Radar device and radar signal transmission method

Abstract

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

Description

Technical Field

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

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

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-211388

[0006] Patent Document 2: U.S. Patent Publication No. 2022 / 0066012

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

[0008] Patent Document 4: Japanese Patent Application Publication No. 2014-119344

[0009] Patent Document 5: Japanese Patent Application Publication No. 2020-204603

[0010] Patent Document 6: Japanese Patent Application Publication No. 2022-92247

[0011] Non-patent literature

[0012] 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

[0013] Non-patent document 2: M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823

[0014] Non-patent literature 3: Direction-of-arrival estimation using signal subspacemodeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1 Publication Year: 1992, Page (s): 64-79 Summary of the invention

[0015] However, a method for detecting a target (or object) using a radar device (eg, MIMO radar) has not been fully studied.

[0016] The non-limiting embodiments of the present disclosure are helpful to provide a radar device and a method for transmitting a radar signal that improve the detection accuracy of a target object.

[0017] 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, transmitting signals to which phase rotation amounts corresponding to combinations of Doppler frequency shift amounts and code sequences are assigned, wherein a different combination of at least one of the Doppler frequency shift amounts and the code sequences corresponds to each of the plurality of transmitting antennas, and a first pattern of the Doppler frequency shift amounts and the code sequences assigned to the first transmitting antenna is different from a second pattern of the Doppler frequency shift amounts and the code sequences assigned to the second transmitting antenna.

[0018] In addition, these broad or specific embodiments may be implemented by systems, devices, methods, integrated circuits, computer programs or recording media, or by any combination of systems, devices, methods, integrated circuits, computer programs and recording media.

[0019] According to an embodiment of the present disclosure, the detection accuracy of a target object of a radar device can be improved.

[0020] Further advantages and effects in one embodiment of the present disclosure will be clearly presented by the description and the drawings. The above advantages and / or effects are provided by several embodiments and the features described in the description and the drawings, but not necessarily all of them are provided in order to obtain one or more of the same features. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing an example of coded Doppler multiplexing (DDM: Doppler Division Multiplexing) transmission.

[0022] Figure 2 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing.

[0023] Figure 3 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0024] Figure 4 This is a diagram showing an example of coded Doppler multiplexing transmission of a multi-beam transmission MIMO radar.

[0025] Figure 5 This is a block diagram showing a configuration example of a radar device.

[0026] Figure 6 This is a diagram showing an example of a transmission signal when a chirp signal is used.

[0027] Figure 7 It is a diagram showing an example of setting the Doppler shift amount and the code sequence.

[0028] Figure 8 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0029] Fig. 9 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing.

[0030] Fig.10 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0031] Fig.11 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0032] Fig.12 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0033] Fig.13 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0034] Fig.14 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0035] Fig.15 This is a diagram showing an example of a received signal transmitted by coded Doppler multiplexing.

[0036] Fig.16 This is a flowchart showing an example of the operation of demultiplexing a coded Doppler multiplexed signal.

[0037] Fig.17 It is a diagram showing a configuration example of a transmitting antenna.

[0038] Fig.18 This is a diagram showing an example of a MIMO antenna arrangement and a virtual receiving antenna arrangement.

[0039] Fig.19 This is a diagram showing an example of a MIMO antenna arrangement and a virtual receiving antenna arrangement.

[0040] Fig. 20 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0041] Fig.21 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0042] Fig. 22 This is a diagram showing an example of coded Doppler multiplexing transmission.

[0043] Fig.23 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0044] Fig.24 This is a diagram showing an example of a multi-beam transmission MIMO radar.

[0045] Fig.25 This is a diagram showing an example of a multi-beam transmission MIMO radar. DETAILED DESCRIPTION

[0046] [About Multibeam Radar]

[0047] For example, there is a method of constructing a MIMO radar using transmitting antennas or receiving antennas with multiple directional characteristics (or simply called "directivity") with different main beam directions (hereinafter sometimes also recorded as "beam directions", "transmitting beam directions" or "receiving beam directions") (for example, refer to Patent Document 1 or Patent Document 2).

[0048] Examples of different directional characteristics of a transmitting antenna or a receiving antenna include a directional characteristic with the same beam width but different beam directions, a directional characteristic with different beam directions and beam widths, and a directional characteristic with the same beam direction but different beam widths.

[0049] Hereinafter, a MIMO radar using a plurality of transmitting antennas having different directional characteristics as described above (for example, transmitting antennas forming different beams) is referred to as a "multi-beam transmitting MIMO radar". Here, the multi-beam transmitting MIMO radar includes a plurality of transmitting antennas having different directional characteristics. In addition, the multi-beam transmitting MIMO radar may also be a structure including one or more transmitting antennas having the same directivity.

[0050] In addition, hereinafter, a MIMO radar using a plurality of receiving antennas having different directional characteristics as described above (for example, receiving antennas forming different beams) is referred to as a "multi-beam receiving MIMO radar". Here, the multi-beam receiving MIMO radar includes a plurality of receiving antennas having different directional characteristics. In addition, the multi-beam receiving MIMO radar may also be a structure including one or more receiving antennas with the same directivity.

[0051] Similarly, hereinafter, a MIMO radar using 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, multi-beam MIMO radar).

[0052] For example, as multiplexing transmission methods of MIMO radar using multiple transmission antennas, time division multiplexing (TDM) transmission (for example, Patent Document 3) and Doppler division multiplexing (DDM) transmission (for example, Patent Document 4) are mentioned.

[0053] In the above-mentioned time division multiplexing transmission or Doppler multiplexing transmission, the reflected waves corresponding to the transmission signals from multiple transmission antennas can be demultiplexed using the allocated transmission time or Doppler frequency domain. On the other hand, in time division multiplexing transmission and Doppler multiplexing transmission, if the number of transmission antennas increases, the detection range of the Doppler frequency tends to become smaller. For example, in time division multiplexing and Doppler division multiplexing, the detectable Doppler frequency range is -1 / (2Nt×Tr)≦fd<1 / (2Nt×Tr), and the detection range of the Doppler frequency decreases inversely proportional to the number of transmission antennas. Here, Nt is the number of transmission antennas, and Tr is the transmission period of the transmission signal.

[0054] [About Coded Doppler Multiplexing Transmission]

[0055] Patent Document 5 (for example, Figure 1 ) discloses a multiplexing transmission method that combines Doppler multiplexing and code multiplexing (hereinafter referred to as "coded Doppler multiplexing transmission" or "Coded DDM").

[0056] For example, Figure 1 The figure shows an example of the allocation of transmission Doppler frequencies and codes when, when a radar transmission wave (e.g., a chirp signal) is transmitted at a transmission period Tr, the signal after code multiplexing with orthogonal codes (e.g., code#1, code#2) with a code length Loc=2 is transmitted using two Doppler multiplexed signals (e.g., Δfd1, Δfd2) for three transmitting antennas (e.g., Tx#1, Tx#2, Tx#3).

[0057] For example, the code length is times the transmission period Loc×Tr (in Figure 1 The chirp signal is repeatedly assigned in a cycle of 2 transmission periods (2Tr) to perform phase rotation based on the code. At this time, it is assumed that when a code with a code length of 2 is assigned, in a transmission period of code length times (in Figure 1 In the case where the phase rotation based on the Doppler multiplexed signal is constant during the two transmission cycles (2Tr), for example, the phase rotation based on the Doppler multiplexed signal may be varied every 2Tr transmission cycle and given.

[0058] For example, in Figure 1 In the example, the allocated transmit Doppler frequency shift amounts are set to Δfd1=-1 / (4Tr) and Δfd2=0 [Hz], respectively. For example, since the transmit Doppler frequency shift amount Δfd1 is assigned to each n-th transmit cycle, the radar transmit wave (chirp signal) is assigned a phase rotation Φ1(n)=ΔΦ1×(floor(n / Loc)+1). In addition, since the transmit Doppler frequency shift amount Δfd2 is assigned to each n-th transmit cycle, the radar transmit wave (chirp signal) is assigned a phase rotation Φ2(n)=ΔΦ2×(floor(n / Loc)+1). Here, ΔΦ1=-π, ΔΦ2=0. Doppler multiplexing interval Δf d =1 / (4Tr). In addition, for example, code#1=[1,1] and code#2=[1,-1] can be used as orthogonal codes of code length 2. Figure 1 For example, as a coded Doppler multiplexing signal combining a Doppler multiplexing signal and a code, DopCode#1=(Δfd1, code#1), DopCode#2=(Δfd1, code#2), and DopCode#3=(Δfd2, code#1) are assigned to the transmitting antennas Tx#1, Tx#2, and Tx#3, respectively, and transmitted. In addition, floor[x] is an operator that outputs the largest integer that does not exceed the real number x.

[0059] These signals multiplexed and transmitted simultaneously are received in a radar device (e.g., a received signal processing unit). For example, the radar device distinguishes the radar reflected wave received signals according to the transmission period of the code length, for example, for each odd-numbered transmission period received signal and each even-numbered transmission period received signal, respectively, and performs Doppler frequency analysis in separate Doppler analysis units (e.g., V-FFT#1 and V-FFT#2), and performs code multiplexing demultiplexing and Doppler multiplexing demultiplexing based on the output of the Doppler frequency analysis, thereby demultiplexing the multiplexed transmission signal and receiving it.

[0060] Here, the code length is used in the radar device (for example, the Doppler analysis unit) Figure 1The sending cycle of Loc=2) (in Figure 1 The received signal is 2 transmission cycles (2Tr) in the Figure 1 For example, as disclosed in Patent Document 5, a coded Doppler multiplexed signal (in Figure 1 In the example, the radar reflected wave reception signal is determined to include a component of the aliased frequency range by using the fact that the received power of a signal obtained by demultiplexing code multiplexing and demultiplexing Doppler multiplexing of the following signal is at the noise level, thereby determining whether the radar reflected wave reception signal includes a component of the aliased frequency range. The signal is a coded Doppler multiplexed signal that is a combination of an unused code to which a transmitting antenna is not allocated and a Doppler multiplexed signal.

[0061] In this way, the radar device multiplexes and transmits Doppler multiplexed signals from multiple transmitting antennas in a manner that makes the code multiplexing number between the Doppler multiplexed signals uneven, and detects the received signal level, thereby being able to detect whether there is an aliasing signal, thereby being able to expand the Doppler frequency range (maximum Doppler) in which the Doppler frequency can be detected without aliasing to ±1 / (2Tr), and being able to determine the transmitting antenna.

[0062] For example, Figure 2 (a) indicates that Figure 1 The coded Doppler multiplexed signal shown in FIG. 1 is the received Doppler signal when demultiplexed with code#1 and code#2 respectively when the Doppler frequency of the target object fdtarget=0. Figure 2 As shown in (a), in the received Doppler multiplexed signal demultiplexed with code#1, the reception levels at two Doppler frequencies are detected to be high, and the interval between the two Doppler frequencies is the same as the Doppler multiplexing interval Δf of Δfd1 and Δfd2. d The radar device can determine these components as the received signals of Tx#1 and Tx#3. Figure 2 As shown in (a), in the received Doppler signal demultiplexed with code#2, a Doppler frequency with a high reception level is detected, and the Doppler multiplexing interval Δfd1 and Δfd2 is Δfd2 with respect to the detected Doppler frequency. d The reception level of the Doppler frequencies at the same Doppler frequency interval is at the noise level. As a result, the radar device can determine the component of a Doppler frequency with a high reception level as the reception signal of Tx#2. In addition, since the deviation amount relative to the Doppler frequency shift amount when each transmitting antenna is transmitted is the Doppler frequency of the target object, the radar device can determine the Doppler frequency of the target object.

[0063] In addition, for example, Figure 2 (b) indicates that Figure 1 The coded Doppler multiplexed signal shown in FIG. 1 is a received Doppler signal when demultiplexed with code#1 and code#2 respectively when the Doppler frequency of the target object fdtarget=-1 / (2Tr). Figure 2 As shown in (b), in the received Doppler signal demultiplexed with code#2, the received levels at two Doppler frequencies are detected to be high, and the interval between the two Doppler frequencies is the same as the Doppler multiplexing interval Δf of Δfd1 and Δfd2. d The radar device can determine these components as the received signals of Tx#1 and Tx#3. Figure 2 As shown in (b), in the received Doppler signal demultiplexed with code#1, a Doppler frequency with a high reception level is detected, and the Doppler multiplexing interval Δfd1 and Δfd2 is Δfd2 with respect to the detected Doppler frequency. d The reception level of the Doppler frequencies at the same Doppler frequency interval is at the noise level. As a result, the radar device can determine the component of a Doppler frequency with a high reception level as the reception signal of Tx#2. In addition, since the deviation amount relative to the Doppler frequency shift amount when each transmitting antenna is transmitted is the Doppler frequency of the target object, the radar device can determine the Doppler frequency of the target object.

[0064] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), an aliased Doppler frequency will be observed in the Doppler analysis unit (for example, V-FFT#1 and V-FFT#2). At this time, the actual Doppler frequency has a phase difference of 2π during the transmission period of 2Tr relative to the Doppler frequency detected in the Doppler analysis unit (V-FFT#1 and V-FFT#2), so there is a phase rotation of π during the detection time difference Tr between V-FFT#1 and V-FFT#2. Therefore, in the case of Figure 2 As shown in (b), when the received signal of Tx#2 is determined in the demultiplexing of code#1, the radar device can determine that there is aliasing.

[0065] By demultiplexing and receiving the coded Doppler multiplexed signal in this way, the radar device can estimate the Doppler frequency of the radar reflected wave in the Doppler frequency range of ±1 / (2Tr). In this way, the detectable Doppler frequency range is expanded to ±1 / 2Tr by coded Doppler multiplexing transmission. For example, compared with Patent Document 3 or 4, the detectable Doppler frequency range is expanded to Nt times.

[0066] [Application of coded Doppler multiplexing transmission in multi-beam transmission MIMO radar]

[0067] As described above, a MIMO radar using coded Doppler multiplexing (e.g., also called "coded DDM") is different from a MIMO radar using Doppler multiplexing transmission (DDM) in that a portion of the Doppler frequency domain is not allocated to the transmission signal, and the MIMO radar performs demultiplexing processing of the Doppler multiplexed signal of the Doppler frequency of the estimated target based on the received power of the received Doppler frequency of the reflected wave from the target after demultiplexing of the code multiplexing (hereinafter referred to as "demultiplexing of coded Doppler multiplexing").

[0068] Therefore, in the case of applying coded Doppler multiplexing to a multi-beam transmission MIMO radar, the following situation can be conceived.

[0069] 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 the case where the beam direction coincides with the target direction and the case where the beam direction does not coincide with the target direction. Therefore, in a multi-beam transmission MIMO radar, when multiplexing transmission is performed using coded Doppler multiplexing, if the difference in the reception level of the reflected wave between the multi-beams in different beam directions is large, demultiplexing of Doppler multiplexing based on coded Doppler multiplexing becomes difficult. If demultiplexing of Doppler multiplexing becomes difficult, degradation of the detection performance of the target in the MIMO radar, or demultiplexing error of coded Doppler multiplexing, Doppler misestimation, or degradation of the angle measurement performance may occur.

[0070] Next, an example in which demultiplexing of Doppler multiplexing is difficult in a multi-beam transmission MIMO radar to which coded Doppler multiplexing is applied will be described.

[0071] For example, a 4Tx MIMO radar including two transmission antennas in each of two beam directions is described. For example, the number of transmission antennas corresponding to each of the two beam directions is represented as “N TxBeam#1 ” and “N TxBeam#2 ”(N TxBeam#1 =N TxBeam#2 =2).

[0072] For example, Figure 3 The multi-beam transmission MIMO radar shown in FIG. 1 is used to illustrate the formation of transmission beams (TxBeam#1, TxBeam#2) in two different directions, wherein each transmission beam is formed using two transmission antennas among the four transmission antennas Tx#1, Tx#2, Tx#3, and Tx#4. Figure 3, the transmission beam (beam direction) of Tx#1 and Tx#2 is set to TxBeam#1, and the transmission beam (beam direction) of Tx#3 and Tx#4 is set to TxBeam#2. In addition, for example, the directional characteristics of the receiving antenna can be non-directional, or it can be a directional characteristic that is roughly uniform within the field of view (FOV: field of view) covered by multiple transmitting antennas with different directivities.

[0073] For example Figure 4 As shown in (a), the four transmitting antennas Tx#1, Tx#2, Tx#3, and Tx#4 are assigned a Doppler multiplexing number N. DM =3, code multiplexing number N CM =2 coded Doppler multiplexed signal is described below.

[0074] For example, in the direction of the object Figure 3 In the case of the target object direction (1) shown, 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 object direction (1).

[0075] Therefore, if Figure 4 As shown in (b), the reception level (for example, the reflected wave reception level) of the received signal corresponding to Tx#1 and Tx#2 forming TxBeam#1 is high. Figure 3 In the case of the target object direction (1) shown in FIG. 1 , 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 object direction (1), and the target object direction (1) corresponds to the directivity zero direction (hereinafter also referred to as "zero direction") of TxBeam#2. Therefore, for example, Figure 4 As shown in (b), 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 greatly different from the reception level corresponding to TxBeam#1, and may be smaller by more than 10 dB depending on the beam pointing characteristics of the null azimuth of TxBeam#2.

[0076] In addition, for example, when the target object direction is the middle direction between the beam direction of TxBeam#1 and the beam direction of TxBeam#2, and the target object direction is in the direction of the region where the beam widths of the two beams overlap by about 3 dB or 6 dB (for example, in the case of Figure 3 In the case of the object direction (2) shown in the figure), Figure 4As shown in (c), the reflected wave corresponding to the radar transmission wave transmitted from Tx#1 and Tx#2 forming TxBeam#1 and the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 are received at the same level.

[0077] In addition, for example, in the direction of the object Figure 3 In the case of the target object direction (3) shown in FIG. 1 , the direction of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 is consistent with the target object direction (3). Figure 4 As shown in (d), the reception level (for example, the reflected wave reception level) of the received signal corresponding to Tx#3 and Tx#4 forming TxBeam#2 is high. Figure 3 In the case of the target direction (3) shown in FIG. 1 , 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) is equivalent to the zero direction of TxBeam#1. Figure 4 As shown in (d), the reception level of the reception signal corresponding to Tx#1 and Tx#2 forming TxBeam#1 is 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 is greatly different from the reception level corresponding to TxBeam#2, and may be smaller by more than 10 dB depending on the beam pointing characteristics of the null azimuth of TxBeam#1.

[0078] For example, in Figure 4 In the case of (c), the reception level of the reflected wave corresponding to the radar transmission wave sent from Tx#1 and Tx#2 forming TxBeam#1 is about the same as the reception level of the reflected wave corresponding to the radar transmission wave sent from Tx#3 and Tx#4 forming TxBeam#2. Since the code multiplexing number is not uniform between Doppler multiplexed signals, the multi-beam transmission MIMO radar can determine which transmission antenna used in coded Doppler multiplexing transmission the peak of the detected Doppler frequency corresponds to based on the reception levels of these received signals. In addition, Figure 4 In (c), the Doppler frequency fd of the target object reflected wave can be determined in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0079] On the other hand, Figure 4 (b) or Figure 4In the case of (d), since the Doppler frequency of the target object is unknown, it is difficult for the multi-beam transmission MIMO radar to determine based on the reception level of the received signal that 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, Figure 4 In the case of (d), the reception level of the reflected wave corresponding to the radar transmission wave transmitted from Tx#3 and Tx#4 forming TxBeam#2 is lowered (for example, Figure 4 (b)). Therefore, it is difficult for the multi-beam transmission MIMO radar to determine, based on the reception level of the received signal, which transmission antenna used in the coded Doppler multiplexing transmission corresponds to the peak of the detected Doppler frequency. Therefore, it is difficult for the multi-beam transmission MIMO radar to demultiplex the Doppler multiplexing signal and to determine the Doppler frequency fd of the reflected wave from the target (for example, called "target reflected wave") in the range of -1 / (2Tr)≦fd<1 / (2Tr).

[0080] Thus, in coded Doppler multiplexing, the demultiplexing process of coded Doppler multiplexing is performed on the premise that the reception levels of reflected waves corresponding to the respective transmission antennas are of the same level and the reception level of the Doppler multiplexing interval that is not Doppler multiplexed is sufficiently low to the level of noise level. In a multi-beam transmission MIMO radar using coded Doppler multiplexing, if Figure 4 As shown in (b) and (d), there is a case where the premise of the demultiplexing processing of the coded Doppler multiplexing does not hold (a case where the reception level corresponding to a part of the beams decreases), and the demultiplexing processing of the coded Doppler multiplexing may be performed erroneously.

[0081] In a non-limiting embodiment of the present disclosure, a method for improving the detection performance of a multi-beam transmission MIMO radar using coded Doppler multiplexing transmission is described.

[0082] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the embodiments, the same components are given the same reference numerals, and their descriptions are omitted to avoid duplication.

[0083] The following describes a structure (for example, a MIMO radar structure) in which, in a radar device, different multiplexed transmission signals are simultaneously sent out from a plurality of transmission antennas in a transmission branch, and each transmission signal is demultiplexed in a reception branch to perform reception processing.

[0084] In addition, as an example, the following describes a radar method that uses a frequency-modulated pulse wave such as a chirp pulse (for example, also referred to as "fast chirp modulation"). However, the modulation method is not limited to frequency modulation. For example, one embodiment of the present disclosure may also be applied to a radar method that uses a pulse compression radar that transmits a pulse train by phase modulation or amplitude modulation.

[0085] In addition, the radar device performs Doppler multiplexing transmission, for example. In addition, the radar device performs encoding (for example, CDM (Code Division Multiplexing)) of signals (hereinafter referred to as "Doppler multiplexing transmission signals") to which different phase rotations (for example, phase shifts) equal to the number of Doppler multiplexing are given in Doppler multiplexing transmission, and performs multiplexing transmission (hereinafter referred to as "Coded Doppler Multiplexing").

[0086] [Structure of radar device]

[0087] Figure 5 The radar device 10 includes a radar transmitting unit (transmitting branch) 100 and a radar receiving unit (receiving branch) 200 .

[0088] The radar transmitting unit 100 generates a radar signal (radar transmission signal) and uses a transmitting antenna unit 109 (e.g., a transmitting array antenna) composed of multiple transmitting antennas (e.g., Nt) to transmit the radar transmission signal at a predetermined transmission period (hereinafter referred to as "radar transmission period").

[0089] The radar receiving unit 200 uses a receiving antenna unit 202 (e.g., a receiving array antenna) including a plurality of receiving antennas 202-1 to 202-Na to receive a radar transmission signal, i.e., a reflected wave signal, which is reflected by a target (not shown). The radar receiving unit 200 performs signal processing on the reflected wave signal received by each receiving antenna, such as detecting the presence of a target or estimating the arrival distance, Doppler frequency (e.g., relative speed), and arrival direction of the reflected wave signal, and outputs information related to the estimation result (e.g., positioning information).

[0090] In addition, the radar device 10 can be mounted on a mobile object such as a vehicle, and the positioning output from the radar receiving unit 200 (for example, information related to the estimation result) can also be connected to a control device ECU (Electronic Control Unit) (not shown) such as an advanced driver assistance system (ADAS) or an automatic driving system that improves collision safety, for vehicle drive control or alarm call control.

[0091] In addition, the radar device 10 can be installed on a higher structure such as a roadside electric pole or a traffic light (not shown). In addition, the radar device 10 can also be used as a sensor in an auxiliary system for improving the safety of passing vehicles or pedestrians or a system to prevent suspicious people from breaking into the road (not shown). In addition, the positioning output of the radar receiving unit 200 can also be connected to a control device (not shown) in an auxiliary system for improving safety or a system to prevent suspicious people from breaking into the road, for example, for alarm call control or abnormality detection control. In addition, the use of the radar device 10 is not limited to this, and it can also be used for other purposes.

[0092] The target object is an object to be detected by the radar device 10 , and includes, for example, a vehicle (including four-wheeled and two-wheeled vehicles), a person, a rock, a curb, and the like.

[0093] [Configuration of Radar Transmitter 100]

[0094] 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 transmission antenna unit 109. The radar transmission signal generator 101, the phase rotation amount setting unit 105, and the phase rotation unit 108 may be collectively referred to as a "transmission circuit."

[0095] The radar transmission signal generating unit 101 generates a radar transmission signal. The radar transmission signal generating unit 101 includes, for example, a transmission signal generation control unit 102, a modulation signal generating unit 103, and a VCO (Voltage Controlled Oscillator) 104. The following describes each component of the radar transmission signal generating unit 101.

[0096] The transmission signal generation control unit 102 sets the transmission signal generation timing of each radar transmission cycle, for example, and outputs information related to the set transmission signal generation timing to the modulation signal generation unit 103 and the phase rotation amount setting unit 105 (for example, the Doppler shift setting unit 106). Here, the radar transmission cycle is set to Tr.

[0097] The modulated signal generation unit 103 periodically generates a modulated signal having, for example, a sawtooth shape, based on information on the transmission signal generation timing of each radar transmission cycle Tr input from the transmission signal generation control unit 102 .

[0098] The VCO 104 generates a frequency modulation signal (hereinafter, for example, referred to as a frequency chirp signal or a chirp signal) based on the modulation signal input from the modulation signal generator 103. Figure 6 The radar transmission signal (radar transmission wave) shown is output to the phase rotation unit 108 and the radar reception unit 200 (mixer unit 204 described later).

[0099] The phase rotation amount setting unit 105 sets the phase rotation amount (for example, the phase rotation amount corresponding to coded Doppler multiplexing transmission) given to the radar signal in each radar transmission cycle Tr in the phase rotation unit 108 based on the information related to the transmission signal generation timing of each radar transmission cycle Tr input from the transmission signal generation control unit 102. The phase rotation amount setting unit 105 includes, for example, a Doppler shift setting unit 106 and a coding unit 107.

[0100] The Doppler shift setting unit 106 sets a phase rotation amount corresponding to the Doppler shift amount given to the radar transmission signal (for example, chirp signal) based on information on the transmission signal generation timing of each radar transmission cycle Tr, for example.

[0101] The coding unit 107 sets the phase rotation amount corresponding to the code, for example, based on information related to the transmission signal generation timing of each radar transmission cycle Tr. The coding unit 107 calculates the phase rotation amount for the phase rotation unit 108, for example, based on the phase rotation amount input from the Doppler shift setting unit 106 and the phase rotation amount corresponding to the code, and outputs it to the phase rotation unit 108. In addition, the coding unit 107 outputs information related to the code sequence (for example, each element of the orthogonal code sequence) used in the coding to the radar receiving unit 200 (for example, the output switching unit 209).

[0102] The phase rotation unit 108 gives the chirp signal input from the VCO 104 a phase rotation amount input from the encoding unit 107, and outputs the phase-rotated signal to the transmission antenna unit 109. For example, the phase rotation unit 108 includes a phase shifter and a phase modulator (not shown). The output signal of the phase rotation unit 108 is amplified to a predetermined transmission power and radiated into space from each transmission antenna. For example, a radar transmission signal is given a phase rotation amount corresponding to a combination of a Doppler frequency shift amount and an orthogonal code sequence, and is multiplexed and transmitted from a plurality of transmission antennas.

[0103] Next, an example of a method of setting the phase rotation amount in the phase rotation amount setting unit 105 will be described.

[0104] The Doppler shift setting unit 106 sets the Doppler shift amount DOP to be given. ndm The phase rotation amount And output to the encoding unit 107. Here, ndm = 1 to N DM . N DM It is the setting number of different Doppler frequency shift amounts, hereinafter referred to as the "Doppler multiplexing number".

[0105] In the radar device 10, since the encoding by the encoding unit 107 is used in combination, the Doppler multiplexing number N may be DM It is set to be smaller than the number of transmission antennas Nt used in multiplex transmission. DM Is 2 or more.

[0106] As the Doppler frequency shift amounts DOP1, DOP2, ..., DOP N_DM (“N_DM” can also be expressed as “N DM ”) For example, the Doppler frequency shift amounts may be set at equal intervals, or the Doppler frequency shift amounts may be set at unequal intervals. In order to use the encoding of the encoding unit 107 described later, for example, the Doppler frequency shift amounts DOP1, DOP2, ..., DOP N_DM Set to satisfy 0≦DOP1, DOP2, ..., DOP N_DM <(1 / TrL oc ). Alternatively, the Doppler frequency shift amounts DOP1, DOP2, ..., DOP N_DM It is assumed to satisfy equation (1).

[0107] [Formula 1]

[0108]

[0109] In addition, for example, the Doppler shift amounts DOP1, DOP2, . . . , DOP N_DM The minimum Doppler frequency shift interval Δf MinInterval The following equation (2) is satisfied. In addition, the Doppler shift interval (also referred to as Doppler multiplexing interval or Doppler interval) can be obtained by the Doppler shift amounts DOP1, DOP2, ..., DOP N_DM Here, Loc represents the number of coding elements. For example, Loc represents the code length of the code used in the coding unit 107.

[0110] [Formula 2]

[0111]

[0112] In addition, for giving each Doppler shift amount DOP1, DOP2, ..., DOP N DM The phase rotation amount For example, it can be allocated as shown in the following formula (3).

[0113] [Formula 3]

[0114]

[0115] In addition, the intervals are set to be equal and Δf MinInterval In the case of a Doppler shift amount of equal intervals (hereinafter referred to as "equal interval Doppler shift amount setting"), for example, the Doppler shift amount DOP is allocated as shown in the following equation (4): ndm The phase rotation amount

[0116] [Formula 4]

[0117]

[0118] In addition, the minimum Doppler frequency shift interval Δf MinInterval The smaller the value, the easier it is for interference between Doppler multiplexed signals to occur, and the higher the possibility of a decrease (e.g., degradation) in target detection accuracy. Therefore, within the range of satisfying the constraints of equation (2), it is preferred to maximize the interval of Doppler frequency shift. For example, when the equal sign in equation (2) holds (e.g., Δf MinInterval =1 / (T r N DM L OC )), the intervals in the Doppler regions between the Doppler multiplexed signals can be maximized (hereinafter referred to as "maximum equally spaced Doppler frequency shift amount setting"). In this case, the phase rotation range greater than 0 and less than 2π is divided into N equal parts. DM Doppler frequency shift DOP1, DOP2, ..., DOP N_DM Different phase rotation amounts are allocated to each of them. For example, the amount of phase rotation for providing the Doppler shift amount DOP is allocated as shown in the following equation (5): ndm The phase rotation amount In addition, hereinafter, angles are expressed in radians.

[0119] [Formula 5]

[0120]

[0121] In equation (5), for example, when the Doppler multiplexing number N DM = 2, the phase rotation amount given to the Doppler frequency shift amount DOP1 Then, the phase rotation amount of the Doppler shift amount DOP2 is given For example, each Doppler shift amount DOP is assigned ndm The phase rotation amount is equal interval.

[0122] In addition, Doppler shift amounts DOP1, DOP2, ..., DOP N_DM The allocation of the phase rotation amount is not limited to this allocation method. For example, the allocation table of the phase rotation amount may be used to allocate the Doppler frequency shift amounts DOP1, DOP2, ..., DOP N_DM Randomly assign phase rotation (where “N_DM” is equivalent to N DM ).

[0123] Alternatively, in the setting of the Doppler frequency shift amount at equal intervals, by setting Δf in equation (4) MinInterval =1 / (T r (N DM +N int )L OC ), and thus the phase rotation amount is set as shown in the following equation (6). Here, N int Takes an integer value.

[0124] [Formula 6]

[0125]

[0126] The encoding unit 107 assigns N to the Doppler frequency shift setting unit 106. DM The phase rotation amount of the Doppler frequency shift Set based on 1 or N CM In addition, the encoding unit 107 sets a phase rotation amount based on both the Doppler frequency shift amount and the orthogonal code sequence (for example, a "coding Doppler phase rotation amount" for generating a coded Doppler multiplexed signal), and outputs it to the phase rotation unit 108.

[0127] An example of the operation in the encoding unit 107 is described below.

[0128] For example, preferably, the encoding unit 107 uses the number of codes (for example, the number of code multiplexing) N composed of the code length Loc. CM A plurality of code sequences with low correlation between each other or code sequences that are uncorrelated with each other, for example, an orthogonal code sequence is used. In addition, the code elements constituting the orthogonal code sequence are not limited to real numbers, and may also include complex values.

[0129] Next, N consisting of the code length Loc CM The orthogonal code sequence is expressed as Code ncm ={OCncm (1), OC ncm (2), ..., OC ncm (Loc)}. OC ncm (noc) represents the ncmth orthogonal code sequence Code ncm Here, noc is the index of the code element, noc = 1 to Loc.

[0130] The orthogonal code sequence used in the encoding unit 107 may be, for example, a Walsh-Hadamard code. The encoding unit 107 uses a Walsh-Hadamard code that can generate N codes. CM The specified code length L of the orthogonal code sequence OC To generate orthogonal code sequences.

[0131] For example, in N CM =2, the code length Loc of the Walsh-Hadamard code is 2, and the orthogonal code sequence is Code1={1,1}, Code2={1,-1}.

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

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

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

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

[0136] [Formula 7]

[0137]

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

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

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

[0141] [Formula 8]

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

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

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

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

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

[0147] Next, the code Doppler phase rotation amount ψ is described. ndop_code(ndm)，ndm (m) setting example.

[0148] For example, in the encoding unit 107, the number of transmission antennas used for multiplexing transmission is Nt=3, and the Doppler multiplexing number N DM =2, code multiplexing number N CM = 2, using the orthogonal code sequence Code1 = {1, 1}, Code2 = {1, -1} with a code length of Loc = 2. In this case, for example, Figure 7 As shown, when the coded Doppler multiplexing number N is set DOP_CODE (1) = 1, N DOP_CODE When (2)=2, the encoding unit 107 sets the encoding Doppler phase rotation amount ψ 1，1 (m), ψ 1，2 (m), ψ 2，2 (m), and outputs it to the phase rotation unit 108. For example, when setting the code Doppler phase rotation amount ψ 1，1 (m), the encoding unit 107 performs the following setting as in equation (9). Figure 7 In , “0” represents the used Doppler frequency shift and orthogonal code, and “×” represents the allocation of unused Doppler frequency shift and orthogonal code.

[0149] [Formula 9]

[0150]

[0151] Here, as an example, the Doppler shift amount DOP is given ndm The phase rotation amount of is set as (5) The encoding unit 107 uses the phase rotation amount given to the Doppler shift amount DOP1 and the phase rotation amount given to the Doppler frequency shift amount DOP2 Set the code Doppler phase rotation amount ψ 1，1 (m), ψ 1，2 (m), ψ 2，2 (m) and outputs it to the phase rotation unit 108. Alternatively, a modular operation modulo 2π may be performed to describe the phase rotation amount in a range of radians greater than or equal to 0 and less than 2π.

[0152] For example, regardless of the number of transmitting antennas Nt, the number of phases used for the phase rotation amount may be set to be smaller than the number of transmitting antennas Nt used for multiplexed transmission. In addition, the number of phases used for the phase rotation amount to give the Doppler frequency shift amount may be set to be smaller than the number of Doppler frequency shift amounts used for multiplexed transmission. DM equal.

[0153] In the above example, the setting of the phase rotation amount shown in the maximum equally spaced Doppler frequency shift amount setting is 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 equally spaced Doppler frequency shift amount setting may also be used, that is, for example, using formula (6).

[0154] The method of setting the phase rotation amount in the phase rotation amount setting unit 105 has been described above.

[0155] exist Figure 1 In the embodiment, the phase rotation unit 108 performs the phase rotation according to the code Doppler phase rotation amount ψ set in the phase rotation amount setting unit 105. ndop_code(ndm)，ndm (m) A phase rotation amount is given to the chirp signal input from the radar transmission signal generation unit 101 at the transmission period Tr. Here, ndm = 1 to N DM , ndop_code(NDM)=1~N DOP_CODE (NDM).

[0156] The outputs from the Nt phase rotation units 108 (for example, referred to as coded Doppler multiplexed signals) are amplified to predetermined transmission power and then radiated into space from the Nt transmission antennas of the transmission antenna unit 109 .

[0157] In addition, the code Doppler phase rotation amount ψ is given below. ndop_code(ndm)，ndm The phase rotation unit 108 of (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 , ndop_code(ndm)=1~N DOP_CODE (ndm). Alternatively, the Nt transmitting antennas are also expressed as Tx#1, Tx#2, ..., Tx#Nt. A known table or the like may be used in advance to establish a relationship with the coded Doppler phase rotation amount assigned to the radar transmission signal transmitted from the transmitting antennas Tx#1, Tx#2, ..., Tx#Nt. Thus, for example, it is possible to determine (or detect) the coded Doppler phase rotation amount ψ ndop_code(ndm)，ndm (m) to determine (or detect) the transmitting antenna.

[0158] For example, in Figure 7 In the example shown, the coding Doppler phase rotation amount ψ is input from the coding unit 107 to the phase rotation unit 108 at each transmission cycle. 1，1 (m), ψ 1，2 (m), ψ 2，2(m).

[0159] For example, the phase rotation unit PROT#[1,1] outputs the chirp signal cp(t) generated in the radar transmission signal generation unit 101 according to the transmission cycle, and the phase rotation amount ψ is given in the mth transmission cycle. 1，1 (m) signal exp[jψ 1，1 (m)]cp(t). In addition, the output of the phase rotation unit PROT#[1,1] is output from the transmitting antenna Tx#[1,1]. Here, cp(t) represents a chirp signal according to the transmission period. Similarly, the output of the phase rotation unit PROT#[1,2] is output from 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].

[0160] The above explains the code Doppler phase rotation amount ψ ndop_code(ndm),ndm (m) setting example.

[0161] In addition, in the present embodiment, the coded Doppler multiplexing number N for the Doppler multiplexed signal is set unevenly. DOP_CODE In the case of (ndm), it can be that the Doppler frequency shift amount DOP ndm Orthogonal code sequence Code ncm In the combination of ndm The corresponding orthogonal code sequence Code ncm The multiplexing number (for example, the coded Doppler multiplexing number N DOP_CODE (ndm)) is different.

[0162] In addition, in the present embodiment, the coded Doppler multiplexing number N for the Doppler multiplexed signal is uniformly set. DOP_CODE In the case of (ndm), it can be that the Doppler frequency shift amount DOP ndm Orthogonal code sequence Code ncm In the combination of ndm The corresponding orthogonal code sequence Code ncm The multiplexing number (for example, the coded Doppler multiplexing number N DOP_CODE (ndm)) is the same.

[0163] In this case, the Doppler shift amount DOP ndm The number of combinations of orthogonal code sequences and the number of transmitting antennas Nt may be the same number (for example, Nt may be set to DM ×N CM =Nt).

[0164] In addition, in this embodiment, the transmitting antennas Tx#1 to Tx#Nt may constitute a multi-beam transmitting radar including at least two transmitting antennas with different main beam directions (or beam directions). In addition, the transmitting antennas Tx#1 to Tx#Nt may include a plurality of transmitting antennas corresponding to different beam directions. In addition, the transmitting antennas Tx#1 to Tx#Nt may also include a plurality of transmitting antennas corresponding to the same beam direction.

[0165] For example, the phase rotation amount setting unit 105 may consider the structures of the transmitting antennas Tx#1 to Tx#Nt in different beam directions, and assign different coded Doppler phase rotation amounts ψ to the chirp signal according to the transmitting antennas that transmit the chirp signal. ndop_code(ndm),ndm Thus, even when the reception power levels of reflected waves are greatly different between the reception signals corresponding to the chirp signals transmitted from the transmission antennas in different beam directions, the radar device 10 can demultiplex the coded Doppler multiplexed signals, thereby improving the positioning performance and radar detection performance of the radar device 10.

[0166] Hereinafter, an operation example of the phase rotation amount setting unit 105 in the radar transmitting unit 100 when a multi-beam transmitting radar including at least a transmitting antenna forming two different beam directions is configured will be described.

[0167] In the following description, the first beam direction (or beam) of the plurality of beam directions (or beams) used in the multi-beam transmission MIMO radar is recorded as "B1", and the second beam direction (or beam) is recorded as "B2". In addition, for example, the number of multi-beams with different beam directions is recorded as "NB", and the qth beam direction (or beam) is recorded 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.

[0168] In addition, for example, it is assumed that the number of transmission antennas Nt≧3 and the number of Doppler multiplexing N DM ≧2, code multiplexing number N CM ≧2, where Nt <N DM ×N CM .

[0169] In the transmission antenna unit 109, the number of transmission antennas corresponding to the beam direction B1 is N. B1 , the number of transmitting antennas corresponding to the beam direction B2 is set to N B2 In this case, N B1 +N B2 =Nt. In addition, let the number of transmission antennas corresponding to the beam direction Bq be N Bq . N Bq≧1, the total number of transmitting antennas in each beam direction Bq is Nt.

[0170] In addition, the Doppler multiplexing number assigned to the transmission antenna in the beam direction B1 is expressed as N DM_B1 , the Doppler multiplexing number assigned to the transmitting antenna of beam direction B2 is expressed as N DM_B2 Here, N DM_B1 、N DM_B2 ≦N DM .

[0171] The phase rotation amount setting unit 105 sets the code Doppler multiplexing number N for the Doppler multiplexed signal unevenly, for example. DOP_CODE (ndm), and set the code Doppler phase rotation amount ψ in a manner that satisfies the following <Condition 1> ndop_code(ndm)，ndm (m). Here, ndm = 1 to N DM , ndop_code(ndm)=1~N DOP_CODE (ndm).

[0172] <Condition 1>

[0173] For example, the Doppler frequency shift amount and the code sequence pattern (e.g., coded Doppler multiplexing pattern) assigned to the transmitting antenna in the beam direction B1 are different from the coded Doppler multiplexing pattern assigned to the transmitting antenna in the beam direction B2. For example, the phase rotation amount setting unit 105 sets the coded Doppler phase rotation amount ψ that satisfies different Doppler multiplexing pattern conditions (e.g., Doppler frequency shift amount allocation pattern), different code multiplexing pattern conditions (e.g., different code multiplexing numbers between Doppler multiplexed signals), or different Doppler multiplexing and code multiplexing pattern conditions for the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2. ndop_code(ndm)，ndm (m).

[0174] For example, the different Doppler multiplexing mode condition may be one of the following conditions (eg, also referred to as "condition 1A").

[0175] (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 , but only for N DM_B1 =N DM_B2 ≧2), and each beam direction includes a different Doppler shift interval (for example, the interval of the Doppler shift amount corresponding to the transmitting antenna in each beam direction).

[0176] (A-2) The Doppler multiplexing number of each beam direction is different (N DM_B1 ≠N DM_B2 ).

[0177] (A-3) in N DM_B1 ≧3, N DM_B2 When ≧3, when the same Doppler shift interval is included in the Doppler shift intervals of each beam direction, the order of the Doppler shift intervals is different (not cyclically consistent).

[0178] In addition, for example, the different code multiplexing mode condition may be one of the following conditions (for example, also referred to as "condition 1B").

[0179] (B-1) The code intervals (for example, code index intervals) assigned to the respective Doppler multiplexed signals are different (not cyclically consistent).

[0180] (B-2) The code multiplexing numbers assigned to the respective Doppler multiplexed signals are different (circular inconsistency).

[0181] In addition, the phase rotation amount setting unit 105 may set the code Doppler phase rotation amount ψ that further satisfies the following condition 2, for example: ndop_code(ndm)，ndm (m).

[0182] <Condition 2>

[0183] The signals transmitted from the transmitting antennas in the same beam direction are multiplexed and transmitted with a non-uniform code multiplexing number between Doppler multiplexed signals. The code multiplexing number may be greater than 1 and N CM For example, with respect to the transmitting antenna of at least one of the beam direction B1 and the beam direction B2, among the multiple combinations of Doppler frequency shift amounts and code sequences, at least one Doppler frequency shift amount is such a Doppler frequency shift amount that the code multiplexing number based on the code sequence corresponding to the Doppler frequency shift amount is different from the code multiplexing number based on the code sequence corresponding to other Doppler frequency shift amounts.

[0184] For example, according to A-3 of condition 1, when the values ​​of the plurality of intervals of Doppler frequency shift amounts allocated between the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 are the same (for example, a combination of Doppler frequency shift intervals), the order of the plurality of Doppler frequency shift intervals corresponding to the transmitting antenna in beam direction B1 on the Doppler frequency axis and the order of the plurality of Doppler frequency shift intervals corresponding to the transmitting antenna in beam direction B2 on the Doppler frequency axis may be different. For example, the combination of the intervals included in the sequence in which the intervals of Doppler frequency shift amounts allocated to the transmitting antenna in beam direction B1 are arranged in order from the smallest on the Doppler frequency axis is the same as the combination of the intervals included in the sequence in which the intervals of Doppler frequency shift amounts allocated to the transmitting antenna in beam direction B2 are arranged in order from the smallest on the Doppler frequency axis, and the first sequence and the second sequence are different sequences when arranged in a circle. In the case of A-3 satisfying condition 1, even if one of the Doppler shift intervals of the transmitting antenna in beam direction B1 and the Doppler shift intervals of the transmitting antenna in beam direction B2 is cyclically shifted in the Doppler frequency domain, the two will not match (circular inconsistency).

[0185] In addition, for example, according to B-1 of condition 1, the order of the code sequences corresponding to the transmitting antennas in beam direction B1 on the Doppler frequency axis may be different from the order of the code sequences corresponding to the transmitting antennas in beam direction B2 on the Doppler frequency axis. For example, a sequence in which the indices of the code sequences corresponding to the Doppler frequency shift amounts assigned to the transmitting antennas in beam direction B1 are arranged in order from the smaller side on the Doppler frequency axis and a sequence in which the indices of the code sequences corresponding to the Doppler frequency shift amounts assigned to the transmitting antennas in beam direction B2 are arranged in order from the smaller side on the Doppler frequency axis are different sequences when arranged in a circle. In the case of satisfying B-1 of condition 1, even if one of the indices of the code sequences corresponding to the Doppler frequency shift amounts of the transmitting antennas in beam direction B1 and the indices of the code sequences corresponding to the Doppler frequency shift amounts of the transmitting antennas in beam direction B2 is cyclically shifted in the Doppler frequency domain, the two will not be consistent (cyclic inconsistency).

[0186] In addition, for example, according to B-2 of condition 1, the order of the code multiplexing numbers based on the code sequence corresponding to the transmitting antenna of beam direction B1 and the order of the code multiplexing numbers based on the code sequence corresponding to the transmitting antenna of beam direction B2 on the Doppler frequency axis may be different. For example, a sequence in which the code multiplexing numbers corresponding to the Doppler frequency shift amounts assigned to the transmitting antenna of beam direction B1 are arranged in order from the smaller side on the Doppler frequency axis and a sequence in which the code multiplexing numbers corresponding to the Doppler frequency shift amounts assigned to the transmitting antenna of beam direction B2 are arranged in order from the smaller side on the Doppler frequency axis are different sequences when arranged in a circle. In the case of satisfying B-2 of condition 1, even if one of the code multiplexing numbers corresponding to the Doppler frequency shift amounts of the transmitting antenna of beam direction B1 and the code multiplexing numbers corresponding to the Doppler frequency shift amounts of the transmitting antenna of beam direction B2 is cyclically shifted in the Doppler frequency domain, the two will not be consistent (cyclic inconsistency).

[0187] The setting of the coded Doppler phase rotation amount performed by the phase rotation amount setting unit 105 satisfies condition 1. Thus, even if the reception power levels of reflected waves differ greatly between the reception signals from the transmitting antennas in different beam directions, the radar device 10 can demultiplex the Doppler multiplexed signal in this case, thereby suppressing the degradation of the positioning performance and the radar detection performance (an example will be described later).

[0188] In addition, by making the setting of the coded Doppler phase rotation amount performed by the phase rotation amount setting unit 105 satisfy condition 2, the Doppler frequency range detectable by the radar device 10 reaches the range of -1 / (2Tr)≦fd<1 / (2Tr), which can be expanded to a range equivalent to the Doppler detection range when a single transmitting antenna is used (an example will be described later).

[0189] For example, in the coded Doppler multiplexing transmission of 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, as a case where condition 1 is satisfied but condition 2 is not satisfied, the following three cases are mentioned.

[0190] (Case 1)

[0191] Case 1 is a case where both beam direction B1 and beam direction B2 do not satisfy condition 2. In case 1, the detectable Doppler frequency range fd depends on the target direction and is within the range of -1 / (2Tr)≦fd<1 / (2Tr), -1 / (2Loc N DM_B1 Tr)≦fd<1 / (2Loc N DM_B1 Tr) or -1 / (2Loc N DM_B2 Tr)≦fd<1 / (2Loc NDM_B2 Here, when the Doppler multiplexed signal distributed between the transmitting antennas in the beam direction B1 does not contain unused codes, N DM_B1 =N B1 / Loc, the detectable Doppler frequency range fd is -1 / (2N B1 Tr)≦fd<1 / (2N B1 Similarly, when the Doppler multiplexed signal allocated between the transmitting antennas in the beam direction B2 does not contain unused codes, N DM_B2 =N B2 / Loc, the detectable Doppler frequency range fd is -1 / (2N B2 Tr)≦fd<1 / (2N B2 Tr) this range.

[0192] (Case 2)

[0193] Case 2 is a case where the beam direction B2 does not satisfy condition 2. In case 2, the detectable Doppler frequency range fd depends on the target direction and is within the range of -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2Loc N DM_B2 Tr)≦fd<1 / (2LocN DM_B2 For example, when the Doppler multiplexed signal allocated between the transmitting antennas in the beam direction B2 does not contain unused codes, N DM_B2 =N B2 / Loc, the detectable Doppler frequency range fd is -1 / (2N B2 Tr)≦fd<1 / (2N B2 Tr) this range.

[0194] (Case 3)

[0195] Case 3 is a case where the beam direction B1 does not satisfy condition 2. In case 3, the detectable Doppler frequency range fd depends on the target direction and is within the range of -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2Loc N DM_B1 Tr)≦fd<1 / (2LocN DM_B1 For example, when the Doppler multiplexed signal allocated between the transmitting antennas in the beam direction B1 does not contain any unused code, N DM_B1 =N B1 / Loc, the detectable Doppler frequency range fd is -1 / (2N B1 Tr)≦fd<1 / (2N B1 Tr) this range.

[0196] Regardless of which of the cases 1 to 3, the detectable Doppler frequency range can be expanded to -1 / (2N t Tr)≦fd<1 / (2N t Tr) Larger range.

[0197] The following describes an example of setting the coding Doppler phase rotation amount in the phase rotation amount setting unit 105. In addition, the interval of the Doppler frequency shift amounts assigned to Tx#n1 and Tx#n2 is expressed as the Doppler frequency shift interval "Δfd(n1, n2)". Here, Δfd(n1, n2) represents the Doppler frequency shift amount DOP assigned to Tx#n1. n1 The Doppler frequency shift DOP given to Tx#n2 based on the reference n2 The interval (DOP n2 -DOP n1 ). In addition, in the Doppler frequency shift interval Δfd ( n1, n2) is a negative value (for example, in (DOP n2 -DOP n1 )<0), taking into account the aliasing in the observation range of the Doppler analysis unit, that is, in the range of -1 / (2Loc Tr) or more and less than 1 / (2Loc Tr), Δfd(n1, n2 ) =1 / (Loc Tr)-Δfd(n1, n2) to calculate the Doppler frequency shift interval Δfd(n1, n2) and express it as a positive value.

[0198] <Setting Example 1>

[0199] Setting example 1 is a setting example of the code Doppler phase rotation amount when condition 1 (a case where the different code multiplexing mode condition is satisfied) and condition 2 are satisfied.

[0200] Figure 8 Indicates the number of transmitting antennas Nt = 4, N B1 =2, N B2 An example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 when φ=2.

[0201] exist Figure 8 In , Tx#1 and Tx#2 are the transmitting antennas of beam direction B1, and Tx#3 and Tx#4 are the transmitting antennas of beam direction B2. Figure 8 In the figure, the shaded circle marks indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx#1 and Tx#2) in beam direction B1, and the white circle marks indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx#3 and Tx#4) in beam direction B2.

[0202] In addition, Figure 8 In the Doppler multiplexing number N DM =3, the Doppler shift setting unit 106 can set three Doppler shift amounts DOP1, DOP2, and DOP3 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Figure 8 The phase rotation amount that gives the Doppler frequency shift amount DOP1 = 0 is Phase rotation amount given Doppler frequency shift amount DOP2 = Δfd Phase rotation amount that gives Doppler frequency shift amount DOP3 = -Δfd (You can also set ).like Figure 8 As shown, the interval between Doppler multiplexed signals (also called "Doppler multiplexing interval", "Doppler frequency shift interval", "Doppler interval") Δfd is equally spaced, and Δfd=1 / (6Tr).

[0203] In addition, Figure 8 In the code multiplexing number N CM =2, the coding unit 107 uses, for example, Walsh-Hadamard codes with orthogonal code sequences Code1={1,1} and Code2={1,-1} of code length Loc=2. In the following setting examples 2 to 5, the code multiplexing number N is CM =2, and the same code is also used.

[0204] exist Figure 8 In the example, the number of transmitting antennas Nt = 4, the number of Doppler multiplexing N DM =3, code multiplexing number N CM =2, Nt <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the Doppler multiplexed signal unevenly. DOP_CODE (ndm) (here, ndm = 1 to N DM ).

[0205] like Figure 8 As shown, in the encoding unit 107, the Doppler multiplexing numbers for encoding Doppler multiplexing signals using the three Doppler shift amounts DOP1, DOP2, and DOP3 input from the Doppler shift setting unit 106 are set to N and N, respectively. 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 code Doppler multiplexing number for the Doppler multiplexed signal to N in an uneven manner. DOP_CODE (1) = N DOP_CODE (2)≠N DOP_CODE (3).

[0206] In addition, Figure 8 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1 and Tx#2 in the beam direction B1. DM =3 Doppler multiplexing signal using Doppler frequency shift amounts DOP1 and DOP3 (N DM_B1 =2). In addition, the coding unit 107 allocates Code 2 and Code 1 to the Doppler multiplexed signal using the Doppler frequency shift amounts DOP1 and DOP3 allocated to the transmitting antennas Tx#1 and Tx#2 of the beam direction B1, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#1 and Tx#2 of the beam direction B1, respectively. 2，1 (m), ψ 1，3 (m).

[0207] In addition, Figure 8 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#3 and Tx#4 in the beam direction B2. DM =3 among the Doppler multiplexed signals using the Doppler frequency shift amounts DOP2 and DOP3 (N DM_B2 =2). In addition, the coding unit 107 allocates Code2 and Code2 to the Doppler multiplexed signal using the Doppler frequency shift amounts DOP2 and DOP3 allocated to the transmitting antennas Tx#3 and Tx#4 in the beam direction B2, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#3 and Tx#4 in the beam direction B2, respectively. 2，2 (m), ψ 2，3 (m).

[0208] exist Figure 8 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the transmitting antenna in the beam direction B1 and the transmitting antenna in 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 of the transmitting antennas Tx#1 and Tx#2 assigned to the beam direction B1 are Δfd(1,2)=2Δfd, Δfd(2,1)=Δfd, and the Doppler intervals of the Doppler multiplexed signals of the transmitting antennas Tx#3 and Tx#4 assigned to the beam direction B2 are Δfd(3,4)=Δfd, Δfd(4,3)=2Δfd, which are the same.

[0209] therefore, Figure 8 The setting of the code Doppler phase rotation amount shown does not satisfy any of the different Doppler multiplexing pattern conditions of condition 1A.

[0210] In addition, Figure 8 , for each Doppler multiplexed signal using Doppler frequency shift amounts DOP1, DOP2, and DOP3, the code allocated to the transmitting antenna in beam direction B1 is [Code2, no allocation, Code1], and the code multiplexing number allocated to each Doppler multiplexed signal is 0 or 1.

[0211] In addition, hereinafter, the code index assigned to the transmitting antenna of the beam direction B1 for each Doppler multiplexed signal using the Doppler frequency shift amounts DOP1, DOP2, and DOP3 is recorded as "CodeIndex_B1 = (2, *, 1)". In CodeIndex_B1, "*" indicates the case where no code is assigned. In addition, when multiple codes are assigned to a Doppler multiplexed signal, "&" is used to express it. For example, when Code1 and Code2 are assigned to a Doppler multiplexed signal, it is expressed as "1&2". The code index is also called a "code interval".

[0212] In addition, the code multiplexing number assigned to the transmission antenna of the beam direction B1 for each Doppler multiplexing signal using the Doppler shift amounts DOP1, DOP2, and DOP3 is described as "N_Code_B1 = (1, 0, 1)" ( Figure 8 situation).

[0213] exist Figure 8 , the codes assigned to the transmitting antennas of the beam direction B2 for each Doppler multiplexed signal using the Doppler frequency shift amounts DOP1, DOP2, and DOP3 are [no assignment, Code2, Code2], and the number of code multiplexing assigned to each Doppler multiplexed signal is 0 or 1. In addition, similarly to the case of beam direction B1, the code index assigned to the transmitting antennas of the beam direction B2 for each Doppler multiplexed signal using the Doppler frequency shift amounts DOP1, DOP2, and DOP3 is recorded as "CodeIndex_B2=(*, 2, 2)". In addition, the number of code multiplexing assigned to the transmitting antennas of the beam direction B2 for each Doppler multiplexed signal using the Doppler frequency shift amounts DOP1, DOP2, and DOP3 is recorded as "N_Code_B2=(0, 1, 1)".

[0214] In this way, for the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2, the code multiplexing numbers allocated to each Doppler multiplexed signal are N_Code_B1 = (1, 0, 1) and N_Code_B2 = (0, 1, 1), which are cyclically consistent and therefore do not satisfy B-2 of condition 1.

[0215] On the other hand, for the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2, the code indices assigned to each Doppler multiplexing signal are CodeIndex_B1 = (2, *, 1) and CodeIndex_B2 = (*, 2, 2), which are different (or can be expressed as "cyclically inconsistent". Hereinafter, it is also expressed as "the code index intervals are different").

[0216] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. At this time, the code indexes are CodeIndex_B1_alias=(1,*,2) and CodeIndex_B2_alias=(*,1,1), which are different (circular inconsistency). Therefore, in Figure 8 In the example, in the range of the target's Doppler frequency -1 / (2Tr) ≦ fdtarget < -1 / (2Tr), the code index is cyclically inconsistent and the code interval is different. Therefore, the code intervals allocated to each Doppler multiplexed signal between multiple beams are different, so B-1 that satisfies condition 1 meets the condition of different code multiplexing modes.

[0217] As mentioned above, Figure 8 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 1.

[0218] In addition, Figure 8 In the transmission antenna of beam direction B1, the code multiplexing number assigned to each Doppler multiplexing signal is N_Code_B1 = (1, 0, 1), and the code multiplexing number assigned to each Doppler multiplexing signal in the transmission antenna of beam direction B2 is N_Code_B2 = (0, 1, 1). Both are multiplexed and transmitted with uneven code multiplexing numbers between Doppler multiplexing signals, and the code multiplexing number is included in 1 or more and N CM In the range below -1.

[0219] Therefore, in Figure 8 In the example, signals transmitted from the transmitting antennas in the same beam direction (for example, beam directions B1 and B2) are multiplexed and transmitted with a non-uniform code multiplexing number between Doppler multiplexed signals, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Figure 8 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies Condition 2 in both the beam direction B1 and the beam direction B2.

[0220] The following describes the transmission antenna unit 109 including Figure 8An example of a received signal in the output of the Doppler analysis unit 210 is described in which the transmitting antennas have beam directions B1 and B2 for setting the encoded Doppler phase rotation amount shown, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam directions B1 and B2).

[0221] Fig. 9 The output of the Doppler analysis unit 210 for the target object reflected wave of a certain distance index is shown. For example, the target object reflected wave includes the Doppler frequency fd of the target object. target Therefore, the radar device 10 receives the Doppler frequency shift amount set in the radar transmitter 100 and generates fd target The amount of Doppler shift in the signal. Fig. 9 As an example, the Doppler frequency fd of the reflected wave of the target object is shown. target = 0 and fd target =1 / 2Tr case.

[0222] in addition, Fig.10 An example of a multi-beam transmission MIMO radar (for example, the radar device 10 ) that forms transmission beams in the beam direction B1 (Tx Beam # 1 ) and the beam direction B2 (Tx Beam # 2 ) is shown.

[0223] For example, in the direction of the object Fig.10 In the case of the target object direction (1) shown in FIG. 1 (for example, when the target object exists around the beam direction B1), the radiation direction of the radar transmission wave transmitted from Tx#1 and Tx#2 in the beam direction B1 coincides with the target object direction. Fig. 9 As shown in (a), the reception level of the received signal of the reflected wave from the target object corresponding to Tx#1 and Tx#2 in the radar device 10 is high. Fig.10 In the case of the target direction (1) shown in FIG. 1 , the radiation direction of the radar transmission wave transmitted from Tx#3 and Tx#4 in beam direction B2 is not consistent with the target direction, and the target direction is equivalent to the zero azimuth of the transmission beam B2. Fig. 9 As shown in (a), in the radar device 10, the reception level of the received signal of the reflected wave from the target corresponding to Tx#3 and Tx#4 is lower than the reception level of the received signal corresponding to each transmitting antenna (for example, Tx#1, Tx#2) in the beam direction B1. Fig. 9As shown in (a), the reception level of the received signal corresponding to Tx#3 and Tx#4 is greatly different from the reception level of the received signal corresponding to Tx#1 and Tx#2, and may be 10 dB or more lower depending on the beam pointing characteristics of the zero azimuth of Tx#3 and Tx#4. Fig. 9 In the figure, the size of the shaded circle mark or the white circle mark represents the received power. In this figure, if the size of the circle mark is small, it means that the received power is small compared with the case where the size is large (for example, the received power is as small as the noise level).

[0224] In addition, for example, when the target object direction is the middle direction between the beam direction B1 and the beam direction B2, and the target object direction is the direction of the region where the beam widths of the two beams overlap by about 3 dB or 6 dB (for example, Fig.10 The direction of the object shown in (2)), such as Fig. 9 As shown in (b), the reception level of the received signal (reflected wave of radar transmission wave) corresponding to Tx#1 and Tx#2 in beam direction B1 is about the same as the reception level of the received signal (reflected wave of radar transmission wave) corresponding to Tx#3 and Tx#4 in beam direction B2.

[0225] In addition, for example, in the direction of the object Fig.10 In the case of the target object direction (3) shown in FIG. 1 (for example, when the target object exists around the beam direction B2), the radiation direction of the radar transmission wave transmitted from Tx#3 and Tx#4 in the beam direction B2 coincides with the target object direction. Fig. 9 As shown in (c), the reception level of the received signal of the reflected wave from the target object corresponding to Tx#3 and Tx#4 in the radar device 10 is high. Fig.10 In the case of the target direction (3) shown in FIG. 1 , the radiation direction of the radar transmission wave transmitted from Tx#1 and Tx#2 in beam direction B1 is not consistent with the target direction, and the target direction is equivalent to the zero azimuth of the transmission beam B1. Fig. 9 As shown in (c), the reception level of the received signal of the reflected wave from the target corresponding to Tx#1 and Tx#2 in the radar device 10 is lower than the reception level of the received signal corresponding to each transmitting antenna (for example, Tx#3, Tx#4) in the beam direction B2. Fig. 9 As shown in (c), the reception level of the reception signal corresponding to Tx#1 and Tx#2 is greatly different from the reception level of the reception signal corresponding to Tx#3 and Tx#4, and may be more than 10dB lower depending on the beam pointing characteristics of the zero azimuth of Tx#1 and Tx#2.

[0226] For example, in Fig. 9As shown in (b), the target direction is the center direction between the beam direction B1 and the beam direction B2 ( Fig.10 In the case of the target direction (2) shown in the figure, the radar device 10 receives the reception signals corresponding to the transmission antennas in each beam direction at approximately the same reception level. Therefore, the signals transmitted from the Nt transmission antennas including the transmission antennas in the beam direction B1 and the beam direction B2 are coded Doppler multiplexed and transmitted using the setting of the existing coded Doppler multiplexed signal. Therefore, the radar device 10 can demultiplex the coded Doppler multiplexed signal based on the demultiplexing operation of the existing coded Doppler multiplexed signal. The demultiplexing operation of the existing coded Doppler multiplexed signal is disclosed in, for example, patent documents 5 and 6. This is also the same in the following embodiments.

[0227] In addition, in Fig. 9 As shown in (a), the target direction is the beam direction B1 ( Fig.10 In the case of the object direction (1) shown in FIG. Fig. 9 As shown in (c), the target direction is the beam direction B2 ( Fig.10 In the case of the target direction (3) shown in FIG. 1 ), the radar device 10 receives two different Doppler multiplexed signals with the same Doppler interval. Therefore, it is difficult for the radar device 10 to distinguish the Doppler multiplexed signals based on the Doppler frequency shift amount. On the other hand, Fig. 9 As shown in (a) and (c), the code multiplexing signals for the Doppler multiplexing signals are different (for example, the code intervals are different, satisfying B-1 of condition 1), therefore, Fig. 9 (a) When and Fig. 9 In (c), the radar device 10 receives coded Doppler multiplexed signals that are different from each other.

[0228] Therefore, when the direction of the target object is the beam direction B1 or B2, the radar device 10 can distinguish in the coded Doppler multiplexing and demultiplexing unit 212 described later whether the reception level of the reception signal corresponding to the transmitting antenna in the beam direction B1 is reduced, and whether the reception level of the reception signal corresponding to the transmitting antenna in the beam direction B2 is reduced.

[0229] Furthermore, when it is determined based on the determination result that the received signal is from the transmission antenna (Tx#1, Tx#2) in the beam direction B1, since the settings of the coded Doppler multiplexed signals for Tx#1 and Tx#2 in the beam direction B1 are known, the radar device 10 can demultiplex the multiplexed signal by, for example, the operation disclosed in Patent Documents 5 and 6. Furthermore, when it is determined that the received signal is from the transmission antenna (Tx#3, Tx#4) in the beam direction B2, since the settings of the coded Doppler multiplexed signals for Tx#3 and Tx#4 in the beam direction B2 are also known, the radar device 10 can demultiplex the multiplexed signal in the same manner.

[0230] In addition, by making the setting of the coding Doppler phase rotation amount performed by the phase rotation amount setting unit 105 satisfy condition 2 in addition to condition 1, the Doppler detection range can be expanded to the same range as that of the case with a single transmitting antenna (the range of ±1 / (2Tr)) (an example will be described later).

[0231] By operating the code Doppler multiplexing and demultiplexing unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antenna is associated with each code Doppler multiplexed signal.

[0232] <Setting Example 2>

[0233] Setting example 2 is a setting example of the code Doppler phase rotation amount when condition 1 (a case where the different code multiplexing mode condition is satisfied) and condition 2 are satisfied.

[0234] Fig.11 Indicates the number of transmitting antennas Nt = 6, N B1 =3,N B2 An example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 when φ=3.

[0235] exist Fig.11 In , Tx#1, Tx#2, and Tx#3 are the transmitting antennas of beam direction B1, and Tx#4, Tx#5, and Tx#6 are the transmitting antennas of beam direction B2. Fig.11 In the figure, the shaded circle marks indicate the allocation of coded Doppler multiplexed signals of the transmitting antennas (Tx#1, Tx#2, Tx#3) of the beam direction B1, and the white circle marks indicate the allocation of coded Doppler multiplexed signals of the transmitting antennas (Tx#4, Tx#5, Tx#6) of the beam direction B2.

[0236] In addition, Fig.11 In the Doppler multiplexing number N DM=4, the Doppler shift setting unit 106 can use the maximum equally spaced Doppler shift amount setting shown in equation (5) to set four Doppler shift amounts DOP1=0, DOP2=Δfd, DOP3=-2Δfd, and DOP4=-Δfd. Fig.11 The phase rotation amounts given to the Doppler frequency shift amounts DOP1 to DOP4 are like Fig.11 As shown, the Doppler multiplexing interval Δfd is an equal interval, Δfd=1 / (8Tr).

[0237] exist Fig.11 In the example, the number of transmitting antennas Nt = 6, the number of Doppler multiplexing N DM =4, code multiplexing number N CM =2, N t <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the Doppler multiplexed signal unevenly. DOP_CODE (ndm) (here, ndm = 1 to N DM ).

[0238] like Fig.11 As shown, in the encoding unit 107, the Doppler multiplexing numbers for encoding Doppler multiplexing signals using the four Doppler shift amounts DOP1, DOP2, DOP3, and DOP4 input from the Doppler shift setting unit 106 are set to N and N, respectively. 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 code Doppler multiplexing number for the Doppler multiplexed signal to N in an uneven manner. DOP_CODE (1)≠N DOP_CODE (2), or N DOP_CODE (3)≠N DOP_CODE (4).

[0239] In addition, Fig.11 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1, Tx#2, and Tx#3 in the beam direction B1. DM =4 Doppler multiplexed signals using Doppler frequency shift amounts DOP1, DOP3, and DOP4 (N DM_B1=3). In addition, the coding unit 107 allocates Code1, Code1, and Code2 to the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1, DOP3, and DOP4, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#1, Tx#2, and #3 in the beam direction B1, respectively. 1，1 (m), ψ 1，3 (m), ψ 2，4 (m).

[0240] In addition, Fig.11 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmitting antennas Tx#4, Tx#5, and Tx#6 in the beam direction B2. DM =4 Doppler multiplexing signal using Doppler frequency shift amounts DOP1, DOP2, and DOP3 (N DM_B2 =3). In addition, the coding unit 107 assigns Code2, Code2, and Code2 to the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1, DOP2, and DOP3, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#4, Tx#5, and #6 in the beam direction B2, respectively. 2，1 (m), ψ 2，2 (m), ψ 2，3 (m).

[0241] exist Fig.11 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2 is N. DM_B1 =N DM_B2 =3, which is the same. In addition, the Doppler intervals of the Doppler multiplexed signals of the transmitting antennas Tx#1, Tx#2, and #3 assigned to the beam direction B1 are Δfd(1,3)=2Δfd, Δfd(3,4)=Δfd, and Δfd(4,1)=Δfd, and the Doppler intervals of the Doppler multiplexed signals of the transmitting antennas Tx#4, Tx#5, and #6 assigned to the beam direction B2 are Δfd(1,2)=Δfd, Δfd(2,3)=Δfd, and Δfd(3,1)=2Δfd, which are the same (circularly consistent).

[0242] therefore, Fig.11 The setting of the code Doppler phase rotation amount shown does not satisfy any of the different Doppler multiplexing pattern conditions of condition 1A.

[0243] In addition, Fig.11In the figure, the code indices assigned to the transmitting antennas in beam direction B1 and B2 respectively for each Doppler multiplexing signal using Doppler multiplexing signals DOP1, DOP2, DOP3, and DOP4 are CodeIndex_B1=(1, *, 1, 2) and CodeIndex_B2=(2, 2, 2, *), which are cyclically inconsistent and have different code index intervals, and therefore satisfy B-1 of condition 1.

[0244] In addition, Fig.11 In the figure, for each Doppler multiplexing signal using Doppler multiplexing signals DOP1, DOP2, DOP3, and DOP4, the code multiplexing numbers allocated to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 are N_Code_B1 = (1, 0, 1, 1) and N_Code_B2 = (1, 1, 0, 1), respectively, including cyclically consistent code multiplexing numbers, and the code multiplexing numbers are the same, so B-2 of condition 1 is not satisfied.

[0245] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. At this time, the code indexes are CodeIndex_B1_alias=(2,*,2,1) and CodeIndex_B2_alias=(1,1,1,*), which are different (circular inconsistency). Therefore, in Fig.11 In the example, in the range of the target's Doppler frequency -1 / (2Tr) ≦ fdtarget < -1 / (2Tr), the code index is cyclically inconsistent and the code interval is different. Therefore, B-1 that satisfies condition 1 meets the condition of different code multiplexing modes.

[0246] As mentioned above, Fig.11 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 1.

[0247] In addition, Fig.11 In the transmission antenna of beam direction B1, the code multiplexing number assigned to each Doppler multiplexing signal is N_Code_B1 = (1, 0, 1, 1), and the code multiplexing number assigned to each Doppler multiplexing signal in the transmission antenna of beam direction B2 is N_Code_B2 = (1, 1, 0, 1). Both are multiplexed and transmitted with uneven code multiplexing numbers between Doppler multiplexing signals, and the code multiplexing number is included in 1 or more and N CM In the range below -1.

[0248] Therefore, in Fig.11In the example, signals transmitted from the transmitting antennas in the same beam direction (for example, beam directions B1 and B2) are multiplexed and transmitted with a non-uniform code multiplexing number between Doppler multiplexed signals, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig.11 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies Condition 2 in both the beam direction B1 and the beam direction B2.

[0249] The following describes the transmission antenna unit 109 including Fig.11 An example of a received signal in the output of the Doppler analysis unit 210 is described in which the Doppler frequency shift amount is set for transmitting antennas in different beam directions B1 and B2, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam direction B1 and beam direction B2).

[0250] For example, in the direction of the object Fig.10 In the case of the target direction (1) shown in FIG. 1 (for example, when the target exists in the periphery of the beam direction B1), or in the case of the target direction Fig.10 In the case of the target object direction (3) shown in the figure (for example, when the target object exists around the beam direction B2), the number of Doppler multiplexed signals, the code interval and the number of code multiplexing are different between the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2. Therefore, the radar device 10 can distinguish in the coded Doppler multiplexing and demultiplexing unit 212 described later whether the reception level of the received signal corresponding to the transmitting antenna in the beam direction B1 is reduced and whether the reception level of the received signal corresponding to the transmitting antenna in the beam direction B2 is reduced.

[0251] Furthermore, when it is determined based on the determination result that the received signal is from the transmission antenna (Tx#1, Tx#2, Tx#3) of the beam direction B1, since the settings of the coded Doppler multiplexed signals for Tx#1, Tx#2, and Tx#3 of the beam direction B1 are known, the radar device 10 can demultiplex the multiplexed signal by, for example, the operation disclosed in Patent Documents 5 and 6. Furthermore, when it is determined that the received signal is from the transmission antenna (Tx#4, Tx#5, and Tx#6) of the beam direction B2, since the settings of the coded Doppler multiplexed signals for Tx#4, Tx#5, and Tx#6 of the beam direction B2 are known, the radar device 10 can demultiplex the multiplexed signal in the same manner.

[0252] In addition, by making the setting of the coding Doppler phase rotation amount performed by the phase rotation amount setting unit 105 satisfy condition 2 in addition to condition 1, the Doppler detection range can be expanded to the same range as that of the case with a single transmitting antenna (the range of ±1 / (2Tr)) (an example will be described later).

[0253] By operating the code Doppler multiplexing and demultiplexing unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antenna is associated with each code Doppler multiplexed signal.

[0254] <Setting Example 3>

[0255] Setting example 3 is a setting example of the code Doppler phase rotation amount when condition 1 (a case where the different code multiplexing mode condition and the different Doppler multiplexing mode condition are satisfied) and condition 2 are satisfied.

[0256] Fig.12 Indicates the number of transmitting antennas Nt = 6, N B1 =3,N B2 An example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 when φ=3.

[0257] exist Fig.12 In the figure, Tx#1, Tx#2, and #3 are the transmitting antennas of beam direction B1, and Tx#4, Tx#5, and Tx#6 are the transmitting antennas of beam direction B2. Fig.12 In the figure, the shaded circle marks indicate the allocation of coded Doppler multiplexed signals of the transmitting antennas (Tx#1, Tx#2, #3) of the beam direction B1, and the white circle marks indicate the allocation of coded Doppler multiplexed signals of the transmitting antennas (Tx#4, Tx#5, Tx#6) of the beam direction B2.

[0258] In addition, Fig.12 In the Doppler multiplexing number N DM =4, the Doppler shift setting unit 106 can set four Doppler shift amounts DOP1 to DOP4 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig.12 The phase rotation amounts given to the Doppler frequency shift amounts DOP1 = 0, DOP2 = Δfd, DOP3 = -2Δfd, and DOP4 = -Δfd are respectively like Fig.12 As shown, the Doppler multiplexing interval Δfd is an equal interval, Δfd=1 / (8Tr).

[0259] exist Fig.12 In the example, the number of transmitting antennas Nt = 6, the number of Doppler multiplexing N DM=4, code multiplexing number N CM =2,N t <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the Doppler multiplexed signal unevenly. DOP_CODE (ndm) (here, ndm = 1 to N DM ).

[0260] like Fig.12 As shown, in the coding unit 107, the coding Doppler multiplexing numbers for the Doppler multiplexing signals using the four Doppler shift amounts DOP1 to DOP4 input from the Doppler shift setting unit 106 are set to N and N, respectively. 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 code Doppler multiplexing number for the Doppler multiplexed signal to N in an uneven manner. DOP_CODE (1)≠N DOP_CODE (2), or N DOP_CODE (3)≠N DOP_CODE (4).

[0261] In addition, Fig.12 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1, Tx#2, and Tx#3 in the beam direction B1. DM =4 Doppler multiplexing signal using Doppler frequency shift amounts DOP1 and DOP3 (N DM_B1 =2). In addition, the coding unit 107 allocates Code1, Code1, and Code2 (for example, using two codes) to the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1 and DOP3, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#1, Tx#2, and Tx#3 in the beam direction B1, respectively. 1，1 (m), ψ 1，3 (m), ψ 2，3 (m).

[0262] In addition, Fig.12 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmitting antennas Tx#4, Tx#5, and Tx#6 in the beam direction B2. DM =4 Doppler multiplexed signal using Doppler frequency shift amounts DOP1, DOP2, and DOP4 (N DM_B2=3). In addition, the coding unit 107 assigns Code2, Code2, and Code2 (for example, using one code) to the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1, DOP2, and DOP4, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#4, Tx#5, and Tx#6 in the beam direction B2, respectively. 2，1 (m), ψ 2，2 (m), ψ 2，4 (m).

[0263] exist Fig.12 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2 is N. DM_B1 =2, N DM_B2 =3, which is a different Doppler multiplexing number, and therefore satisfies A-2 of condition 1.

[0264] In addition, Fig.12 In the figure, the code indices assigned to each Doppler multiplexing signal using Doppler multiplexing signals DOP1~DOP4, the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 are CodeIndex_B1=(1,*,1&2,*) and CodeIndex_B2=(2,2,*,2), which are cyclically inconsistent and have different code index intervals, and therefore satisfy B-1 of condition 1.

[0265] In addition, Fig.12 In the figure, the code multiplexing numbers allocated to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 respectively for each Doppler multiplexing signal using Doppler multiplexing signals DOP1 to DOP4 are N_Code_B1 = (1, 0, 2, 0) and N_Code_B2 = (1, 1, 0, 1). The code multiplexing numbers are different, so B-2 of condition 1 is satisfied.

[0266] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. At this time, the code indexes are CodeIndex_B1_alias=(2,*,1&2,*) and CodeIndex_B2_alias=(1,1,*,1), which are different (circular inconsistency). Therefore, in Fig.12 In the example, in the range of the target's Doppler frequency -1 / (2Tr) ≦ fdtarget < -1 / (2Tr), the code index is cyclically inconsistent and the code interval is different. Therefore, B-1 that satisfies condition 1 meets the condition of different code multiplexing modes.

[0267] As mentioned above, Fig.12 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 1.

[0268] In addition, Fig.12 In the transmission antennas of beam direction B1 and beam direction B2, the code multiplexing numbers assigned to each Doppler multiplexed signal are N_Code_B1 = (1, 0, 2, 0) and N_Code_B2 = (1, 1, 0, 1), respectively. Fig.12 In the example, signals transmitted from the transmitting antennas in the same beam direction are multiplexed and transmitted with a non-uniform code multiplexing number between Doppler multiplexed signals, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig.12 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies Condition 2 in both the beam direction B1 and the beam direction B2.

[0269] The following describes the transmission antenna unit 109 including Fig.12 An example of a received signal in the output of the Doppler analysis unit 210 is described in which the Doppler frequency shift amount is set for transmitting antennas in different beam directions B1 and B2, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam direction B1 and beam direction B2).

[0270] For example, in the direction of the object Fig.10 In the case of the target direction (1) shown in FIG. 1 (for example, when the target exists in the periphery of the beam direction B1), or in the case of the target direction Fig.10 In the case of the target object direction (3) shown in the figure (for example, when the target object exists around the beam direction B2), the number of Doppler multiplexed signals, the code interval and the number of code multiplexing are different between the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2. Therefore, the radar device 10 can distinguish in the coded Doppler multiplexing and demultiplexing unit 212 described later whether the reception level of the received signal corresponding to the transmitting antenna in the beam direction B1 is reduced and whether the reception level of the received signal corresponding to the transmitting antenna in the beam direction B2 is reduced.

[0271] Furthermore, when it is determined based on the determination result that the received signal is from the transmission antenna (Tx#1, Tx#2, Tx#3) of the beam direction B1, since the settings of the coded Doppler multiplexed signals for Tx#1, Tx#2, and Tx#3 of the beam direction B1 are known, the radar device 10 can demultiplex the multiplexed signal by, for example, the operation disclosed in Patent Documents 5 and 6. Furthermore, when it is determined that the received signal is from the transmission antenna (Tx#4, Tx#5, and Tx#6) of the beam direction B2, since the settings of the coded Doppler multiplexed signals for Tx#4, Tx#5, and Tx#6 of the beam direction B2 are known, the radar device 10 can demultiplex the multiplexed signal in the same manner.

[0272] In addition, by making the setting of the coding Doppler phase rotation amount performed by the phase rotation amount setting unit 105 satisfy condition 2 in addition to condition 1, the Doppler detection range can be expanded to the same range as that of the case with a single transmitting antenna (the range of ±1 / (2Tr)) (an example will be described later).

[0273] By operating the code Doppler multiplexing and demultiplexing unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antenna is associated with each code Doppler multiplexed signal.

[0274] <Setting Example 4>

[0275] Setting example 4 is a setting example of the code Doppler phase rotation amount in a case where condition 1 (different code multiplexing mode condition) is satisfied but condition 2 is not satisfied.

[0276] Fig.13 Indicates the number of transmitting antennas Nt = 3, N B1 =2, N B2 An example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 when φ =1.

[0277] exist Fig.13 In , Tx#1 and Tx#2 are the transmitting antennas of beam direction B1, and Tx#3 is the transmitting antenna of beam direction B2. Fig.13 In the figure, the shaded circle marks indicate the allocation of the coded Doppler multiplexed signal to the transmitting antennas (Tx#1 and Tx#2) in the beam direction B1, and the white circle marks indicate the allocation of the coded Doppler multiplexed signal to the transmitting antenna (Tx#3) in the beam direction B2.

[0278] In addition, Fig.13 In the Doppler multiplexing number N DM=2, the Doppler shift setting unit 106 can set the two Doppler shift amounts DOP1 and DOP2 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig.13 The phase rotation amount that gives the Doppler frequency shift amount DOP1 = 0 is Phase rotation amount that gives Doppler frequency shift amount DOP2 = -Δfd like Fig.13 As shown, the Doppler multiplexing interval Δfd is an equal interval, Δfd=1 / (4Tr).

[0279] exist Fig.13 In the example, the number of transmitting antennas Nt = 3, the number of Doppler multiplexing N DM =2, code multiplexing number N CM =2, N t <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the Doppler multiplexed signal unevenly. DOP_CODE (ndm) (here, ndm = 1 to N DM ).

[0280] like Fig.13 As shown, in the coding unit 107, the coding Doppler multiplexing numbers for the Doppler multiplexing signals using the two Doppler shift amounts DOP1 and DOP2 input from the Doppler shift setting unit 106 are set to N and N, respectively. DOP_CODE (1) = 2, N DOP_CODE (2) = 1. In this way, the phase rotation amount setting unit 105 sets the code Doppler multiplexing number for the Doppler multiplexed signal to N in an uneven manner. DOP_CODE (1)≠N DOP_CODE (2).

[0281] In addition, Fig.13 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1 and Tx#2 in the beam direction B1. DM =2, the Doppler multiplexed signal using the Doppler frequency shift amounts DOP1 and DOP2 (N DM_B1 =2). In addition, the coding unit 107 allocates Code1 and Code1 to the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1 and DOP2 allocated 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 coding Doppler phase rotation amount ψ for the transmitting antennas Tx#1 and Tx#2 in the beam direction B1, respectively. 1，1 (m), ψ 1，2 (m).

[0282] In addition, Fig.13 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antenna Tx#3 in the beam direction B2. DM =2 among the Doppler multiplexed signals using the Doppler frequency shift amount DOP2 (N DM_B2 =1). In addition, the coding unit 107 allocates Code2 to the Doppler multiplexed signal using the Doppler frequency shift amount DOP2 allocated to the transmitting antenna Tx#3 in the beam direction B2. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antenna Tx#3 in the beam direction B2. 2，2 (m).

[0283] exist Fig.13 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2 is N. DM_B1 =2, N DM_B2 =1, which is a different Doppler multiplexing number, so A-2 of condition 1 is satisfied.

[0284] In addition, Fig.13 In the figure, the code indices assigned to each Doppler multiplexing signal using Doppler multiplexing signals DOP1 and DOP2, and to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 are CodeIndex_B1=(1, 1) and CodeIndex_B2=(*, 2), which are cyclically inconsistent and have different code index intervals, and therefore satisfy B-1 of condition 1.

[0285] In addition, Fig.13 In the figure, the code multiplexing numbers allocated to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 respectively for each Doppler multiplexing signal using Doppler multiplexing signals DOP1 and DOP2 are N_Code_B1=(1,1) and N_Code_B2=(0,1). The code multiplexing numbers are different, so B-2 of condition 1 is satisfied.

[0286] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), the aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. At this time, the code indexes are CodeIndex_B1_alias=(2,2) and CodeIndex_B2_alias=(*,1), which are different (circular inconsistency). Therefore, in Fig.13In the example, in the range of the target's Doppler frequency -1 / (2Tr) ≦ fdtarget < -1 / (2Tr), the code index is cyclically inconsistent and the code interval is different. Therefore, B-1 and B-2 that meet condition 1 meet the conditions of different code multiplexing modes.

[0287] As mentioned above, Fig.13 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 1.

[0288] In addition, Fig.13 In the transmitting antenna of the beam direction B1, the code multiplexing number allocated to each Doppler multiplexed signal is N_Code_B1=(1,1), and multiplexing and transmission are performed with a uniform code multiplexing number between Doppler multiplexed signals, so condition 2 is not satisfied.

[0289] On the other hand, Fig.13 In the transmitting antenna of beam direction B2, the code multiplexing number assigned to each Doppler multiplexing signal is N_Code_B2 = (0, 1), and the Doppler multiplexing signals are multiplexed and transmitted with uneven code multiplexing numbers, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig.12 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 2.

[0290] As mentioned above, Fig.13 The setting of the code Doppler phase rotation amount shown is a setting example in which the transmission antenna for the beam direction B1 does not satisfy the condition 2, but the transmission antenna for the beam direction B2 satisfies the condition 2.

[0291] The following describes the transmission antenna unit 109 including Fig.13 An example of a received signal in the output of the Doppler analysis unit 210 is described in which the Doppler frequency shift amount is set for transmitting antennas in different beam directions B1 and B2, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam direction B1 and beam direction B2).

[0292] For example, in the direction of the object Fig.10 In the case of the target direction (1) shown in FIG. 1 (for example, when the target exists in the periphery of the beam direction B1), or in the case of the target direction Fig.10In the case of the target object direction (3) shown in the figure (for example, when the target object exists around the beam direction B2), the code multiplexing number is different between the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2. Therefore, the radar device 10 can distinguish the case where the reception level of the received signal corresponding to the transmitting antenna in the beam direction B1 is reduced, and the case where the reception level of the received signal corresponding to the transmitting antenna in the beam direction B2 is reduced in the coded Doppler multiplexing and demultiplexing unit 212 described later.

[0293] Furthermore, when it is determined based on the determination result that the received signal is from the transmission antenna (Tx#1, Tx#2) in the beam direction B1, since the settings of the coded Doppler multiplexed signals for Tx#1 and Tx#2 in the beam direction B1 are known, the radar device 10 can demultiplex the multiplexed signal by, for example, the operation disclosed in Patent Documents 5 and 6. Furthermore, when it is determined that the received signal is from the transmission antenna (Tx#3) in the beam direction B2, since the settings of the coded Doppler multiplexed signal for Tx#3 in the beam direction B2 are known, the radar device 10 can demultiplex the multiplexed signal in the same manner.

[0294] In the setting example 4, the setting of the code 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 depends on the target object direction and is within the range of -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2Loc N DM_B1 Tr)≦fd<1 / (2Loc N DM_B1 Tr), the Doppler detection range can be expanded to a larger range than the Doppler detection range of the equally spaced DDM: -1 / (6Tr)≦fd<1 / (6Tr), depending on the target direction.

[0295] <Setting Example 5>

[0296] Setting example 5 is a setting example of the code Doppler phase rotation amount in a case where condition 1 (different Doppler multiplexing pattern condition and different code multiplexing pattern condition) is satisfied but condition 2 is not satisfied.

[0297] Fig.14 Indicates the number of transmitting antennas Nt = 4, N B1 =2, N B2 An example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 when φ=2.

[0298] exist Fig.14 In , Tx#1 and Tx#2 are the transmitting antennas of beam direction B1, and Tx#3 and Tx#4 are the transmitting antennas of beam direction B2. Fig.14In the figure, the shaded circle marks indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx#1 and Tx#2) in beam direction B1, and the white circle marks indicate the allocation of coded Doppler multiplexed signals to the transmitting antennas (Tx#3 and Tx#4) in beam direction B2.

[0299] In addition, Fig.14 In the Doppler multiplexing number N DM =3, the Doppler shift setting unit 106 can set three Doppler shift amounts DOP1, DOP2, and DOP3 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig.14 The phase rotation amounts given to the Doppler frequency shift amounts DOP1 = 0, DOP2 = Δfd, and DOP3 = -Δfd are respectively (You can also set ).like Fig.14 As shown, the Doppler multiplexing interval Δfd is an equal interval, Δfd=1 / (6Tr).

[0300] exist Fig.14 In the example, the number of transmitting antennas Nt = 4, the number of Doppler multiplexing N DM =3, code multiplexing number N CM =2,N t <N DM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the Doppler multiplexed signal unevenly. DOP_CODE (ndm) (here, ndm = 1 to N DM ).

[0301] like Fig.14 As shown, in the encoding unit 107, the Doppler multiplexing numbers for encoding Doppler multiplexing signals using the three Doppler shift amounts DOP1, DOP2, and DOP3 input from the Doppler shift setting unit 106 are set to N and N, respectively. 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 code Doppler multiplexing number for the Doppler multiplexed signal to N in an uneven manner. DOP_CODE (1) = N DOP_CODE (2)≠N DOP_CODE (3).

[0302] In addition, Fig.14 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1 and Tx#2 in the beam direction B1. DM =3 among the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1 and DOP2 (NDM_B1 =2). In addition, the coding unit 107 allocates Code2 and Code2 to the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1 and DOP2 allocated 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 coding Doppler phase rotation amount ψ for the transmitting antennas Tx#1 and Tx#2 in the beam direction B1, respectively. 2，1 (m), ψ 2，2 (m).

[0303] In addition, Fig.14 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#3 and Tx#4 in the beam direction B2. DM =3 among the Doppler multiplexed signals using the Doppler frequency shift amount DOP3 (N DM_B2 =1). In addition, the coding unit 107 allocates two codes, Code 1 and Code 2, to the Doppler multiplexed signal using the Doppler frequency shift amount DOP3 allocated to the transmitting antennas Tx#3 and Tx#4 in the beam direction B2. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#3 and Tx#4 in the beam direction B2. 1，3 (m), ψ 2，3 (m).

[0304] exist Fig.14 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2 is N. DM_B1 =2, N DM_B2 =1, which is a different Doppler multiplexing number, so A-2 of condition 1 is satisfied.

[0305] In addition, Fig.14 In the figure, the code indices assigned to each Doppler multiplexing signal using Doppler multiplexing signals DOP1, DOP2, and DOP3, and to the transmitting antenna of beam direction B1 and the transmitting antenna of beam direction B2 are CodeIndex_B1=(1, 1, *) and CodeIndex_B2=(*, 1&2), which are cyclically inconsistent and have different code index intervals, and therefore satisfy B-1 of condition 1.

[0306] In addition, Fig.14 In the figure, for each Doppler multiplexing signal using Doppler multiplexing signals DOP1, DOP2, and DOP3, the code multiplexing numbers allocated to the transmitting antenna in beam direction B1 and the transmitting antenna in beam direction B2 are N_Code_B1 = (1, 1, 0) and N_Code_B2 = (0, 0, 2), respectively. The code multiplexing numbers are different, so B-2 of condition 1 is satisfied.

[0307] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), an aliased Doppler frequency is observed in the Doppler analysis unit 210 described later. At this time, the code indexes are CodeIndex_B1_alias=(2, 2, *) and CodeIndex_B2_alias=(*, 1&2), which are different (circular inconsistency). Therefore, in Fig.14 In the example, in the range of the target's Doppler frequency -1 / (2Tr) ≦ fdtarget < -1 / (2Tr), the code index is cyclically inconsistent and the code interval is different. Therefore, B-1 and B-2 that meet condition 1 meet the conditions of different code multiplexing modes.

[0308] As mentioned above, Fig.14 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 1.

[0309] In addition, Fig.14 In the transmitting antenna of the beam direction B1, the code multiplexing number assigned to each Doppler multiplexing signal is N_Code_B1 = (1, 1, 0), and the code multiplexing number is uniform between the Doppler multiplexing signals for multiplexing transmission, and the code multiplexing number is included in 1 or more and N CM It is within the range of -1 or less, and therefore, condition 2 is satisfied.

[0310] On the other hand, Fig.14 In the transmitting antenna of beam direction B2, the code multiplexing number assigned to each Doppler multiplexing signal is N_Code_B2 = (0, 0, 2), and the Doppler multiplexing signals are multiplexed and transmitted with uneven code multiplexing numbers, but the code multiplexing number is not included in 1 or more and N CM The value is within the range of -1 or less, and therefore, condition 2 is not satisfied.

[0311] As mentioned above, Fig.14 The setting of the code Doppler phase rotation amount shown is a setting example in which the transmission antenna for the beam direction B1 satisfies the condition 2, but the transmission antenna for the beam direction B2 does not satisfy the condition 2.

[0312] The following describes the transmission antenna unit 109 including Fig.14 An example of a received signal in the output of the Doppler analysis unit 210 is described in which the Doppler frequency shift amount is set for transmitting antennas in different beam directions B1 and B2, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam direction B1 and beam direction B2).

[0313] For example, in the direction of the object Fig.10 In the case of the target direction (1) shown in FIG. 1 (for example, when the target exists in the periphery of the beam direction B1), or in the case of the target direction Fig.10 In the case of the target object direction (3) shown in the figure (for example, when the target object exists around the beam direction B2), the code multiplexing number is different between the transmitting antenna in the beam direction B1 and the transmitting antenna in the beam direction B2. Therefore, the radar device 10 can distinguish the case where the reception level of the received signal corresponding to the transmitting antenna in the beam direction B1 is reduced, and the case where the reception level of the received signal corresponding to the transmitting antenna in the beam direction B2 is reduced in the coded Doppler multiplexing and demultiplexing unit 212 described later.

[0314] Furthermore, when it is determined based on the determination result that the received signal is from the transmission antenna (Tx#1, Tx#2) in the beam direction B1, since the setting of the coded Doppler multiplexed signal for Tx#1 and Tx#2 in the beam direction B1 is known, the radar device 10 can demultiplex the multiplexed signal by, for example, the operation disclosed in Patent Documents 5 and 6. Furthermore, when it is determined that the received signal is from the transmission antenna (Tx#3, Tx#4) in the beam direction B2, since the setting of the coded Doppler multiplexed signal for Tx#3 and Tx#4 in the beam direction B2 is known, the radar device 10 can demultiplex the multiplexed signal in the same manner.

[0315] In addition, the setting of the code Doppler phase rotation amount by the phase rotation amount setting unit 105 in setting example 5 does not satisfy condition 2 for the beam direction B2. In this case, the detectable Doppler frequency range fd depends on the target object direction and is within the range of -1 / (2Tr)≦fd<1 / (2Tr) or -1 / (2Loc N DM_B2 Tr)≦fd<1 / (2Loc N DM_B2 Tr), the Doppler detection range can be expanded to a larger range than the Doppler detection range of the equally spaced DDM: -1 / (6Tr)≦fd<1 / (6Tr), depending on the target direction.

[0316] In the above, an example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 has been described.

[0317] In addition, the setting of the code Doppler phase rotation amount is not limited to the above-mentioned setting examples 1 to 5. For example, the number of transmission antennas Nt and the number of transmission antennas N in the beam direction B1 are B1 , the number of transmitting antennas N in beam direction B2 B2 , Doppler multiplexing number (N DM 、N DM_B1、N DM_B2 ), code multiplexing number (N CM 、N CM_B1 、N CM_B2 ), the number of multi-beams NB, the code interval, and the Doppler frequency shift interval may also be other values. In addition, the above setting examples 1 to 5 show the use of the code multiplexing number N CM =2 code setting example, but not limited to this, for example, even if the code multiplexing number N is set CM ≧3, the same setting of the code Doppler phase rotation amount can also be performed.

[0318] [Configuration of the radar receiving unit 200]

[0319] exist Figure 5 In the embodiment, the radar receiving unit 200 has a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. In addition, the radar receiving unit 200 includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a coded Doppler multiplexing and demultiplexing unit 212, and a direction estimation unit 213. In addition, the Na antenna system processing units 201-1 to 201-Na, the CFAR unit 211, the coded Doppler multiplexing and demultiplexing unit 212, and the direction estimation unit 213 can be collectively referred to as a "receiving circuit". In addition, the receiving circuit uses the reflected wave signal reflected by the transmission signal at the target (target) to estimate the direction of the target.

[0320] The receiving antennas Rx#1 to Rx#Na of the receiving antenna unit 202 receive reflected wave signals, which are radar transmission signals reflected by a target object (object), and output the received reflected wave signals to the corresponding antenna system processing unit 201 as received signals.

[0321] Each antenna system processing unit 201 includes a reception radio unit 203 and a signal processing unit 206 .

[0322] Each signal received by Na receiving antennas Rx#1 to Rx#Na is output to Na receiving wireless units 203. In addition, output signals from Na receiving wireless units 203 are output to Na signal processing units 206, respectively.

[0323] The receiving wireless unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the chirp signal as the transmission signal input from the radar transmission signal generating unit 101 with the received reflected wave signal. The receiving wireless unit 203, for example, passes the output of the mixer unit 204 through the LPF 205. As a result, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is output. For example, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulation wave) as the transmission signal (radar transmission wave) and the frequency of the reception chirp signal (reception frequency modulation wave) as the reception signal (radar reflected wave) is obtained as a beat frequency.

[0324] The signal processing unit 206 in each antenna system processing unit 201 - z (where z=any one of 1 to Na) includes an AD conversion unit 207 , a beat frequency analysis unit 208 , an output switching unit 209 , and a Doppler analysis unit 210 .

[0325] The signal (for example, the beat signal) output from the LPF 205 is converted into discrete sample data by the AD converter 207 in the signal processing unit 206 through discrete sampling.

[0326] The beat frequency analysis unit 208 analyzes the N signals obtained within a predetermined time range (range gate) according to the transmission period Tr. data The signal processing unit 206 performs frequency analysis processing (for example, FFT processing) on ​​discrete sample data. As a result, the signal processing unit 206 outputs a frequency spectrum having a peak at a beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave).

[0327] Here, the beat frequency response obtained by transmitting the m-th chirped pulse and outputted from the beat frequency analysis unit 208 in the z-th signal processing unit 206 is represented by “RFT z (f b , m)”. Here, f b represents the beat frequency index, which corresponds to the index (bin number) of the FFT. b =0, ..., (N data / 2)-1, z=1~Na, m=1~N C . Beat frequency index f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (for example, the closer the distance to the target object).

[0328] In addition, the beat frequency index f b It can be converted into distance information R(f b ). Therefore, in the following, the beat frequency index f b It is called the “distance index f b”.

[0329] [Formula 10]

[0330]

[0331] 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.

[0332] The output switching unit 209 selectively switches to the OC_INDEX-th Doppler analysis unit 210 among the Loc Doppler analysis units 210 and outputs the output of the beat frequency analysis unit 208 of each transmission cycle based on the orthogonal code element index OC_INDEX input from the encoding unit 107 of the phase rotation amount setting unit 105. For example, in the m-th transmission cycle Tr, the output switching unit 209 selects the OC_INDEX-th Doppler analysis unit 210 obtained by equation (8).

[0333] The signal processing unit 206 includes Loc Doppler analysis units 210-1 to 210-Loc. For example, the noc-th Doppler analysis unit 210 receives data once in each Loc-th transmission cycle (Loc×Tr) through the operation of the output switching unit 209. Therefore, the noc-th Doppler analysis unit 210 uses data of the Ncode-th transmission cycle in the Nc-th transmission cycle (for example, the beat frequency response RFT input from the beat frequency analysis unit 208). z (f b , m)), index f by each distance b Doppler analysis is performed. Here, noc is the index of the code element, noc = 1 to Loc.

[0334] For example, when Ncode is a power of 2, FFT processing can be applied to Doppler analysis. Here, the FFT size is Ncode, and the maximum Doppler frequency that does not cause aliasing is ±1 / (2Loc×Tr) derived from the sampling theorem. In addition, the Doppler frequency index f s The Doppler frequency interval is 1 / (Ncode×Loc×Tr), and the Doppler frequency index f s The range is f s =-Ncode / 2,...,0,...,Ncode / 2-1.

[0335] Hereinafter, as an example, a case where Ncode is a power of 2 is described. In addition, when Ncode is not a power of 2, FFT processing can be performed with a power of 2 as the data size (FFT size), for example, by including zero-padding data.

[0336] For example, the output VFT of the Doppler analysis unit 210 of the z-th signal processing unit 206 is z noc (f b , f s ) is represented by the following formula (11). In addition, j is an imaginary unit, and z=1 to Na.

[0337] [Formula 11]

[0338]

[0339] The above describes the processing in each component of the signal processing unit 206.

[0340] [Operation Example of CFAR Unit 211]

[0341] exist Figure 5 In the example, the CFAR unit 211 uses the outputs of the Loc Doppler analysis units 210 of the first to Na signal processing units 206 to perform CFAR processing (for example, threshold determination in an adaptive manner) to extract the distance index f that gives the peak signal. b_cfar and the Doppler frequency index f s_cfar .

[0342] For example, the CFAR unit 211 calculates the output VFT of the Doppler analysis unit 210 of the first to Na-th signal processing units 206 as shown in the following equation (12): z noc (f b , f s ) implements power addition, performs two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (equivalent to relative velocity), or performs CFAR processing combined with one-dimensional CFAR processing (for example, the processing disclosed in non-patent document 2 can be applied).

[0343] [Formula 12]

[0344]

[0345] The CFAR unit 211 sets the threshold in an adaptive manner and indexes the distances where the received power is greater than the threshold. b_cfar , Doppler frequency index f s_cfar , and received power information PowerFT(f b_cfar , f s_cfar ) is output to the coded Doppler multiplexing and demultiplexing unit 212.

[0346] In addition, for example, when using equation (5) as the formula for assigning the Doppler shift amount DOP ndm The phase rotation amount In the case where the intervals of the Doppler frequency shift amounts in the Doppler frequency domain in the output of the Doppler analysis unit 210 are equal intervals, when the intervals of the Doppler frequency indexes, i.e., the intervals of the Doppler frequency shift amounts, are represented by ΔFD, ΔFD=Ncode / N DM Therefore, in the output of the Doppler analysis unit 210, in the Doppler frequency domain, peaks are detected at intervals of ΔFD for each signal multiplexed with the Doppler shift.

[0347] Fig.15 (a) indicates that in N DM An example of the output of the Doppler analysis unit 210 at a distance where there are three reflected waves from targets when . Fig.15 As shown in (a), when the reflected waves of three targets are observed in Doppler frequency indices f1, f2 and f3, the reflected waves are also observed in Doppler frequency indices that are spaced ΔFD apart from f1, f2 and f3, respectively (for example, f1-ΔFD, f2-ΔFD, f3-ΔFD+Ncode).

[0348] Therefore, the CFAR unit 211 may divide each output of the Doppler analysis unit 210 into a range of intervals ΔFD of the Doppler frequency shift amount, and for each divided range, perform power addition at each signal peak position of the Doppler multiplexing as shown in the following equation (13) (for example, called "Doppler region compression"), and then perform CFAR processing (for example, called "Doppler region compression CFAR processing"). Here, f s_comp = -ΔFD / 2, ..., -ΔFD / 2-1. For example, when ΔFD = Ncode / N DM When f s_comp =Ncode / (2N DM ), ..., Ncode / (2N DM )-1.

[0349] [Formula 13]

[0350]

[0351] In addition, when the following conditions are satisfied in equation (13), the Doppler frequency index to which Ncode is added is used.

[0352] [Formula 14]

[0353]

[0354] Similarly, when the following condition is satisfied in equation (13), the Doppler frequency index from which Ncode is subtracted is further used.

[0355] [Formula 15]

[0356]

[0357] Fig.15 (b) indicates Fig.15 The output of the Doppler analysis unit 210 shown in (a) is an output example after the Doppler region compression processing shown in equation (13) is applied. Fig.15 As shown in (b), in N DM =2, the CFAR unit 211 adds the power component of the Doppler frequency index f1 and the power component of f1-ΔFD through the Doppler region compression process and outputs the result. Fig.15 As shown in (b), the CFAR unit 211 adds the power component of the Doppler frequency index f2 to the power component of f2-ΔFD and outputs the result. In addition, regarding the power component of the Doppler frequency index f3, since f3-ΔFD is smaller than -Ncode / 2, the CFAR unit 211 adds the power component of the Doppler frequency index f3 to f3-ΔFD+Ncode (for example, in N DM =2, the power components of f3+ΔFD) are added and output.

[0358] As a result of the Doppler region compression, the range of the Doppler frequency index fs_comp in the Doppler frequency domain is reduced to be greater than -ΔFD / 2, ..., less than ΔFD / 2-1 (in the case of ΔFD=Ncode / N DM In the case of -Ncode / (2N DM ) above, ..., Ncode / (2N DM )-1 or less).

[0359] The CFAR unit 211 using the Doppler region compression CFAR process sets a threshold in an adaptive manner, for example, and indexes the distances where the received power is greater than the threshold. b_cfar , 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) received power information PowerFT(f b_cfar , f s_comp_cfar +(nfd-ceil(N DM / 2)-1)×ΔFD), nfd=1,...,N DM The signal is output to the coded Doppler multiplexing and demultiplexing unit 212 .

[0360] [Operation Example of the Coded Doppler Multiplexing and Demultiplexing Unit 212]

[0361] Next, Figure 5 The operation example of the coded Doppler multiplexing and demultiplexing unit 212 shown in FIG.

[0362] In addition, an example of the processing of the coded Doppler multiplexing and demultiplexing unit 212 when the Doppler region compression CFAR processing is used in the CFAR unit 211 is described below. In addition, the operation of the coded Doppler multiplexing and demultiplexing unit 212 when omnidirectional antennas (or antennas having a directional characteristic that is substantially uniform within the field of view angle covered by the transmitting antennas in multiple beam directions) are used as multiple receiving antennas is described.

[0363] Fig.16 2 is a flowchart showing an example of the demultiplexing operation in the code-Doppler multiplexing and demultiplexing unit 212 .

[0364] <Step A-1>

[0365] The coded Doppler multiplexing demultiplexing unit 212 performs coded Doppler multiplexing demultiplexing processing on the Nt coded Doppler multiplexed signals.

[0366] For example, the coded Doppler multiplexing and demultiplexing unit 212 uses the distance index f input from the CFAR unit 211 to b_cfar , 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) received power information (PowerFT(f 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, demultiplexes the Nt coded Doppler multiplexed transmitted signals, and determines (e.g., determines or identifies) the transmitting antenna and the Doppler frequency (e.g., Doppler speed or relative speed).

[0367] It is utilized that, as described above, when the equal-interval Doppler frequency shift amount setting including the maximum equal-interval Doppler frequency shift amount setting is used, the encoding unit 107 of the phase rotation amount setting unit 105 does not set N DM The number of coded Doppler multiplexing N DOP_CODE (1) N DOP_CODE (2), ..., N DOP_CODE (N DM )All are set to N CM Instead, at least one coded Doppler multiplexing number is set to be less than N. CMThe case where the value of each is set (unevenly).

[0368] For example, (1) the code Doppler multiplexing demultiplexing unit 212 performs code demultiplexing processing and detects that the code Doppler multiplexing number is set to a value greater than N. CM The coded Doppler multiplexed signal (for example, unused coded Doppler multiplexed signals not used in multiplexed transmission) is detected and aliasing determination is performed. Then, (2) the coded Doppler multiplexed demultiplexing unit 212 performs Doppler code demultiplexing processing on the coded Doppler multiplexed signal used in multiplexed transmission based on the aliasing determination result.

[0369] The operation of such a coded Doppler multiplexing and demultiplexing unit 212 is the same as the operation of a coded Doppler multiplexing and demultiplexing unit in a MIMO radar using existing coded Doppler multiplexing transmission, and is described in, for example, Patent Documents 5 and 6, so the detailed operation description is omitted.

[0370] For example, in the case of the equal-interval Doppler frequency shift amount setting including the maximum equal-interval Doppler frequency shift amount setting, N is not set. DM The number of coded Doppler multiplexing N DOP_CODE (1) N DOP_CODE (2), ..., N DOP_CODE (N DM )All are set to N CM Instead, at least one coded Doppler multiplexing number is set to be less than N. CM In the case of the value of fd, the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) can be detected by the operation of the above-mentioned code-Doppler multiplexing and demultiplexing unit 212 (for example, Patent Documents 5 and 6).

[0371] <Step A-2>

[0372] The coded Doppler multiplexing and demultiplexing unit 212 determines whether Nt coded Doppler multiplexing signals are detected normally. The coded Doppler multiplexing and demultiplexing unit 212 performs the process of step A-3 if Nt coded Doppler multiplexing signals are detected normally, and performs the process of step B-1 if Nt coded Doppler multiplexing signals are not detected normally.

[0373] For example, in the process of step A-1, Nt coded Doppler multiplexed signals may not be detected normally depending on the consistency between the main beam direction of the multi-beam and the target object direction.

[0374] For example, suppose that a multi-beam MIMO radar is constructed using two transmitting antennas in beam directions B1 and B2, and the phase rotation amount setting unit 105 is set to N DM >N DM_B1 , or NDM >N DM_B2 (Here, N DM_B1 、N DM_B2 <N DM ). At this time, when the main beam direction of the multi-beam is inconsistent with the target direction and the target exists at zero azimuth, 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) is greater than a predetermined value, or contains a component whose received power is as low as the noise level. In this case, the coded Doppler multiplexed signal detected by the coded Doppler multiplex demultiplexing unit 212 is less than N DM Therefore, it is determined that the detection is not normal, and the processing of step B-1 is performed.

[0375] For example, for the transmission antenna in the beam direction B1, the phase rotation amount setting unit 105 sets the value N. DM =N DM_B1 , when the main beam direction B2 of the multi-beam is not consistent with the target direction and the target direction is at zero azimuth, or when the phase rotation amount setting unit 105 is set to N for the transmitting antenna in the beam direction B2 DM = DM_B2 , the main beam direction B2 of the multi-beam is inconsistent with the target direction, and the target direction is zero azimuth, 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) is within the specified range. In this case, when the code demultiplexing process is performed, the unused coded Doppler multiplexed signal that is not used in the multiplexed transmission is larger than the assumed (N DM =Nt) more, the aliasing determination of the coded Doppler multiplexing and demultiplexing unit 212 fails, and it is difficult to normally detect Nt coded Doppler multiplexed signals. DM -Nt) or more unused coded Doppler multiplexed signals that are not used in multiplexed transmission are detected, so it is determined that it is not a normal detection and the processing of step B-1 is performed.

[0376] <Step A-3>

[0377] The coded Doppler multiplexing demultiplexing unit 212 performs coded Doppler multiplexing demultiplexing processing on the coded Doppler multiplexed signal used in multiplexed transmission according to the aliasing determination result. z (f b_cfar , f s_comp_cfar , ncm, ndm) and the distance index f b_cfar and the Doppler frequency index f s_comp_cfar The two signals are outputted together to the direction estimation unit 213 .

[0378] 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 DOP was used. ndm and orthogonal code Code ndop_code(ndm) The output after demultiplexing of the coded Doppler multiplexed signal (for example, the demultiplexing result of the coded Doppler multiplexed signal). z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm) represents the received signal transmitted by the transmitting antenna Tx#[ndop_code(ndm), ndm] and reflected by the target object, and then received by the z-th antenna system processing unit 201. Here, z=1~Na, ncm=1~N CM In addition, ndm = 1 to N DM , ndop_code(ndm)=1~N DOP_CODE (ndm).

[0379] Furthermore, the code-Doppler multiplexing and demultiplexing unit 212 may output information related to the Doppler frequency of the detected target object to the direction estimating unit 213 , for example.

[0380] Furthermore, when condition 2 is satisfied, the code-Doppler multiplexing and demultiplexing unit 212 can detect the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0381] <Step B-1>

[0382] The coded Doppler multiplexing and demultiplexing unit 212 assumes that the target direction is the beam direction B1, and performs B1The present invention is to perform demultiplexing of a coded Doppler multiplexed signal.

[0383] For example, the coded Doppler multiplexing and demultiplexing unit 212 uses the distance index f input from the CFAR unit 211 to b_cfar , 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) received power information (PowerFT(f 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, demultiplexing N B1 The coded Doppler multiplexed transmitted signals are used to discriminate (eg, determine or identify) the transmitting antenna and the Doppler frequency (eg, Doppler velocity or relative velocity).

[0384] Here, in 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), sometimes the difference in received power is greater than the specified value, or there is a situation where (N DM -N DM_B1 ) The received power is as low as the noise level. It should be noted that when the phase rotation amount setting unit 105 is set to N DM =N DM_B1 In the case of (N DM -N DM_B1 )=0, and does not include a component whose received power is as small as the noise level. These Doppler multiplexed signals are unused Doppler multiplexed signals that are not used in multiplexed transmission.

[0385] Therefore, the coded Doppler multiplexing and 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(NDM / 2)-1)×ΔFD), extract the N with the highest power DM_B1 Doppler multiplexed signal.

[0386] For example, in the case where the extracted power ranks first, DM_B1 When the Doppler multiplexing interval of the Doppler multiplexing signal coincides with the Doppler multiplexing interval of the transmitting antenna assigned to the beam direction B1, (1) the coded Doppler multiplexing demultiplexing unit 212 performs code demultiplexing processing and detects that the coded Doppler multiplexing number is set to a value greater than N from the coded Doppler multiplexing signal assigned to the transmitting antenna of the beam direction B1. CM The coded Doppler multiplexed signal (for example, unused coded Doppler multiplexed signals not used in multiplexed transmission) is detected and aliasing determination is performed. Then, (2) the coded Doppler multiplexed demultiplexing unit 212 performs Doppler code demultiplexing processing on the coded Doppler multiplexed signal used in multiplexed transmission based on the aliasing determination result.

[0387] The operation of such a coded Doppler multiplexing and demultiplexing unit 212 is the same as the operation of a coded Doppler multiplexing and demultiplexing unit in a MIMO radar using existing coded Doppler multiplexing transmission, and is described in, for example, Patent Documents 5 and 6, so the detailed operation description is omitted.

[0388] In addition, by setting the coded Doppler phase rotation amount to satisfy condition 2, for example, through the operation of the coded Doppler multiplexing and demultiplexing unit 212 described above, the Doppler frequency of the target object estimated in the range of -1 / (2Tr)≦fd<1 / (2Tr) can be detected (for example, Patent Documents 5 and 6).

[0389] <Step B-2>

[0390] The coded Doppler multiplexing and demultiplexing unit 212 determines whether the N B1 N transmitting antennas B1 The coded Doppler multiplexing demultiplexing unit 212 generates N coded Doppler multiplexing signals. B1 When the coded Doppler multiplexed signal is detected normally, the process of step B-3 is performed, and when it is not detected normally, the process of step C-1 is performed.

[0391] For example, in the process of step B-1, N may not be detected normally depending on the consistency between the main beam direction of the multi-beam and the target direction. B1 Coded Doppler multiplexed signal.

[0392] For example, in the case where the extracted power ranks first, DM_B1 Doppler multiplexed signals are combined with other power signals (NDM -N DM_B1 ) When the power difference (or power ratio) between the two Doppler multiplexed signals does not reach a predetermined level or above, the coded Doppler multiplexing and demultiplexing unit 212 determines that the target object direction is not the beam direction B1 and performs the processing of step C-1.

[0393] In addition, the N with the most extracted power DM_B1 When the Doppler multiplexing interval of the Doppler multiplexed signal does not match the Doppler multiplexing interval assigned to the transmission antenna of the beam direction B1, the coded Doppler demultiplexing unit 212 determines that the target object direction is not the beam direction B1 and performs the process of step C-1.

[0394] For example, assume that for the beam direction B1, the setting of the phase rotation amount setting unit 105 is N DM_B1 =N DM_B2 At this time, when the main beam direction B2 of the multi-beam is inconsistent with the target direction and the target exists at zero azimuth, 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) is within the specified range. In this case, when the code demultiplexing process is performed, the unused coded Doppler multiplexed signal that is not used in the multiplexed transmission is different from the assumed N B1 The code intervals of the coded Doppler multiplexed signals are different. Therefore, the aliasing determination of the coded Doppler multiplexed demultiplexing unit 212 fails, and it is difficult to normally detect N B1 In this case, the coded Doppler multiplexing demultiplexing unit 212 determines that it is not for N B1 The normal detection of the coded Doppler multiplexed signal is performed and the processing of step C-1 is performed.

[0395] <Step B-3>

[0396] The coded Doppler multiplexing and demultiplexing unit 212 performs coding on the N beams in the beam direction B1 according to the processing result of step B-2. B1 The received signal YB1 after demultiplexing of the coded Doppler multiplexed signal used in the multiplexed transmission of the transmitting antennas z (f b_cfar , f s_comp_cfar , ncm, ndm) and the distance index f b_cfar and the Doppler frequency index fs_comp_cfar The two signals are outputted together to the direction estimation unit 213 .

[0397] 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 DOP was used. ndm and orthogonal code Code ndop_code(ndm) The output after demultiplexing of the coded Doppler multiplexed signal (for example, the demultiplexing result of the coded Doppler multiplexed signal). z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm) represents the N of beam direction B1 B1 The received signal is transmitted by the z-th transmitting antenna Tx#[ndop_code(ndm), ndm] and reflected by the target object, and then received by the z-th antenna system processing unit 201. Here, z=1 to Na. In addition, ndm=1 to N DM , ndop_code(ndm)=1~N DOP_CODE (ndm), except for N allocated to beam direction B1 B1 Except for the signal from the transmitting antenna, the output is zero.

[0398] Furthermore, the code-Doppler multiplexing and demultiplexing unit 212 may output the detected Doppler frequency of the target object to the direction estimating unit 213 .

[0399] Furthermore, when condition 2 is satisfied, the code-Doppler multiplexing and demultiplexing unit 212 can detect the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0400] <Step C-1>

[0401] The coded Doppler multiplexing and demultiplexing unit 212 assumes that the target direction is the beam direction B2, and performs B2 The present invention is to perform demultiplexing of a coded Doppler multiplexed signal.

[0402] For example, the coded Doppler multiplexing and demultiplexing unit 212 uses the distance index f outputted from the CFAR unit 211 to b_cfar , 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) received power information (PowerFT(f 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, demultiplexing N B2 The coded Doppler multiplexed transmitted signals are used to discriminate (eg, determine or identify) the transmitting antenna and the Doppler frequency (eg, Doppler velocity or relative velocity).

[0403] Here, in 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), sometimes the difference in received power is greater than the specified value, or there is a situation where (N DM -N DM_B2 ) The received power is as low as the noise level. It should be noted that when the phase rotation amount setting unit 105 is set to N DM =N DM_B2 In the case of (N DM -N DM_B2 )=0, and does not include a component whose received power is as small as the noise level. These Doppler multiplexed signals are unused Doppler multiplexed signals that are not used in multiplexed transmission.

[0404] Therefore, the coded Doppler multiplexing and 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), extract the N with the highest power DM_B2 Doppler multiplexed signal.

[0405] For example, in the case where the extracted power ranks first, DM_B2When the Doppler multiplexing interval of the Doppler multiplexing signal coincides with the Doppler multiplexing interval of the transmitting antenna assigned to the beam direction B2, (1) the coded Doppler multiplexing demultiplexing unit 212 performs code demultiplexing processing and detects that the coded Doppler multiplexing number is set to a value greater than N from the coded Doppler multiplexing signal assigned to the transmitting antenna of the beam direction B2. CM The coded Doppler multiplexed signal (for example, unused coded Doppler multiplexed signals not used in multiplexed transmission) is detected and aliasing determination is performed. Then, (2) the coded Doppler multiplexed demultiplexing unit 212 performs Doppler code demultiplexing processing on the coded Doppler multiplexed signal used in multiplexed transmission based on the aliasing determination result.

[0406] The operation of such a coded Doppler multiplexing and demultiplexing unit 212 is the same as the operation of a coded Doppler multiplexing and demultiplexing unit in a MIMO radar using existing coded Doppler multiplexing transmission, and is described in, for example, Patent Documents 5 and 6, so the detailed operation description is omitted.

[0407] In addition, by setting the coded Doppler phase rotation amount to satisfy condition 2, for example, through the operation of the coded Doppler multiplexing and demultiplexing unit 212 described above, the Doppler frequency of the target object estimated in the range of -1 / (2Tr)≦fd<1 / (2Tr) can be detected (for example, Patent Documents 5 and 6).

[0408] <Step C-2>

[0409] The coded Doppler multiplexing and demultiplexing unit 212 determines whether the N B2 N transmitting antennas B2 The coded Doppler multiplexing demultiplexing unit 212 generates N coded Doppler multiplexing signals. B2 If the coded Doppler multiplexed signal is detected normally, the process of step C-3 is performed, and if it is not detected normally, the process of step D is performed.

[0410] For example, in the process of step C-1, N may not be detected normally depending on the consistency between the main beam direction of the multi-beam and the target direction. B2 Coded Doppler multiplexed signal.

[0411] For example, in the case where the extracted power ranks first, DM_B2 Doppler multiplexed signals are combined with other power signals (N DM -N DM_B2 ) When the power difference (or power ratio) between the two Doppler multiplexed signals does not reach a predetermined level or above, the coded Doppler multiplexing and demultiplexing unit 212 determines that the target object direction is not the beam direction B2, and performs the processing of step D.

[0412] In addition, the N with the most extracted power DM_B2 When the Doppler multiplexing interval of the Doppler multiplexed signal does not match the Doppler multiplexing interval assigned to the transmission antenna of the beam direction B2, the coded Doppler demultiplexing unit 212 determines that the target object direction is not the beam direction B2 and performs the process of step D.

[0413] For example, assume that for the beam direction B2, the setting of the phase rotation amount setting unit 105 is N DM_B1 =N DM_B2 At this time, when the main beam direction B2 of the multi-beam is inconsistent with the target direction and the target exists at zero azimuth, 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) is within the specified range. In this case, when the code demultiplexing process is performed, the unused coded Doppler multiplexed signal that is not used in the multiplexed transmission is different from the assumed N B2 The code intervals of the coded Doppler multiplexed signals are different. Therefore, the aliasing determination of the coded Doppler multiplexed demultiplexing unit 212 fails, and it is difficult to normally detect N B2 In this case, the coded Doppler multiplexing demultiplexing unit 212 determines that it is not for N B2 The coded Doppler multiplexing signal is detected normally and the processing of step D is performed.

[0414] <Step C-3>

[0415] The coded Doppler multiplexing and demultiplexing unit 212 performs coding on the N beams in the beam direction B2 according to the processing result of step C-2. B2 The received signal YB2 after demultiplexing of the coded Doppler multiplexed signal used in the multiplexed transmission of the transmitting antennas z (f b_cfar , f s_comp_cfar , ncm, ndm) and the distance index f b_cfar and the Doppler frequency index f s_comp_cfar The two signals are outputted together to the direction estimation unit 213 .

[0416] 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 DOP was used. ndm and orthogonal code Code ndop_code(ndm) The output after demultiplexing of the coded Doppler multiplexed signal (for example, the demultiplexing result of the coded Doppler multiplexed signal). z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm) represents the N of beam direction B2 B2 The received signal is transmitted by the z-th transmitting antenna Tx#[ndop_code(ndm), ndm] and reflected by the target object, and then received by the z-th antenna system processing unit 201. Here, z=1 to Na. In addition, ndm=1 to N DM , ndop_code(ndm)=1~N DOP_CODE (ndm), except for N allocated to beam direction B2 B1 Except for the signal from the transmitting antenna, the output is zero.

[0417] Furthermore, the code-Doppler multiplexing and demultiplexing unit 212 may output the detected Doppler frequency of the target object to the direction estimating unit 213 .

[0418] Furthermore, when condition 2 is satisfied, the code-Doppler multiplexing and demultiplexing unit 212 can detect the Doppler frequency of the target object estimated within the range of -1 / (2Tr)≦fd<1 / (2Tr) by using the aliasing determination result.

[0419] <Step D>

[0420] When the condition of step C-2 is not satisfied, the coded Doppler multiplexing and demultiplexing unit 212 may determine that the received signal is a noise component or an interference component and may not output it to the direction estimation unit 213 .

[0421] In addition, in the above-mentioned operation example of the coded Doppler multiplexing demultiplexing unit 212, the case where the number of multi-beams NB=2 is described, but the number of multi-beams NB is not limited to this. For example, NB can also be greater than 3. For example, when the number of multi-beams NB=3, the coded Doppler multiplexing demultiplexing unit 212 can further continue the demultiplexing processing of Doppler multiplexing for beam directions different from beam directions B1 and B2 (or overlapping beam ranges or different beams. For example, beam direction B3) in step D (or between step C-2 and step D). As a result, even if the number of multi-beams is further increased, the demultiplexing operation of Doppler multiplexing can be performed in the same manner.

[0422] In the above, an operation example of the code-Doppler multiplexing and demultiplexing unit 212 has been described.

[0423] In addition, the distance index f input from the CFAR unit 211 b_cfar , Doppler frequency index f sddm_cfar and received power information (PowerFT(f b_cfar , f sddm_cfar +(ndm-1)×N Δfd )) When there are multiple coded Doppler multiplexing demultiplexing units 212, for example, can perform the above-mentioned coded Doppler multiplexing demultiplexing operation multiple times on the distance index, Doppler frequency index and reception power information respectively.

[0424] [Operation Example of Direction Estimation Unit 213]

[0425] Next, Figure 5 The operation example of the direction estimation unit 213 shown in FIG. 2 is described below.

[0426] In the following description, an example of operation of the direction estimation unit 213 is described when the multiple receiving antennas of the receiving antenna unit 202 are identical omnidirectional antennas or antennas having substantially uniform directional characteristics within the field of view of the transmitting antennas in multiple different beam directions.

[0427] The direction estimation unit 213 generates a signal (eg, a distance index f) input from the coded Doppler multiplexing / demultiplexing unit 212, for example. b_cfar , the received signal Y after demultiplexing by coded Doppler multiplexing 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), and perform the object target direction estimation process. Here, q=1 to NB. When the number of multi-beams is 2 (NB=2), q=1 or 2.

[0428] In addition, the received signal Y after the demultiplexing process of the coded Doppler multiplexing is z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm)) is derived from the coded Doppler phase rotation amount ψ ndop_code(ndm)，ndm (m), so it can correspond to the transmitting antennas Tx#1, Tx#2, ..., Tx#Nt.

[0429] Therefore, for the received signal Y z (f b_cfar , f s_comp_cfar , ndop_code(ndm), the coded Doppler phase rotation ψ in ndm) ndop_code(ndm)，ndm (m) uses the expression YT corresponding to any one of the transmitting antennas Tx#1 to Tx#Nt. z (f b_cfar , f s_comp_cfar , nt). Here, nt = 1 to Nt.

[0430] Similarly, for the received signal YBq z (f b_cfar , f s_comp_cfar , ndop_code(ndm), the coded Doppler phase rotation ψ in ndm) ndop_code(ndm)，ndm (m) uses the expression YBT corresponding to one of the transmitting antennas Tx#1 to Tx#Nt. z (f b_cfar , f s_comp_cfar , nt). Here, nt = 1 to Nt, q = 1 to NB. When the number of multi-beams is 2 (NB = 2), q = 1 or 2.

[0431] Hereinafter, operation example 1 and operation example 2 of the direction estimation unit 213 will be described.

[0432] <Operation Example 1 of Direction Estimation Unit 213>

[0433] In operation example 1, the direction estimation unit 213 uses the distance index f b_cfar and the received signal Y after the demultiplexing processing of the coded Doppler multiplexing z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), generates the virtual receiving array correlation vector h(f) of the direction estimation unit 213 shown in the following equation (14): b_cfar , f s_comp_cfar ) and perform direction estimation processing.

[0434] Here, the information input from the code Doppler multiplexing demultiplexing unit 212 includes the received signal Y after code Doppler multiplexing demultiplexing processing. z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), contains the coded Doppler multiplexed demultiplexed received signals for Nt transmitting antennas. Therefore, as shown in equation (14), the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar) contains Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. The direction estimation unit 213 uses the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ) and estimate the direction of the reflected wave signal from the target based on the phase difference between each transmitting and receiving antenna.

[0435] [Formula 16]

[0436]

[0437] In formula (14), h cal[b] b is an array correction value for correcting the phase deviation and amplitude deviation between the transmission antennas and the reception antennas. b = an integer from 1 to (Nt×Na).

[0438] The direction estimation unit 213 uses, for example, the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ), change the direction within the specified angle range to estimate the evaluation function P H (θ u , f b_cfar , f s_comp_cfar ) in the azimuth direction θ u , to calculate the spatial distribution.

[0439] The direction estimation unit 213 may extract a predetermined number of maximum peaks from the calculated maximum peaks of the spatial distribution in descending order, and output the azimuth directions of the maximum peaks as arrival direction estimation values ​​(eg, positioning output).

[0440] In addition, regarding the direction estimation evaluation function value P H (θ u , f b_cfar , f s_comp_cfar ), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0441] In addition, in the above example, the direction estimation unit 213 calculates the azimuth direction as an example of the estimated value of the arrival direction, but it is not limited to this. It is also possible to estimate the arrival direction in the elevation direction or to use MIMO antennas arranged in a rectangular grid to perform the arrival direction estimation in the azimuth direction and the elevation direction. For example, the direction estimation unit 213 can also calculate the azimuth direction and the elevation direction as the estimated value of the arrival direction for the transmitting antennas with different beam directions, and output them as positioning. In addition, this point can also be applied to the action example 2 of the direction estimation unit 213 described later.

[0442] Through the above operation, the direction estimation unit of the radar device 10 can output the positioning result according to the distance index f b_cfar and the received signal Y after the demultiplexing processing of the coded Doppler multiplexing z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), and outputs the estimated value of the arrival direction. In addition, as the positioning output, the direction estimation unit 213 can also output the distance index f b_cfar and the Doppler frequency estimate of the target.

[0443] In addition, the distance index f can also be converted into b_cfar This is converted into distance information and outputted. This point can also be applied to the operation example 2 of the direction estimation unit 213 described later.

[0444] In addition, the information input from the coded Doppler multiplexing and demultiplexing unit 212 (for example, the distance index f b_cfar , and the received signal Y after the demultiplexing processing of the coded Doppler multiplexing z (f b_cfar , f s_comp_cfar When there are multiple ndop_code(ndm), ndm)), the direction estimation unit 213 can calculate the arrival direction estimation values ​​for them in the same way as the above processing and output the positioning result.

[0445] <Operation Example 2 of Direction Estimation Unit 213>

[0446] In operation example 2, the direction estimation unit 213 uses the distance index f b_cfar and the received signal YBq after the demultiplexing processing of the coded Doppler multiplexing z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), generates the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), performs direction estimation processing based on the received signal from the transmitting antenna in the beam direction Bq.

[0447] Here, q = 1 to NB. For example, when the number of multi-beams NB = 2, q = 1 or 2. The operation in the case of NB = 2 will be described below as an example, but the value of NB is not limited to this.

[0448] The direction estimation unit 213 performs demultiplexing processing on the received signal YBq after the coded Doppler multiplexing z (f b_cfar, f s_comp_cfar , ndop_code(ndm), ndm) corresponding to the direction estimation processing of the beam direction Bq.

[0449] Here, the information input from the code Doppler multiplexing demultiplexing unit 212 includes the received signal YBq after code Doppler multiplexing demultiplexing processing. z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), contains the coded Doppler multiplexing and demultiplexing received signals for Nt transmitting antennas, but due to the exception of N Bq Since no received signal can be obtained except the coded Doppler multiplexing and demultiplexing signals of the transmitting antennas, a signal of zero value is included. Therefore, as shown in equation (15), the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar ) contains Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. The direction estimation unit 213 uses the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar ) and estimate the direction of the reflected wave signal from the target based on the phase difference between each transmitting and receiving antenna.

[0450] [Formula 17]

[0451]

[0452] For example, the transmitting antennas in beam direction B1 are Tx#1 and Tx#3, the transmitting antennas in beam direction B2 are Tx#2 and Tx#4, and N B1 =2,N B2 =2,N t =4, when the number of receiving antennas Na=4, the B1 beam antenna extraction vector SP of the received signal corresponding to the transmitting antenna in the beam direction B1 is extracted B1 , and a B2 beam antenna extraction vector SP for extracting a received signal corresponding to the transmitting antenna of the beam direction B2 B2 It can be expressed as 16(=N) using the following formula (16) or (17). t Here, the superscript T represents the vector transpose.

[0453] [Formula 18]

[0454] SP B1 =[1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0] T (16)

[0455] [Formula 19]

[0456] SP B2 =[0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1] T (17)

[0457] The direction estimation unit 213 uses, for example, the B1 beam antenna to extract the vector SP B1 The element index of the element with 1 is the element index of the virtual receiving array related vector h1(f b_cfar , f s_comp_cfar ) extracts the element components of the element index and arranges them in ascending order according to the element index, and uses the arranged column vector as the virtual receiving array correlation vector h based on the B1 beam antenna B1 (f b_cfar , f s_comp_cfar ) is generated. For example, the B1 beam antenna extraction vector SP shown in equation (16) B1 The first to fourth and ninth to twelfth elements of the element index of are 1. In this case, the direction estimation unit 213 obtains the virtual receiving array correlation vector h1(f b_cfar , f s_comp_cfar ), extract the element components in the order of the 1st to 4th, 9th to 12th element indexes, and generate the B1 beam antenna virtual receiving array correlation vector h B1 (f b_cfar , f s_comp_cfar ).

[0458] Similarly, the direction estimation unit 213 uses, for example, the B2 beam antenna to extract the vector SP B2 The element index of the element with 1 is the element index of the virtual receiving array related vector h2(f b_cfar , f s_comp_cfar ) extracts the element components of the element index and arranges them in ascending order according to the element index, and uses the arranged column vector as the virtual receiving array correlation vector h based on the B2 beam antenna B2 (f b_cfar , f s_comp_cfar ) is generated. For example, the B2 beam antenna extraction vector SP shown in equation (17) B2 The 5th to 8th and 13th to 16th elements of the element index of are 1. In this case, the direction estimation unit 213 calculates the direction of the virtual receiving array correlation vector h2(f b_cfar , f s_comp_cfar ), extract the element components in the order of the 5th to 8th and 13th to 16th element indexes, and generate the B2 beam antenna virtual receiving array correlation vector h B2 (f b_cfar , f s_comp_cfar ).

[0459] The direction estimation unit 213 uses, for example, a Bq beam antenna virtual receiving array correlation vector h Bq (f b_cfar , f s_comp_cfar ), change the direction within the specified angle range to estimate the evaluation function P H-Bq (θ u , f b_cfar , f s_comp_cfar ) in the azimuth direction θ u , to calculate the spatial distribution based on each Bq beam. Here, q=1 or 2.

[0460] The direction estimation unit 213 can extract a specified number of maximum peaks from the maximum peaks of the spatial distribution of the received signal corresponding to the transmitting antenna based on the calculated beam direction Bq in order from large to small, and output the azimuth direction of the maximum peak as an arrival direction estimation value based on the Bq beam (for example, positioning output).

[0461] In addition, regarding the direction estimation evaluation function value P H-Bq (θ u , f b_cfar , f s_comp_cfar ), there are various methods based on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 can also be used.

[0462] Through the above operation, the direction estimation unit 213 of the radar device 10 can output the positioning result according to the distance index f b_cfar and a received signal YB after code-Doppler multiplexing, which is a received signal from the transmitting antenna in the beam direction Bq. z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), and outputs the estimated arrival direction based on the Bq beam. In addition, as the positioning output, the direction estimation unit 213 can also output the distance index f b_cfar and the Doppler frequency estimate of the target.

[0463] In addition, the information input from the coded Doppler multiplexing and demultiplexing unit 212 (for example, the distance index f b_cfar , and the received signal YBq after the demultiplexing processing of the coded Doppler multiplexing z (f b_cfar , f s_comp_cfar When there are multiple ndop_code(ndm), ndm)), the direction estimation unit 213 can calculate the arrival direction estimation values ​​for them in the same way as the above processing and output the positioning result.

[0464] In the above, operation example 1 and operation example 2 of the direction estimation unit 213 have been described.

[0465] Next, an example of arrangement of the MIMO antenna and an example of operation of the direction estimation unit 213 when the example of arrangement of the MIMO antenna is used will be described. In the following, the transmission antenna and the reception antenna in the MIMO radar are collectively referred to as MIMO antennas.

[0466] In the following description, each transmitting antenna included in the transmitting antenna unit 109 may be, for example, Fig.17 As shown in FIG. 1 , a plurality of planar patch antennas are arranged in a subarray structure in the longitudinal and transverse directions. Fig.17 In the example, the transmitting antenna is composed of 8 planar patch antennas in the vertical direction and 4 planar patch antennas in the horizontal direction. For example, by changing the power supply phase for each patch antenna included in a transmitting antenna, a beam pattern (element pattern of the transmitting antenna) in which a directional beam is directed in a desired direction can be formed. In addition, for example, the more planar patch antennas in the horizontal (or vertical) direction that constitute a transmitting antenna, the sharper the directional beam in the horizontal (or vertical) direction can be formed. For example, a transmitting antenna can be composed of a number of planar patches that meet the desired beam width.

[0467] In addition, the structure of a transmitting antenna is not limited to Fig.17 In the example shown, 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 Fig.17 In addition, one transmitting antenna is not limited to a planar patch antenna, and may be a structure in which patch antennas are arranged in one of the longitudinal and lateral directions. In addition, the structures of the patch antennas of the plurality of transmitting antennas may be different.

[0468] Next, as an example, a configuration example of MIMO antennas when two transmission antennas are associated with each transmission beam will be described. For example, each transmission beam may be formed by two transmission antennas.

[0469] Below, as an example, the antenna configuration of a MIMO radar with the number of transmitting antennas Nt=4 (for example, Tx#1, Tx#2, Tx#3, Tx#4) and the number of receiving antennas Na=3 (for example, Rx#1, Rx#2, Rx#3) is described.

[0470] For example, Fig.18 or Fig.19 As shown, the transmitting antennas Tx#1, Tx#2, Tx#3, and Tx#4 have different directivity patterns with different transmission beam directions (or directional beam directions). Fig.18 and Fig.19In FIG. 1 , Tx#1 and Tx#2 are the directivity patterns of beam direction B1 (beam B1), and Tx#3 and Tx#4 are the directivity patterns of beam direction B2 (beam B2). Fig.18 and Fig.19 As shown, the number of transmitting antennas with the directivity pattern having the beam direction B1 and the number of transmitting antennas with the directivity pattern having the beam direction B2 are 2, N B1 =2, N B2 =2.

[0471] In addition, below, the directivity of the receiving antenna (e.g., Rx#1, Rx#2, Rx#3) can be non-directional, or a directional characteristic that is roughly uniform within the field of view of the transmitting antenna (e.g., Tx#1, Tx#2, Tx#3, Tx#4) in multiple beam directions.

[0472] For example, when the number of transmission antennas for multiplex transmission is Nt=4, the radar device 10 uses the code or Doppler multiplexed signal (Doppler multiplexed number Nt) of setting example 1 as the setting of the code Doppler phase rotation amount in the phase rotation amount setting unit 105. DM =3, code multiplexing number N CM =2), to send the radar transmission signal. In this case, for example, in the setting of the above-mentioned Doppler frequency shift amount, N can be applied B1 =2, N B2 =2 Doppler multiplexing signal allocation.

[0473] In addition, for example, virtual reception antenna (or MIMO virtual antenna) configurations VA#1 to VA#12 are composed of transmission antennas Tx#1, Tx#2, Tx#3, Tx#4 and reception antennas Rx#1, Rx#2, Rx#3.

[0474] Here, the configuration of the virtual receiving antenna (virtual receiving array) can be based on, for example, the position of the transmitting antenna constituting the transmitting antenna unit 109 (for example, the position of the power supply point) and the position of the receiving antenna constituting the receiving antenna unit 202 (for example, the position of the power supply point), as expressed by the following equation (18).

[0475] [Formula 20]

[0476]

[0477] Here, the position coordinates of the transmission antenna (for example, Tx#n) constituting the transmission antenna unit 109 are represented as (X T_#n , Y T_#n )(for example, n=1, ..., Nt), the position coordinates of the receiving antenna (for example, Rx#z) constituting the receiving antenna unit 202 are expressed as (X R_#z , Y R_#z)(for example, z=1, ..., Na), the position coordinates of the virtual antenna VA#b constituting the virtual receiving array antenna are expressed as (X V_#b , Y V_#b )(for example, b=1,…,Nt×Na).

[0478] In addition, in the formula (18), for example, VA#1 is expressed as the position reference (0, 0) of the virtual receiving array.

[0479] Next, an example of MIMO antenna configuration is described. T_#n Indicates the horizontal position coordinate, Y T_#n The description is given by indicating the position coordinates in the vertical direction, but the present invention is not limited to this.

[0480] Fig.18 and Fig.19 An example of a configuration of a transmitting antenna and a receiving antenna (MIMO antenna configuration) for a MIMO radar is shown below. Fig.18 The example of MIMO antenna configuration shown is referred to as "Configuration Example A". Fig.19 The example of the MIMO antenna configuration shown is referred to as "Configuration Example B". Fig.18 and Fig.19 (a) shows an example of the configuration of MIMO antennas (Tx#1, Tx#2, Tx#3, Tx#4, Rx#1, Rx#2, Rx#3). Fig.18 and Fig.19 (b) indicates that Fig.18 and Fig.19 An example of arrangement of virtual receiving antennas (VA#1 to VA#12) configured by the MIMO antenna arrangement of (a).

[0481] like Fig.18 and Fig.19 As shown in (a), in configuration example A and configuration example B, receiving antennas Rx#1, Rx#2, and Rx#3 are arranged in the horizontal direction ( Fig.18 and Fig.19 In the configuration examples A and B, the transmitting antennas Tx#1 and Tx#2 corresponding to the beam direction B1 are arranged at intervals of Dr in the horizontal direction (Dt=Dr), and in the vertical direction ( Fig.18 and Fig.19 In the configuration example A and the configuration example B, the transmitting antennas Tx#3 and Tx#4 corresponding to the beam direction B2 are arranged at intervals of Dt in the horizontal direction and at different positions (for example, at intervals of Dv) in the vertical direction. In addition, as Fig.18 and Fig.19As shown in (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 spaced apart in the horizontal direction at a spacing (for example, a spacing of 3Dr) that is larger than the aperture (2Dr) of the receiving antennas Rx#1, Rx#2, and Rx#3.

[0482] For example, in Fig.18 and Fig.19 The configuration of the transmitting antennas Tx#1, Tx#2, Tx#3, and Tx#4 shown in (a) is (X T_#1 , Y T_#1 )=(0,0)、(X T_#2 , Y T_#2 )=(D r , D V )、(X T_#3 , Y T_#3 )=(3Dr,0)、(X T_#4 , Y T_#4 )=(D t +3D r , D V ), and the configuration of receiving antennas Rx#1, Rx#2, and Rx#3 is (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 , ay), the position coordinates of the virtual antennas VA#1 to VA#12 constituting the virtual receiving antennas are calculated by equation (18). Here, ax and ay are arbitrary constants.

[0483] For example, the position coordinates of virtual antennas VA#1 to VA#12 are as follows: Fig.18 and Fig.19 As shown in (b), it does not depend on ax and ay, but is respectively (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 +Dr , 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 , Y V_#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 ).

[0484] Here, in configuration example A ( Fig.18 ) shows a configuration example using Dt=Dr. In addition, in configuration example B ( Fig.19 ) shows an example of the configuration of Dr and Dt using an absolute value of the difference between Dt and Dr of about 0.5 wavelengths (|Dt-Dr|≒0.5). For example, Fig.19 This is a configuration example of Dt=1.5Dr, and shows an example of Dt-Dr=Dr / 2. For example, if Dt=1.5 wavelengths and Dr=1 wavelength, then Dt-Dr=Dr / 2=0.5 wavelength.

[0485] For example, in the operation example 1 of the direction estimation unit 213, the information input from the coded Doppler multiplexing demultiplexing unit 212 includes the received signal Y after the coded Doppler multiplexing demultiplexing process. z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm), the direction estimation unit 213 generates the virtual receiving array correlation vector h(f) shown in equation (14) b_cfar , f s_comp_cfar ) and perform direction estimation processing.

[0486] Here, the received signal based on the b-th virtual antenna VA#b is represented by the virtual receiving array correlation vector h(f b_cfar , f s_comp_cfar ). b = an integer from 1 to (Nt×Na).

[0487] The received signal Y after the demultiplexing process of the coded Doppler multiplexing input from the coded Doppler multiplexing demultiplexing unit 212 is z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm) contains the coded Doppler demultiplexed signal for Nt transmit antennas. This is the direction of the target object, for example Fig.10 The case of the target object direction (2) shown corresponds to the case where the beam directions of the transmitting antennas Tx#1, Tx#2, Tx#3, and Tx#4 overlap. In this case, the radar transmission signals from the transmitting antennas Tx#1, Tx#2, Tx#3, and Tx#4 are reflected by the target object and received by the receiving antennas Rx#1, Rx#2, and Rx#3. Therefore, in this case, the direction estimation unit 213 can use the received signals of the virtual antennas VA#1 to VA#12 corresponding to Tx#1, Tx#2, Tx#3, and Tx#4 to perform direction estimation.

[0488] exist Fig.18 and Fig.19 In the MIMO antenna configuration of (a), Tx#1 and Tx#2 have the directional characteristics of beam direction B1, and Tx#3 and Tx#4 have the directional characteristics of beam direction B2, which correspond to different beam directions. Fig.10 As shown in FIG. 1 , the beam direction B1 and the beam direction B2 overlap in an angular region within a range of about the beam width. Fig.18 and Fig.19 As shown in (a), in the configurations of Tx#1 and Tx#2, and in the configurations of Tx#3 and Tx#4, an offset is made in the vertical direction (for example, an offset value Dv), so that the direction estimation unit 213 can perform angle measurement in the vertical direction in addition to the horizontal direction. The configurations of Tx#1 and Tx#2 and the configurations of Tx#3 and Tx#4 are respectively the following configurations, which make it possible for the target to exist in the overlapping area of ​​the beam direction B1 and the beam direction B2 (for example, Fig.10 When the target object direction (2) is shown, the aperture length of the virtual receiving antenna is expanded in the horizontal direction, and the estimation accuracy and angle resolution of the horizontal direction in the angle measurement processing of the direction estimation unit 213 are improved.

[0489] In addition, in configuration example A, if Fig.18As shown in the configuration of Tx#1 and Tx#2 (or, the configuration of Tx#3 and Tx#4) shown in (a), the horizontal offset Dt is Dt=Dr. In this way, Tx#1 and Tx#2 (or, Tx#3 and Tx#4) are arranged with an element spacing equal to the element spacing Dr of the receiving antennas Rx#1, Rx#2, and Rx#3 offset in the horizontal direction. Therefore, Fig.18 As shown in (b), the virtual receiving antenna configuration includes a configuration in which the horizontal positions of multiple virtual antennas (e.g., VA#2 and VA#4, or VA#3 and VA#5) are consistent but the vertical positions differ by Dv. With such a configuration of virtual receiving antennas, the direction estimation unit 213 can, for example, simply perform vertical angle measurement based on the reception phase difference between two virtual antennas (e.g., VA#2 and VA#4, or VA#3 and VA#5) that are consistent in horizontal positions.

[0490] In addition, as in Fig.19 As shown in the configuration of Tx#1 and Tx#2 (or the configuration of Tx#3 and Tx#4) shown in (a), configuration example B is a configuration of Dr and Dt in which the absolute value of the difference between Dt and Dr is about 0.5 wavelengths (|Dt-Dr|≒0.5). By configuring in this way, for example, Fig.19 As shown in (b), the interval between virtual antennas VA#2 and VA#4 (or, the interval between VA#3 and VA#5, the interval between VA#7 and VA#6, the interval between VA#8 and VA#10, and the interval 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 transmission antenna interval Dt and the reception antenna interval Dr is set to half a wavelength, in the radar device 10, grating lobes can be suppressed within a field of view angle of ±90°. For example, when Dt=1.5λ and Dr=1λ, Dt-Dr=0.5λ.

[0491] In addition, the case where the difference between Dt and Dr |Dt-Dr| (specified value) is set to half the wavelength (0.5λ) is described, but the present invention is not limited to this. For example, |Dt-Dr| can also be set to a value in the range of about 0.45λ to 0.8λ (for example, a value in the range of 0.5 to 0.8 times the wavelength of the radar signal).

[0492] |Dt-Dr| can be set, for example, according to the field of view of the radar device 10 in the horizontal direction, and the grating lobe within the field of view can be suppressed. For example, in the case of a wide field of view in the range of about ±70 degrees to ±90 degrees in the horizontal direction, |Dt-Dr| can be set to about 0.5λ. Alternatively, in the case of a narrow field of view in the range of about ±20 degrees to ±40 degrees in the horizontal direction, |Dt-Dr| can be set to about 0.7λ as a wider interval, for example.

[0493] In the above-mentioned operation example 2 of the direction estimation unit 213, the direction estimation unit 213 generates a signal YB1 after demultiplexing of the coded Doppler multiplexing input from the coded Doppler multiplexing demultiplexing unit 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), generates 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 ) or, and perform direction estimation processing.

[0494] Here, the received signal based on the b-th virtual antenna VA#b is represented by the virtual receiving array correlation vector hq(f b_cfar , f s_comp_cfar ) is represented by the bth element of . Here q=1 or 2.

[0495] The received signal YBq after the code-Doppler multiplexing demultiplexing process input from the code-Doppler multiplexing demultiplexing unit 212 is z (f b_cfar , f s_comp_cfar , ndop_code(ndm), ndm) contains the Bq The received signal of the transmitting antenna with a beam direction Bq. This is the direction of the target, for example Fig.10 The case of the target object direction (1) (e.g., beam direction B1) or the target object direction (3) (e.g., beam direction B2) shown is the case corresponding to the area of ​​beam direction Bq. In this case, the radar transmission signal from the transmission antenna in beam direction Bq is reflected by the target object and received by the receiving antennas Rx#1, Rx#2, and Rx#3.

[0496] Therefore, in this case, for example, when q=1 (the direction of the object is Fig.10In the case of the target object direction (1) shown in the figure), the direction estimation unit 213 can use the received signals of the virtual antennas VA#1 to VA#6 corresponding to the transmitting antennas Tx#1 and Tx#2 included in the beam direction B1 to perform direction estimation. In addition, for example, in the case of q=2 (the target object direction is Fig.10 In the case of the target object direction (3) shown in FIG. 1 ), the direction estimation unit 213 can perform direction estimation using the received signals of the virtual antennas VA#7 to VA#12 corresponding to the transmitting antennas Tx#3 and Tx#4 included in the beam direction B2.

[0497] In addition, in configuration example A, Fig.18 In (a), Dt and Dr can be set to be, for example, more than one wavelength. In this case, the result of the direction estimation processing in the direction estimation unit 213 may cause ambiguity in the horizontal direction estimation due to the presence of grating lobes. On the other hand, the direction estimation unit 213 estimates the received signal Y after the coded Doppler multiplexing demultiplexing processing input from the coded Doppler multiplexing demultiplexing unit 212, for example. 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), and direction estimation processing is performed. Thus, the direction estimation unit 213 can determine whether the target object exists in the beam direction B1, the beam direction B2, and the direction of the overlapping area of ​​the beam direction B1 and the beam direction B2. Therefore, even if a grating lobe appears, the true value direction can be detected.

[0498] In addition, Dv in configuration examples A and B can be set to values ​​of about 0.45λ to 0.8λ (for example, a value in the range of 0.5 to 0.8 times the wavelength of the radar transmission signal). Dv can be set, for example, according to the vertical field of view of the radar device 10. For example, in the case of a wide field of view in the range of about ±70 degrees to ±90 degrees in the vertical direction, Dv can be set to about 0.5λ. Alternatively, in the case of a narrow field of view in the range of about ±20 degrees to ±40 degrees in the vertical direction, Dv can be set to about 0.7λ as a wider interval.

[0499] Here, λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, when a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency of the frequency sweep band of the chirp signal.

[0500] In addition, in configuration examples A and B, the configuration of the receiving antennas (Rx#1, Rx#2, Rx#3) is described as being arranged at the same position in the vertical direction and being arranged at equal intervals with each antenna being offset by an interval Dr. However, the configuration of the receiving antennas is not limited thereto. For example, in the horizontal configuration of the receiving antennas, the intervals between the receiving antennas may be unequal intervals.

[0501] In addition, the MIMO antenna configuration described in Configuration Example A and Configuration Example B is only an example and is not limited to this. For example, it is also possible to further configure other antennas (at least one of the transmitting antenna and the receiving antenna) for the MIMO antenna configuration described in Configuration Example A and Configuration Example B. In addition, it is also possible to configure the antenna in which the horizontal direction and the vertical direction are swapped in Configuration Example A and Configuration Example B. In addition, the spacing between the transmitting antennas described in Configuration Example A and Configuration Example B can be applied to the spacing between the receiving antennas, and the spacing between the receiving antennas described in Configuration Example A and Configuration Example B can be applied to the spacing between the transmitting antennas.

[0502] By operating as described above, in multi-beam transmission, the direction estimation unit 213 can perform direction estimation processing in response to the fact that the demultiplexing operation of the code-Doppler multiplexing / demultiplexing unit 212 differs depending on the target object direction.

[0503] For example, when the coded Doppler multiplexing and demultiplexing unit 212 is capable of demultiplexing Doppler multiplexed signals from all transmitting antennas (for example, 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 the received signals of Nt×Na virtual receiving antennas.

[0504] For example, when the coded Doppler multiplexing and demultiplexing unit 212 can demultiplex the Doppler multiplexing signal from the transmitting antenna in the beam direction Bq (for example, in the case of the target object direction (1) or (3)), the direction estimating unit 213 uses N Bq The direction of the received signals of ×Na virtual receiving antennas is estimated, which can improve the angle measurement accuracy and angle measurement resolution.

[0505] In the above, an operation example of the direction estimation unit 213 has been described.

[0506] As described above, in the present embodiment, the radar device 10 allocates coded Doppler multiplexing signals (for example, signals having at least one different Doppler multiplexing mode and code multiplexing mode) that satisfy at least condition 1 and are different between multi-beams in the phase rotation amount setting unit 105 in a multi-beam transmission MIMO radar using coded Doppler multiplexing. As a result, in the radar device 10, even when the reception levels of reflected waves corresponding to transmission antennas having different directional characteristics are greatly different, the transmission antenna can be identified in the coded Doppler multiplexing demultiplexing unit 212, and coded Doppler multiplexing demultiplexing can be performed. Therefore, according to the present embodiment, it is possible to suppress degradation of target detection performance, misestimation of Doppler frequency, or degradation of angle measurement performance.

[0507] In addition, for example, when the aforementioned conditions 1 and 2 are satisfied in the allocation of the coded Doppler multiplexed signal in the phase rotation amount setting unit 105, in the radar device 10, even when the reception levels of reflected waves corresponding to transmitting antennas having different directional characteristics are greatly different, the detectable Doppler frequency range fd is within the range of -1 / (2Tr)≦fd<1 / (2Tr), and can be expanded to the same Doppler frequency range as that when a single transmitting antenna is used.

[0508] In addition, in the radar device 10 of the present embodiment, as a multi-beam transceiver MIMO radar structure, Doppler multiplexing demultiplexing can be performed without using the following beam direction determination processing, thereby reducing the amount of reception processing calculation. The beam direction determination processing is a processing using a directional receiving antenna (or a directional receiving processing using a receiving array antenna).

[0509] In addition, for example, when receiving antennas with different beam directions are used as receiving antennas in a multi-beam transmission and reception MIMO radar structure, the number of receiving antennas available for angle measurement may decrease depending on the target object direction, and thus the angle measurement accuracy or angle measurement resolution of the radar device 10 may decrease. In the present embodiment, for example, it is possible to perform demultiplexing of Doppler multiplexing regardless of the target object direction without using a directional receiving antenna, thereby suppressing the decrease in angle measurement accuracy and angle measurement resolution.

[0510] Therefore, according to the present embodiment, the detection performance of a multi-beam transmission MIMO radar using coded Doppler multiplexing transmission can be improved.

[0511] (Variant 1)

[0512] In the above embodiment, the case where the number of multi-beams NB=2 is described, but the number of multi-beams NB may be greater than or equal to 3. In Modification 1, the case where the number of multi-beams NB≧3 is described.

[0513] When the number of multi-beams NB≧3, the above-mentioned condition 1 can be replaced by the later-described conditions 1-a and 1-b applied to the setting of the coded Doppler phase rotation amount performed by the phase rotation amount setting unit 105. Thus, as in the above-mentioned embodiment, even when the received power levels of the reflected waves between the received signals corresponding to the transmitting antennas in different beam directions are greatly different, the Doppler multiplexed signal can be demultiplexed, thereby achieving the effect of suppressing the degradation of the positioning performance and the radar detection performance.

[0514] Hereinafter, an example of setting conditions for setting the code Doppler phase rotation amount by the phase rotation amount setting unit 105 when the multi-beam number NB≧3 will be described.

[0515] For example, in the transmitting antenna unit 109, for different Q beam directions Bq, (N B1 , N B2 , ..., N BQ ) transmitting antennas in each beam direction. For example, the phase rotation amount setting unit 105 of the radar transmitting unit 100 of the MIMO radar (for example, the radar device 10) performing multi-beam transmission non-uniformly sets the coded Doppler multiplexing number N for the Doppler multiplexed signal. DOP_CODE (ndm), and set the code Doppler phase rotation amount ψ so as to satisfy the following <condition 1-a> and <condition 1-b> ndop_code(ndm)，ndm (m). Here, ndm = 1 to N DM , ndop_code(ndm)=1~N DOP_CODE (ndm).

[0516] <Condition 1-a>

[0517] The phase rotation amount setting unit 105 sets the code Doppler phase rotation amount ψ that satisfies different Doppler multiplexing mode conditions, different code multiplexing mode conditions, or different Doppler multiplexing and code multiplexing mode conditions for the transmitting antenna in each beam direction Bq according to the beam direction. ndop_code(ndm)，ndm (m). Here, q = 1 to Q.

[0518] <Condition 1-b>

[0519] When an overlapping field angle region is included between the beam directions Bq, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ in such a manner that different code multiplexing mode conditions or different Doppler multiplexing and code multiplexing mode conditions are satisfied when a group of multiple transmitting antennas (hereinafter referred to as a "transmitting antenna set") included in the overlapping region (or, referred to as the overlapping beam region) is taken into consideration. ndop_code(ndm)，ndm (m). Here, q = 1 to Q.

[0520] The transmission antennas assigned to each beam Bq and the codes and Doppler multiplexed signals of the transmission antenna sets included in the overlapping region satisfy at least one of the following conditions.

[0521] For example, the different Doppler multiplexing mode conditions may be one of the following conditions (eg, also referred to as "condition 1A-a").

[0522] (A-1) The Doppler multiplexing number corresponding to each beam direction is the same, and each beam direction contains a different Doppler interval (limited to N DM_Bq ≧2).

[0523] (A-2) The Doppler multiplexing numbers of the respective beam directions are different.

[0524] (A-3) When the Doppler multiplexing number is 3 or more, when the same Doppler interval is included in the Doppler shift intervals in each beam direction, the order of the Doppler intervals is different (the cycle is inconsistent).

[0525] In addition, the different code multiplexing mode condition may be one of the following conditions (for example, also referred to as "condition 1B-a").

[0526] (B-1) The code intervals (code index intervals) assigned to the respective Doppler multiplexed signals are different (not cyclically consistent).

[0527] (B-2) The code multiplexing numbers assigned to the respective Doppler multiplexed signals are different (circular inconsistency).

[0528] Here, when the number of multi-beams NB ≧ 3, the number of transmitting antennas Nt ≧ 4, and the number of Doppler multiplexing N DM ≧2, maximum code reuse number N CM ≧2, Nt <N DM ×N CM In addition, the number of transmitting antennas in beam direction Bq is recorded as N Bq . N Bq ≧1, the total number of transmitting antennas in each beam direction Bq is Nt (N B1 +N B2 +...+N Bq =Nt). In addition, the Doppler multiplexing number of the transmission antenna assigned to the beam direction Bq is recorded as N DM_Bq . N DM_Bq <N DM .

[0529] In addition, for different Q beam directions Bq, (N B1 , N B2 , ..., N BQIn a MIMO radar (for example, the radar device 10) that performs multi-beam transmission using a plurality of transmitting antennas in each beam direction, the phase rotation amount setting unit 105 of the radar transmitting unit 100 may set, for example, a code Doppler phase rotation amount ψ that satisfies the following conditions 2-a and 2-b in addition to the conditions 1-a and 1-b. ndop_code(ndm)，ndm (m).

[0530] <Condition 2-a>

[0531] The signals transmitted from the transmission antennas of each beam Bq are multiplexed and transmitted with a code multiplexing number that is not uniform between Doppler multiplexed signals. The code multiplexing number may be greater than 1 and N CM A certain number within the range of -1 or less. Here, q=1~Q.

[0532] <Condition 2-b>

[0533] When an overlapping beam region is included between each beam Bq, the signal transmitted from the transmission antenna set included in the overlapping beam region is multiplexed and transmitted with a non-uniform code multiplexing number between Doppler multiplexed signals. The code multiplexing number may be greater than 1 and N CM A number in the range below -1.

[0534] In addition, by making the setting of the coding Doppler phase rotation amount by the phase rotation amount setting unit 105 satisfy conditions 2-a and 2-b in addition to conditions 1-a and 1-b, the Doppler detection range that can be detected by the radar device 10 can be expanded to the same range as that when a single transmitting antenna is used (for example, a range of ±1 / (2Tr)). In addition, even if conditions 1-a and 1-b are satisfied but conditions 2-a and 2-b are not satisfied, the Doppler detection range can be expanded to a range larger than the Doppler detection range of the equally spaced DDM (for example, a range of 1 / (2N)) as in the above-mentioned embodiment. t Tr)≦fd<1 / (2N t Tr))Larger range.

[0535] An operation example of the radar device 10 will be described below.

[0536] <Action Example 1>

[0537] In Operation Example 1, the number of multi-beams NB=3, and no overlapping beam region is included between the beam directions Bq.

[0538] For example, Fig. 20 The following is an example of the beam pattern of the transmitting antenna with beam directions B1, B2, and B3 when the number of multi-beams NB = 3. Fig. 20As shown, when the beam patterns of the transmission antennas in the respective beam directions have no overlapping portions (or when the overlapping portions are small), conditions 1-a and 2-a can be applied.

[0539] For example, in Fig. 20 In the case where the target object direction is any one of the beam direction B1, the beam direction B2, and the beam direction B3, the allocation of the Doppler multiplexed signal by the Doppler shift setting unit 106 may satisfy the condition 1-a. Thus, the radar device 10 can distinguish in the coded Doppler multiplexing demultiplexing unit 212 whether the reception level of the received signal corresponding to the transmission antenna of the beam direction B1 is reduced, the reception level of the received signal corresponding to the transmission antenna of the beam direction B2 is reduced, and the reception level of the received signal corresponding to the transmission antenna of the beam direction B3 is reduced.

[0540] In addition, when the result of this determination is that the received signal is a received signal corresponding to the transmission antenna of the beam direction B1 (or B2, B3), since the allocation of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 satisfies the condition 2-a, the coded Doppler multiplexed signal for the transmission antenna of the beam direction B1 (or B2, B3) can be demultiplexed using the operation of the existing coded Doppler multiplexed signal demultiplexing unit. By the operation of the coded Doppler multiplex demultiplexing unit 212, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output in which the transmission antenna is associated with each coded Doppler multiplexed signal.

[0541] <Action Example 2>

[0542] In Operation Example 2, the number of multi-beams NB=3, and an overlapping beam region is included between each beam direction Bq.

[0543] For example, Fig.21 The following is an example of the beam pattern of the transmitting antenna with beam directions B1, B2, and B3 when the number of multi-beams NB = 3. Fig.21 As shown, when the beam patterns of the transmitting antennas in each beam direction include overlapping portions (overlapping beam regions), conditions 1-a, 1-b, 2-a, and 2-b can be applied.

[0544] For example, in Fig.21 In the target direction, the transmission beam direction B1, B2 or B3 outside the overlapping beam range ( Fig.21In the case of the target object direction (1), (3) or (5) shown in FIG. 1 ), the allocation of the code-Doppler phase rotation amount by the phase rotation amount setting unit 105 may satisfy the condition 1-a. As a result, the radar device 10 can determine in the code-Doppler multiplexing and demultiplexing unit 212 whether the received signal corresponds to a transmitting antenna in one of the beam directions B1, B2 and B3.

[0545] In addition, for example, Fig.21 In the case where the direction of the target object is within the overlapping beam range ( Fig.21 In the case of the target direction (2) or (4) in the above example), the allocation of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 may satisfy the conditions 1-a and 1-b. Thus, the radar device 10 can not only determine in the coded Doppler multiplexing and demultiplexing unit 212 whether the received signal corresponds to a transmitting antenna in the beam directions B1, B2, and B3, but also determine whether the received signal is a received signal from the overlapping beam area of ​​the transmitting antennas in the beam directions B1 and B2 or a received signal from the overlapping beam area of ​​the transmitting antennas in the beam directions B2 and B3.

[0546] In addition, when the result of this determination is that the received signal is a received signal corresponding to the transmission antenna of the beam direction B1 (or B2, B3), since the allocation of the coded Doppler phase rotation amount by the phase rotation amount setting unit 105 satisfies the condition 2-a, the coded Doppler multiplexed signal for the transmission antenna of the beam direction B1 (or B2, B3) can be demultiplexed using the operation of the existing coded Doppler multiplexed signal demultiplexing unit. By the operation of the coded Doppler multiplex demultiplexing unit 212, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr), and can obtain an output in which the transmission antenna is associated with each coded Doppler multiplexed signal.

[0547] In addition, when it is determined that the received signal is a received signal from the overlapping beam area of ​​the transmitting antennas in the beam directions B1 and B2 (or the beam directions B2 and B3), since the allocation of the coded Doppler multiplexed signal in the phase rotation amount setting unit 105 satisfies the condition 2-b, the coded Doppler multiplexed signal for the transmitting antennas included in the overlapping beam area of ​​the transmitting antennas in the beam directions B1 and B2 (or the beam directions B2 and B3) can be demultiplexed using the operation of the existing coded Doppler multiplexed signal demultiplexing unit. By the operation of the coded Doppler multiplex demultiplexing 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 antennas are associated with each coded Doppler multiplexed signal.

[0548] The operation example of the radar device 10 has been described above.

[0549] Next, an example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 will be described.

[0550] Hereinafter, a setting example of the code Doppler phase rotation amount (case of NB=3) when condition 1 (for example, condition 1-a, condition 1-b) and condition 2 (condition 2-a, condition 2-b) are satisfied will be described.

[0551] Fig. 22 Indicates the number of transmitting antennas Nt = 6, N B1 =2, N B2 =2, N B2 An example of setting the code Doppler phase rotation amount in the phase rotation amount setting unit 105 when φ=3.

[0552] exist Fig. 22 In the figure, Tx#1 and Tx#2 are the transmitting antennas of beam direction B1, Tx#3 and Tx#4 are the transmitting antennas of beam direction B2, and Tx#5 and Tx#6 are the transmitting antennas of beam direction B3.

[0553] In addition, Fig. 22 In the Doppler multiplexing number N DM =5, the Doppler shift setting unit 106 can set five Doppler shift amounts DOP1 to DOP5 using, for example, the maximum equally spaced Doppler shift amount setting shown in equation (5). Fig. 22 The phase rotation amounts given to the Doppler frequency shift amounts DOP1 = 0, DOP2 = Δfd, DOP3 = 2Δfd, DOP4 = -2Δfd, and DOP5 = -Δfd are respectively (It can also be ), (It can also be ).like Fig. 22 As shown, the Doppler multiplexing interval Δfd is an equal interval, Δfd=1 / (10Tr).

[0554] In addition, Fig. 22 In the code multiplexing number N CM =2, 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.

[0555] exist Fig. 22 In the example, the number of transmitting antennas Nt = 6, the number of Doppler multiplexing N DM =5, code multiplexing number N CM =2, Nt <NDM× N CM Therefore, the phase rotation amount setting unit 105 can set the coded Doppler multiplexing number N for the Doppler multiplexed signal unevenly. DOP_CODE (ndm) (here, ndm = 1 to N DM ).

[0556] like Fig. 22 As shown, in the coding unit 107, the coding Doppler multiplexing numbers for the Doppler multiplexing signals using the five Doppler shift amounts DOP1 to DOP5 input from the Doppler shift setting unit 106 are set to N and N, respectively. 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, the phase rotation amount setting unit 105 sets the code-Doppler multiplexing number for the Doppler multiplexed signal unevenly.

[0557] In addition, Fig. 22 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#1 and Tx#2 in the beam direction B1. DM =5, among the Doppler multiplexed signals, the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1 and DOP2 (N DM_B1 =2). In addition, the coding unit 107 allocates Code2 and Code1 to the Doppler multiplexed signal using the Doppler frequency shift amounts DOP1 and DOP2 allocated 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 coding Doppler phase rotation amount ψ for the transmitting antennas Tx#1 and Tx#2 in the beam direction B1, respectively. 2，1 (m), ψ 1，2 (m).

[0558] In addition, Fig. 22 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#3 and Tx#4 in the beam direction B2. DM =5, among the Doppler multiplexed signals, the Doppler multiplexed signals using the Doppler frequency shift amounts DOP4 and DOP5 (N DM_B2 =2). In addition, the coding unit 107 allocates Code1 and Code1 to the Doppler multiplexed signals using the Doppler frequency shift amounts DOP4 and DOP5 allocated to the transmitting antennas Tx#3 and Tx#4 in the beam direction B2, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#3 and Tx#4 in the beam direction B2, respectively. 1，4 (m), ψ 1，5 (m).

[0559] In addition, Fig. 22 In the example, the Doppler shift setting unit 106 allocates the Doppler multiplexing number N to the transmission antennas Tx#5 and Tx#6 in the beam direction B3. DM =5 among the Doppler multiplexed signals using the Doppler frequency shift amounts DOP1 and DOP3 (N DM_B3 =2). In addition, the coding unit 107 allocates Code 1 and Code 2 to the Doppler multiplexed signal using the Doppler frequency shift amounts DOP1 and DOP3 allocated to the transmitting antennas Tx#5 and Tx#6 in the beam direction B2, respectively. For example, the phase rotation amount setting unit 105 sets the coding Doppler phase rotation amount ψ for the transmitting antennas Tx#5 and Tx#6 in the beam direction B3, respectively. 1，1 (5) ψ 2，3 (m).

[0560] exist Fig. 22 In the example, the Doppler multiplexing number assigned by the Doppler frequency shift setting unit 106 to the transmitting antennas of the beam directions B1, B2, and B3 is N. DM_B1 =N DM_B2 =N DM_B3 =2, are the same. Therefore, Fig. 22 The setting of the code Doppler phase rotation amount shown does not meet the different Doppler multiplexing pattern condition of condition 1A-a.

[0561] In addition, Fig. 22 In the figure, the code indices assigned to the transmitting antennas of the beam directions B1, B2, and B3 for each Doppler multiplexing signal using the Doppler multiplexing signals DOP1 to DOP5 are CodeIndex_B1 = (2, 1, *, *), CodeIndex_B2 = (*, *, 1, 1), and CodeIndex_B3 = (1, *, 2, *,). They are cyclically inconsistent and have different code index intervals, thus satisfying condition 1B-a (B-1).

[0562] In addition, Fig. 22 In the figure, for each Doppler multiplexing signal using Doppler multiplexing signals DOP1~DOP5, the code multiplexing numbers allocated to the transmitting antennas of the 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), which include cyclically consistent code multiplexing numbers. The code multiplexing numbers are the same, and therefore, condition 1B-a(B-2) is not satisfied.

[0563] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), an aliased Doppler frequency is observed in the Doppler analysis unit 210. At this time, the code indexes are CodeIndex_B1_alias=(1, 2, *, *), CodeIndex_B2_alias=(*, *, 2, 2), CodeIndex_B3_alias=(2, *, 1, *), which are different (circular inconsistency). Therefore, in Fig. 22 In the example, in the range of the target's Doppler frequency -1 / (2Tr)≦fdtarget<-1 / (2Tr), the code index is cyclically inconsistent and the code index intervals are different. Therefore, condition 1-a is satisfied, and the condition of different code multiplexing modes is met.

[0564] As mentioned above, Fig. 22 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 1-a.

[0565] In addition, Fig. 22 In the example, 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 are CodeIndex_B1&B2=(2, 1, *, 1, 1) and CodeIndex_B2&B3=(1, *, 2, 1, 1), respectively, for each Doppler multiplexed signal using Doppler multiplexed signals DOP1 to DOP5, which are cyclically inconsistent. In addition, even if CodeIndex_B1, CodeIndex_B2, and CodeIndex_B3 are also taken into account in addition to CodeIndex_B1&B2 and CodeIndex_B2&B3, the code index intervals between them are different (cyclically inconsistent), so condition 1-b is satisfied.

[0566] In addition, when the Doppler frequency of the target object is -1 / (2Tr)≦fdtarget<-1 / (4Tr) or 1 / (4Tr)≦fdtarget<1 / (2Tr), an aliased Doppler frequency is observed in the Doppler analysis unit 210. At this time, the code indexes are CodeIndex_B1&B2_alias=(1,2,*,2,2) and CodeIndex_B2&B3_alias=(2,*,1,2,2), which are different (circular inconsistency). Therefore, in Fig. 22In the example, in the range of the target's Doppler frequency -1 / (2Tr) ≦ fdtarget < -1 / (2Tr), even if CodeIndex_B1_alias, CodeIndex_B2_alias, and CodeIndex_B3_alias are taken into account, the code index cycles are inconsistent and the code index intervals are different. Therefore, condition 1-b is satisfied.

[0567] As mentioned above, Fig. 22 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 1-b.

[0568] In addition, Fig. 22 In the transmission antennas of the beam directions B1, B2, and B3, the code multiplexing numbers assigned to each Doppler multiplexing signal 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), and the Doppler multiplexing signals are multiplexed and transmitted with uneven code multiplexing numbers, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig. 22 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 2-a.

[0569] In addition, Fig. 22 In the overlapping beam areas of beam directions B1 and B2 and the overlapping beam areas of beam directions B2 and B3, the code multiplexing numbers assigned to each Doppler multiplexed signal in each transmitting antenna are N_Code_B1&B2=(1, 1, 0, 1, 1) and N_Code_B2&B3=(1, 0, 1, 1, 1), and the Doppler multiplexed signals are multiplexed and transmitted with uneven code multiplexing numbers, and the code multiplexing number is included in 1 or more and N CM -1 or less. Therefore, Fig. 22 The setting of the code Doppler phase rotation amount shown is a setting example that satisfies condition 2-b.

[0570] The following describes the transmission antenna unit 109 including Fig. 22 An example of a received signal in the output of the Doppler analysis unit 210 is described in which the Doppler frequency shift amount is set for transmitting antennas in different beam directions B1, B2 and B3, and the receiving antenna unit 202 is an omnidirectional antenna (or an antenna having a directional characteristic that is approximately uniform within the field of view covered by the two transmitting antennas in beam direction B1 and beam direction B2).

[0571] For example, in the direction of the object Fig.21In the case of the target object direction (1), (3) or (5) shown in the figure (for example, when the target object exists around the beam direction B1, B2 or B3), or in the case of the target object direction (2) or target object direction (4) (for example, when the target object exists around the overlapping beam area B2&B3 or B2&B3), the code intervals are different for the transmission antennas in each beam direction and the transmission antennas in each overlapping beam direction. Therefore, the radar device 10 can judge in the code-Doppler multiplexing and demultiplexing unit 212 that the reception level of the reception signal corresponding to the transmission antenna included in any one of the beam directions B1, B2, B3 and the overlapping beam areas B2&B3 or B2&B3 has decreased.

[0572] In addition, in the case where it is determined based on the determination result that the received signal is from a transmitting antenna in a beam direction Bq or an overlapping beam area (for example, B2&B3 or B2&B3), since the setting of the coded Doppler multiplexed signal for the transmitting antenna in the beam direction Bq or the overlapping beam area (B2&B3 or B2&B3) is known, the radar device 10 can demultiplex the multiplexed signal through the actions disclosed in patent documents 5, 6, etc., for example.

[0573] in addition, Fig. 22 In the example, the setting of the coded Doppler phase rotation amount performed by the phase rotation amount setting unit 105 satisfies conditions 2-a and 2-b. Therefore, the detectable Doppler frequency range fd depends on the direction of the target object and is in the range of -1 / (2Tr)≦fd<1 / (2Tr), which can be expanded to a Doppler detection range larger than the Doppler detection range of equally spaced Doppler multiplexing.

[0574] (Variant 2)

[0575] In the above-mentioned embodiments and modifications, Fig.10 , Fig. 20 and Fig.21 As shown in the figure, the case where the directions of the beams in the multi-beam are different from each other is described, but the setting of the multi-beam (for example, the beam direction and the beam width) is not limited to the above example. For example, at least one of the beam direction and the beam width of each beam constituting the multi-beam may be different. In addition, the number of multi-beams NB≧2 may be.

[0576] Next, a multi-beam setting example is described.

[0577] <Multi-beam setting example 1>

[0578] In setting example 1, for example, it can be as follows Fig.23As shown, in the multi-beam (e.g., beam directions B1, B2, B3), the beam directions are different from each other and the beam widths are different. It may be that in the multi-beam (e.g., beam directions B1, B2, B3), the beam directions in the horizontal direction (or horizontal plane) are different from each other and the beam widths in the horizontal direction (or horizontal plane) are different. It may also be that the beam directions in the vertical direction (or vertical plane) are different from each other and the beam widths in the vertical direction (or vertical plane) are different.

[0579] <Multi-beam setting example 2>

[0580] In the above embodiment, Fig.10 As shown, an example in which the beam directions are different in the horizontal direction (or horizontal plane) is described, but the present invention is not limited to this.

[0581] In setting example 2, for example, the beam directions may be different in the vertical direction (or vertical plane).

[0582] For example, it could be, Fig.24 As shown in (a), in the multi-beam (for example, beam directions B1 and B2), the beam directions are substantially the same in the horizontal direction (or horizontal plane), and are different in the vertical direction (or vertical plane).

[0583] In addition, for example, it can also be Fig.24 As shown in (b), in the multi-beam (for example, beam directions B1, B2, B3), the beam directions are different in both the horizontal direction (or horizontal plane) and the vertical direction (or vertical plane).

[0584] <Multi-beam setting example 3>

[0585] In setting example 3, for example, it can be as follows Fig.25 As shown, in the multi-beam (for example, beam directions B1 and B2), the beam directions are substantially the same but the beam widths are different. Alternatively, in the multi-beam (for example, beam directions B1 and B2), the beam directions in the horizontal direction (or horizontal plane) are substantially the same but the beam widths in the horizontal direction (or horizontal plane) are different. Alternatively, in the multi-beam (for example, beam directions B1 and B2), the beam directions in the vertical direction (or vertical plane) are substantially the same but the beam widths in the vertical direction (or vertical plane) are different.

[0586] In setting example 3, for example, in the description of the above embodiment, "transmitting antennas with different beam directions" are replaced with "transmitting antennas with different beam widths" (hereinafter referred to as "different beams"), thereby enabling the same application as the above embodiment.

[0587] Hereinafter, as an example, an operation example of the radar device 10 in the case where the beam directions are the same but the beam widths are different is described using setting example 1 of the code Doppler phase rotation amount. In addition, the setting of the code Doppler phase rotation amount is not limited to setting example 1, and the same operation can be performed even when other setting examples of the code Doppler phase rotation amount are used, and the same effect as the above-mentioned embodiment can be obtained.

[0588] For example, when 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 coding Doppler phase rotation amount in the phase rotation amount setting unit 105 is applied. In addition, for example, Tx#1 and Tx#2 are Fig.25 The transmit antennas of beam width B1 (eg, beam B1) shown, Tx#3 and Tx#4 are Fig.25 The transmit antenna has a beam width B2 (eg, beam B2) as shown. Fig.25 , an example of a case where the beam width of beam B1 is wider than the beam width of beam B2 is shown. Here, the beam widths of beams B1 and B2 may be in the horizontal direction (or horizontal plane), 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.

[0589] In the radar device 10 , the receiving antenna may be an omnidirectional antenna (or an antenna having a directional characteristic that is substantially uniform within the field of view covered by the transmitting antennas of both the beam B1 and the beam B2 ).

[0590] For example, when the object position is Fig.25In the case of the target object position (1) or the target object position (3) shown, the target object position is within the beam width of beam B1 and within the field of view, 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, since the target object position (1) and the target object position (3) are outside the beam width of beam B2 and outside the field of view, the radiation direction of the radar transmission wave transmitted from Tx#3 and Tx#4 of beam B2 does not coincide with the direction of the target object position (1) and (3), and the target object position (1) and the target object position (3) are equivalent to the zero azimuth of the transmission 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 level of the reception signal corresponding to Tx#3 and Tx#4 is greatly different from the reception level of the reception signal corresponding to Tx#1 and Tx#2, and may be 10 dB or more lower depending on the beam directivity characteristics of the zero azimuth of Tx#3 and Tx#4. In this case, the reception signal received by the radar device 10 becomes Fig. 9 The received signal shown in (a).

[0591] In addition, for example, at the object position such as Fig.25 When the target position (4) is in an area where the field of view of beams B1 and B2 overlap (for example, when the target position is close to the target), radar device 10 receives reflected waves corresponding to radar transmission waves transmitted from Tx#1 and Tx#2 of beam B1 and reflected waves corresponding to radar transmission waves transmitted from Tx#3 and Tx#4 of beam B2. In this case, the received signal received by radar device 10 may be, for example, Fig. 9 In addition, for example, when the directional gain of beam B2 is higher than that of beam B1 by about 10 dB, the received signal received by radar device 10 may be, for example, Fig. 9 The received signal is as shown in (c).

[0592] In addition, for example, at the object position such as Fig.25When the target object position (2) is located within the field of view of beam B2 and outside the field of view of beam B1 (for example, when located at a long distance), the reception level of the reflected wave corresponding to the radar transmission wave sent 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 the directional gain of beam B2, the reception level of the reflected wave corresponding to the radar transmission wave sent from Tx#1 and Tx#2 of beam B1 is lower than the reception level of the received signal corresponding to Tx#3 and Tx#4. For example, the reception level of the received signal corresponding to Tx#1 and Tx#2 is greatly different from the reception level of the received signal corresponding to Tx#3 and Tx#4, and depends on the beam directivity characteristics of Tx#1 and Tx#2, and may be, for example, 10 dB or more lower. In such a case, the received signal received by radar device 10 becomes Fig. 9 The received signal shown in (c).

[0593] For example, Fig. 9 As shown in (b), when the radar device 10 receives the reception signals corresponding to the transmission antennas of each beam at substantially the same reception level, the signals transmitted from the Nt transmission antennas including the transmission antennas of the beams B1 and B2 are coded Doppler multiplexed and transmitted by unequally setting the coded Doppler multiplexing number for the Doppler multiplexed signal. Therefore, the radar device 10 can demultiplex the coded Doppler multiplexed signal based on the existing demultiplexing operation of the coded Doppler multiplexed signal.

[0594] In addition, if Fig. 9 (a) and Fig. 9 As shown in (c), when receiving the reflected wave from one of the beam B1 and the beam B2 (when the reception levels are greatly different), the radar device 10 receives different coded Doppler multiplexed signals (for example, Doppler multiplexed signals that satisfy condition 1) depending on the position of the target object. Therefore, the radar device 10 can determine in the coded Doppler multiplex demultiplexing unit 212 whether the reception level of the reception signal corresponding to the transmission antenna of the beam B1 has decreased or the reception level of the reception signal corresponding to the transmission antenna of the beam B2 has decreased.

[0595] For example, the coded Doppler multiplexed signal transmitted from the transmission antenna of the beam B1 (or beam B2) is coded Doppler multiplexed and transmitted by setting the coded Doppler multiplex number for the Doppler multiplexed signal unevenly. Therefore, for example, when the coded Doppler multiplexed demultiplexing unit 212 determines that the received signal is a received signal corresponding to the transmission antenna of the beam B1 (or beam B2), the radar device 10 can demultiplex the coded Doppler multiplexed signal based on the existing demultiplexing operation of the coded Doppler multiplexed signal.

[0596] By operating the code Doppler multiplexing and demultiplexing unit 212 in this manner, the radar device 10 can determine the Doppler frequency fd of the target object in the range of -1 / (2Tr)≦fd<1 / (2Tr) and obtain an output in which the transmission antenna is associated with each code Doppler multiplexed signal.

[0597] In the above, each embodiment of the present disclosure has been described.

[0598] [Other embodiments]

[0599] (1) In addition, in a radar device according to an embodiment of the present disclosure, the radar transmitter and the radar receiver may be respectively arranged at physically separate locations. In addition, in a radar receiver according to an embodiment of the present disclosure, the direction estimation unit and other components may also be independently arranged at physically separate locations.

[0600] (2) In addition, the number of transmitting antennas Nt, the number of receiving antennas Na, and the number of Doppler multiplexing N used in one embodiment of the present disclosure are DM , the number of beams of multi-beam NB, the number of transmitting antennas in each beam direction N Bq , Doppler frequency shift, Doppler frequency shift interval, code multiplexing number N CM , code interval (code index (Code Index)) and other parameters are examples, and are not limited to these values. In addition, for example, a part of the transmitting antennas of the radar device can be used as the number of transmitting antennas Nt, and a part of the receiving antennas of the radar device can be used as the number of receiving antennas Na.

[0601] (3) The configuration example of the MIMO antenna used in one embodiment of the present disclosure (e.g., configuration example A, configuration example B) is described as a case where a radar transmission signal is transmitted from a plurality of transmission antennas using coded Doppler multiplexing transmission, but the present invention is not limited thereto. For example, the present invention can also be applied to a case where a radar transmission signal is transmitted from a plurality of transmission antennas using time division multiplexing transmission or code multiplexing transmission, and the effect brought about by the configuration of the disclosed MIMO antenna can be obtained.

[0602] (4) In the above embodiment, in a multi-beam transmission MIMO radar using coded Doppler multiplexing transmission, in order to expand the detectable Doppler frequency range for Nt transmission antennas with different directivities to the range of ±1 / (2Tr), it is assumed that the code multiplexing number between Doppler multiplexing signals is set unevenly and coded Doppler multiplexing transmission is performed from multiple transmission antennas. In the above embodiment, a method for improving the detection performance of the multi-beam transmission MIMO radar by applying coded Doppler multiplexing transmission that satisfies conditions 1 and 2 is further described. For example, when the moving speed of the assumed target object is a relatively low speed, or when the relative speed between the radar device and the target object is limited to a relatively small range, the above premise may not be applied.

[0603] For example, the coding unit 107 may use an evenly spaced Doppler frequency shift setting with a smaller interval than the maximum evenly spaced Doppler frequency shift setting interval to set the coded Doppler multiplexing number N to DOP_CODE (1), N DOP_CODE (2), ..., N DOP_CODE (N DM ) is set to be included in 1 or more and N CM For example, the coding unit 107 may set the code number N to be the same in all settings of the code Doppler multiplexing number. CM Therefore, it can be that the Doppler frequency shift DOP ndm In multiple combinations of orthogonal code sequences, the Doppler frequency shift DOP ndm The orthogonal code sequences corresponding to each other are based on the multiplexing number (coded Doppler multiplexing number) N of these orthogonal code sequences. DOP_CODE (ndm) are the same. For example, the coding unit 107 can uniformly set the coded Doppler multiplexing number for the Doppler multiplexed signal. By setting it in this way, the Doppler multiplexed signal is non-uniformly spaced Doppler multiplexed, so the radar device 10 can demultiplex the signals sent by coded Doppler multiplexing from multiple transmitting antennas into separate signals and receive them over the Doppler range of ±1 / (2×Loc×Tr). By applying such a setting of coded Doppler multiplexing transmission, and then applying coded Doppler multiplexing transmission that satisfies condition 1, it is possible to improve the detection performance of the multi-beam transmission MIMO radar.

[0604] Alternatively, the coding unit 107 may use the maximum equally spaced Doppler frequency shift setting to set the coding Doppler multiplexing number N DOP_CODE (1), N DOP_CODE (2), ..., N DOP_CODE (N DM ) is set to be included in 1 or more and N CMFor example, the coding unit 107 may set the code number N to be the same in all settings of the code Doppler multiplexing number. CM In this case, the Doppler frequency shift DOP ndm The number of combinations of orthogonal code sequences and the number of transmitting antennas Nt may be the same (for example, N DM ×N CM =Nt). For example, the coding unit 107 may uniformly set the coded Doppler multiplexing number for the Doppler multiplexed signal. When this setting is adopted, the aliasing determination process in the reception process of the radar device 10 is not applied. In addition, the radar device 10 may, for example, cover ±1 / (2Loc×N DM ×Tr), the signals transmitted by coded Doppler multiplexing from multiple transmitting antennas are demultiplexed into separate signals and received. By applying such coded Doppler multiplexing transmission settings, and then applying coded Doppler multiplexing transmission that satisfies condition 1, the detection performance of multi-beam transmission MIMO radar can be improved.

[0605] (5) In one embodiment of the present disclosure, instead of using all Nt transmission antennas included in the radar device 10 , only a part of them may be used to perform code multiplexing transmission in one embodiment of the present disclosure.

[0606] In addition, when not using all Nt transmitting antennas of the radar device 10 but only using a part to apply code multiplexing transmission, the radar device 10 may also set (or change) at least one of the combination of transmitting antennas and the number of multiplexed transmissions for code Doppler multiplexing transmission to time division and transmit. In this case, for example, the radar device 10 may time-division switch the combination of transmitting antennas for each transmission cycle or each code transmission cycle (for example, a cycle corresponding to the code length of the code sequence). Or, for example, the radar device 10 may switch the combination of transmitting antennas or the number of transmitting antennas for multiplexing for each measurement cycle (every Nc radar transmission signal transmissions). Even if such an action is applied, the same effect as the above-mentioned embodiment can be obtained.

[0607] In addition, when code multiplexing transmission is applied by using only a part of the Nt transmission antennas provided by the radar device 10 instead of using all of them, the radar device 10 may set (e.g., change) the combination of transmission antennas used for code Doppler multiplexing transmission in a time division manner and use different chirp signals for transmission. For example, the radar device 10 may change at least one of the transmission frequency band, frequency scanning time, and center frequency of the chirp signal, or may combine a plurality of these parameters and use different chirp signals for transmission.

[0608] (6) Although not shown in the figure, a radar device according to an embodiment of the present disclosure has, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, and an operating memory such as a RAM (Random Access Memory). In this case, the functions of the above-mentioned parts are realized by the CPU executing the control program. However, the hardware structure of the radar device is not limited to this example. For example, each functional part of the radar device may also be realized as an integrated circuit, i.e., an IC (Integrated Circuit). Each functional part may be independently integrated on a single chip, or may be integrated on a single chip in a manner that includes part or all of it.

[0609] Various embodiments have been described above with reference to the accompanying drawings, but the present disclosure is of course not limited to these examples. As long as one is skilled in the art, it is obvious that various variations or modifications can be thought of within the scope described in the claims, and it should be understood that these variations or modifications also belong to the technical scope of the present disclosure. In addition, the constituent elements of the above-mentioned embodiments can be arbitrarily combined within the scope of the disclosure purpose.

[0610] In addition, the expression "part" in the above-mentioned embodiments can also be replaced by other expressions such as "...circuitry", "...component (assembly)", "device (device)", "unit (unit)" or "module (module)".

[0611] In the above-mentioned embodiments, an example in which the present disclosure is configured using hardware has been described. However, the present disclosure may also be implemented by software in cooperation with hardware.

[0612] In addition, each functional block used in the description of the above-mentioned embodiments is typically implemented as an integrated circuit, i.e., LSI (Large Scale Integration). The integrated circuit can also control each functional block used in the description of the above-mentioned embodiments, and includes input terminals and output terminals. These functional blocks can be independently monolithic, or can be monolithic in a manner that includes a part or all. It is referred to as "LSI" here, but it can also be referred to as "IC", "system LSI (system LSI)", "super LSI (super LSI)", "ultra-large LSI (ulira LSI)" depending on the degree of integration.

[0613] In addition, the method of integrated circuitization is not limited to LSI, and it can also be realized using a dedicated circuit or a general-purpose processor. It is also possible to use an FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connection or setting of the circuit blocks inside the LSI.

[0614] Furthermore, if integrated circuit technology that replaces LSI emerges as semiconductor technology advances or other derived technologies emerge, it is of course possible to use this technology to integrate functional blocks. There is also the possibility of applying biotechnology, etc.

[0615] <Summary of the present disclosure>

[0616] 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, transmitting signals to which phase rotation amounts corresponding to combinations of Doppler frequency shift amounts and code sequences are assigned, wherein a different combination of at least one of the Doppler frequency shift amounts and the code sequences corresponds to each of the plurality of transmitting antennas, and a first pattern of the Doppler frequency shift amounts and the code sequences assigned to the first transmitting antenna is different from a second pattern of the Doppler frequency shift amounts and the code sequences assigned to the second transmitting antenna.

[0617] In one embodiment of the present disclosure, the number of the plurality of transmitting antennas is less than the total number of the combinations.

[0618] In one embodiment of the present disclosure, the first mode and the second mode are related to the interval of Doppler frequency shift amount, the Doppler multiplexing number based on the first transmitting antenna is the same as the Doppler multiplexing number based on the second transmitting antenna, and at least one of the intervals of Doppler frequency shift amount based on the first transmitting antenna is different from the intervals of Doppler frequency shift amount based on the second transmitting antenna.

[0619] In one embodiment of the present disclosure, the first mode and the second mode are related to a Doppler multiplexing number, and a Doppler multiplexing number based on the first transmitting antenna is different from a Doppler multiplexing number based on the second transmitting antenna.

[0620] In one embodiment of the present disclosure, the first mode and the second mode are related to the order of the intervals of the Doppler frequency shift amounts, a plurality of first Doppler frequency shift intervals based on the first transmitting antenna and a plurality of second Doppler frequency shift intervals based on the second transmitting antenna are the same, and the order of the plurality of first Doppler frequency shift intervals on the Doppler frequency axis is different from the order of the plurality of second Doppler frequency shift intervals on the Doppler frequency axis.

[0621] In one embodiment of the present disclosure, the first mode and the second mode are related to the code sequence, and in the plurality of combinations, the index of the code sequence corresponding to each of the Doppler frequency shift amounts corresponding to the first transmitting antenna is different from the index of the code sequence corresponding to each of the Doppler frequency shift amounts corresponding to the second transmitting antenna.

[0622] In one embodiment of the present disclosure, the first mode and the second mode are related to a code multiplexing number based on the code sequence, and in the plurality of combinations, the code multiplexing number of the code sequence corresponding to each of the Doppler frequency shift amounts corresponding to the first transmitting antenna is different from the code multiplexing number of the code sequence corresponding to each of the Doppler frequency shift amounts corresponding to the second transmitting antenna.

[0623] In one embodiment of the present disclosure, in multiple combinations, with respect to at least one of the first transmitting antenna and the second transmitting antenna, at least one Doppler frequency shift amount is such that a code multiplexing number based on the code sequence corresponding to the Doppler frequency shift amount is different from a code multiplexing number based on the code sequence corresponding to other Doppler frequency shift amounts.

[0624] In one embodiment of the present disclosure, the device further comprises: a plurality of receiving antennas for receiving reflected wave signals generated by the transmission signal reflected from a target; and a receiving circuit for estimating the direction of the target using the reflected wave signals.

[0625] In one embodiment of the present disclosure, there are also multiple receiving antennas arranged at a first interval in a first direction, the first transmitting antenna is arranged at the first interval in the first direction, and is arranged at a different position in a second direction orthogonal to the first direction, the second transmitting antenna is arranged at the first interval in the first direction, and is arranged at a different position in the second direction orthogonal to the first direction, and in the first direction, the first transmitting antenna and the second transmitting antenna are arranged at a spacing larger than the aperture length of the multiple receiving antennas.

[0626] In one embodiment of the present disclosure, there are also multiple receiving antennas arranged at a first interval in a first direction, the first transmitting antenna is arranged at the second interval in the first direction, and is arranged at a different position in a second direction orthogonal to the first direction, the second transmitting antenna is arranged at the second interval in the first direction, and is arranged at a different position in the second direction orthogonal to the first direction, in the first direction, the first transmitting antenna and the second transmitting antenna are arranged at a spacing larger than the aperture length of the multiple receiving antennas, and the difference between the first spacing and the second spacing is a specified value based on the wavelength of the transmission signal.

[0627] In one embodiment of the present disclosure, the prescribed value is a value within a range of 0.45 times to 0.8 times the wavelength.

[0628] In one embodiment of the present disclosure, at least one of a beam direction and a beam width of the first beam and the second beam is different.

[0629] In one embodiment of the present disclosure, a combination of transmitting antennas among the plurality of transmitting antennas used for multiplexed transmission of the transmitting signal is switched according to each transmitting period of the transmitting signal, each period corresponding to the code length of the code sequence, or each measurement period in the radar device.

[0630] The disclosure contents of the specification, drawings and abstract contained in the Japanese patent application No. 2022-191347 filed on November 30, 2022 are all cited in this application.

[0631] Industrial Applicability

[0632] The present disclosure is suitable as a radar device that detects a wide-angle range.

[0633] Description of Reference Numerals

[0634] 10 Radar device

[0635] 100 Radar Transmitter

[0636] 101 Radar transmission signal generating unit

[0637] 102 transmission signal generation control unit

[0638] 103 Modulation signal generation unit

[0639] 104 VCO

[0640] 105 Phase rotation amount setting unit

[0641] 106 Doppler frequency shift setting unit

[0642] 107 Coding Department

[0643] 108 Phase rotation unit

[0644] 109 Transmitting antenna unit

[0645] 200 Radar receiving unit

[0646] 201 Antenna System Processing Department

[0647] 202 Receiving antenna unit

[0648] 203 Receiving wireless unit

[0649] 204 Mixer Department

[0650] 205 LPF

[0651] 206 Signal Processing Department

[0652] 207 AD conversion unit

[0653] 208 Beat Frequency Analysis Department

[0654] 209 Output switching unit

[0655] 210 Doppler Analysis Department

[0656] 211 CFAR Department

[0657] 212 Coded Doppler multiplexing and demultiplexing unit

[0658] 213 Direction Estimation Unit

Claims

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

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

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

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

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

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

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

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

9. The radar device according to claim 1, wherein: Also available: A plurality of receiving antennas for receiving reflected wave signals generated by the transmitted signal reflected from a target; and The receiving circuit uses the reflected wave signal to estimate the direction of the target.

10. The radar device according to claim 1, wherein: It also includes a plurality of receiving antennas arranged at a first interval in a first direction, The antennas included in the first transmitting antenna are arranged at the first interval in the first direction and at different positions in a second direction orthogonal to the first direction. The antennas included in the second transmitting antenna are 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 transmitting antenna and the second transmitting antenna are arranged at a distance greater than an aperture length of the plurality of receiving antennas.

11. The radar device according to claim 1, wherein: It also includes a plurality of receiving antennas arranged at a first interval in a first direction, The antennas included in the first transmitting antenna are arranged at a second interval in the first direction and at different positions in a second direction orthogonal to the first direction. The antennas included in the second transmitting antenna are 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 a distance greater than the aperture length of the plurality of receiving antennas. The difference between the first interval and the second interval is a prescribed value based on the wavelength of the transmission signal.

12. The radar device according to claim 11, wherein: The prescribed value is a value within a range of 0.45 to 0.8 times the wavelength.

13. The radar device according to claim 1, wherein: The first beam and the second beam are different in at least one of a beam direction and a beam width.

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

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

16. The method for transmitting a radar signal according to claim 15, wherein: The number of the plurality of transmitting antennas is less than the total number of the combinations.

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

18. The method for transmitting a radar signal according to claim 15, wherein: The first mode and the second mode are related to the Doppler multiplexing number. A Doppler multiplexing number of the radar signal transmitted by the first transmitting antenna is different from a Doppler multiplexing number of the radar signal transmitted by the second transmitting antenna.

19. The method for transmitting a radar signal according to claim 15, wherein: The first mode and the second mode are related to the order of the intervals of the Doppler frequency shift amounts. A plurality of first Doppler frequency shift intervals between the Doppler frequency shift amounts corresponding to the first transmitting antenna and a plurality of second Doppler frequency shift intervals between the Doppler frequency shift amounts corresponding to the second transmitting antenna are the same, An order of the plurality of first Doppler frequency shift intervals on a Doppler frequency axis is different from an order of the plurality of second Doppler frequency shift intervals on the Doppler frequency axis.

20. A method for receiving a radar signal, characterized in that: The following steps are involved: receiving, from a plurality of receiving antennas, reflected wave signals of the radar signal transmitted by the radar signal transmitting method according to claim 15 and reflected from the target; as well as The direction of the target is estimated using the reflected wave signal.

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