Radar device and radar device transmission method

Abstract

To improve detection accuracy of a target in a radar apparatus.SOLUTION: A radar apparatus includes: a plurality of transmission antennas including a first transmission antenna connected to a first feeding line, and a second transmission antenna connected to a second feeding line different from the first feeding line; and a transmission circuitry for transmitting a transmission signal to which a phase rotation amount corresponding to a Doppler shift amount is applied, from the plurality of transmission antennas. A phase deviation due to a line length difference between the first feeding line and the second feeding line is an odd multiple of π / 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

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

[0003] [Patent Document 1] JP 2014-119344 A [Patent Document 2] JP 2019-052952 A [Patent Document 3] JP 2020-204603 A [Patent Document 4] JP 2020-148754 A [Non-patent literature]

[0004] [Non-Patent Document 1] J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 [Non-Patent Document 2] J. Jung, S. Lim, S. -C. Kim and S. Lee, "Solving Doppler-Angle Ambiguity of BPSK-MIMO FMCW Radar System," in IEEE Access, vol. 9, pp. 120347-120357, 2021 [Non-Patent Document 3] M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 [Non-Patent Document 4] Direction-of-arrival estimation using signal subspace modeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28 , Issue: 1 Publication Year: 1992, Page(s): 64-79 Summary of the Invention [Problem to be solved by the invention]

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

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

[0007] A radar device according to an embodiment of the present disclosure includes a plurality of transmitting antennas including a first transmitting antenna connected to a first feed line and a second transmitting antenna connected to a second feed line different from the first feed line, and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, a transmission signal to which a phase rotation amount corresponding to a Doppler shift amount has been imparted, wherein a phase deviation due to a line length difference between the first feed line and the second feed line is an odd multiple of π / 2.

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

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

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

[0011] [Figure 1] FIG. 2 is a diagram showing an example of an antenna arrangement and a target direction of a radar device; [Diagram 2] A block diagram showing a configuration example of a radar device. [Diagram 3] FIG. 1 is a diagram showing an example of a transmission signal when a chirp signal is used; [Figure 4] Flowchart showing an example of an operation for separating Doppler multiplexed signals and estimating directions [Diagram 5] FIG. 13 is a diagram showing an example of the relationship between the phase difference between the feeder line lengths and the target direction in which the receiving phase difference between the transmitting antennas is in phase. [Figure 6] FIG. 13 is a diagram showing an example of the relationship between the phase difference between the feed line lengths and the viewing angle. [Figure 7] FIG. 1 shows an example of a transmitting antenna arrangement and a receiving antenna arrangement. [Figure 8] FIG. 13 is a diagram showing an example of the relationship between the phase difference between the feeder line lengths and the target direction in which the receiving phase difference between the transmitting antennas is in phase. [Figure 9] FIG. 1 is a diagram showing an example of a directivity pattern of a transmitting antenna; [Figure 10] A diagram showing an example of setting the Doppler shift amount [Figure 11] A diagram showing an example of setting the Doppler shift amount [Figure 12] A diagram showing an example of setting the Doppler shift amount [Figure 13] A diagram showing an example of setting the Doppler shift amount [Figure 14] A diagram showing an example of setting the Doppler shift amount [Figure 15] A diagram showing an example of setting the Doppler shift amount DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In the following, we will focus on the multiplexing method in MIMO radar.

[0013] As a method for simultaneously multiplexing and transmitting transmission signals from multiple transmitting antennas, there is, for example, a method for transmitting signals so that multiple transmission signals in the Doppler frequency domain can be separated at the receiving unit (hereinafter referred to as "Doppler Division Multiplexing (DDM) transmission" or "DDM transmission") (see, for example, Patent Document 1).

[0014] In DDM transmission, the transmitter applies phase rotation that gives a different Doppler shift amount (hereinafter referred to as DS amount) to the transmission signal to be transmitted for each transmitting antenna, and the transmission signals are transmitted simultaneously from the multiple transmitting antennas. In DDM transmission, signals received using multiple receiving antennas (waves reflected from targets) are filtered in the Doppler frequency domain, so that the transmission signals transmitted from each transmitting antenna are separated and received.

[0015] In a MIMO radar using DDM transmission, the time interval for observing the received phase change when applying Fourier frequency analysis for Doppler frequency detection (e.g., relative velocity detection) can be shortened compared to time division multiplexing transmission by simultaneously transmitting transmission signals from multiple transmitting antennas. On the other hand, in a MIMO radar using DDM transmission, the transmission signals of each transmitting antenna are separated by filtering on the Doppler frequency axis, so the effective Doppler frequency bandwidth per transmission signal is limited.

[0016] In this way, in a MIMO radar using DDM transmission, the reflected wave signals corresponding to the transmission signals from each transmitting antenna are received and processed on the assumption that they fall within the Doppler frequency range of ±1 / (2Tr×Nt), resulting in a Doppler frequency range similar to that in the case of time division multiplexing transmission, where Nt is the number of transmitting antennas and Tr is the transmission period of the transmission signal.

[0017] For example, as a method for expanding the detection range of Doppler frequencies in DDM transmission, Patent Document 2 discloses a DDM transmission method in which the Doppler intervals assigned to multiple transmitting antennas are unequal. This allows the detectable Doppler frequency range to be expanded. Here, Patent Document 2 uses a multi-value phase shifter with a number of values ​​greater than the number of transmitting antennas. For example, in the case of two transmitting antennas, a phase shifter with three or more values ​​is used. For example, a different phase rotation (for example, one of three phase rotation values ​​of 0, π / 3, 2 / 3π) is applied to the chirp signal for each transmission period for each transmitting antenna. In this case, it is required to narrow the interval of phase rotation by the phase shifter (for example, to increase the number of phase values), and in order to increase the accuracy of the phase rotation of the phase shifter, the circuit configuration of the phase shifter becomes complex, which tends to increase the cost of the radar device.

[0018] For example, Non-Patent Document 2 discloses a method for determining a transmitting antenna so as to maintain continuity of phase change between virtual receiving antennas that depends on the target direction. For example, the phase difference between virtual antennas arranged at equal intervals on a line is a phase change that is fitted by a line whose inclination depends on the target direction. For this reason, in the method disclosed in Non-Patent Document 2, a transmitting antenna is determined so as to increase the consistency of the phase change.

[0019] For example, a case will be described in which 0 [Hz] and -1 / (2Tr) [Hz], which are transmission Doppler shifts (hereinafter also referred to as "transmission Doppler shift (DS) amount") that divide the Doppler frequency range ±1 / (2Tr) equally into Nt (for example, Nt=2), are applied to Nt transmission antennas (Tx#1, Tx#2 when Nt=2). In this case, the radar device multiplies the chirp signal, which is the transmission signal of the m-th transmission period, by phase rotations Φ1(m)=(m-1)ΔΦ1 and Φ2(m)=(m-1)ΔΦ2 (where ΔΦ1=0, ΔΦ2=π), respectively, and transmits the signals from Tx#1 and Tx#2. In this case, when a reflected wave from a target at a certain distance is detected, two Doppler frequency peaks are detected as the Doppler frequency (fd) at a distance Bin corresponding to that distance in the range of -1 / (2Tr)≦fd<-1 / (2Tr). Here, Tr is the transmission period, and m is a natural number equal to or less than a predetermined value. For example, when the Doppler frequency of the reflected wave from the assumed target is in the range of 1 / (2Tr)≦fd<−1 / (2Tr), it exceeds the Doppler division range of ±1 / (4Tr), so it is expected that multiple transmitting antennas (e.g., Tx#1 and Tx#2) will detect by some means which of the two detected Doppler frequency peaks corresponds to.

[0020] The method disclosed in Non-Patent Document 2 is a method for determining a transmitting antenna so as to maintain the continuity of the phase change between virtual receiving antennas depending on the target direction, as described above. For example, a case will be described in which two transmitting antennas and four receiving antennas are arranged, and eight virtual receiving antennas are arranged linearly at equal intervals d. Here, for an arrival angle θ, the reception phase of the received signal from each virtual antenna is determined as follows, with virtual receiving antenna #1 (for example, the virtual receiving antenna at one end) as the reference, and the nth va Virtual receiving antenna #n va The receiving phase at (n va -1)×ω, where ω=2πd×sinθ / λ, where λ is the wavelength of the radar transmission wave. Here, n va =1,…,8.

[0021] For example, when two Doppler frequency peaks (fd1, fd2) are detected in the range of the Doppler frequency axis -1 / (2Tr)≦fd<-1 / (2Tr) at distance Bin corresponding to the distance where the target exists, there are two cases of transmitting antennas corresponding to (fd1, fd2): (Tx#1, Tx#2) and (Tx#2, Tx#1). The radar device selects, for example, from the two cases, the case in which the phase change between the virtual receiving antennas changes linearly with a gradient that depends on the target direction.

[0022] By using this type of transmitting antenna discrimination, it becomes possible to separate multiple signals of the DDM transmission signal, and the Doppler frequency of the reflected wave from the target can be detected in the range of 1 / (2Tr)≦fd<-1 / (2Tr), expanding the Doppler detection range. In addition, in this type of transmitting antenna discrimination, the direction of the target is estimated at the same time as the separation of the multiple signals of the DDM transmission signal.

[0023] The method disclosed in Non-Patent Document 2 can also be applied to the case where existing DDM transmission (for example, Patent Document 1) is used. For example, the method disclosed in Non-Patent Document 2 can also be applied to DDM transmission using a binary phase shifter in the case of two transmitting antennas. For example, by using the method disclosed in Non-Patent Document 2, it is possible to expand the detectable Doppler frequency range without increasing the number of multilevels of the phase shifter. Furthermore, the method disclosed in Non-Patent Document 2 has the effect of suppressing an increase in the number of multilevels of the phase shifter, thereby suppressing an increase in the cost of the radar.

[0024] Incidentally, the path difference of the reflected waves of signals (radar transmission waves) transmitted from multiple transmitting antennas can be an integer multiple of the wavelength of the radar transmission waves depending on the target direction. For example, when the target direction θ is (2πDt sinθ) / λ=±2nπ, the received phases of the reflected waves corresponding to the signals transmitted from multiple transmitting antennas are equal. Here, Dt is the distance between the transmitting antennas, n is an integer value, and λ is the wavelength of the radar transmission waves.

[0025] In such a case, if the technology disclosed in Non-Patent Document 2 is applied, the received phases of reflected waves corresponding to signals transmitted from multiple transmitting antennas will be in-phase, which may make it difficult for the radar device to determine the transmitting antenna.

[0026] For example, as shown in FIG. 1, a case will be described in which two transmitting antennas (Tx#1 and Tx#2) are arranged at intervals of Dt=0.5 wavelengths in a first direction (horizontal direction in FIG. 1), and three receiving antennas (Rx#1, Rx#2, and Rx#3) are arranged at intervals of Dr=1 wavelength in a direction that coincides with the first direction. For example, in FIG. 1, when a target is present in the front direction θ=0° (when (2πDt sinθ) / λ=0), the received phases of reflected waves corresponding to signals transmitted from different transmitting antennas are equal or in phase, making it difficult for the radar device to determine the transmitting antenna. Here, as shown in FIG. 1, the θ direction is the angle formed with the perpendicular direction (broadside direction) with respect to the direction in which the multiple transmitting antennas are arranged. For example, the perpendicular direction with respect to the direction in which the multiple transmitting antennas are arranged is θ=0°.

[0027] In a non-limiting example embodiment of the present disclosure, a method for improving the accuracy of transmit antenna determination is described.

[0028] Hereinafter, an embodiment according to an example of the present disclosure will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and the description thereof will be omitted to avoid duplication.

[0029] The following describes a configuration (e.g., a MIMO radar configuration) in which a radar device transmits different transmit signals simultaneously multiplexed from multiple transmit antennas in a transmit branch, and a receive branch separates each transmit signal for receiving processing.

[0030] In addition, the following describes, as an example, the configuration of a radar system using a frequency-modulated pulse wave such as a chirp pulse (also called fast chirp modulation). However, the modulation system is not limited to frequency modulation. For example, an embodiment of the present disclosure is also applicable to a radar system using a pulse compression radar that transmits a pulse train after phase modulation or amplitude modulation.

[0031] The radar device also performs, for example, DDM transmission. Furthermore, the radar device multiplexes and transmits, using multiple transmission antennas, signals (hereinafter referred to as "Doppler multiplexed (DDM) transmission signals" or "DDM transmission signals") that have been given phase rotations (for example, phase shifts) corresponding to different DS amounts corresponding to the number of Doppler multiplexes in DDM transmission.

[0032] [Radar device configuration] The radar device 10 in FIG. 2 includes a radar transmitter (transmitting branch) 100 and a radar receiver (receiving branch) 200.

[0033] The radar transmitter 100 generates a radar signal (radar transmission signal) and transmits the radar transmission signal at a specified transmission period (hereinafter referred to as the "radar transmission period") using a transmitting antenna unit 109 (e.g., a transmitting array antenna) consisting of multiple transmitting antennas (e.g., Nt antennas).

[0034] The radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target, using a receiving antenna unit 202 (e.g., a receiving array antenna) including multiple receiving antennas 202-1 to 202-Na. The radar receiver 200 processes the reflected wave signal received by each receiving antenna, for example, to detect the presence or absence of a target or estimate the arrival distance, Doppler frequency (e.g., relative speed), and arrival direction of the reflected wave signal, and outputs information on the estimation result (e.g., positioning information).

[0035] The radar device 10 may be mounted on a moving object such as a vehicle, and the positioning output (information on the estimation result) of the radar receiver 200 may be connected to a control device ECU (Electronic Control Unit) (not shown) such as an Advanced Driver Assistance System (ADAS) that improves collision safety or an autonomous driving system, and may be used for vehicle drive control or alarm call control.

[0036] The radar device 10 may be attached to a relatively high structure (not shown), such as a roadside utility pole or a traffic light. The radar device 10 may be used, for example, as a sensor in a support system for improving the safety of passing vehicles or pedestrians or a system for preventing intrusion of suspicious persons (not shown). The positioning output of the radar receiving unit 200 may be connected to a control device (not shown) in the support system for improving safety or the system for preventing intrusion of suspicious persons, and used for alarm generation control or abnormality detection control. The uses of the radar device 10 are not limited to these, and the radar device 10 may be used for other uses.

[0037] Moreover, a target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including four-wheeled and two-wheeled vehicles), a person, a block, a curb, and the like.

[0038] [Configuration of radar transmitter 100] The radar transmitter 100 includes a radar transmission signal generator 101 , a phase rotation amount setting unit 105 , a phase rotation unit 107 , and a transmitting antenna unit 109 .

[0039] The radar transmission signal generating unit 101 generates a radar transmission signal. The radar transmission signal generating unit 101 includes, for example, a transmission signal generation control unit 102, a modulation signal generating unit 103, and a VCO (Voltage Controlled Oscillator) 104. Each component of the radar transmission signal generating unit 101 will be described below.

[0040] The transmission signal generation control unit 102 sets, for example, a transmission signal generation timing for each radar transmission cycle, and outputs information on the set transmission signal generation timing to the modulation signal generating unit 103 and the phase rotation amount setting unit 105 (for example, the Doppler shift setting unit 106). Here, the radar transmission cycle (also called the transmission cycle) is denoted as Tr.

[0041] The modulation signal generating unit 103 periodically generates a modulation signal having a modulation frequency of, for example, a sawtooth shape, based on information relating to the timing of generation of a transmission signal for each Tr input from the transmission signal generation control unit 102 .

[0042] Based on the modulation signal input from the modulation signal generating unit 103, the VCO 104 outputs a frequency modulation signal (hereinafter, for example, referred to as a frequency chirp signal or chirp signal) to the phase rotation unit 107 and the radar receiving unit 200 (mixer unit 204 described later) as a radar transmission signal (radar transmission wave) as shown in Fig. 3. In Fig. 3, the vertical axis represents the modulation frequency (transmission frequency) and the horizontal axis represents time.

[0043] In the following description, the modulated signal generating unit 103 generates a modulated signal so that the chirp signal is transmitted Nc times for each Tr for one radar positioning. The VCO 104 outputs the chirp signal Nc times for each Tr based on the operation of the modulated signal generating unit 103. Each of the Nc Tr is represented by an index m, where m=1, . . . Nc.

[0044] The radar device 10 performs radar positioning multiple times, thereby detecting the time variation of the target position.

[0045] The phase rotation amount setting unit 105 sets the amount of phase rotation (e.g., the amount of phase rotation corresponding to DDM transmission) to be applied to the radar transmission signal for each Tr in the phase rotation unit 107, based on information related to the transmission signal generation timing for each Tr input from the transmission signal generation control unit 102. The phase rotation amount setting unit 105 has, for example, a Doppler shift (DS) setting unit 106.

[0046] The DS setting unit 106 sets a phase rotation amount corresponding to the DS amount to be assigned to the radar transmission signal (e.g., a chirp signal) based on information regarding the transmission signal generation timing for each Tr, and outputs information regarding the set phase rotation amount to the phase rotation unit 107.

[0047] The phase rotation unit 107 imparts the phase rotation amount input from the DS setting unit 106 to the chirp signal input from the VCO 104, and outputs the phase-rotated signal to the transmitting antenna unit 109. For example, the phase rotation unit 107 includes a phase shifter, a phase modulator, and the like (not shown). The output signal from the phase rotation unit 107 is amplified to a specified transmission power, and is radiated into space from each transmitting antenna via a power feed line 108 connected to each transmitting antenna. For example, a radar transmission signal is given a phase rotation amount corresponding to the DS amount, and is multiplexed and transmitted from a plurality of transmitting antennas.

[0048] Here, the power supply lines 108 connected to each transmitting antenna (for example, Tx#1 to Tx#Nt) do not all need to be equal in length. For example, at least two of the power supply lines 108 may have different lengths.

[0049] In the following, the lengths of the power supply lines 108-1 to 108-Nt connected to Tx#1 to #Nt are denoted by L1 to L Nt It is written as follows.

[0050] Furthermore, as the phase difference of the radar transmission signal caused by the difference in the feeder line length between the feeder lines 108, for example, the phase differences of Tx#1 to #Nt when Tx#tref is used as the reference are written as γ(1,tref) to γ(Nt,tref) (expressed in radians). For example, when Tx#1 is used as the reference (tref=1), the phase differences of Tx#1 to #Nt can be written as γ(1,1) to γ(Nt,1). Note that γ(1,1)=0 [rad]. Note that the phase differences expressed by γ(1,tref) to γ(Nt,tref) can be regarded as having the same value even if an integer multiple of 2π is added.

[0051] If the radar transmission signal has a wide frequency band such as a chirp signal, the phase difference at the center frequency of the radar transmission signal may be used as the representative value. An example of setting the feeder line length will be described later.

[0052] Next, an example of a method for setting the amount of phase rotation in phase rotation setting section 105 will be described.

[0053] The DS setting unit 106 sets the DS amount DOP ndm The amount of phase rotation φ for adding ndm Set where ndm=1~N DM N DM is the number of different DS amounts set, and is hereinafter referred to as the "Doppler multiplex number (DDM number)."

[0054] In the radar device 10, the number of DDMs N DM may be set to the same number as the number of transmitting antennas Nt used for multiplex transmission. In the following, as an example, the number of DDMs N DM When Nt is the same as the number of transmit antennas used for multiplex transmission (N DM =Nt), the number of DDMs N DM is not limited to this. For example, the number of DDMs N DM may be set to a number smaller than Nt. Note that the number of DDMs N DM must be 2 or more.

[0055] DOP1, DOP2, ~, DOP N_DM ("N_DM" is "N DM For example, the DOP1, DOP2, ..., DOP N_DM For example, 0≦DOP1,DOP2,~,DOP N_DM < 1 / Tr. Alternatively, DOP1, DOP2, ~, DOP N_DM may be set to satisfy, for example, equation (1).

number

[0056] Also, for example, DOP1, DOP2, ~, DOP N_DM Minimum DS interval Δf MinInterval may satisfy the following formula (2). Note that the DS interval (also written as DDM interval or Doppler interval) is DOP1, DOP2, ..., DOP N_DM It may be defined as the absolute value of the difference between any two DS amounts.

number

[0057] Also, for each DOP1, DOP2, ~, DOP N_DM The amount of phase rotation φ for adding ndm may be assigned, for example, as shown in the following equation (3).

number

[0058] In addition, the intervals are equal to Δf MinInterval When the DS amount is set to be equal to the DOP ndm The amount of phase rotation φ for adding ndm is assigned, for example, as shown in the following equation (4).

number

[0059] In addition, the minimum DS interval Δf MinInterval The narrower the DS interval, the more likely it is that interference between DDM signals will occur, and the more likely it is that the target detection accuracy will be reduced (e.g., deteriorated). Therefore, it is preferable to widen the interval between the DS amounts as long as the constraints of formula (2) are satisfied. For example, when the equality sign is satisfied in formula (2) (e.g., Δf MinInterval =1 / (T r N DM)) can maximize the interval between DDM signals in the Doppler domain (hereinafter referred to as "maximum equal interval DS amount setting"). In this case, DOP1, DOP2, ..., DOP N_DM The phase rotation range is from 0 to less than 2π, DM Each is assigned a different phase rotation. For example, DOP ndm The amount of phase rotation φ for adding ndm is assigned as shown in the following formula (5). Note that in the following, angles are expressed in radians.

number

[0060] In addition, DOP1, DOP2, ~, DOP N_DM The allocation of the phase rotation amount to be applied is not limited to the above allocation method. For example, the phase rotation amount allocation table may be used to allocate DOP1, DOP2, ..., DOP N_DM Phase rotation amount φ1,φ2,~,φ N_DM (However, "N_DM" is N DM ) may be randomly assigned.

[0061] In addition, when setting the amount of DS at equal intervals, Δf MinInterval =1 / (T r (N DM +N int )), the amount of phase rotation may be set as in the following equation (6). int takes an integer value. In this case, the amount of DS is set at uneven intervals, and a multi-level phase shifter with a number of multi-levels greater than the number of transmitting antennas Nt is used. For example, in the case of two transmitting antennas, N int If =1, DOP ndm The amount of phase rotation φ for adding ndmAny two of the three phase rotation amounts 0, π / 3, and 2 / 3π are used. Unequally spaced DS amount settings narrow the interval of phase rotation by the phase shifter (increase the number of phase multi-values) compared to equally spaced DS amount settings. Unequally spaced DS amount settings require higher accuracy of phase rotation of the phase shifter, which tends to complicate the circuit configuration of the phase shifter.

number

[0062] The DS setting unit 106 sets the ndm-th DS amount DOP in the m-th Tr. ndm The amount of phase rotation φ ndm For this, the phase shift (PS) amount ψ ndm (m) is set and output to the phase rotation unit 107. Here, m=1 to Nc, ndm=1 to N DM It is.

number

[0063] The method for setting the amount of phase rotation in phase rotation setting section 105 has been described above.

[0064] In FIG. 2, outputs from Nt phase rotation units 107 (e.g., called Doppler multiplexed signals (DDM signals)) are amplified to a specified transmission power, and then radiated into space from each of the transmitting antennas via feed lines 108 connected to the Nt transmitting antennas of transmitting antenna unit 109.

[0065] For example, in the case of Nt=2, the phase rotation unit #1 outputs a signal cp(t)exp[j(m-1)×φ1] obtained by adding a phase rotation amount (m-1)×φ1 to the chirp signal cp(t) generated in the radar transmission signal generation unit 101 in every m-th transmission period. The output of the phase rotation unit #1 is output from Tx#1. Here, cp(t) represents the chirp signal in every transmission period. Similarly, the phase rotation unit #2 outputs a signal cp(t)exp[j(m-1)×φ2] obtained by adding a phase rotation amount (m-1)×φ2 to the chirp signal cp(t) generated in the radar transmission signal generation unit 101 in every transmission period in every m-th transmission period. The output of the phase rotation unit #2 is output from Tx#2. Here, j is an imaginary unit.

[0066] [Configuration of radar receiver 200] 2, the radar receiving unit 200 includes a receiving antenna unit 202 including Na receiving antennas Rx#1 to Rx#Na. The radar receiving unit 200 also includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 210, and a Doppler multiplexing (DDM) separation / direction estimation unit 211. The Na antenna system processing units 201-1 to 201-Na, the CFAR unit 210, and the DDM separation / direction estimation unit 211 may be collectively referred to as a receiving circuit. The receiving circuit estimates the direction of a target by using a reflected wave signal that is a transmission signal reflected by the target.

[0067] The receiving antenna units 202 Rx#1 to Rx#Na receive reflected wave signals that are radar transmission signals reflected by targets, and output the received reflected wave signals to the corresponding antenna system processors 201 as received signals.

[0068] Each antenna system processing unit 201 includes a radio reception unit 203 and a signal processing unit 206 .

[0069] The signals received in Na Rx#1 to Rx#Na are output to Na radio reception units 203, respectively. In addition, output signals from Na radio reception units 203 are output to Na signal processing units 206, respectively.

[0070] The radio reception unit 203 has a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with a chirp signal, which is a transmission signal, input from the radar transmission signal generation unit 101. The radio reception unit 203, for example, passes the output of the mixer unit 204 through the LPF 205. This outputs a beat signal with a frequency corresponding to the delay time of the reflected wave signal. For example, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulated wave), which is the transmission signal (radar transmission wave), and the frequency of the reception chirp signal (reception frequency modulated wave), which is the reception signal (radar reflected wave), is obtained as the beat frequency.

[0071] The signal processing unit 206 of each antenna system processing unit 201-z (where z=any of 1 to Na) has an AD conversion unit 207, a beat frequency analysis unit 208, and a Doppler analysis unit 209.

[0072] The signal (eg, beat signal) output from the LPF 205 is converted by the AD conversion unit 207 in the signal processing unit 206 into discrete sample data that has been discretely sampled.

[0073] The beat frequency analysis unit 208 calculates N data The discrete sample data is subjected to frequency analysis processing (for example, FFT processing), whereby the signal processing unit 206 outputs a frequency spectrum in which a peak appears at a beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave).

[0074] Here, the beat frequency response output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 obtained by transmitting the m-th chirp pulse is called “RFT z (fb ,m) where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,~,(N data / 2)-1, z = 1 to Na, m = 1 to N C f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (e.g., the closer the distance to the target).

[0075] Also, the beat frequency index f b is calculated by the following equation (8): b ) can be transformed into the beat frequency index f b Let "distance index f b " It is called.

number

[0076] Here, B w represents the frequency modulation bandwidth within the range gate of the chirp signal, and C0 represents the speed of light. In addition, in equation (8), C0 / (2B w ) represents the distance resolution.

[0077] The Doppler analysis unit 209 receives the beat frequency response RFT output from the beat frequency analysis unit 208. z (f b , m) is input for each Tr. Therefore, the Doppler analysis unit 209 calculates data for each Nc transmission period (for example, the beat frequency response RFT input from the beat frequency analysis unit 208). z (f b ,m)) to f b Doppler analysis is performed every 10 minutes.

[0078] For example, if Ncode is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is Nc, and the maximum Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is ±1 / (2Tr). Also, the Doppler frequency index (hereinafter referred to as DF Index) f s The Doppler frequency interval of DF Index f s The range of f s =-Nc / 2,~,0,~,Nc / 2-1.

[0079] In the following, as an example, a case where Nc is a power of 2 will be described. If Nc is not a power of 2, for example, by including zero-padded data, FFT processing is possible with a data size (FFT size) of a power of 2.

[0080] For example, the output VFT of the Doppler analysis unit 209 of the z-th signal processing unit 206 z (f b ,f s ) is expressed by the following formula (9), where j is the imaginary unit and z=1 to Na.

number

[0081] The processing in each component of the signal processing unit 206 has been described above.

[0082] [Example of operation of CFAR section 210] In FIG. 2, the CFAR unit 210 performs CFAR processing (for example, adaptive threshold determination) using the output of the Doppler analysis unit 209 of each of the first to Na-th signal processing units 206, and calculates the distance index (hereinafter, f b_cf ) and DF Index (hereafter, f s_cf The CFAR unit 210 extracts, for example, the output VFT of the Doppler analysis unit 209 of the first to Na-th signal processing units 206. z (f b ,f s) are power-added, and two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity) or CFAR processing combining one-dimensional CFAR processing is performed (for example, the processing disclosed in Non-Patent Document 3 may be applied).

[0083] DOP ndm The amount of phase rotation φ for adding ndm For example, when equation (5) is used, the intervals of the DS amount in the Doppler frequency domain in the output of the Doppler analysis unit 209 are equal, and if the interval ΔFD of the DS amount is expressed by the interval of the DF index, then ΔFD=Nc / N DM Therefore, in the output of Doppler analysis section 209, peaks are detected at intervals of ΔFD for each DDM signal in the Doppler frequency domain.

[0084] Therefore, the CFAR unit 210 may divide each output of the Doppler analysis unit 209 into ranges of ΔFD, and perform power addition (for example, called "Doppler domain compression") on each of the DDMed signal peak positions for each divided range as shown in the following equation (10), and then perform CFAR processing (for example, called "Doppler domain compression CFAR processing" and written as DC-CFAR). sc =-ΔFD / 2,~,(ΔFD / 2)-1. For example, ΔFD=Nc / N DM If f sc =-Nc / (2N DM ),~,(Nc / (2N DM ))-1. DC-CFAR is described in, for example, Patent Document 3, and a detailed description thereof will be omitted.

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[0085] In addition, in formula (10), DF Index f SC If +(ndm-1)×ΔFD is equal to or larger than Nc / 2, the Doppler frequency is folded back and output, so that the CFAR unit 210 SC+(ndm-1)×ΔFD)-Nc. Similarly, the DF Index f SC When +(ndm-1)×ΔFD is equal to or smaller than −Nc / 2-1, the Doppler frequency is folded back and output by the CFAR unit 210, so that (f SC +(ndm-1)×ΔFD)+Nc is output as the DF Index.

[0086] The CFAR unit 210 using DC-CFAR adaptively sets a threshold value, for example, and calculates f b_cf , f sc_cf , and N DM DF Index(f sc_cf +(ndm-1)×ΔFD) b_cf ,f sc_cf +(ndm-1)×ΔFD), and the output VFT of the Doppler analysis unit 209 z (f b_cf ,f sc_cf +(ndm-1)×ΔFD) to the DDM separation / direction estimation unit 211. Here, ndm=1, ∼, N DM It is.

[0087] [Example of operation of the Doppler multiplex (DDM) separation / direction estimation unit 211] Next, a description will be given of an example of the operation of DDM separation / direction estimation section 211 shown in Fig. 2. Note that, below, a description will be given of an example of the processing of DDM separation / direction estimation section 211 when DC-CFAR is used in CFAR section 210.

[0088] The DDM separation / direction estimation unit 211 is DM DDM separation processing and direction estimation processing are performed on (=Nt) DDM signals.

[0089] For example, the DDM separation / direction estimation unit 211 receives f b_cf , f sc_cf , and N DMUsing the received power information at the DF Index of each DDM signal and the outputs of the Doppler analysis units 209 of the first to Na-th signal processing units 206, Nt DDM-transmitted signals are separated, and the transmitting antenna is discriminated (for example, determined or identified) together with the direction estimation process.

[0090] Also, the DDM separation / direction estimation unit 211 outputs, for example, the Doppler frequency (for example, Doppler speed or relative speed) and the direction estimation process result based on the discrimination result of the transmitting antenna.

[0091] FIG. 4 is a flowchart showing an operation example in the DDM separation / direction estimation unit 211.

[0092] <Step 1: Received power comparison between DDM signals (DDM received power comparison determination)> The DDM separation / direction estimation unit 211 determines whether N b_cf DDM signals are included for the N DM DF Indexes (f sc_cf +(ndm-1)×ΔFD) input from the CFAR unit 210. DM For example, the DDM separation / direction estimation unit 211 compares the received power (PowerFT(f

[0093] ,f sc_cf +(ndm-1)×ΔFD)) at the DF Index (f b_cf ,f sc_cf +(ndm-1)×ΔFD)), and determines whether the difference in received power between each DF Index is different by a predetermined level or more (here, ndm = 1 to N DM is an integer). For example, the DDM separation / direction estimation unit 211 determines whether the difference in received power at N DM DF Indexes is equal to or less than the threshold value, or whether the received level ratio at N DM DF Indexes is equal to or less than the threshold value (hereinafter referred to as "DDM received power comparison determination").

[0094] When the determination condition of the DDM received power comparison determination is satisfied, the DDM separation / direction estimation unit 211 sets fb_cf The output VFT of the Doppler analysis unit 209 in z (f b_cf , f sc_cf +(ndm - 1)×ΔFD) is determined to include N DM pieces of DDM signals, and the process of Step 2 described later is performed.

[0095] On the other hand, when the determination condition of the DDM reception power comparison determination is not satisfied, the DDM separation / direction estimation unit 211 determines that the output of the Doppler analysis unit 209 in f b_cf does not include DDM signals, but is a noise signal or an interference signal, and does not perform the process of Step 2 described later.

[0096] <Step 2: DDM Separation Process (Transmitting Antenna Discrimination)> The DDM separation / direction estimation unit 211 uses the output VFT of the Doppler analysis unit 209 in f b_cf to discriminate (or determine, identify) which transmitting antenna's received signal among the Nt transmitting antennas the N z (f b_cf , f sc_cf +(ndm - 1)×ΔFD) are the received signals of (hereinafter referred to as "transmitting antenna discrimination"). DM Hereinafter, an example of the transmitting antenna discrimination process (hereinafter also referred to as TxSel) will be described.

[0097] Note that hereinafter, the output VFT of the Doppler analysis unit 209 of the z-th signal processing unit 206 in f

[0098] in which it is determined that N DM pieces of DDM signals are included b_cf is denoted as "VFT z (f b_cf , f sc_cf +(ndm - 1)×ΔFD)". Here, fddm(ndm) = f z (f b_cf , fddm(ndm))". Here, fddm(ndm) = f sc_cf +(ndm - 1)×ΔFD.

[0099] TxSel is f b_cfN of the Doppler analysis unit 209 in DM (=Nt) output VFTs z (f b_cf , fddm(ndm)) (where ndm = 1 to N DM ) and the process of associating with Tx#1, ~, #Nt.

[0100] Here, the order on the Doppler frequency axis of the N DM DDM signals during transmission does not change and changes cyclically. For example, TxSel is the process of selecting one of the Nt candidates regarding the correspondence between the N DM (=Nt) outputs of the Doppler analysis unit 209 and the Nt transmission antennas.

[0101] For example, when N DM = Nt = 3, the case where DDM signals with fd1 < fd2 < fd3 are assigned to each of the Nt transmission antennas {Tx#1, Tx#2, Tx#3} will be described. In this case, the candidates for the output of the Doppler analysis unit 209 are {VFT z (f b_cf , fddm(1)), VFT z (f b_cf , fddm(2)), VFT z (f b_cf , fddm(3))}, {VFT z (f b_cf , fddm(2)), VFT z (f b_cf , fddm(3)), VFT z (f b_cf , fddm(1))}, and {VFT z (f b_cf , fddm(3)), VFT z (f b_cf , fddm(1)), VFT z (f b_cf , fddm(2))}, three candidates. TxSel is the process of selecting one candidate from the three candidates of the output of the Doppler analysis unit 209.

[0102] Among the Nt candidates of the output of the Doppler analysis unit 209, the output VFT of the Doppler analysis unit 209 with ndm = 1 z (f b_cf , fddm(1)) corresponding to Tx#1 is designated as the "first transmission antenna candidate". Similarly, the output VFT of the Doppler analysis unit 209 with ndm = 2 z (f b_cf , fddm(2)) corresponding to Tx#1 is designated as the "second transmission antenna candidate". Hereinafter, the output VFT of the Doppler analysis unit 209 with ndm = ndt z (f b_cf , fddm(ndt)) corresponding to Tx#1 is designated as the "ndt-th transmission antenna candidate". Here, ndt = 1 to Nt.

[0103] Also, the Nt-order column vector with the output of the Doppler analysis unit 209 of the ndt-th transmission antenna candidate corresponding to Tx#1 to Tx#Nt as elements is denoted as the "ndt-th transmission antenna candidate vector DopTx(ndt, z)".

[0104] For example, when N DM = Nt = 3, and DDM signals with fd1 < fd2 < fd3 are assigned to each of the Nt transmission antennas {Tx#1, Tx#2, Tx#3}, each of the first to third transmission antenna candidate vectors DopTx(1, z), DopTx(2, z), DopTx(3, z) is expressed as follows. Here, the superscript T represents vector transposition. DopTx(1, z) = {VFT z (f b_cf , fddm(1)) VFT z (f b_cf , fddm(2)) VFT z (f b_cf , fddm(3))} T DopTx(2, z) = {VFT z (f b_cf , fddm(2)) VFT z (f b_cf , fddm(3)) VFT z (f b_cf, fddm(1))} T DopTx(3, z) = {VFT z (f b_cf , fddm(3))VFT z (f b_cf , fddm(1))VFT z (f b_cf , fddm(2))} T

[0105] <Step 2-1: Transmission Antenna Interference Correction> The DDM separation / direction estimation unit 211 performs transmission antenna interference correction (hereinafter referred to as TxCal) on DopTx(ndt, z).

[0106] In TxCal, the DDM separation / direction estimation unit 211 performs a process of multiplying, for example, a correction coefficient Ct(ndt) that corrects the phase deviation between Tx#1 to Tx#Nt. The correction coefficient Ct(ndt) can be calculated using, for example, a target with a known direction, and a value obtained in advance before radar ranging can be used. In this embodiment, by using the power supply line 108 with a power supply line length including different lengths, a predetermined phase difference (or phase deviation) between transmission antennas is set. Therefore, the correction coefficient Ct(ndt) is expressed as, for example, the following equation (11) when the phase deviation is based on Tx#1 (tref = 1). Here, the correction coefficient Ct(1) for Tx#1 is 1. [Equation]

[0107] Also, the TxCal process is expressed as the following equation (12). Here, diag(Ct) is an Nt-order diagonal matrix, and the elements of the diagonal matrix are {Ct(1)Ct(2)…Ct(Nt)}. Also, DopTxCal(ndt, z) represents the ndt-th transmission antenna candidate vector after TxCal (hereinafter, the "ndt-th deviation-corrected transmission antenna candidate vector") based on the output of the Doppler analysis unit 209 of the z-th signal processing unit 206. [Equation]

[0108] For example, when N DM = 2, the first transmission antenna candidate vector is DopTx(1,z)=[VFT z (f b_cf , fddm(1))VFT z (f b_cf , fddm(2))] T . In this case, by TxCal, the DDM separation / direction estimation unit 211 outputs DopTxCal(1,z)=[Ct(1)×VFT z (f b_cf , fddm(1))Ct(2)×VFT z (f b_cf , fddm(2))] T . Similarly, the second transmission antenna candidate vector is DopTx(2,z)=[VFT z (f b_cf , fddm(2)), VFT z (f b_cf , fddm(1))} T . In this case, by TxCal, the DDM separation / direction estimation unit 211 outputs DopTxCal(2,z)={Ct(1)×VFT z (f b_cf , fddm(2))Ct(2)×VFT z (f b_cf , fddm(1))} T .

[0109] <Step2-2: Direction Estimation Processing for Each Transmission Antenna Candidate> Based on the ndt-th deviation-corrected transmission antenna candidate vector, the DDM separation / direction estimation unit 211 performs direction estimation processing (hereinafter referred to as "the ndt-th candidate DOA processing") for each transmission antenna candidate.

[0110] In the ndt-th candidate DOA processing, the DDM separation / direction estimation unit 211 uses, for example, the ndt-th deviation-corrected transmission antenna candidate vector to calculate the azimuth direction θ in the direction estimation evaluation function P H (θ u , ndt) uwithin a predetermined angle range to calculate a spatial profile. The DDM separation / direction estimation unit 211 outputs the maximum peak direction θmax(ndt) and the maximum peak power value Pmax(ndt) of the calculated spatial profile.

[0111] In addition, the direction estimation evaluation function value P H (θ u , ndt) can be calculated using various methods depending on the direction-of-arrival estimation algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 4 may be used.

[0112] For example, when the beamformer method is used, the direction estimation evaluation function value P H (θ u , ndt) is expressed by the following equation (13). In addition to the beamformer method, other methods such as Capon and MUSIC can also be applied.

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[0113] In equation (13), AllDopTxcal(ndt) represents the receiving vector of the virtual receiving antenna, and is a vector in which the elements of each column vector DopTxCal(ndt,1) to DopTxCal(ndt,Na) are arranged in order in the column direction, as shown in the following equation (14), and represents a column vector consisting of Nt × Na elements.

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[0114] In addition, in formula (13), the superscript H indicates a Hermitian transpose operator for column vectors, and the superscript T indicates a transpose operator for column vectors.

number

[0115] In addition, in equation (13), a(θu ) is the azimuth direction θ of the radar transmission signal u a(θ u ) is expressed as a column vector having Na elements as in the following equation (15), when the receiving antennas are arranged in a line at equal intervals Dr.

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[0116] In equation (15), λ is the center frequency f c is the wavelength of the radar transmission signal (e.g., a chirp signal) when c It is.

[0117] In addition, in the formula (13),

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[0118] In addition, in equation (13), b(θ u ) is the azimuth direction θ of the radar transmission signal u b(θ u ) is expressed as a column vector having Nt elements as shown in the following equation (16), when the transmitting antennas are arranged linearly at equal intervals Dt.

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[0119] In addition, the azimuth direction θ uIt is a vector that changes within the azimuth range for arrival direction estimation at a predetermined azimuth interval β1.

[0120] <Step2-3: Transmission Antenna Discrimination Processing (TxSel)> The DDM separation / direction estimation unit 211 performs TxSel based on the maximum peak direction θmax(ndt) and the maximum peak power value Pmax(ndt) obtained by the direction estimation process for each of the first to Nt transmission antenna candidates. Here, ndt = 1 to Nt.

[0121] Here, in the direction estimation process result using the correct transmission antenna candidate, the direction vector V of the virtual receiving array at θmax(ndt) ab (θ u ) has the highest correlation. Also, in TxSel, the DDM separation / direction estimation unit 211 discriminates the transmission antenna candidate with the highest Pmax(ndt) obtained by the direction estimation process for each of the first to Nt transmission antenna candidates as the transmission antenna.

[0122] Hereinafter, among ndt = 1 to Nt, the transmission antenna candidate with the highest Pmax(ndt) is denoted as "transmission antenna candidate nmax". Also, the transmission antenna candidate with the highest Pmax(ndt) among the other transmission antenna candidates excluding the transmission antenna candidate nmax is denoted as "next-best transmission antenna candidate n" 2nd ". In the case where there are multiple transmission antenna candidates with equal Pmax(ndt), one of them can be regarded as the transmission antenna candidate nmax, and one of the remaining transmission antenna candidates can be denoted as the next-best transmission antenna candidate n 2nd as well.

[0123] Also, the DDM separation / direction estimation unit 211 calculates the likelihood (reliability, probability) of TxSel as follows. When the calculated likelihood is less than or equal to a predetermined likelihood value (threshold), the result of TxSel may be rejected, and subsequent positioning output may not be performed. Thereby, the effect of reducing the probability of false detection or false alarm by the radar device 10 can be obtained.

[0124] In the following description, an example in which the first likelihood and the second likelihood are used will be described. Note that the DDM separation / direction estimation unit 211 may use either the first likelihood or the second likelihood, or both the first likelihood and the second likelihood. When both the first likelihood and the second likelihood are used, an AND condition or an OR condition between the two may be used.

[0125] When the DDM separation / direction estimation unit 211 has determined the transmitting antenna candidate nmax in TxSel, the DDM separation / direction estimation unit 211 may use, for example, the following equation (17) as the first likelihood of TxSel.

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[0126] In equation (17), P max (nmax) and the next best transmitting antenna candidate n 2nd P in max (n 2nd ) and the first likelihood LH1(nmax,n 2nd ) is calculated. Here, the first likelihood LH1(nmax,n 2nd ) is 0≦LH1(nmax,n 2nd )≦1. P for the transmit antenna candidate nmax max (nmax) is the next best transmitting antenna candidate n 2nd P in max (n 2nd ), the greater the likelihood LH1(nmax,n 2nd ) is close to 1. Also, the likelihood LH1(nmax,n 2nd ) is closer to 1, the likelihood (reliability) of the transmitting antenna decision is considered to be higher.

[0127] For example, the DDM separation / direction estimation unit 211 calculates the first likelihood LH1(nmax,n 2nd ) with a predetermined value (for example, about 0.3 to 0.5), and the first likelihood LH1(nmax, n 2nd) is equal to or smaller than a predetermined value, the result of TxSel may be rejected and no further positioning output may be performed. This has the effect of reducing the probability of false detection or false alarm in the radar device 10. For example, when signals corresponding to a correct transmitting antenna candidate and an incorrect transmitting antenna candidate are received in the same phase or in approximately the same phase, P max (nmax) and the next best transmitting antenna candidate n 2nd P in max (n 2nd ) is calculated as a value of the same order. Therefore, the first likelihood LH1(nmax,n 2nd ) is 0 or close to 0, a low value is output as the likelihood (reliability) of TxSel. 2nd ) is equal to or smaller than a predetermined value, the result of TxSel is rejected and no further positioning output is performed, thereby achieving the effect of reducing the probability of false detection or false alarm in the radar device 10.

[0128] Furthermore, when the DDM separation / direction estimation unit 211 determines the transmitting antenna candidate nmax in TxSel, it may use, for example, the following equation (18) as the second likelihood LH2(nmax) of TxSel.

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[0129] For example, when Pmax(ndt) is calculated using equation (13), the second likelihood LH2(nmax) is output in the range of 0≦LH2(nmax)≦1. For example, θ max The direction vector V of the virtual receiving array at (ndt) ab (θ u ), the closer the second likelihood LH2(nmax) shown in equation (18) is to 1. In addition, the closer the second likelihood LH2(nmax) is to 1, the higher the likelihood (reliability) of the transmitting antenna decision can be considered to be.

[0130] For example, the DDM separation / direction estimation unit 211 may compare the second likelihood LH(nmax) with a predetermined value (for example, about 0.6 to 0.9), and if the second likelihood LH(nmax) is equal to or less than the predetermined value (equal to or less than the predetermined likelihood value), may reject the result of TxSel and not perform any further positioning output. This provides the effect of reducing the probability of false detection or false alarm in the radar device 10.

[0131] For example, when multiple targets exist in different directions in the same distance bin, the received signal components from the multiple targets are mixed. For example, when the received signal components from the multiple targets have the same reception level, the probability that TxSel cannot be performed correctly in the DDM separation / direction estimation unit 211 increases. In such a case, the second likelihood LH2(nmax,n 2nd ) is likely to be a value of about 0.5 or less, and the likelihood (reliability) of TxSel is output as a relatively low value. Also, for example, the more noise components are included in the received signal from the target, the higher the probability that TxSel cannot be performed correctly. In such a case, the second likelihood LH2(nmax,n 2nd ) is likely to be a value of about 0.5 or less, and a relatively low value is output as the likelihood (reliability) of TxSel. Furthermore, when the second likelihood LH(nmax) is a predetermined value or less, the DDM separation / direction estimation unit 211 rejects the result of TxSel and does not perform subsequent positioning output, thereby achieving the effect of reducing the probability of false detection or false alarm of the radar device 10.

[0132] In addition, the DDM separation / direction estimation unit 211 uses distance index information f b_cf and θ obtained by direction estimation processing for each nmax transmit antenna candidate. max (nmax), and P max (nmax) may be output as the positioning result.

[0133] In addition, the DDM separation / direction estimation unit 211 may detect the Doppler frequency of the target within the range of ±1 / (2Tr) based on the difference between the DF Index indicating the output of the Doppler analysis unit 209 corresponding to each Tx#1 to Tx#Nt indicated by the nmax-th transmitting antenna candidate vector DopTx(nmax,z) determined as the transmitting antenna in TxSel and the DS amount for each Tx#1 to Tx#Nt set in the DS setting unit 106 in the radar transmitter 100, and output the Doppler frequency as the positioning result.

[0134] In addition, the DDM separation / direction estimation unit 211 uses distance index information f b_cf (or, for example, distance information using equation (8)) may be output as the positioning result.

[0135] In FIG. 4, the DDM separation / direction estimation unit 211 performs the above-mentioned operations of Step 1 to Step 2 on the f of each of the multiple (for example, all) targets extracted by the CFAR unit 210. b_cf and DF Index(f sc_cf +(ndm-1)×ΔFD) to perform the same operation.

[0136] The DDM separation process (transmitting antenna discrimination) has been described above.

[0137] As described above, in this embodiment, the DDM separation / direction estimation unit 211 separates the multiplexed signals (DDM signals) from the reflected wave signal, and determines which of the transmitting antennas each of the separated signals corresponds to, based on the direction estimation result after correcting the phase deviation between the transmitting antennas for the separated signals. This allows the radar device 10 to accurately distinguish between correct transmitting antenna candidates and incorrect transmitting antenna candidates, thereby improving the accuracy of antenna identification.

[0138] [Example of power supply line 108] The radar device 10 according to this embodiment may apply a feeder line 108 having a line length that satisfies any of the following conditions for the feeder line 108 (e.g., referred to as "feeder line conditions") and conditions for the placement of the transmitting and receiving antennas (e.g., "transmitting and receiving antenna placement conditions"). This allows the radar device 10 to reduce errors in transmitting antenna determination and errors in detecting the Doppler frequency of a target. Furthermore, reducing errors in transmitting antenna determination and errors in detecting the Doppler frequency of a target improves the detection performance of the radar device 10.

[0139] Hereinafter, examples of the power supply line conditions and the effects obtained by satisfying the power supply line conditions will be described.

[0140] <Feed line condition (1): In the case of two transmitting antennas> The radar device 10 supplies power using feed lines 108 having a feed line length such that the line length difference (also referred to as feed line difference or feed line length difference, for example) between feed lines 108 connected to each of the two transmitting antennas in the transmitting antenna unit 109 is half the wavelength of the radar transmission signal or an odd multiple of half the wavelength (1.5 wavelengths, 2.5 wavelengths, etc.). For example, the phase deviation due to the line length difference between feed lines 108 connected to each of the two transmitting antennas is an odd multiple of π / 2.

[0141] As a result, in the radar device 10, power is fed using the feed lines 108 having different feed line lengths such that the phase deviation between the transmitting antennas is π / 2 or an odd multiple of π / 2.

[0142] <Feedline condition (2): When there are at least three transmitting antennas arranged in the same direction> The radar device 10 supplies power to a target direction in which the reception phases of signals transmitted from two of at least three transmitting antennas in a transmitting antenna unit 109 are in phase, using a feeder line 108 having a length such that the reception phases between any of the two transmitting antennas and the remaining transmitting antenna are not in phase.

[0143] The setting of the phase deviation between the above-mentioned transmitting antennas may include an error of about ±π / 10, and even in this case, a relatively high effect can be achieved similarly.

[0144] The radar device 10 has, for example, a transmission antenna interval and feeder line lengths L1 to L2 of the feeder lines 108 connected to the Tx#1 to #Nt, Nt The parameters are set so that the path difference within the radar viewing angle is an integer multiple of the wavelength and is not in phase.

[0145] For example, there is a method of making the phase deviation between the transmitting antennas as small as possible by wiring the power feed lines with equal lengths, making correction of the phase deviation between the transmitting antennas unnecessary or only fine adjustment, whereas in this embodiment, the line length of the power feed line 108 is made different between the transmitting antennas.

[0146] Alternatively, there is a method of transmitting radio waves of a specific polarization by feeding power with a specific phase difference between the transmitting antennas, in which case the radar device outputs the same transmission signal from the multiple transmitting antennas.In contrast, in this embodiment, the radar device 10 performs DDM transmission using different Doppler frequencies, and does not transmit using the same transmission signal.

[0147] An example of the feeder line condition (1) (when there are two transmitting antennas) will be described below.

[0148] [Example of power supply line condition (1)] For example, a signal R is a signal transmitted from the nt-th Tx#nt and reflected by a target in the direction θ by, for example, the na-th Rx#na among Rx#1 to #Na. na,nt (θ) is expressed as the following equation (19). Here, A na,nt (θ) represents a real amplitude response, and ξ(nt) represents the amount of phase rotation of the radar transmission signal occurring in the feed line 108 connected to the nt-th Tx#nt. na,nt (θ) represents the received phase caused by the path difference of the reflected wave from the target in the direction θ. na,nt(θ) does not include the phase difference due to the feed line difference.

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[0149] Here, in the case of a correct transmit antenna candidate, the correction coefficient Ct(ndt) for correcting the phase deviation between the transmit antennas is applied to the received signal R by TxCal (for example, Step 2-1 in Fig. 4). na,nt By multiplying it by (θ), the phase deviation due to the feed line length is correctly corrected as shown in the following equation (20). Note that, since the phase difference γ(nt,1)=ξ(nt)-ξ(1), the equation (20) includes e jξ(1) However, the radar device 10 performs direction estimation processing using the phase difference, so the phase difference ρ na,nt The target direction can be correctly detected based on (θ).

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[0150] For example, the radar device 10 may calculate the target direction θ based on the phase difference between the received signal corresponding to the signal from Tx#1 and the received signal corresponding to the signal from Tx#2, which are received at the n-th receiving antenna, as shown in the following equation (21).

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[0151] Here, D t represents the distance between the transmitting antennas Tx#1 and Tx#2.

number

number

[0152] On the other hand, in the case of an incorrect transmitting antenna candidate, the phase deviation caused by the feed line length is not correctly corrected by TxCal (e.g., Step 2-1 in FIG. 4). For example, when a received signal corresponding to a signal from Tx#1 received at the na-th receiving antenna is erroneously determined (or regarded) as a received signal from Tx#2, and a received signal corresponding to a signal from Tx#2 is erroneously determined as a received signal from Tx#1, the phase deviation caused by the feed line length is not correctly corrected by TxCal (e.g., Step 2-1 in FIG. 4), as shown in the following equations (22) and (23).

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number

[0153] In this case, the phase difference between the received signals after TxCal (eg, Step 2-1 in FIG. 4) is expressed by the following equation (24).

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[0154] In addition, when the correct transmitting antenna candidate and the incorrect transmitting antenna candidate are in phase, it is difficult to distinguish the transmitting antenna. For example, when the relationship of the following equation (25) is satisfied, the target direction θ c In this case, the correct transmitting antenna candidate and the incorrect transmitting antenna candidate have the same phase, making it difficult to distinguish the transmitting antenna.

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[0155] where m a is an integer value that satisfies the following equation (26).

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[0156] FIG. 5 shows the target direction θ where the received phases of the signals from Tx#1 and Tx#2 are the same, where Nt=2, and the horizontal axis represents the phase difference (ξ2-ξ1) between the feeder line lengths of the feeder line 108 of Tx#1 and the feeder line 108 of Tx#2, based on the above-mentioned formula. c The graphs are plotted with Dt=λ / 2 as the vertical axis. Fig. 5(a) shows an example where Dt=λ / 2, Fig. 5(b) shows an example where Dt=3λ / 4, and Fig. 5(c) shows an example where Dt=λ. Note that the same relationship will be obtained if an integer multiple of 2π is added to the horizontal axis of Fig. 5.

[0157] As shown in FIG. 5, the narrower the transmitting antenna spacing is, Dt=λ / 2, the closer the target direction θ c It can be seen that the viewing angle range not including

[0158] For example, in the case of Dt=λ / 2 shown in FIG. 5(a), when ξ2-ξ1=0 or π, ρ2(θ c )-ρ1(θ c )=0,π. For example, when the arrival angle of a target is θ c =0,±π / 2[rad](=0,±90[°]) and the phase is the same.

[0159] For example, in the case of Dt=λ / 2 shown in FIG. 5(a), when ξ2-ξ1=π / 2 (horizontal axis: 0.5), ρ2(θ c )-ρ1(θ c ) = ±π / 2. For example, if the arrival angle of a target is θ c = ±π / 6 [rad] (= ±30 [°]). Therefore, for example, in the case of Dt = λ / 2 shown in FIG. 5(a), the radar viewing angle θ FOV -π / 6<θ FOV If <π / 6, within the radar viewing angle, the reception phases corresponding to Tx#1 and Tx#2 do not have an in-phase relationship, and the radar device 10 is able to distinguish the transmitting antenna.

[0160] FIG. 6 shows Nt=2, the horizontal axis represents the phase difference (ξ2-ξ1) due to the difference in the length of the power feed line 108 connected to Tx#1 and the power feed line 108 connected to Tx#2, and the horizontal axis represents the target direction θ c The figure plots the vertical axis of the viewing angle that can secure the maximum positive and negative angle regions with the target direction θ=0° as the center, without including θ. Note that the same relationship will be obtained even if an integer multiple of 2π is added to the horizontal axis of FIG. 6.

[0161] As an example, Fig. 6 shows plots for Dt = λ / 2, Dt = 3λ / 4, and Dt = λ. As shown in Fig. 6, when the phase difference between the feeder lines 108 connected to Tx #1 and Tx #2 is π / 2, the viewing angle that can be secured to the maximum in both positive and negative angle regions centered on the target direction θ = 0° is maximized. Note that even if the phase difference between the feeder lines 108 is about 0.4 to 0.6π, a relatively wide viewing angle can be secured.

[0162] 6, when the phase difference between the feeder lines 108 connected to Tx#1 and Tx#2 is π / 2, the view angle that can be secured when Dt=λ / 2 is in the range of ±30°, when Dt=3λ / 4 is in the range of ±19.5°, and when Dt=λ is in the range of ±14.5°. Thus, the target direction θ where the received phases of the signals from Tx#1 and Tx#2 are in the same phase is narrowed to about Dt=λ / 2. c The viewing angle range not including the above can be expanded.

[0163] An example of the feeder line condition (1) has been described above.

[0164] [Receiving antenna placement conditions] In this embodiment, of the Na receiving antennas, at least two receiving antennas are arranged on a straight line in the direction in which the transmitting antennas are arranged (hereinafter referred to as the transmitting antenna arrangement direction).

[0165] For example, as shown in Fig. 7(a), Na=3 receiving antennas may be arranged with respect to Nt=2 transmitting antennas in the transmitting antenna arrangement direction (horizontal direction in Fig. 7) at intervals Dr=2Dt, for example. With the arrangement shown in Fig. 7(a), in addition to the arrangement position of the transmitting antenna in the transmitting antenna arrangement direction, a virtual receiving antenna is arranged at a position different from the position of the transmitting antenna. Therefore, the radar device 10 can detect the reception phase for the multiple transmitting antennas using the multiple receiving antennas at different positions in the transmitting antenna arrangement direction, and TxSel can be performed using the direction estimation process (Step 2-2 in Fig. 4) for each transmitting antenna candidate.

[0166] In this embodiment, at least two receiving antennas may be arranged in an oblique direction with respect to the direction in which the transmitting antennas are arranged. For example, as shown in FIG. 7B, three receiving antennas may be arranged in an oblique direction with an angle smaller than 90° (for example, a direction perpendicular to the direction in which the transmitting antennas are arranged) with respect to two transmitting antennas (horizontal direction in FIG. 7), and arranged at intervals Dr=2Dt in the direction in which the transmitting antennas are arranged. With the arrangement shown in FIG. 7B, in addition to the arrangement position of the transmitting antenna in the direction in which the transmitting antennas are arranged, a virtual receiving antenna is arranged at a position different from the position of the transmitting antenna. Therefore, the radar device 10 can detect the reception phases for the multiple transmitting antennas using the multiple receiving antennas at different positions in the direction in which the transmitting antennas are arranged, and a transmitting antenna discrimination process (TxSel) using a direction estimation process (Step 2-2 in FIG. 4) for each transmitting antenna candidate is possible.

[0167] In addition, in this embodiment, as shown in FIG. 7(c), if all the receiving antennas are arranged in a direction perpendicular to the transmitting antenna arrangement direction (horizontal in FIG. 7) (vertical in FIG. 7), the virtual receiving antenna arrangement has the same number of virtual receiving antennas as the transmitting antennas arranged in the transmitting antenna arrangement direction, and it may be difficult for the radar device 10 to detect whether the target direction is correct. For example, the receiving antennas may be arranged in an arrangement direction different from the direction perpendicular to the transmitting antenna arrangement direction, as shown in FIG. 7(a) or FIG. 7(b). The receiving antennas may be arranged in the transmitting antenna arrangement direction (for example, the example in FIG. 7(a)), or in an oblique direction different from the direction perpendicular to the transmitting antenna arrangement (for example, the example in FIG. 7(b)). This makes it possible to obtain the effects of this embodiment described above.

[0168] Next, an example of the feeder line condition (2) (when there are three or more transmitting antennas) will be described.

[0169] [Example of power supply line condition (2)] For example, in a target direction where received signals corresponding to signals transmitted from two transmitting antennas among multiple transmitting antennas Tx #1 to #Nt are in phase, a feeder line length is used such that the received signal corresponding to a signal transmitted from any of the two transmitting antennas is not in phase with the received signal corresponding to a signal transmitted from the remaining transmitting antenna.

[0170] For example, the case where Nt=3 (Tx#1, Tx#2, and Tx#3) will be described.

[0171] Element spacing Dt between Tx#1 and Tx#2 (2,1) The target direction θ that is in phase with c2,1 From equation (25), it is expressed by the following equation (27).

number

[0172] Similarly, the element spacing Dt (3,1) The target direction θ that is in phase with c3,1From equation (25), it is expressed by the following equation (28).

number

[0173] sinθ in equation (27) c2,1 and sinθ in equation (28) c2,1 The phase differences γ(2,1)=(ξ2-ξ1) and γ(3,1)=(ξ3-ξ1) may be set so that they do not match. This makes it possible to set the feeder line length such that the received signals of the signals transmitted from Tx#1 and Tx#3 are not in phase in the target direction where the received signals of the signals transmitted from Tx#1 and Tx#2 among the multiple Tx#1 to #3 are in phase.

[0174] In addition, when the received signal level is low (for example, when the received SNR (Signal to Noise Ratio) is low), it becomes more susceptible to noise, so sinθ c2,1 and sinθ c3,1 It is preferable to set the values ​​of and to be as different as possible, thereby reducing the probability of an error in the transmit antenna determination.

[0175] <Example 1> For example, when Nt=3 (for example, Tx#1, Tx#2, and Tx#3), the element spacing between Tx#1 and Tx#2 is Dt (2,1) = λ / 2 target direction θ c2,1 From equation (25), it is expressed by the following equation (29).

number

[0176] For example, the element spacing between Tx#1 and Tx#3 is Dt (3,1) = Target direction θ that is in phase with λ c3,1 From equation (25), it is expressed by the following equation (30).

number

[0177] For example, the feed line length of the feed lines 108 of Tx#1 and Tx#2 is a feed line length having a phase difference of γ(2,1)=π / 2, and the feed line length of the feed lines 108 of Tx#1 and Tx#3 is a feed line length having a phase difference of γ(3,1)=π / 2. In this case, formulas (29) and (30) are expressed by the following formulas (31) and (32).

number

number

[0178] The length of the feeder line 108 thus set is determined based on, for example, the target direction (e.g., θ c2,1 ), the received signals transmitted from Tx#1 and the remaining Tx#3 are in the target direction (for example, θ c2,1 ) is the length of the power supply line that does not become in-phase.

[0179] Also, for example, the target direction θ c2,1 and θ c3,1 For example, as shown in FIG. 8A, when γ(2,1)=γ(3,1)=π / 2, the received signals transmitted from Tx#1 and Tx#2 are in phase with each other, i.e., sinθ c2,1 and sinθ where the received signals of the signals transmitted from Tx#1 and Tx#3 are in phase. c3,1 There is a difference of ±1 / 4 between the sinθ c3,1 is 1 / 2 interval from equation (28), and sinθ c2,1 is the same phase as above, sinθ c3,1 In this way, the target direction θ c2,1 and θ c3,1 are as far apart as possible. The same relationship will be obtained if an integer multiple of 2π is added to the horizontal axis of Figure 8. The same level of performance can be ensured even if γ(2,1) = γ(3,1) = π / 2 ± π / 10.

[0180] The above can be summarized as follows:

[0181] For example, at least three transmitting antennas (including Tx#1 to Tx#3) are arranged on the same line, and the distance between Tx#1 and Tx#2 is Dt (2,1) The interval between Tx#1 and Tx#3 is Dt (2,1) Integer multiple of (at × Dt (2,1) ), and a case will be described in which the transmitting antenna spacing is in a relationship of at=2. In this case, the feed line length of the feed lines 108 of Tx#1 and Tx#2 may be a feed line length having a phase difference of γ(2,1)=π / 2. Also, the feed line length of the feed lines 108 of Tx#1 and Tx#3 may be a feed line length having a phase difference of γ(3,1)=π / 2.

[0182] Note that the same relationship is true not only for at=2, but also for at=4, 6, 8, and other even multiples.

[0183] In this case, the above-mentioned relationship is expressed by the following equations (33) and (34).

number

number

[0184] As a result, the target direction θ c2,1 In contrast, the received signals of the signals transmitted from Tx#1 and Tx#3 are in the target direction θ c2,1 In this case, the signals are not in phase, and the radar device 10 can determine the transmitting antenna.

[0185] In addition, the target direction θ c2,1 and the target direction θ where the received signals transmitted from Tx#1 and Tx#3 are in phase. c3,1This makes it possible to reduce the probability of erroneous transmission antenna determination, for example, even when the reception signal level is low (for example, when the reception SNR is low), and is less susceptible to the effects of noise and the like.

[0186] As described above, when the number of transmitting antennas is three or more, by setting the feeder line lengths of the feeder lines 108 connected to each transmitting antenna to the above values, the received signals transmitted from each transmitting antenna are not in phase in the target direction within a ±90° range. This enables the radar device 10 to distinguish transmitting antennas over a wide viewing angle range.

[0187] <Example 2> For example, when Nt=3 (for example, Tx#1, Tx#2, and Tx#3), the element spacing Dt (2,1) = λ / 2 target direction θ c2,1 From equation (25), it is expressed by the following equation (35).

number

[0188] For example, the element spacing Dt (3,1) = 3λ / 2, the target direction θ c3,1 is expressed by the following equation (36) based on equation (25).

number

[0189] For example, the feeder lines 108 of Tx#1 and Tx#2 have a feeder line length with a phase difference of γ(2,1)=π / 4 (or 3 / 4π), and the feeder lines 108 of Tx#1 and Tx#3 have a feeder line length with a phase difference of γ(3,1)=π / 4 (or 3 / 4π). In this case, formulas (35) and (36) are expressed by the following formulas (37) and (38).

number

number

[0190] The length of the feeder line 108 thus set is determined based on, for example, the target direction (e.g., θ c2,1 ), the received signals transmitted from Tx#1 and the remaining Tx#3 are in the target direction (for example, θ c2,1 ) is the length of the power supply line that does not become in-phase.

[0191] Also, for example, the target direction θ c2,1 and θ c3,1 For example, as shown in FIG. 8B, when γ(2,1)=γ(3,1)=π / 4 or 3 / 4π, the received signals transmitted from Tx#1 and Tx#2 are in phase with each other, i.e., sinθ c2,1 and sinθ where the received signals of the signals transmitted from Tx#1 and Tx#3 are in phase. c3,1 There is a difference of ±1 / 6 between the sinθ c3,1 is 1 / 3 interval from equation (28), and sinθ c2,1 is the same phase as above, sinθ c3,1 In this way, the target direction θ c2,1 and θ c3,1 are as far apart as possible. The same relationship will be obtained even if an integer multiple of 2π is added to the horizontal axis of Fig. 8. The same level of performance can be ensured even if γ(2,1) = γ(3,1) = π / 4 (or 3 / 4π) ± π / 10.

[0192] The above can be summarized as follows:

[0193] For example, at least three transmitting antennas (including, for example, Tx#1 to Tx#3) are arranged on the same line, and the distance between Tx#1 and Tx#2 is Dt (2,1) The interval between Tx#1 and Tx#3 is Dt (2,1) Integer multiple of (at × Dt (2,1)), and a case will be described in which the transmitting antenna spacing is in a relationship of at=3. In this case, the feed line length of the feed lines 108 of Tx#1 and Tx#2 may be a feed line length having a phase difference of γ(2,1)=π / 4 (or 3 / 4π). Also, the feed line length of the feed lines 108 of Tx#1 and Tx#3 may be a feed line length having a phase difference of γ(3,1)=π / 4 (or 3 / 4π).

[0194] In this case, the above-mentioned relationship is expressed by the following equations (39) and (40).

number

number

[0195] As a result, the target direction θ c2,1 In contrast, the received signals of the signals transmitted from Tx#1 and Tx#3 are in the target direction θ c2,1 In this case, the signals are not in phase, and the radar device 10 can determine the transmitting antenna.

[0196] In addition, the target direction θ c2,1 and the target direction θ where the received signals transmitted from Tx#1 and Tx#3 are in phase. c3,1 This makes it possible to reduce the probability of erroneous transmission antenna determination, for example, even when the reception signal level is low (for example, when the reception SNR is low), and is less susceptible to the effects of noise and the like.

[0197] As described above, when the number of transmitting antennas is three or more, by setting the feeder line lengths of the feeder lines 108 connected to each transmitting antenna to the above values, the received signals transmitted from each transmitting antenna are not in phase in the target direction within a ±90° range. This enables the radar device 10 to distinguish transmitting antennas over a wide viewing angle range.

[0198] The above describes an example of how the power supply line 108 is set.

[0199] As described above, in the present embodiment, in the radar device 10, the line length of the power feed line 108 is set so that the phase deviation due to the line length difference between the power feed lines 108 connected to at least two transmitting antennas (for example, the first transmitting antenna and the second transmitting antenna) is an odd multiple of π / 2. Alternatively, in the radar device 10, the line length of the power feed line 108 is set so that the phase deviation due to the line length difference between the power feed lines 108 connected to at least three transmitting antennas (for example, the first to third transmitting antennas) is an odd multiple of π / 4. In this way, by making the power feed line lengths of the power feed lines 108 connected to each transmitting antenna different, a phase difference occurs between the transmitting antennas, so that even when the target direction θ is (2πDt sinθ) / λ=±2nπ, the received phases of the reflected waves corresponding to the signals transmitted from the multiple transmitting antennas can be made different. This enables the radar device 10 to distinguish the transmitting antennas in the DDM separation / direction estimation unit 211. Here, Dt is the distance between the transmitting antennas, n is an integer value, and λ is the wavelength of the radar transmission wave.

[0200] Therefore, according to this embodiment, it is possible to improve the detection performance of a MIMO radar using DDM transmission.

[0201] Furthermore, in this embodiment, the phase deviation between the transmitting antennas is adjusted by setting the length of the power feed line 108 connected to the transmitting antennas, so that the radar device 10 does not need to change the settings of other parameters (e.g., parameters related to DDM transmission) to adjust the phase deviation.

[0202] In this embodiment, the line lengths of the feed lines 108 are set so that the phase deviation due to the line length difference between the feed lines 108 connected to the two transmitting antennas is an odd multiple of π / 2. However, since, for example, the longer the line length difference, the greater the power supply loss may be, it is preferable to set the phase deviation due to the line length difference between the feed lines 108 to π / 2.

[0203] In this embodiment, feeding lines of different lengths are used as feeding lines 108 to at least two transmitting antennas, and it is set so that different phase deviations occur between the transmitting antennas. However, the method of making the phase deviations between the transmitting antennas different is not limited to this, and for example, in phase rotation unit 107, the path length within phase rotation unit 107 may be made different, and in this case, the same effect can also be obtained. In this case, different phase deviations are added between the transmitting antennas at the output end of phase rotation unit 107.

[0204] (Embodiment 2) The radar device 10 according to the present embodiment may have a similar configuration to that of the first embodiment.

[0205] In the first embodiment, for example, in the case of two transmitting antennas, the radar device 10 receives the target reflected wave in phase in the target direction θ c As shown in equation (25), depends on the feed line length (for example, the phase difference ξ2-ξ1 between the feed line lengths) and the spacing Dt between the transmitting antennas. The feed line length and the spacing Dt between the transmitting antennas are parameters that are physically set and fixed, and the target direction θ c is a known direction.

[0206] In this embodiment, for example, the target direction θ in which the target reflected waves are received in phase is c In the embodiment, transmitting antennas having directional gains different from each other by a predetermined value or more are used. For example, in a direction in which the radar transmission signals transmitted from the first transmitting antenna and the second transmitting antenna included in the transmitting antenna unit 109 have the same reception phase as the received phase of the reflected wave signal reflected by the target, the directional gains between the first transmitting antenna and the second transmitting antenna differ by a predetermined value or more. This provides an effect of expanding the viewing angle at which transmitting antenna discrimination is possible compared to the first embodiment.

[0207] As an example, a case where the number of transmitting antennas is Nt=2 and the distance between transmitting antennas is Dt=λ / 2 will be described.

[0208] For example, when using the feeder lines 108 having different feeder line lengths such that the phase deviation between the transmitting antennas is about π / 2, the radar device 10 uses the target direction θ c In the direction of θ = ±30°, the target reflected waves for the signals transmitted from the two transmitting antennas are received in phase. In this way, when Dt and the phase deviation between the transmitting antennas (or the feed line length of the feed line 108) are set, the target reflected waves for the signals transmitted from the two transmitting antennas are received in phase and the target direction θ c is known.

[0209] In this embodiment, for example, two transmitting antennas Tx#1 and Tx#2 are used, the directivity gains of which in ±30° directions differ by a predetermined value or more (for example, about 2 dB to 6 dB).

[0210] For example, Fig. 9 shows an example of the directivity patterns of two transmitting antennas, Tx#1 and Tx#2. The directional beam width of each of the two transmitting antennas shown in Fig. 9 is 100°, the main beam direction of Tx#1 is the -15° direction, and the main beam direction of Tx#2 is the 15° direction. In this way, the main beam directions of Tx#1 and Tx#2 are different. By using multiple transmitting antennas having directivity patterns with shifted main beam directions, as shown in Fig. 9, the directional gain in the 30° direction or the -30° direction differs by about 2 dB between the transmitting antennas.

[0211] By using a plurality of transmitting antennas having such different directivity patterns, the radar device 10 receives target reflected waves in phase with respect to signals transmitted from Tx#1 and Tx#2, and detects the target direction θ c Therefore, the radar device 10 can distinguish the transmitting antenna based on the directional gain (or the received power) even when the viewing angle is wider than ±30°.

[0212] In the following, when the radar device 10 uses multiple transmitting antennas with different directivity patterns, operations different from those according to the first embodiment will be described, and operations similar to those according to the first embodiment will not be described. For example, in this embodiment, an example of the operation of the radar transmitter 100 of the radar device 10 is similar to that of the first embodiment, so a description of the operation will be omitted. In this embodiment, in the radar receiver 200 of the radar device 10, the operation of the DDM separation / direction estimation unit 211 differs from that of the first embodiment.

[0213] An example of the operation of DDM separation / direction estimation section 211 (for example, an operation different from that in the first embodiment) will be described below.

[0214] For example, among the operations of DDM separation / direction estimation section 211 according to the present embodiment, the operation of Step 2-3 (TxSel) of Step 2 (DDM separation processing (transmitting antenna discrimination)) in FIG.

[0215] For example, after performing TxSel in Step 2-3 described in the first embodiment, the DDM separation / direction estimation unit 211 performs θ max (nmax) is the target direction θ at which the target reflected wave is received in phase in the case of two transmitting antennas. c or, |θ max (nmax)-θ c | is a given value (e.g., δ θ ), perform TxSel including the following processing.

[0216] For example, in the case of two transmit antennas, N DM = 2. The DDM separation / direction estimation unit 211 calculates, for example, a VFT z (f b_cf , fddm(1)) and VFT z (f b_cf , fddm(2)) are compared. Note that the received power value may be the received power by any of Rx#1 to #Na, or may be the sum of the received power values ​​of multiple receiving antennas.

[0217] In addition, the θ c The directional gain of the transmitting antenna in the direction is set as "TxGain #1 (θ c ) and "TxGain #2 (θ c For example, the target direction θ c The directional gain of each transmitting antenna (TxGain #1 (θ c ) and TxGain #2 (θ c For example, in the example of Figure 9, θ c =-30°, TxGain #1 (-30°)>TxGain #2 (-30°) and θ c = 30°, TxGain #1 (30°) <TxGain #2 (30°).

[0218] Using such directivity conditions of the transmitting antenna, the DDM separation / direction estimation unit 211 performs the following transmitting antenna discrimination.

[0219] <Transmitting antenna discrimination (TxSel) using the directivity condition of the transmitting antenna> For example, the DDM separation / direction estimation unit 211 may max (nmax) is |θ max (nmax)-θ c |≦δ θ The condition of |VFT is satisfied. z (f b_cf ,fddm(1))| 2 >|VFT z (f b_cf ,fddm(2))| 2 If so, perform TxSel as in (1) and (2) below.

[0220] (1)TxGain #1 (θ c ) <TxGain #2 (θ cIn this case, the DDM separation / direction estimation unit 211 performs VFT z (f b_cf , fddm(1)) is the output of the received signal corresponding to Tx#2, and VFT z (f b_cf , fddm(2)) is determined to be the output of the received signal corresponding to Tx#1.

[0221] (2)TxGain #1 (θ c )>TxGain #2 (θ c In this case, the DDM separation / direction estimation unit 211 performs VFT z (f b_cf , fddm(1)) is the output of the received signal corresponding to Tx#1, and VFT z (f b_cf , fddm(2)) is determined to be the output of the received signal corresponding to Tx#2.

[0222] Also, for example, the DDM separation / direction estimation unit 211 may max (nmax) is |θ max (nmax)-θ c |≦δ θ The condition of |VFT is satisfied. z (f b_cf ,fddm(1))| 2 <|VFT z (f b_cf ,fddm(2))| 2 If so, perform TxSel as in (1) and (2) below.

[0223] (1)TxGain #1 (θ c ) <TxGain #2 (θ c In this case, the DDM separation / direction estimation unit 211 performs VFT z (f b_cf , fddm(1)) is the output of the received signal corresponding to Tx#1, and VFT z (f b_cf , fddm(2)) is determined to be the output of the received signal corresponding to Tx#2.

[0224] (2)TxGain #1 (θ c )>TxGain #2 (θ c In this case, the DDM separation / direction estimation unit 211 performs VFT z (f b_cf , fddm(1)) is the output of the received signal corresponding to Tx#2, and VFT z (f b_cf , fddm(2)) is determined to be the output of the received signal corresponding to Tx#1.

[0225] Here, θ c represents the target direction in which the target reflected waves from Tx#1 and Tx#2 are received in phase.

[0226] In addition, the above |VFT z (f b_cf ,fddm(1))| 2 , and |VFT z (f b_cf ,fddm(2))| 2 Instead of the above, the sum of the received powers by a plurality of receiving antennas shown in the following equation (41) may be used.

number

[0227] For example, when using the directivity pattern of the transmitting antenna shown in FIG. c = 30°, TxGain #1 (30°) <TxGain #2 (30°), so the θ of the candidate transmitting antenna max (nmax) is |θ max (nmax)-30°|≦δ θ The condition of |VFT is satisfied. z (f b_cf ,fddm(1))| 2 >|VFT z (f b_cf ,fddm(2))| 2 In this case, the DDM separation / direction estimation unit 211 performs VFT z (f b_cf ,fddm(1)) corresponds to Tx#2, and VFTz (f b_cf , fddm(2)) corresponds to Tx#1.

[0228] In addition, for example, when the directivity pattern of the transmitting antenna shown in FIG. c =-30°, TxGain #1 (-30°)>TxGain #2 (-30°), so the θ of the transmitting antenna candidate max (nmax) is |θ max (nmax)-(-30°)|≦δ θ The condition of |VFT is satisfied. z (f b_cf ,fddm(1))| 2 >|VFT z (f b_cf ,fddm(2))| 2 If so, the DDM separation / direction estimation unit 211 performs the VFT z (f b_cf ,fddm(1)) corresponds to Tx#1, and VFT z (f b_cf , fddm(2)) corresponds to Tx#2.

[0229] Note that TxSel using the above-mentioned directivity conditions of the transmitting antenna may be performed using likelihood information in combination.

[0230] Moreover, according to the present embodiment, by adding TxSel using the directivity condition of the transmitting antenna, it is possible to obtain an effect that the viewing angle at which the transmitting antenna can be distinguished can be further expanded compared to the first embodiment.

[0231] By the above-mentioned receiving process, in this embodiment, the radar device 10 uses transmitting antennas whose directional gains in the target direction where the target reflected waves of the signals transmitted from the transmitting antennas are received in phase within a predetermined viewing angle differ by a predetermined value or more, thereby obtaining an effect of further expanding the viewing angle in which the transmitting antennas can be distinguished.

[0232] (Embodiment 3) The TxSel by the DDM separation / direction estimation unit 211 of the above-mentioned first embodiment may cause an error in identifying the transmitting antenna in the following cases: In such cases, an error in reception separation of the DDM transmission signal may occur, causing an error in the Doppler frequency estimation or direction estimation result, which may degrade the detection performance of the radar.

[0233] <Case 1> When two target reflected waves arrive at the same distance index (hereinafter also referred to as distance bin) at an interval equal to the DDM interval, during the direction estimation process for each transmitting antenna candidate in Step 2-2 of Figure 4, the maximum peak power value varies depending on the relationship in at least one of the amplitude and phase between the reflected waves from the two targets, which may cause an error in TxSel and result in an error in direction estimation or Doppler frequency detection.

[0234] <Case 2> When two targets with different arrival angles are included in the same distance bin and the same DF index (hereinafter also referred to as Doppler bin), during the direction estimation process for each transmitting antenna candidate in Step 2-2 of Figure 4, the maximum peak power value varies depending on the relationship between at least one of the amplitude and phase between the reflected waves from the two targets, which may cause an error in TxSel and an error in the direction estimation or Doppler frequency detection.

[0235] In this embodiment, a method of sending a transmission signal that enables the radar device 10 to correctly separate the DDM signal even in the above-mentioned case will be described.

[0236] The radar device according to this embodiment has a basic configuration in common with the radar device 10 shown in Fig. 2, and will be described with reference to Fig. 2. For example, in this embodiment, the operations of the DS setting unit 106, the Doppler analysis unit 209, the CFAR unit 210, and the DDM separation / direction estimation unit 211 in the radar device 10 shown in Fig. 2 are different from those in the first embodiment.

[0237] In this embodiment, for example, the radar device 10 variably sets at least one of the number of DS amounts (e.g., the number of DDMs) and the interval of the DS amounts, which are set for transmitting a radar transmission signal, for each transmission cycle in which the radar transmission signal is transmitted. For example, the radar device 10 variably sets the number of DDMs and variably sets each interval of the DS amounts for each transmission cycle, and changes the allocation of DDMs to transmitting antennas.

[0238] For example, in DDM, if the reception levels of the Doppler peaks of multiple targets are approximately equal and the spacing between the Doppler peaks matches the spacing between the DS amounts, it may become difficult for the DDM separation / direction estimation unit 211 to correctly detect TxSel (Case 1 described above).

[0239] In this embodiment, we will explain two cases: 1) the number of DDMs is made variable and each interval of the DS amount is set variable for each transmission cycle, and 2) the number of DDMs is not made variable and each interval of the DS amount is set variable, in order to more reliably separate multiple targets in the positioning output of the radar device 10. According to this embodiment, since the intervals of Doppler peaks corresponding to multiple transmitting antennas for one target differ for each transmission cycle, the radar device 10 can easily separate multiple targets in one radar observation, which is a countermeasure for Case 1.

[0240] Hereinafter, an example of a method for setting the amount of DS added in DS setting section 106 will be described as a method for setting the amount of phase rotation in phase rotation amount setting section 105 according to this embodiment.

[0241] The DS setting unit 106 sets the DS amount DOP ndm The amount of phase rotation φ for adding ndm Here, ndm=1~N DM N DMis the number of different DS amounts (DDM number), and in this embodiment, in order to more reliably separate multiple targets in the positioning output of the radar device 10, when the DDM number is varied for each transmission period, the transmission period includes a transmission period in which transmission is performed using a portion of the number of transmission antennas. Therefore, depending on the transmission period, the DDM number N DM may be set to a number greater than or equal to 1 and less than Nt.

[0242] In addition, the DS setting unit 106 sets the DS amount DOP for each Tr. ndm For example, the number of DDMs N DM When variable, the number of DDMs for each odd-numbered Tr is N DM "N DM odd " and the number of DDMs for each even-numbered Tr is N DM "N DM even " respectively.

[0243] Here, Nt ≥ N DM odd ≧1, Nt≧N DM even ≧1. Note that N DM odd ≠N DM even It may be N DM odd =N DM even The number of DDMs, N DM odd Or N DM even Depending on the transmission period, Nt may be set to a number smaller than Nt. In such a case, the radar device 10 transmits the radar transmission signal using a part of the transmission antenna.

[0244] In the following, Tx#1 to Tx#N DM odd Or Tx#1~Tx#N DM even However, the present invention is not limited to this, and the number of transmitting antennas and the number of DDMs N DMBy using an allocation table with the DDM indexes assigned by the user, it is possible to assign DDM indexes using any transmit antenna.

[0245] In addition, the DS setting unit 106 sets the DS amount DOP for each odd-numbered Tr. ndm odd , and the DS amount DOP for every even-numbered Tr ndm even Set the following respectively.

[0246] The period for variable setting of the DS amount is not limited to two transmission periods, and may be set to vary the DS amount every three transmission periods. In this case, the DS setting unit 106 sets three types of DS amounts to be used every three transmission periods.

[0247] An example of the settings in the DS setting unit 106 will be described below.

[0248] [Example 1] In setting example 1, a case will be described in which the number of DDMs is set variable every two transmission periods (2Tr) and each interval of the DS amount is set variable.

[0249] For example, the number of transmitting antennas (or the number of DDMs) to which the DS amount is assigned may be different between odd-numbered transmission periods and even-numbered transmission periods among the multiple transmitting antennas included in the transmitting antenna unit 109. In this case, at least one identical DS amount may be set in the odd-numbered transmission periods and the even-numbered transmission periods.

[0250] For example, when the maximum equal interval DS amount setting shown in formula (5) is used, the DS setting unit 106 sets the DS amount DOP for every odd-numbered Tr according to the following formula (42) for the ndm-th DS amount. ndm odd The phase rotation amount φ corresponding to ndm odd (where ndm=1~N DM odd ), according to equation (43), the DS amount DOP for every even-numbered Tr ndm even The phase rotation amount φ corresponding tondm even (where ndm=1~N DM even ).

number

number

[0251] Here, N DM odd and N DM even is a positive number equal to or greater than 1 and is set to a different value. Therefore, the DS amount DOP for each odd-numbered Tr is ndm odd And the DS amount DOP for every even numbered Tr ndm even This causes each interval of the DS amount to be variably set for each Tr.

[0252] The amount of phase rotation φ n is not limited to the value shown in formula (5), and the DS amount DOP ndm odd and DS amount DOP ndm even Any phase rotation amount may be used as long as the intervals between the DS amounts are different. For example, the DS amount may be set with an offset. Also, the allocation of the DS amount index may be variable. Also, the DS amounts with unequal intervals shown in equation (6) may be used.

[0253] The DS setting unit 106 sets the DS amount DOP ndm odd The amount of phase rotation φ ndm odd Using this, the PS amount ψ shown in the following equation (44) is ndm odd (m) is set and output to the phase rotation unit 107. Here, m=1 to Nc, ndm=1 to N DM odd It is.

number

[0254] In addition, the DS setting unit 106 sets the DS amount DOP in the m-th Tr when m is an even number. ndm even The amount of phase rotation φ ndm even Using this, the PS amount ψ shown in the following equation (45) is ndm even (m) is set and output to the phase rotation unit 107. Here, m=1 to Nc, ndm=1 to N DM even It is.

number

[0255] An example of DS settings for setting example 1 is shown below.

[0256] In the example shown in FIG. 10, in an odd-numbered transmission period (hereinafter, referred to as odd Tr), the DDM number N DM odd = 4, and the maximum equal interval DS amount setting shown in equation (5) is applied. On the other hand, in an even transmission period (hereinafter, referred to as even Tr), the number of DDMs N DM even = 3 is set, and the maximum equal interval DS amount setting is applied. As a result, in Fig. 10, radar transmission signals are transmitted by DDM from four transmission antennas in the odd Tr and from three transmission antennas in the even Tr.

[0257] In the example shown in FIG. 11, in the odd Tr, the number of DDMs N DM odd = 2 and the maximum equal interval DS amount setting is applied. On the other hand, in the even Tr, the number of DDMs N DM even = 1, and the DS amount is set to zero. As a result, in Fig. 11, in the odd Tr, the radar transmission signal is transmitted using multiple (e.g., two) transmission antennas, and in the even Tr, the radar transmission signal is transmitted using one transmission antenna.

[0258] In the example shown in FIG. 12, in the odd Tr, the number of DDMs is N DM odd = 4 is set, and the maximum equal interval DS amount setting is applied. On the other hand, in the even Tr, the number of DDMs N DM even = 3 is set, and the non-uniform DS amount setting shown in formula (6) (where N int =1) is applied. As a result, in Fig. 12, radar transmission signals are DDM transmitted from four transmitting antennas in the odd Tr, and radar transmission signals are DDM transmitted from three transmitting antennas in the even Tr. Also, in Fig. 12, the DS amounts allocated to Tx1, Tx#2, and Tx#3 are the same in both the odd Tr and the even Tr.

[0259] [Example 2] In setting example 2, a case will be described in which the number of DDMs is constant and each interval of the DS amount is set variably every two transmission periods (2Tr).

[0260] For example, when the maximum equal interval DS amount setting shown in equation (5) is used for every odd-numbered Tr, the DS setting unit 106 sets the DS amount DOP for every odd-numbered Tr according to equation (42) for the ndm-th DS amount. ndm odd The phase rotation amount φ corresponding to ndm odd (where ndm=1~N DM ).

[0261] Then, in the m-th Tr, when m is an odd number, the DS setting unit 106 sets the DS amount DOP ndm odd The amount of phase rotation φ ndm odd Using this, the PS amount ψ shown in equation (44) ndm odd (m) is set and output to the phase rotation unit 107. Here, N DM odd =N DM even =N DM where m = 1 ~ Nc, ndm = 1 ~ NDM It is.

[0262] On the other hand, the DS setting unit 106 sets the DS amount DOP for every even-numbered Tr. ndm even The phase rotation amount φ corresponding to ndm even For example, the following setting example 2-1, setting example 2-2, or setting example 2-3 is used (where ndm=1 to N DM ).

[0263] <Setting example 2-1> For example, when the non-uniform DS amount setting shown in formula (6) is used for every even-numbered Tr, the DS setting unit 106 sets the DS amount DOP for every even-numbered Tr according to the following formula (46) for the ndm-th DS amount: ndm even The phase rotation amount φ corresponding to ndm even (where ndm=1~N DM ), where N int is an integer value.

number

[0264] In addition, the DS setting unit 106 sets the DS amount DOP in the m-th Tr when m is an even number. ndm even The amount of phase rotation φ ndm even Using this, the PS amount ψ shown in equation (45) ndm even (m) is set and output to the phase rotation unit 107. Here, m=1 to Nc, ndm=1 to N DM It is.

[0265] FIG. 13 shows a DS setting example of setting example 2-1.

[0266] In the example shown in FIG. 13, in odd Tr, the number of DDMs is N DM odd= 3, and the maximum equal interval DS amount setting shown in equation (5) is applied. On the other hand, in the even Tr, the number of DDMs N DM even = 3 is set, and the non-uniform DS amount setting shown in formula (6) (where N int =1) is applied.

[0267] In this manner, in FIG. 13, in odd Tr, the DS amounts are spaced at equal intervals on the Doppler frequency axis, and in even Tr, the DS amounts are spaced at unequal intervals on the Doppler frequency axis.

[0268] <Setting example 2-2> In setting example 2-2, a setting example where Nt=2 will be described.

[0269] For example, when the equal-interval DS amount setting shown in equation (5) is used for every even-numbered Tr for the first Tx#1, the DS setting unit 106 sets the DS amount DOP1 for every even-numbered Tr according to the following equation (47): even The phase rotation amount φ1 corresponding to even Here, ndm fix ndm=1~N DM Any one of these may be selected and used in a fixed manner.

number

[0270] In addition, for the first DS amount, for example, in the m-th Tr, when m is an even number, the DS setting unit 106 sets the DS amount DOP1 even The phase rotation amount φ1 even Using this, the PS amount ψ1 shown in equation (45) even (m) is set and output to phase rotation section 107, where m=1 to Nc.

[0271] The DS setting unit 106 applies the following phase rotation to the second DS amount, for example, to the second Tx#2, and generates two DDM signals.

[0272] For example, the DS setting unit 106 sets two DS amount DOPs for the second Tx#2 for the second DS amount. 2-1 and DOP 2-2 In order to give the chirp signal a phase rotation of Φ2 even Add (m)=phseq[mod(floor((m-1) / 2),4)+1] and output.

[0273] Here, phseq[ps] represents the ps-th element of phseq=[0,0,π,π]. For example, phseq[1]=phseq[2]=0, and phseq[3]=phase[4]=π. Also, mod(x,y) is a remainder calculation function that represents the remainder when x is divided by y. Note that, since two DDM signals are generated for Tx#2, the DS amount DOP 2-1 and DS amount DOP 2-2 The power is divided in two.

[0274] The example of generating two DDM signals is not limited to the above example, and two DDM signals can be generated using, for example, phseq=[0,π / 2,0,π / 2],[0,-π / 2,0,-π / 2],[π,-π / 2,π,-π / 2], or [π,π / 2,π,π / 2]. Furthermore, for example, when two DDM signals are generated for one transmitting antenna, the other transmitting antenna may transmit using a DDM signal that does not match these DDM signals.

[0275] FIG. 14 shows a DS setting example of setting example 2-2.

[0276] In the example shown in FIG. 14, in odd Tr, the number of DDMs N DM odd = 2, and the maximum equal interval DS amount setting shown in equation (5) is applied. On the other hand, in the even Tr, the number of DDMs N DM even =2 is set, DS amount zero is set for Tx#1, and phase rotation using phseq=[0,0,π,π] is set for Tx#2.

[0277] Thus, in FIG. 14, in the odd Tr, one DS amount is assigned to each of Tx#1 and Tx#2, and in the even Tr, one DS amount is assigned to Tx#1 and multiple DS amounts are assigned to Tx#2.

[0278] <Setting example 2-3> In setting example 2-3, a case will be described in which the DS amounts for all transmitting antennas are set to the same amount for every even-numbered Tr.

[0279] For example, when the equal interval DS amount setting shown in formula (5) is used, the DS setting unit 106 sets the DS amount DOP for every even-numbered Tr according to the following formula (48) for the ndm-th DS amount. ndm even The phase rotation amount φ corresponding to ndm even Here, ndm fix ndm=1~N DM Any one of these may be selected and used in a fixed manner.

number

[0280] In addition, the DS setting unit 106 sets the DS amount DOP in the m-th Tr when m is an even number. ndm even The amount of phase rotation φ ndm even Using this, the PS amount ψ shown in equation (45) ndm even (m) is set and output to the phase rotation unit 107. Here, m=1 to Nc, ndm=1 to N DM It is.

[0281] FIG. 15 shows a DS setting example of setting example 2-3.

[0282] In FIG. 15, in odd Tr, the number of DDMs N DM odd= 2, and the maximum equal interval DS amount setting shown in equation (5) is applied. On the other hand, in the even Tr, the number of DDMs N DM even =2 is set, and the DS amount is set to zero for Tx#1 and Tx#2.

[0283] In this way, in FIG. 15, different DS amounts are assigned to multiple transmitting antennas in an odd Tr, and the same DS amount is assigned to multiple transmitting antennas in an even Tr.

[0284] The above describes an example of settings in the DS setting unit 106.

[0285] When the DS setting unit 106 applies a phase rotation amount to a radar transmission signal (for example, a chirp signal), if a phase rotation error is included, spurious may occur in the Doppler frequency domain. Here, for example, if the spurious level is about -20 dB or less compared to the Doppler peak level, there is no significant degradation effect on the radar detection performance of the radar device 10. Therefore, as a phase rotation error during phase rotation, a phase rotation error in which the spurious level is within a range of about -20 dB or less compared to the Doppler peak (for example, a range of about 5° to 10°) may be included. Note that in other embodiments (or variations), similarly, a phase rotation error in which the spurious level is within a range of about -20 dB or less compared to the Doppler peak (for example, a range of about 5° to 10°) may be included.

[0286] [Example of operation of radar receiver 200] Next, the radar reception processing in this embodiment will be described, mainly focusing on the operations that differ from those in the first embodiment.

[0287] [Example of operation of Doppler analyzer 209] In FIG. 2, the Doppler analysis unit 209 analyzes N C Using the beat frequency response obtained by transmitting chirp pulses once, the distance index f b Doppler analysis is performed every 10 minutes.

[0288] In this embodiment, for a radar transmission signal (for example, a chirp signal), the number of DDMs is set to be variable or constant for every two transmission periods (2Tr), and each interval of the DS amount is set to be variable. In this case, the phase rotation φ of the DS amount setting that differs between odd-numbered Tr and even-numbered Tr is set to be ndm Therefore, the Doppler analysis unit 209 calculates f by using the beat frequency response for each odd-numbered Tr. b Similarly, the Doppler analysis unit 209 performs a Doppler analysis for every even-numbered Tr. b Doppler analysis is performed every 10 minutes.

[0289] For example, the Doppler analysis unit 209 performs FFT processing based on data obtained every odd-numbered or even-numbered Tr (for example, every 2Tr). In this case, the FFT size is Nc / 2. Therefore, the maximum Doppler frequency at which aliasing does not occur, which is derived from the sampling theorem, is ±1 / (4Tr). In addition, the DF Index f s The Doppler frequency interval of DF Index f s The range of f s =-N c / 4,~,0,~,Nc c / 4-1.

[0290] For example, in the z-th signal processing unit 206, the output VFT of the Doppler analysis unit 209 for the beat frequency response for each odd-numbered Tr is z odd (f b ,f s ), and the output VFT of the Doppler analysis unit 209 for the beat frequency response for each even-numbered Tr z even (f b ,f s ) is expressed by the following equation (49), where j is the imaginary unit and z=1 to Na.

number

[0291] [Example of operation of CFAR section 210] In FIG. 2, the CFAR unit 210 performs CFAR processing (for example, adaptive threshold determination) using the output from the Doppler analysis unit 209 of the first to Na-th signal processing units 206, and calculates f b_cf and DF Index f s_cf Extract.

[0292] The CFAR unit 210 calculates, for example, the output VFT of the Doppler analysis unit 209 for the beat frequency response for each odd-numbered Tr. z odd (f b ,f s ) is subjected to CFAR processing to adaptively set a threshold value and obtain a received power greater than the threshold value f b_cf odd , DF Index f s_cf odd , and the received power information PowerFT odd (f b_cf odd ,f s_cf odd ) to the DDM separation / direction estimation unit 211.

[0293] In addition, the CFAR unit 210 calculates, for example, the output VFT of the Doppler analysis unit 209 of the first to Na-th signal processing units 206. z odd (f b ,f s ) are power-added, and two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity) or a CFAR processing combining one-dimensional CFAR processing is performed.

[0294] DOP ndm odd The amount of phase rotation φ for adding ndm For example, when equation (5) is used, the intervals of the DS amount in the Doppler frequency domain in the output of the Doppler analysis unit 209 are equal, and when the interval ΔFD of the DS amount is expressed by the interval of the DF index, ΔFD is expressed as follows: odd =Nc / (2N DM oddTherefore, in the output of the Doppler analysis unit 209, in the Doppler frequency domain, ΔFD odd Peaks are detected at intervals of .

[0295] Therefore, the CFAR unit 210 calculates each output VFT of the Doppler analysis unit 209. z odd (f b ,f s ) for the DS amount interval ΔFD odd Then, for each divided range, the power of each DDMed signal peak position is added as shown in the following equation (50), and then DC-CFAR is performed. Here, f sc =-ΔFD odd / 2,~,(ΔFD odd / 2)-1.

number

[0296] The CFAR unit 210 using DC-CFAR adaptively sets a threshold value, for example, and calculates f b_cf odd , f sc_cf odd , and N DM odd DF Index(f sc_cf odd +(ndm-1) × ΔFD odd ) received power information PowerFT(f b_cf odd ,f sc_cf odd +(ndm-1) × ΔFD odd ), and the output VFT of the Doppler analysis unit 209 z (f b_cf odd ,f sc_cf odd +(ndm-1) × ΔFD odd ) to the DDM separation / direction estimation unit 211. Here, ndm=1, ∼, N DM odd It is.

[0297] Similarly, the CFAR unit 210 adaptively sets a threshold value by performing CFAR processing on, for example, the output VFT of the Doppler analysis unit 209 for the beat frequency response every even-numbered Tr, and the f z even (f b , f s ) at which the received power is greater than the threshold value, the DF Index f b_cf even , and the received power information PowerFT s_cf even are output to the DDM separation / direction estimation unit 211. even (f b_cf even , f s_cf even )

[0298] Also, the CFAR unit 210 using DC-CFAR performs similar processing in which "odd" in the description for the above odd-numbered transmission periods is read as "even".

[0299] [Operation example of DDM separation / direction estimation unit 211] Next, an operation example of the DDM separation / direction estimation unit 211 shown in FIG. 2 will be described.

[0300] Note that hereinafter, an example of the processing of the DDM separation / direction estimation unit 211 when DC-CFAR is used in the CFAR unit 210 will be described.

[0301] [When using setting example 1 in DS setting unit 106] When using setting example 1 in the DS setting unit 106, for example, every 2 transmission periods (2Tr), the number of DDMs is variably set, and each interval of the DS amount is variably set. In this case, a phase rotation φ ndm is given to the DS amount for every odd-numbered Tr and the DS amount for every even-numbered Tr, which are different settings.

[0302] Therefore, setting example 1 can be a countermeasure for the above-mentioned case 1. For example, even if two target reflected waves arrive at an interval equal to the DDM interval in either an even-numbered transmission period or an odd-numbered transmission period, the radar device 10 can detect two target reflected waves at an interval different from the DDM interval in the other even-numbered or odd-numbered transmission period.

[0303] DDM separation / direction estimation section 211 performs DDM separation processing and direction estimation processing on the DDM signal, for example, by the same operation as in the first embodiment.

[0304] For example, the DDM separation / direction estimation unit 211 receives f b_cf odd , f sc_cf odd , and N DM odd The received power information at the DF index of each DDM signal and the output VFT of the Doppler analysis unit 209 of the first to Nath signal processing units 206 z odd (f b ,f s ) to N DM odd The DDM separation / direction estimation unit 211 separates the DDM transmitted signals and performs TxSel together with direction estimation processing. Furthermore, the DDM separation / direction estimation unit 211 outputs the Doppler frequency (for example, Doppler velocity or relative velocity) and the direction estimation processing result based on the result of TxSel.

[0305] Similarly, the DDM separation / direction estimation unit 211 performs the same processing as above, substituting "even" for "odd."

[0306] Since the Doppler analysis unit 209 performs FFT processing based on data obtained every odd-numbered or even-numbered Tr (for example, every 2Tr), the Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is in the range of ±1 / (4Tr).

[0307] Here, for example, the DDM separation / direction estimation unit 211 can determine whether aliasing is included or not by utilizing the fact that the same transmitting antenna is included in each of the odd-numbered and even-numbered Tr. For example, in the setting example shown in Fig. 10, Tx#1 to Tx#3 are included in both the odd-numbered Tr and the even-numbered Tr. For example, the DDM separation / direction estimation unit 211 uses the output VFT of the Doppler analysis unit 209 of the 1st to Nath signal processing unit 206 in the DF Index of Tx#1 to Tx#3. z odd (f b ,f s ) and VFT z even (f b ,f s ) the presence or absence of aliasing can be detected. This makes it possible to detect the Doppler frequency of a target within the range of ±1 / (2Tr).

[0308] Also, for example, in the setting example shown in FIG. 11, the DDM number 1 is set for Tx#1 in the even Tr. Therefore, the DDM separation / direction estimation unit 211 can identify the signal detected in the even Tr as the signal corresponding to Tx#1, and can determine TxSel without error. For example, the DDM separation / direction estimation unit 211 can determine TxSel in the even Tr without error by using the DF Index information of Tx#1. For example, even in the above-mentioned case 2, the effect of being able to determine TxSel without error can be obtained by using the transmitting antenna determination result in the even Tr, so this can be a countermeasure for case 2.

[0309] 11, Tx#1 is included in both odd Tr and even Tr. For example, the DDM separation / direction estimation unit 211 calculates the output VFT of the Doppler analysis unit 209 of the first to Na-th signal processing units 206 in the DF Index of Tx#1. z odd (f b ,f s ) and VFT z even (f b ,f sBy comparing the phases with , the presence or absence of folding can be detected. As a result, the Doppler frequency of the target can be detected within the range of ±1 / (2Tr).

[0310] Also, for example, in the setting example shown in FIG. 12, at even Tr, Tx#1 to Tx#3 are set to DDM number 3 and are non-uniformly spaced DDM. For example, the separate reception of DDM signals using non-uniformly spaced DDM can be separated using existing techniques (see, for example, Patent Document 4). The DDM separation / direction estimation unit 211 may perform TxSel, for example, based on the separation result using existing techniques. Also, the DDM separation / direction estimation unit 211 may use this TxSel result for the TxSel result of another transmission period (for example, odd Tr in FIG. 12). In this case, even in the case of Case 2 described above, by using the transmission antenna determination result at even Tr, the effect of reducing the error of TxSel can be obtained, which can be a countermeasure for Case 2.

[0311] Also, for example, in the setting example shown in FIG. 12, Tx#1 to Tx#3 are included in both odd Tr and even Tr. For example, the DDM separation / direction estimation unit 211 outputs the VFT of the Doppler analysis unit 209 of the first to Na-th signal processing units 206 in the DF Index of Tx#1 to Tx#3 z odd (f b ,f s ) and VFT z even (f b ,f s ) By comparing the phases with , the presence or absence of folding can be detected. As a result, the Doppler frequency of the target can be detected within the range of ±1 / (2Tr).

[0312] <When using Setting Example 2-1 in the DS setting unit 106> When using Setting Example 2-1 in the DS setting unit 106, for example, the DDM number is fixed, and each interval of the DS amount is variably set every two transmission periods (2Tr). In this case, a phase rotation φ ndm is given.

[0313] Therefore, setting example 2-1 can be a countermeasure for the above-mentioned case 1. For example, even if two target reflected waves arrive at an interval equal to the DDM interval in either an even-numbered transmission period or an odd-numbered transmission period, the radar device 10 can detect two target reflected waves at an interval different from the DDM interval in the other even-numbered or odd-numbered transmission period.

[0314] For example, the DDM separation / direction estimation unit 211 performs DDM separation processing and direction estimation processing on the DDM signal by the same operation as when setting example 1 is used in the DS setting unit 106 .

[0315] Since the Doppler analysis unit 209 performs FFT processing based on data obtained every odd-numbered or even-numbered Tr (for example, every 2Tr), the Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is in the range of ±1 / (4Tr).

[0316] Here, for example, the DDM separation / direction estimation unit 211 can determine whether aliasing is included or not by utilizing the fact that the same transmitting antenna is included in each of the odd-numbered and even-numbered Tr. For example, in the setting example shown in FIG. 13, Tx#1 to Tx#3 are included in both the odd-numbered Tr and the even-numbered Tr. For example, the DDM separation / direction estimation unit 211 uses the output VFT of the Doppler analysis unit 209 of the 1st to Nath signal processing unit 206 in the DF Index of Tx#1 to Tx#3. z odd (f b ,f s ) and VFT z even (f b ,f s By comparing the phase between the target and the Doppler frequency, the presence or absence of aliasing can be detected. This makes it possible to detect the Doppler frequency of the target within the range of ±1 / (2Tr).

[0317] Also, in Setting Example 2-1, non-uniform DDM is used in a certain transmission period. For example, in the setting example shown in FIG. 13, Tx#1 to Tx#3 use non-uniform DDM with a DDM number of 3 at even Tr. For example, the separated reception of DDM signals using non-uniform DDM can be separated using existing technologies (for example, Patent Document 4). The DDM separation / direction estimation unit 211 may perform TxSel, for example, based on the separation result using existing technologies. Further, the DDM separation / direction estimation unit 211 may use this TxSel result for the TxSel result of another transmission period (for example, odd Tr in FIG. 13). In this case, even in the case of Case 2 described above, by using the transmission antenna determination result at even Tr, the effect of reducing the error of TxSel can be obtained, which can be a countermeasure for Case 2.

[0318] <When using Setting Example 2-2 in the DS setting unit 106> When using Setting Example 2-2 in the DS setting unit 106, for example, the number of DDMs is fixed, and each interval of the DS amount is variably set every two transmission periods (2Tr). In this case, a phase rotation φ ndm is given to the DS amount for each odd-numbered Tr and the DS amount for each even-numbered Tr. Therefore, Setting Example 2-2 can be a countermeasure for Case 2 described above.

[0319] For example, the DDM separation / direction estimation unit 211 performs DDM separation processing and direction estimation processing on the DDM signal by the same operation as in the case of using Setting Example 1 in the DS setting unit 106.

[0320] Note that since the Doppler analysis unit 209 performs FFT processing based on the data obtained for each odd-numbered or even-numbered Tr (for example, every 2Tr), the Doppler frequency without folding derived from the sampling theorem is in the range of ±1 / (4Tr).

[0321] Here, for example, the DDM separation / direction estimation unit 211 can determine whether aliasing is included or not by utilizing the fact that the same transmitting antenna is included in each of the odd-numbered and even-numbered Tr. For example, in the setting example shown in FIG. 14, Tx#1 is included in both the odd Tr and the even Tr. The DDM separation / direction estimation unit 211 can determine whether aliasing is included or not by utilizing the output VFT of the Doppler analysis unit 209 of the 1st to Nath signal processing units 206 in the DF index of Tx#1. z odd (f b ,f s ) and VFT z even (f b ,f s By comparing the phase between the target and the Doppler frequency, the presence or absence of aliasing can be detected. This makes it possible to detect the Doppler frequency of the target within the range of ±1 / (2Tr).

[0322] Also, in the setting example 2-2, non-uniform DDM is used in a certain transmission cycle. For example, in the setting example shown in FIG. 14, Tx#1 and Tx#2 use non-uniform DDM with a DDM number of 3 in the even Tr. For example, separation and reception of DDM signals using non-uniform DDM can be performed using existing technology (for example, Patent Document 4). The DDM separation / direction estimation unit 211 may perform TxSel based on the separation result using the existing technology, for example. Also, the DDM separation / direction estimation unit 211 may use this TxSel result for the TxSel result of another transmission cycle (for example, odd Tr in FIG. 14). In this case, even in the above-mentioned case 2, by using the transmitting antenna determination result in the even Tr, the effect of reducing TxSel errors can be obtained, which can be a countermeasure for case 2.

[0323] Setting example 2-2 can be a countermeasure for the above-mentioned case 1. For example, even if two target reflected waves arrive at an interval equal to the DDM interval in either an even-numbered transmission period or an odd-numbered transmission period, the radar device 10 can detect two target reflected waves at an interval different from the DDM interval in the other even-numbered or odd-numbered transmission period.

[0324] <When using Setting Example 2-3 in the DS Setting Unit 106> When using Setting Example 2-3 in the DS Setting Unit 106, for example, the number of DDMs is fixed, and each interval of the DS amount is variably set every two transmission periods (2Tr). In this case, a phase rotation φ ndm is applied, where the DS amount for every odd-numbered Tr is different from that for every even-numbered Tr.

[0325] Therefore, Setting Example 2-3 can be a countermeasure for Case 1 described above. For example, even when two target reflected waves with an interval equal to the DDM interval arrive in either the even-numbered transmission period or one of the odd-numbered transmission periods, the radar device 10 can detect the two target reflected waves in the other transmission period (either even or odd).

[0326] For example, the DDM separation / direction estimation unit 211 performs DDM separation processing and direction estimation processing on the DDM signal in the same manner as when using Setting Example 1 in the DS Setting Unit 106.

[0327] Also, for example, in the setting example shown in FIG. 15, in even Tr, Tx#1 and Tx#2 use one DDM. Therefore, the DDM separation / direction estimation unit 211 can make a determination without misidentifying TxSel. For example, the DDM separation / direction estimation unit 211 can make a determination without misidentifying TxSel in even Tr by using the DF Index information of Tx#1 and Tx#2. For example, even in the case of Case 2 described above, by using the transmission antenna determination result in even Tr, the effect of being able to make a determination without misidentifying TxSel can be obtained, which can be a countermeasure for Case 2.

[0328] Also, for example, in the setting example shown in FIG. 17, Tx#1 is included in both odd Tr and even Tr. Also, in odd Tr, Tx#1 and Tx#2 use different DDM signals. For example, the DDM separation / direction estimation unit 211 uses the outputs VFT of the Doppler analysis units 209 of the first to Na-th signal processing units 206 in the DF Index of Tx#1 and Tx#2 z odd (f b ,f s) and VFT z even (f b ,f s ) the presence or absence of aliasing can be detected. This makes it possible to detect the Doppler frequency of a target within the range of ±1 / (2Tr).

[0329] The radar reception process in this embodiment has been described above.

[0330] In the present embodiment, as an example, a case has been described in which a different Doppler multiplex number and a different Doppler shift amount are set for each transmission cycle, but the present invention is not limited to this. In order to more reliably separate multiple targets in the positioning output of the radar device 10, the Doppler shift amount may be variably set for each radar observation.

[0331] In the present embodiment, the radar device 10 performs the operation according to the first or second embodiment, but the present invention is not limited to this. For example, the radar device 10 may perform the operation according to the present embodiment without performing the operation according to the first or second embodiment (or the setting of the power feed line 108).

[0332] The embodiments of the present disclosure have been described above.

[0333] [Other embodiments] In the radar device according to the embodiment of the present disclosure, the radar transmitter and the radar receiver may be disposed separately in physically separate locations. Also, in the radar receiver according to the embodiment of the present disclosure, the Doppler demultiplexing / direction estimation unit 211 and other components may be disposed separately in physically separate locations.

[0334] In the above-described embodiment, an example has been described in which the viewing angle of the radar device 10 is set to an angular region centered on the target direction θ=0°. However, the viewing angle of the radar device 10 is not limited to an angular region centered on the target direction θ=0°.

[0335] In addition, the number of transmitting antennas Nt, the number of receiving antennas Na, the transmitting antenna intervals Dt and Dr, and the Doppler multiplexing number N DM The numerical values ​​of the parameters, such as the Doppler shift amount, the Doppler shift interval, and the value related to the phase rotation, are merely examples and are not limited to these values. In addition, for example, some of the transmitting antennas equipped in the radar device may be used as the number of transmitting antennas Nt, and some of the receiving antennas equipped in the radar device may be used as the number of receiving antennas Na.

[0336] Furthermore, although not shown, the radar device according to an embodiment of the present disclosure includes, for example, a central processing unit (CPU), a storage medium such as a read only memory (ROM) storing a control program, and a working memory such as a random access memory (RAM). In this case, the functions of each of the above-mentioned units are realized by the CPU executing the control program. However, the hardware configuration of the radar device is not limited to this example. For example, each functional unit of the radar device may be realized as an integrated circuit (IC). Each functional unit may be individually implemented as a single chip, or may be implemented as a single chip that includes some or all of the functional units.

[0337] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or amended examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure. In addition, the components in the above embodiments may be arbitrarily combined within the scope of the disclosure.

[0338] In addition, the notation "... part" in the above-mentioned embodiments may be replaced with other notations such as "... circuitry", "... assembly", "... device", "... unit", or "... module".

[0339] In each of the above embodiments, the present disclosure has been described as an example configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

[0340] Moreover, each functional block used in the description of each of the above embodiments is typically realized as an LSI, which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiments and may have input terminals and output terminals. These may be individually integrated into one chip, or may be integrated into one chip that includes some or all of them. Here, the term LSI is used, but depending on the degree of integration, it may also be called an IC, a system LSI, a super LSI, or an ultra LSI.

[0341] The method of integration is not limited to LSI, but may be realized using a dedicated circuit or a general-purpose processor. A field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections or settings of circuit cells inside the LSI may also be used.

[0342] Furthermore, if a new integrated circuit technology that can replace LSI appears due to the progress of semiconductor technology or a derivative technology, it is possible to integrate the functional blocks using that technology. The application of biotechnology is also a possibility.

[0343] <Summary of this disclosure> A radar device according to an embodiment of the present disclosure includes a plurality of transmitting antennas including a first transmitting antenna connected to a first feed line and a second transmitting antenna connected to a second feed line different from the first feed line, and a transmitting circuit that multiplexes and transmits, from the plurality of transmitting antennas, a transmission signal to which a phase rotation amount corresponding to a Doppler shift amount has been imparted, wherein a phase deviation due to a line length difference between the first feed line and the second feed line is an odd multiple of π / 2.

[0344] In one embodiment of the present disclosure, the line length difference is a half wavelength of the transmission signal or an odd multiple of the half wavelength.

[0345] In one embodiment of the present disclosure, the multiple transmitting antennas further include a third transmitting antenna connected to a third feed line, and a phase deviation due to a line length difference between the first feed line and the second feed line further includes an odd multiple of π / 4, and a phase deviation due to a line length difference between the first feed line and the third feed line is an odd multiple of π / 4.

[0346] In one embodiment of the present disclosure, the system further includes a plurality of receiving antennas that receive reflected wave signals of the transmitted signals reflected by a target, and a receiving circuit that separates the multiplexed signals from the reflected wave signals and determines whether each of the separated signals corresponds to the first transmitting antenna or the second transmitting antenna based on a direction estimation result after correcting the phase deviation for the separated signals.

[0347] In one embodiment of the present disclosure, the multiple receiving antennas include a first receiving antenna and a second receiving antenna, and the first receiving antenna and the second receiving antenna are arranged in a straight line in a direction in which the first transmitting antenna and the second transmitting antenna are arranged.

[0348] In one embodiment of the present disclosure, in a direction in which the received phases of reflected wave signals of signals transmitted from the first transmitting antenna and the second transmitting antenna reflected by a target are in phase, a directional gain between the first transmitting antenna and the second transmitting antenna differs by a predetermined value or more.

[0349] In one embodiment of the present disclosure, the first transmitting antenna and the second transmitting antenna have different main beam directions.

[0350] In an embodiment of the present disclosure, at least one of the number of the Doppler shift amounts and the interval of the Doppler shift amounts set for transmission of the transmission signal is set variably for each transmission period in which the transmission signal is transmitted.

[0351] In an embodiment of the present disclosure, the number of transmitting antennas to which the Doppler shift amounts are assigned among the plurality of transmitting antennas differs between odd-numbered transmission periods and even-numbered transmission periods.

[0352] In one embodiment of the present disclosure, at least one identical Doppler shift amount is set in the odd-numbered transmission periods and the even-numbered transmission periods.

[0353] In one embodiment of the present disclosure, in either the odd-numbered transmission period or the even-numbered transmission period, the transmission signal is transmitted using the multiple transmission antennas, and in the other transmission period of the odd-numbered transmission period or the even-numbered transmission period, the transmission signal is transmitted using one of the multiple transmission antennas.

[0354] In one embodiment of the present disclosure, in either the odd-numbered transmission cycles or the even-numbered transmission cycles, the intervals of the Doppler shift amounts are equal on the Doppler frequency axis, and in the other of the odd-numbered transmission cycles and the even-numbered transmission cycles, the intervals of the Doppler shift amounts are unequal on the Doppler frequency axis.

[0355] In one embodiment of the present disclosure, in either one of the odd-numbered transmission cycles or the even-numbered transmission cycles, one Doppler shift amount is assigned to each of the first transmitting antenna and the second transmitting antenna, and in the other of the odd-numbered transmission cycles or the even-numbered transmission cycles, one Doppler shift amount is assigned to the first transmitting antenna and multiple Doppler shift amounts are assigned to the second transmitting antenna.

[0356] In one embodiment of the present disclosure, in either an odd-numbered transmission period or an even-numbered transmission period, different Doppler shift amounts are assigned to the multiple transmitting antennas, and in the other of the odd-numbered transmission period and the even-numbered transmission period, the same Doppler shift amount is assigned to the multiple transmitting antennas.

[0357] A radar device according to one embodiment of the present disclosure includes a plurality of transmitting antennas and a transmitting circuit that multiplexes, from the plurality of transmitting antennas, transmission signals to which a phase rotation amount corresponding to a Doppler shift amount has been imparted, and at least one of the number of the Doppler shift amounts set for transmission of the transmission signals and the interval between the Doppler shift amounts set for the multiplexing is variably set for each transmission period in which the transmission signals are transmitted.

[0358] In one embodiment of the present disclosure, the Doppler shift amounts are spaced at equal intervals.

[0359] In one embodiment of the present disclosure, the transmission period includes a transmission period in which the Doppler shift amounts are spaced at equal intervals, and a transmission period in which the Doppler shift amounts are spaced at unequal intervals. [Industrial Applicability]

[0360] The present disclosure is suitable for a radar device that detects a wide angle range. [Explanation of symbols]

[0361] 10 Radar Equipment 100 Radar transmitter 101 Radar transmission signal generator 102 Transmission signal generation control section 103 Modulation signal generator 104 VCO 105 Phase rotation amount setting section 106 Doppler shift setting section 107 Phase Rotation Unit 108 Power Supply Line 109 Transmitting antenna section 200 Radar receiver 201 Antenna system processing unit 202 Receiving antenna section 203 Receiving Radio Unit 204 Mixer section 205 LPF 206 Signal Processing Section 207 AD conversion section 208 Beat Frequency Analysis Section 209 Doppler Analysis Unit 210 CFAR Department 211 Doppler demultiplexing / direction estimation unit

Claims

1. a plurality of transmitting antennas including a first transmitting antenna connected to a first feed line and a second transmitting antenna connected to a second feed line different from the first feed line; a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, transmission signals to which a phase rotation amount corresponding to the Doppler shift amount has been added; Equipped with a phase deviation due to a line length difference between the first feed line and the second feed line is an odd multiple of π / 2; Radar equipment.

2. the line length difference is a half wavelength of the transmission signal or an odd multiple of the half wavelength; The radar device according to claim 1 .

3. the plurality of transmitting antennas further includes a third transmitting antenna connected to a third feed line; the phase deviation due to the line length difference between the first feed line and the second feed line further includes an odd multiple of π / 4; a phase deviation due to a line length difference between the first feed line and the third feed line is an odd multiple of π / 4; The radar device according to claim 1 .

4. a plurality of receiving antennas for receiving reflected wave signals resulting from the transmission signals being reflected by targets; a receiving circuit that separates the multiplexed signals from the reflected wave signal, and determines whether each of the separated signals corresponds to the first transmitting antenna or the second transmitting antenna based on a direction estimation result after correcting the phase deviation for the separated signals. The radar device according to claim 1 .

5. the plurality of receiving antennas includes a first receiving antenna and a second receiving antenna; the first receiving antenna and the second receiving antenna are arranged on a straight line in a direction in which the first transmitting antenna and the second transmitting antenna are arranged. The radar device according to claim 4.

6. a difference in directional gain between the first transmitting antenna and the second transmitting antenna by a predetermined value or more in a direction in which the received phases of reflected wave signals of signals transmitted from the first transmitting antenna and the second transmitting antenna reflected by a target are in phase; The radar device according to claim 1 .

7. The first transmitting antenna and the second transmitting antenna have different main beam directions. The radar device according to claim 6.

8. At least one of the number of Doppler shift amounts and the interval of the Doppler shift amounts set for transmission of the transmission signal is variably set for each transmission cycle in which the transmission signal is transmitted. The radar device according to claim 1 .

9. the number of transmitting antennas to which the Doppler shift amounts are assigned differs between odd-numbered transmission periods and even-numbered transmission periods; The radar device according to claim 8.

10. At least one of the Doppler shift amounts is set to be the same in the odd-numbered transmission periods and the even-numbered transmission periods. The radar device according to claim 9.

11. In one of the odd-numbered transmission cycles and the even-numbered transmission cycles, the transmission signal is transmitted using the multiple transmission antennas, and in the other of the odd-numbered transmission cycles and the even-numbered transmission cycles, the transmission signal is transmitted using one transmission antenna of the multiple transmission antennas. The radar device according to claim 9.

12. In one of the odd-numbered transmission periods and the even-numbered transmission periods, the intervals of the Doppler shift amounts are equal on the Doppler frequency axis, and in the other of the odd-numbered transmission periods and the even-numbered transmission periods, the intervals of the Doppler shift amounts are unequal on the Doppler frequency axis. The radar device according to claim 9.

13. In one of the odd-numbered transmission cycles and the even-numbered transmission cycles, one Doppler shift amount is assigned to each of the first transmission antenna and the second transmission antenna, and in the other of the odd-numbered transmission cycles and the even-numbered transmission cycles, one Doppler shift amount is assigned to the first transmission antenna and a plurality of Doppler shift amounts are assigned to the second transmission antenna. The radar device according to claim 9.

14. different Doppler shift amounts are assigned to the plurality of transmitting antennas in either the odd-numbered transmission cycles or the even-numbered transmission cycles, and the same Doppler shift amount is assigned to the plurality of transmitting antennas in the other transmission cycle of the odd-numbered transmission cycles or the even-numbered transmission cycles. The radar device according to claim 8.

15. a plurality of transmitting antennas; a transmission circuit that multiplexes and transmits, from the plurality of transmission antennas, transmission signals to which a phase rotation amount corresponding to the Doppler shift amount has been added; Equipped with At least one of the number of the Doppler shift amounts set for the transmission of the transmission signal and the interval of the Doppler shift amounts set for the multiplex transmission is variably set for each transmission period in which the transmission signal is transmitted. Radar equipment.

16. The Doppler shift amounts are spaced at equal intervals. The radar device according to claim 15.

17. a transmission cycle in which the Doppler shift amounts are spaced at regular intervals and a transmission cycle in which the Doppler shift amounts are spaced at irregular intervals, The radar device according to claim 15.

18. Applying a phase rotation amount corresponding to the Doppler shift amount to a transmission signal, multiplexing the transmission signals from a plurality of transmission antennas; A transmission method for a radar device, comprising: The plurality of transmitting antennas a first transmitting antenna connected to a first feed line and a second transmitting antenna connected to a second feed line different from the first feed line; a phase deviation due to a line length difference between the first feed line and the second feed line is an odd multiple of π / 2; Radar device transmission method.

19. At least one of the number of Doppler shift amounts and the interval of the Doppler shift amounts set for transmission of the transmission signal is set variably for each transmission period in which the transmission signal is transmitted. The radar transmission method according to claim 18.

20. Among the plurality of transmitting antennas, the number of transmitting antennas to which the Doppler shift amount is assigned differs between odd-numbered transmission periods and even-numbered transmission periods.

20. The radar transmission method according to claim 19.

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