Radar device

Abstract

The radar receiving unit includes: a plurality of transmission antennas for transmitting transmission signals; and a radar transmitting unit for adding Doppler frequency shift amounts to the transmission signals transmitted from the plurality of transmission antennas. Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be the object of Doppler analysis into unequal intervals.

Description

Technical Field

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

[0002] In recent years, research has been progressing on radar devices that use short-wavelength radars including microwaves or millimeter waves that can achieve high resolution to transmit signals. In addition, in order to improve safety when outdoors, it is required to develop radar devices (wide-angle radar devices) that can detect small objects such as pedestrians or fallen objects in addition to vehicles within a wide angle range.

[0003] As a structure of a radar device having a wide-angle detection range, there is a structure using the following method (arrival angle estimation method. Direction of Arrival (DOA) estimation), which receives reflected waves through an array antenna composed of multiple antennas (antenna elements), and estimates the arrival angle (arrival direction) of the reflected waves through a signal processing algorithm based on the reception phase difference for the element spacing (antenna spacing). For example, as an arrival angle estimation method, the Fourier method can be cited, or, as a method that can obtain high resolution, the Capon method, MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques, signal parameter estimation based on rotational invariance techniques) can be cited.

[0004] In addition, as a radar device, for example, the following structure has been proposed (sometimes also called "MIMO (Multiple Input Multiple Output) radar"): in addition to the receiving side, the transmitting side 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).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2008-304417

[0008] Patent Document 2: Japanese Patent Application No. 2011-526371

[0009] Patent Document 3: Japanese Patent Application Publication No. 2014-119344

[0010] Non-patent literature

[0011] 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

[0012] Non-patent document 2: M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823

[0013] 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

[0014] However, methods for detecting targets (or objects) in radar devices (eg, MIMO radars) have not been fully studied.

[0015] Non-limiting embodiments of the present disclosure contribute to providing a radar device capable of detecting a target object with good accuracy.

[0016] A radar device according to one embodiment of the present disclosure includes: a plurality of transmitting antennas for transmitting transmission signals; and a circuit for adding Doppler frequency shift amounts to the transmission signals transmitted from the plurality of transmitting antennas, wherein each interval of the Doppler frequency shift amounts is set to an interval obtained by dividing a Doppler frequency range that is the object of Doppler analysis into unequal intervals.

[0017] In addition, these broad or specific embodiments may be implemented by a system, an apparatus, a method, an integrated circuit, a computer program or a recording medium, or may be implemented by any combination of systems, apparatuses, methods, integrated circuits, computer programs and recording media.

[0018] According to one embodiment of the present disclosure, a radar device can detect a target object with high accuracy.

[0019] 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

[0020] Figure 1 This is a block diagram showing a configuration example of a radar device according to Embodiment 1.

[0021] Figure 2 This is a diagram showing an example of a transmission signal and a reflected wave signal when a chirp pulse is used.

[0022] Figure 3 This is a diagram showing an example of a Doppler peak.

[0023] Figure 4 This is a diagram showing an example of a Doppler peak in the first embodiment.

[0024] Figure 5 This is a diagram showing an example of the Doppler peak of deformation 1.

[0025] Figure 6 This is a diagram showing an example of the Doppler peak of the modification 2.

[0026] Figure 7 This is a block diagram showing a configuration example of a radar transmitting unit according to variation 4.

[0027] Figure 8 This is a block diagram showing a configuration example of a radar device according to variation 5.

[0028] Fig. 9 This is a block diagram showing a configuration example of a radar device according to the second embodiment.

[0029] Fig.10 This is a block diagram showing another configuration example of the radar transmitting unit of embodiment 2.

[0030] Fig.11 This is a block diagram showing a configuration example of a radar device according to a third embodiment.

[0031] Fig.12 This is a diagram showing an example of the Doppler peak of deformation 7.

[0032] Fig.13 This is a diagram showing an example of Doppler multiplexing and separation processing according to variation 7.

[0033] Fig.14 This is a diagram showing an example of the Doppler peak of the deformation 8.

[0034] Fig.15This is a diagram showing an example of Doppler multiplexing and separation processing according to variation 8. DETAILED DESCRIPTION

[0035] For example, MIMO radar transmits multiplexed signals (radar transmission waves) using time division, frequency division or code division from multiple transmission antennas (or "transmission array antennas"), receives signals (radar reflection waves) reflected by surrounding objects using multiple reception antennas (or "reception array antennas"), and receives the multiplexed transmission signals separately from each reception signal. Through this processing, MIMO radar can obtain a propagation path response represented by the product of the number of transmission antennas and the number of reception antennas, and perform array signal processing on these reception signals as a virtual reception array.

[0036] In addition, in MIMO radar, by appropriately configuring the element spacing in the transmitting and receiving array antenna, the antenna aperture can be virtually expanded and the angular resolution can be improved.

[0037] For example, Patent Document 1 discloses the following MIMO radar (hereinafter referred to as "time division multiplexing MIMO radar"), which uses time division multiplexing transmission in which signals are transmitted at staggered transmission times according to the transmitting antennas as the multiplexing transmission method of the MIMO radar. Compared with frequency multiplexing transmission or code multiplexing transmission, time division multiplexing transmission can be implemented with a simple structure. In addition, by sufficiently expanding the interval between transmission times, time division multiplexing transmission can well maintain the orthogonality between transmission signals. The time division multiplexing MIMO radar outputs a transmission pulse as an example of a transmission signal while switching the transmitting antennas in sequence at a prescribed period. The time division multiplexing MIMO radar uses multiple receiving antennas to receive signals obtained by reflection of the transmission pulse by an object, and after correlation processing between the received signal and the transmission pulse, for example, spatial FFT (Fast Fourier Transform) processing (arrival direction estimation processing of the reflected wave) is performed.

[0038] The time-division multiplexing MIMO radar sequentially switches the transmitting antennas used to transmit the transmission signal (e.g., transmission pulses or radar transmission waves) at a predetermined period. Therefore, the time required for time-division multiplexing transmission until the transmission signal is transmitted from all the transmission antennas will become longer than that of frequency-division transmission or code-division transmission. Therefore, for example, in the case where the transmission signal is transmitted from each transmission antenna as in Patent Document 2, and the Doppler frequency (i.e., the relative speed of the target) is detected based on the received phase change of these transmission signals, when Fourier frequency analysis is applied to detect the Doppler frequency, the time interval (e.g., sampling interval) for observing the received phase change will be long. The Doppler frequency range (i.e., the relative speed range of the target that can be detected) that can detect the Doppler frequency without aliasing is thereby reduced.

[0039] Furthermore, in the case of a reflected wave signal from a target exceeding the Doppler frequency range (in other words, the relative speed range) in which the Doppler frequency can be detected without aliasing, the radar device cannot determine whether the reflected wave signal is an aliasing component, resulting in ambiguity (uncertainty) in the Doppler frequency (in other words, the relative speed of the target).

[0040] For example, when the radar device transmits a transmission signal (transmission pulse) while switching Nt transmission antennas in sequence at a predetermined period Tr, it takes Tr×Nt transmission time until all transmission antennas have transmitted the transmission signal. c Next, Fourier frequency analysis is applied to detect the Doppler frequency. According to the sampling theorem, the Doppler frequency range that can detect the Doppler frequency without aliasing is ±1 / (2Tr×Nt). Therefore, the larger the number of transmitting antennas Nt, the smaller the Doppler frequency range that can detect the Doppler frequency without aliasing. Even at a lower relative speed, ambiguity in the Doppler frequency is still likely to occur.

[0041] Since the time-division multiplexing MIMO radar may have the ambiguity of the Doppler frequency as described above, the following focuses on a method of multiplexing and transmitting transmission signals from a plurality of transmission antennas at the same time as an example.

[0042] As a method of multiplexing and transmitting transmission signals simultaneously from multiple transmission antennas, there is, for example, a method of transmitting signals in a manner that allows the receiving side to separate multiple transmission signals on the Doppler frequency axis (hereinafter referred to as "Doppler multiplexing transmission") (for example, refer to non-patent document 3).

[0043] In Doppler multiplexing transmission, the transmitting side adds a Doppler frequency shift larger than the Doppler frequency bandwidth of the received signal to the transmission signal transmitted from the transmission antenna different from the reference transmission antenna, for example, relative to the transmission signal transmitted from the reference transmission antenna, and transmits the transmission signals from multiple transmission antennas simultaneously. In Doppler multiplexing transmission, the receiving side receives the transmission signals transmitted from each transmission antenna separately by filtering on the Doppler frequency axis.

[0044] In Doppler multiplexing transmission, by simultaneously transmitting transmission signals from multiple transmission antennas, the time interval for observing the reception phase change when applying Fourier frequency analysis to detect the Doppler frequency (or relative speed) can be shortened compared to time division multiplexing transmission. However, in Doppler multiplexing transmission, since the transmission signals of each transmission antenna are separated by filtering on the Doppler frequency axis, the effective Doppler frequency bandwidth of each transmission signal is limited.

[0045] For example, the following case is described, that is, in Doppler multiplexing transmission, the radar device transmits transmission signals from Nt transmission antennas at a period Tr. c Next, Fourier frequency analysis is applied to detect the Doppler frequency (or relative speed). According to the sampling theorem, the Doppler frequency range that can detect the Doppler frequency without aliasing is ±1 / (2×Tr). That is, compared with the case of time division multiplexing transmission (for example, ±1 / (2Tr×Nt)), the Doppler frequency range that can detect the Doppler frequency without aliasing in Doppler multiplexing transmission is expanded to Nt times.

[0046] However, in Doppler multiplexing transmission, as described above, the transmission signal is separated by filtering on the Doppler frequency axis. Therefore, the effective Doppler frequency bandwidth of each transmission signal is limited to 1 / (Tr×Nt), so the Doppler frequency range is the same as that in the case of time division multiplexing transmission. In addition, in Doppler multiplexing transmission, the Doppler frequency domain of the related transmission signal and the Doppler frequency domain of other transmission signals different from it are mixed in the Doppler frequency domain exceeding the effective Doppler frequency range of each transmission signal, so it may not be possible to correctly separate the transmission signal.

[0047] Therefore, in one embodiment of the present disclosure, a method is described below, which expands the range of Doppler frequencies where aliasing does not occur (in other words, ambiguity does not occur) in Doppler multiplexing transmission. As a result, a radar device in one embodiment of the present disclosure can detect a target object with good accuracy within a wider Doppler frequency range.

[0048] 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 denoted by the same reference numerals, and their descriptions are omitted due to duplication.

[0049] The following describes a structure (in other words, a MIMO radar structure) in which a radar device simultaneously sends out different multiplexed transmission signals from a plurality of transmission antennas in a transmission branch, and separates each transmission signal in a reception branch for reception processing.

[0050] 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 called "fast chirp modulation"). However, the modulation method is not limited to frequency modulation. For example, an embodiment of the present disclosure can also be applied to a radar method that uses a pulse compression radar that transmits a pulse train by phase modulation or amplitude modulation.

[0051] [Structure of radar device]

[0052] Figure 1 It is a block diagram showing the configuration of the radar device 10 according to the present embodiment.

[0053] The radar device 10 includes a radar transmitting unit (transmitting branch) 100 and a radar receiving unit (receiving branch) 200 .

[0054] The radar transmitting unit 100 generates a radar signal (radar transmission signal), and transmits the radar transmission signal at a predetermined transmission cycle using a transmission array antenna composed of a plurality of transmission antennas 105 - 1 to 105 -Nt.

[0055] The radar receiving unit 200 uses a receiving array antenna including a plurality of receiving antennas 202-1 to 202-Na to receive a radar transmission signal reflected by a target (not shown). The radar receiving unit 200 performs signal processing on the reflected wave signal received by each receiving antenna 202, for example, detecting the presence of a target or estimating the arrival direction of the reflected wave signal.

[0056] 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.

[0057] [Configuration of Radar Transmitter 100]

[0058] The radar transmitter 100 includes a radar transmission signal generator 101 , Doppler shifters 104 - 1 to 104 -Nt, and transmission antennas 105 - 1 to 105 -Nt. That is, the radar transmitter 100 has Nt transmission antennas 105 , each of which is connected to a separate Doppler shifter 104 .

[0059] The radar transmission signal generating unit 101 generates a radar transmission signal. The radar transmission signal generating unit 101 includes, for example, a modulation signal generating unit 102 and a VCO (Voltage Controlled Oscillator) 103. Hereinafter, each component of the radar transmission signal generating unit 101 will be described.

[0060] For example, Figure 2 As shown in FIG. 1 , the modulation signal generation unit 102 periodically generates a sawtooth-shaped modulation signal. Here, the radar transmission period is set to Tr.

[0061] Based on the radar transmission signal output from the modulation signal generating unit 102, the VCO 103 outputs a frequency modulation signal (hereinafter, for example, referred to as a "frequency chirp signal" or "chirp signal") to the Doppler frequency shift unit 104-1 to the Doppler frequency shift unit 104-Nt and the radar receiving unit 200 (the mixer unit 204 described later).

[0062] The Doppler frequency shift unit 104 applies a phase rotation φ to the chirp signal input from the VCO 103. n , with additional Doppler frequency shift DOP n , and outputs the Doppler shifted signal to the transmitting antenna 105. Here, n=1, ..., Nt. In addition, the additional Doppler shift amount DOP in the Doppler shift unit 104 is n (In other words, the phase rotation φ n An example of the method of ) will be described later.

[0063] The output signals of the Doppler shift units 104 - 1 to 104 -Nt are amplified to predetermined transmission power and radiated into space from each transmission antenna 105 .

[0064] [Configuration of the radar receiving unit 200]

[0065] exist Figure 1 In the embodiment, the radar receiving unit 200 includes Na receiving antennas 202, thereby forming an array antenna. In addition, the radar receiving unit 200 includes Na antenna system processing units, namely antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 210, a Doppler multiplexing separation unit 211 and a direction estimation unit 212.

[0066] Each receiving antenna 202 receives a reflected wave signal which is a radar transmission signal reflected by a target object (object), and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

[0067] Each antenna system processing unit 201 includes a wireless receiving unit 203 and a signal processing unit 206 .

[0068] The wireless receiving unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The wireless receiving unit 203 mixes the received reflected wave signal with the transmission signal, i.e., the chirp signal, in the mixer unit 204, and passes the chirp signal through the LPF 205. Thus, a beat signal is extracted, the frequency of which corresponds to the delay time of the reflected wave signal. For example, Figure 2As shown, the difference frequency between the frequency of the transmission signal (transmission frequency modulation wave) and the frequency of the reception signal (reception frequency modulation wave) is obtained as the beat frequency.

[0069] The signal processing unit 206 of each antenna system processing unit 201 - z (where z=any one of 1 to Na) includes an AD (Analog Digital) conversion unit 207 , a beat frequency analysis unit 208 , and a Doppler analysis unit 209 .

[0070] The signal (for example, the beat signal) output from the LPF 205 is converted into discrete sampling data by the AD conversion section 207 in the signal processing section 206 and is discretely sampled.

[0071] The beat frequency analysis unit 208 analyzes the N signals obtained within a predetermined time range (range gate) according to the transmission cycle Tr. data The signal processing unit 206 performs FFT processing on discrete sampling data. As a result, the signal processing unit 206 outputs a spectrum where the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave) appears at a peak. In addition, during FFT processing, the beat frequency analysis unit 208 may also multiply the window function coefficients such as the Han window or the Hamming window. By using the window function coefficients, the side lobes generated around the beat frequency peak can be suppressed.

[0072] 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 the RFT z (f b , m). Here, f b represents the beat frequency index, which corresponds to the index (binary number) of the FFT. b =0, ..., N data / 2, z=0,...,Na,m=1,...,N C In addition, in the following, N C The chirp pulse transmission of times is called a "transmission frame unit". The beat frequency index f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (in other words, the closer the distance to the target object).

[0073] 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 ”.

[0074]

[0075] Here, B w represents the frequency modulation bandwidth of the chirp signal within the range gate, and C0 represents the speed of light.

[0076] The Doppler analysis unit 209 uses the N output from the beat frequency analysis unit 208. C The beat frequency response RFT is obtained by sending chirped pulses z (f b , 1) RFT z (f b , 2), ..., RFT z (f b , N C ), indexed by distance f b Doppler analysis was performed.

[0077] For example, in N c When the value is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N c According to the sampling theorem, the maximum Doppler frequency without aliasing is ±1 / (2Tr). In addition, the Doppler frequency index f s The Doppler frequency interval is 1 / (Nc×Tr), and the Doppler frequency index f s The range is f s =-N c / 2, …, 0, …, N c / 2-1.

[0078] As an example, the following describes N c is a power of 2. In addition, c When it is not a power of 2, for example, the FFT processing can be performed with a data size of a power of 2 by including zero-padded data. In addition, the Doppler analysis unit 209 can also multiply the coefficient of a window function such as a Han window or a Hamming window during the FFT processing. By applying the window function, the side lobes generated around the beat frequency peak can be suppressed.

[0079] For example, the output VFT of the Doppler analysis unit 209 of the z-th signal processing unit 206 is z (f b , f s ) is shown in the following formula. In addition, j is an imaginary unit, z = 1 to Na.

[0080]

[0081] The above describes the processing in each component of the signal processing unit 206.

[0082] exist Figure 1In the example, the CFAR unit 210 performs CFAR processing (in other words, performs adaptive threshold determination) using the outputs of the Doppler analysis unit 209 from the first to Na-th signal processing units 206, and extracts the distance index f that gives the peak signal. b_cfar and the Doppler frequency index f s_cfar .

[0083] The CFAR unit 210 converts the outputs VFT1 (f b , f s )、VFT2(f b , f s ),…,VFT Na (f b , f s ) are added to perform a two-dimensional CFAR process including a distance axis and a Doppler frequency axis (equivalent to a relative velocity), or a CFAR process combined with a one-dimensional CFAR process. For example, the process disclosed in Non-Patent Document 2 can be applied to the two-dimensional CFAR process or the CFAR process combined with the one-dimensional CFAR process.

[0084]

[0085] The CFAR unit 210 adaptively sets a threshold value and indexes the distance at which the received power is greater than the threshold value. b_cfar , Doppler frequency index f s_cfar and receiving power information PowerFT(f b_cfar , f s_cfar ) is output to the Doppler multiplexing separation unit 211.

[0086] The Doppler demultiplexing unit 211 uses the information input from the CFAR unit 210 (for example, the distance index f b_cfar , Doppler frequency index f s_cfar and receiving power information PowerFT(f b_cfar , f s_cfar )), using the output from each Doppler analysis unit 209, the transmission signal transmitted from each transmission antenna 105 (in other words, the reflected wave signal for the transmission signal) is separated from the signal subjected to Doppler multiplexing transmission (hereinafter referred to as "Doppler multiplexing signal"). The Doppler multiplexing separation unit 211 outputs information related to the separated signal to the direction estimation unit 212, for example. The information related to the separated signal may include, for example, a distance index f corresponding to the separated signal. b_cfar and Doppler frequency index (hereinafter, sometimes also referred to as "separation index information") (f demul_Tx#1 、f demul_Tx#2 ,…,fdemul_Tx#Nt ). In addition, the Doppler demultiplexing unit 211 outputs the output from each Doppler analysis unit 209 to the direction estimation unit 212.

[0087] Hereinafter, an operation example of the Doppler demultiplexing unit 211 will be described together with the operation of the Doppler frequency shift unit 104 .

[0088] [How to set the Doppler shift amount]

[0089] First, an example of a method of setting the Doppler frequency shift amount added by the Doppler frequency shift unit 104 will be described.

[0090] The Doppler shift units 104-1 to 104-Nt each add a different Doppler shift amount DOP to the input chirp signal. n In one embodiment of the present disclosure, between the Doppler frequency shift unit 104-1 to the Doppler frequency shift unit 104-Nt (in other words, between the transmitting antenna 105-1 to the transmitting antenna 105-Nt), the Doppler frequency shift amount DOP n The intervals (Doppler frequency shift intervals) are not equal intervals, and at least one Doppler interval is different.

[0091] In other words, the Doppler shift DOP n The Doppler frequency range (-1 / (2Tr) to 1 / (2Tr)) that satisfies the sampling theorem is not divided into equal intervals, but divided in a way that at least one interval is different. Here, as long as the phase rotation of each transmission period Tr is in the range of -π to π, the sampling theorem is satisfied. Therefore, the Doppler frequency shift DOP n Use the following phase rotation φ n (m), the phase rotation φ n (m) The range from -π to π, that is, the phase range of 2π is not divided into equal intervals, but is divided into different intervals at least one.

[0092] For example, when Nt=2, if φ1(m)=π / 2×m and φ2(m)=-π / 2×m, then |φ1(m)-φ2(m)|=π, and the phase range of 2π is divided into equal intervals. One embodiment of the present disclosure does not use this phase rotation that divides the phase range of 2π into equal intervals as the Doppler shift amount. One embodiment of the present disclosure uses phase rotations φ1(m) and φ2(m) where |φ1(m)-φ2(m)|≠π as Doppler shift amounts DOP1 and DOP2. In addition, when Nt≧2, one embodiment of the present disclosure includes |φ1(m)-φ2(m)|≠π. n (m)-φ adjacent(n) The phase rotation of (m)|≠2π / Nt is taken as the Doppler frequency shift DOP nHere, n is an integer value ranging from 1 to Nt. In addition, adjacent(n) represents the value of n (m) The index of the adjacent phase rotation, n The phase rotation difference (φ) between n (m)-φ n1 (m)) indicates that the minimum index n1 is reached using a modulo operation of 2π.

[0093] For example, the n-th Doppler frequency shift unit 104 adds Doppler frequency shift amounts DOP different from each other to the input m-th chirp signal. n The phase rotation φ n (m) and output. Thus, different Doppler frequency shift amounts are added to the transmission signals transmitted from the plurality of transmission antennas 105. That is, in one embodiment, the Doppler multiplexing number N DM =Nt. Here, m=1, ..., N C , n=1,…,Nt.

[0094] In addition, the Doppler analysis unit 209 derives the Doppler frequency f that does not cause aliasing based on the sampling theorem. d The range is -1 / (2Tr)≦f d <1 / (2Tr).

[0095] Therefore, it is assumed that for the transmission signals transmitted from Nt transmission antennas 105, the Doppler frequency shift intervals are equal to the phase rotation φ of 1 / (Nt×Tr). n (m) is represented by the following formula.

[0096]

[0097] Here, φ0 is the initial phase, and Δφ0 is the reference Doppler frequency shift phase. In addition, round(x) is a round function that outputs an integer value obtained by rounding off the real value x. In addition, in order to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 209, round(N C / N t ) item.

[0098] Assume that the phase rotation φ shown in equation (4) is used. n In the case of (m), the intervals of phase rotation between the transmission signals added to the m-th chirp signal are all equal, which is 2πround(N C / N t ) / N C .

[0099] As an example, in equation (4), Nt = 2, Δφ0 = 0, φ0 = 0, and NC Set to an even number and add a phase rotation φ n In the case of (m), the Doppler shift amounts are DOP1=0 and DOP2=1 / (2Tr).

[0100] In other words, the intervals of the Doppler shift amounts added to the transmission signals transmitted from the plurality of transmission antennas 105 are set by the radar device 10 (radar receiving unit 200) to be equal intervals within the Doppler frequency range (e.g., the Doppler frequency range where aliasing does not occur). For example, the intervals of the Doppler shift amounts added to the transmission signals transmitted from Nt=2 transmission antennas 105 are set to be equal to the number of transmission antennas 105 (e.g., Nt=2) within the Doppler frequency range where aliasing does not occur (e.g., -1 / (2Tr)≦f d <1 / (2Tr)) divided into intervals (in the above example, 1 / (2Tr)).

[0101] Figure 3 The figure shows an example of Doppler peaks obtained by Doppler analysis in the Doppler analysis unit 209 assuming that Doppler shift amounts DOP1=0 and DOP2=1 / (2Tr) are used for transmission signals transmitted from Nt=2 transmission antennas 105 (hereinafter referred to as "Tx#1" and "Tx#2").

[0102] like Figure 3 As shown, for a measured target Doppler frequency f d_TargetDoppler , generating Nt (in Figure 3 , Nt=2) Doppler peak.

[0103] As an example, in Figure 3 In the comparison, the position relationship between the following Doppler peaks is compared, and the Doppler peak is the measured target Doppler frequency f d_TargetDoppler = -1 / (4Tr) and f d_TargetDoppler =1 / (4Tr), the Doppler peak generated when a reflected wave signal for a transmission signal transmitted from the transmission antenna Tx#1 is received, and the Doppler peak generated when a reflected wave signal for a transmission signal transmitted from the transmission antenna Tx#2 is received.

[0104] <Target Doppler frequency f d_TargetDoppler =-1 / (4Tr)>

[0105] In f d_TargetDoppler =-1 / (4Tr), if Figure 3As shown in FIG. 1 , the positional relationship is the positional relationship between the Doppler peak (P1) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#1 is received, and the Doppler peak (P2) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#2 is received. The Doppler interval between the Doppler peak P1 and the Doppler peak P2 is 1 / (2Tr).

[0106] <Target Doppler frequency f d_TargetDoppler =1 / (4Tr)>

[0107] In f d_TargetDoppler =1 / (4Tr), if Figure 3 As shown in FIG. 1 , the Doppler peak generated when the reflected wave signal for the transmission signal from the transmission antenna Tx#2 is received is output as the peak value (P2A) of the aliased signal by FFT. d_TargetDoppler =1 / (4Tr), if Figure 3 As shown in FIG. 1 , the positional relationship is the positional relationship between the Doppler peak (P1) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#1 is received and the Doppler peak (P2A) of the aliased signal. The Doppler interval between the Doppler peak (P1) and the Doppler peak (P2A) is 1 / (2Tr).

[0108] Thus, in f d_TargetDoppler =-1 / (4Tr), and in the case of f d_TargetDoppler =1 / (4Tr), the Doppler interval between the Doppler peak (P1) corresponding to the transmitting antenna Tx#1 and the Doppler peak (P2 or P2A) corresponding to the transmitting antenna Tx#2 is 1 / (2Tr). d_TargetDoppler = -1 / (4Tr) and 1 / (4Tr), the positional relationship of the Doppler peaks corresponding to Tx#1 and Tx#2 cannot be distinguished, resulting in ambiguity. Figure 3 In the example shown, the target Doppler frequency range that does not cause ambiguity is, for example, -1 / (4Tr)≦f d_TargetDoppler <1 / (4Tr).

[0109] On the other hand, in the Doppler shift unit 104 of one embodiment of the present disclosure, as described above, the Doppler shift amount DOP added to the transmission signal transmitted from the transmission antenna 105 is n (or phase rotation φ n (m)) have at least one different interval.

[0110] For example, the Doppler frequency shift unit 104 increases the interval of the Doppler frequency shift added to the transmission signals transmitted from the Nt transmission antennas 105 as much as possible and rotates the phase by φ n (m) at least one interval different way to add Doppler shift DOP n Thereby, the separation performance of Doppler multiplexing can be improved.

[0111] For example, the n-th Doppler frequency shift unit 104 adds Doppler frequency shift amounts DOP different from each other to the input m-th chirp signal. n The phase rotation φ is as follows n (m).

[0112]

[0113] Here, A is a coefficient with a positive or negative polarity of 1 or -1. In addition, δ is a positive number greater than 1. In order to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 209, round(N C / (Nt+δ)).

[0114] As an example, in equation (5), Nt=2, Δφ0=0, φ0=0, A=1, δ=1, and NC is set to a multiple of 3 and a phase rotation φ is added. n In the case of (m), the Doppler shift amounts are DOP1=0 and DOP2=1 / (3Tr).

[0115] Figure 4 The figure shows an example of Doppler peaks obtained by Doppler analysis in the Doppler analysis unit 209 when Doppler shift amounts DOP1=0 and DOP2=1 / (3Tr) are used for transmission signals transmitted from Nt=2 transmission antennas 105 (hereinafter referred to as "Tx#1" and "Tx#2").

[0116] like Figure 4 As shown, for a measured target Doppler frequency f d_TargetDoppler , generating Nt (in Figure 4 , Nt=2) Doppler peak.

[0117] As an example, in Figure 4 In the comparison, the position relationship between the following Doppler peaks is compared, and the Doppler peak is the measured target Doppler frequency f d_TargetDoppler = -1 / (4Tr) and f d_TargetDoppler=1 / (4Tr), the Doppler peak generated when the reflected wave signal of the transmission signal transmitted from the transmission antenna Tx#1 is received, and the Doppler peak generated when the reflected wave signal of the transmission signal transmitted from the transmission antenna Tx#2 is received.

[0118] <Target Doppler frequency f d_TargetDoppler =-1 / (4Tr)>

[0119] In f d_TargetDoppler =-1 / (4Tr), if Figure 4 As shown in FIG. 1 , the positional relationship is the positional relationship between the Doppler peak (P1) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#1 is received, and the Doppler peak (P2) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#2 is received. The Doppler interval between the Doppler peak P1 and the Doppler peak P2 is 1 / (3Tr).

[0120] <Target Doppler frequency f d_TargetDoppler =1 / (4Tr)>

[0121] In f d_TargetDoppler =1 / (4Tr), the Doppler peak generated when the reflected wave signal for the transmission signal from the transmission antenna Tx#2 is received is output as the peak value (P2A) of the aliased signal by FFT. d_TargetDoppler =1 / (4Tr), the above positional relationship is the positional relationship between the Doppler peak (P1) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#1 is received and the Doppler peak (P2A) of the above aliased signal. The Doppler interval between the Doppler peak (P1) and the peak (P2A) is 2 / (3Tr).

[0122] like Figure 4 As shown, at the target Doppler frequency f d_TargetDoppler =-1 / (4Tr), and in the case of f d_TargetDoppler =1 / (4Tr), the positional relationship between the Doppler peak (P1) corresponding to the transmission antenna Tx#1 and the Doppler peak (P2 or P2A) corresponding to the transmission antenna Tx#2 are different from each other.

[0123] Thus, each interval of the Doppler frequency shift amount added to the transmission signal transmitted from the plurality of transmission antennas 105 is set to an unequal interval within the range of Doppler frequencies to be analyzed (e.g., the Doppler frequency range where aliasing does not occur). For example, the interval of the Doppler frequency shift amount added to the transmission signal transmitted from Nt=2 transmission antennas 105 is set to divide the Doppler frequency range where aliasing does not occur (e.g., -1 / (2Tr)≦f d <1 / (2Tr)) (in the above example, 1 / (3Tr)).

[0124] Thus, for example, Figure 4 As shown, the Doppler interval (1 / (3Tr)) in the case without aliasing (e.g., Doppler peak (P1) and Doppler peak (P2)) is different from the Doppler interval (2 / (3Tr)) in the case with aliasing (e.g., Doppler peak (P1) and Doppler peak (P2A)).

[0125] Therefore, in Figure 4 In the example shown, the Doppler demultiplexing unit 211 can distinguish the target Doppler frequency f d_TargetDoppler = -1 / (4Tr) (in other words, no aliasing), and f d_TargetDoppler =1 / (4Tr) (in other words, there is aliasing).

[0126] For example, in the case where the target Doppler frequency is assumed to be -1 / (2Tr) ≤ f d_TargetDoppler <1 / (2Tr), the Doppler demultiplexing unit 211 can determine the target Doppler frequency f d_TargetDoppler = -1 / (4Tr), no aliased signal is included. Figure 4 The f d_TargetDoppler =-1 / (4Tr), the Doppler demultiplexing unit 211 can determine that the reflected wave signals are the transmission signals from the transmission antennas Tx#1 and Tx#2, based on the Doppler peak that does not include an aliasing signal and has the smallest frequency.

[0127] In addition, for example, when the target Doppler frequency is assumed to be -1 / (2Tr) ≤ f d_TargetDoppler <1 / (2Tr), the Doppler demultiplexing unit 211 can determine the target Doppler frequency f d_TargetDoppler =1 / (4Tr), the Doppler peak after aliasing (e.g., P2A) is included and can be determined as the Doppler frequency f d_TargetDoppler =1 / (4Tr). Thus, for example, Figure 4 The f d_TargetDoppler =1 / (4Tr), because the aliasing signal (P2A) is included, the Doppler multiplexing separation unit 211 can determine that the higher Doppler peak among the Doppler peaks whose interval between Doppler peaks reaches 2 / (3Tr) is the reflected wave signal corresponding to the transmitting antenna Tx#1, and the lower Doppler peak is the reflected wave signal corresponding to the transmitting antenna Tx#2.

[0128] Next, as another example, in Figure 4 In the comparison, the position relationship between the following Doppler peaks is compared, and the Doppler peak is the measured target Doppler frequency f d_TargetDoppler = -1 / (2Tr) and f d_TargetDoppler =1 / (2Tr), the Doppler peak generated when the reflected wave signal of the transmission signal transmitted from the transmission antenna Tx#1 is received, and the Doppler peak generated when the reflected wave signal of the transmission signal transmitted from the transmission antenna Tx#2 is received.

[0129] <Target Doppler frequency f d_TargetDoppler =-1 / (2Tr)>

[0130] In f d_TargetDoppler =-1 / (2Tr), if Figure 4 As shown in FIG. 1 , the positional relationship is the positional relationship between the Doppler peak (P1) generated when the reflected wave signal for the transmission signal from the transmission antenna Tx#1 is received, and the Doppler peak (P2) generated when the reflected wave signal for the transmission signal from the transmission antenna Tx#2 is received. The Doppler interval between the Doppler peak (P1) and the Doppler peak (P2) is 1 / (3Tr).

[0131] <Target Doppler frequency f d_TargetDoppler =1 / (2Tr)>

[0132] In f d_TargetDoppler =1 / (2Tr), if Figure 4 As shown, the Doppler peak generated when the reflected wave signal for the transmission signal from the transmission antenna Tx#2 is received is FFT-output as the Doppler peak (P2A) of the aliased signal. Therefore, the above positional relationship is the positional relationship between the Doppler peak (P1) generated when the reflected wave signal for the transmission signal from the transmission antenna Tx#1 is received and the Doppler peak (P2A) of the aliased signal. The Doppler interval between the Doppler peak (P1) and the Doppler peak (P2A) is 1 / (3Tr).

[0133] Thus, at the target Doppler frequency f d_TargetDoppler=-1 / (2Tr), and in the case of f d_TargetDoppler =1 / (2Tr), the Doppler interval between the Doppler peak (P1) corresponding to the transmitting antenna Tx#1 and the Doppler peak (P2 or P2A) corresponding to the transmitting antenna Tx#2 is 1 / (3Tr). d_TargetDoppler =-1 / (2Tr), and in the case of f d_TargetDoppler =1 / (2Tr), the positional relationship of the Doppler peaks corresponding to Tx#1 and Tx#2 cannot be distinguished, resulting in ambiguity. Figure 4 In the example shown, the target Doppler frequency range that does not cause ambiguity is, for example, -1 / (2Tr)≦f d_TargetDoppler <1 / (2Tr).

[0134] Therefore, according to the present embodiment, compared with the case of time division multiplexing or the case of setting the Doppler shift amount to an equal interval (for example, see Figure 3 ), the target Doppler frequency range that does not produce ambiguity can be expanded to Nt times (for example, Figure 4 2 times in the middle).

[0135] Next, an example of a method of separating signals corresponding to the respective transmission antennas 105 in the Doppler demultiplexing unit 211 will be described.

[0136] As an example, the operation of the Doppler demultiplexing unit 211 in the case of Nt=2 will be described.

[0137] As an example, the following describes a case where the phase rotation φ shown in equation (5) is added to the Doppler frequency shift unit 104. n (m) In the following, as an example, Δφ0=0, φ0=0, δ=1, and N C It is set to a multiple of 3. When A=1, the Doppler shift amount for each transmission antenna 105 is DOP1=0, DOP2=1 / (3Tr), and when A=-1, the Doppler shift amount for each transmission antenna 105 is DOP1=0, DOP2=-1 / (3Tr).

[0138] In this case, the Doppler demultiplexing unit 211 uses the peak value (distance index f) of the received power greater than the threshold value input from the CFAR unit 210. b_cfar and the Doppler frequency index f s_cfar ), separate the Doppler multiplexed signal.

[0139] For example, the Doppler demultiplexing unit 211 calculates the distance index f b_cfar The same multiple Doppler frequency index f s_cfar, and determines from which transmission antenna Tx#1 to Tx#Nt the reflected wave signal corresponds to the transmission signal. The Doppler demultiplexing unit 211 separates and outputs the determined reflected wave signals from each of the transmission antennas Tx#1 to Tx#Nt.

[0140] Next, the distance index f is described. b_cfar The same multiple Doppler frequency index f s_cfar There are Ns actions. For example, f s_cfar ∈{fd #1 、fd #2 …、fd #Ns}.

[0141] For example, the Doppler demultiplexing unit 211 calculates the distance index f b_cfar The same multiple Doppler frequency index f s_cfar ∈{fd #1 、fd #2 …、fd #Ns}, calculate the Doppler index interval.

[0142] Here, for one target Doppler frequency f, the Doppler frequency shift amounts DOP1 and DOP2 added to the transmission signals transmitted from the transmission antenna Tx#1 and the transmission antenna Tx#2 are calculated. d_TargetDoppler , generating Nt = 2 Doppler peaks. According to the difference between the phase rotation φ1(m) for the transmitting antenna Tx#1 and the phase rotation φ2(m) for the transmitting antenna Tx#2 shown in the following equation, the Doppler index interval equivalent to the Doppler interval between the Doppler peaks is round(N c / (Nt+1)). In addition, when an aliasing signal is included, the Doppler index interval corresponding to the Doppler interval between Doppler peaks is N c -round(N c / (Nt+1)).

[0143]

[0144] Next, the Doppler demultiplexing unit 211 searches for a Doppler index interval round (N ) corresponding to the interval of the Doppler frequency shift amount when no aliasing signal is included. c / (Nt+1)) or a Doppler frequency index interval (Nt) corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included. c -round(N c / (Nt+1))) consistent Doppler frequency index.

[0145] The Doppler demultiplexing unit 211 performs the following processing based on the above-mentioned search result.

[0146] (1) There is an index interval round (N) corresponding to the interval of the Doppler shift amount when the aliasing signal is not included c / (Nt+1)), the Doppler demultiplexing unit 211 outputs an index pair of these Doppler frequency indices (for example, represented by “fd #p , fd #q ”) as the separation index information of the Doppler multiplexed signal (f demul_Tx#1 、f demul_Tx#2 ).

[0147] Here, when the Doppler shift amounts for the transmission antenna Tx#1 and the transmission antenna Tx#2 are in the relationship of DOP1<DOP2, the Doppler demultiplexing unit 211 converts fd #p 、fd #q The larger one of the two is determined as the Doppler frequency index f corresponding to Tx#2. demul_Tx#2 and the smaller one is determined as the Doppler frequency index f corresponding to Tx#1 demul_Tx#1 On the other hand, when the Doppler shift amounts for the transmission antenna Tx#1 and the transmission antenna Tx#2 are in the relationship of DOP1>DOP2, the Doppler demultiplexing unit 211 converts fd #p 、fd #q The larger one of the two is determined as the Doppler frequency index f corresponding to Tx#1. demul_Tx#1 and the smaller one is determined as the Doppler frequency index f corresponding to Tx#2 demul_Tx#2 .

[0148] (2) When there is an index interval N corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included c -round(N c / (Nt+1)), the Doppler frequency index that matches the Doppler frequency index, the Doppler demultiplexing unit 211 outputs an index pair of these Doppler frequency indexes (for example, fd #p , fd #q ) as the separation index information of the Doppler multiplexed signal (f demul_Tx#1 、f demul_Tx#2 ).

[0149] Here, when the Doppler shift amounts for the transmission antenna Tx#1 and the transmission antenna Tx#2 are in the relationship of DOP1<DOP2, the Doppler demultiplexing unit 211 converts fd #p 、fd #q The larger one of the two is determined as the Doppler frequency index f corresponding to Tx#1.demul_Tx#1 and the smaller one is determined as the Doppler frequency index f corresponding to Tx#2 demul_Tx#2 On the other hand, when the Doppler shift amounts for the transmission antenna Tx#1 and the transmission antenna Tx#2 are in the relationship of DOP1>DOP2, the Doppler demultiplexing unit 211 converts fd #p 、fd #q The larger one of the two is determined as the Doppler frequency index f corresponding to Tx#2. demul_Tx#2 and the smaller one is determined as the Doppler frequency index f corresponding to Tx#1 demul_Tx#1 .

[0150] (3) The index interval round (N) is equal to the interval of the Doppler frequency shift amount when no aliasing signal is included. c / (Nt+1)) and there is no index interval N corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included. c -round(N c / (Nt+1)), the Doppler demultiplexing unit 211 determines that the generated Doppler peak is a noise component. In this case, the Doppler demultiplexing unit 211 may not output the separation index information (f demul_Tx#1 、f demul_Tx#2 ).

[0151] (4) When there is an index interval round (N) corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is not included c / (Nt+1)) and is consistent with the index interval N corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included. c -round(N c / (Nt+1)), the Doppler demultiplexing unit 211 performs deduplication processing as described below, for example.

[0152] For example, the index interval round (N c / (Nt+1)) is represented by the index pair of Doppler frequency indices that are consistent with each other as (fd #p , fd #q1 ). In addition, the index interval N corresponding to the interval of the Doppler frequency shift amount in the case of including the aliasing signal is c -round(N c / (Nt+1)) is represented by the index pair of Doppler frequency indices that are consistent with each other as (fd #p 、fd #q2 ).

[0153] The Doppler demultiplexing unit 211 calculates, for example, an index pair of Doppler frequency indices (fd #p 、fd #q1 )'s power differential |PowerFT(f b_cfar , fd #q1 )-PowerFT(f b_cfar , fd #p )|, and the index pair of Doppler frequency index (fd #p , fd #q2 )'s power differential |PowerFT(f b_cfar , fd #q2 )-PowerFT(f b_cfar , fd #p When the power (in other words, the difference) between these power differences is greater than a predetermined power threshold TPL, the Doppler demultiplexing unit 211 adopts an index pair of Doppler frequency indices having a smaller power difference between the index pairs.

[0154] For example, when the following equation is satisfied, the Doppler demultiplexing unit 211 uses the index pair (fd #p , fd #q2 ), and perform the processing of (2) above.

[0155] |PowerFT(f b_cfar , fd #q1 )-PowerFT(f b_cfar , fd #p )|-|PowerFT(f b_cfar , fd #q2 )-PowerFT(f b_cfar , fd #p )|>TPL (7)

[0156] For another example, when the following equation is satisfied, the Doppler demultiplexing unit 211 uses the index pair (fd #p , fd #q1 ) and perform the processing of (1) above.

[0157] |PowerFT(f b_cfar , fd #q2 )-PowerFT(f b_cfar , fd #p )|-|PowerFT(f b_cfar , fd #q1 )-PowerFT(f b_cfar , fd #p )|>TPL (8)

[0158] When equations (7) and (8) are not satisfied, the Doppler demultiplexing unit 211 performs the above-mentioned process (3) without using any index pair of Doppler frequency indices.

[0159] Thereby, the Doppler multiplexing and demultiplexing unit 211 can separate the Doppler multiplexed signal.

[0160] The above is a description of an operation example of the Doppler demultiplexing unit 211 .

[0161] exist Figure 1 In the example, the direction estimation unit 212 calculates the distance index f based on the information input from the Doppler demultiplexing unit 211 (for example, the distance index f b_cfar and separate index information (f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt )) to estimate the direction of the target.

[0162] For example, the direction estimation unit 212 extracts the signal corresponding to the distance index f from the output of the Doppler demultiplexing unit 211. b_cfar and separate index information (f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt ) output, generating the virtual receive array correlation vector h(f b_cfar 、f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt ) and perform direction estimation processing.

[0163] Virtual receiving array correlation vector h(f b_cfar 、f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt ) contains the product of the number of transmitting antennas Nt and the number of receiving antennas Na, that is, Nt×Na elements. The virtual receiving array correlation vector h(f b_cfar 、f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt ) is used for the following processing, which estimates the direction of the reflected wave signal from the target based on the phase difference between each receiving antenna 202.

[0164] Here, z=1,…,Na.

[0165]

[0166] In formula (9), h cal[b] b is an array correction value for correcting the phase deviation and amplitude deviation between the transmission array antennas and the reception array antennas. b = 1, ..., (Nt × Na).

[0167] The direction estimation unit 212 changes the direction estimation evaluation function value P within a predetermined angle range, for example. H (θ、f b_cfar 、f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt ) and calculates the spatial distribution. The direction estimation unit 212 extracts a predetermined number of the maximum peaks of the calculated spatial distribution in descending order, and outputs the azimuth direction of the maximum peak as an estimated value of the arrival direction (for example, positioning output).

[0168] In addition, for the direction estimation evaluation function value P H (θ BEAM_cfar 、f b_cfar 、f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt ), there are various methods depending on the arrival direction estimation algorithm. For example, the estimation method using an array antenna disclosed in non-patent document 3 may also be used.

[0169] For example, in Nt×Na virtual receiving arrays with equal intervals d H When arranged in a straight line, the beam forming method can be expressed as follows: Alternatively, methods such as Capon and MUSIC can be applied in the same manner.

[0170] P H (θ u ,f b_cfar ,f demul_Tx#1 ,f demul_Tx#2 ,...,f demul_Tx#Nt )=|a H (θ u )h(f b_cfar ,f demul_Tx#1 ,f demul_Tx#2 ,...,f demul_Tx#Nt )| 2 (10)

[0172]

[0173] Here, in equation (10), the superscript H is the Hermitian transposition operator. u ) represents the direction vector of the virtual receiving array of the arriving wave relative to the azimuth direction θu.

[0174] In addition, the azimuth direction θ u is a vector that changes at a predetermined azimuth interval β1 within the azimuth range for estimating the direction of arrival. For example, θ is set as follows u .

[0175] θ u =θ min +uβ1,u=0、…、NU

[0176] NU=floor[(θ max -θ min ) / β1]+1

[0177] Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0178] In addition, the Doppler frequency information may be converted into a relative velocity component and output. d (f s ), can be converted using the following formula. Here, λ is the wavelength of the carrier frequency of the RF signal output from the wireless transmission unit (not shown). In addition, Δ f is the Doppler frequency interval in the FFT processing of the Doppler analysis unit 209. For example, in this embodiment, Δ f =1 / (N C Tr).

[0179]

[0180] As described above, in the present embodiment, the radar device 10 includes a plurality of transmission antennas 105 for transmitting transmission signals, and a Doppler shift unit 104 for adding different Doppler shift amounts to the transmission signals for each of the plurality of transmission antennas 105. In addition, in the radar device 10, the intervals of the Doppler shift amounts added to the transmission signals transmitted from the plurality of transmission antennas 105 are set by the radar device 10 to be unequal intervals within the range of the Doppler frequency.

[0181] Thus, the radar device 10 can make the intervals of the Doppler peaks corresponding to each transmission signal different when there is aliasing and when there is no aliasing. In other words, the radar device 10 can determine whether there is aliasing in the Doppler peak. Thus, the radar device 10 can distinguish the target Doppler frequency (target doppler) when aliasing occurs and the target Doppler frequency when aliasing does not occur and separate the Doppler multiplexed signal. Thus, the radar device 10 can expand the Doppler frequency range (or the maximum value of the relative speed) in which the Doppler multiplexed signal can be separated.

[0182] As described above, according to this embodiment, the Doppler frequency range (or the maximum value of the relative velocity) where ambiguity does not occur can be expanded. As a result, the radar device 10 can detect the target object (for example, the arrival direction) with good accuracy in a wider Doppler frequency range.

[0183] (Transformation 1)

[0184] In the above-mentioned embodiment, an operation example of Doppler multiplexing is described in the case where Nt = 2. However, the number of transmission antennas Nt is not limited to 2, and may be 3 or more.

[0185] In Modification 1, as another example, the operation of the radar device 10 in the case of Nt=3 will be described.

[0186] As an example, the phase rotation φ shown in equation (5) is added to the Doppler frequency shift unit 104. n (m) is described below. In addition, as an example, Δφ0=0, φ0=0, δ=1, and N C For example, when A=1, the Doppler frequency shift amount for each transmitting antenna 105 is DOP1=0, DOP2=1 / (4Tr), and DOP3=1 / (2Tr). For another example, when A=-1, the Doppler frequency shift amount for each transmitting antenna 105 is DOP1=0, DOP2=-1 / (4Tr), and DOP3=-1 / (2Tr).

[0187] When using this Doppler shift amount, for example, Figure 5 As shown, for a measured target Doppler frequency f d_TargetDoppler , generating Nt (in Figure 5 There are three Doppler peaks. Figure 5 This is a diagram showing changes in the Doppler peak value of Nt=3 when the horizontal axis represents the target Doppler frequency and the vertical axis represents the output of the Doppler analysis unit 209 (FFT).

[0188] <Target Doppler frequency is 0≦f d_TargetDoppler <1 / (2Tr)>

[0189] like Figure 5 As shown, the Doppler interval between the Doppler peak (solid line) generated when the reflected wave signal of the transmission signal from the transmitting antenna Tx#1 is received and the Doppler peak (dashed line) generated when the reflected wave signal of the transmission signal from the transmitting antenna Tx#3 is received is 1 / (2Tr).

[0190] In addition, in this case, Tx#3 contains an aliased signal. Therefore, the Doppler demultiplexing unit 211 can determine that the higher Doppler peak among the Doppler peaks whose interval reaches 1 / (2Tr) is the reflected wave signal corresponding to the transmitting antenna Tx#1, the lower Doppler peak is the reflected wave signal corresponding to the transmitting antenna Tx#3, and the remaining Doppler peak is the reflected wave signal from the transmitting antenna Tx#2.

[0191] <Target Doppler frequency is -1 / (2Tr)≦f d_TargetDoppler <Case 0>

[0192] like Figure 5 As shown in FIG. 1 , the Doppler interval between the Doppler peak (solid line) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#1 is received and the Doppler peak (dotted line) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#2 is received is 1 / (4Tr). In addition, the Doppler interval between the Doppler peak (dotted line) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#2 is received and the Doppler peak (broken line) generated when the reflected wave signal of the transmission signal from the transmission antenna Tx#3 is received is 1 / (4Tr).

[0193] In this case, none of the transmission antennas Tx#1, Tx#2, and Tx#3 contains an aliasing signal. Therefore, the Doppler demultiplexing unit 211 can identify the reflected wave signals for the transmission signals from the transmission antennas Tx#1, Tx#2, and Tx#3, starting from the Doppler peak with a low frequency.

[0194] Thus, each interval of the Doppler shift amount added to the transmission signal transmitted from the plurality of transmission antennas 105 is within the Doppler frequency range (in Figure 5 In the example, for example, -1 / (2Tr)≦f d <1 / (2Tr)) is set to unequal intervals. For example, each interval of the Doppler frequency shift amount added to the transmission signal transmitted from Nt=3 transmission antennas is set to the value obtained by adding δ=1 to the number of transmission antennas (for example, Nt=3), and the Doppler frequency range where aliasing does not occur is divided (for example, -1 / (2Tr)≦f d <1 / (2Tr)) (in the above example, 1 / (4Tr)).

[0195] Thus, for example, Figure 5 As shown, the Doppler interval (1 / (4Tr)) in the case without aliasing is different from the Doppler interval (1 / (4Tr) and 1 / (2Tr)) in the case with aliasing.

[0196] Therefore, in Figure 5 In the example shown, the Doppler demultiplexing unit 211 can distinguish the target Doppler frequency as -1 / (2Tr)≦f d_TargetDoppler <0 (in other words, no aliasing), and the target Doppler frequency is 0 ≤ f d_TargetDoppler <1 / (2Tr) (in other words, there is aliasing).

[0197] Therefore, in Figure 5In the example shown, the target Doppler frequency range that does not cause ambiguity is, for example, -1 / (2Tr)≦f d_TargetDoppler <1 / (2Tr).

[0198] Therefore, it is different from the case where time division multiplexing or Doppler frequency shift is set to equal intervals (in Figure 5 Compared with the Doppler multiplexing of 1 / (3Tr) in the case ... Figure 5 3 times in the middle).

[0199] Next, an example of a method of separating signals corresponding to the respective transmission antennas 105 in the Doppler demultiplexing unit 211 will be described.

[0200] The Doppler demultiplexing unit 211 uses the peak value (range index f) of the received power greater than the threshold value input from the CFAR unit 210. b_cfar and the Doppler frequency index f s_cfar ), separate the Doppler multiplexed signal.

[0201] For example, the Doppler demultiplexing unit 211 calculates the distance index f b_cfar The same multiple Doppler frequency index f s_cfar It is determined from which transmission antenna Tx#1 to Tx#Nt the reflected wave signal corresponds to the transmission signal. The Doppler demultiplexing unit 211 separates and outputs the determined reflected wave signals from each of the transmission antennas Tx#1 to Tx#Nt.

[0202] For example, the Doppler demultiplexing unit 211 calculates the distance index f b_cfar The same multiple Doppler frequency index f s_cfar ∈{fd #1 、fd #2 …、fd #Ns}, calculate the Doppler index interval.

[0203] Next, the Doppler demultiplexing unit 211 searches for an index interval round (N) corresponding to the interval between two Doppler indexes when three Doppler frequency indices are observed in ascending order and the interval between two Doppler indexes corresponding to the interval between the Doppler frequency shift amounts when no aliasing signal is included. c / (Nt+1)) and round(N c Alternatively, the Doppler demultiplexing unit 211 searches for an index interval round (Nt) corresponding to the interval between two Doppler indexes when three Doppler frequency indexes are observed in ascending order and the interval between two Doppler indexes corresponding to the interval of the Doppler frequency shift amount when an aliasing signal is included. c / (Nt+1)) and Nc -round(N c / (Nt+1)), or Nc-round(N c / (Nt+1)) and round(N c / (Nt+1)) consistent Doppler frequency index combination.

[0204] The Doppler demultiplexing unit 211 performs the following processing based on the above-mentioned search result.

[0205] (1) There is an index interval round (N) corresponding to the interval of the Doppler shift amount when the aliasing signal is not included c / (Nt+1)) and round(N c / (Nt+1)), the Doppler demultiplexing unit 211 outputs the combination of these Doppler frequency indices (for example, represented by “fd #p1 , fd #p2 , fd #p3 ”) as the separation index information of the Doppler multiplexed signal (f demul_Tx#1 、f demul_Tx#2 、f demul_Tx#3 ).

[0206] Here, when the Doppler shift amounts for the transmission antennas Tx#1 to Tx#3 are in the relationship of DOP1<DOP2<DOP3, the Doppler demultiplexing unit 211 will demultiplex the transmission antennas Tx#1 to Tx#3 from fd #p1 、fd #p2 、fd #p3 The larger one of the two is determined as the Doppler frequency index f corresponding to Tx#3, Tx#2, and Tx#1, respectively. demul_Tx#3 、f demul_Tx#2 、f demul_Tx#1 In addition, when the Doppler frequency shift amounts for the transmission antennas Tx#1 to Tx#3 are in the relationship of DOP1>DOP2>DOP3, the Doppler demultiplexing unit 211 will demultiplex fd #p1 、fd #p2 、fd #p3 The larger one of the two is determined as the Doppler frequency index f corresponding to Tx#1, Tx#2, and Tx#3, respectively. demul_Tx#1 、f demul_Tx#2 、f demul_Tx#3 .

[0207] (2) When there is an index interval Nc-round (N) corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included c / (Nt+1)) and round(N c / (Nt+1)), the Doppler demultiplexing unit 211 outputs the combination of these Doppler frequency indices (for example, represented by “fd #q1 , fd #q2 , fd #q3 ”) as the separation index information of the Doppler multiplexed signal (f demul_Tx#1 、f demul_Tx#2 、f demul_Tx#3 ).

[0208] Here, when the Doppler shift amounts for the transmission antennas Tx#1 to Tx#3 are in the relationship of DOP1<DOP2<DOP3, the Doppler demultiplexing unit 211 will demultiplex the transmission antennas Tx#1 to Tx#3 from fd #q1 、fd #q2 、fd #q3 The larger one of the two is determined as the Doppler frequency index f corresponding to Tx#2, Tx#1, and Tx#3, respectively. demul_Tx#2 、f demul_Tx#1 、f demul_Tx#3 In addition, when the Doppler frequency shift amounts for the transmission antennas Tx#1 to Tx#3 are in the relationship of DOP1>DOP2>DOP3, the Doppler demultiplexing unit 211 will demultiplex fd #q1 、fd #q2 、fd #q3 The larger one among them is determined as f corresponding to Tx#2, Tx#3, and Tx#1 respectively. demul_Tx#2 、f demul_Tx#3 、f demul_Tx#1 .

[0209] (3) When there is an index interval round (N) corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included c / (Nt+1)) and N c -round(N c / (Nt+1)), the Doppler demultiplexing unit 211 outputs the combination of these Doppler frequency indices (for example, represented by “fd #u1 , fd #u2 , fd #u3 ”) as the separation index information of the Doppler multiplexed signal (f demul_Tx#1 、f demul_Tx#2 、f demul_Tx#3 ).

[0210] Here, when the Doppler shift amounts for the transmission antennas Tx#1 to Tx#3 are in the relationship of DOP1<DOP2<DOP3, the Doppler demultiplexing unit 211 will demultiplex the transmission antennas Tx#1 to Tx#3 from fd #u1 、fd#u2 、fd #u3 The larger one of them is determined as f corresponding to Tx#1, Tx#3, and Tx#2 respectively. demul_Tx#3 、f demul_Tx#2 、f demul_Tx#1 In addition, when the Doppler frequency shift amounts for the transmission antennas Tx#1 to Tx#3 are in the relationship of DOP1>DOP2>DOP3, the Doppler demultiplexing unit 211 will demultiplex fd #u1 、fd #u2 、fd #u3 The larger one among them is determined as f corresponding to Tx#3, Tx#1, and Tx#2 respectively. demul_Tx#3 、f demul_Tx#1 、f demul_Tx#2 .

[0211] (4) The Doppler demultiplexing unit 211 determines that the Doppler peak corresponding to the Doppler frequency index that does not match any of the above (1), (2) and (3) is a noise component. In this case, the Doppler demultiplexing unit 211 may not output the separation index information (f demul_Tx#1 、f demul_Tx#2 、f demul_Tx#3 ).

[0212] (5) When the Doppler frequency indexes that correspond to (1), (2), and (3) above are included repeatedly, the Doppler demultiplexing unit 211 performs deduplication processing as described below, for example.

[0213] For example, the combinations of Doppler frequency indices that repeatedly meet the above (1) and (2) are (fd #p1 , fd #p2 , fd #p3 )、(fd #q1 , fd #q2 , fd #q3 ), the Doppler demultiplexing unit 211 compares the received power of the Doppler frequency index in each combination {for example, PowerFT(f b_cfar , fd #p1 )、PowerFT(f b_cfar , fd #p2 )、PowerFT(f b_cfar , fd #p3 )}、{PowerFT(f b_cfar , fd #q1 )、PowerFT(f b_cfar , fd #q2 )、PowerFT(f b_cfar , fd #q3)}, and extract the minimum received power from each combination. Next, the Doppler demultiplexing unit 211 uses, for example, a combination of Doppler frequency indices whose power difference between the powers that reach the minimum power of each combination is greater than a predetermined power threshold TPL.

[0214] For example, when the following equation is satisfied, the Doppler demultiplexing unit 211 uses the Doppler frequency index (fd #p1 , fd #p2 , fd #p3 ) and perform the processing of (1) above.

[0215] Min({PowerFT(f b_cfar , fd #p1 ), PowerFT(f b_cfar , fd #p2 ), PowerFT(f b_cfar , fd #p3 )})

[0216] -Min({PowerFT(f b_cfar , fd #q1 ), PowerFT(f b_cfar , fd #q2 ), PowerFT(f b_cfar , fd #q3 )})

[0217] >TPL (13)

[0218] For another example, when the following equation is satisfied, the Doppler demultiplexing unit 211 uses the Doppler frequency index (fd #q1 , fd #q2 , fd #q3 ) combination and perform the processing of (2) above.

[0219] Min({PowerFT(f b_cfar , fd #q1 ), PowerFT(f b_cfar , fd #q2 ), PowerFT(f b_cfar , fd #q3 )})

[0220] -Min({PowerFT(f b_cfar , fd #p1 ), PowerFT(f b_cfar , fd #p2 ), PowerFT(f b_cfar , fd #p3 )})

[0221] >TPL (14)

[0222] When equations (13) and (14) are not satisfied, the Doppler demultiplexing unit 211 performs the above-mentioned process (4) without using any combination of Doppler frequency indices. The Doppler demultiplexing unit 211 also performs the same repetition determination process for repetitive combinations other than (1) and (2).

[0223] Thereby, the Doppler multiplexing and demultiplexing unit 211 can separate the Doppler multiplexed signal.

[0224] (Transformation 2)

[0225] In the above embodiment, the phase rotation φ shown in equation (5) is used. n (m) is described as an example of a phase rotation corresponding to the Doppler shift amount added to the transmission signal. However, the phase rotation is not limited to the phase rotation φ shown in equation (5). n (m).

[0226] As another example, the n-th Doppler frequency shift unit 104 may add a Doppler frequency shift amount DOP different from that in the case of using equation (5) to the input m-th chirp signal (transmission signal). n The phase rotation φ of the following formula n (m).

[0227]

[0228] Here, dp n It is the component that makes the phase rotation into unequal intervals within the Doppler frequency range. For example, dp1, dp2, ..., dp Nt Yes-round(N C / Nt) / 2<dp n <round(N C In addition, in order to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 209, round (Nt) is introduced. C / Nt) items.

[0229] As an example, when Nt=2, Δφ0=0, φ0=0, A=1, dp1=0, dp2=π / 5 are added to equation (15), and N C The phase rotation φ when set to an even number n (m), the Doppler frequency shift amount is DOP1=0, DOP2=1 / (2Tr)+1 / (10Tr)=6 / (10Tr).

[0230] Figure 6 The graph shows changes in Doppler peak values ​​when Nt=2, DOP1=0, and DOP2=6 / (10Tr), with the horizontal axis representing the target Doppler frequency and the vertical axis representing the output of the Doppler analysis unit 209 (FFT).

[0231] <Target Doppler frequency is -1 / (10Tr)≦f d_TargetDoppler <1 / (2Tr)>

[0232] like Figure 6 As shown, the Doppler interval between the Doppler peak (solid line) generated when the reflected wave signal of the transmission signal from the transmitting antenna Tx#1 is received and the Doppler peak (dotted line) generated when the reflected wave signal of the transmission signal from the transmitting antenna Tx#2 is received is 4 / (10Tr).

[0233] In this case, Tx#2 contains an aliasing signal. Therefore, the Doppler demultiplexing unit 211 can determine that the higher Doppler peak among the Doppler peaks whose interval reaches 4 / (10Tr) is the reflected wave signal corresponding to the transmitting antenna Tx#1, and the lower Doppler peak is the reflected wave signal corresponding to the transmitting antenna Tx#2.

[0234] <Target Doppler frequency is -1 / (2Tr)≦f d_TargetDoppler <-1 / (10Tr)>

[0235] like Figure 6 As shown, the Doppler interval between the Doppler peak (solid line) generated when the reflected wave signal of the transmission signal from the transmitting antenna Tx#1 is received and the Doppler peak (dotted line) generated when the reflected wave signal of the transmission signal from the transmitting antenna Tx#2 is received is 6 / (10Tr).

[0236] In this case, neither of the transmission antennas Tx#1 and Tx#2 contains an aliasing signal. Therefore, the Doppler demultiplexing unit 211 can identify, for example, the reflected wave signals from the transmission antennas Tx#1 and Tx#2 starting from the Doppler peak with a low frequency.

[0237] Thus, in the second modification, each interval of the Doppler frequency shift amount of the transmitting antenna 105 is set so that the Doppler frequency range (in Figure 6 For example, -1 / (2Tr)≦f d The interval obtained by dividing by 1 / (2Tr)) plus the offset amount of DOP2=6 / (10Tr).

[0238] Thus, for example, Figure 6 As shown, the Doppler interval (6 / (10Tr)) in the case without aliasing is different from the Doppler interval (4 / (10Tr)) in the case with aliasing.

[0239] Therefore, in Figure 6 In the example shown, the target Doppler frequency range that does not cause ambiguity is, for example, -1 / (2Tr)≦f d_TargetDoppler <1 / (2Tr).

[0240] Thus, according to variation 2, compared with time division multiplexing or Doppler multiplexing, the target Doppler frequency range that does not cause ambiguity can be expanded to Nt times (for example, Figure 6 2 times in the middle).

[0241] (Transformation 3)

[0242] In Doppler multiplexing, when the reception levels of Doppler peaks of a plurality of targets are substantially equal and the intervals between Doppler peaks coincide with the intervals between Doppler shift amounts, the Doppler demultiplexing unit 211 may be unable to make a demultiplexing decision.

[0243] However, when the Doppler frequencies of the multiple targets are different, the relative moving speeds between the targets and the radar device 10 are different. Therefore, the radar device 10 continuously performs radar observation, and even if the reception levels of the Doppler peaks of the multiple targets in the positioning output of a certain radar device are approximately equal, and the intervals of the Doppler peaks are consistent with the intervals of the Doppler frequency shift amounts, there is still a high possibility that the distances between the multiple targets are different and measured in the subsequent positioning output of the radar device. Therefore, it is considered that the output of the multiple targets separated can be obtained in the subsequent positioning output of the radar device.

[0244] In variation 3, a case is described in which the Doppler shift amount is variably set for example per radar observation in order to more reliably separate multiple targets for the positioning output of the radar device 10. The radar observation unit may be, for example, a transmission frame unit or other units.

[0245] For example, in variation 3, equation (5) can be used as the equation corresponding to the Doppler frequency shift amount DOP n The phase rotation φ n (m).

[0246] The radar device 10 can variably set the interval of the Doppler shift amount for each transmission antenna 105 by variably setting the value of δ in equation (5) according to radar observation. For example, δ may be periodically changed in the order of 1, 2, 1, 2 according to radar observation.

[0247] In addition, equation (15) can be used as the value corresponding to the Doppler frequency shift DOP n The phase rotation φ n (m). For example, the radar device 10 converts the components dp1, dp2, ..., dp Nt By setting different values, the interval of the Doppler shift amount for each transmitting antenna 105 can be variably set. The components dp1, dp2, ..., dp Nt Make the phase rotation into unequal intervals.

[0248] According to variation 3, the intervals between Doppler peaks corresponding to a plurality of transmission antennas 105 for one target differ in each radar observation, and therefore, a plurality of targets can be easily separated.

[0249] (Transformation 4)

[0250] In variation 4, a case where the transmitting antenna of the radar device has a subarray structure will be described.

[0251] By combining several of the transmitting antennas and using them as a subarray, the beam width of the transmitting directional beam pattern can be narrowed, thereby improving the transmitting directional gain. As a result, the detectable angle range is narrowed, but the detectable distance range can be increased. In addition, by making the beam weight coefficient for generating the directional beam variable, the beam direction can be variably controlled.

[0252] Figure 7 4 is a block diagram showing a configuration example of a radar transmitter 100a according to a modification 4. Figure 7 In the Figure 1 The same reference numerals are used for the same operational structures of the radar transmitting unit 100 shown, and the description thereof will be omitted.

[0253] In addition, the basic structure of the radar receiving unit of the variant 4 is the same as Figure 1 The radar receiving unit 200 shown is universal, therefore, reference Figure 1 Provide explanation.

[0254] exist Figure 7 In, N DM Indicates the Doppler multiplexing number.

[0255] exist Figure 7 In the example, the output of each Doppler frequency shift unit 104 is composed of N SA Therefore, the number of transmit antennas 105 Nt=N SA ×N DM In addition, the subarray structure of the transmitting antenna 105 is not limited to Figure 7For example, between the Doppler frequency shift units 104, the number of transmission antennas included in the subarray for the output of each Doppler frequency shift unit 104 may not be the same. Here, N SA is an integer greater than 1. SA =1, and Figure 1 In addition, the Doppler frequency shift unit 104 performs the Doppler frequency shift on the transmission antenna 105 (eg, N SA The same Doppler frequency shift amount is added to the radar transmission signals transmitted by the transmitting antennas 105).

[0256] exist Figure 7 In the example, the beam weight generation unit 106 generates a beam weight that directs the main beam direction of the transmission beam toward a predetermined direction using the subarray. SA The subarray of transmitting antennas is spaced d apart from each other. SA The transmission beam direction when arranged in a straight line is represented by “θ TxBF In this case, the beam weight generation unit 106 generates the beam weight W as follows, for example: Tx (Index_TxSubArray, θ TxBF ).

[0257]

[0258] Here, Index_TxSubArray represents the element index of the subarray, Index_TxSubArray=1, ..., N SA In addition, λ represents the wavelength of the radar signal, d SA Indicates the subarray antenna spacing.

[0259] For example, the ndm-th beam weight multiplication unit 107 calculates the beam weight coefficient W input from the beam weight generation unit 106. Tx (Index_TxSubArray, θ TxBF ) is multiplied by the output from the ndm-th Doppler frequency shift unit 104. SA ×(ndm-1)+Index_TxSubArray} transmit antennas 105 transmit multiplied by the beam weight W Tx (Index_TxSubArray, θ TxBF Here, Index_TxSubArray = 1, ..., N SA , ndm=1、…、N DM .

[0260] Through the above operation, the radar transmitter 100a can transmit the transmission directional beam in a predetermined direction using the subarray in response to the output from the Doppler shifter 104. This can increase the transmission directional gain in the predetermined direction and expand the detectable distance range.

[0261] Furthermore, the radar transmitting unit 100 a can variably control the beam direction by variably setting a beam weight coefficient for generating a transmission directional beam.

[0262] In addition, the structure for performing sub-array transmission described in Variation 4 can also be similarly applied to other variations or implementations.

[0263] (Transformation 5)

[0264] In variation 5, for example, a method of reducing the influence of interference from a plurality of radar devices that overlap in the same frequency band or in a partial frequency band will be described.

[0265] Figure 8 1 is a block diagram showing a configuration example of a radar device 10b according to variation 5. Figure 8 In, with Figure 1 The same structure is assigned the same reference numeral and its description is omitted. Figure 8 The radar device 10b shown is structured as follows, that is, Figure 1 In the radar device 10 shown, a random code generating unit 108 and a random code multiplying unit 109 are newly added to the radar transmitting unit 100 b , and a random code multiplying unit 213 is newly added to the radar receiving unit 200 b .

[0266] exist Figure 8 In the example, the random code generation unit 108 generates a pseudo-random code sequence RCode={RC(1), RC(2), ..., RC(N LRC )}. For example, the pseudo random code may use a PN (pseudo random noise) code, an M sequence code, or a Gold code. In addition, the random code generator 108 generates a signal by adding a phase rotation of {π, -π} to the code element {1, -1} of the pseudo random code sequence, for example.

[0267] The code length N of the pseudo-random code sequence LRC N c In addition, the random code generator 108 changes the code element index of the pseudo-random code sequence so that RC_INDEX(m)=m at each transmission period m, and outputs the random code element RC(RC_INDEX(m)) of the pseudo-random code sequence RCode to the random code multiplier 109 and the random code multiplier 213 .

[0268] The random code multiplication unit 109 of the radar transmission unit 100 b multiplies the random code element RC(RC_INDEX) input from the random code generation unit 108 by the chirp signal cp(t) of the transmission period m. The random code multiplication unit 109 outputs a signal represented by RC(RC_INDEX(m))×cp(t) to each Doppler shift unit 104 .

[0269] The random code multiplication unit 213 of the radar receiving unit 200b multiplies the random code element RC (RC_INDEX) input from the random code generation unit 108 by the output signal RFT of the beat frequency analysis unit 208 in the transmission cycle m. z (f b , m). The random code multiplication unit 213 converts RC(RC_INDEX(m))×RFT z (f b The signal represented by ( , m) is output to the Doppler analysis unit 209. Here, z=1, ..., Na.

[0270] By the above-mentioned operation, even in the case of interference from multiple radar devices in the same frequency band or overlapping partial frequency bands, the radar device 10b can convert the interference signal into a pseudo-random signal by the random code multiplication unit 213 before the interference signal is input to the Doppler analysis unit 209. As a result, the output of the Doppler analysis unit 209 can obtain the effect of spreading the signal power of the interference wave in the Doppler frequency domain. For example, by multiplying the pseudo-random code sequence, the peak power of the interference wave can be reduced to 1 / N c Therefore, in the subsequent CFAR unit 210, the probability of erroneously detecting the peak of the interference wave can be greatly reduced.

[0271] (Transformation 6)

[0272] For example, when the phase rotation shown in equation (5) is used as the Doppler frequency shift amount DOP n In the case of DM More quantity (N DM +δ) The interval obtained by equally dividing the Doppler frequency range (ΔFD = round (N C / (N DM +δ)), the interval of ΔFD and the interval of (δ+1)ΔFD are used as the interval of the Doppler frequency shift amount.

[0273] Therefore, in the Doppler analysis unit 209 (for example, refer to Figure 1 ) in the output, each signal subjected to Doppler multiplexing is detected in an aliased manner at intervals of ΔFD in the Doppler frequency domain.

[0274] By using this property, the operations of the CFAR unit 210 and the Doppler demultiplexing unit 211 can be simplified as follows, for example.

[0275] [Operation of CFAR Unit 210]

[0276] The CFAR unit 210 detects the Doppler peak using a threshold value, for example, for a power addition value obtained by adding the reception powers of reflected wave signals in each range (for example, ΔFD) corresponding to each interval of the Doppler frequency shift amount added to the radar transmission signal in the Doppler frequency range that is the object of CFAR processing.

[0277] For example, the CFAR unit 210 calculates the power addition value after folding and adding the outputs from the Doppler analysis unit 209 of the first to Na-th signal processing units 206 within the range of ΔFD as shown in the following equation, and performs CFAR processing. s_shrink =-N c ,…,-N c +ΔFD-1.

[0278]

[0279] Thus, the Doppler frequency range to be processed by CFAR can be set to 1 / (N DM +δ), thereby reducing the amount of computation required for CFAR processing.

[0280] The CFAR unit 210 adaptively sets a threshold and indexes the distances where the received power is greater than the threshold. b_cfar , Doppler frequency index f shrink_cfar and received power information (PowerFT(f b_cfar , f shrink_cfar +ndm×ΔFD), ndm=1,...,N DM ) is output to the Doppler multiplexing separation unit 211.

[0281] [Operation of Doppler Demultiplexing Unit 211]

[0282] The Doppler demultiplexing unit 211 compares the received power information (PowerFT(f b_cfar , f shrink_cfar +ndm×ΔFD), ndm=1,...,N DM ), and the received power is based on the received levels of the upper NDM Doppler frequency indices, and the received power is based on the received levels of the upper N DMWhen the reception level differences of the δ Doppler frequency indices other than (δ+1)ΔFD are greatly different (for example, when they are equal to or greater than a predetermined threshold), the δ Doppler frequency indices with smaller reception levels are determined to be Doppler frequency indices included in the interval of (δ+1)ΔFD, and the upper N of the reception power are output. DM The Doppler frequency index is used as the separation index information of the Doppler multiplexed signal (f demul_Tx#1 ,…,f demul_Tx#NDM ).

[0283] In other words, in the order of received power from high to low, the N Doppler peaks detected in the Doppler frequency range correspond to DM The received level of the Doppler peaks corresponds to the above N DM When the difference in reception level of Doppler peaks other than N Doppler peaks (for example, δ Doppler peaks) is greater than the threshold, the Doppler demultiplexing unit 211 performs the multiplication of the received Doppler peaks based on the N DM Doppler peaks, and separate the Doppler multiplexed signals from the reflected wave signals. DM Alternatively, the difference in reception level can also be set to N DM The difference between the minimum value among the received levels and the maximum value among the δ received levels.

[0284] In addition, without limitation to the above processing, for example, the Doppler multiplexed signals may be separated from the reflected wave signals based on the relationship between the transmission antenna 105 and the Doppler frequency shift amount added to the radar transmission signal transmitted from each transmission antenna 105. For example, the Doppler frequency index information at intervals up to (δ+1)ΔFD and the upper N of the received power may be used. DM The relative position relationship of the Doppler frequency indexes determines the separation index information of the Doppler multiplexed signal. Figure 5 In the example, use N DM =3, δ=1, and the Doppler frequency shift amount using the phase rotation shown in equation (5) is added. Therefore, the target Doppler frequency includes the Doppler interval of ΔFD and the Doppler interval of (δ+1)ΔFD. It is known that Figure 5 The Doppler frequency index of the Doppler interval that reaches (δ+1)ΔFD is f demul_Tx#1 and f demul_Tx#3 , the Doppler multiplexing separation unit 211 can determine the separation index information of the Doppler multiplexing signal based on this. That is, in the output of the Doppler analysis unit 209, when the Doppler interval of (δ+1)ΔFD is in the range of 0 to 1 / (2T), the higher Doppler frequency index that reaches the Doppler interval of (δ+1)ΔFD is f demul_Tx#1 , the lower Doppler frequency index is f demul_Tx#3In addition, when the Doppler interval of (δ+1)ΔFD is in the range of -1 / (2T) to 0, f is generated in consideration of aliasing. demul_Tx#3 The higher Doppler frequency index of the Doppler interval reaching (δ+1)ΔFD is f demul_Tx#3 , the lower Doppler frequency index is f demul_Tx#1 . The upper N of the received power DM The remaining Doppler frequency index in the Doppler frequency index is f demul_Tx#2 The Doppler demultiplexing unit 211 can determine the Doppler shift amount DOP by using the result. n , so that the Doppler multiplexed signals can be separated.

[0285] Thus, in the Doppler demultiplexing unit 211, the received power information PowerFT(f b_cfar , f shrink_cfar +ndm×ΔFD), ndm=1,...,N DM Doppler multiplexing separation is performed by comparison processing, thereby reducing Doppler separation processing.

[0286] (Implementation Method 2)

[0287] In this embodiment, a case where Doppler multiplexing transmission and code division multiplexing (CDM: Code Division Multiplexing) transmission are used together will be described.

[0288] For example, in Embodiment 1 (for example, referring to Figure 1 ), if the Doppler multiplexing number increases, the probability of the Doppler frequency index where the interval of the Doppler frequency shift amount in the case of aliasing and the interval of the Doppler frequency shift amount in the case of no aliasing will overlap will increase in the processing of the Doppler multiplexing separation unit 211. Therefore, depending on the propagation environment with many reflecting objects, the Doppler multiplexing number has an appropriate range, and there is a Doppler multiplexing number that reaches the upper limit.

[0289] Therefore, the present embodiment describes a structure in which the structure for performing Doppler multiplexing described in Embodiment 1 is further combined with code multiplexing, and the Doppler region and the code region can be used to increase the multiplexing number even when the number of transmitting antennas (for example, the Doppler multiplexing number) increases.

[0290] Fig. 9 is a block diagram showing a configuration example of a radar device 10c according to this embodiment. Fig. 9 In the embodiment 1 (for example, Figure 1 ) The same structure is assigned the same reference numeral and its description is omitted. For example, Fig. 9 The radar device 10c shown is relative to Figure 1 In the radar device 10 shown, an orthogonal code generating unit 301 and an orthogonal code multiplying unit 302 are newly added to the radar transmitting unit 100 c , and an output switching unit 401 and a code multiplexing separation unit 402 are newly added to the radar receiving unit 200 c .

[0291] Below, the Doppler multiplexing number is set to N DM , set the code multiplexing number to N CM , and the number of transmitting antennas 105 used Nt=N DM ×N CM The situation of Doppler multiplexing number and code multiplexing number.

[0292] [Configuration Example of Radar Transmitter 100c]

[0293] In the radar transmitter 100c, the orthogonal code generator 301 generates N orthogonal codes of length Loc. CM Orthogonal code sequence Code ncm ={OC ncm (1) OC ncm (2),…,OC ncm (L oc )}. Here, ncm=1, ..., N CM .

[0294] For example, the orthogonal code generation unit 301 generates orthogonal code sequences Code1 to Code2 according to the radar transmission period (Tr). Ncm The orthogonal code element index OC_INDEX of the element is set cyclically and variably, and the orthogonal code sequence Code1 to the orthogonal code sequence Code Ncm Element OC1 (OC_INDEX) ~ element OC Ncm (OC_INDEX) is output to the 1st to Ntth orthogonal code multiplication units 302. In addition, the orthogonal code generation unit 301 outputs the orthogonal code element index OC_INDEX to the output switching unit 401 for each radar transmission cycle (Tr).

[0295] Here, OC_INDEX = 1, 2, ..., Loc. For example, in the mth transmission cycle, OC_INDEX = MOD(m-1, L oc )+1. Here, MOD(x, y) is a modulus operator, and is a function that outputs a remainder after dividing x by y.

[0296] In addition, for example, codes that are not correlated with each other are used in the orthogonal code sequence generated by the orthogonal code generation unit 301. For example, Walsh-Hadamard code can be used in the orthogonal code sequence.

[0297] As an example, when NCM=2, the orthogonal code length Loc of the Walsh-Hadamard code is 2, and the orthogonal code generation unit 301 generates an orthogonal code sequence of OC1={1, 1} and OC2={1, -1}.

[0298] In addition, as another example, in N CM When =4, the orthogonal code length Loc=4, and the orthogonal code generating unit 301 generates the orthogonal code sequences OC1={1,1,1,1}, OC2={1,-1,1,-1}, OC3={1,1,-1,-1}, OC4={1,-1,-1,1}.

[0299] Furthermore, the elements constituting the orthogonal code sequence are not limited to real numbers, but may include complex numbers, or may be orthogonal codes using phase rotation as shown in the following equation.

[0300]

[0301] For formula (19), for example, when Nt=3, the orthogonal code length Loc=Nt, and the orthogonal code generation unit 301 generates orthogonal code sequences of OC1={1, 1, 1}, OC2={1, exp(j2π / 3), exp(j4π / 3)}, and OC3={1, exp(-j2π / 3), exp(-j4π / 3)}.

[0302] In addition, as another example, when Nt=4, the orthogonal code length Loc=Nt, and the orthogonal code generation unit 301 generates orthogonal code sequences of OC1={1, 1, 1, 1}, OC2={1, j, -1, -j}, OC3={1, -1, 1, -1}, and OC4={1, -j, -1, j}.

[0303] For example, when the Doppler multiplexing number is set to N DM In the case of Fig. 9 The radar transmitting unit 100c shown includes N DM Doppler frequency shift units 104-1 to 104-N DM In addition, the radar transmitter 100c includes the same number of N as the Doppler frequency shift unit 104. DM The orthogonal code multiplication unit 302 is provided.

[0304] Each Doppler frequency shift unit 104 adds a predetermined phase rotation φ to the chirp signal input from the radar transmission signal generation unit 101. ndm With additional Doppler shift DOP ndm , and outputs the chirped signal with phase rotation added to the corresponding orthogonal code multiplication section 302. Here, ndm=1, ..., N DM .

[0305] Each orthogonal code multiplication section 302 includes a number corresponding to the number of code multiplexing N CM The orthogonal code multiplication unit 302 converts N CM orthogonal code sequences Code1, Code2, ..., Code Ncm multiply the output of Doppler frequency shift unit 104 by N CM The signal is output to the transmitting antenna 105.

[0306] Through the operation of the Doppler frequency shift unit 104 and the orthogonal code multiplication unit 302 as described above, the following signal is output from the nth transmission antenna 105 among the Nt transmission antennas 105. The signal is obtained by floor[(n-1) / N CM ]+1 Doppler frequency shift unit 104 adds a Doppler frequency shift DOP to the output of the radar transmission signal generation unit 101 floor[(n-1) / NCM]+1 , and further on the floor[(n-1) / N CM ]+1 orthogonal code multiplication unit 302 multiplies mod(n-1, N CM )+1 orthogonal code Code mod(n-1，NCM)+1 signal.

[0307] For example, the transmitting antenna 105 with Nt=6 is described, and the Doppler multiplexing number is set to N DM =3, and set the code multiplexing number to N CM =2. In this case, 3 (=N DM ) The Doppler frequency shift unit 104 adds Doppler frequency shift amounts DOP1, DOP2, and DOP3 to the chirp signal. DM ) The orthogonal code multiplication unit 302 converts 2(=N CM ) orthogonal code sequence Code1 and orthogonal code sequence Code2 are multiplied by the output of the Doppler frequency shift unit 104.

[0308] In this case, for example, the following signal is output from the first transmission antenna 105 at the transmission period Tr.

[0309] OC1(1)Λ1(1)cp(t),OC1(2)Λ1(1)cp(t),OC1(1)Λ1(2)cp(t),OC1(2)Λ1(2)cp(t),OC1(1)Λ1(3)cp(t),OC1(2)Λ1(3)cp(t),... (20)

[0311] Here, cp(t) represents the chirp signal per transmission period Tr. In addition, the Doppler frequency shift unit 104 adds a phase rotation φ ndm The multiplication value when (m) is recorded as "Λndm (m)”.

[0312] Λ ndm (m) = exp[jφ ndm (m)] (21)

[0313] Similarly, the following signal is output from the second transmission antenna 105 at the transmission period Tr.

[0314] OC2(1)Λ1(1)cp(t),OC2(2)Λ1(1)cp(t),OC2(1)Λ1(2)cp(t),OC2(2)Λ1(2)cp(t),OC2(1)Λ1(3)cp(t),OC2(2)Λ1(3)cp(t),... (twenty two)

[0316] Similarly, the following signal is output from the third transmission antenna 105 at the transmission period Tr.

[0317] OC1(1)Λ2(1)cp(t),OC1(2)Λ2(1)cp(t),OC1(1)Λ2(2)cp(t),OC1(2)Λ2(2)cp(t),OC1(1)Λ2(3)cp(t),OC1(2)Λ2(3)cp(t),... (twenty three)

[0319] Similarly, the fourth transmitting antenna 105 outputs the following signal at a transmission period Tr.

[0320] OC2(1)Λ2(1)cp(t),OC2(2)Λ2(1)cp(t),OC2(1)Λ2(2)cp(t),OC2(2)Λ2(2)cp(t),OC2(1)Λ2(3)cp(t),OC2(2)Λ2(3)cp(t),... (twenty four)

[0322] Similarly, the fifth transmitting antenna 105 outputs the following signal at the transmission period Tr.

[0323] OC1(1)Λ3(1)cp(t),OC1(2)Λ3(1)cp(t),OC1(1)Λ3(2)cp(t),OC1(2)Λ3(2)cp(t),OC1(1)Λ3(3)cp(t),OC1(2)Λ3(3)cp(t),... (25)

[0325] Similarly, the sixth transmitting antenna 105 outputs the following signal at the transmission period Tr.

[0326] OC2(1)Λ3(1)cp(t),OC2(2)Λ3(1)cp(t),OC2(1)Λ3(2)cp(t),OC2(2)Λ3(2)cp(t),OC2(1)Λ3(3)cp(t),OC2(2)Λ3(3)cp(t),... (26)

[0328] The radar transmitter 100c transmits the signal so that the number of chirped pulse transmissions reaches an integral multiple (Ncode times) of the orthogonal code length Loc. C =L OC ×Ncode.

[0329] In addition, the configuration of the radar transmitter in the radar device 10c is not limited to Fig. 9 For example, it can also be the following structure, that is, Fig.10 As shown in the radar transmitter 100d, Fig. 9 The phase rotation of the Doppler frequency shift unit 104 is multiplied by the code in the orthogonal code multiplication unit 302. Fig.10 The structure of the radar receiving unit 200d shown is similar to Fig. 9 The structure of the radar receiving unit 200c shown is the same.

[0330] For example, in Fig.10 In the example, the Doppler frequency shift and orthogonal code generation unit 303 generates the multiplication coefficients of the Doppler frequency shift and orthogonal coding for each transmission period Tr. For example, the Doppler frequency shift and orthogonal code generation unit 303 outputs the multiplication coefficients for adding the floor[(n-1) / Nth]th transmission antenna to the multiplication unit 304 connected to the nth transmission antenna among the Nt transmission antennas 105. CM ]+1 Doppler shift DOP floor[(n-1) / NCM]+1 The phase rotation of mod(n-1, N CM )+1 orthogonal code Code mod(n-1，NCM)+1 The multiplication factor obtained by multiplication.

[0331] The multiplication unit 304 multiplies the output signal (chirp signal) of the radar transmission signal generation unit 101 by the multiplication coefficient input from the Doppler shift and orthogonal code generation unit 303 .

[0332] [Configuration Example of Radar Receiving Unit 200c]

[0333] Next, explain Fig. 9 The structure example of the radar receiving unit 200c shown.

[0334] In the z-th signal processing unit 206c, the output switching unit 401 selectively switches the output of the beat frequency analysis unit 208 of each transmission period Tr to Loc Doppler analysis units, i.e., the Doppler analysis units 209-1 to 209-L, based on the orthogonal code element index OC_INDEX input from the orthogonal code generation unit 301. OC That is, the output switching unit 401 selects the OC_INDEX-th Doppler analysis unit 209 in the m-th transmission cycle Tr.

[0335] The z-th signal processing unit 206 c includes Loc Doppler analysis units 209 .

[0336] By the output switching unit 401, the transmission cycle (L OC ×Tr) inputs the data to the nol-th Doppler analysis unit 209 in the z-th signal processing unit 206c. Therefore, the nol-th Doppler analysis unit 209 uses N C Doppler analysis is performed on the data of Ncode transmission cycles in the Ncode transmission cycles. Here, nol = 1, ..., L OC .

[0337] When Ncode is a power of 2, the Doppler analysis unit 209 can apply FFT (Fast Fourier Transform) processing as shown in the following equation.

[0338]

[0339] Here, the FFT size is Ncode, and the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1 / (2Loc×Tr). 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.

[0340] In addition, when Ncode is not a power of 2, for example, FFT processing can be performed by including zero-padded data as an FFT size that is a power of 2. In addition, the Doppler analysis unit 209 can also multiply the window function coefficient such as the Han window or the Hamming window during FFT processing, and by applying the window function, the side lobes generated around the beat frequency peak can be suppressed.

[0341] The code multiplexing separation unit 402 separates signals that have been multiplexed and transmitted using orthogonal codes.

[0342] For example, the code multiplexing separation unit 402 performs the following operation on the orthogonal code element OC used in transmission: ncm Perform complex conjugation (indicated by *), multiply by the Doppler analysis result of each orthogonal code element index OC_INDEX and add them. Thus, the orthogonal code Code ncm Here, ncm = 1, ..., N CM .

[0343]

[0344] The CFAR unit 210c performs CFAR processing (in other words, adaptive threshold determination) using the output of the code multiplexing separation unit 402, and extracts the distance index f that gives the peak signal. b_cfar and the Doppler frequency index f s_cfar .

[0345] The CFAR unit 210c adds the power of the output of the code multiplexing separation unit 402 in the following manner, and performs a two-dimensional CFAR process including a distance axis and a Doppler frequency axis (equivalent to a relative speed) or a CFAR process combined with a one-dimensional CFAR process. For example, the process disclosed in non-patent document 2 can be applied to the two-dimensional CFAR process or the CFAR process combined with the one-dimensional CFAR process.

[0346]

[0347] The CFAR unit 210c adaptively sets a threshold and indexes the distances where the received power is greater than the threshold. b_cfar , Doppler frequency index f s_cfar and receiving power information PowerFT(f b_cfar , f s_cfar ) is output to the Doppler multiplexing separation unit 211c.

[0348] In addition, Fig. 9 , the structure in which the CFAR unit 210c uses the output of the code multiplexing separation unit 402 is shown, but the present invention is not limited to this. As another structure, the CFAR unit 210c may also use the output of the Doppler analysis unit 209 to perform CFAR processing. In this case, the CFAR unit 210c may, for example, perform a two-dimensional CFAR processing including a distance axis and a Doppler frequency axis (equivalent to a relative speed) or a CFAR processing combined with a one-dimensional CFAR processing by adding the power of the output of the Doppler analysis unit 209 in the following manner. With regard to the two-dimensional CFAR processing or the CFAR processing combined with the one-dimensional CFAR processing, for example, the processing disclosed in non-patent document 2 may be applied.

[0349]

[0350] In addition, when the CFAR unit 210c performs CFAR processing using the output of the Doppler analysis unit 209, the code multiplexing separation unit 402 may use the distance index f that makes the received power greater than the threshold value indicated by the CFAR unit 210c. b_cfar , Doppler frequency index f s_cfar And the received power information PowerFT(f b_cfar , f s_cfar ) performs the code multiplexing separation operation, thereby being limited to the distance index f where the received power indicated by the CFAR unit 210c is greater than the threshold value b_cfar , Doppler frequency index f s_cfar The code multiplexing and separation operation is performed, so the amount of processing by the code multiplexing and separation unit 402 can be reduced.

[0351] The Doppler demultiplexing unit 211c uses the information input from the CFAR unit 210c (for example, the distance index f b_cfar , Doppler frequency index f s_cfar and receiving power information PowerFT(f b_cfar , f s_cfar )), using the output from each code multiplexing separation unit 402, the transmission signal sent from each transmission antenna 105 is separated.

[0352] The operation of the Doppler demultiplexing unit 211 c will be described below together with the operation of the Doppler frequency shift unit 104 .

[0353] 1st to Nth DM The Doppler frequency shift units 104 add different Doppler frequency shift amounts DOP1, DOP2, ..., DOP to the input chirp signal. NDM Here, as in the first embodiment, the Doppler shift amounts DOP1, DOP2, ..., DOP NDM For example, each interval (Doppler frequency shift interval) is not a value obtained by dividing the Doppler frequency range where aliasing does not occur at equal intervals, but an interval obtained by dividing it at unequal intervals (for example, at least one Doppler interval is different). ndm Each interval of can be set to the number Nt of the plurality of transmitting antennas 105 divided by the code multiplexing number N CM The resulting value (in other words, the Doppler multiplexing number N DM ) plus a value greater than 1 (e.g., δ), and the Doppler frequency range (e.g., -1 / (2L oc ×Tr)≦f d <1 / (2L oc ×Tr)) is the interval obtained by segmentation.

[0354] In the first embodiment, the case where the Doppler multiplexing number is equal to the number of transmission antennas Nt (that is, Nt=N DM ). In contrast, in the present embodiment, since code multiplexing is used together with Doppler multiplexing, the Doppler multiplexing number N DM The multiplexing number becomes smaller than the number of transmission antennas Nt (for example, Nt>N DM ). Thus, for example, the Doppler frequency shift amount DOP ndm Each interval of can be set to divide the Doppler frequency range where aliasing does not occur by a number less than the number Nt of the transmitting antennas 105 (for example, -1 / (2L oc ×Tr)≦f d <1 / (2L oc ×Tr)) obtained.

[0355] Therefore, in this embodiment, the Doppler shift amount DOP ndm , using N DM The equation obtained by replacing Nt in equation (5) or equation (15) used in Embodiment 1. In addition, in order to make the phase rotation multiplied by the transmission period (L) of the orthogonal code sequence OC ×Tr), between the transmission cycles of the orthogonal code length Loc (L OC ×Tr), repeatedly outputs the same phase rotation φ ndm (m).

[0356] That is, the ndm-th Doppler frequency shift unit 104 adds a phase rotation φ as shown in the following equation to the input m-th chirp signal. ndm (m) to achieve different Doppler frequency shift DOP ndm .

[0357]

[0358] Here, A is a coefficient that gives a positive or negative polarity of 1 or -1. In addition, δ is a positive number greater than 1. In addition, φ0 is an initial phase, and Δφ0 is a reference Doppler frequency shift phase. In addition, round(x) is a round function that outputs an integer value obtained by rounding off a real value x. In addition, floor[x] is an operator that outputs the nearest integer less than the real number x. In addition, in order to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 209, round(Ncode / (N DM +1))'s item.

[0359] As described above, in Embodiment 1, the Doppler multiplexing number N is described. DM In the present embodiment, the Doppler multiplexing number N is equal to the number of transmitting antennas Nt. DMLess than the number of transmitting antennas Nt. In the Doppler demultiplexing unit 211c, N DM Instead of the Doppler demultiplexing unit 211 of the first embodiment (for example, see Figure 1 )The parameter Nt used.

[0360] In addition, the Doppler analysis unit 209 (for example, see Figure 1 ) is N in the first embodiment. C Therefore, in the Doppler demultiplexing unit 211c, the parameter N used in the Doppler demultiplexing unit 211 of the first embodiment is replaced by Ncode. C .

[0361] The sampling period of FFT in the Doppler analysis unit 209 is Tr in the first embodiment, but is L in the present embodiment. OC Therefore, in the Doppler demultiplexing unit 211c, L OC The parameter Tr used by the Doppler demultiplexing unit 211 in the first embodiment is replaced by ×Tr.

[0362] As an example, in N DM =2, Δφ0=0, φ0=0, δ=1, and Ncode is set to a multiple of 3 and a phase rotation φ is added ndm (m) (for example, in the case of equation (31)), the Doppler shift amount is DOP1=0 when A=1, and DOP2=1 / (3L OC ×Tr), when A=-1, DOP1=0, DOP2=-1 / (3L OC ×Tr).

[0363] The Doppler demultiplexing unit 211c uses the peak value (distance index f) of the received power greater than the threshold value input from the CFAR unit 210c. b_cfar , Doppler frequency index f s_cfar ), separate the Doppler multiplexed signal.

[0364] For example, the Doppler demultiplexing unit 211c calculates the distance index f b_cfar The same multiple Doppler frequency index f s_cfar , it is determined that it corresponds to Doppler multiplexing transmission signal #1 to Doppler multiplexing transmission signal #N DM The Doppler multiplexing separation unit 211c separates and outputs the reflected wave signals of the determined Doppler multiplexing transmission signals.

[0365] Next, the distance index f is described. b_cfar The same multiple Doppler frequency index f s_cfarThere are Ns actions. For example, f s_cfar ∈{fd #1 、fd #2 …、fd #Ns}.

[0366] For example, the Doppler demultiplexing unit 211c calculates the distance index f b_cfar The same multiple Doppler frequency index f s_cfar ∈{fd #1 、fd #2 …、fd #Ns}, calculate the Doppler index interval.

[0367] Here, according to the Doppler frequency shift DOP ndm , for a target Doppler frequency f d_TargetDoppler In the Doppler spectrum obtained by the Doppler analysis in the Doppler analysis unit, N DM (where N DM <Nt) Doppler peaks. According to the difference between the phase rotation φ1(m) and the phase rotation φ2(m) shown in the following equation, the Doppler index interval corresponding to the Doppler interval between the Doppler peaks is round(Ncode / (N DM +1)). In addition, when an aliasing signal is included, the Doppler index interval corresponding to the Doppler interval between Doppler peaks is N c -round(Ncode / (N DM +1)).

[0368]

[0369] Next, the Doppler demultiplexing unit 211c searches for an index interval round (Ncode / (N DM +1)) or an index interval N corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included. c -round(Ncode / (N DM +1))Consistent Doppler frequency index.

[0370] The Doppler demultiplexing unit 211c performs the following processing based on the above-mentioned search result.

[0371] (1) There is an index interval round (Ncode / (Ncode) corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is not included DM +1)), the Doppler demultiplexing unit 211c outputs an index pair of these Doppler frequency indices (for example, represented by "fd#p , fd #q ”) as the separation index information of the Doppler multiplexed signal (f demul_DS#1 、f demul_DS#2 ).

[0372] Here, when the Doppler frequency shift amount is in the relationship of DOP1<DOP2, the Doppler demultiplexing unit 211c converts fd #p 、fd #q The larger one of fd is determined as the output (DS#2) of the second Doppler frequency shift unit 104, and the smaller one is determined as the output (DS#1) of the first Doppler frequency shift unit 104. On the other hand, when the Doppler frequency shift amount is in the relationship of DOP1>DOP2, the Doppler demultiplexing unit 211c determines fd #p 、fd #q The larger one of the two is determined as the output of the first Doppler frequency shift unit 104 (DS#1), and the smaller one is determined as the output of the second Doppler frequency shift unit 104 (DS#2).

[0373] (2) When there is an index interval N corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included c -round(Ncode / (N DM +1)), the Doppler demultiplexing unit 211c outputs an index pair of these Doppler frequency indices (for example, fd #p , fd #q ) as the separation index information of the Doppler multiplexed signal (f demul_DS#1 、f demul_DS#2 ).

[0374] Here, when the Doppler frequency shift amount is in the relationship of DOP1<DOP2, the Doppler demultiplexing unit 211c converts fd #p 、fd #q The larger one of fd is determined as the output (DS#1) of the first Doppler frequency shift unit 104, and the smaller one is determined as the output (DS#2) of the second Doppler frequency shift unit 104. On the other hand, when the Doppler frequency shift amount is in the relationship of DOP1>DOP2, the Doppler demultiplexing unit 211c determines fd #p 、fd #q The larger one of the two is determined as the output of the second Doppler frequency shift unit 104 (DS#2), and the smaller one is determined as the output of the first Doppler frequency shift unit 104 (DS#1).

[0375] (3) The index interval round(Ncode / (Ncode) is equal to the interval of the Doppler frequency shift amount when no aliasing signal is included. DM+1)) and the index interval N corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included. c -round(Ncode / (N DM +1)), the Doppler demultiplexing unit 211c determines that the generated Doppler peak is a noise component. In this case, the Doppler demultiplexing unit 211c may not output the separation index information (f demul_Tx#1 、f demul_Tx#2 ).

[0376] (4) When there is an index interval round(Ncode / (Ncode) corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is not included DM +1)) and is consistent with the index interval N corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is included c -round(Ncode / (N DM +1)), when the Doppler frequency indexes match, the Doppler demultiplexing unit 211c performs deduplication processing as described below, for example.

[0377] For example, the index interval corresponding to the interval of the Doppler frequency shift amount when the aliasing signal is not included is rounded (Ncode / (N DM +1)) is represented by the index pair of Doppler frequency indices that are consistent with each other as (fd #p , fd #q1 ). In addition, the index interval N corresponding to the interval of the Doppler frequency shift amount in the case of including the aliasing signal is c -round(Ncode / (N DM +1)) is represented by the index pair of Doppler frequency indices that are consistent with each other as (fd #p , fd #q2 ).

[0378] The Doppler demultiplexing unit 211c calculates, for example, an index pair of Doppler frequency indices (fd #p , fd #q1 )'s power differential |PowerFT(f b_cfar , fd #q1 )-PowerFT(f b_cfar , fd #p )|, and the index pair of Doppler frequency index (fd #p , fd #q2 )'s power differential |PowerFT(f b_cfar , fd #q2 )-PowerFT(f b_cfar , fd #pWhen the power (in other words, the difference) between these power differences is greater than a predetermined power threshold value TPL, the Doppler demultiplexing unit 211c adopts an index pair having a smaller power difference between the index pairs of Doppler frequency indices.

[0379] For example, when the following equation is satisfied, the Doppler demultiplexing unit 211c uses the index pair (fd #p , fd #q2 ), and perform the processing of (2) above.

[0380] |PowerFT(f b_cfar , fd #q1 )-PowerFT(f b_cfar , fd #p )|-|PowerFT(f b_cfar , fd #q2 )-PowerFT(f b_cfar , fd #p )|>TPL (33)

[0381] For another example, when the following equation is satisfied, the Doppler demultiplexing unit 211c uses the index pair (fd #p , fd #q1 ) and perform the processing of (1) above.

[0382] |PowerFT(f b_cfar , fd #q2 )-PowerFT(f b_cfar , fd #p )|-|PowerFT(f b_cfar , fd #q1 )-PowerFT(f b_cfar , fd #p )|>TPL (34)

[0383] When equations (33) and (34) are not satisfied, the Doppler demultiplexing unit 211c performs the above-mentioned process (3) without using any index pair of Doppler frequency indices.

[0384] Thereby, the Doppler multiplexing separation unit 211c can separate the Doppler multiplexed signal.

[0385] In this embodiment, the phase rotation φ of the following formula can also be used: ndm (m) is used to replace formula (31).

[0386]

[0387] Here, dp ndmIt is the component that makes the phase rotation into unequal intervals within the Doppler frequency range. For example, dp1, dp2, ..., dp DM Yes-round(N C / N DM ) / 2<dp n <round(N C / N DM ) / 2, and not all of them are the same value, and at least one component contains different values. In addition, in order to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 209, round(N C / N DM ) item.

[0388] The above is a description of an operation example of the Doppler demultiplexing unit 211 c.

[0389] exist Fig. 9 In the example, the direction estimation unit 212c uses the information input from the Doppler demultiplexing unit 211c (for example, the distance index f b_cfar and separate index information (f demul_DS#1 、f demul_DS#2 ,…,f demul_DS#NDM ), and perform target direction estimation.

[0390] For example, the direction estimation unit 212c extracts the direction corresponding to the distance index f from the output of each code multiplexing separation unit 402. b_cfar and separate index information (f demul_DS#1 、f demul_DS#2 ,…,f demul_DS#NDM ) output, generating a virtual receive array correlation vector h(f b_cfar 、f demul_DSx#1 、f demul_DSx#2 ,…,f demul_DS#NDM ) and perform direction estimation processing.

[0391] Virtual receiving array correlation vector h(f b_cfar 、f demul_DSx#1 、f demul_DSx#2 ,…,f demul_DS#NDM ) contains the product of the number of transmitting antennas Nt and the number of receiving antennas Na, that is, Nt×Na elements. The virtual receiving array correlation vector h(f b_cfar 、f demul_DSx#1 、f demul_DSx#2 ,…,f demul_DS#NDM ) is used for the following process, which estimates the direction of the reflected wave signal from the target based on the phase difference between each receiving antenna 202. Here, z=1, ..., Na. In addition, the direction estimation method can apply the same method as the first embodiment, for example.

[0392]

[0393] In formula (36), h cal[b] b is an array correction value for correcting the phase deviation and amplitude deviation between the transmission array antennas and the reception array antennas. b = 1, ..., (Nt × Na).

[0394] As described above, in this embodiment, by using a structure that uses Doppler multiplexing and code multiplexing together, in addition to the same effects as embodiment 1, the number of signals that are multiplexed and transmitted simultaneously can be increased, thereby being adaptable to a MIMO array structure with an increased number of transmitting antennas.

[0395] In the above description, the Doppler multiplexing number is assumed to be N. DM , set the code multiplexing number to N CM , and the number of transmitting antennas 105 used is Nt=N DM ×N CM The Doppler multiplexing number and code multiplexing number of N are not limited to this. DM For example, the orthogonal code generation unit 301 generates an orthogonal code length L oc N CM Orthogonal code sequence Code ncm Each orthogonal code multiplication unit 302 may include a code multiplexing number N CM The orthogonal code multiplication unit 302 may also use the following structure, that is, N CM orthogonal code sequences Code1, Code2, ..., Code Ncm N CM The following orthogonal code sequences are multiplied by the output of the Doppler frequency shift unit 104, and N CM The following signals are output to the transmitting antenna 105.

[0396] For example, the transmission antenna 105 with Nt=5 is described, and the Doppler multiplexing number is set to N DM =3, and the code multiplexing number N CM In this case, 3 (=N DM ) The Doppler frequency shift unit 104 adds Doppler frequency shift amounts DOP1, DOP2, and DOP3 to the chirp signal. In addition, the following configuration is used, that is, 3 (=N DM ) The orthogonal code multiplication unit 302 converts 2(=N CM ) orthogonal code sequences Code1 and Code2 are multiplied by the outputs of Doppler frequency shift units 104-1 and 104-2, and 1(≦N CM) orthogonal code sequence Code1 is multiplied by the output of Doppler frequency shift unit 104-3. In other words, between radar transmission signals transmitted from multiple transmission antennas 105, the code multiplexing number N applied to the radar transmission signal is CM In the processing of the radar receiving unit 200c in this case, in addition to not having to perform code multiplexing separation on the signal transmitted by multiplying the orthogonal code sequence Code2 by the output of the Doppler frequency shift unit 104-3, the processing described so far (Nt=6 transmitting antennas 105, the Doppler multiplexing number is set to N) can be used. DM =3, and set the code multiplexing number to N CM =2) to separate the transmission signal from the transmission antenna of Nt=5. DM Doppler multiplexing signals can be increased by using different code multiplexing numbers instead of the same code multiplexing number. DM For example, when the Doppler multiplexing number is set to N DM =3, and the code multiplexing number N CM When the number of transmitting antennas Nt is set to 2 or less, the number of transmitting antennas Nt (in other words, the number of simultaneous multiplexing transmissions) can be used in the range of 4, 5, or 6. If expressed in a more general way, Nt can be used in the range of 4, 5, or 6. DM +1≦Nt≦N DM ×N CM The number of transmitting antennas Nt (in other words, the number of simultaneous multiplexed transmissions) is applied within the range.

[0397] Alternatively, the orthogonal code multiplication unit 302 may use the following configuration, that is, CM orthogonal code sequences Code1, Code2, ..., Code NcmThe radar receiving unit 200c multiplies the output of at least one of the outputs of the plurality of Doppler shift units 104 by one orthogonal code sequence, and outputs the result to the transmitting antenna 105. As described above, by using a structure in which a signal without code multiplexing is output from the transmitting antenna for the output of at least one of the outputs of the plurality of Doppler shift units 104, the radar receiving unit 200c can detect whether the output of the Doppler analyzing unit 209 includes a Doppler aliasing signal. That is, although the maximum Doppler frequency without aliasing derived by the Doppler analysis unit 209 based on the sampling theorem is ±1 / (2Loc×Tr), as described above, by using the output of at least one Doppler frequency shift unit 104 among the outputs of multiple Doppler frequency shift units 104, a structure that outputs a signal from a transmitting antenna without using code multiplexing can be used to make the maximum Doppler frequency without aliasing derived by the Doppler analysis unit 209 based on the sampling theorem as ±1 / (2×Tr), thereby achieving the following effect, namely, expanding the Doppler frequency range that can be detected without ambiguity.

[0398] Furthermore, when Doppler multiplexing and code multiplexing are used together, the pseudo-random code sequence may be multiplied by the transmission signal in the same manner as in variation 5 of embodiment 1. The code length N of the pseudo-random code sequence LRC It can also be set to less than Ncode, and according to the code reuse period, RC_INDEX(m)=floor[(m-1) / N LOC ]+1 to change the random code element index and output the random code element RC (RC_INDEX(m)) of the pseudo-random code sequence RCode.

[0399] (Implementation 3)

[0400] In this embodiment, a case where Doppler multiplexing transmission and time division multiplexing (TDM: Time Division Multiplexing) transmission are used together will be described.

[0401] For example, in embodiment 1 (for example, refer to Figure 1 ), if the Doppler multiplexing number increases, the probability of the Doppler frequency index where the interval of the Doppler frequency shift amount in the case of aliasing and the interval of the Doppler frequency shift amount in the case of no aliasing will overlap will increase in the processing of the Doppler multiplexing separation unit 211. Therefore, depending on the propagation environment with many reflecting objects, the Doppler multiplexing number has an appropriate range, and there is a Doppler multiplexing number that reaches the upper limit.

[0402] Therefore, the present embodiment describes a structure that further uses time division multiplexing together with the structure for performing Doppler multiplexing described in Embodiment 1, and that can increase the multiplexing number using the Doppler region and the time domain even when the number of transmitting antennas (for example, the Doppler multiplexing number) increases.

[0403] Fig.11 is a block diagram showing a configuration example of a radar device 10e according to this embodiment. Fig.11 In the embodiment 1 (for example, Figure 1 ) The same structure is assigned the same reference numeral and its description is omitted. For example, Fig.11 The radar device 10e shown is relative to Figure 1 In the radar device 10 shown, a transmission switching control unit 501 and a transmission switching unit 502 are newly added to the radar transmitting unit 100e, and an output switching unit 601 is newly added to the radar receiving unit 200e.

[0404] Below, the Doppler multiplexing number is set to N DM , set the time division multiplexing number to N TM , and the number of transmitting antennas 105 used Nt=N DM ×N TM The situation of Doppler multiplexing number and time division multiplexing number.

[0405] [Configuration Example of Radar Transmitter 100e]

[0406] The transmission switching control unit 501 generates a time division multiplexing index TM_INDEX for instructing switching of the transmission antenna 105 used in time multiplexing according to the radar transmission cycle (Tr), and outputs the time division multiplexing index TM_INDEX to the transmission switching unit 502 and the output switching unit 601 .

[0407] Here, TM_INDEX = 1, 2, ..., N TM For example, in the mth transmission cycle, TM_INDEX = MOD(m-1, N TM )+1. Here, MOD(x, y) is a modulus operator, and is a function that outputs a remainder after dividing x by y.

[0408] For example, when the Doppler multiplexing number is set to N DM In the case of Fig.11 The radar transmitting unit 100e shown includes N DM Doppler frequency shift units 104-1 to 104-N DM In addition, the radar transmitter 100e includes the same number of N as the Doppler frequency shift unit 104. DM A transmission switching unit 502 is provided.

[0409] Each Doppler frequency shift unit 104 adds a predetermined phase rotation φ to the chirp signal input from the radar transmission signal generation unit 101. ndm With additional Doppler shift DOP ndm , and outputs the chirp signal with phase rotation added to the corresponding transmission switching section 502. Here, ndm=1, ..., N DM .

[0410] The ndm-th transmission switching unit 502 switches the output of the ndm-th Doppler frequency shift unit 104 according to the instruction of the time division multiplexing index TM_INDEX and outputs it to the {(ndm-1)×N TM +TM_INDEX} transmitting antennas 105.

[0411] By the operation of the Doppler frequency shift unit 104 and the transmission switching unit 502 as described above, the floor[(n-1) / N TM ]+1 transmission switching unit 502, when the time division multiplexing index TM_INDEX reaches mod(n-1, N TM )+1, the nth transmitting antenna 105 among the Nt transmitting antennas 105 outputs the signal through the floor[(n-1) / N TM ]+1 Doppler frequency shift unit 104 adds a Doppler frequency shift DOP to the output of the radar transmission signal generation unit 101 floor[(n-1) / NTM]+1 The resulting signal.

[0412] For example, the transmitting antenna 105 with Nt=6 is described, and the Doppler multiplexing number is set to N DM =3, and set the time division multiplexing number to N TM =2. In this case, 3(=N DM ) Doppler frequency shift units 104 add Doppler frequency shift amounts DOP1, DOP2, and DOP3 to the chirp signal, respectively. DM ) The time division multiplexing index TM_INDEX of each transmission switching unit 502 includes 2 (=N TM ) elements.

[0413] In this case, for example, the following signal is output from the first transmission antenna 105 at the transmission period Tr.

[0414] Λ1(1)cp(t),0,Λ1(2)cp(t),0,Λ1(3)cp(t),0,... (37)

[0415] Here, cp(t) represents the chirp signal per transmission period Tr. In addition, the Doppler frequency shift unit 104 adds a phase rotation φ ndm The multiplication value when (m) is expressed as Λndm (m), is set to zero when no signal is sent.

[0416] Λ ndm (m) = exp[jφ ndm (m)] (38)

[0417] Similarly, for example, the following signal is output from the second transmission antenna 105 at the transmission period Tr.

[0418] 0,Λ1(1)cp(t),0,Λ1(2)cp(t),0,Λ1(3)cp(t),... (39)

[0419] Similarly, for example, the following signal is output from the third transmission antenna 105 at the transmission period Tr.

[0420] Λ2(1)cp(t),0,Λ2(2)cp(t),0,Λ2(3)cp(t),0,... (40)

[0421] Similarly, for example, the following signal is output from the fourth transmission antenna 105 at the transmission period Tr.

[0422] 0,Λ2(1)cp(t),0,Λ2(2)cp(t),0,Λ2(3)cp(t),... (41)

[0423] Similarly, for example, the following signal is output from the fifth transmission antenna 105 at a transmission period Tr.

[0424] Λ3(1)cp(t),0,Λ3(2)cp(t),0,Λ3(3)cp(t),0,... (42)

[0425] Similarly, for example, the following signal is output from the sixth transmission antenna 105 at the transmission period Tr.

[0426] 0,Λ3(1)cp(t),0,Λ3(2)cp(t),0,Λ3(3)cp(t),... (43)

[0427] In addition, the radar transmitter 100e transmits chirped pulses at a frequency of N. TM The signal is sent in integer multiples (Ncode times). C =N TM ×Ncode.

[0428] [Configuration Example of Radar Receiver 200e]

[0429] Next, explain Fig.11 The structure example of the radar receiving unit 200e shown in FIG.

[0430] In the z-th signal processing unit 206e, the output switching unit 601 selectively switches the output of the beat frequency analysis unit 208 of each transmission cycle Tr to the N-th signal processing unit 206e based on the time division multiplexing index TM_INDEX input from the transmission switching control unit 501. TM Doppler analysis units 209-1 to 209-N TM That is, the output switching unit 601 selects the TM_INDEX-th Doppler analysis unit 209 in the m-th transmission cycle Tr.

[0431] The z-th signal processing unit 206e has N TM A Doppler analysis unit 209 is provided.

[0432] By output switching unit 601, press N TM The sending cycle (N TM ×Tr) inputs the data to the ntm-th Doppler analysis unit 209 in the z-th signal processing unit 206e. Therefore, the ntm-th Doppler analysis unit 209 uses N C Doppler analysis is performed on the data of Ncode transmission cycles in Ncode transmission cycles. Here, ntm = 1, ..., N TM .

[0433] When Ncode is a power of 2, the Doppler analysis unit 209 can apply FFT (Fast Fourier Transform) processing as shown in the following equation.

[0434]

[0435] Here, the FFT size is Ncode, and the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1 / (2N TM ×Tr). In addition, the Doppler frequency interval of the Doppler frequency index fs is 1 / (Ncode×N TM ×Tr), Doppler frequency index f s The range is f s =-Ncode / 2, .., 0, ..., Ncode / 2-1.

[0436] In addition, when Ncode is not a power of 2, for example, FFT processing can be performed by including zero-padded data as an FFT size that is a power of 2. In addition, during FFT processing, window function coefficients such as a Han window or a Hamming window can be multiplied, and by applying the window function, side lobes generated around the beat frequency peak can be suppressed.

[0437] The CFAR unit 210e uses the first to the Nth signal processing units 206e. TM The output of the Doppler analysis unit 209 is subjected to CFAR processing (in other words, adaptive threshold determination), and the distance index f that gives the peak signal is extracted. b_cfar and the Doppler frequency index f s_cfar .

[0438] The CFAR unit 210e adds the power of the output of the Doppler analysis unit 209, for example, in the following manner, and performs a two-dimensional CFAR process including a distance axis and a Doppler frequency axis (equivalent to a relative velocity) or a CFAR process combined with a one-dimensional CFAR process. For example, the process disclosed in Non-Patent Document 2 can be applied to the two-dimensional CFAR process or the CFAR process combined with the one-dimensional CFAR process.

[0439]

[0440] The CFAR unit 210e adaptively sets a threshold and indexes the distances where the received power is greater than the threshold. b_cfar , Doppler frequency index f s_cfar and receiving power information PowerFT(f b_cfar , f s_cfar ) is output to the Doppler multiplexing separation unit 211e.

[0441] The Doppler demultiplexing unit 211e uses the information input from the CFAR unit 210e (for example, the distance index f b_cfar , Doppler frequency index f s_cfar and receiving power information PowerFT(f b_cfar , f s_cfar )), using the output from each Doppler analysis unit 209, the transmission signal transmitted from each transmission antenna 105 is separated.

[0442] The operation of the Doppler demultiplexing unit 211 e will be described below together with the operation of the Doppler frequency shift unit 104 .

[0443] 1st to Nth DM The Doppler frequency shift units 104 add different Doppler frequency shift amounts DOP1, DOP2, ..., DOP to the input chirp signal. NDM Here, as in the first embodiment, the Doppler shift amounts DOP1, DOP2, ..., DOP NDM For example, each interval (Doppler frequency shift interval) is not a value obtained by dividing the Doppler frequency range where aliasing does not occur at equal intervals, but an interval obtained by dividing it at unequal intervals (for example, at least one Doppler interval is different). ndmEach interval can be set to the number Nt of the plurality of transmitting antennas 105 divided by the number N of time division multiplexing TM The resulting value (in other words, the Doppler multiplexing number N DM ) plus a value greater than 1 (e.g., δ), dividing the Doppler frequency range (e.g., -1 / (2N TM ×Tr)≦f d <1 / (2N TM ×Tr)) obtained.

[0444] In the first embodiment, the case where the Doppler multiplexing number is equal to the number of transmission antennas Nt (that is, Nt=N DM ). In contrast, in the present embodiment, since time division multiplexing is used together with Doppler multiplexing, the Doppler multiplexing number N DM The multiplexing number becomes smaller than the number of transmission antennas Nt (for example, Nt>N DM ).

[0445] Therefore, in this embodiment, the Doppler shift amount DOP ndm , using N DM The equation obtained by replacing Nt in equation (5) or equation (15) used in Embodiment 1. In addition, in order to make the phase rotation in the transmission period (Nt) of time division multiplexing TM ×Tr), between the transmission cycles of time division multiplexing (N TM ×Tr), repeatedly outputs the same phase rotation φ ndm (m).

[0446] That is, the ndm-th Doppler frequency shift unit 104 adds a phase rotation φ as shown in the following equation to the input m-th chirp signal. ndm (m) to achieve different Doppler frequency shift DOP ndm .

[0447]

[0448] Here, A is a coefficient that gives a positive or negative polarity of 1 or -1. In addition, δ is a positive number greater than 1. In addition, φ0 is an initial phase, and Δφ0 is a reference Doppler frequency shift phase. In addition, round(x) is a round function that outputs an integer value obtained by rounding off a real value x. In addition, floor[x] is an operator that outputs the nearest integer less than the real number x. In addition, in order to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 209, round(Ncode / (N DM +1))'s item.

[0449] Alternatively, in this embodiment, the phase rotation φ of the following formula may be used: ndm(m) is used to replace formula (46).

[0450]

[0451] Here, dp ndm It is the component that makes the phase rotation into unequal intervals. For example, dp1, dp2, ..., dp DM Yes-round(N C / N DM ) / 2<dp n <round(N C / N DM ) / 2, and not all of them are the same value, and at least one component contains different values. In addition, in order to make the phase rotation amount an integer multiple of the Doppler frequency interval in the Doppler analysis unit 209, round(N C / N DM ) item.

[0452] The operation of the Doppler multiplexing and demultiplexing unit 211e in this embodiment is similar to that of the Doppler multiplexing and demultiplexing unit 211c in Embodiment 2 when Doppler multiplexing and code multiplexing are used together (for example, see Fig. 9 ) in the action by N TM Replace L OC The action is the same as in the case of , so the description of the action is omitted.

[0453] Thereby, the Doppler multiplexing separation unit 211e can separate the Doppler multiplexed signal.

[0454] The above is a description of an operation example of the Doppler demultiplexing unit 211 e.

[0455] exist Fig.11 In the example, the direction estimation unit 212e calculates the distance index f based on the information input from the Doppler demultiplexing unit 211e. b_cfar and separate index information (f demul_DS#1 、f demul_DS#2 ,…,f demul_DS#NDM ), and perform target direction estimation.

[0456] For example, the direction estimation unit 212e extracts the direction corresponding to the distance index f from the output of each Doppler analysis unit 209. b_cfar and separate index information (f demul_DS#1 、f demul_DS#2 ,…,f demul_DS#NDM ) output, generating a virtual receive array correlation vector h(f b_cfar 、f demul_DSx#1 、f demul_DSx#2 ,…,f demul_DS#NDM ) and perform direction estimation processing.

[0457] Virtual receiving array correlation vector h(f b_cfar 、f demul_DSx#1 、f demul_DSx#2 ,…,f demul_DS#NDM ) contains the product of the number of transmitting antennas Nt and the number of receiving antennas Na, that is, Nt×Na elements. The virtual receiving array correlation vector h(f b_cfar 、f demul_DSx#1 、f demul_DSx#2 ,…,f demul_DS#NDM ) is used for the following process, which estimates the direction of the reflected wave signal from the target based on the phase difference between each receiving antenna 202. Here, z=1, ..., Na. In addition, the same method as the first embodiment can be applied as the direction estimation method, for example.

[0458]

[0459] In formula (48), h cal[b] is an array correction value for correcting the phase deviation and amplitude deviation between the transmitting array antennas and the receiving array antennas. b = 1, ..., (Nt × Na). In addition, Txc ntm (f s ) is the transmit phase correction coefficient. Since the transmit antenna is switched by time division, according to the Doppler frequency index f s , different phase rotations will be generated, so the transmission phase correction coefficient corrects the phase rotation to make it consistent with the phase of the reference transmission antenna. For example, when the first time division multiplexing index (ntm=1) is set as the reference transmission antenna, it becomes the following formula. Here, ntm=1, ..., N TM .

[0460]

[0461] As described above, in this embodiment, by using a structure that uses Doppler multiplexing and time division multiplexing together, in addition to the same effects as embodiment 1, the number of signals that are multiplexed and transmitted simultaneously can be increased, thereby being adaptable to a MIMO array structure with an increased number of transmitting antennas.

[0462] In the above description, the Doppler multiplexing number is assumed to be N. DM , set the time division multiplexing number to N TM , and the number of transmitting antennas 105 used is Nt=N DM ×N TM The Doppler multiplexing number and the time division multiplexing number are not limited to this. For example, for N DM Doppler multiplexed signals, it is also possible to set the time division multiplexing number to N instead of making the time division multiplexing number the same. TM the following.

[0463] For example, the transmission antenna 105 with Nt=5 is described, and the Doppler multiplexing number is set to N DM =3, and set the time division multiplexing number to N TM =2. In this case, 3(=N DM ) Doppler frequency shift units 104 add Doppler frequency shift amounts DOP1, DOP2, and DOP3 to the chirp signal, respectively. In addition, the following configuration is used, that is, 3 (= N DM ) transmission switching units 502 switch 2 (= N) with respect to the outputs of the Doppler frequency shift unit 104-1 and the Doppler frequency shift unit 104-2. TM ) transmission antennas and outputs, and the output of the Doppler frequency shift unit 104-3 is from 1(≦N TM In other words, between the radar transmission signals transmitted from the plurality of transmission antennas 105, the number of time division multiplexing applied to the radar transmission signals is N. TM In this case, the processing of the radar receiving unit 200e can use the same processing as described above (Nt=6 transmitting antennas 105, the Doppler multiplexing number is N DM =3, and set the time division multiplexing number to N TM =2) to separate the transmission signal from the transmission antenna of Nt=5. DM Doppler multiplexed signals are generated by using a time division multiplexing number N instead of making the time division multiplexing numbers the same. TM The following time division multiplexing numbers can be increased beyond the Doppler multiplexing number N DM For example, when the Doppler multiplexing number is set to N DM =3, and the time division multiplexing number N TM When the number of transmission antennas Nt is set to 2 or less, the number of transmission antennas Nt (in other words, the number of multiplexed transmissions) can be used in the range of 4, 5, or 6. If expressed in a more general way, Nt can be used in the range of 4, 5, or 6. DM +1≦Nt≦N DM ×N TM The number of transmitting antennas Nt (in other words, the number of multiplexed transmissions) is applied within the range of .

[0464] In addition, a configuration may be used for outputting at least one of the outputs of the plurality of Doppler shift units 104 to the transmission antenna 105 without using the transmission switching unit 502. As described above, by using a configuration in which a signal not using time division multiplexing is output from the transmission antenna for outputting at least one of the outputs of the plurality of Doppler shift units 104, the radar receiving unit 200e can detect whether the output of the Doppler analysis unit 209 includes a Doppler aliasing signal. That is, the maximum Doppler frequency without aliasing derived by the Doppler analysis unit 209 based on the sampling theorem is ±1 / (2Loc×Tr), but as described above, by using the output of at least one Doppler frequency shift unit 104 among the outputs of multiple Doppler frequency shift units 104, a structure that outputs a signal from a transmitting antenna without using time division multiplexing can be used to set the maximum Doppler frequency without aliasing derived by the Doppler analysis unit 209 based on the sampling theorem to ±1 / (2×Tr), and the following effect can also be obtained, namely, expanding the Doppler frequency range that can be detected without ambiguity.

[0465] Furthermore, when Doppler multiplexing and time division multiplexing are used together, the pseudo-random code sequence may be multiplied by the transmission signal in the same manner as in variation 5 of embodiment 1. The code length N of the pseudo-random code sequence LRC It can also be set to less than Ncode and divided into time periods by RC_INDEX(m)=floor[(m-1) / N TM ]+1 to change the random code element index and output the random code element RC (RC_INDEX(m)) of the pseudo-random code sequence RCode.

[0466] In the above, one embodiment of the present disclosure has been described.

[0467] [Other embodiments]

[0468] (Transformation 7)

[0469] In variation 7, for example, the radar apparatus variably sets each interval of the Doppler shift amount at each transmission cycle, and changes the allocation of Doppler multiplexing to the transmission antenna.

[0470] In addition, the basic structure of the radar device of variant 7 is the same as Figure 1 The radar device 10 shown is universal, therefore, reference Figure 1 For example, in variant 7, Figure 1 The operations of the Doppler frequency shift unit 104 , the Doppler analysis unit 209 , the CFAR unit 210 , and the Doppler demultiplexing unit 211 of the radar device 10 shown are different from those of the first embodiment.

[0471] For example, in Doppler multiplexing, when the reception levels of Doppler peaks of a plurality of targets are substantially equal and the intervals between Doppler peaks coincide with the intervals between Doppler shift amounts, the Doppler demultiplexing unit 211 may not be able to make a demultiplexing decision.

[0472] For example, in Variation 3, a case has been described in which the Doppler shift amount is variably set for each radar observation in order to more reliably separate a plurality of targets with respect to the positioning output of the radar device 10 .

[0473] In variation 7, a case is described in which each interval of the Doppler shift amount is variably set according to the transmission cycle in order to more reliably separate multiple targets for the positioning output of the radar device 10. According to variation 7, for one target, the intervals of the Doppler peaks corresponding to the multiple transmission antennas 105 are different according to the transmission cycle, so that the radar device 10 can easily separate multiple targets through a single radar observation.

[0474] An example of a method of setting the Doppler shift amount added in the Doppler shift unit 104 according to the seventh modification will be described below.

[0475] The Doppler shift units 104-1 to 104-Nt each add a different Doppler shift amount DOP to the input chirp signal. n Here, n=1, ..., Nt.

[0476] In addition, the Doppler frequency shift units 104-1 to 104-Nt variably set the Doppler frequency shift amount DOP according to the transmission cycle Tr. n For example, the Doppler shift units 104-1 to 104-Nt set the Doppler shift amount DOP of each odd-numbered transmission period Tr. n odd , and the Doppler frequency shift amount DOP of each even-numbered transmission period Tr n even .

[0477] For example, the n-th Doppler frequency shift unit 104 adds a Doppler frequency shift amount DOP corresponding to the input m-th chirp signal at each odd-numbered transmission period Tr according to the following equation: n odd The phase rotation φ n (m), and add the Doppler frequency shift amount DOP according to the even-numbered transmission period Tr n even The phase rotation φ n (m).

[0478]

[0479] Here, δodd and δ even is a positive number greater than 1 and is set to different values. odd and δ even , the Doppler frequency shift DOP of each odd-numbered transmission cycle Tr n odd , and the Doppler frequency shift amount DOP of each even-numbered transmission period Tr n even In other words, each interval of the Doppler shift amount is variably set according to the transmission cycle Tr.

[0480] In addition, the phase rotation amount φ n The value is not limited to the value shown in equation (50), as long as the Doppler shift amount DOP n odd and Doppler frequency shift DOP n even The phase rotation amount can be changed at different intervals.

[0481] In addition, when the Doppler frequency shift unit 104 adds a phase rotation amount to the radar transmission signal (for example, a chirp signal), spurious signals will be generated in the Doppler region if a phase rotation error is included. Here, for example, if the spurious level is about -20 dB or less of the Doppler peak level, it will not cause a significant degradation effect on the radar detection performance of the radar device 10. Therefore, a phase rotation error in which the spurious level is within a range of about -20 dB or less of the Doppler peak (for example, a range of about 5° to 10°) may be included as a phase rotation error during phase rotation. In addition, in other embodiments (or variations), a phase rotation error in which the spurious level is within a range of about -20 dB or less of the Doppler peak (for example, a range of about 5° to 10°) may also be included.

[0482] exist Figure 1 In the process, the Doppler analysis unit 209 uses the N output from the beat frequency analysis unit 208. C The beat frequency response RFT is obtained by sending chirped pulses z (f b , 1) RFT z (f b , 2), ..., RFT z (f b , N C ), indexed by distance f b Doppler analysis was performed.

[0483] In variation 7, a phase rotation φ is added to the radar transmission signal (for example, a chirp signal) in which the Doppler frequency shift amount of each odd-numbered transmission period Tr is different from the Doppler frequency shift amount of each even-numbered transmission period Tr. n Therefore, the Doppler analysis unit 209 uses the beat frequency response of each odd-numbered transmission period Tr, for example, to calculate the distance index f. b Similarly, the Doppler analysis unit 209 uses the beat frequency response of each even-numbered transmission period Tr, for example, to calculate the Doppler frequency response according to the distance index f. b Doppler analysis was performed.

[0484] For example, in N c When the value is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is N c / 2, the Doppler analysis unit 209 performs FFT processing based on the data obtained at the odd or even transmission period Tr (in other words, at 2Tr). Therefore, the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1 / (4Tr). In addition, the Doppler frequency index f s The Doppler frequency interval is 1 / (Nc×Tr), and the Doppler frequency index f s The range is f s =-N c / 4, ..., 0, ..., N c / 4-1.

[0485] As an example, the following describes N c is a power of 2. In addition, c When the value is not a power of 2, for example, the FFT process can be performed by including zero-padded data as a data size of a power of 2. In addition, the Doppler analysis unit 209 can also multiply the coefficient of a window function such as a Han window or a Hamming window during the FFT process. By applying the window function, the side lobes generated around the beat frequency peak can be suppressed.

[0486] For example, the output VFT of the Doppler analysis unit 209 for the beat frequency response of each odd-numbered transmission period Tr in the z-th signal processing unit 206 is z odd (f b , f s ), and the output VFT of the Doppler analysis unit 209 for the beat frequency response of each even-numbered transmission period Tr. z even (f b , f s ) is represented by the following formula. In addition, j is an imaginary unit, and z=1 to Na.

[0487]

[0488] The CFAR unit 210 performs CFAR processing (in other words, adaptive threshold determination) using the outputs of the Doppler analysis unit 209 from the first to Na-th signal processing units 206, and extracts the distance index f that gives the peak signal. b_cfar and the Doppler frequency index f s_cfar .

[0489] The CFAR unit 210 of the modification 7 performs, for example, VFT analysis of the output of the Doppler analysis unit 209 for the beat frequency response for each odd-numbered transmission period Tr. z odd (f b , f s ) performs CFAR processing, adaptively sets the threshold, and indexes the distance where the received power is greater than the threshold f b_cfar odd , Doppler frequency index f s_cfar odd And receive power information PowerFT odd (f b_cfar odd , f s_cfar odd ) is output to the Doppler multiplexing separation unit 211.

[0490] Similarly, the CFAR unit 210 of the modification 7 performs, for example, a VFT analysis of the output of the Doppler analysis unit 209 for the beat frequency response for each even-numbered transmission period Tr. z even (f b , f s ) performs CFAR processing, adaptively sets the threshold, and indexes the distance where the received power is greater than the threshold f b_cfar even , Doppler frequency index f s_cfar even And receive power information PowerFT even (f b_cfar even , f s_cfar even ) is output to the Doppler multiplexing separation unit 211.

[0491] The Doppler demultiplexing unit 211 generates a Doppler demultiplexing signal based on the information input from the CFAR unit 210 (for example, the distance index f of the beat frequency response for each odd-numbered transmission period Tr). b_cfar odd , Doppler frequency index f s_cfar odd And receive power information PowerFT odd(f b_cfar odd , f s_cfar odd ), and the distance index f of the beat frequency response for each even-numbered transmission period Tr b_cfar even , Doppler frequency index f s_cfar even And receive power information PowerFT even (f b_cfar even , f s_cfar even )), using the output from each Doppler analysis unit 209, the transmission signal transmitted from each transmission antenna 105 (in other words, the reflected wave signal for the transmission signal) is separated from the signal subjected to Doppler multiplexing transmission (hereinafter referred to as "Doppler multiplexing signal").

[0492] The Doppler demultiplexing unit 211 outputs information related to the separated signal to the direction estimation unit 212. The information related to the separated signal may include, for example, a distance index f corresponding to the separated signal. b_cfar and Doppler frequency index (hereinafter, sometimes also referred to as "separation index information") (f demul_Tx#1 、f demul_Tx#2 ,…,f demul_Tx#Nt ). In addition, the Doppler demultiplexing unit 211 outputs the output from each Doppler analysis unit 209 to the direction estimation unit 212.

[0493] As an example, in equation (50), Nt = 3, Δφ0 = 0, φ0 = 0, A = 1, δ odd =1,δ even =2, and N C When the phase rotation is set to a multiple of 4, the radar transmission signal is given a phase rotation amount φ as shown in the following equation: n (m).

[0494] {φ1(1),φ1(2),...,φ1(22),...}={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,...} (52)

[0495]

[0496]

[0497] When the FFT processing of equation (51) is performed in the Doppler analysis unit 209, the Doppler frequency shift amount is DOP1 odd =0, DOP1 even =0, DOP2odd =1 / (8Tr), DOP2 even =1 / (10Tr), DOP3 odd =1 / (4Tr), DOP3 even =1 / (5Tr).

[0498] When using this Doppler shift amount, for example, Fig.12 As shown, for a measured target Doppler frequency f d_TargetDoppler , generating Nt (in Fig.12 There are three Doppler peaks. Fig.12 This is a diagram showing changes in the Doppler peak value of Nt=3 when the horizontal axis represents the target Doppler frequency and the vertical axis represents the output of the Doppler analysis unit 209 (FFT).

[0499] Fig.12 (a) shows an example of the output of the Doppler analysis unit 209 for the beat frequency response of each odd-numbered transmission period Tr. Fig.12 (b) shows an example of the output of the Doppler analysis unit 209 for the beat frequency response of each even-numbered transmission period Tr.

[0500] exist Fig.12 (a) and Fig.12 In (b), for a measured target Doppler frequency f d_TargetDoppler , generating Nt (in Fig.12 There are 3 Doppler peaks in the image, but the intervals between the Doppler peaks are different. Fig.12 In (a), the interval between Doppler peaks is 1 / (8Tr) or 1 / (4Tr). On the other hand, for example, Fig.12 In (b), the interval between Doppler peaks is 1 / (10Tr) or 3 / (10Tr).

[0501] Therefore, for the same distance index f b In the case where there are two targets, even when the difference in the Doppler frequencies of the two targets is consistent with the interval of the Doppler frequency shift amounts of each odd-numbered transmission period Tr, because it is inconsistent with the interval of the Doppler frequency shift amounts of each even-numbered transmission period Tr, the Doppler multiplexing separation unit 211 can separate and detect the signals corresponding to the two targets.

[0502] Similarly, for the same distance index f bIn the case where there are two targets, even when the difference in the Doppler frequencies of the two targets is consistent with the interval of the Doppler frequency shift amounts of each even-numbered transmission period Tr, because it is inconsistent with the interval of the Doppler frequency shift amounts of each odd-numbered transmission period Tr, the Doppler multiplexing separation unit 211 can separate and detect the signals corresponding to the two targets.

[0503] This allows the radar device 10 to easily separate a plurality of targets within one radar observation.

[0504] For example, the following situation is described, that is, for the same distance index f b ,like Fig.13 As shown, the Doppler frequency of target #1 is 0, and the Doppler frequency of target #2 is 1 / (8Tr).

[0505] In this case, for example, Fig.13 As shown in (a), the difference 1 / (8Tr) (in other words, the interval) between the Doppler frequencies of targets #1 and #2 is consistent with the interval (e.g., 1 / (8Tr)) of the Doppler frequency shift amounts of the odd-numbered transmission cycles Tr. Therefore, for example, Fig.13 As shown in (a), in the output of the Doppler analysis unit 209 for the beat response of each odd-numbered transmission period Tr, the Doppler peaks of targets #1 and #2 overlap, so it is difficult for the Doppler demultiplexing unit 211 to separate the signals of targets #1 and #2.

[0506] On the other hand, for example, Fig.13 As shown in (b), the difference 1 / (8Tr) (in other words, the interval) between the Doppler frequencies of targets #1 and #2 does not coincide with the interval (e.g., 1 / (10Tr)) of the Doppler frequency shift amounts of the even-numbered transmission cycles Tr. Therefore, for example, Fig.13 As shown in (b), in the output of the Doppler analysis unit 209 for the beat frequency response of each even-numbered transmission period Tr, the Doppler peaks of targets #1 and #2 do not overlap, so the Doppler demultiplexing unit 211 can easily separate and detect the signals of targets #1 and #2.

[0507] In this way, the radar device 10 is more likely to be able to separate signals corresponding to multiple targets in any one of the transmission cycles Tr with different intervals of Doppler shift amounts. As a result, the radar device 10 can easily separate multiple targets in one radar observation.

[0508] As described above, in variation 7, the radar device 10 variably sets the interval of the Doppler shift amount according to the transmission cycle Tr. As a result, the intervals of the Doppler peaks corresponding to the multiple transmission antennas 105 for one target are different according to the transmission cycle, so the radar device 10 can easily separate multiple targets through a single radar observation.

[0509] (Transformation 8)

[0510] In Variation 8, for example, the radar apparatus variably sets the Doppler shift amount at each transmission cycle, and changes the allocation of Doppler multiplexing to the transmission antennas.

[0511] In addition, the basic structure of the radar device of the variant 8 is the same as Figure 1 The radar device 10 shown is universal, therefore, reference Figure 1 For example, in variant 8, Figure 1 The operations of the Doppler frequency shift unit 104, the Doppler analysis unit 209, the CFAR unit 210, and the Doppler multiplexing and separation unit 211 of the radar device 10 shown are different from those in Embodiment 1. In addition, the operations of the Doppler analysis unit 209, the CFAR unit 210, and the Doppler multiplexing and separation unit 211 of Modification 8 are the same as those of Modification 7, and therefore, the description thereof is omitted here.

[0512] In variation 8, a case is described in which the Doppler shift amount is variably set according to the transmission cycle for the positioning output of the radar device 10. According to variation 8, the positions of the Doppler peaks corresponding to the plurality of transmission antennas 105 for one target are different according to the transmission cycle, so that even when there is a colored interference component in the Doppler region, the radar device 10 can easily separate the target within one radar observation.

[0513] An example of a method of setting the Doppler shift amount added by the Doppler shift unit 104 according to the eighth modification will be described below.

[0514] The Doppler shift units 104-1 to 104-Nt each add a different Doppler shift amount DOP to the input chirp signal. n Here, n=1, ..., Nt.

[0515] In addition, the Doppler frequency shift units 104-1 to 104-Nt variably set the Doppler frequency shift amount DOP according to the transmission cycle Tr. n For example, the Doppler shift units 104-1 to 104-Nt set the Doppler shift amount DOP of each odd-numbered transmission period Tr. n odd , and the Doppler frequency shift amount DOP of each even-numbered transmission period Tr n even .

[0516] For example, the n-th Doppler frequency shift unit 104 adds a Doppler frequency shift amount DOP corresponding to the input m-th chirp signal at each odd-numbered transmission period Tr according to the following equation: nodd The phase rotation φ n (m), and add the Doppler frequency shift amount DOP according to the even-numbered transmission period Tr n even The phase rotation φ n (m).

[0517]

[0518] Here, δ is a positive number greater than 1. A phase rotation φn is added as in equation (55). By setting δ odd and δ even , the Doppler frequency shift DOP of each odd-numbered transmission cycle Tr n odd , and the Doppler frequency shift amount DOP of each even-numbered transmission period Tr n even In other words, the Doppler shift amount is variably set for each transmission period Tr. Thus, the allocation of Doppler multiplexing to the transmission antenna 105 is variably set for each transmission period Tr.

[0519] In addition, the phase rotation amount φ n The value is not limited to the value shown in equation (55), as long as the Doppler shift amount DOP n odd and Doppler frequency shift DOP n even The phase rotation amount can be set in a different manner according to the position (in other words, allocation).

[0520] As an example, in equation (55), let Nt = 3, Δφ0 = 0, φ0 = 0, A = 1, δ = 1, and N C When the phase rotation is a multiple of 4, the radar transmission signal is given a phase rotation φ as shown in the following equation: n (m).

[0521]

[0522]

[0523]

[0524] When the FFT processing of equation (51) is performed in the Doppler analysis unit 209, the Doppler frequency shift amount is DOP1 odd =0, DOP1 even =1 / (8Tr), DOP2 odd =1 / (8Tr), DOP2 even =1 / (4Tr), DOP3 odd=1 / (4Tr), DOP3 even =-1 / (8Tr).

[0525] When using this Doppler shift amount, for example, Fig.14 As shown, for a measured target Doppler frequency f d_TargetDoppler , generating Nt (in Fig.14 There are three Doppler peaks. Fig.14 This is a diagram showing changes in the Doppler peak value of Nt=3 when the horizontal axis represents the target Doppler frequency and the vertical axis represents the output of the Doppler analysis unit 209 (FFT).

[0526] Fig.14 (a) shows an example of the output of the Doppler analysis unit 209 for the beat frequency response of each odd-numbered transmission period Tr. Fig.14 (b) shows an example of the output of the Doppler analysis unit 209 for the beat frequency response of each even-numbered transmission period Tr.

[0527] exist Fig.14 (a) and Fig.14 In (b), for a measured target Doppler frequency f d_TargetDoppler , generating Nt (in Fig.14 There are 3 Doppler peaks in the image, but the positions of the Doppler peaks are different. For example, Fig.14 The output of the Doppler analysis unit 209 shown in (a), and Fig.14 The output of the Doppler analysis unit 209 shown in (b) is shifted by 1 / 8 Tr in the Doppler region.

[0528] Therefore, it is possible to increase the possibility that, for the same distance index fb, even when there is a colored interference component in the Doppler region (in other words, when the interference component is generated in a limited Doppler region), for example, when a Doppler peak is generated in the Doppler region where the interference component is present in one of the transmission cycles of the odd-numbered transmission cycles and the even-numbered transmission cycles, a Doppler peak is generated in a Doppler region different from the Doppler region where the interference component is present in the transmission cycle of the other party. As a result, the Doppler demultiplexing unit 211 can easily perform separation and detection within one radar observation without being affected by interference.

[0529] For example, the following situation is described, that is, for the same distance index f b ,like Fig.15 As shown in FIG. 1 , in the Doppler region, the colored interference component exists in the range of Doppler frequency -1 / (16Tr) to 1 / (16Tr). Fig.15In FIG. 1 , the case where the Doppler frequency of target #1 is 0 is described as an example.

[0530] In this case, for example, Fig.15 As shown in (a), in the output of the Doppler analysis unit 209 for the beat frequency response of each odd-numbered transmission period Tr, part of the Doppler peak of target #1 overlaps with the colored interference component, so it is difficult for the Doppler demultiplexing unit 211 to separate the signal of target #1.

[0531] On the other hand, for example, Fig.15 As shown in (b), in the output of the Doppler analysis unit 209 for the beat frequency response of each even-numbered transmission period Tr, the Doppler peak of target #1 does not overlap with the colored interference component, so the Doppler demultiplexing unit 211 can easily separate the signal of target #1.

[0532] In this way, the radar device 10 is more likely to separate signals corresponding to multiple targets in any transmission period Tr with different Doppler shift amounts (in other words, positions within the Doppler frequency range). As a result, even if there is a colored interference component in the Doppler region, the radar device 10 can easily separate the target within a single radar observation.

[0533] As described above, in variation 8, the radar device 10 variably sets the Doppler shift amount according to the transmission cycle Tr. As a result, the positions of the Doppler peaks corresponding to the plurality of transmission antennas 105 for one target are different according to the transmission cycle, so that even when there is a colored interference component in the Doppler region, the radar device 10 can easily separate the target within one radar observation.

[0534] The above describes modification 8. Modification 7 and modification 8 may be combined. That is, the Doppler shift amount (in other words, the phase rotation amount) may be set so that the intervals and positions of Doppler peaks corresponding to a plurality of transmission antennas 105 for one target differ in each transmission cycle Tr.

[0535] In a radar device of an embodiment of the present disclosure, the radar transmitting unit and the radar receiving unit may also be independently configured at physically separate locations. In addition, in a radar receiving unit of an embodiment of the present disclosure, the direction estimation unit and other components may also be independently configured at physically separate locations.

[0536] In addition, the numerical values ​​used in one embodiment of the present disclosure (for example, the number of transmitting antennas Nt, the number of receiving antennas Na, the number of Doppler multiplexing Nt, the number of transmitting antennas Nt, the number of receiving ... DM , about the phase rotation value (δ, φ0, δ, Δφ0, dp n etc.)) are just examples and are not limited to these values.

[0537] Although not shown in the figure, a radar device of one embodiment of the present disclosure has, for example, a CPU (Central Processing Unit), a recording medium such as a ROM (Read Only Memory) storing a control program, and a working memory such as a RAM (Random Access Memory). In this case, the functions of the above-mentioned parts are realized by the CPU executing the control program. However, the hardware structure of the radar device is not limited to this example. For example, each functional part of the radar device can also be realized as an integrated circuit, that is, an IC (Integrated Circuit). Each functional part can be independently monolithic or monolithic in a manner that includes part or all of it.

[0538] 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 of 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 in the above-mentioned embodiments can be arbitrarily combined within the scope of the disclosure purpose.

[0539] In the above description, the expression “…part” used for each component may be replaced by other expressions such as “…circuitry”, “…device”, “…unit” or “…module”.

[0540] 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.

[0541] 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 part or all of them. 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.

[0542] In addition, the method of integrated circuit is not limited to LSI, and it can also be realized by 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.

[0543] 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.

[0544] <Summary of this disclosure>

[0545] A radar device according to an embodiment of the present disclosure includes: a plurality of transmitting antennas for transmitting transmission signals; and a circuit for adding Doppler frequency shift amounts to the transmission signals transmitted from the plurality of transmitting antennas, wherein each interval of the Doppler frequency shift amounts is set to an interval obtained by dividing a Doppler frequency range to be the object of Doppler analysis into unequal intervals.

[0546] In one embodiment of the present disclosure, each interval of the Doppler frequency shift amount is an interval obtained by dividing the Doppler frequency range by a value obtained by adding an integer greater than 1 to the number of the plurality of transmitting antennas.

[0547] In one embodiment of the present disclosure, each interval of the Doppler frequency shift amount is an interval obtained by adding an offset to an interval obtained by dividing the Doppler frequency range by the number of the plurality of transmitting antennas.

[0548] In one embodiment of the present disclosure, the Doppler frequency shift amount is variably set in each frame in which the transmission signal is transmitted.

[0549] In one embodiment of the present disclosure, the Doppler frequency shift amount is variably set according to a transmission cycle of the transmission signal.

[0550] In one embodiment of the present disclosure, each interval of the Doppler shift amount is variably set in accordance with a transmission cycle of the transmission signal.

[0551] In one embodiment of the present disclosure, the circuit multiplies the transmit signal by a pseudo-random code sequence.

[0552] In one embodiment of the present disclosure, the transmitting antenna is a subarray structure.

[0553] In one embodiment of the present disclosure, the circuit adds the same Doppler frequency shift amount to the transmission signals transmitted from the transmission antennas in the sub-array structure.

[0554] In one embodiment of the present disclosure, the circuit further applies at least one of time division transmission and code division transmission to transmit the transmission signal.

[0555] In one embodiment of the present disclosure, each interval of the Doppler frequency shift amount is an interval obtained by dividing the Doppler frequency range by a value less than the number of the plurality of transmitting antennas.

[0556] In one embodiment of the present disclosure, the circuit further applies code division transmission to send the transmission signal, and each interval of the Doppler frequency shift amount is an interval obtained by dividing the Doppler frequency range by an integer value obtained by dividing the value obtained by dividing the number of the multiple transmitting antennas by the code multiplexing number plus a value greater than 1.

[0557] In one embodiment of the present disclosure, the circuit further applies code division transmission to transmit the transmission signal, and the code division multiplexing numbers applied to the transmission signal are different between the transmission signals transmitted from the multiple transmission antennas.

[0558] In one embodiment of the present disclosure, the circuit further applies time division transmission to send the transmission signal, and each interval of the Doppler frequency shift amount is an interval obtained by dividing the Doppler frequency range by an integer value obtained by dividing the number of the multiple transmitting antennas by the time division number plus a value greater than 1.

[0559] In one embodiment of the present disclosure, the circuit further applies time division transmission to transmit the transmission signal, and the number of time division multiplexing applied to the transmission signal is different between the transmission signals transmitted from the plurality of transmission antennas.

[0560] In one embodiment of the present disclosure, the radar device also includes: multiple receiving antennas for receiving reflected wave signals after the transmitted signal is reflected by the target; and a receiving circuit for detecting the peak value of the reflected wave signal using a threshold value for a power addition value, wherein the power addition value is a power addition value obtained by adding the received powers of the reflected wave signals in each range corresponding to each interval of the Doppler frequency shift amount in the Doppler frequency range.

[0561] In one embodiment of the present disclosure, each interval of the Doppler frequency shift amount is an interval obtained by dividing the Doppler frequency range by a number greater than the Doppler multiplexing number, and for the peaks detected within the Doppler frequency range, the first peaks that are arranged in front when arranged in order from high to low in terms of the received power and whose number is equivalent to the Doppler multiplexing number, and the second peaks other than the first peaks, when the difference between the received level corresponding to the first peak and the received level corresponding to the second peak is greater than a threshold, the receiving circuit separates the transmission signal from the reflected wave signal based on the first peak.

[0562] In one embodiment of the present disclosure, the receiving circuit separates the transmission signals from the reflected wave signals based on the relationship between the transmission antennas and the Doppler shift amounts added to the transmission signals respectively transmitted from the transmission antennas.

[0563] The disclosures of the specification, drawings, and abstract contained in Japanese patent application No. 2019-115492 filed on June 21, 2019 are incorporated herein by reference in their entirety.

[0564] Industrial Applicability

[0565] The present disclosure is suitable as a radar device capable of detecting a wide-angle range.

[0566] Description of Reference Numerals

[0567] 10, 10b, 10c, 10e Radar device

[0568] 100, 100a, 100b, 100c, 100d, 100e radar transmission unit

[0569] 101 Radar transmission signal generation unit

[0570] 102 Modulation signal generation unit

[0571] 103 VCO

[0572] 104 Doppler shift unit

[0573] 105 Transmitting Antenna

[0574] 106 Beam weight generation unit

[0575] 107 Beam weight multiplication unit

[0576] 108 Random code generation unit

[0577] 109, 213 Random code multiplication part

[0578] 200, 200b, 200c, 200e radar receiving unit

[0579] 201 Antenna System Processing Department

[0580] 202 Receiving Antenna

[0581] 203 Wireless receiving unit

[0582] 204 Mixer Section

[0583] 205 LPF

[0584] 206, 206b, 206c, 206e signal processing unit

[0585] 207 AD conversion unit

[0586] 208 Beat Frequency Analysis Department

[0587] 209 Doppler Analysis Department

[0588] 210, 210c, 210e CFAR Department

[0589] 211, 211c, 211e Doppler multiplexing separation unit

[0590] 212, 212c, 212e direction estimation unit

[0591] 301 Orthogonal code generation unit

[0592] 302 Orthogonal code multiplication unit

[0593] 303 Doppler frequency shift and orthogonal code generation unit

[0594] 304 Multiplication part

[0595] 401, 601 output switching unit

[0596] 402 code multiplexing and separation unit

[0597] 501 Sending switching control unit

[0598] 502 Send Switching Unit

Claims

1. A radar device, characterized in that: include: Multiple transmitting antennas to transmit the transmission signal; as well as circuit, adding a Doppler frequency shift amount to the transmission signal transmitted from the plurality of transmission antennas, Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be analyzed by Doppler into unequal intervals. Each interval of the Doppler shift amount is an interval obtained by adding an offset amount to an interval obtained by dividing the Doppler frequency range by the number of the plurality of transmission antennas.

2. The radar device according to claim 1, wherein: The Doppler shift amount is variably set for each frame in which the transmission signal is transmitted.

3. The radar device according to claim 1, wherein: The Doppler shift amount is variably set according to a transmission cycle for transmitting the transmission signal.

4. The radar device according to claim 1, wherein: Each interval of the Doppler shift amount is variably set according to a transmission cycle of the transmission signal.

5. The radar device according to claim 1, wherein: The circuit multiplies the transmit signal by a pseudo-random code sequence.

6. The radar device according to claim 1, wherein: The transmitting antenna is a subarray structure.

7. The radar device according to claim 6, wherein: The circuit adds the same Doppler shift amount to the transmission signal transmitted from the transmission antennas of the sub-array configuration.

8. The radar device according to claim 1, wherein: At least one of the offsets comprises a different value.

9. A radar device, characterized in that: include: Multiple transmitting antennas to transmit the transmission signal; as well as circuit, adding a Doppler frequency shift amount to the transmission signal transmitted from the plurality of transmission antennas, Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be the object of Doppler analysis into unequal intervals. The circuit further applies time division transmission or code division transmission to transmit the transmission signal.

10. The radar device according to claim 9, wherein: Each interval of the Doppler shift amount is an interval obtained by dividing the Doppler frequency range by a value not larger than the number of the plurality of transmission antennas.

11. A radar device, characterized in that: include: Multiple transmitting antennas to transmit the transmission signal; as well as circuit, adding a Doppler frequency shift amount to the transmission signal transmitted from the plurality of transmission antennas, Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be analyzed by Doppler into unequal intervals. The circuit further applies code division transmission to transmit the transmit signal, Each interval of the Doppler shift amount is an interval obtained by dividing the Doppler frequency range by an integer value obtained by adding a value greater than or equal to 1 to a value obtained by dividing the number of the plurality of transmission antennas by the code multiplexing number.

12. A radar device, characterized in that: include: Multiple transmitting antennas to transmit the transmission signal; as well as circuit, adding a Doppler frequency shift amount to the transmission signal transmitted from the plurality of transmission antennas, Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be the object of Doppler analysis into unequal intervals. The circuit further applies code division transmission to transmit the transmit signal, The transmission signals transmitted from the plurality of transmission antennas have different numbers of code multiplexing applied to the transmission signals.

13. A radar device, characterized in that: include: Multiple transmitting antennas to transmit the transmission signal; as well as circuit, adding a Doppler frequency shift amount to the transmission signal transmitted from the plurality of transmission antennas, Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be the object of Doppler analysis into unequal intervals. The circuit further applies time division transmission to transmit the transmission signal, Each interval of the Doppler shift amount is an interval obtained by dividing the Doppler frequency range by an integer value obtained by adding a value greater than or equal to 1 to a value obtained by dividing the number of the plurality of transmission antennas by the time division multiplexing number.

14. A radar device, characterized in that: include: Multiple transmitting antennas to transmit the transmission signal; as well as circuit, adding a Doppler frequency shift amount to the transmission signal transmitted from the plurality of transmission antennas, Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be the object of Doppler analysis into unequal intervals. The circuit further applies time division transmission to transmit the transmission signal, The transmission signals transmitted from the plurality of transmission antennas have different numbers of time division multiplexing applied to the transmission signals.

15. A radar device, characterized in that: include: Multiple transmitting antennas to transmit the transmission signal; as well as circuit, adding a Doppler frequency shift amount to the transmission signal transmitted from the plurality of transmission antennas, Each interval of the Doppler frequency shift amount is set to an interval obtained by dividing the Doppler frequency range to be the object of Doppler analysis into unequal intervals. A plurality of receiving antennas for receiving reflected wave signals after the transmitted signal is reflected by a target; as well as The receiving circuit detects a peak value of the reflected wave signal using a threshold value for a power addition value obtained by adding reception powers of the reflected wave signal in each range corresponding to each interval of the Doppler shift amount in the Doppler frequency range.

16. The radar apparatus according to claim 15, wherein: Each interval of the Doppler frequency shift amount is an interval obtained by dividing the Doppler frequency range by a number greater than the Doppler multiplexing number. Among the peaks detected within the Doppler frequency range, the first peaks that are arranged first when arranged in descending order of the received power and whose number is equivalent to the Doppler multiplexing number, and the second peaks other than the first peaks, when the difference between the received level corresponding to the first peak and the received level corresponding to the second peak is greater than a threshold, the receiving circuit separates the transmission signal from the reflected wave signal based on the first peak.

17. The radar apparatus according to claim 15, wherein: The receiving circuit separates the transmission signals from the reflected wave signals based on the relationship between the transmission antennas and the Doppler shift amounts added to the transmission signals respectively transmitted from the transmission antennas.

Images