias=(2,2) and CodeIndex_B2_alias=(*,1), which are different (cyclic mismatch). Therefore, in the example of FIG. 13, when the Doppler frequency of the target is in the range of -1 / (2Tr)≦fdtarget<-1 / (2Tr), the code indexes are cyclic mismatch and the code intervals are different. Therefore, B-1 and B-2 of condition 1 are satisfied, and different code multiplexing pattern conditions are met.

[0213] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG.

[0214] In addition, in Figure 13, the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna in beam direction B1 is N_Code_B1 = (1, 1), and the Doppler multiplexed signals are multiplexed and transmitted with a uniform code multiplexing number, so condition 2 is not satisfied.

[0215] On the other hand, in FIG. 13, the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna of the beam direction B2 is N_Code_B2=(0,1), and the Doppler multiplexed signals are multiplexed and transmitted with an uneven code multiplexing number between the Doppler multiplexed signals. The code multiplexing number ranges from 1 to N. CM 12 is an example of a setting that satisfies condition 2. The setting of the coded Doppler phase rotation amount shown in FIG.

[0216] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG. 13 are a setting example that does not satisfy condition 2 for the transmitting antenna in beam direction B1, but satisfies condition 2 for the transmitting antenna in beam direction B2.

[0217] Below, we will explain an example of the received signal at the output of the Doppler analysis unit 210 when the transmitting antenna unit 109 includes a transmitting antenna with different beam directions B1 and B2 based on the setting of the Doppler shift amount shown in Figure 13, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with approximately uniform directional characteristics within the field of view covered by both the transmitting antennas in beam direction B1 and beam direction B2).

[0218] For example, when the target direction is target direction (1) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B1), or when the target direction is target direction (3) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B2), the code multiplexing number differs between the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B1. Therefore, the radar device 10 can distinguish, in the coded Doppler multiplex separation unit 212 described later, between a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B1 decreases and a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B2 decreases.

[0219] Furthermore, if it is determined from this determination result that the signal is a reception signal of the transmitting antenna (Tx#1, Tx#2) in the beam direction B1, the settings of the coded Doppler multiplexed signals for Tx#1 and Tx#2 in the beam direction B1 are known, so the radar device 10 can separate the multiplexed signals, for example, by the operations disclosed in Patent Documents 5 and 6. Furthermore, if it is determined that the signal is a reception signal of the transmitting antenna (Tx#3) in the beam direction B2, the settings of the coded Doppler multiplexed signals for Tx#3 in the beam direction B2 are known, so the radar device 10 can similarly separate the multiplexed signals.

[0220] In addition, in the setting example 4, the setting of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 does not satisfy the condition 2 for the beam direction B1. In this case, the detectable Doppler frequency range fd is in the range of -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2LocN DM_B1 Tr)≦fd < 1 / (2 Loc N DM_B1 This has the effect of expanding the Doppler detection range depending on the target direction compared to the Doppler detection range of the equal-interval DDM, which is -1 / (6 Tr)≦fd < 1 / (6 Tr).

[0221] <Setting example 5> Setting example 5 is an example of setting the amount of coded Doppler phase rotation when condition 1 (different Doppler multiplexing pattern condition and code multiplexing pattern condition) is satisfied but condition 2 is not satisfied.

[0222] Figure 14 shows the number of transmit antennas, Nt=4, N B1 =2, N B2 13 shows an example of how the coded Doppler phase rotation amount is set in phase rotation amount setting section 105 when .DELTA..times ...

[0223] In Fig. 14, Tx#1 and Tx#2 are transmitting antennas in beam direction B1, and Tx#3 and Tx#4 are transmitting antennas in beam direction B2. In Fig. 14, shaded circles indicate the allocation of coded Doppler multiplexed signals to transmitting antennas (Tx#1 and Tx#2) in beam direction B1, and white circles indicate the allocation of coded Doppler multiplexed signals to transmitting antennas (Tx#3 and Tx#4) in beam direction B2.

[0224] In addition, in FIG. 14, the Doppler multiplexing number N DM =3, and the Doppler shift setting unit 106 may set the three Doppler shift amounts DOP1, DOP2, and DOP3 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 14, the phase rotation amounts for imparting the Doppler shift amounts DOP1=0, DOP2=Δfd, and DOP3=-Δfd are φ1=0, φ2=2π / 3, and φ3=4π / 3 (or φ3=-2π / 3 may be used). As shown in Fig. 14, the Doppler multiple intervals Δfd are equal, and Δfd=1 / (6Tr).

[0225] In FIG. 14, 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 N t <N DM ×N CM Therefore, the phase rotation amount setting unit 105 sets the coded Doppler multiplexing number N DOP_CODE (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0226] As shown in FIG. 14, in the encoding unit 107, the number of coded Doppler multiplexes for the Doppler multiplexed signal using the three Doppler shift amounts DOP1, DOP2, and DOP3 input from the Doppler shift setting unit 106 is set to N DOP_CODE (1)=1, N DOP_CODE (2)=1, N DOP_CODE (3)=2. In this way, the phase rotation amount setting unit 105 determines the coded Doppler multiplexing number N DOP_CODE (1) = N DOP_CODE(2) ≠ N DOP_CODE (3) is set as non-uniform.

[0227] In FIG. 14, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =3, for example, Doppler multiplexed signals using Doppler shift amounts DOP1 and DOP2 are assigned (N DM_B1 =2). Furthermore, the encoding unit 107 assigns Code2 and Code2 to the Doppler multiplexed signals using the Doppler shift amounts DOP1 and DOP2 assigned to the transmitting antennas Tx#1 and Tx#2 in the beam direction B1, respectively. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 2, 1 (m), ψ 2, 2 Set (m).

[0228] In addition, in FIG. 14, the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =3, for example, a Doppler multiplexed signal using a Doppler shift amount DOP3 is assigned (N DM_B2 =1). The encoding unit 107 also assigns two codes, Code1 and Code2, to the Doppler multiplexed signal using the Doppler shift amount DOP3 assigned to the transmitting antennas Tx#3 and Tx#4 in the beam direction B2. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 1, 3 (m), ψ 2, 3 Set (m).

[0229] In FIG. 14, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to the transmitting antenna of the beam direction B1 and the transmitting antenna of the beam direction B2 is N DM_B1 =2, N DM_B2 = 1, A-2 of Condition 1 is satisfied.

[0230] In addition, in FIG. 14, the code indexes assigned to the transmitting antennas in beam direction B1 and the transmitting antennas in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1, DOP2, and DOP3 are CodeIndex_B1=(1,1,*) and CodeIndex_B2=(*,*,1&2), which results in a cyclic mismatch and the code index intervals are different, thereby satisfying B-1 of condition 1.

[0231] Also, in FIG. 14, the code multiplexing numbers assigned to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1, DOP2, and DOP3 are N_Code_B1=(1,1,0) and N_Code_B2=(0,0,2), and since the code multiplexing numbers are different, B-2 of condition 1 is satisfied.

[0232] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit 210 described later observes the folded Doppler frequency, and the code index in this case is CodeIndex_B1_alias=(2,2,*) and CodeIndex_B2_alias=(*,*,1&2), which is different (cyclic mismatch). Therefore, in the example of FIG. 14, when the Doppler frequency of the target is in the range of -1 / (2Tr)≦fdtarget<-1 / (2Tr), the code index is cyclic mismatch and the code interval is different. Therefore, B-1 and B-2 of condition 1 are satisfied, and different code multiplexing pattern conditions are met.

[0233] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG.

[0234] In FIG. 14, the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna of the beam direction B1 is N_Code_B1=(1,1,0), and the Doppler multiplexed signals are multiplexed and transmitted with uneven code multiplexing numbers. The code multiplexing number ranges from 1 to N.CM Since it is within the range of -1 or less, condition 2 is met.

[0235] On the other hand, in FIG. 14, the code multiplexing number assigned to each Doppler multiplexed signal in the transmitting antenna of the beam direction B2 is N_Code_B2=(0,0,2), and the Doppler multiplexed signals are multiplexed and transmitted with uneven code multiplexing numbers. The code multiplexing number is set to 1 or more and N CM Since it is not within the range of -1 or less, condition 2 is not met.

[0236] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG. 14 are a setting example that satisfies condition 2 for the transmitting antenna in beam direction B1, but does not satisfy condition 2 for the transmitting antenna in beam direction B2.

[0237] Below, we will explain an example of the received signal at the output of the Doppler analysis unit 210 when the transmitting antenna unit 109 includes a transmitting antenna with different beam directions B1 and B2 based on the setting of the Doppler shift amount shown in Figure 14, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with approximately uniform directional characteristics within the field of view covered by both the transmitting antennas in beam direction B1 and beam direction B2).

[0238] For example, when the target direction is target direction (1) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B1), or when the target direction is target direction (3) shown in FIG. 10 (e.g., when a target exists in the vicinity of beam direction B2), the code multiplexing number differs between the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B1. Therefore, the radar device 10 can distinguish, in the coded Doppler multiplex separation unit 212 described later, between a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B1 decreases and a case where the reception level of the receiving signal corresponding to the transmitting antenna in beam direction B2 decreases.

[0239] Furthermore, if it is determined from this determination result that the signal is a reception signal of the transmitting antennas (Tx#1, Tx#2) in the beam direction B1, the settings of the coded Doppler multiplexed signals for Tx#1 and Tx#2 in the beam direction B1 are known, so the radar device 10 can separate the multiplexed signals, for example, by the operations disclosed in Patent Documents 5 and 6. Furthermore, if it is determined that the signal is a reception signal of the transmitting antennas (Tx#3, Tx#4) in the beam direction B2, the settings of the coded Doppler multiplexed signals for Tx#3 and Tx#4 in the beam direction B2 are known, so the radar device 10 can similarly separate the multiplexed signals.

[0240] In addition, in the setting example 5, the setting of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 does not satisfy the condition 2 for the beam direction B2. In this case, the detectable Doppler frequency range fd is in the range of -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2LocN DM_B2 Tr)≦fd < 1 / (2 Loc N DM_B2 This has the effect of expanding the Doppler detection range depending on the target direction compared to the Doppler detection range of the equal-interval DDM, which is -1 / (6 Tr)≦fd < 1 / (6 Tr).

[0241] An example of setting the amount of coded Doppler phase rotation in phase rotation amount setting section 105 has been described above.

[0242] The setting of the coded Doppler phase rotation amount is not limited to the above-mentioned setting examples 1 to 5. For example, when the number of transmitting antennas is Nt and the number of transmitting antennas in the beam direction B1 is N B1 , the number of transmitting antennas in beam direction B2 is N B2 , Doppler multiplex number (N DM , N DM_B1 , N DM_B2 ), code multiplexing number (N CM , N CM_B1 , N CM_B2 At least one of the following may be a different value: number of multi-beams NB, code interval, and Doppler shift interval. In addition, in the above setting examples 1 to 5, the code multiplexing number N CMAlthough a setting example using the code of =2 is shown, the present invention is not limited to this. For example, CM Even if it is set as ≧3, the same coded Doppler phase rotation amount can be set.

[0243] [Configuration of radar receiver 200] 5, the radar receiver 200 includes a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. The radar receiver 200 also includes Na antenna system processors 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 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.

[0244] 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.

[0245] Each antenna system processing unit 201 includes a radio reception unit 203 and a signal processing unit 206 .

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] The beat frequency analysis unit 208 calculates N data 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).

[0251] 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).

[0252] 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

[0253] 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.

[0254] Based on the orthogonal code element index OC_INDEX input from the encoding unit 107 of the phase rotation amount setting unit 105, the output switching unit 209 selectively switches and outputs the output of the beat frequency analysis unit 208 for each transmission period to the OC_INDEX-th Doppler analysis unit 210 among the Loc Doppler analysis units 210. For example, in the m-th transmission period Tr, the output switching unit 209 selects the OC_INDEX-th Doppler analysis unit 210 obtained by equation (8).

[0255] 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 Here, noc is the index of the code element, noc=1 to Loc.

[0256] 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.

[0257] 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.

[0258] For example, the output VFT of the Doppler analysis unit 210 of the z-th signal processing unit 206 z noc (f b , f s ) is expressed by the following formula (11), where j is the imaginary unit and z=1 to Na.

number

[0259] The processing in each component of the signal processing unit 206 has been described above.

[0260] [Example of operation of CFAR section 211] In FIG. 5, 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 f b_cfar and the Doppler frequency index f s_cfar Extract.

[0261] The CFAR unit 211 calculates the output VFT of the Doppler analyzer 210 of the first to Na-th signal processors 206 as shown in the following equation (12), for example. 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).

number

[0262] The CFAR unit 211 adaptively sets a threshold value and calculates a distance index f b_cfar , the Doppler frequency index f s_cfar , and the received power information PowerFT(f b_cfar , f s_cfar ) to the coded Doppler demultiplexing unit 212.

[0263] The Doppler shift amount 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 Doppler frequency domain at the output of the Doppler analysis unit 210, peaks are detected at intervals of ΔFD for each signal that is Doppler shift multiplexed.

[0264] FIG. 15(a) shows the N DM 15 shows an example of the output of the Doppler analysis unit 210 at a distance where reflected waves from three targets exist when Ncode=2. For example, as shown in (a) of FIG. 15, when reflected waves from three targets are observed at Doppler frequency indexes f1, f2, and f3, the reflected waves are also observed at Doppler frequency indexes spaced apart by ΔFD (e.g., f1-ΔFD, f2-ΔFD, f3-ΔFD+Ncode) for each of f1, f2, and f3.

[0265] Therefore, the CFAR unit 211 may divide each output of the Doppler analysis unit 210 into ranges of intervals ΔFD of the Doppler shift amount, and perform CFAR processing (for example, called "Doppler domain compression CFAR processing") after adding power of each signal peak position that is Doppler multiplexed for each divided range as shown in the following formula (13). Here, f s_comp =-ΔFD / 2,…,-ΔFD / 2-1. For example, ΔFD=Ncode / N DM If f s_comp =Ncode / (2N DM ),…,Ncode / (2N DM )-1.

number

[0266] However, in formula (13),

number

[0267] Similarly, in equation (13),

number

[0268] FIG. 15B shows an example of an output after applying the Doppler domain compression process shown in equation (13) to the output of the Doppler analysis unit 210 shown in FIG. 15A. As shown in FIG. 15B, N DM If Ncode=2, the CFAR unit 211 adds the power component of Doppler frequency index f1 and the power component of f1-ΔFD by Doppler region compression processing and outputs the result. Similarly, as shown in FIG. 15(b), the CFAR unit 211 adds the power component of Doppler frequency index f2 and the power component of f2-ΔFD and outputs the result. Furthermore, for the power component of Doppler frequency index f3, since f3-ΔFD is smaller than -Ncode / 2, the CFAR unit 211 adds the power component of Doppler frequency index f3 and f3-ΔFD+Ncode (for example, Ncode / 2). DM If = 2, the power component of f3 + ΔFD) is added and output.

[0269] As a result of the Doppler domain compression, the range of the Doppler frequency index fs_comp in the Doppler frequency domain is -ΔFD / 2 or more, ~, ΔFD / 2-1 or less (ΔFD=Ncode / N DM In the case of -Ncode / (2N DM ) or more,…,Ncode / (2N DM )-1 or less).

[0270] The CFAR unit 211 using the Doppler domain compression CFAR process adaptively sets a threshold value, for example, and selects a distance index f b_cfar , the Doppler frequency index f s_comp_cfar , and N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), nfd=1,…,N DM to the coded Doppler demultiplexing unit 212.

[0271] [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. 5 will be described.

[0272] In the following, an example of the processing of the coded Doppler demultiplexing unit 212 will be described when Doppler domain compression CFAR processing is used in the CFAR unit 211. Also, the operation of the coded Doppler demultiplexing unit 212 will be described when omnidirectional antennas (or antennas with approximately uniform directional characteristics over the entire viewing angle covered by multiple transmitting antennas with different beam directions) are used as multiple receiving antennas.

[0273] FIG. 16 is a flowchart showing an example of the demultiplexing operation in the coded Doppler demultiplexing section 212. As shown in FIG.

[0274] <Step A-1> The coded Doppler demultiplexing section 212 performs coded Doppler demultiplexing processing on the Nt coded Doppler multiplexed signals.

[0275] For example, the coded Doppler demultiplexing unit 212 receives the distance index f b_cfar , the Doppler frequency index f s_comp_cfar , and N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), nfd=1~N DM ), the output of the Doppler analysis unit 210 is used to separate the Nt coded Doppler multiplexed signals, and the transmitting antenna is identified (e.g., determined or identified) and the Doppler frequency (e.g., Doppler velocity or relative velocity) is determined.

[0276] 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 DOP_CODE (1), N DOP_CODE (2),…, N DOP_CODE (N DM ) to N CM At least one coded Doppler multiplex number is set to N CM This is achieved by setting the number of pixels to a value smaller than the number of pixels (non-uniform setting).

[0277] For example, the coded Doppler demultiplexing unit 212 (1) performs code demultiplexing processing to set the number of coded Doppler multiplexes to N CM The coded Doppler multiplexing unit 212 detects coded Doppler multiplexed signals set to less than 100 (for example, detects unused coded Doppler multiplexed signals not used for multiplexing) and performs aliasing determination. After that, the coded Doppler multiplexing separation unit 212 (2) performs Doppler code separation processing of the coded Doppler multiplexed signals used for multiplexing based on the aliasing determination result.

[0278] The operation of such a 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 Documents 5 and 6, so a detailed description of the operation will be omitted.

[0279] 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 DOP_CODE (1), N DOP_CODE (2), ~, N DOP_CODE (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 (for example, Patent Documents 5 and 6).

[0280] <Step A-2> The coded Doppler multiplex separation unit 212 judges whether or not the Nt coded Doppler multiplex signals are normally detected. If the Nt coded Doppler multiplex signals are normally detected, the coded Doppler multiplex separation unit 212 performs the process of step A-3, and if the signals are not normally detected, the coded Doppler multiplex separation unit 212 performs the process of step B-1.

[0281] For example, in the process of step A-1, depending on the coincidence between the main beam direction of the multi-beam and the target direction, there are cases where the Nt coded Doppler multiplexed signals are not detected normally.

[0282] For example, a multi-beam MIMO radar is configured using two transmitting antennas with beam directions B1 and B2, and the setting of the phase rotation amount setting unit 105 is N DM >N DM_B1 , or N DM >N DM_B2 (where N DM_B1 , N DM_B2 <N DM In this case, if the main beam direction of the multi-beam does not match the target direction and a target exists in the null direction, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), the received power differs by a predetermined value or more, or a component with received power as small as the noise level is included. In such a case, the coded Doppler demultiplexing unit 212 DM Since fewer than 10 coded Doppler multiplex signals are detected, it is determined that the detection is not normal, and the process of step B-1 is carried out.

[0283] For example, for the transmitting antenna in the beam direction B1, the phase rotation amount setting unit 105 is set to N DM =N DM_B1When the main beam direction B2 of the multi-beam does not coincide with the target direction and the target direction is in the null direction, or when the setting of the phase rotation amount setting unit 105 for the transmitting antenna of the beam direction B2 is N DM = DM_B2 If the main beam direction B2 of the multi-beam does not match the target direction and the target direction is in the null direction, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), the received power is within a predetermined range. In this case, during code separation processing, the unused coded Doppler multiplexed signal that is not used for multiplex transmission is received within the assumed (N DM Since the number of coded Doppler multiplex signals is greater than the number of coded Doppler multiplex signals assumed (N −Nt), the coded Doppler multiplex separation unit 212 fails to determine whether or not the coded Doppler multiplex signals are aliased, making it difficult to normally detect the Nt coded Doppler multiplex signals. DM Since more than Nt are detected, it is determined that the detection is not normal, and the process of step B-1 is carried out.

[0284] <Step A-3> The coded Doppler demultiplexing unit 212 performs coded Doppler demultiplexing processing on the coded Doppler multiplexed signal used for multiplex transmission based on the aliasing determination result to obtain a received signal Y z (f b_cfar ,f s_comp_cfar ,ncm,ndm) as the distance index f b_cfar and the Doppler frequency index f s_comp_cfar At the same time, it outputs the result to the direction estimation unit 213.

[0285] Here, Y z (f b_cfar ,f s_comp_cfar, ndop_code(ndm), ndm) is the distance index f of the Doppler analysis unit 210 in the z-th antenna system processing unit 201. b_cfar and the Doppler frequency index f s_comp_cfar , the Doppler shift amount DOP ndm and orthogonal code ndop_code(ndm) For example, Y z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) represents a signal transmitted from a transmitting antenna Tx#[ndop_code(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 ndop_code(ndm)=1~N DOP_CODE (ndm)

[0286] 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.

[0287] 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.

[0288] <Step B-1> The coded Doppler demultiplexing unit 212 assumes that the target direction is the beam direction B1. B1 The coded Doppler multiplexed signals are subjected to coded Doppler demultiplexing processing.

[0289] For example, the coded Doppler demultiplexing unit 212 receives the distance index f b_cfar , the Doppler frequency index f s_comp_cfar , and N DMThe Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), nfd=1~N DM ), using the output of the Doppler analysis unit 210, B1 The coded Doppler multiplexed signals are separated and transmit antenna discrimination (eg, determination or identification) and Doppler frequency (eg, Doppler velocity or relative velocity) discrimination is performed.

[0290] Here, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), or when the received power differs by more than a certain value, or when the received power component is as small as the noise level (N DM -N DM_B1 ) may be included. Note that the setting of the phase rotation amount setting unit 105 may be N DM =N DM_B1 If so, then (N DM -N DM_B1 )=0, and does not include components whose received power is as small as the noise level. These Doppler multiplexed signals are unused Doppler multiplexed signals that are not used for multiplex transmission.

[0291] Therefore, the coded Doppler demultiplexing unit 212 receives, for example, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), the N with the highest power DM_B1 Doppler multiplex signals are extracted.

[0292] For example, the top N powers extracted DM_B1 When the Doppler multiplex interval of the Doppler multiplexed signals matches the Doppler multiplex interval assigned to the transmitting antenna of the beam direction B1, the coded Doppler multiplex separation unit 212 (1) performs code separation processing and extracts the coded Doppler multiplex number N from the coded Doppler multiplexed signals assigned to the transmitting antenna of the beam direction B1. CM The coded Doppler multiplexing unit 212 detects coded Doppler multiplexed signals set to less than 100 (for example, detects unused coded Doppler multiplexed signals not used for multiplexing) and performs aliasing determination. After that, the coded Doppler multiplexing separation unit 212 (2) performs Doppler code separation processing of the coded Doppler multiplexed signals used for multiplexing based on the aliasing determination result.

[0293] The operation of such a 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 Documents 5 and 6, so a detailed description of the operation will be omitted.

[0294] In addition, by setting the amount of coded Doppler phase rotation to satisfy condition 2, for example, the operation of the coded Doppler demultiplexing unit 212 described above makes it possible to detect the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) (for example, Patent Documents 5 and 6).

[0295] <Step B-2> The coded Doppler demultiplexing unit 212 detects N B1 N B1 The coded Doppler multiplexing unit 212 judges whether N coded Doppler multiplexed signals are normally detected. B1 If the coded Doppler multiplexed signals are detected normally, the process of step B-3 is carried out, and if they are not detected normally, the process of step C-1 is carried out.

[0296] For example, in the process of step B-1, depending on the coincidence between the main beam direction of the multi-beam and the target direction, N B1 In some cases, the coded Doppler multiplexed signals may not be detected normally.

[0297] The coded Doppler demultiplexing unit 212 extracts, for example, the N highest power components DM_B1 Doppler multiplex signals and other power-lower (N DM -N DM_B1 ) Doppler multiplexed signals, it is determined that the target direction is not beam direction B1, and the process of step C-1 is performed.

[0298] In addition, the top N of the extracted power DM_B1 If the Doppler multiplex interval of the Doppler multiplexed signal does not match the Doppler multiplex interval assigned to the transmitting antenna of beam direction B1, the coded Doppler multiplex separation unit 212 determines that the target direction is not beam direction B1 and performs processing of step C-1.

[0299] For example, the phase rotation amount setting unit 105 sets N DM_B1 =N DM_B2 In this case, if the main beam direction B2 of the multi-beam does not match the target direction and a target exists in the null direction, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM In this case, the unused coded Doppler multiplexed signal that is not used for multiplex transmission is received within the assumed N B1 Therefore, the coded Doppler multiplexing separation unit 212 fails to detect aliasing, and B1In such a case, it becomes difficult to normally detect the coded Doppler multiplexed signals. B1 It is determined that the detection is not normal for the coded Doppler multiplexed signals, and the process of step C-1 is carried out.

[0300] <Step B-3> The coded Doppler demultiplexing unit 212 divides N B1 The received signal YB1 is a coded Doppler demultiplexed signal that is used for multiplex transmission from the 1 transmitting antennas. z (f b_cfar ,f s_comp_cfar ,ncm,ndm) as the distance index f b_cfar and the Doppler frequency index f s_comp_cfar At the same time, it outputs the result to the direction estimation unit 213.

[0301] Here, YB1 z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) is the distance index f of the Doppler analysis unit 210 in the z-th antenna system processing unit 201. b_cfar and the Doppler frequency index f s_comp_cfar , the Doppler shift amount DOP ndm and orthogonal code ndop_code(ndm) For example, YB1 is a demultiplexed output of a coded Doppler multiplexed signal (e.g., a coded Doppler demultiplexed result). z (f b_cfar ,f s_comp_cfar ,ndop_code(ndm),ndm) is the N B1 represents a received signal transmitted from a transmitting antenna Tx#[ndop_code(ndm), ndm], reflected by a target, and received by the z-th antenna system processor 201. Note that z=1 to Na. Also, ndm=1 to N DM and ndop_code(ndm)=1~N DOP_CODE (ndm), and the beam direction is B1. B1Signals other than those assigned to the transmitting antennas are output as zero.

[0302] In addition, the coded Doppler demultiplexing unit 212 may output the Doppler frequency of the detected target to the direction estimating unit 213.

[0303] 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.

[0304] <Step C-1> The coded Doppler demultiplexing unit 212 assumes that the target direction is the beam direction B2, and B2 The coded Doppler multiplexed signals are subjected to coded Doppler demultiplexing processing.

[0305] For example, the coded Doppler demultiplexing unit 212 receives the range index f b_cfar , the Doppler frequency index f s_comp_cfar , and N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), nfd=1~N DM ), using the output of the Doppler analysis unit 210, B2 The coded Doppler multiplexed signals are separated and transmit antenna discrimination (eg, determination or identification) and Doppler frequency (eg, Doppler velocity or relative velocity) discrimination is performed.

[0306] Here, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(fb_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), or when the received power differs by more than a certain value, or when the received power is as small as the noise level (N DM -N DM_B2 ) may be included. Note that the setting of the phase rotation amount setting unit 105 may be N DM =N DM_B2 If (N DM -N DM_B2 )=0, and does not include components whose received power is as small as the noise level. These Doppler multiplexed signals are unused Doppler multiplexed signals that are not used for multiplex transmission.

[0307] Therefore, the coded Doppler demultiplexing unit 212 receives, for example, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), the N with the highest power DM_B2 Doppler multiplex signals are extracted.

[0308] For example, the top N powers extracted DM_B2 When the Doppler multiplex interval of the Doppler multiplexed signals matches the Doppler multiplex interval assigned to the transmitting antenna of the beam direction B2, the coded Doppler multiplex separation unit 212 (1) performs code separation processing and extracts the coded Doppler multiplex number N from the coded Doppler multiplexed signals assigned to the transmitting antenna of the beam direction B2. CM The coded Doppler multiplexing unit 212 detects coded Doppler multiplexed signals set to less than 100 (for example, detects unused coded Doppler multiplexed signals not used for multiplexing) and performs aliasing determination. After that, the coded Doppler multiplexing separation unit 212 (2) performs Doppler code separation processing of the coded Doppler multiplexed signals used for multiplexing based on the aliasing determination result.

[0309] The operation of such a 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 Documents 5 and 6, so a detailed description of the operation will be omitted.

[0310] In addition, by setting the amount of coded Doppler phase rotation to satisfy condition 2, for example, the operation of the coded Doppler demultiplexing unit 212 described above makes it possible to detect the Doppler frequency of the target estimated in the range of -1 / (2Tr) ≦ fd < 1 / (2Tr) (for example, Patent Documents 5 and 6).

[0311] <Step C-2> The coded Doppler demultiplexing unit 212 detects N B2 N B2 The coded Doppler multiplexing unit 212 judges whether N coded Doppler multiplexed signals are normally detected. B2 If the coded Doppler multiplexed signals are detected normally, the process of step C-3 is carried out, and if they are not detected normally, the process of step D is carried out.

[0312] For example, in the process of step C-1, depending on the coincidence between the main beam direction of the multi-beam and the target direction, N B2 In some cases, the coded Doppler multiplexed signals may not be detected normally.

[0313] The coded Doppler demultiplexing unit 212 extracts, for example, the N highest power components DM_B2 Doppler multiplex signals and other power-lower (N DM -N DM_B2 ) Doppler multiplexed signals, it is determined that the target direction is not beam direction B2, and the process of step D is performed.

[0314] In addition, the top N of the extracted power DM_B2If the Doppler multiplex interval of the Doppler multiplexed signal does not match the Doppler multiplex interval assigned to the transmitting antenna of beam direction B2, the coded Doppler multiplex separation unit 212 determines that the target direction is not beam direction B2 and performs processing of step D.

[0315] For example, for the beam direction B2, the phase rotation amount setting unit 105 is set to N DM_B1 =N DM_B2 In this case, if the main beam direction B2 of the multi-beam does not match the target direction and a target exists in the null direction, N DM The Doppler frequency index (f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD) received power PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM In this case, the unused coded Doppler multiplexed signal that is not used for multiplex transmission is received within the assumed N B2 Therefore, the coded Doppler multiplexing separation unit 212 fails to detect aliasing, and B2 In such a case, it becomes difficult to normally detect the coded Doppler multiplexed signals. B2 It is determined that the detection is not normal for the coded Doppler multiplexed signals, and the process of step D is performed.

[0316] <Step C-3> The coded Doppler demultiplexing unit 212 divides N B2 The received signal YB2 is the result of the coded Doppler demultiplexing process of the coded Doppler multiplexed signal used for multiplex transmission from the transmitting antennas. z (f b_cfar ,f s_comp_cfar ,ncm,ndm) as the distance index f b_cfar and the Doppler frequency index f s_comp_cfarAt the same time, it outputs the result to the direction estimation unit 213.

[0317] Here, YB2 z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) is the distance index f of the Doppler analysis unit 210 in the z-th antenna system processing unit 201. b_cfar and the Doppler frequency index f s_comp_cfar , the Doppler shift amount DOP ndm and orthogonal code ndop_code(ndm) The output of the coded Doppler multiplexed signal (e.g., the coded Doppler multiplexed signal separation result) is shown in Fig. 1. For example, YB2 z (f b_cfar ,f s_comp_cfar ,ndop_code(ndm),ndm) is the N B2 represents a received signal transmitted from a transmitting antenna Tx#[ndop_code(ndm), ndm], reflected by a target, and received by the z-th antenna system processor 201. Note that z=1 to Na. Also, ndm=1 to N DM and ndop_code(ndm)=1~N DOP_CODE (ndm), and the beam direction is B2. B1 Signals other than those assigned to the transmitting antennas are output as zero.

[0318] In addition, the coded Doppler demultiplexing unit 212 may output the Doppler frequency of the detected target to the direction estimating unit 213.

[0319] 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.

[0320] <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.

[0321] In the above-mentioned operation example of the coded Doppler demultiplexing unit 212, the case where the number of multibeams NB=2 has been described, but the number of multibeams NB is not limited to this, and may be, for example, 3 or more. For example, when the number of multibeams NB=3, the coded Doppler demultiplexing unit 212 may further continue performing Doppler demultiplexing processing for a beam direction different from beam directions B1 and B2 (or an overlapping beam range or a different beam, for example, beam direction B3) in step D (or between step C-2 and step D). This makes it possible to perform a similar Doppler demultiplexing operation even when the number of multibeams is further increased.

[0322] An example of the operation of the coded Doppler demultiplexing unit 212 has been described above.

[0323] The distance index f b_cfar , the Doppler frequency index f sddm_cfar , and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) is present, the coded Doppler demultiplexing unit 212 may perform the coded Doppler demultiplexing operation described above multiple times for each of the distance index, the Doppler frequency index, and the reception power information.

[0324] [Example of operation of direction estimation unit 213] Next, an example of the operation of the direction estimator 213 shown in FIG. 5 will be described.

[0325] In the following explanation, an example of the operation of the direction estimation unit 213 will be described when the multiple receiving antennas of the receiving antenna unit 202 are the same omnidirectional antenna or an antenna with approximately uniform directional characteristics within the viewing angle of multiple transmitting antennas with different beam directions.

[0326] The direction estimation unit 213 estimates, for example, a signal (for example, a distance index fb_cfar , the received signal Y z (f b_cfar ,f s_comp_cfar ,ndop_code(ndm),ndm) or YBq z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm), where q=1 to NB. When the number of multi-beams is two (NB=2), q=1 or 2.

[0327] The received signal Y z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) is the coded Doppler phase rotation amount ψ ndop_code(ndm), ndm Since the received signals are from the transmitting antennas using (m), they can be associated with the transmitting antennas Tx#1, Tx#2, . . . , Tx#Nt.

[0328] Therefore, in the following, the received signal Y z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) ndop_code(ndm), ndm For (m), the notation YT corresponding to one of the transmitting antennas Tx#1 to Tx#Nt is z (f b_cfar ,f s_comp_cfar , nt) is used, where nt = 1 to Nt.

[0329] Similarly, the received signal YBq z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) ndop_code(ndm), ndm For (m), the notation YBT corresponding to one of the transmitting antennas Tx#1 to Tx#Nt is z (f b_cfar ,f s_comp_cfar , nt) are used, where nt=1 to Nt and q=1 to NB. When the number of multi-beams is two (NB=2), q=1 or 2.

[0330] Hereinafter, operation example 1 and operation example 2 of the direction estimation unit 213 will be described.

[0331] <Operation Example 1 of Direction Estimation Unit 213> In the first operation example, for example, the direction estimation unit 213 calculates a distance index f b_cfar and the received signal Y after coded Doppler demultiplexing processing z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm), the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ) is generated and direction estimation processing is performed.

[0332] Here, the information input from the coded Doppler demultiplexing unit 212 is the received signal Y z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm), the coded Doppler demultiplexed received signals for the Nt transmitting antennas are included. Therefore, the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ) includes Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na, as shown in equation (14). The direction estimator 213 calculates the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ) 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.

number

[0333] In equation (14), h cal[b] is an array correction value that corrects the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas. b is an integer between 1 and (Nt×Na).

[0334] The direction estimation unit 213 calculates, for example, a virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ) to obtain the direction estimation evaluation function P H (θ u , f b_cfar , f s_comp_cfar ) in the azimuth direction θ u is varied within a predetermined angle range to calculate a spatial profile.

[0335] The direction estimating section 213 may extract a predetermined number of maximum peaks from the calculated spatial profile in descending order, and output the azimuth direction of the maximum peak as an arrival direction estimate (for example, positioning output).

[0336] In addition, the direction estimation evaluation function value P H (θ u , f b_cfar , f s_comp_cfar There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0337] In the above example, the direction estimation unit 213 calculates the azimuth direction as the arrival direction estimated value, but the present invention is not limited to this example. The direction estimation unit 213 can estimate the arrival direction in the elevation direction, or estimate the arrival direction in the azimuth direction and the elevation direction by using MIMO antennas arranged in a rectangular grid. For example, the direction estimation unit 213 can calculate the azimuth direction and the elevation direction as the arrival direction estimated value for each transmitting antenna with a different beam direction, and output the calculated values ​​as the positioning output. The same application is possible in the operation example 2 of the direction estimation unit 213 described later.

[0338] Through the above operations, the direction estimator of the radar device 10 outputs, for example, a distance index f b_cfar and the received signal Y after coded Doppler demultiplexing processing z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) as a positioning output.b_cfar , and a Doppler frequency estimate of the target.

[0339] Also, the distance index f b_cfar 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.

[0340] In addition, information input from the coded Doppler demultiplexing unit 212 (for example, distance index f b_cfar , and the received signal Y z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm)), the direction estimator 213 may calculate arrival direction estimates for them in the same manner as in the above-mentioned processing, and output the positioning result.

[0341] <Operation Example 2 of Direction Estimation Unit 213> In the second operation example, for example, the direction estimation unit 213 calculates the distance index f b_cfar and the received signal YBq after coded Doppler demultiplexing processing z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm), the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm) is generated, and direction estimation processing is performed based on the received signal from the transmitting antenna in the beam direction Bq.

[0342] Here, q = 1 to NB. For example, when the number of multi-beams NB = 2, q = 1 or 2. Below, as an example, the operation when NB = 2 will be described, but the value of NB is not limited to this.

[0343] The direction estimation unit 213 estimates the received signal YBq after the coded Doppler demultiplexing process. z (f b_cfar ,f s_comp_cfar, ndop_code(ndm), ndm) is matched with the beam direction Bq, and direction estimation processing is performed.

[0344] Here, the information input from the coded Doppler demultiplexing unit 212 is the received signal YBq that has been subjected to coded Doppler demultiplexing processing. z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm), the coded Doppler demultiplexed received signals for Nt transmit antennas are included, but N Bq Since no received signals are obtained other than the coded Doppler multiplexed separated signals for the transmitting antennas, signals with zero values ​​are included. Therefore, the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar ) includes Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na, as shown in equation (15). The direction estimator 213 calculates the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar ) 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.

number

[0345] For example, the transmitting antennas in the beam direction B1 are Tx#1 and Tx#3, the transmitting antennas in the beam direction B2 are Tx#2 and Tx#4, and N B1 =2, N B2 =2, N t = 4, and when the number of receiving antennas Na = 4, the B1 beam antenna extraction vector SP B1 , and the B2 beam antenna extraction vector SP for extracting the received signal corresponding to the transmitting antenna in the beam direction B2 B2 is expressed as 16(=N t × Na) may be represented as the following column vector, where the superscript T denotes vector transpose:

number

number

[0346] The direction estimation unit 213 estimates, for example, the B1 beam antenna extraction vector SP B1 Using the element index where the element of is 1, the virtual receiving array correlation vector h1(f b_cfar , f s_comp_cfar ) and sort the element indexes in ascending order to obtain a column vector, which is called the virtual receiving array correlation vector h B1 (f b_cfar , f s_comp_cfar For example, the B1 beam antenna extraction vector SP B1 In this case, the elements in the first to fourth and ninth to twelfth element indexes are 1. In this case, the direction estimator 213 calculates the virtual receiving array correlation vector h1(f b_cfar , f s_comp_cfar ) in the order of the 1st to 4th and 9th to 12th element indexes, and the B1 beam antenna virtual receiving array correlation vector h B1 (f b_cfar , f s_comp_cfar )

[0347] Similarly, the direction estimation unit 213 calculates, for example, the B2 beam antenna extraction vector SP B2 Using the element index where the element of is 1, the virtual receiving array correlation vector h2(f b_cfar , f s_comp_cfar ) and sort the element indexes in ascending order to obtain a column vector, which is called the virtual receiving array correlation vector h B2 (f b_cfar , f s_comp_cfar For example, the B2 beam antenna extraction vector SP B2In this case, the elements in the fifth to eighth and thirteenth to sixteenth element indexes are 1. In this case, the direction estimator 213 calculates the virtual receiving array correlation vector h2(f b_cfar , f s_comp_cfar ) in the order of the 5th to 8th and 13th to 16th element indexes, and the B2 beam antenna virtual receiving array correlation vector h B2 (f b_cfar , f s_comp_cfar )

[0348] The direction estimation unit 213 calculates, for example, a beam antenna virtual receiving array correlation vector h Bq (f b_cfar , f s_comp_cfar ) to obtain the direction estimation evaluation function P H-Bq (θ u , f b_cfar , f s_comp_cfar ) in the azimuth direction θ u is varied within a predetermined angle range to calculate the spatial profile of each Bq beam, where q=1 or 2.

[0349] The direction estimation unit 213 may extract a predetermined number of maximum peaks in a spatial profile based on a received signal corresponding to a transmitting antenna of the calculated beam direction Bq in descending order, and output the azimuth direction of the maximum peak as an arrival direction estimate (e.g., positioning output) by the Bq beam.

[0350] In addition, the direction estimation evaluation function value P H-Bq (θ u , f b_cfar , f s_comp_cfar There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

[0351] Through the above operations, the direction estimator 213 of the radar device 10 outputs, for example, a distance index f b_cfar , the received signal YB, which is a signal received from a transmitting antenna with a beam direction Bq and has been subjected to coded Doppler demultiplexing processing z (f b_cfar ,fs_comp_cfar , ndop_code(ndm), ndm), the direction estimator 213 may output an estimated value of the direction of arrival by the Bq beam. In addition, the direction estimator 213 may further output a distance index f b_cfar , and a Doppler frequency estimate of the target.

[0352] In addition, information input from the coded Doppler demultiplexing unit 212 (for example, distance index f b_cfar , and the received signal YBq after coded Doppler demultiplexing processing z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm)), the direction estimator 213 may calculate arrival direction estimates for them in the same manner as in the above-mentioned processing, and output the positioning result.

[0353] Operation example 1 and operation example 2 of direction estimation unit 213 have been described above.

[0354] Next, an example of the arrangement of the MIMO antennas and an example of the operation of the direction estimation unit 213 when the example of the arrangement of the MIMO antennas is used will be described. Note that, hereinafter, the transmitting antennas and the receiving antennas in the MIMO radar are collectively referred to as MIMO antennas.

[0355] In the following description, each transmitting antenna included in the transmitting antenna unit 109 may have a sub-array configuration in which a plurality of planar patch antennas are arranged vertically and horizontally, as shown in FIG. 17. In the example of FIG. 17, the transmitting antenna is composed of eight planar patch antennas in the vertical direction and four planar patch antennas in the horizontal direction. For example, by changing the feed phase for each patch antenna included in one transmitting antenna, it is possible to form a beam pattern (transmitting antenna element pattern) that directs a directional beam in a desired direction. Also, for example, the more planar patch antennas in the horizontal (or vertical) direction that constitute one transmitting antenna, the sharper the directional beam in the horizontal (or vertical) direction can be formed. One transmitting antenna may be composed of, for example, the number of planar patches that satisfies a desired beam width.

[0356] The configuration of one transmitting antenna is not limited to the example shown in Fig. 17, and the number of patch antennas constituting one transmitting antenna (for example, at least one of the total number, the number in the horizontal direction, and the number in the vertical direction) is not limited to the number shown in Fig. 17. Also, one transmitting antenna is not limited to a planar patch antenna, and may be configured with patch antennas arranged in either the vertical direction or the horizontal direction. Also, for example, the configurations of the patch antennas of each of the multiple transmitting antennas may be different.

[0357] In the following, as an example, an arrangement example of MIMO antennas in which two transmission antennas correspond to each transmission beam will be described. Each transmission beam may be formed by, for example, two transmission antennas.

[0358] In the following, as an example, an antenna arrangement of a MIMO radar with the number of transmitting antennas Nt=4 (for example, Tx#1 to Tx#4) and the number of receiving antennas Na=3 (for example, Rx#1 to Rx#3) will be described.

[0359] For example, as shown in Fig. 18 or 19, transmitting antennas Tx#1 to Tx#4 have directivity patterns with different transmitting beam directions (or directional beam directions). In Fig. 18 and 19, Tx#1 and Tx#2 have a directivity pattern of beam direction B1 (beam B1), and Tx#3 and Tx#4 have a directivity pattern of beam direction B2 (beam B2). As shown in Fig. 18 and 19, the number of transmitting antennas having directivity patterns of beam direction B1 and beam direction B2, respectively, is two, and N B1 =2, N B2 =2.

[0360] In the following description, the directivity of the receiving antennas (for example, Rx#1 to Rx#3) may be omnidirectional or may have a substantially uniform directivity characteristic within the viewing angle of the transmitting antennas (for example, Tx#1 to Tx#4) with multiple beam directions.

[0361] For example, when the number of transmitting antennas used for multiplex transmission is Nt=4, the radar device 10 sets the coded Doppler phase rotation amount in the phase rotation amount setting unit 105 to a coded Doppler multiplexed signal (Doppler multiplex number N DM =3, code multiplex number N CM = 2) to transmit the radar transmission signal. In this case, for example, in the setting of the Doppler shift amount described above, N B1 =2, N B2 =2 Doppler multiplex signal allocation can be applied.

[0362] Also, for example, the arrangement of the transmitting antennas Tx#1 to Tx#4 and the receiving antennas Rx#1 to Rx#3 constitutes the arrangement VA#1 to VA#12 of virtual receiving antennas (or MIMO virtual antennas).

[0363] Here, the arrangement of the virtual receiving antenna (virtual receiving array) may be expressed, for example, as in the following equation (18) based on the position (e.g., the position of the feed point) of the transmitting antenna constituting the transmitting antenna section 109 and the position (e.g., the position of the feed point) of the receiving antenna constituting the receiving antenna section 202.

number

[0364] Here, the position coordinates of a transmitting antenna (for example, Tx#n) constituting the transmitting antenna unit 109 are expressed as (X T_#n ,Y T_#n ) (for example, n=1 to Nt), and the position coordinates of the receiving antenna (for example, Rx#z) constituting the receiving antenna unit 202 are represented as (X R_#z ,Y R_#z ) (for example, z=1 to Na), and the position coordinates of the virtual antenna VA#b that constitutes the virtual receiving array antenna are expressed as (X V_#b ,Y V_#b ) (for example, b = 1 ~ Nt × Na).

[0365] In addition, in equation (18), for example, VA#1 is expressed as the position reference (0,0) of the virtual receiving array.

[0366] Below, we will explain an example of the arrangement of MIMO antennas. T_#n represents the horizontal position coordinate, and Y T_#n Here, the description will be given assuming that the coordinate represents a position coordinate in the vertical direction, but the present invention is not limited to this.

[0367] Figures 18 and 19 show examples of the arrangement of transmitting antennas and receiving antennas (MIMO antenna arrangements) used in a MIMO radar. Hereinafter, the example of the MIMO antenna arrangement shown in Figure 18 is referred to as "arrangement example A," and the example of the MIMO antenna arrangement shown in Figure 19 is referred to as "arrangement example B." (a) of Figures 18 and 19 shows an example of the arrangement of MIMO antennas (Tx#1 to Tx#4, Rx#1 to Rx#3), and (b) of Figures 18 and 19 shows an example of the arrangement of virtual receiving antennas (VA#1 to VA#12) configured by the MIMO antenna arrangement of (a) of Figures 18 and 19.

[0368] As shown in (a) of Fig. 18 and Fig. 19, in Arrangement Example A and Arrangement Example B, receiving antennas Rx#1 to Rx#3 are arranged at intervals of Dr in the horizontal direction (horizontal direction in Fig. 18 and Fig. 19). In addition, in Arrangement Example A and Arrangement Example B, transmitting antennas Tx#1 and Tx#2 corresponding to beam direction B1 are arranged at intervals of Dr (Dt=Dr) in the horizontal direction, and arranged at different positions (for example, intervals of Dv) in the vertical direction (vertical direction in Fig. 18 and Fig. 19). In addition, in Arrangement Example A and Arrangement Example B, transmitting antennas Tx#3 and Tx#4 corresponding to beam direction B2 are arranged at intervals of Dt in the horizontal direction, and arranged at different positions (for example, intervals of Dv) in the vertical direction. Also, as shown in Figures 18 and 19(a), the transmitting antennas Tx#1 and Tx#3 (or Tx#2 and Tx#4) are arranged at the same position in the vertical direction and are arranged horizontally at a distance greater than the apertures (2Dr) of the receiving antennas Rx#1 to Rx#3 (for example, a distance of 3Dr).

[0369] For example, in the arrangement of the transmitting antennas Tx#1 to Tx#4 shown in (a) of FIG. 18 and FIG. 19 (X T_#1 ,Y T_#1 )=(0,0),(X T_#2 ,Y T_#2)=(D r , D V ), (X T_#3 ,Y T_#3 )=(3D r , 0), (X T_#4 ,Y T_#4 )=(D t +3D r , D V ), and the arrangement of receiving antennas Rx#1 to Rx#3 (X R_#1 ,Y R_#1 )=(ax,ay),(X R_#2 ,Y R_#2 )=(ax+D r ,ay),(X R_#3 ,Y R_#3 )=(ax+2D r In the case where ax, ay, the position coordinates of virtual antennas VA#1 to VA#12 that configure the virtual receiving antenna are calculated by equation (18), where ax and ay are arbitrary constants.

[0370] For example, as shown in FIG. 18 and FIG. 19(b), the position coordinates of the virtual antennas VA#1 to VA#12 are expressed as (X V_#1 ,Y V_#1 )=(0,0), (X V_#2 ,Y V_#2 )=(D r , 0), (X V_#3 ,Y V_#3 )=(2D r , 0), (X V_#4 ,Y V_#4 )=(D t ,D V ), (X V_#5 ,Y V_#5 )=(D t +D r , D V ), (X V_#6 ,Y V_#6 )=(D t +2D r , D V ), (X V_#7 ,Y V_#7 )=(3D r , 0), (X V_#8 ,Y V_#8 )=(4D r , 0), (X V_#9 ,YV_#9 )=(5D r , 0), (X V_#10 ,Y V_#10 )=(D t +3D r ,D V ), (X V_#11 ,Y V_#11 )=(D t +4D r , D V ), (X V_#12 ,Y V_#12 )=(D t +5D r , D V )

[0371] Here, Arrangement example A (FIG. 18) shows an arrangement example using Dt=Dr. Arrangement example B (FIG. 19) shows an arrangement example using Dr and Dt where the absolute value of the difference between Dt and Dr is about 0.5 wavelengths (|Dt-Dr| ≈ 0.5). For example, FIG. 19 shows an arrangement example where Dt=1.5Dr, and an example where Dt-Dr=Dr / 2. This is an arrangement where, for example, assuming Dt=1.5 wavelengths and Dr=1 wavelength, Dt-Dr=Dr / 2=0.5 wavelengths.

[0372] For example, in the above-described operation example 1 of the direction estimation unit 213, the direction estimation unit 213 receives information from the coded Doppler demultiplexing unit 212 and converts the information into the coded Doppler demultiplexed received signal Y z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm), the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ) is generated and direction estimation processing is performed.

[0373] Here, the received signal by the b-th virtual antenna VA#b is expressed by the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ), where b is an integer between 1 and (Nt×Na).

[0374] Also, the coded Doppler demultiplexing process is performed on the received signal Y z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) includes coded Doppler separated signals for Nt transmitting antennas. This is the case where the target direction is, for example, target direction (2) shown in FIG. 10, and corresponds to an area where the beam directions of the transmitting antennas Tx#1 to Tx#4 overlap. In this case, the radar transmission signals from the transmitting antennas Tx#1 to Tx#4 are reflected by the target and received by the receiving antennas Rx#1 to Rx#3. Therefore, in this case, the direction estimation unit 213 can perform direction estimation using the received signals of the virtual antennas VA#1 to VA#12 corresponding to Tx#1 to Tx#4.

[0375] In the MIMO antenna arrangements in FIG. 18 and FIG. 19(a), Tx#1 and Tx#2 have directional characteristics of beam direction B1, and Tx#3 and Tx#4 have directional characteristics of beam direction B2, and correspond to different beam directions. Also, as shown in FIG. 10, beam direction B1 and beam direction B2 overlap in an angle region within about the beam width. Here, as shown in FIG. 18 and FIG. 19(a), the arrangements of Tx#1 and Tx#2 and the arrangements of Tx#3 and Tx#4 are offset in the vertical direction (for example, offset value Dv), and the direction estimation unit 213 is capable of measuring angles in the vertical direction in addition to the horizontal direction. In addition, the arrangement of Tx#1 and Tx#2, and the arrangement of Tx#3 and Tx#4 are each an arrangement that can expand the aperture length of the virtual receiving antenna in the horizontal direction when a target exists in the overlapping area between beam directions B1 and B2 (for example, target direction (2) shown in Figure 10), and can improve the horizontal estimation accuracy and angular resolution in the angle measurement process of the direction estimation unit 213.

[0376] In addition, in the arrangement example A, as shown in the arrangement of Tx#1 and Tx#2 (or the arrangement of Tx#3 and Tx#4) shown in FIG. 18(a), the offset Dt in the horizontal direction is Dt=Dr. In this way, Tx#1 and Tx#2 (or Tx#3 and Tx#4) are arranged in the horizontal direction with an offset at an element interval equal to the element interval Dr of the receiving antennas Rx#1 to Rx#3. For this reason, as shown in FIG. 18(b), the virtual receiving antenna arrangement includes an arrangement in which the horizontal positions of multiple virtual antennas (for example, VA#2 and VA#4, or VA#3 and VA#5) match, but the vertical positions differ by Dv. With such an arrangement of the virtual receiving antennas, the direction estimation unit 213 can easily measure the vertical angle based on, for example, the reception phase difference between two virtual antennas (for example, VA#2 and VA#4, or VA#3 and VA#5) whose horizontal positions match.

[0377] Moreover, the arrangement example B is an arrangement using Dr and Dt such that the absolute value of the difference between Dt and Dr is about 0.5 wavelengths (|Dt-Dr| ≈ 0.5), as shown in the arrangement of Tx#1 and Tx#2 (or the arrangement of Tx#3 and Tx#4) in FIG. 19(a). With this arrangement, for example, as shown in FIG. 19(b), the distance between virtual antennas VA#2 and VA#4 (or the distance between VA#3 and VA#5, the distance between VA#7 and VA#6, the distance between VA#8 and VA#10, and the distance between VA#9 and VA#11) is Dt-Dr when Dt>Dr, and is Dr-Dt when Dr>Dt. For example, when the absolute value |Dt-Dr| of the difference between the transmitting antenna distance Dt and the receiving antenna distance Dr is set to a half wavelength, the radar device 10 can suppress grating lobes within a viewing angle range of ±90°. For example, when Dt=1.5λ and Dr=1λ, |Dt-Dr|=0.5λ.

[0378] Although the case has been described where the difference between Dt and Dr, |Dt-Dr| (prescribed value), is set to half the wavelength (0.5λ), this is not limiting and, for example, |Dt-Dr| may be set to any value in the range of approximately 0.45λ to 0.8λ (for example, any value in the range of 0.5 to 0.8 times the wavelength of the radar transmission signal).

[0379] For example, |Dt-Dr| may be set according to the horizontal viewing angle of the radar device 10, and grating lobes within the viewing angle can be suppressed. For example, when the horizontal viewing angle is a wide viewing angle in the range of about ±70 degrees to ±90 degrees, |Dt-Dr| may be set to about 0.5λ. Or, when the horizontal viewing angle is a narrow viewing angle in the range of about ±20 degrees to ±40 degrees, |Dt-Dr| may be set to a wider interval, for example, about 0.7λ.

[0380] In the above-described second operation example of the direction estimator 213, the direction estimator 213 receives the coded Doppler demultiplexed received signal YB1 from the coded Doppler demultiplexer 212. z (f b_cfar ,f s_comp_cfar ,ndop_code(ndm),ndm), or YB2 z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm) based on the virtual receiving array correlation vector h B1 (f b_cfar , f s_comp_cfar ), or h B2 (f b_cfar , f s_comp_cfar ) is generated and direction estimation processing is performed.

[0381] Here, the received signal by the b-th virtual antenna VA#b is expressed by the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar ), where q=1 or 2.

[0382] Also, the coded Doppler demultiplexing process is performed on the received signal YBq input from the coded Doppler demultiplexing unit 212. z (f b_cfar ,f s_comp_cfar ,ndop_code(ndm),ndm) is N BqThe received signals for the transmitting antennas in beam direction Bq are included. This is the case where the target direction is, for example, target direction (1) (e.g., in the case of beam direction B1) or target direction (3) (e.g., in the case of beam direction B2) shown in Fig. 10, and corresponds to the area of ​​beam direction Bq. In this case, the radar transmission signal from the transmitting antenna in beam direction Bq is reflected by the target and received by the receiving antennas Rx#1 to Rx#3.

[0383] Therefore, in this case, for example, when q=1 (when the target direction is target direction (1) shown in FIG. 10), the direction estimation unit 213 performs direction estimation using the reception signals of virtual antennas VA#1 to VA#6 corresponding to transmitting antennas Tx#1 and Tx#2 included in beam direction B1. Also, for example, when q=2 (when the target direction is target direction (3) shown in FIG. 10), the direction estimation unit 213 performs direction estimation using the reception signals of virtual antennas VA#7 to VA#12 corresponding to transmitting antennas Tx#3 and Tx#4 included in beam direction B2.

[0384] In the arrangement example A, Dt and Dr may be set to, for example, one wavelength or more in (a) of FIG. 18. In this case, as a result of the direction estimation process in the direction estimation unit 213, grating lobes may occur, and ambiguity may occur in the direction estimation in the horizontal direction. On the other hand, the direction estimation unit 213 estimates the received signal Y z (f b_cfar ,f s_comp_cfar ,ndop_code(ndm),ndm),YB1 z (f b_cfar ,f s_comp_cfar ,ndop_code(ndm),ndm), or YB2 z (f b_cfar ,f s_comp_cfar , ndop_code(ndm), ndm). As a result, the direction estimation unit 213 can specify that the target is in any of the beam direction B1, the beam direction B2, and the direction of the overlapping area between the beam directions B1 and B2, so that the true direction can be detected even if a grating lobe occurs.

[0385] Furthermore, Dv in each of the arrangement examples A and B may be set to a value of, for example, about 0.45λ to 0.8λ (for example, any value in the range of 0.5 to 0.8 times the wavelength of the radar transmission signal). Dv may be set, for example, according to the vertical viewing angle of the radar device 10. For example, when the vertical viewing angle is a wide viewing angle in the range of about ±70 degrees to ±90 degrees, Dv may be set to about 0.5λ. Alternatively, when the vertical viewing angle is a narrow viewing angle in the range of about ±20 degrees to ±40 degrees, Dv may be set to a wider interval, for example, about 0.7λ.

[0386] Here, λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, if a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency in the frequency sweep band of the chirp signal.

[0387] In the arrangement examples A and B, the receiving antennas (Rx#1 to Rx#3) are arranged in the same vertical position and offset by equal intervals Dr in the horizontal direction, but the arrangement of the receiving antennas is not limited to this. For example, the intervals between the receiving antennas in the horizontal direction may be unequal.

[0388] Moreover, the MIMO antenna arrangements described in Arrangement Example A and Arrangement Example B are merely examples and are not limiting. For example, a configuration in which another antenna (at least one of a transmitting antenna and a receiving antenna) is further arranged in addition to the MIMO antenna arrangements described in Arrangement Example A and Arrangement Example B may be adopted. Also, an antenna arrangement in which the horizontal direction and the vertical direction are interchanged in Arrangement Example A and Arrangement Example B may be adopted. Also, the spacing between the transmitting antennas described in Arrangement Example A and Arrangement Example B may be applied to the spacing between the receiving antennas, and the spacing between the receiving antennas described in Arrangement Example A and Arrangement Example B may be applied to the spacing between the transmitting antennas.

[0389] By the above-mentioned operation, the direction estimation unit 213 can perform direction estimation processing in response to the fact that the separation operation of the coded Doppler multiplex separation unit 212 differs depending on the target direction in multi-beam transmission.

[0390] For example, when the coded Doppler multiplex separation unit 212 is capable of separating the Doppler multiplexed signals from all transmitting antennas (e.g., in the case of target direction (2)), the direction estimation unit 213 can improve the angle measurement accuracy and angle measurement resolution by performing direction estimation using received signals from Nt×Na virtual receiving antennas.

[0391] Also, for example, when the coded Doppler multiplexing separation unit 212 can separate the Doppler multiplexed signal from the transmitting antenna in the beam direction Bq (for example, in the case of the target direction (1) or (3)), the direction estimation unit 213 estimates N Bq By performing direction estimation using received signals from ×Na virtual receiving antennas, it is possible to improve the angle measurement accuracy and angle measurement resolution.

[0392] An example of the operation of the direction estimator 213 has been described above.

[0393] As described above, in this embodiment, the radar device 10 assigns different coded Doppler multiplexed signals (e.g., signals with different at least one of Doppler multiplexing pattern and code multiplexing pattern) between multi-beams that satisfy at least condition 1 in the phase rotation amount setting unit 105 in a multi-beam transmission MIMO radar using coded Doppler multiplexing. As a result, even if the reception levels of reflected waves corresponding to transmitting antennas with different directional characteristics differ greatly, the radar device 10 can distinguish the transmitting antennas in the coded Doppler multiplexing separation unit 212, and can perform coded Doppler multiplexing 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.

[0394] Furthermore, for example, when the phase rotation setting unit 105 satisfies the above-mentioned conditions 1 and 2 in allocating the coded Doppler multiplexed signal, in the radar device 10, even if the reception levels of reflected waves corresponding to transmitting antennas having different directional characteristics differ significantly, the detectable Doppler frequency range fd is in the range of -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.

[0395] Furthermore, in the radar device 10 of this embodiment, as a multi-beam transmission / reception MIMO radar configuration, Doppler demultiplexing is possible without using beam direction determination processing using a directional receiving antenna (or directional receiving processing using a receiving array antenna), thereby reducing the amount of calculation required for receiving processing.

[0396] Furthermore, for example, when receiving antennas with different beam directions are used as receiving antennas in a multi-beam transmission / reception MIMO radar configuration, the number of receiving antennas available for angle measurement may decrease depending on the target direction, which may result in a decrease in the angle measurement accuracy or angle measurement resolution of the radar device 10. In this embodiment, for example, Doppler demultiplexing is possible regardless of the target direction without using a directional receiving antenna, so that the decrease in angle measurement accuracy and angle measurement resolution can be suppressed.

[0397] Therefore, according to this embodiment, it is possible to improve the detection performance of a multi-beam transmission MIMO radar using coded Doppler multiplexing transmission.

[0398] (Variation 1) In the above embodiment, the case where the number of multibeams NB is 2 has been described, but the number of multibeams NB may be equal to or greater than 3. In Modification 1, the case where the number of multibeams NB is equal to or greater than 3 will be described.

[0399] When the number of multi-beams NB is 3 or more, the coded Doppler phase rotation amount set by the phase rotation amount setting unit 105 applies conditions 1-a and 1-b described below instead of the above-mentioned condition 1, which makes it possible to separate Doppler multiplexed signals and suppress deterioration of positioning performance and radar detection performance, even when the received power levels of reflected waves differ significantly between received signals from transmitting antennas with different beam directions, as in the above-mentioned embodiment.

[0400] An example of the conditions for setting the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 when the number of multibeams NB is 3 or more will be described below.

[0401] For example, in the transmitting antenna unit 109, the transmitting antennas having Q different beam directions Bq are each denoted by (N B1 ,N B2 ,~,N BQ For example, the phase rotation amount setting unit 105 of the radar transmitter 100 in a MIMO radar (e.g., the radar device 10) that transmits multiple beams determines the number of coded Doppler multiplexing signals N DOP_CODE (ndm) is set to be non-uniform, and the coded Doppler phase rotation amount ψ is set to satisfy the following <Condition 1-a> and <Condition 1-b>. ndop_code(ndm), ndm Set (m), where ndm=1~N DM and ndop_code(ndm)=1~N DOP_CODE (ndm).

[0402] <Condition 1-a> The phase rotation amount setting unit 105 determines, for each transmitting antenna in each beam direction Bq, an encoded Doppler phase rotation amount ψ that satisfies different Doppler multiplexing pattern conditions, different code multiplexing pattern conditions, or different patterns of Doppler multiplexing and code multiplexing. ndop_code(ndm), ndm Set (m), where q = 1 to Q.

[0403] <Condition 1-b> When there is an overlapping viewing angle region between each beam direction Bq, the phase rotation amount setting unit 105 determines an encoded Doppler phase rotation amount ψ that satisfies different code multiplexing pattern conditions or different patterns of Doppler multiplexing and code multiplexing conditions, including a set of multiple transmitting antennas (hereinafter referred to as a "transmitting antenna set") included in the overlapping region (or referred to as an overlapping beam region). ndop_code(ndm), ndm Set (m), where q = 1 to Q.

[0404] The code and Doppler multiplexed signals assigned to the transmitting antennas of each beam Bq and the transmitting antenna sets included in the overlapping region satisfy at least one of the following conditions.

[0405] For example, the different Doppler multiple pattern condition may be any one of the following conditions (eg, also referred to as condition 1A-a): (A-1) The Doppler multiplexing number corresponding to each beam direction is the same, and each beam direction includes a different Doppler interval (however, N DM_Bq ≧2). (A-2) The number of Doppler multiplexes varies for each beam direction. (A-3) When the number of Doppler multiplexes is 3 or more, if the same Doppler intervals are included in the Doppler shift intervals for each beam direction, the order of the Doppler intervals is different (cyclic mismatch).

[0406] Furthermore, the different code multiplexing pattern condition may be any one of the following conditions (for example, also referred to as condition 1B-a). (B-1) The code intervals (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).

[0407] Here, when the number of multibeams NB ≥ 3, the number of transmitting antennas Nt ≥ 4, the number of Doppler multiplexing N DM ≧2, maximum code multiplex number N CM ≧2, Nt <N DM ×N CM In addition, the number of transmitting antennas in the beam direction Bq is NBq It is written as N Bq ≧1, and the total number of transmitting antennas in each beam direction Bq is Nt (N B1 + N B2 + ~ + N BQ =Nt ) The Doppler multiplexing number N assigned to the transmitting antenna in the beam direction Bq is DM_Bq It is written as N DM_Bq <N DM It is.

[0408] In addition, the transmitting antennas with Q different beam directions Bq are each (N B1 ,N B2 ,~,N BQ In a MIMO radar (e.g., radar device 10) that transmits multiple beams using multiple Doppler elements, the phase rotation amount setting unit 105 of the radar transmitter 100 sets the coded Doppler phase rotation amount ψ so as to satisfy the following conditions 2-a and 2-b in addition to conditions 1-a and 1-b. ndop_code(ndm), ndm (m) may be set.

[0409] <Condition 2-a> The signals transmitted from the transmitting antenna of each beam Bq are multiplexed by a code multiplexing number that is uneven between the Doppler multiplexed signals, and the code multiplexing number is from 1 to N CM It is in the range of -1 or less, where q = 1 to Q.

[0410] <Condition 2-b> When there is an overlapping beam area between each beam Bq, the signals transmitted from the transmitting antenna set included in the overlapping beam area are multiplexed by a code multiplexing number that is uneven between the Doppler multiplexed signals, and the code multiplexing number is 1 or more and N CM It is in the range of -1 or less.

[0411] By setting the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 to satisfy conditions 2-a and 2-b in addition to conditions 1-a and 1-b, the Doppler detection range detectable by the radar device 10 can be expanded to a range equivalent to that in the case of one transmitting antenna (for example, a range of ±1 / (2Tr)), as in the above embodiment. Also, even if conditions 1-a and 1-b are satisfied but conditions 2-a and 2-b are not satisfied, the Doppler detection range of the equal-interval DDM (for example, -1 / (2 N t Tr)≦fd < 1 / (2 N t The Doppler detection range can be expanded more than with the conventional radar.

[0412] An example of the operation of the radar device 10 will now be described.

[0413] <Example 1> In the operation example 1, the number of multi-beams NB=3, and no overlapping beam regions are included between each beam direction Bq.

[0414] For example, Fig. 20 shows an example of beam patterns of transmitting antennas in beam directions B1, B2, and B3 when the number of multi-beams NB = 3. As shown in Fig. 20, when there is no (or only a small) overlapping portion in the beam patterns of the transmitting antennas in each beam direction, Condition 1-a and Condition 2-a may be applied.

[0415] 20, when the target direction is any one of beam direction B1, beam direction B2, and beam direction B3, the allocation of the Doppler multiplexed signal by the Doppler shift setting unit 106 may satisfy condition 1-a. This enables the radar device 10 to distinguish, in the coded Doppler multiplexing separation unit 212, a case in which the reception level of the reception signal corresponding to the transmitting antenna of beam direction B1 decreases, a case in which the reception level of the reception signal corresponding to the transmitting antenna of beam direction B2 decreases, and a case in which the reception level of the reception signal corresponding to the transmitting antenna of beam direction B3 decreases.

[0416] Furthermore, if it is determined from this determination result that the signal is a reception signal of a transmitting antenna in beam direction B1 (or B2, B3), the assignment of the coded Doppler phase rotation amount in the phase rotation amount setting unit 105 satisfies condition 2-a, and thus the coded Doppler multiplexed signal for the transmitting antenna in beam direction B1 (or B2, B3) can be separated using the operation of an existing coded Doppler multiplexed signal separation unit. By such operation of the coded Doppler multiplex separation unit 212, 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 an output in which the transmitting antenna is associated with each coded Doppler multiplexed signal.

[0417] <Example 2> In the operation example 2, the number of multi-beams NB=3, and overlapping beam regions are included between each beam direction Bq.

[0418] For example, Fig. 21 shows an example of beam patterns of transmitting antennas with beam directions B1, B2, and B3 when the number of multi-beams NB = 3. As shown in Fig. 21, when the beam patterns of the transmitting antennas in each beam direction include overlapping parts (overlapping beam areas), Condition 1-a, Condition 1-b, Condition 2-a, and Condition 2-b may be applied.

[0419] For example, in Fig. 21, when the target direction is a transmission beam direction B1, B2, or B3 outside the overlapping beam range (target direction (1), (3), or (5) in Fig. 21), the allocation of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 may satisfy condition 1-a. This enables the radar device 10 to determine which of the transmitting antennas in the beam directions B1, B2, and B3 corresponds to the received signal in the coded Doppler demultiplexing unit 212.

[0420] 21, when the target direction is within the overlapping beam range (target direction (2) or (4) in FIG. 21), the allocation of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 may satisfy condition 1-a and condition 1-b. This enables the radar device 10 to determine which transmitting antenna of the beam directions B1, B2, and B3 the received signal corresponds to, and also enables the coded Doppler demultiplexing unit 212 to determine whether the received signal is from an overlapping beam region of the transmitting antennas of the beam directions B1 and B2, or from an overlapping beam region of the transmitting antennas of the beam directions B2 and B3.

[0421] Furthermore, if it is determined from this determination result that the received signal corresponds to the transmitting antenna of the beam direction B1 (or B2, B3), the assignment of the coded Doppler phase rotation amount in the phase rotation amount setting unit 105 satisfies condition 2-a, so that the coded Doppler multiplexed signal for the transmitting antenna of the beam direction B1 (or B2, B3) can be separated using the operation of an existing coded Doppler multiplexed signal separation unit. By such operation of the coded Doppler multiplex separation unit 212, the radar device 10 can determine the Doppler frequency fd of the target within the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output that associates the transmitting antenna with each coded Doppler multiplexed signal.

[0422] Furthermore, when it is determined that the received signal is from an overlapping beam region of the transmitting antennas of the beam directions B1 and B2 (or beam directions B2 and B3), the allocation of the coded Doppler multiplexed signal in the phase rotation amount setting unit 105 satisfies condition 2-b, so that the coded Doppler multiplexed signal for the transmitting antenna included in the overlapping beam region of the transmitting antennas of the beam directions B1 and B2 (or beam directions B2 and B3) can be separated using the operation of an existing coded Doppler multiplexed signal separation unit. By such operation of the coded Doppler multiplex separation unit 212, 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 in which the transmitting antenna is associated with each coded Doppler multiplexed signal.

[0423] An example of the operation of the radar device 10 has been described above.

[0424] Next, an example of setting the amount of coded Doppler phase rotation in phase rotation amount setting section 105 will be described.

[0425] In the following, a setting example (NB=3) of the coded Doppler phase rotation amount when condition 1 (eg, condition 1-a, condition 1-b) and condition 2 (eg, condition 2-a, condition 2-b) are satisfied will be described.

[0426] FIG. 22 shows the number of transmitting antennas, Nt=6, N B1 =2, N B2 =2, N B2 4 shows an example of how the coded Doppler phase rotation amount is set in phase rotation amount setting section 105 when .DELTA..times ...

[0427] In FIG. 22, Tx#1 and Tx#2 are transmitting antennas in beam direction B1, Tx#3 and Tx#4 are transmitting antennas in beam direction B2, and Tx#5 and Tx#6 are transmitting antennas in beam direction B3.

[0428] In addition, in FIG. 22, the Doppler multiplexing number N DM = 5, and the Doppler shift setting unit 106 may set five Doppler shift amounts DOP1 to DOP5 using, for example, the maximum equal interval Doppler shift amount setting shown in equation (5). In Fig. 22, the phase rotation amounts for giving Doppler shift amounts DOP1 = 0, DOP2 = Δfd, DOP3 = 2Δfd, DOP4 = -2Δfd, and DOP5 = -Δfd are φ1 = 0, φ2 = 2π / 5, φ3 = 4π / 5, φ4 = 6π / 5 (or φ4 = -4π / 5 may be used), and φ5 = 8π / 5 (or φ5 = -2π / 5 may be used). As shown in Fig. 22, the Doppler multiple intervals Δfd are equal, and Δfd = 1 / (10Tr).

[0429] In addition, in FIG. 22, 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 of the Walsh-Hadamard code.

[0430] In FIG. 22, the number of transmitting antennas is Nt=6, and the number of Doppler multiplexing is N DM =5, 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 DOP_CODE (ndm) can be set non-uniformly (where ndm=1~N DM ).

[0431] As shown in FIG. 22, in the encoding unit 107, the number of coded Doppler multiplexes for the Doppler multiplexed signals using the five Doppler shift amounts DOP1 to DOP5 input from the Doppler shift setting unit 106 is N DOP_CODE (1)=2, N DOP_CODE (2)=1, N DOP_CODE (3)=1, N DOP_CODE (4)=1, N DOP_CODE (5)=1. In this way, phase rotation amount setting section 105 non-uniformly sets the coded Doppler multiplexing numbers for the Doppler multiplexed signals.

[0432] In FIG. 22, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =5, for example, the Doppler multiplexed signals using the Doppler shift amounts DOP1 and DOP2 are assigned (N DM_B1 =2). Furthermore, the encoding unit 107 assigns Code2 and Code1 to the Doppler multiplexed signals using the Doppler shift amounts DOP1 and DOP2 assigned to the transmitting antennas Tx#1 and Tx#2 in the beam direction B1, respectively. For example, the phase rotation amount setting unit 105 sets the coded Doppler phase rotation amount ψ 2, 1 (m), ψ 1, 2 Set (m).

[0433] In FIG. 22, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =5, for example, Doppler multiplexed signals using Doppler shift amounts DOP4 and DOP5 are assigned (N DM_B2 =2). The encoding unit 107 also assigns Code1 and Code1 to the Doppler multiplexed signals using the Doppler shift amounts DOP4 and DOP5 assigned to the transmitting antennas Tx#3 and Tx#4 in the beam direction B2. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 1, 4 (m), ψ 1, 5 Set (m).

[0434] In FIG. 22, the Doppler shift setting unit 106 sets the Doppler multiplexing number N DM Of the Doppler multiplexed signals of =5, for example, Doppler multiplexed signals using Doppler shift amounts DOP1 and DOP3 are assigned (N DM_B3 =2). The encoding unit 107 also assigns Code1 and Code2 to the Doppler multiplexed signals using the Doppler shift amounts DOP1 and DOP3 assigned to the transmitting antennas Tx#5 and Tx#6 in the beam direction B2, respectively. For example, the phase rotation amount setting unit 105 assigns the coded Doppler phase rotation amount ψ 1, 1 (5), ψ 2, 3 Set (m).

[0435] In FIG. 22, the Doppler multiplexing number assigned by the Doppler shift setting unit 106 to each of the transmitting antennas of the beam directions B1, B2, and B3 is N DM_B1 =N DM_B2 =N DM_B3 = 2, which are the same. Therefore, the settings of the coded Doppler phase rotation amount shown in Fig. 22 do not match the different Doppler multiplex pattern condition of condition 1A-a.

[0436] On the other hand, in FIG. 22, the code indexes assigned to the transmitting antennas in the beam directions B1, B2, and B3 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 to DOP5 are CodeIndex_B1 = (2,1,*,*,*), CodeIndex_B2 = (*,*,*,1,1), and CodeIndex_B3 = (1,*,2,*,*), which results in a cyclic mismatch and the code index intervals are different, thereby satisfying condition 1B-a (B-1).

[0437] Also, in FIG. 22, the code multiplexing numbers assigned to the transmitting antennas in the beam directions B1, B2, and B3 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 to DOP5 are N_Code_B1 = (1,1,0,0,0), N_Code_B2 = (0,0,0,1,1), and N_Code_B3 = (1,0,1,0,0), which include code multiplexing numbers that result in cyclic consistency and are the same, so condition 1B-a (B-2) is not satisfied.

[0438] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit 210 observes the folded Doppler frequency. In this case, the code indexes are CodeIndex_B1_alias=(1,2,*,*,*), CodeIndex_B2_alias=(*,*,*,2,2) and CodeIndex_B3_alias=(2,*,1,*,*), which are different (cyclic mismatch). Therefore, in the example of FIG. 22, when the Doppler frequency of the target is in the range of -1 / (2Tr)≦fdtarget<-1 / (2Tr), the code indexes are cyclic mismatch and the code intervals are different. Therefore, the condition 1-a is satisfied, and the different code multiplexing pattern conditions are met.

[0439] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG. 22 are setting examples that satisfy condition 1-a.

[0440] 22, the code indexes assigned to the overlapping beam areas (transmitting antenna sets) of beam directions B1 and B2 and the overlapping beam areas (transmitting antenna sets) of beam directions B2 and B3 for each of the Doppler multiplexed signals using Doppler multiplexed signals DOP1 to DOP5 are CodeIndex_B1&B2=(2,1,*,1,1) and CodeIndex_B2&B3=(1,*,2,1,1), which are cyclically inconsistent. Also, even if CodeIndex_B1, CodeIndex_B2, and CodeIndex_B3 are included in addition to CodeIndex_B1&B2 and CodeIndex_B2&B3, the code index intervals are different (cyclically inconsistent), so condition 1-b is satisfied.

[0441] In addition, when the Doppler frequency of the target is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the Doppler analysis unit 210 observes the folded Doppler frequency. In this case, the code indexes are CodeIndex_B1&B2_alias=(1,2,*,2,2), CodeIndex_B2&B3_alias=(2,*,1,2,2), which are different (cyclic mismatch). Therefore, in the example of FIG. 22, when the Doppler frequency of the target is in the range of -1 / (2Tr)≦fdtarget<-1 / (2Tr), even if CodeIndex_B1_alias, CodeIndex_B2_alias, and CodeIndex_B3_alias are included, the code indexes are cyclic mismatch and the code INDEX intervals are different, so the condition 1-b is satisfied.

[0442] From the above, the settings of the coded Doppler phase rotation amounts shown in FIG. 22 are setting examples that satisfy condition 1-b.

[0443] In FIG. 22, the code multiplexing numbers assigned to each Doppler multiplexed signal in each transmitting antenna of beam directions B1, B2, and B3 are N_Code_B1=(1,1,0,0,0), N_Code_B2=(0,0,0,1,1), and N_Code_B3=(1,0,1,0,0). The Doppler multiplexed signals are multiplexed and transmitted with uneven code multiplexing numbers, 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 coded Doppler phase rotation amount shown in Fig. 22 is a setting example that satisfies condition 2-a.

[0444] In FIG. 22, the code multiplexing numbers assigned to each Doppler multiplexed signal in each transmitting antenna in the overlapping beam area of ​​beam directions B1 and B2 and the overlapping beam area of ​​beam directions B2 and B3 are N_Code_B1&B2=(1,1,0,1,1), N_Code_B2&B3=(1,0,1,1,1), and the Doppler multiplexed signals are multiplexed and transmitted with code multiplexing numbers that are uneven between the Doppler multiplexed signals. The code multiplexing number ranges from 1 to N. CM This is within the range of -1 or less. Therefore, the setting of the coded Doppler phase rotation amount shown in Fig. 22 is a setting example that satisfies condition 2-b.

[0445] Below, we will explain an example of the received signal at the output of the Doppler analysis unit 210 when the transmitting antenna unit 109 includes a transmitting antenna with different beam directions B1, B2, and B3 based on the setting of the Doppler shift amount shown in Figure 22, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna with approximately uniform directional characteristics within the field of view covered by both the transmitting antennas in beam direction B1 and beam direction B2).

[0446] For example, when the target direction is target direction (1), (3) or (5) shown in Fig. 21 (e.g., when the target exists around beam direction B1, B2 or B3), or when the target direction is target direction (2) or (4) (e.g., when the target exists around overlapping beam area B2&B3 or B2&B3), the code interval is different for the transmitting antenna of each beam direction and the transmitting antenna set of each overlapping beam direction. Therefore, the radar device 10 can determine, in the coded Doppler demultiplexing unit 212, a decrease in the reception level of a reception signal corresponding to a transmitting antenna included in any of beam directions B1, B2 or B3, or overlapping beam areas B2&B3 or B2&B3.

[0447] If the result of this determination indicates that the received signal is from a transmitting antenna in beam direction Bq or an overlapping beam area (for example, B2&B3 or B2&B3), the settings of the coded Doppler multiplexed signal for the transmitting antenna in beam direction Bq or the overlapping beam area (B2&B3 or B2&B3) are known, so the radar device 10 becomes able to separate the multiplexed signal by operations disclosed in, for example, Patent Documents 5 and 6.

[0448] Moreover, in the example of FIG. 22, the setting of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 satisfies the condition 2-a and the condition 2-b, so the detectable Doppler frequency range fd is in the range of −1 / (2 Tr)≦fd < 1 / (2 Tr) depending on the target direction, and the Doppler detection range can be expanded compared to the Doppler detection range of equal-interval Doppler multiplexing.

[0449] (Variation 2) In the above embodiment and modification, as shown in Fig. 10, Fig. 20 and Fig. 21, the beam directions of the multi-beams are different from each other, but the setting of the multi-beams (e.g., beam direction and beam width) is not limited to the above-mentioned example. For example, the beams constituting the multi-beams may differ in at least one of the beam direction and beam width. Also, the number of multi-beams NB may be 2 or more.

[0450] An example of multi-beam settings will now be described.

[0451] <Multi-beam setting example 1> In setting example 1, for example, as shown in Fig. 23, in multiple beams (e.g., beam directions B1, B2, and B3), the beam directions may be different from each other and the beam widths may be different. In multiple beams (e.g., beam directions B1, B2, and B3), the beam directions in the horizontal direction (or horizontal plane) may be different from each other and the beam widths in the horizontal direction (or horizontal plane) may be different. The beam directions in the vertical direction (or vertical plane) may be different from each other and the beam widths in the vertical direction (or vertical plane) may be different.

[0452] <Multi-beam setting example 2> In the above embodiment, as shown in Fig. 10, an example in which the beam direction differs in the horizontal direction (or horizontal plane) has been described, but the present invention is not limited to this. In setting example 2, for example, the beam direction may also differ in the vertical direction (or vertical plane).

[0453] For example, as shown in (a) of FIG. 24, in multiple beams (e.g., beam directions B1 and B2), each beam direction may be approximately the same in the horizontal direction (or horizontal plane), and each beam direction may be different in the vertical direction (or vertical plane).

[0454] Also, for example, as shown in (b) of FIG. 24, in multiple beams (for example, beam directions B1, B2, and B3), the beam directions may be different in both the horizontal direction (or horizontal plane) and the vertical direction (or vertical plane).

[0455] <Multi-beam setting example 3> In setting example 3, for example, as shown in Fig. 25, in multiple beams (e.g., beam directions B1 and B2), the beam directions may be almost the same, but the beam widths may be different. Also, in multiple beams (e.g., beam directions B1 and B2), the beam directions in the horizontal direction (or horizontal plane) may be almost the same, but the beam widths in the horizontal direction (or horizontal plane) may be different. Also, in multiple beams (e.g., beam directions B1 and B2), the beam directions in the vertical direction (or vertical plane) may be almost the same, but the beam widths in the vertical direction (or vertical plane) may be different.

[0456] In setting example 3, for example, by replacing the "transmitting antennas with different beam directions" described in the above embodiment with "transmitting antennas with different beam widths" (hereinafter referred to as "different beams"), the same application as the above embodiment is possible.

[0457] Hereinafter, an example of the operation of the radar device 10 in the case where the beam direction is the same but the beam width is different will be described using coded Doppler phase rotation amount setting example 1 as an example. Note that the setting of the coded Doppler phase rotation amount is not limited to setting example 1, and the radar device 10 can operate in the same manner even when other coded Doppler phase rotation amount setting examples are used, and the same effects as those of the above embodiment can be obtained.

[0458] For example, the number of transmitting antennas Nt=4 (for example, Tx#1, Tx#2, Tx#3, Tx#4), N B1 =2, N B2= 2, the above-mentioned setting example 1 of the coded Doppler phase rotation amount in the phase rotation amount setting unit 105 is applied. For example, Tx#1 and Tx#2 are transmitting antennas with a beam width B1 (for example, beam B1) shown in FIG. 25, and Tx#3 and Tx#4 are transmitting antennas with a beam width B2 (for example, beam B2) shown in FIG. 25. FIG. 25 shows an example in which the beam width of beam B1 is wider than the beam width of beam B2. Here, the beam widths of beams B1 and B2 may be in the horizontal direction (or horizontal plane), or in the vertical direction (or vertical plane), or in both the horizontal direction (or horizontal plane) and the vertical direction (or vertical plane), and the same effect can be obtained.

[0459] Furthermore, in the radar device 10, the receiving antenna may be an omnidirectional antenna (or an antenna with approximately uniform directional characteristics within the viewing angle covered by the transmitting antennas of both beams B1 and B2).

[0460] For example, when the target position is target position (1) or target position (3) shown in FIG. 25, the target position is within the beam width and viewing angle of beam B1, so the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 of beam B1 is relatively high. On the other hand, target position (1) and target position (3) are outside the beam width and viewing angle of beam B2, so the radiation direction of the radar transmission wave transmitted from Tx#3 and Tx#4 of beam B2 does not match the direction of target positions (1) and (3), and target position (1) and target position (3) correspond to the null direction of the transmitting antenna Tx#3 of beam B2. Therefore, the reception level of the reception signal corresponding to Tx#3 and Tx#4 in the radar device 10 is lower than the reception level of the reception signal corresponding to Tx#1 and Tx#2. For example, the reception levels of the reception signals corresponding to Tx#3 and Tx#4 are significantly different from the reception levels of the reception signals corresponding to Tx#1 and Tx#2, and may be, for example, 10 dB or more lower depending on the beam directivity characteristics in the null direction of Tx#3 and Tx#4. In such a case, the reception signal received by the radar device 10 becomes the reception signal shown in (a) of FIG.

[0461] Also, for example, when the target position is in an area where the viewing angles of both beams B1 and B2 overlap (for example, when it is in a close distance) like target position (4) shown in Fig. 25, the radar device 10 receives reflected waves corresponding to the radar transmission waves transmitted from Tx#1 and Tx#2 of beam B1, and reflected waves corresponding to the radar transmission waves transmitted from Tx#3 and Tx#4 of beam B2. In this case, the received signal received by the radar device 10 may be, for example, a received signal as shown in (b) of Fig. 9. Alternatively, for example, when the directional gain of beam B2 is higher than that of beam B1 by about 10 dB or more, the received signal received by the radar device 10 may be, for example, a received signal as shown in (c) of Fig. 9.

[0462] Also, for example, when the target position is within the viewing angle of beam B2 and outside the viewing angle of beam B1 (for example, at a long distance) like target position (2) shown in FIG. 25, the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 of beam B2 is relatively high. On the other hand, since the directional gain of beam B1 is smaller than that of beam B2, the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 of beam B1 is lower than the reception level of the reception signal corresponding to Tx#3 and Tx#4. For example, the reception level of the reception signal corresponding to Tx#1 and Tx#2 is significantly different from the reception level of the reception signal corresponding to Tx#3 and Tx#4, and depending on the beam directivity characteristics of Tx#1 and Tx#2, it may be, for example, 10 dB or more lower. In such a case, the reception signal received by the radar device 10 becomes the reception signal shown in FIG. 9(c).

[0463] 9(b), when the radar device 10 receives signals corresponding to the transmitting antennas of each beam at approximately the same reception level, the signals transmitted from Nt transmitting antennas including the transmitting antennas of beams B1 and B2 are coded Doppler multiplexed with the coded Doppler multiplexing numbers for the Doppler multiplexed signals set unevenly. Thus, the radar device 10 can separate the coded Doppler multiplexed signal based on the existing operation of separating the coded Doppler multiplexed signal.

[0464] 9(a) and 9(c), when the radar device 10 receives a reflected wave from either beam B1 or beam B2 (when the reception levels differ greatly), it receives a different coded Doppler multiplexed signal (for example, a Doppler multiplexed signal that satisfies condition 1) depending on the target position. Therefore, the radar device 10 can determine in the coded Doppler multiplex separation unit 212 whether a decrease in the reception level of the reception signal corresponding to the transmitting antenna of beam B1 has occurred or a decrease in the reception level of the reception signal corresponding to the transmitting antenna of beam B2 has occurred.

[0465] For example, the coded Doppler multiplexed signal transmitted from the transmitting antenna of beam B1 (or beam B2) is coded Doppler multiplexed with the coded Doppler multiplexing numbers for the Doppler multiplexed signal set to non-uniform values. Therefore, for example, when the coded Doppler multiplexing separation unit 212 determines that the received signal corresponds to the transmitting antenna of beam B1 (or beam B2), the radar device 10 can separate the coded Doppler multiplexed signal by using an existing coding Doppler multiplexed signal separation operation.

[0466] By operating the coded Doppler multiplex 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 coded Doppler multiplex signal.

[0467] The embodiments of the present disclosure have been described above.

[0468] [Other embodiments] (1) In a radar device according to an embodiment of the present disclosure, a radar transmitter and a radar receiver may be disposed separately in physically separate locations. Also, in a radar receiver according to an embodiment of the present disclosure, a direction estimator and other components may be disposed separately in physically separate locations.

[0469] (2) The number of transmitting antennas Nt, the number of receiving antennas Na, and the number of Doppler multiplexing N DM , the number of beams in the multi-beam system NB, and the number of transmitting antennas in each beam direction N Bq , Doppler shift amount, Doppler shift interval, number of code multiplexes N CM The 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.

[0470] (3) The arrangement examples of the MIMO antennas used in the embodiment of the present disclosure (e.g., arrangement example A and arrangement example B) have been described as cases in which radar transmission signals are transmitted from multiple transmission antennas using coded Doppler multiplexing, but are not limited thereto. For example, the present disclosure can also be applied to cases in which radar transmission signals are transmitted from multiple transmission antennas using time division multiplexing or code multiplexing, and the effects of the disclosed MIMO antenna arrangement can be obtained.

[0471] (4) In the above embodiment, in a multi-beam transmission MIMO radar using coded Doppler multiplexing, in order to expand the detectable Doppler frequency range to ±1 / (2Tr) range for transmitting antennas including Nt different directivities, the code multiplexing numbers between Doppler multiplexed signals are set unevenly, and coded Doppler multiplexing is performed from multiple transmitting antennas. In the above embodiment, a method for improving the detection performance of a multi-beam transmission MIMO radar by applying coded Doppler multiplexing 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 preconditions do not need to be applied.

[0472] For example, the encoding unit 107 may set the number of coded Doppler multiplexes N to N by using a uniform Doppler shift amount setting with a narrower interval than the maximum uniform Doppler shift amount setting. DOP_CODE (1), N DOP_CODE (2), ~, N DOP_CODE (N DM ) for 1 to N CM For example, the encoding unit 107 may set the code number N CM Therefore, the Doppler shift amount DOP ndm In multiple combinations of and orthogonal code sequences, the Doppler shift amount DOP ndm The number of multiplexes (coded Doppler multiplexes) corresponding to each orthogonal code sequence is N. DOP_CODE (ndm) may be the same. For example, the encoding unit 107 may uniformly set the number of coded Doppler multiplexing for the Doppler multiplexed signals. With this setting, the Doppler multiplexed signals become unevenly spaced Doppler multiplexed, so that the radar device 10 can individually separate and receive the signals that have been coded Doppler multiplexed from the multiple transmitting antennas over a Doppler range of ±1 / (2×Loc×Tr). By applying such a coded Doppler multiplexing setting and further applying coded Doppler multiplexing that satisfies condition 1, it is possible to improve the detection performance of the multi-beam transmitting MIMO radar.

[0473] 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 DOP_CODE (1), N DOP_CODE (2),~,N DOP_CODE (N DM ) for 1 to N CM For example, the encoding unit 107 may set the code number N CM In this case, the Doppler shift amount 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 uniformly set the number of encoded Doppler multiplexing signals for the Doppler multiplexing signals. 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 that have been coded Doppler multiplexed from multiple transmitting antennas can be individually separated and received. By applying such coded Doppler multiplexing settings and further applying coded Doppler multiplexing that satisfies condition 1, it is possible to improve the detection performance of the multi-beam transmitting MIMO radar.

[0474] (5) 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.

[0475] Furthermore, when code multiplexing is applied using some but not all of the Nt transmitting antennas provided in 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 in a time-division manner and transmit. 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-mentioned embodiment can be obtained in an equivalent manner.

[0476] Furthermore, when code multiplexing transmission is applied 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.

[0477] (6) 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.

[0478] 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.

[0479] In addition, the notation "... part" in the above-mentioned embodiments may be replaced with other notations such as "... circuitry", "... assembly", "... device", "... unit", or "... module".

[0480] 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.

[0481] 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.

[0482] 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.

[0483] 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.

[0484] <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 forms a first beam and a second transmitting antenna that forms a second beam different from the first beam, and a transmitting circuit that multiplexes 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 a 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.

[0485] In one embodiment of the present disclosure, the number of the plurality of transmitting antennas is less than the total number of the combinations.

[0486] In one embodiment of the present disclosure, the first pattern and the second pattern have, with respect to the intervals of the Doppler shift amounts, a Doppler multiplexing number by the first transmitting antenna and a Doppler multiplexing number by the second transmitting antenna that are the same, and at least one of the intervals of the Doppler shift amounts by the first transmitting antenna is different from the intervals of the Doppler shift amounts by the second transmitting antenna.

[0487] In an embodiment of the present disclosure, the first pattern and the second pattern relate to a Doppler multiplexing number, and the Doppler multiplexing number by the first transmitting antenna and the Doppler multiplexing number by the second transmitting antenna are different.

[0488] 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 by the first transmitting antenna are the same as a plurality of second Doppler shift intervals by 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.

[0489] In one embodiment of the present disclosure, the first pattern and the second pattern are such that, for the code sequences, in the multiple combinations, an index of the code sequence corresponding to each of the Doppler shift amounts associated with the first transmitting antenna is different from an index of the code sequence corresponding to each of the Doppler shift amounts associated with the second transmitting antenna.

[0490] 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 number of code multiplexes by the code sequence corresponding to each of the Doppler shift amounts associated with the first transmitting antenna is different from the number of code multiplexes by the code sequence corresponding to each of the Doppler shift amounts associated with the second transmitting antenna.

[0491] 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.

[0492] In one embodiment of the present disclosure, the system further includes a plurality of receiving antennas for receiving reflected wave signals of the transmitted signals reflected by a target, and a receiving circuit for estimating a direction of the target using the reflected wave signals.

[0493] In one embodiment of the present disclosure, the radio system further includes a plurality of receiving antennas arranged at a first interval in a first direction, the first transmitting antennas being arranged at the first interval in the first direction and arranged at a different position in a second direction perpendicular to the first direction, the second transmitting antennas being arranged at the first interval in the first direction and arranged at a different position in the second direction perpendicular to the first direction, and the first transmitting antennas and the second transmitting antennas being arranged at an interval greater than an aperture length of the plurality of receiving antennas in the first direction.

[0494] In one embodiment of the present disclosure, the antenna further includes a plurality of receiving antennas arranged at a first interval in a first direction, the first transmitting antennas being arranged at the second interval in the first direction and arranged at a different position in a second direction perpendicular to the first direction, the second transmitting antennas being arranged at the second interval in the first direction and arranged at a different position in the second direction perpendicular to the first direction, the first transmitting antennas and the second transmitting antennas being arranged at an interval greater than an aperture length of the plurality of receiving antennas in the first direction, and a difference between the first interval and the second interval being a specified value based on the wavelength of the transmitting signal.

[0495] In one embodiment of the present disclosure, the specified value is any value in the range of 0.45 to 0.8 times the wavelength.

[0496] In one embodiment of the present disclosure, the first beam and the second beam differ in at least one of a beam direction and a beam width.

[0497] 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 a period corresponding to the code length of the code sequence, or every measurement period in the radar device. [Industrial Applicability]

[0498] The present disclosure is suitable for a radar device that detects a wide angle range. [Explanation of symbols]

[0499] 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 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 CFAR Department 212 Coded Doppler demultiplexer 213 Direction estimation part

Claims

1. A plurality of transmission antennas including a first transmission antenna that forms a first beam and a second transmission antenna that forms a second beam different from the first beam, 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, A radar device.

2. 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 amounts associated with the first transmission antenna is different from the interval of the Doppler shift amounts associated with the second transmission antenna, The radar device according to claim 1.

3. The first pattern and the second pattern relate to the 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.

4. 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.

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

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

7. In a plurality of the combinations, with respect to 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.

8. A plurality of receiving antennas that receive a reflected wave signal obtained by reflecting the transmission signal by a target; A receiving circuit that estimates the direction of the target using the reflected wave signal; The radar apparatus according to claim 1, further comprising: The radar apparatus according to claim 1.

9. The radar apparatus according to claim 1, further comprising a plurality of receiving antennas arranged at a first interval in a first direction, Each antenna included in the first transmission antenna is arranged at the first interval in the first direction and at different positions in a second direction orthogonal to the first direction. Each antenna included in the second transmission antenna is arranged at the first interval in the first direction and at different positions in a second direction orthogonal to the first direction. In the first direction, the first transmission antenna and the second transmission antenna are arranged at an interval larger than the aperture length of the plurality of receiving antennas. The radar apparatus according to claim 1.

10. The radar apparatus according to claim 1, further comprising a plurality of receiving antennas arranged at a first interval in a first direction, Each antenna included in the first transmission antenna is arranged at a second interval in the first direction and at different positions in a second direction orthogonal to the first direction. Each antenna included in the second transmitting antenna is arranged at the second interval in the first direction and at different positions in a second direction orthogonal to the first direction. In the first direction, the first transmitting antenna and the second transmitting antenna are arranged at an interval larger than the aperture length of the plurality of receiving antennas. The difference between the first interval and the second interval is a specified value based on the wavelength of the transmission signal. The radar device according to claim 1.

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

12. Among the plurality of transmitting antennas, the combination of the transmitting 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 device. The radar device according to claim 1.

13. Apply a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence to the radar signal, Multiplex-transmit the radar signal to which the phase rotation amount is applied from a plurality of transmitting antennas. A method for transmitting a radar signal, The plurality of transmitting antennas include a first transmitting antenna that forms a first beam and a second transmitting antenna that forms a second beam different from the first beam. For each of the plurality of transmitting 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 transmitting antenna and a second pattern of a Doppler shift amount and a code sequence assigned to the second transmitting antenna are different. A method for transmitting a radar signal.

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

15. 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.

16. The first pattern and the second pattern are 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 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 method for transmitting a radar signal according to claim 13.

17. Receive, from a plurality of receiving antennas, 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. Perform direction estimation of the target using the reflected wave signal. The method for receiving a radar signal.

18. An applying circuit that applies a phase rotation amount corresponding to a combination of a Doppler shift amount and a code sequence to a radar signal. A transmission circuit that multiplex-transmits the radar signal to which the phase rotation amount is applied from a plurality of transmission antennas. Comprising The plurality of transmission antennas include a first transmission antenna that forms a first beam and a second transmission antenna that forms a second beam different from the first beam. 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 is different from a second pattern of a Doppler shift amount and a code sequence assigned to the second transmission antenna. Radar signal processing apparatus.

19. The first pattern and the second pattern are with respect to the intervals of the Doppler shift amounts. 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 amounts associated with the first transmission antenna is different from the intervals of the Doppler shift amounts associated with the second transmission antenna. The radar signal processing apparatus according to claim 18. **Claim 20** A radar signal processing apparatus according to claim 18 receives, from a plurality of reception antennas, a reflected wave signal obtained by reflecting a radar signal transmitted from the radar signal processing apparatus from a target. Performs direction estimation of the target using the reflected wave signal. Radar signal processing apparatus.

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