JP7117557B2 - radar equipment - Google Patents

Description

The present disclosure relates to radar equipment.

2. Description of the Related Art In recent years, studies have been made on radar devices using short-wavelength radar transmission signals including microwaves or millimeter waves that can provide high resolution. Also, in order to improve outdoor safety, there is a demand for the development of a radar device (wide-angle radar device) that detects small objects such as pedestrians and falling objects in a wide-angle range in addition to vehicles.

As a configuration of a radar system with a wide detection range, an array antenna consisting of multiple antennas (antenna elements) receives reflected waves, and the reflected waves are processed by a signal processing algorithm based on the reception phase difference with respect to the element spacing (antenna spacing). This is a configuration using a method of estimating the arrival angle (arrival direction) of (Direction of Arrival (DOA) estimation). For example, the method for estimating the angle of arrival includes the Fourier method (FFT (Fast Fourier Transform) method), or the Capon method, MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) as methods for obtaining high resolution. ).

Further, as a radar device, for example, in addition to the receiving side, a plurality of antennas (array antennas) are provided on the transmitting side, and beam scanning is performed by signal processing using the transmitting and receiving array antennas (MIMO (Multiple Input Multiple Output) radar is also called) has been proposed (see, for example, Non-Patent Document 1).

JP 2008-304417 A Japanese Patent Publication No. 2011-526371

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

However, methods for detecting target objects (or targets) in radar devices (for example, MIMO radar) have not been sufficiently studied.

One aspect of the present disclosure provides a radar device capable of accurately detecting a target.

A radar apparatus according to an aspect of the present disclosure includes a plurality of transmitting antennas and a transmitting circuit that transmits a transmission signal using the plurality of transmitting antennas, and based on the plurality of receiving antennas and the plurality of transmitting antennas, At least two of the virtual receiving arrays including a plurality of virtual antennas configured in the same arrangement position, and from the transmitting antennas corresponding to the at least two virtual antennas among the plurality of transmitting antennas Transmission intervals of the transmission signals that are sequentially transmitted are equal intervals.

In addition, these generic or specific aspects may be realized by systems, devices, methods, integrated circuits, computer programs, or recording media. may be realized by any combination of

According to one aspect of the present disclosure, it is possible to accurately estimate a direction of arrival in a radar device.

Further advantages and advantages of one aspect of the present disclosure are apparent from the specification and drawings. Such advantages and/or advantages are provided by the several embodiments and features described in the specification and drawings, respectively, not necessarily all provided to obtain one or more of the same features. no.

1 is a block diagram showing a configuration example of a radar device according to an embodiment; FIG. FIG. 4 is a diagram showing an example of a radar transmission signal according to one embodiment; A diagram showing an example of transmission switching operation according to an embodiment FIG. 3 is a block diagram showing another configuration example of the radar transmission signal generator according to one embodiment; A diagram showing an example of transmission timing and measurement range of a radar transmission signal according to an embodiment. A diagram showing an example of transmission timing according to an embodiment A diagram showing an example of transmission timing according to an embodiment A diagram showing an example of transmission timing according to an embodiment A diagram showing an example of an antenna arrangement according to an embodiment A diagram showing an example of reception timing for each virtual antenna according to an embodiment A diagram showing an example of an arrangement of transmitting antennas according to an embodiment A diagram showing an example of a receiving antenna arrangement according to an embodiment A diagram showing an example of a virtual reception array arrangement according to an embodiment A diagram showing an example of reception timing for each virtual antenna according to an embodiment A diagram showing an example of transmission timing according to Variation 1 of an embodiment A diagram showing another example of transmission timing according to variation 1 of one embodiment A diagram showing another example of transmission timing according to variation 1 of one embodiment A diagram showing an example of an antenna arrangement according to Variation 2 of an embodiment. A diagram showing an example of transmission timing according to variation 2 of one embodiment A diagram showing another example of antenna arrangement according to variation 2 of one embodiment A diagram showing an example of an antenna arrangement according to Variation 3 of an embodiment. A diagram showing another example of antenna arrangement according to Variation 3 of one embodiment. A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. FIG. 10 is a diagram showing an example of transmission switching operation according to variation 4 of one embodiment; A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. FIG. 10 is a diagram showing an example of transmission switching operation according to variation 4 of one embodiment; A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. FIG. 10 is a diagram showing an example of transmission switching operation according to variation 4 of one embodiment; A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. A diagram showing an example of an antenna arrangement according to Variation 4 of an embodiment. FIG. 10 is a diagram showing an example of transmission switching operation according to variation 4 of one embodiment; Block diagram showing a configuration example of a radar device according to variation 5 Block diagram showing a configuration example of a radar device according to variation 6 A diagram showing an example of a transmitted signal and a reflected wave signal when a chirped pulse is used

In MIMO radar, for example, signals (radar transmission waves) multiplexed using time division, frequency division, or code division are transmitted from a plurality of transmission antennas (or called transmission array antennas), and signals reflected by surrounding objects ( Radar reflected waves) are received using a plurality of receiving antennas (or called receiving array antennas), and multiplexed transmission signals are separated and received from the respective received signals. Through such processing, the MIMO radar can extract the complex channel response indicated by the product of the number of transmitting antennas and the number of receiving antennas, and performs array signal processing on these received signals as a virtual receiving array.

Moreover, in the MIMO radar, by appropriately arranging the element intervals in the transmitting and receiving array antennas, it is possible to virtually enlarge the antenna aperture and improve the angular resolution.

For example, Patent Document 1 discloses a MIMO radar multiplex transmission method using time-division multiplex transmission (hereinafter referred to as "time-division multiplex MIMO radar") in which signals are transmitted by shifting the transmission time for each transmission antenna. ) is disclosed. Time division multiplex transmission can be realized with a simpler configuration than frequency multiplex transmission or code multiplex transmission. In addition, time-division multiplex transmission can maintain good orthogonality between transmission signals by sufficiently widening the interval of transmission time. A time-division multiplex MIMO radar outputs a transmission pulse, which is an example of a transmission signal, while sequentially switching transmission antennas at a predetermined cycle. In a time-division multiplex MIMO radar, a signal of a transmitted pulse reflected by an object is received by a plurality of receiving antennas. process).

The time-division multiplex MIMO radar sequentially switches transmission antennas for transmitting transmission signals (for example, transmission pulses or radar transmission waves) at predetermined intervals. Therefore, time-division multiplexing can take longer to finish transmitting transmission signals from all transmit antennas than frequency-division or code-division transmission. For this reason, for example, as in Patent Document 2, when transmitting transmission signals from each transmission antenna and detecting the Doppler frequency (that is, the relative velocity of the target) from the change in the received phase, in order to detect the Doppler frequency In applying Fourier frequency analysis to , the time interval (for example, the sampling interval) for observing the received phase change is lengthened. Therefore, the Doppler frequency range in which the Doppler frequency can be detected without aliasing (that is, the relative velocity range of the target that can be detected) is reduced.

In addition, when a reflected wave signal from a target exceeding the Doppler frequency range (in other words, relative velocity range) in which the Doppler frequency can be detected without folding is assumed, the radar device identifies whether the reflected wave signal is a folding component. cannot, resulting in ambiguity of the Doppler frequency (in other words, relative velocity of the target).

For example, when a radar apparatus transmits a transmission signal (transmission pulse) while sequentially switching Nt transmission antennas at a predetermined cycle Tr, Tr×Nt is required by the time the transmission signals are completely transmitted from all the transmission antennas. Sending time is required. When such time-division multiplexing is repeated Nc times and Fourier frequency analysis is applied to detect the Doppler frequency, the Doppler frequency range in which the Doppler frequency can be detected without aliasing is ±1/(2Tr× Nt). Therefore, the Doppler frequency range in which the Doppler frequency can be detected without aliasing decreases as the number of transmitting antennas Nt increases, and Doppler frequency ambiguity tends to occur even at lower relative velocities.

Here, one method for expanding the Doppler frequency range (in other words, the relative velocity range or the maximum value of the relative velocity) is to use one transmitting antenna (one branch) and not form a virtual receiving array. In this method, the transmission time (transmission period) of Tr×Nt can be shortened by one transmission antenna (Nt=1), so that the Doppler frequency range (or the maximum value of relative velocity) can be expanded. However, with this method, the antenna aperture area becomes small, and the accuracy of distance or azimuth separation and estimation decreases.

Another method for expanding the Doppler frequency range (or the maximum value of relative velocity) is to use one transmitting antenna (one branch) and widen the element spacing of the receiving antenna. In this method, the transmission time (transmission period) of Tr×Nt can be shortened by one transmission antenna (Nt=1), so that the Doppler frequency range (or the maximum value of relative velocity) can be expanded. Furthermore, by widening the element spacing of the receiving antenna, the antenna aperture area can be increased. However, in this method, grating lobes become large due to the element spacing of the receiving antenna, and erroneous detection (for example, generation of ghosts) increases.

Therefore, in one aspect of the present disclosure, the Doppler frequency range (or the maximum value of the relative velocity) in which folding does not occur (in other words, ambiguity does not occur) while suppressing the reduction of the antenna aperture area or the increase of the grating lobe A method for enlarging will be explained. Accordingly, in one aspect of the present disclosure, the radar device 10 can accurately detect a target in a wider Doppler frequency range.

Hereinafter, embodiments according to one aspect of the present disclosure will be described in detail with reference to the drawings. In addition, in the embodiments, the same constituent elements are denoted by the same reference numerals, and redundant description thereof will be omitted.

In the following, in the radar device, the transmission branch transmits different transmission signals that are time-division multiplexed from a plurality of transmission antennas, and the reception branch separates each transmission signal and performs reception processing (in other words, MIMO radar configuration) will be explained.

[Configuration of radar device]
FIG. 1 is a block diagram showing the configuration of a radar device 10 according to this embodiment.

The radar device 10 has a radar transmission section (transmission branch) 100 , a radar reception section (reception branch) 200 and a reference signal generation section 300 .

The radar transmission unit 100 generates a high-frequency (radio frequency) radar signal (radar transmission signal) based on the reference signal received from the reference signal generation unit 300 . Radar transmission section 100 transmits a radar transmission signal at a predetermined transmission cycle using a transmission array antenna composed of a plurality of transmission antennas 108-1 to 108-Nt.

Radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a receiving array antenna including a plurality of receiving antennas 202-1 to 202-Na. The radar receiver 200 performs processing in synchronization with the radar transmitter 100 by performing the following processing operations using the reference signal received from the reference signal generator 300 . The radar receiver 200 also performs signal processing on reflected wave signals received by the respective receiving antennas 202, and, for example, detects the presence or absence of a target or estimates the direction of arrival of the reflected wave signal.

A target is an object to be detected by the radar device 10, and includes, for example, vehicles (including four-wheeled vehicles and two-wheeled vehicles), people, blocks, curbs, and the like.

The reference signal generator 300 is connected to each of the radar transmitter 100 and the radar receiver 200 . The reference signal generation unit 300 supplies a reference signal as a reference signal to the radar transmission unit 100 and the radar reception unit 200 to synchronize the processing of the radar transmission unit 100 and the radar reception unit 200 .

[Configuration of radar transmission unit 100]
Radar transmission section 100 includes radar transmission signal generation section 101, switching control section 105, transmission switching section 106, transmission radio sections 107-1 to 107-Nt, and transmission antennas 108-1 to 108-Nt. have. That is, the radar transmission section 100 has Nt transmission antennas 108 , and each transmission antenna 108 is connected to an individual transmission radio section 107 .

The radar transmission signal generator 101 generates a timing clock by multiplying the reference signal received from the reference signal generator 300 by a predetermined number, and generates a radar transmission signal based on the generated timing clock. Then, the radar transmission signal generator 101 repeatedly outputs the radar transmission signal at a predetermined radar transmission cycle (Tr). A radar transmission signal is represented by y(k, M)=I(k, M)+j Q(k, M). Here, j represents an imaginary unit, k represents a discrete time, and M represents an ordinal number of a radar transmission period. Also, I(k, M) and Q(k, M) are the in-phase component (In-Phase component) and quadrature component of the radar transmission signal (k M) at discrete time k in the M-th radar transmission cycle (Quadrature component) respectively.

Radar transmission signal generator 101 includes code generator 102 , modulator 103 , and LPF (Low Pass Filter) 104 . Each component in the radar transmission signal generator 101 will be described below.

Specifically, the code generating section 102 generates a code a _n (M) (n=1, . For the code a _n (M) generated in the code generating section 102, for example, a code that provides low-range sidelobe characteristics is used. Examples of code sequences include Barker codes, M-sequence codes, and Gold codes.

Modulation section 103 performs pulse modulation (amplitude modulation, ASK (Amplitude Shift Keying), pulse shift keying) or phase modulation (Phase Shift Keying) on a pulse code sequence (for example, code a _n (M)) received from code generation section 102 keying), and outputs the modulated signal to the LPF 104 .

LPF 104 outputs a signal component below a predetermined band limit in the modulated signal received from modulating section 103 to transmission switching section 106 as a baseband radar transmission signal.

FIG. 2 shows an example of a radar transmission signal generated by the radar transmission signal generator 101. As shown in FIG. As shown in FIG. 2, a pulse code sequence of code length L is included in a code transmission period Tw in the radar transmission period Tr. In each radar transmission period Tr, a pulse code sequence is transmitted during the code transmission interval Tw, and the remaining interval (Tr-Tw) is a no-signal interval. One code includes L sub-pulses. In addition, since pulse modulation is performed using No samples per sub-pulse, a signal of Nr (=No×L) samples is included in each code transmission interval Tw. Nu samples are included in a no-signal interval (Tr-Tw) in the radar transmission cycle Tr.

The switching control section 105 controls the transmission switching section 106 in the radar transmitting section 100 and the output switching section 211 in the radar receiving section 200 . Note that the control operation of the output switching unit 211 of the radar receiving unit 200 in the switching control unit 105 will be described later in the description of the operation of the radar receiving unit 200 . The control operation of the switching control section 105 for the transmission switching section 106 of the radar transmission section 100 will be described below.

The switching control section 105 outputs a control signal (hereinafter referred to as a “switching control signal”) for switching the transmission antenna 108 (in other words, the transmission radio section 107) to the transmission switching section 106, for example, every radar transmission period Tr. .

Transmission switching section 106 performs a switching operation of outputting a radar transmission signal input from radar transmission signal generation section 101 to transmission radio section 107 instructed by a switching control signal input from switching control section 105 . For example, transmission switching section 106 selects and switches one of a plurality of transmission radio sections 107-1 to 107-Nt based on a switching control signal, and outputs a radar transmission signal to selected transmission radio section 107. do.

The z-th (z=1, . radar transmission signal is generated, amplified to a predetermined transmission power P [dB] by a transmission amplifier, and output to the z-th transmission antenna 108 .

The z-th (z=1, . . . , Nt) transmitting antenna 108 radiates the radar transmission signal output from the z-th transmitting radio section 107 into space.

FIG. 3 shows an example of switching operation of transmitting antenna 108 according to the present embodiment. Note that the switching operation of transmitting antenna 108 according to this embodiment is not limited to the example shown in FIG.

In FIG. 3, the switching control unit 105 switches from the first transmitting antenna 108 (or the transmitting radio unit 107-1) to the Nt-th transmitting antenna 108 (or the transmitting radio unit 107-Nt) for each radar transmission period Tr. A switching control signal indicating an instruction to sequentially switch is output to transmission switching section 106 . Therefore, in each of the first transmitting antenna 108 to the Nt-th transmitting antenna 108, the radar transmission signal is transmitted at a transmission interval of Np (=Nt×Tr) period.

The switching control section 105 performs control to repeat the switching operation of the transmission radio section 107 at the antenna switching cycle Np Nc times.

The transmission start time of the transmission signal in each transmission radio section 107 does not have to be synchronized with the period Tr. For example, each transmission radio section 107 may set different transmission delays _{Δ 1} , Δ ₂ , . _When such transmission _{delays Δ 1} , _{Δ 2} , . By doing so, the influence of different phase rotations depending on the Doppler frequency can be removed. By varying the transmission delays Δ ₁ , _{Δ 2} , . , the effect of mutually randomizing the effects of interference between other radars is obtained.

Further, the radar transmission section 100 may include a radar transmission signal generation section 101a shown in FIG. 4 instead of the radar transmission signal generation section 101. Radar transmission signal generation section 101a does not have code generation section 102, modulation section 103 and LPF 104 shown in FIG. The code storage unit 111 preliminarily stores code sequences generated by the code generation unit 102 (FIG. 1), and cyclically reads the stored code sequences. The DA conversion unit 112 converts the code series (digital signal) output from the code storage unit 111 into an analog signal (baseband signal).

[Configuration of radar receiver 200]
In FIG. 1, the radar receiver 200 includes Na receiving antennas 202 to form an array antenna. The radar receiver 200 also has Na antenna system processors 201 - 1 to 201 -Na, a CFAR unit 213 and a direction estimator 214 .

Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal reflected by a target, and outputs the received reflected wave signal to the corresponding antenna system processing section 201 as a received signal.

Each antenna system processing section 201 has a receiving radio section 203 and a signal processing section 207 .

Receiving radio section 203 has amplifier 204 , frequency converter 205 , and quadrature detector 206 . The reception radio section 203 generates a timing clock by multiplying the reference signal received from the reference signal generation section 300 by a predetermined number, and operates based on the generated timing clock. Specifically, the amplifier 204 amplifies the received signal received from the receiving antenna 202 to a predetermined level, the frequency converter 205 frequency-converts the received signal in the high frequency band to the baseband band, and the quadrature detector 206 The detection converts the received signal in the baseband band into a received signal in the baseband band including the I signal and the Q signal.

The signal processing unit 207 of each antenna system processing unit 201-z (where z = any of 1 to Na) includes AD conversion units 208 and 209, a correlation calculation unit 210, an output switching unit 211, and a Doppler analysis unit 212-1 to 212-Nt.

The I signal is input from the quadrature detector 206 to the AD conversion section 208 , and the Q signal is input from the quadrature detector 206 to the AD conversion section 209 . The AD conversion unit 208 converts the I signal into digital data by sampling the baseband signal including the I signal at discrete times. The AD conversion unit 209 converts the Q signal into digital data by sampling the baseband signal including the Q signal at discrete times.

Here, in the sampling of the AD converters 208 and 209, for example, Ns discrete samples are performed per time Tp (=Tw/L) of one subpulse in the radar transmission signal. That is, the number of oversamples per subpulse is Ns.

In the following description, using the I signal I _z (k, M) and the Q signal Q _z (k, M), A baseband received signal at discrete time k is expressed as a complex signal x _z (k, M)=I _z (k, M)+j Q _z (k, M) (where z = any of 1 to Na) . In the following description, the discrete time k is based on the start timing of the radar transmission cycle (Tr) (k=1), and the signal processing unit 207 uses k Operates periodically until = (Nr + Nu) Ns/No. That is, k=1, . . . , (Nr+Nu)Ns/No. where j is the imaginary unit.

The correlation calculation unit 210 in the z-th (z=1, . . . , Na)-th signal processing unit 207 receives the discrete sample values I _z (k, M) Discrete sample value x _z (k, M) including Q _z (k, M) and pulse code a _n (M) of code length L transmitted in radar transmission unit 100 (where z=1, . . . , Na , n = 1, ..., L). For example, the correlation calculator 210 performs a sliding correlation calculation between the discrete sample value x _z (k, M) and the pulse code a _n (M). For example, the correlation calculation value AC _z (k, M) of the sliding correlation calculation at the discrete time k in the Mth radar transmission cycle Tr[M] is calculated based on the following equation.

In the above equation, the asterisk (*) represents the complex conjugate operator.

Correlation calculation section 210 performs correlation calculation over a period of k=1, .

Note that the correlation calculation unit 210 is not limited to performing the correlation calculation for k=1, . . . , (Nr+Nu)Ns/No. The range (ie range of k) may be limited. As a result, in the radar device 10, it is possible to reduce the computational processing amount of the correlation computing section 210. FIG. For example, correlation calculator 210 may limit the measurement range to k=Ns(L+1), . . . , (Nr+Nu)Ns/No−NsL. In this case, as shown in FIG. 5, the radar device 10 does not perform measurement during the time interval corresponding to the code transmission interval Tw.

As a result, in the radar apparatus 10, even when the radar transmission signal directly enters the radar receiving section 200, the correlation calculation section 210 does not perform processing during the period during which the radar transmission signal enters (at least the period of less than τ1). Therefore, it is possible to measure without the influence of wraparound. When limiting the measurement range (range of k), the same measurement range (range of k range) may be applied. Thereby, the amount of processing in each component can be reduced, and the power consumption in the radar receiver 200 can be reduced.

Based on the switching control signal input from the switching control unit 105, the output switching unit 211 selectively transfers the output of the correlation calculation unit 210 for each radar transmission period Tr to one of the Nt Doppler analysis units 212. switch to output. Hereinafter, as an example, the switching control signal in the M-th radar transmission cycle Tr[M] is represented by Nt-bit information [bit ₁ (M), bit ₂ (M), . . . , bit _Nt (M)]. For example, in the switching control signal of the M-th radar transmission cycle Tr[M], when the ND-th bit (where ND is any of 1 to Nt) is '1', the output switching unit 211 switches the ND-th th Doppler analysis unit 212 is selected (in other words, turned on). On the other hand, in the switching control signal of the M-th radar transmission cycle Tr[M], when the ND-th bit is '0', the output switching unit 211 deselects the ND-th Doppler analysis unit 212 (in other words, OFF). The output switching section 211 outputs the correlation calculation value AC _z (k, M) input from the correlation calculation section 210 to the selected Doppler analysis section 212 .

For example, an Nt-bit switching control signal corresponding to the switching operation of the transmission radio section 107 (or the transmission antenna 108) shown in FIG.
[bit ₁ (1), bit ₂ (1), … ,bit _Nt (1)] = [1, 0, …, 0]
[bit ₁ (2), bit ₂ (2), … ,bit _Nt (2)] = [0, 1, …, 0]
…
[bit ₁ (Nt), bit ₂ (Nt), … ,bit _Nt (Nt)] = [0, 0, …, 1]

As described above, each Doppler analysis unit 212 is sequentially selected (in other words, turned ON) at Np (=Nt×Tr) cycles. For example, the switching control signal repeats the above contents Nc times.

The z-th (z=1, . . . , Na) signal processing unit 207 has Nt Doppler analysis units 212 .

The Doppler analysis unit 212 performs Doppler analysis on the output from the output switching unit 211 (for example, the correlation calculation value AC _z (k, M)) every discrete time k. For example, if Nc is a power of 2 value, Fast Fourier Transform (FFT) processing can be applied in Doppler analysis.

For example, among the w-th output of the ND-th Doppler analysis unit 212 of the z-th signal processing unit 207, the output in the superimposed virtual reception array described later is, at discrete time k, as shown in the following equation: FIG. 2 shows the Doppler frequency response FT_CI _z ^(ND) (k, f _s , w) for Doppler frequency index f _s ; ND=1 to Nt, k=1, . . . , (Nr+Nu)Ns/No, and w is an integer of 1 or more. Also, N _va indicates the number of antennas corresponding to the superimposed virtual reception array, and N indicates the number of times of transmission within one period. Also, j is an imaginary unit, and z=1 to Na.

As an example, a case (details will be described later) of using the antenna arrangements and transmission intervals shown in FIGS. 7 and 8 will be described. 7 and 8, the set of overlapping virtual receive arrays (VA#4, VA#7, VA#9) are sampled at period T'. Therefore, when ND=1,2,3 and z=4,3,1, Equation (2) is expressed by the following equation. In equation (3), N _va =3 and N=3.

As another example, a case (details will be described later) of using the antenna arrangements and transmission intervals shown in FIGS. 9, 10, 11 and 12 will be described. 9, 10, 11 and 12, the set of overlapping virtual arrays (VA#11, VA#18) is sampled with period T'=3Tr. Therefore, when ND=2 and z=3, and when ND=3 and z=2, Equation (2) is expressed by the following equation. In equation (4), N _va =2 and N=6.

On the other hand, for example, among the w-th outputs of the ND-th Doppler analysis unit 212 of the z-th signal processing unit 207, the outputs of the non-overlapping virtual reception arrays other than the superimposed virtual reception array are expressed by the following equations: As shown, the Doppler frequency response FT_CI _z ^(ND) (k, f _u , w) for Doppler frequency index f _u at discrete time k is shown. ND=1 to Nt, k=1, . . . , (Nr+Nu)Ns/No, and w is an integer of 1 or more. Also, j is an imaginary unit, and z=1 to Na.

Note that the Doppler analysis unit 212 may multiply window function coefficients such as a Han window or a Hamming window during FFT processing. Side lobes generated around the frequency peak can be suppressed by using the window function coefficients.

The processing in each component of the signal processing unit 207 has been described above.

In FIG. 1, the CFAR unit 213 uses the output from the Doppler analysis unit 212 to perform CFAR (Constant False Alarm Rate) processing (in other words, adaptive threshold determination), and obtains a discrete-time index k_ _{Extract cfar} and Doppler frequency index _{fs_cfar} .

For example, CFAR unit 213 outputs _{FT_CI z} ^(ND) (k , f _s , w) is used to perform CFAR processing.

In addition, CFAR section 213 converts Doppler frequency index f _{s_cfar} corresponding to the superimposed virtual reception array to output FT_CI _z ^(ND) (k , f _u , w) is indexed to correspond to the Doppler frequency index f _u . The index conversion may be performed according to Equations (6) and (7). CFAR section 213 outputs Doppler frequency index f _{s_cfar} after index conversion to direction estimating section 214 .

where f _{s_cfar} =-(Nt-1)Nc/2+1,..,0,...,(Nt-1)Nc/2 and f _{u_cfar} =-Nc/2+1,.. ,0,..., Nc/2.

A Doppler frequency index f _{s_cfar} with a wide Doppler frequency range is hereinafter expressed as a wide range Doppler frequency index f _{s_cfar} . A Doppler frequency index f _u with a narrow Doppler frequency range is expressed as a narrow range Doppler frequency index f _u . There may be overlaps in mapping the broad Doppler frequency index f _{s_cfar} to the narrow Doppler frequency index f _u .

For example, if the wide range Doppler frequency index f _{s_cfar} includes the Doppler frequency index α in the range of 0≦α≦Nc/2, it is converted to α by index conversion corresponding to the narrow range Doppler frequency index f _u . Here, if β=α−Nc is also included in the wide range Doppler frequency index f _{s_cfar} , β is included in the range of −Nc≦β≦−Nc/2, so it corresponds to the narrow range Doppler frequency index f _u is converted to β+Nc=α by the index conversion that causes Therefore, duplication occurs in the index conversion that associates the wide range Doppler frequency index _{fs_cfar} with the narrow range Doppler frequency index f _u .

Similarly, if β = α + Nc is also included in the wide range Doppler frequency index f _{s_cfar} , β is included in the range of Nc ≤ β ≤ _3Nc /2. , β+Nc=α. Thus, the index transform to correspond to the narrow Doppler frequency index f _u causes overlap.

In this way, if the wide range Doppler frequency index _{f s_cfar} includes α and β in which |α−β| do.

If the narrow-range Doppler frequency index f _u overlaps, the signal component of the narrow-range Doppler frequency index f _u is in a state in which signals of different Doppler frequency components are mixed. The closer the power of the mixed signal is, the more the amplitude phase component fluctuates, and the accuracy of the angle measurement in the subsequent direction estimator 214 may be degraded. Therefore, in the present embodiment, duplication determination processing is introduced. This suppresses the influence of degrading the accuracy of the side angle in the direction estimator 214 . Next, this duplication determination process will be described.

<Duplicate determination processing>
The w-th output _{FT_CI z} ^(ND) ( k, f _u , w) are converted to correspond to the Doppler frequency index f _u . If the converted Doppler frequency index f _{s_cfar} overlaps, the following processes (B1) to (B3) are performed.

(B1) CFAR unit 213 generates FT_CI ₁ ^(ND) (k, α, w), . . . , FT_CI _Na ^(ND) (k , α, w) and FT_CI ₁ ^(ND) (k, β, w), . . . , FT_CI _Na ^(ND) (k, β, w).

(B2) CFAR unit 213, as a result of comparison of the power sum in (B1), if there is a power difference equal to or greater than a predetermined value (for example, set to about 6 to 10 dB), CFAR unit 213 determines which of Doppler frequency indexes α and β has the greater power One Doppler frequency index is enabled, and the Doppler frequency index with lower power is excluded from the output target to the direction estimator 214 .

(B3) CFAR unit 213 excludes both Doppler frequency indexes α and β from outputs to direction estimating unit 214 when there is no power difference equal to or greater than a predetermined value as a result of the power sum comparison in (B1). .

The processing of the CFAR unit 213 has been described above. Radar apparatus 10 may perform direction estimation processing in direction estimation section 214 without performing CFAR processing.

In FIG. 1, the direction estimator 214 uses the information input from the CFAR unit 213 (for example, the time index _{k_cfar} and the Doppler frequency _{indexes fs_cfar and fu_cfar )} , based on each Doppler analysis unit 212 Target direction estimation processing is performed using the output from the

For example, direction estimating section 214 generates virtual reception array correlation vector h(k, f _s , w) as shown in equation (8), and performs direction estimation processing.

Below, the w-th output from the Doppler analysis units 212-1 to 212-Nt obtained by performing the same processing in each signal processing unit 207 of the antenna system processing units 201-1 to 201-Na is summarized. is expressed as a virtual reception array correlation vector h( _{k_cfar} , _{f_cfar} , w) containing Nt×Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na as shown in Equation (8). do. The virtual receive array correlation vector h( _{k_cfar} , _{f_cfar} , w) is used for direction estimation processing based on the phase difference between the receive antennas 202 for the reflected wave signal from the target. where z=1,...,Na and ND=1,...,Nt.

In equation (8), h _cal[b] is an array correction value that corrects the phase deviation and amplitude deviation between transmitting array antennas and between receiving array antennas. b=1, . . . , Nt×Na. Also, in equation (8), _{f_cfar} =f _{s_cfar} for the set of virtual reception arrays (ND, z) to be superimposed, and _{f_cfar} =f _{u_cfar} for the set of virtual reception arrays (ND, z) not to be superimposed.

Also, since the transmission antenna 108 is switched in a time division manner, different phase rotations occur at different Doppler frequencies f. ^{TxCAL (1)} (f), .

For example, when the first transmitting antenna 108 (ND=1) corresponding to the switching operation of the transmitting radio section 107 (or transmitting antenna 108) shown in FIG. is represented by

When different transmission delays _{Δ 1} ^, Δ ₂ , . may be multiplied by the correction coefficient Δ _TxCAL ^(ND) (f) of equation (10) to obtain a new transmission phase correction coefficient TxCAL ^(ND) (f). This makes it possible to remove the effect of phase rotation that differs depending on the Doppler frequency. Here, ND in Δ _TxCAL ^(ND) (f) is the reference transmission antenna number used as the phase reference.

The virtual receive array correlation vector h( _kcfar , _{fs_cfar} , w) is _a column vector consisting of Na×Nt elements.

The direction estimating unit 214, for example, calculates the spatial profile by _changing the azimuth direction θ in the direction estimation evaluation function value P _H (θ _{BEAM_cfar} , k _cfar , f _{s_cfar} , w) within a predetermined angle range. A predetermined number of maximum peaks of the spatial profile are extracted in descending order, and the azimuth directions of the maximum peaks are output as direction-of-arrival estimation values.

Note that the direction estimation evaluation function value P _H (θ _{BEAM_cfar} , k _cfar , f _{s — cfar} , w) has various methods depending on the direction of arrival estimation algorithm. For example, an estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

For example, when Nt×Na virtual receiver arrays are linearly arranged at equal intervals d _H , the beamformer method can be expressed as follows. Other techniques such as Capon and MUSIC are also applicable.

Here, in equation (11), the superscript H is the Hermitian transpose operator. Also, a(θ _u ) indicates the direction vector of the virtual receiving array for the incoming wave in the azimuth direction θ _u .

Also, the azimuth direction θ _u is a vector obtained by changing the azimuth range in which direction-of-arrival estimation is performed at a predetermined azimuth interval β ₁ . For example, θ _u is set as follows.
θu = θmin + _uβ1 , _u =0,…,NU
NU=floor[(θmax−θmin)/β1] ₊₁
where floor(x) is a function that returns the largest integer value that does not exceed the real number x.

Note that the time information k described above may be converted into distance information and output. The following equation can be used to convert time information k into distance information R(k). Here, Tw represents the code transmission period, L represents the pulse code length, and _C0 represents the speed of light.

Also, the Doppler frequency information may be converted into a relative velocity component and output. To convert the Doppler frequency index f _s to a relative velocity component v _d (f _s ), the following equation can be used. Here, λ is the wavelength of the carrier frequency of the RF signal output from radio transmission section 107 . _Δf is the Doppler frequency interval in FFT processing in Doppler analysis section 212 . For example, in this embodiment, Δ _f =1/(NtNcTr).

The operation of the direction estimation unit 214 has been described above.

[Operation of radar device 10]
The operation of the radar device 10 having the above configuration will be described.

The Nt transmitting antennas 108 (transmitting array) and the Na receiving antennas 202 (receiving array) are arranged, for example, so as to satisfy the following (condition 1), and the transmission timings satisfy the following (condition 2). can be switched.

(Condition 1) Transmission is performed so that at least two of the Nt×Na antenna elements (referred to as virtual antennas or virtual branches) constituting the virtual reception array are placed in the same (overlapping or overlapping) position. An antenna 108 and a receiving antenna 202 are arranged.

(Condition 2) The transmission intervals of the radar transmission signals sequentially transmitted from the transmission antennas 108 respectively corresponding to the virtual antennas having overlapping positions are equal.

First, regarding (condition 2), the transmission timing of the radar transmission signal will be described.

6A, 6B, and 6C show an example of transmission timing of radar transmission signals from multiple transmission antennas 108. FIG. In FIGS. 6A, 6B, and 6C, as an example, the number of transmitting antennas 108 Nt=6 (eg, Tx#1 to Tx#6).

If there are N transmission timings (in other words, the number of transmissions) of the radar transmission signal within the transmission period T (for example, T=Tr×Nt) of each transmission antenna 108, in order to satisfy (Condition 2), the arrangement position The transmission interval (in other words, the transmission cycle) T 'between the transmission antennas corresponding to the overlapping virtual antennas is (1) one cycle for the number of transmissions corresponding to a divisor of N within one transmission cycle T, or , (2) a period of N out of N (in other words, all transmission times).

For example, as shown in FIGS. 6A, 6B, and 6C, when N=6 (divisors: 2 and 3), in one transmission period T=6Tr, transmission periods of transmission antennas corresponding to virtual antennas having overlapping positions T' is a period of once every three transmissions as shown in FIG. 6A (in other words, T'=T/2), and a period of once every two transmissions as shown in FIG. Then, either T'=T/3) or a period of N out of N times (in other words, T'=T/6) as shown in FIG. 6C.

For example, in the radar device 10, the transmission cycle T' is set according to the number of transmission antennas corresponding to virtual antennas having overlapping positions (for example, about several of N or N).

For example, as shown in FIG. 6A, when there are two transmitting antennas Tx#1 and Tx#4 (N=divisor of 6) corresponding to virtual antennas with overlapping placement positions, Tx#1 and Tx# The transmission interval T' of 4 is T/2. Therefore, in the reception process, the radar device 10 can set the sampling interval for the virtual antennas with overlapping positions to the transmission interval T'=T/2 between Tx#1 and Tx#4.

Also, as shown in FIG. 6B, when there are three transmitting antennas 108 corresponding to virtual antennas with overlapping placement positions, Tx#1, Tx#3, and Tx#5 (N=a divisor of 6), Tx# 1, Tx#3 and Tx#5 have a transmission interval T' of T/3. Therefore, in the reception process, the radar device 10 can set the sampling interval for the virtual antennas with overlapping positions to the transmission interval T'=T/3 for Tx#1, Tx#3, and Tx#5.

Also, as shown in FIG. 6C , when the transmitting antennas 108 corresponding to the virtual antennas whose arrangement positions overlap are all (N) of Tx#1 to Tx#6, the transmission interval T of Tx#1 to Tx#6 is ' becomes T/6. Therefore, in the reception process, the radar apparatus 10 can set the sampling interval for the virtual antennas with overlapping positions to the transmission interval T'=T/6 for Tx#1 to Tx#6.

For example, when the sampling interval is the transmission interval T of each transmission antenna 108, the maximum value of the relative velocity v _max =λ/(4T). where λ indicates the wavelength of the carrier frequency and T indicates the sampling interval.

On the other hand, for example, in FIG. 6A, when the sampling interval of the virtual antennas with overlapping placement positions is set to the transmission interval T'=T/2, the maximum value of the relative velocity _v'max =λ/4T'=2v represented by _max . Similarly, for example, in FIG. 6B, when the sampling interval in the virtual antennas with overlapping placement positions is the transmission interval T'=T/3, the maximum value _v'max of the relative velocity is λ/4T'= _3vmax . expressed. Similarly, for example, in FIG. 6C, when the sampling interval of virtual antennas with overlapping placement positions is set to transmission interval T'=T/6, the maximum value of relative velocity _v'max = λ/4T'= _6vmax expressed.

As described above, in FIGS. 6A, 6B, and 6C, the relative velocity The maximum value v' _max (or Doppler frequency range) of each transmit antenna 108 based on the transmission interval T is a multiple of N or N times the maximum value v _max (or Doppler frequency range) of the relative velocity is expanded to Therefore, in the radar apparatus 10, the Doppler frequency range in which the Doppler frequency can be detected without aliasing can be expanded, and ambiguity of the Doppler frequency can be prevented.

The radar device 10 transmits radar transmission signals in a predetermined transmission pattern using a plurality of transmission antennas 108 . For example, the transmission pattern (in other words, the switching pattern indicated by the switching control signal) of the transmitting antenna 108 that transmits the radar transmission signal at a plurality of transmission timings (for example, N times) within the transmission cycle T is set every transmission cycle T. is repeated to In the radar device 10, the transmission pattern (in other words, the switching pattern indicated by the switching control signal) of the transmission antenna 108 that transmits the radar transmission signal at a plurality of transmission timings (for example, N times) within the transmission period T is the above transmission. It repeats every cycle T.

Next, regarding (Condition 1), a specific example of the antenna arrangement according to the present embodiment will be described. Arrangement Example 1 and Arrangement Example 2, which are specific examples of antenna arrangement, will be described below as examples.

<Arrangement example 1>
In arrangement example 1, a case will be described in which the transmitting antennas 108 and the receiving antennas 202 are arranged one-dimensionally.

FIG. 7 shows an example of an antenna arrangement according to Arrangement Example 1. As shown in FIG.

In FIG. 7, the number of transmit antennas 108 is Nt=3 (eg Tx#1, Tx#2 and Tx#3) and the number of receive antennas 202 is Na=4 (eg Rx#1, Rx#2, Rx#3 and Rx#4).

In FIG. 7, for example, the interval between Tx#1 and Tx#3 is the same as the interval between Rx#1 and Rx#4. Also, in FIG. 7, for example, the interval between Tx#3 and Tx#2 is the same as the interval between Rx#1 and Rx#3.

In this case, as shown in FIG. 7, in the virtual receiving array arrangement (Nt×Na=12 VA#1 to VA#12), a virtual antenna VA#4 configured by Tx#1 and Rx#4, A virtual antenna VA#7 made up of Tx#2 and Rx#3 and a virtual antenna VA#9 made up of Tx#3 and Rx#1 are arranged at the same position to overlap.

For example, the radar apparatus 10 arranges each antenna so that the transmission intervals of the transmission antennas Tx#2 and Tx#3 corresponding to the virtual antennas VA#11 and VA#18, which are redundantly arranged at the same position, are equal. The transmission timing of the transmission antenna 108 is switched. For example, FIG. 8 shows each virtual antenna (VA#1 to VA#12 ) (in other words, the transmission timing of each transmission antenna 108) of the reflected wave signal.

As shown in FIG. 8, the radar transmission signals are transmitted at transmission intervals T' in order of Tx#1, Tx#2 and Tx#3. Note that the transmission interval T=3T' of the radar transmission signal transmitted from each transmission antenna 108 (in other words, T'=T/3).

Therefore, in FIG. 8 , as in FIG. 6C , it is assumed that the arrangement positions overlap at all of the transmission timings N=3 of the radar transmission signal within the transmission period T (for example, T=Tr×Nt) of each transmission antenna 108 . Radar transmission signals are transmitted from transmission antennas 108 (for example, Tx#1, Tx#2 and Tx#3) corresponding to the antennas (VA#4, VA#7 and VA#9).

As shown in FIG. 8, the radar apparatus 10 receives reflected wave signals corresponding to radar transmission signals transmitted from Tx#1, Tx#2, and Tx#3 at each transmission interval T'.

Here, in FIG. 8, attention is paid to the virtual antennas VA#4, VA#7 and VA#9 having overlapping positions. As shown in FIG. 8, a received signal is received at each transmission cycle T' by any one of the virtual antennas VA#4, VA#7, and VA#9. Specifically, the radar apparatus 10 receives the reflected wave signal at VA#4 at the transmission timing of Tx#1, receives the reflected wave signal at VA#7 at the transmission timing of Tx#2, and receives the reflected wave signal at VA#7 at the transmission timing of Tx#3. At the transmission timing, the reflected wave signal is received at VA#9. In other words, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna at the same position at each transmission timing without waiting for the reception of the reflected wave signal for each transmission period T of each transmission antenna 108 . The radar device 10 performs Doppler analysis using signals received at virtual antennas VA#4, VA#7 and VA#9, for example.

In this way, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna arranged at the same position every transmission interval T'. Therefore, for example, in FIG. 8, the radar device 10 can set the sampling interval T' to T'=T/3 at the placement positions of the virtual antennas VA#4, VA#7, and VA#9.

For example, when the sampling interval is the transmission interval T of each transmission antenna 108, the maximum value of the relative velocity is represented by v _max =λ/4T. Here, λ indicates the wavelength of the carrier frequency. On the other hand, as shown in FIG. 8, when the sampling interval T'=T/3 for the virtual antennas VA#4, VA#7 and VA#9, the maximum relative velocity _v'max =λ/4T '=3v _max .

As a result, in Arrangement Example 1, the maximum value v′ _max of the relative velocity (or the Doppler frequency range) is expanded to three times the maximum value v _max of the relative velocity based on the transmission interval T for each transmitting antenna 108 .

<Arrangement example 2>
In arrangement example 2, a case will be described in which the transmitting antennas 108 and the receiving antennas 202 are arranged two-dimensionally and direction-of-arrival estimation is performed three-dimensionally.

9 shows an arrangement example of the transmitting antennas 108 according to the arrangement example 2, and FIG. 10 shows an arrangement example of the receiving antennas 202 according to the arrangement example 2. As shown in FIG. Also, FIG. 11 shows an arrangement example of a virtual reception array configured by the transmission antennas 108 shown in FIG. 9 and the reception antennas 202 shown in FIG.

In FIG. 9, the number of transmitting antennas 108 is Nt=6 (eg, Tx#1 to Tx#6), and in FIG. 10, the number of receiving antennas 202 is Na=8 (eg, Rx#1 to Rx#8). and

As shown in FIGS. 9 and 10, the transmitting antenna 108 and the receiving antenna 202 are two-dimensionally arranged in the direction of a first axis and in the direction of a second axis orthogonal to the first axis. For example, in FIG. 9, the two-dimensional arrangement relationship of Tx#2 and Tx#3 is the same as the two-dimensional arrangement relationship of Rx#8 and Rx#6 shown in FIG.

In this case, as shown in FIG. 11, in the virtual receiving array arrangement (Nt×Na=48 VA#1 to VA#48), a virtual antenna VA#11 configured by Tx#2 and Rx#3, A virtual antenna VA#18 configured by Tx#3 and Rx#2 are arranged at the same position and overlap.

For example, the radar apparatus 10 arranges each antenna so that the transmission intervals of the transmission antennas Tx#2 and Tx#3 corresponding to the virtual antennas VA#11 and VA#18, which are redundantly arranged at the same position, are equal. The transmission timing of the transmission antenna 108 is switched. FIG. 12 shows an example of transmission timing of each transmission antenna 108 for each virtual antenna (VA#1 to VA#12) shown in FIG.

In FIG. 12, the radar transmission signals are, for example, Tx#2, Tx#1, Tx#4, Tx#3, Tx#5 and Tx# in the transmission period T (for example, T=6Tr) of each transmission antenna 108. 6 are sent in order. Therefore, as shown in FIG. 12, the transmission interval T' between Tx#2 and Tx#3 is T/2, which is an equal interval. In addition, in FIG. 12, the transmission interval of Tx#2 and Tx#3 should be T/2, and the transmission order of each transmission antenna 108 is not limited to the order shown in FIG.

Therefore, in FIG. 12, as in FIG. 6A, 2, which is a divisor of N, is the transmission timing N=6 times of the radar transmission signal within the transmission period T (for example, T=Tr×Nt) of each transmission antenna 108. A radar transmission signal is transmitted from the transmission antennas 108 (for example, Tx#2 and Tx#3) corresponding to the virtual antennas (VA#11 and VA#18) having overlapping positions.

In the virtual antennas VA#11 and VA#18 having overlapping positions, the radar apparatus 10 receives reflected radar transmission signals respectively transmitted from Tx#2 and Tx#3 corresponding to VA#11 and VA#18. A wave signal is received every transmission interval T/2. In other words, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna at the same position every transmission interval T′=T/2 without waiting for the reception of the reflected wave signal every transmission period T of each transmission antenna 108. . The radar device 10 performs Doppler analysis using signals received at virtual antennas VA#11 and VA#18, for example.

In this way, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna arranged at the same position every transmission interval T'. Therefore, for example, in FIG. 12, the radar device 10 can set the sampling interval T' to T'=T/2 at the placement positions of the virtual antennas VA#11 and VA#18.

For example, when the sampling interval is the transmission interval T of each transmission antenna 108, the maximum value of the relative velocity is represented by v _max =λ/4T. Here, λ indicates the wavelength of the carrier frequency. On the other hand, as shown in FIGS. 11 and 12, when the sampling interval T'=T/2 in the virtual antennas VA#11 and VA#18, the maximum relative velocity _v'max =λ/4T' =2v _max .

As a result, in Arrangement Example 2, the maximum value v′ _max of the relative velocity (or the Doppler frequency range) is expanded to twice the maximum value v _max of the relative velocity based on the transmission interval T for each transmission antenna 108 .

Arrangement example 1 and arrangement example 2 of antenna arrangement have been described above.

In addition, the antenna arrangement (for example, the number of antennas Nt, Na or the arrangement position) is not limited to the examples shown in FIGS. Just do it.

Here, for example, in the virtual receiving array shown in FIG. 7, the gap between VA#8 and VA#12 is wider than the gap between other virtual antennas. In the present embodiment, for example, the transmitting antenna 108 and the receiving antenna 202 may be arranged so that the virtual receiving array has one or less missing portions. As a result, it is possible to prevent the level of side lobes or grating lobes from increasing (in other words, from reaching an unacceptable level) due to the toothless state.

Note that another arrangement example of the antenna arrangement will be described later in Variation 4. FIG.

As described above, in the present embodiment, in the radar device 10, at least two virtual antennas of the virtual reception array including a plurality of virtual antennas configured based on the plurality of transmission antennas 108 and the plurality of reception antennas 202 are placed in the same position. Further, in the radar device 10, the transmission intervals of the radar transmission signals between the transmission antennas 108 corresponding to at least two virtual antennas having the same arrangement position among the plurality of transmission antennas 108 are made equal.

Thereby, the radar device 10 can receive the reflected wave signal at each transmission timing of the plurality of transmission antennas 108 corresponding to the virtual antennas having the same arrangement position. Therefore, the radar device 10 can shorten the reception interval for one virtual antenna compared to the transmission interval for each transmission antenna 108 . Therefore, the radar apparatus 10 can expand the Doppler frequency range (or the maximum value of the relative velocity) by shortening the sampling interval of the virtual antenna.

Moreover, in the radar device 10 , the transmitting antennas 108 and the receiving antennas 202 are arranged using a plurality of transmitting antennas 108 so that the positions of the virtual antennas corresponding to the respective transmitting antennas 108 overlap. As an example, in FIG. 7, if one transmitting antenna (one branch) of Tx#1 and four receiving antennas (Rx#1 to Rx#4) are used, as described above, the transmission interval (in other words, Although the sampling interval) can be shortened, the antenna aperture length becomes four antennas. On the other hand, in the present embodiment, by using three transmitting antennas (three branches) Tx#1 to Tx#3 and four receiving antennas (Rx#1 to Rx#4), as described above, The antenna aperture length can be reduced to 10 antennas while shortening the sampling interval.

As a result, in the present embodiment, the radar device 10 achieves the expansion of the above-described Doppler frequency range while increasing the antenna aperture area (or antenna aperture length) as compared with the case where one transmission antenna is used. can.

Moreover, in the present embodiment, by overlapping the arrangement positions of virtual antennas corresponding to a plurality of transmitting antennas 108, the reception intervals of the virtual antennas are shortened and the Doppler frequency range is expanded. Therefore, in the present embodiment, for example, it is not necessary to widen the element spacing of the receiving antenna 202 in order to secure the antenna aperture area. increase can be suppressed.

As described above, according to the present embodiment, while suppressing the reduction of the antenna aperture area or the increase of the grating lobe, the Doppler frequency range (or the maximum relative velocity value) can be expanded. Thereby, the radar device 10 can accurately detect a target (for example, the direction of arrival) in a wider Doppler frequency range.

(Variation 1 of one embodiment)
If there are N transmission timings (or the number of times of transmission) within the transmission cycle T of each transmission antenna 108, the transmission interval (or transmission cycle) T′ of the transmission antennas corresponding to the virtual antennas with overlapping placement positions is as described above. , (1) one cycle for the number of transmissions corresponding to a divisor of N, or (2) a cycle for all N transmissions.

Variation 1 describes a case where the number Nt of transmitting antennas 108 (for example, the number of transmissions N) is a prime number and there is no divisor of N.

In variation 1, if Nt is a prime number, N is set to a non-prime number larger than Nt, for example. For example, when Nt=5, N may be set to "6", which is a value (Nt+1) larger than Nt by one. The transmission intervals between the transmission antennas 108 corresponding to virtual antennas having overlapping positions can be made equal.

In addition, when the radar transmission signal is transmitted from the transmitting antenna 108 corresponding to the virtual antennas having overlapping positions at all N transmission timings within the transmission cycle T of each transmitting antenna 108 (for example, see FIG. 6C). , set N=Nt even if Nt is a prime number (eg Nt=5). This is because even when N=Nt, the transmission intervals between the transmitting antennas 108 corresponding to virtual antennas having overlapping positions can be made equal.

Therefore, for example, when Nt = 5, the transmission cycle T 'of multiple transmission antennas corresponding to virtual antennas with overlapping placement positions is, for example, a divisor of N = 6 within one transmission cycle T (that is, 2 or It is either one cycle for the number of times of transmission in 3) or a cycle of Nt times when N=Nt=5 times.

FIG. 13 shows the case where Nt=5 and the number of transmissions of the transmitting antennas corresponding to the virtual antennas having overlapping positions within one transmission cycle T is set to 2 (transmission cycle T′=T/2). It is an example of transmission timing. In FIG. 13, transmitting antennas Tx#1 and Tx#4 are transmitting antennas corresponding to virtual antennas having overlapping positions.

In the example shown in FIG. 13, for Nt=5 (prime number), the number of transmissions N within the transmission period T is 6 times (=Nt+1). Therefore, in FIG. 13, the transmission interval T' of the two transmitting antennas 108 of Tx#1 and Tx#4 is equal to T/2. In addition, in FIG. 13, Tx#5 transmits the radar transmission signal twice within one transmission period T as an example. However, if the transmission timings of the transmission antennas Tx#1 and Tx#4 are equidistant, in the transmission pattern within the transmission period T, the transmission antenna 108 that transmits the radar transmission signal multiple times is the transmission antenna other than Tx#5. 108 (eg, Tx#2 or Tx#3).

According to Variation 1, even when the number Nt of transmitting antennas 108 is a prime number, the transmission intervals of transmitting antennas corresponding to virtual antennas having overlapping positions can be made equal. Therefore, as in the above-described embodiment, the range of Doppler frequencies (maximum value of relative velocity) can be expanded. The direction of arrival can be estimated with high accuracy.

Although the case of Nt=5 has been described in FIG. 13, the same applies to cases where the value of Nt is another prime number. Also, in FIG. 13, the case where Nt=5 and N=Nt+1 has been described, but N is not limited to the value obtained by adding 1 to Nt.

In addition, in FIG. 13, as an example, when N=Nt+1=6, the case where the number of transmissions is set to 2, which is a divisor of N, has been described, but the number of transmissions is another divisor. It can be a certain 3 times, or it can be Nt times.

For example, in the case of N>Nt, if the number of transmissions of the transmitting antennas corresponding to the virtual antennas with overlapping placement positions within the transmission cycle T is 3 or more, in the transmission pattern of the transmitting antenna 108 within the transmission cycle T, the placement position may be set as the transmitting antenna 108 that transmits the radar transmission signal a plurality of times (twice or more).

FIG. 14A shows, as an example of N>Nt, when Nt=5 and N=6, transmission antennas corresponding to virtual antennas whose placement positions overlap within the transmission period T (for example, Tx#1 and Tx#4 ) is transmitted three times. In FIG. 14A, in the transmission pattern (or switching pattern) within the transmission cycle T, the transmission timing of Tx#1 is set twice, and the transmission timing of Tx#4 is set once.

Further, for example, in the case of N>Nt, if the number of transmissions of the transmission antennas corresponding to the virtual antennas having overlapping positions within the transmission period T is 3 or more, in the transmission pattern of the transmission antenna 108 within the transmission period T, The transmitting antenna 108 that transmits the radar transmission signal multiple times may be a transmitting antenna other than the transmitting antenna farthest from the center of gravity in the arrangement of the multiple transmitting antennas 108 . For example, the transmitting antenna 108 that transmits the radar transmission signal multiple times may be a transmitting antenna near the center of the arrangement of the multiple transmitting antennas 108 .

FIG. 14B shows, as an example of N>Nt, when Nt=5 and N=6, transmission antennas corresponding to virtual antennas whose placement positions overlap within the transmission period T (for example, Tx#3 and Tx#4 ) is transmitted three times. In FIG. 14B, the transmitting antenna Tx#3 is the transmitting antenna arranged in the center of the transmitting antennas Tx#1 to Tx#5 (or the transmitting antenna other than the transmitting antenna farthest from the center of gravity). In other words, Tx#3 is a transmitting antenna forming a virtual antenna near the center on the virtual antenna arrangement. In the case of FIG. 14B, the transmission timing of Tx#3 is set twice, and the transmission timing of Tx#4 is set once. As a result, the radar device 10 can reduce side lobes on the angular profile during direction estimation due to the effect of the window function.

(Variation 2 of one embodiment)
Variation 2 describes a case where signals obtained by beamforming using multiple antennas (multiple transmitting antennas 108 or multiple receiving antennas 202) are treated as real signals with different phase centers from the signals of each antenna.

FIG. 15 shows an example of the antenna arrangement of the transmitting antenna 108 and the receiving antenna 202 according to Variation 2, and the arrangement of the virtual receiving array.

In FIG. 15, the number of transmit antennas 108 is Nt=3 (eg Tx#1, Tx#2 and Tx#3) and the number of receive antennas 202 is Na=2 (eg Rx#1 and Rx#2). and However, the values of Nt and Na are not limited to the examples shown in FIG.

For example, each antenna element of the transmit antenna 108 and the receive antenna 202 is arranged at an integer multiple of the spacing d. In FIG. 15, Tx#1, Tx#2 and Tx#3 are spaced 2d apart, and Rx#1 and Rx#2 are spaced 3d apart. Note that the interval d is about a half wavelength, for example, d=0.5λ.

In variation 2, the radar device 10 controls the phases of Tx#2 and Tx#3 in the transmitting antenna 108 shown in FIG. (In other words, antenna synthesis). In FIG. 15, the two-element phase center exists between Tx#2 and Tx#3. For example, when equal power is supplied to Tx#2 and Tx#3, the phase center of the two elements is the middle point between Tx#2 and Tx#3, as shown in FIG.

Further, in FIG. 15, the interval 3d between the phase center points of the two elements Tx#2 and Tx#3 (for example, the phase center of the composite antenna) and Tx#1 is the interval between Rx#1 and Rx#2. Identical to 3d.

In this case, as shown in FIG. 15, in the virtual reception array, a virtual antenna configured by the combined antenna of Tx#2 and Tx#3 and Rx#1 (in other words, a virtual antenna corresponding to the combined antenna), A virtual antenna VA#2 configured by Tx#1 and Rx#2 is arranged at the same position to overlap. At positions where two virtual antennas overlap, there are two received signals.

In variation 2, the radar transmission unit 100 arranges the transmission antennas so that the transmission intervals of Tx#1 corresponding to virtual antennas having overlapping positions and the combined antennas of Tx#2 and Tx#3 are equal. 108 is switched.

FIG. 16 shows an example of transmission timing in the antenna arrangement shown in FIG. Note that the transmission timing is not limited to the example shown in FIG. 16, and may be set such that the transmission timings of the transmission antennas 108 corresponding to the virtual antennas having overlapping positions are at regular intervals.

In FIG. 16, the transmission interval (transmission cycle) for each transmission antenna 108 of Tx#1, Tx#2 and Tx#3 is T=4Tr. Further, as shown in FIG. 16, the transmission timing of Tx#1 and the transmission timing of the combined antenna (Tx#2+Tx#3) of Tx#2 and Tx#3 (in other words, Tx#2 and Tx#3 timing of simultaneous transmission of ) is T'=2Tr. Therefore, as shown in FIG. 16, the transmission interval T' between Tx#1 and the composite antenna of Tx#2 and Tx#3 is equal to 2Tr=T/2.

In the case of FIG. 16, the radar apparatus 10 receives the reflected wave signal at each transmission period T'=2Tr at the virtual antennas whose placement positions overlap in FIG. In the Doppler analysis unit 212 of the radar reception unit 200, for example, the Doppler analysis is performed using the received signals respectively received by the two virtual antennas that are arranged at overlapping positions in FIG.

In this way, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna arranged at the same position every transmission interval T'. Therefore, for example, in FIG. 16, the radar device 10 can set the sampling interval to T'=T/2 for the virtual antennas arranged at the same position.

For example, as shown in FIG. 16, when the sampling interval is the transmission interval T=4Tr of each transmitting antenna 108, the maximum relative velocity is represented by v _max =λ/4T. Here, λ indicates the wavelength of the carrier frequency. On the other hand, as shown in FIG. 16, the sampling interval T'=2Tr=T/2 in the virtual antenna corresponding to the transmission interval (2Tr) between Tx#1 and the combined antenna of Tx#2 and Tx#3 , the maximum value of the relative velocity v' _max =λ/4T'=2v _max .

As a result, in FIG. 15, the maximum relative velocity v′ _max (or the Doppler frequency range) is expanded to twice the maximum relative velocity v _max based on the transmission interval T for each transmitting antenna 108 . In other words, the Doppler frequency range (relative velocity) in which aliasing does not occur is doubled compared to when the virtual receive arrays do not overlap.

Therefore, in variation 2, the radar apparatus 10 has a Doppler frequency range (maximum value of relative velocity) in which aliasing does not occur (in other words, ambiguity does not occur) compared to the case where the virtual antennas do not overlap in the virtual reception array. can be expanded to estimate the direction of arrival with high accuracy.

In variation 2, radar transmission signals are simultaneously transmitted from at least two transmission antennas 108 out of a plurality of (for example, three or more) transmission antennas 108 . Thereby, the placement position of the virtual antenna is determined based on the phase center point between the at least two transmitting antennas 108 . Therefore, for example, as compared with the above embodiment, it is not necessary to overlap the virtual antennas configured by the transmitting antenna 108 alone. For example, in FIG. 15, virtual antennas VA#1 to VA#6 configured by combinations of Tx#1 to Tx#3, Rx#1 and Rx#2 do not overlap each other. By doing so, in Variation 2, the Doppler frequency range (or maximum value of relative velocity) can be expanded without reducing the aperture length of the virtual receive array.

Further, for example, the antenna combination of Tx#2 and Tx#3 shown in FIG. The resulting combined beam has a smaller mainlobe width and can be adapted to a narrower range. For example, it is conceivable that variation 2 is applied to a scene in which it is desired to detect an object with a high relative speed in a narrow range, such as a high-speed object on a highway.

Although FIG. 15 describes antenna combining (simultaneous transmission) of a plurality of transmitting antennas 108, the present invention is not limited to this, and received signals of a plurality of (for example, three or more) receiving antennas 202 may be combined.

FIG. 17 shows an example of combining received signals from a plurality of receiving antennas 202 .

In FIG. 17, the number of transmitting antennas 108 is Nt=2 (eg, Tx#1 and Tx#2), and the number of receiving antennas 202 is Na=3 (eg, Rx#1, Rx#2 and Rx#3). do. However, the values of Nt and Na are not limited to the examples shown in FIG.

For example, each antenna element of the transmit antenna 108 and the receive antenna 202 is arranged at an integer multiple of the spacing d. In FIG. 17, Tx#1 and Tx#2 are spaced 3d apart, and Rx#1, Rx#2 and Rx#3 are spaced 2d apart. Note that the interval d is about a half wavelength, for example, d=0.5λ.

In FIG. 17, the radar device 10 synthesizes received signals of Rx#1 and Rx#2. For example, as shown in FIG. 17, the phase center of the two elements Rx#1 and Rx#2 is the middle point between Rx#1 and Rx#2.

Further, as shown in FIG. 17, the distance 3d between the phase center points of the two elements Rx#1 and Rx#2 (for example, the phase center of the composite antenna) and Rx#3 is Tx#1 and Tx#2 is the same as the interval 3d between

In this case, as shown in FIG. 17 , in the virtual reception array, a virtual antenna configured by a combined antenna of Rx#1 and Rx#2 and Tx#2 (in other words, a virtual antenna corresponding to the combined antenna), A virtual antenna VA#3 configured by Tx#1 and Rx#3 is arranged at the same position so as to overlap. At positions where two virtual antennas overlap, there are two received signals.

In variation 2, the radar transmission unit 100 switches the transmission timing of each transmission antenna 108 so that the transmission intervals of Tx#1 and Tx#2 corresponding to virtual antennas having overlapping positions are equal. Also, the radar receiver 200 synthesizes the reflected wave signals received at Rx#1 and Rx#2. As a result, the placement position of the virtual antenna is determined based on the phase center point between Rx#1 and Rx#2.

17, like FIG. 15, the Doppler frequency range (or the maximum value of the relative velocity) can be expanded without reducing the aperture length of the virtual receiving array.

Here, as the antenna combining processing, the processing of simultaneously transmitting radar transmission signals from the two transmitting antennas 108 and the processing of combining the received signals from the two receiving antennas 202 have been described. More than one transmit antenna 108 or more than two receive antennas 202 may be used.

(Variation 3 of one embodiment)
Each of the transmit antennas 108 and each of the receive antennas 202 may be configured by a sub-array antenna.

FIGS. 18 and 19 show an example of a case in which antenna arrangements similar to the arrangement of the transmitting antennas 108 shown in FIG. 9 and the arrangement of the receiving antennas 202 shown in FIG. 10 are configured with subarray antennas.

For example, one system (one antenna element) of the transmitting antenna 108 and the receiving antenna 202 physically interferes with adjacent antennas with a point on the plane of the first axis and the second axis shown in FIGS. 9 and 10 as the phase center. The aperture length may be widened to such an extent that a subarray antenna may be used. Thereby, the beam width is narrowed and a high antenna gain can be obtained. Also, the side lobe may be suppressed by applying an array weight to the sub-array antenna.

For example, as shown in FIG. 18, one antenna system may be configured with a subarray antenna having four elements in the second axis direction. When the field of view (FOV) of the radar device 10 is wide in the horizontal direction and narrow in the vertical direction, the single beam pattern of the transmitting antenna 108 and the receiving antenna 202 is also wide in the horizontal direction. , and a narrow angle in the vertical direction is desirable. Therefore, as shown in FIG. 18, a configuration of sub-array antennas arranged in the vertical direction (for example, the direction of the second axis) can be considered. Note that, instead of the antenna arrangement shown in FIG. 18, a subarray antenna configuration in which elements are arranged in the horizontal direction (for example, the first axis direction) may be used. In this way, it is desirable that one transmission antenna and one reception antenna system be composed of a subarray antenna that forms a beam pattern suitable for the viewing angle of the radar device 10 .

Also, in FIG. 18, the case where all the antenna elements have the same subarray antenna configuration has been described, but the present invention is not limited to this. For example, the configuration may be changed for each antenna element as long as it does not interfere with adjacent antennas.

For example, as shown in FIG. 19, each element of the transmitting antenna 108 consists of a sub-array of 8 elements, 2 elements along the first axis and 4 elements along the second axis. Further, as shown in FIG. 19, among the receiving antennas 202, Rx#4, Rx#6, and Rx#7 have 24 elements, 3 elements in the first axis direction and 8 elements in the second axis direction. Rx#1, Rx#2, Rx#3, Rx#5 and Rx#8 are subarrays of four elements, one element in the direction of the first axis and four elements in the direction of the second axis. Configured. In the antenna configuration of FIG. 19, for example, compared with the antenna configuration of FIG. 18, the beam pattern of one antenna system has a narrower angle, resulting in a narrower field of view (FOV). As a result, in the radar apparatus 10 having the antenna configuration shown in FIG. 19, the antenna gain in the front direction is improved, and the SNR (Signal to Noise Ratio, or S/N ratio) can be improved.

Also, as shown in FIG. 9, FIG. 10, FIG. 18 or FIG. 19, even if dummy antenna elements are installed with respect to the transmitting antenna 108 (antenna element) and the receiving antenna 202 (antenna element) arranged at uneven intervals, good. For example, in FIG. 18, a dummy antenna element may be installed in the right area of Rx#1 or the left area of Rx#8. By installing a dummy antenna element, for example, the effect of equalizing the influence of electrical characteristics such as antenna radiation, impedance matching, or isolation can be obtained.

(Variation 4 of one embodiment)
In Variation 4, regarding the antenna arrangement of the transmitting antenna 108 and the receiving antenna 202, another arrangement example other than the arrangement example 1 and the arrangement example 2 will be described. Note that the antenna arrangement examples (for example, the number of antennas or the antenna arrangement positions) described below are only examples, and the present invention is not limited to these.

20 to 23, 25, and 27 to 30, which will be described later, denotes the interval of one cell shown in FIGS. However, the distance d may have different values between the first axis and the second axis.

(Arrangement Example 3: Example of Nt=6 and Na=8)
In arrangement example 3, the number of transmitting antennas 108 is Nt=6 (eg, Tx#1 to Tx#6), and the number of receiving antennas 202 is Na=8 (eg, Rx#1 to RX#8). An example of antenna arrangement will be described. Further, in arrangement example 3, one of the transmitting antenna 108 and the receiving antenna 202 is a one-dimensional linear array, and the other is a two-dimensional planar array.

<Layout example 3-1>
FIG. 20 shows an example of the antenna arrangement of the transmitting antennas 108 and the receiving antennas 202 and the arrangement of the virtual receiving arrays according to the arrangement example 3-1.

In FIG. 20, Tx#1 to Tx#6 are linearly arranged at an interval d in the first axis direction, for example. Further, in FIG. 20, Rx#1 to Rx#4 and Rx#5 to Rx#8 are arranged at intervals of d in the second axis direction, and the set of Rx#1 to Rx#4 and Rx#5 to A pair of Rx#8 are arranged at intervals of 3d in the first axis direction.

In this case, as shown in FIG. 20, in the virtual receiving array arrangement (Nt×Na=48 virtual antennas), the virtual antennas corresponding to Tx#1 and Tx#4, the virtual antennas corresponding to Tx#2 and Tx#5 The virtual antennas and the virtual antennas corresponding to Tx#3 and Tx#6 are arranged overlappingly at four locations in the second axis direction. In FIG. 20, two virtual antennas are overlapped at each placement position (hereinafter sometimes referred to as "overlapping once").

In this way, multiple virtual antennas corresponding to at least one transmit antenna 108 (eg, Tx#1 to Tx#6 in FIG. 20) overlap virtual antennas corresponding to other transmit antennas 108 at multiple positions. are placed as follows. As a result, the radar apparatus 10 can improve the quality (for example, SNR) of the received signal by using the received signal received by the virtual antennas at a plurality of placement positions.

<Layout example 3-2>
FIG. 21 shows an example of the antenna arrangement of the transmitting antennas 108 and the receiving antennas 202 and the arrangement of the virtual receiving array according to the arrangement example 3-2.

FIG. 21 shows that in the receiving antenna 202, compared to the antenna arrangement of arrangement example 3-1 (FIG. 20), the antenna spacing in the first axis direction is the same, and Rx#2, Rx#4, Rx#6 and This is an antenna arrangement in which the arrangement position of Rx#8 is shifted to the right by the interval d in the direction of the first axis. In the antenna arrangement shown in FIG. 21 as well, similar to FIG. The received signal quality (eg, SNR) can be improved.

<Arrangement example 3-3>
FIG. 22 shows an example of the antenna arrangement of the transmitting antenna 108 and the receiving antenna 202 according to arrangement example 3-3, and the arrangement of the virtual reception array.

In FIG. 22 , the transmitting antenna 108 has Tx#1 to Rx#3 and Tx#4 to Tx#6 arranged at an interval d in the second axis direction, and is a group of Tx#1 to Tx#3. A set of Tx#4 to Tx#6 are arranged at intervals of 4d in the direction of the first axis. Also, in FIG. 22, Rx#1 to Rx#8 are linearly arranged at an interval d in the first axis direction, for example.

In this case, as shown in FIG. 22, in the virtual receiving array arrangement (Nt×Na=48 virtual antennas), the virtual antennas corresponding to Tx#1 and Tx#4, the virtual antennas corresponding to Tx#2 and Tx#5 The virtual antennas and the virtual antennas corresponding to Tx#3 and Tx#6 are arranged overlappingly at four locations in the first axis direction. In FIG. 22, two virtual antennas are overlapped at each arrangement position (one overlap).

In this way, multiple virtual antennas corresponding to at least one transmit antenna 108 (eg, Tx#1 to Tx#6 in FIG. 22) overlap virtual antennas corresponding to other transmit antennas 108 at multiple positions. are placed as follows. As a result, the radar apparatus 10 can improve the quality (for example, SNR) of the received signal by using the received signal received by the virtual antennas at a plurality of placement positions.

<Arrangement Example 3-4>
FIG. 23 shows an example of the antenna arrangement of the transmitting antenna 108 and the receiving antenna 202 according to arrangement example 3-4, and the arrangement of the virtual reception array.

FIG. 23 shows that in the transmitting antenna 108, compared to the antenna arrangement of arrangement example 3-3 (FIG. 22), the antenna spacing in the first axis direction is the same, and the arrangement positions of Tx#2 and Tx#5 are the same. This is an antenna arrangement in which the positions of Tx#3 and Tx#6 are shifted to the right by an interval d in the direction of one axis, and the positions of Tx#3 and Tx#6 are shifted to the right by an interval 2d in the direction of the first axis. In the antenna arrangement shown in FIG. 23 as well, similar to FIG. The received signal quality (eg, SNR) can be improved.

Arrangement Example 3-1 to Arrangement Example 3-4 have been described above.

FIG. 24 shows an example of transmission timings of each of the transmission antennas 108 (Tx#1 to Tx#6) in arrangement example 3 (see FIGS. 20 to 23, for example).

As shown in FIG. 24, the transmission period T for each transmission antenna 108 of Tx#1 to Tx#6 is 6Tr. As shown in FIG. 24, a set of transmit antennas 108 corresponding to co-located virtual antennas (for example, Tx#1 and Tx#4, Tx#2 and Tx#5, and Tx#3 and Tx# 6) Every transmission period T' is 3Tr. In other words, the transmission period T'=T/2 of the set of transmit antennas 108 forming the co-located virtual antennas.

Therefore, with the antenna arrangement of arrangement example 3, the maximum relative velocity _v'max (or the Doppler frequency range) is expanded to twice the maximum relative velocity _vmax based on the transmission interval T for each transmitting antenna 108. be.

(Arrangement example 4: Example of Nt=6 and Na=8)
In arrangement example 4, an antenna arrangement example in which the number of transmitting antennas 108 is Nt=6 (for example, Tx#1 to Tx#6) and the number of receiving antennas 202 is Na=8 will be described. Also, in Arrangement Example 4, both the transmitting antenna 108 and the receiving antenna 202 are two-dimensional planar arrays.

FIG. 25 shows an example of the antenna arrangement of the transmitting antenna 108 and the receiving antenna 202 according to the arrangement example 4, and the arrangement of the virtual reception array.

In FIG. 25, the set of Tx#2 and Tx#3 and the set of Tx#4 and Tx#5 are arranged with an interval of 2d in the first axis direction. In addition, Tx#3 and Tx#5 are arranged with a distance of d in the first axis direction and a distance of 2d in the second axis direction from Tx#1. Similarly, Tx#2 and Tx#4 are separated from Tx#6 by a distance of d in the first axis direction and by a distance of 2d in the second axis direction. In addition, in FIG. 25, two sets of four antenna elements (a set of Rx#1 to Rx#4 and a set of Rx#5 to Rx#8) arranged with an interval d in the first axis direction are They are arranged at intervals of 2d in two axial directions.

In this case, as shown in FIG. 25, in the virtual receiving array arrangement (Nt×Na=48 virtual antennas), Tx#1 and Tx#3, Tx#2 and Tx#4, Tx#3 and Tx#5 , Tx#4 and Tx#6, Tx#1 and Tx#5, and Tx#2 and Tx#6, respectively, are arranged at the same position and overlap once. Also, virtual antennas respectively corresponding to the set of Tx#1, Tx#3 and Tx#5 and the set of Tx#2, Tx#4 and Tx#6 are arranged at the same position twice. be.

In FIG. 25, a double-overlapping virtual receive array is placed in the center, and radially-overlapping one-time virtual antennas and non-overlapping virtual antennas are placed. Therefore, the virtual reception array arrangement shown in FIG. 25 is arranged such that the received power in the center of the virtual reception array becomes higher. In this way, the distribution is spatially like a window function, and the beam pattern formed by the array has lower sidelobe levels and the risk of false detection is reduced compared to the case where similar receiving arrays are arranged without overlapping. . It should be noted that the overlapped signals of the virtual reception array can be used for direction-of-arrival estimation after processing such as adding, averaging, or applying a window function to the spatial power distribution.

FIG. 26 shows an example of transmission timings of each of the transmission antennas 108 (Tx#1 to Tx#6) in Arrangement Example 4 (see FIG. 25, for example).

As shown in FIG. 26, the transmission period T for each transmission antenna 108 of Tx#1 to Tx#6 is 6Tr. As shown in FIG. 26, a set of transmit antennas 108 corresponding to virtual antennas arranged at the same position twice (for example, a set of Tx#1, Tx#3 and Tx#5, and Tx#2, The transmission period T' for each set of Tx#4 and Tx#6) is 2Tr. In other words, the transmission period T′=T/3 of the set of transmit antennas 108 forming the co-located virtual antennas.

Therefore, with the antenna arrangement in FIG. 25, the maximum relative velocity v' _max (or the Doppler frequency range) is expanded to three times the maximum relative velocity v _max based on the transmission interval T for each transmitting antenna 108. .

In addition, in FIG. 25, the virtual antenna corresponding to each transmitting antenna 108 is arranged to overlap the virtual antennas corresponding to other transmitting antennas at a plurality of arrangement positions, so the quality of the received signal in the radar device 10 (for example, SNR) can be improved.

Note that the antenna arrangement shown in FIG. 26 may be applied instead of the antenna arrangement shown in FIG. FIG. 26 shows an antenna arrangement obtained by rotating the arrangement of the transmitting antennas 108 shown in FIG. 25 by 90 degrees. In this case, as shown in FIG. 26, the virtual antennas corresponding to the set of Tx#1, Tx#2, Tx#3 and Tx#4 are arranged at three identical positions with three overlaps. 25, the maximum value of the relative velocity can be increased, and the quality of the received signal (for example, SNR) in the radar device 10 can be improved.

FIG. 28 shows an example of transmission timing of each transmission antenna 108 (Tx#1 to Tx#6) in FIG.

As shown in FIG. 28, the transmission period T for each transmission antenna 108 of Tx#1 to Tx#6 is 8Tr. Also, as shown in FIG. 28 , the transmission period for each set (Tx#1, Tx#2, Tx#3 and Tx#4) of the transmitting antennas 108 corresponding to the virtual antennas arranged three times at the same position T' is 2Tr. Also, the transmission period T' for each of Tx#5 and Tx#6, which are the transmitting antennas 108 corresponding to the virtual array that overlaps twice, is 2Tr.

When the radar apparatus 10 estimates the speed using the virtual reception array with these transmission periods (T'=2Tr), the transmission period T'=Torg/3 if the conventional transmission period Torg=6Tr. Therefore, v' _max (or Doppler frequency range) is expanded to three times the maximum relative velocity v _max based on the transmission interval Torg for each transmit antenna 108 .

Also, the radar apparatus 10 may be configured to estimate the speed using the signals of the virtual reception array with the transmission period T'=4Tr. As a result, the radar apparatus 10 receives the signals of the pairs of transmitting antennas (the pair of Tx#1 and Tx#2 and the pair of Tx#3 and Tx#4) corresponding to the virtual reception array that is overlapped once in FIG. , Tx#5 and Tx#6, and the signals of the three overlapping virtual reception arrays may be added to perform speed estimation processing and CFAR processing.

When the radar apparatus 10 performs velocity estimation using a virtual reception array with these transmission periods (T'=4Tr), the transmission period T'=2T/3 if the conventional transmission period Torg=6Tr. Therefore, v′ _max (or Doppler frequency range) is expanded to 1.5 times the maximum relative velocity value v _max based on the transmission interval Torg for each transmit antenna 108 . Although the maximum speed obtained is smaller than in the case of the transmission period T'=4Tr, since there are many signals of the virtual reception array used for speed estimation, the quality (for example, SNR) of the received signal used for CFAR processing can be improved. can.

In the configurations shown in FIGS. 27 and 28, the radar device 10 can select the receiving process as described above. For example, the radar device 10 performs processing using a received signal with a transmission cycle T'=2Tr when it is desired to detect a reflecting object with a high reflection intensity and a high relative speed, and when the reflection intensity is lower than the above, the transmission cycle T' Processing using a received signal of =4Tr can also be performed.

Moreover, it is not necessary to multiplex all the antennas of the transmission antennas 108 . For example, the radar apparatus 10 continuously transmits radar transmission signals using only Tx#1, Tx#2, Tx#3, and Tx#4 corresponding to overlapping virtual reception antennas among the transmission antennas shown in FIG. Send. As a result, the radar device 10 can estimate the speed using the signals of the virtual reception array with the transmission period T'=Tr. If the conventional transmission period Torg=6Tr, then the transmission period T'=Torg/6. Therefore, v′ _max (or Doppler frequency range) is expanded to 6 times the maximum relative velocity value v _max based on the transmission interval T org for each transmit antenna 108 . In this way, the radar device 10 may adopt a configuration capable of handling higher speeds. For example, the radar device 10 may have a configuration capable of responding to higher speeds and a configuration capable of improving the accuracy of direction-of-arrival estimation by switching the transmission timing pattern of the transmission antenna depending on the detection target. In addition, although this arrangement example of the present embodiment in which a large number of virtual reception antennas overlap is described as an example, it may be applied without being limited to this.

(Arrangement Example 5: Example of Nt=3 and Na=4)
In arrangement example 5, an antenna arrangement example in which the number of transmitting antennas 108 is Nt=3 (for example, Tx#1 to Tx#3) and the number of receiving antennas 202 is Na=4 will be described. In arrangement example 5, the transmitting antenna 108 is a one-dimensional linear array, and the receiving antenna 202 is a two-dimensional planar array.

<Arrangement example 5-1>
FIG. 29 shows an example of the antenna arrangement of the transmitting antennas 108 and the receiving antennas 202 according to the arrangement example 5-1, and the arrangement of the virtual reception array.

In FIG. 29, Tx#1 to Tx#3 are linearly arranged at intervals of d in the first axis direction, for example. In the receiving antenna 202, for example, two sets of two elements (a set of Rx#1 and Rx#2 and a set of Rx#3 and Rx#4) are arranged at an interval d in the second axis direction. The two sets of elements are spaced 2d apart in the axial direction.

In this case, as shown in FIG. 29, in the virtual receiving array arrangement (Nt×Na=12 virtual antennas), the virtual antennas corresponding to Tx#1 and Tx#3 are arranged at two locations in the second axis direction. It is placed in duplicate (overlapping once).

Accordingly, in FIG. 29, the radar apparatus 10 can improve the quality (for example, SNR) of received signals by using received signals received by virtual antennas at a plurality of placement positions.

<Arrangement Example 5-2>
FIG. 30 shows an example of the antenna arrangement of the transmitting antennas 108 and the receiving antennas 202 according to arrangement example 5-2, and the arrangement of the virtual reception array.

FIG. 30 shows that in the receiving antenna 202, compared with the antenna arrangement of arrangement example 5-1 (FIG. 29), the antenna spacing (2d) in the first axis direction is the same, and the arrangement of Rx#2 and Rx#4 This is an antenna arrangement in which the position is shifted to the right by a distance d in the direction of the first axis. In the antenna arrangement shown in FIG. 30 as well, similar to FIG. The received signal quality (eg, SNR) can be improved.

<Arrangement Example 5-3>
FIG. 31 shows an example of the antenna arrangement of the transmitting antennas 108 and the receiving antennas 202 and the arrangement of the virtual receiving array according to the arrangement example 5-3.

In FIG. 31, the total number Nt of transmitting antennas 108 is 3, which are indicated by Tx#1 to Tx#3, respectively. The transmitting antennas Tx#1 to Tx#3 are arranged at regular intervals of _dH in the first axis direction. Here, the basic distance d _H in the direction of the first axis is, for example, d _H =0.5λ. The total number Na of the receiving antennas 202 is four, which are indicated by Rx#1 to Rx#4, respectively. The receiving antennas Rx#1 to Rx#4 are arranged in the first axis direction at intervals of [3,2,3]×d _H .

As shown in FIG. 31, at the position of the virtual antenna VA#6, there are a virtual antenna configured by a transmitting antenna Tx#3 and a receiving antenna Rx#2, a transmitting antenna Tx#1 and a receiving antenna Rx#3. A virtual antenna configured by is overlapped.

FIG. 32 shows an example of transmission timing of each transmission antenna 108 (Tx#1 to Tx#3) in FIG. The transmission cycle T for each transmission antenna 108 of Tx#1 to Tx#3 is 4Tr. As shown in FIG. 32, the transmission period T' for each pair of transmission antennas 108 (Tx#1, Tx#3) corresponding to virtual antennas arranged at the same position with one overlap is 2Tr. Also, as shown in FIG. 32, the transmission cycle T' of the transmission antenna Tx#2 is also 2Tr. Therefore, the radar apparatus 10 may perform speed estimation processing and CFAR processing by adding the virtual reception array by Tx#2 in addition to the signal of the virtual reception array that overlaps once.

When speed estimation is performed using virtual reception arrays with these transmission periods (T'=2Tr), the transmission period T'=2T/3 if the conventional transmission period Torg=3Tr. Therefore, v′ _max (or Doppler frequency range) is expanded to 1.5 times the maximum relative velocity value v _max based on the transmission interval Torg for each transmit antenna 108 .

There is also an advantage in SNR for this transmission method. Normally, as shown in FIG. 32, from Tx#2 which does not overlap the virtual antennas (if Nt = 3, N = 3), the radar transmission signal is transmitted only once every N times of transmission, so the overall The number of transmissions is Nc. However, the total number of transmissions is 2Nc because the radar transmission signal is transmitted twice out of the number of transmissions N from Tx#2 that does not overlap the virtual antennas as described above. In addition, since these transmissions are all transmitted at intervals of 2Tr, in-phase addition of received signals is possible by FFT, and an improvement in SNR can be expected.

(Variation 5 of one embodiment)
The configuration of the radar device according to one aspect of the present disclosure is not limited to the configuration shown in FIG. 1 . For example, the configuration of the radar device 10a shown in FIG. 33 may be used. In FIG. 33, the configuration of the radar receiver 200 is the same as in FIG. 1, so detailed configuration is omitted.

In the radar apparatus 10 shown in FIG. 1 , in the radar transmission section 100 , the transmission switching section 106 selectively switches the output from the radar transmission signal generation section 101 to any one of the plurality of transmission radio sections 107 . On the other hand, in the radar device 10a shown in FIG. 33, in the radar transmission section 100a, the output (radar transmission signal) from the radar transmission signal generation section 101 is subjected to transmission wireless processing by the transmission wireless section 107a, and the transmission is switched. The output of the transmission radio section 107a is selectively switched to one of the plurality of transmission antennas 108 by the section 106a.

The configuration of the radar device 10a shown in FIG. 33 also provides the same effects as those of the above embodiment.

(Variation 6 of one embodiment)
In the above-described embodiment, the radar transmission section 100 uses a pulse compression radar that transmits a pulse train by phase-modulating or amplitude-modulating it, but the modulation method is not limited to this. For example, the present disclosure is also applicable to radar schemes using frequency modulated pulse waves such as chirp pulses.

FIG. 34 shows an example of a block diagram of a radar device 10b when a radar system using chirp pulses (for example, fast chirp modulation) is applied. In addition, in FIG. 34, the same reference numerals are assigned to the same configurations as in FIG. 1, and the description thereof will be omitted.

First, transmission processing in the radar transmission unit 100b will be described.

In radar transmission section 100 b , radar transmission signal generation section 401 has modulation signal generation section 402 and VCO (Voltage Controlled Oscillator) 403 .

For example, as shown in FIG. 35, the modulated signal generator 402 periodically generates a sawtooth-shaped modulated signal. Here, the radar transmission cycle is Tr.

VCO 403 outputs a frequency modulated signal (in other words, a frequency chirp signal) to transmission radio section 107 based on the radar transmission signal output from modulated signal generation section 402 . The frequency-modulated signal is amplified by transmission radio section 107 and radiated into space from transmission antenna 108 switched by transmission switching section 106 . For example, in each of the first transmitting antenna 108 to the Nt-th transmitting antenna 108, the radar transmission signal is transmitted at a transmission interval of Np (=Nt×Tr) period.

The directional coupling section 404 extracts a part of the frequency modulated signal and outputs it to each receiving radio section 501 (mixer section 502) of the radar receiving section 200b.

Next, reception processing in the radar reception unit 200b will be described.

The receiving radio unit 501 of the radar receiving unit 200b mixes the received reflected wave signal with the frequency modulated signal (the signal input from the directional coupling unit 404) which is the transmission signal in the mixer unit 502, and the LPF 503 let it pass. As a result, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is extracted. For example, as shown in FIG. 35, the difference frequency between the frequency of the transmission signal (transmission frequency modulated wave) and the frequency of the received signal (reception frequency modulated wave) is obtained as the beat frequency.

The signal output from the LPF 503 is converted into discrete sample data by the A/D conversion section 208b in the signal processing section 207b.

The R-FFT section 504 performs FFT processing on N _data pieces of discrete sample data obtained in a predetermined time range (range gate) for each transmission period Tr. As a result, the signal processing unit 207b outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). Note that, during FFT processing, the R-FFT unit 504 may multiply window function coefficients such as a Han window or a Hamming window. Side lobes generated around the beat frequency peak can be suppressed by using the window function coefficients.

Here, AC_RFT _z (fb, M) represents the beat frequency spectrum response output from the R-FFT unit 504 in the z-th signal processing unit 207b obtained by the M-th chirp pulse transmission. Here, fb is the FFT index number (bin number), and fb=0, . . . , N _data /2. A smaller frequency index fb indicates a beat frequency with a shorter delay time of the reflected wave signal (in other words, a closer distance to the target).

The output switching unit 211 in the z-th signal processing unit 207b outputs the output of the R-FFT unit 504 for each radar transmission cycle Tr based on the switching control signal input from the switching control unit 105, as in the above embodiment. is selectively switched to one of the Nt Doppler analysis units 212 and output.

Hereinafter, as an example, the switching control signal in the M-th radar transmission cycle Tr[M] is represented by Nt-bit information [bit ₁ (M), bit ₂ (M), . . . , bit _Nt (M)]. For example, in the switching control signal of the M-th radar transmission cycle Tr[M], if the ND-th bit bit _ND (M) (where ND is any of 1 to Nt) is '1', output The switching unit 211 selects (turns ON) the ND-th Doppler analysis unit 212 . On the other hand, in the switching control signal of the M-th radar transmission cycle Tr[M], when the ND-th bit bit _ND (M) is '0', the output switching unit 211 switches to the ND-th Doppler analysis unit 212 is unselected (in other words, OFF). Output switching section 211 outputs the signal input from R-FFT section 504 to selected Doppler analysis section 212 .

As described above, the selection of each Doppler analysis unit 212 is sequentially turned on in Np (=Nt×Tr) cycles. The switching control signal repeats the above content Nc times. Further, as in the above embodiment, in the virtual reception array, the selection of the Doppler analysis unit 212 corresponding to the transmission antenna 108 corresponding to the virtual antennas overlappingly arranged at the same position (in other words, the transmission timing of the transmission antenna 108 ) are set at equal intervals in the transmission cycle of each transmission antenna 108 .

The transmission start time of the transmission signal in each transmission radio section 107 does not have to be synchronized with the period Tr. For example, each transmission radio section 107 may set different transmission delays _{Δ 1} , Δ ₂ , .

The z-th (z=1, . . . , Na) signal processing unit 207b has Nt Doppler analysis units 212 .

The Doppler analysis unit 212 performs Doppler analysis on the output from the output switching unit 211 for each beat frequency index fb.

For example, if Nc is a power of 2 value, Fast Fourier Transform (FFT) processing can be applied in Doppler analysis.

For example, among the w-th output in the ND-th Doppler analysis unit 212 of the z-th signal processing unit 207b, the output in the superimposed virtual reception array is expressed by the Doppler at the beat frequency index fb as shown in the following equation. The Doppler frequency response FT_CI _z ^(ND) (fb, f _s , w) for frequency index f _s is shown. Note that ND=1 to Nt, and w is an integer of 1 or more. Also, N _va indicates the number of antennas corresponding to the superimposed virtual reception array, and N indicates the number of times of transmission within one period. Also, j is an imaginary unit, and z=1 to Na.

On the other hand, for example, among the w-th outputs of the ND-th Doppler analysis unit 212 of the z-th signal processing unit 207b, the outputs of the non-overlapping virtual reception arrays other than the superimposed virtual reception arrays are expressed by the following equation: Doppler frequency response FT_CI _z ^(ND) (fb, f _u , w) for Doppler frequency index f _u at beat frequency index f b is shown as shown. Note that ND=1 to Nt, ND=1 to Nt, and w is an integer of 1 or more. Also, j is an imaginary unit, and z=1 to Na.

The processing of the signal correction unit 213, the CFAR unit 213, and the direction estimation unit 214 subsequent to the signal processing unit 207b is an operation in which the discrete time k described in the above embodiment is replaced by the beat frequency index fb, so detailed description thereof will be omitted. omitted.

With the configuration and operation described above, this variation can also obtain the same effects as those of the above-described embodiment. Note that in a variation of an embodiment described later, a frequency chirp signal can be similarly applied as a radar transmission signal, and the same effects as in the case of using a coded pulse signal can be obtained.

Also, the beat frequency index fb described above may be converted into distance information and output. The following equation can be used to convert the beat frequency index fb into the distance information R(fb). Here, Bw represents the frequency modulation bandwidth of the frequency chirp signal generated by frequency modulation, and _C0 represents the speed of light.

An embodiment according to the present disclosure has been described above.

[Other embodiments]
(1) In the radar device 10 shown in FIG. 1, the radar transmission section 100 and the radar reception section 200 may be separately arranged at physically separate locations. In addition, in the radar receiver 200 shown in FIG. 1, the direction estimator 214 and other components may be individually arranged at physically separate locations.

(2) Although not shown, the radar device 10 includes, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, and a working memory such as a RAM (Random Access Memory). have. In this case, the functions of the respective units described above are realized by the CPU executing the control program. However, the hardware configuration of the radar device 10 is not limited to this example. For example, each functional unit of the radar device 10 may be realized as an IC (Integrated Circuit), which is an integrated circuit. Each functional unit may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them.

Various embodiments have been described above with reference to the drawings, but it goes without saying that the present disclosure is not limited to such examples. It is obvious that a person skilled in the art can conceive of various modifications or modifications within the scope described in the claims, and these also belong to the technical scope of the present disclosure. Understood. Also, the components in the above embodiments may be combined arbitrarily without departing from the gist of the disclosure.

In each of the above-described 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.

Also, each functional block used in the description of each of the above embodiments is typically implemented 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 an input terminal and an output terminal. These may be made into one chip individually, or may be made into one chip so as to include part or all of them. Although LSI is used here, it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Also, the method of circuit integration is not limited to LSI, and may be implemented using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, and a reconfigurable processor (Reconfigurable Processor) that can reconfigure connections or settings of circuit cells inside the LSI may be used.

Furthermore, if an integration technology that replaces the LSI appears due to advances in semiconductor technology or another derived technology, the technology may naturally be used to integrate the functional blocks. Application of biotechnology, etc. is possible.

<Summary of this disclosure>
A radar device according to the present disclosure includes a plurality of transmitting antennas and a transmitting circuit that transmits a transmission signal using the plurality of transmitting antennas, and is configured based on the plurality of receiving antennas and the plurality of transmitting antennas. At least two of the virtual reception arrays including a plurality of virtual antennas are arranged in the same position, and transmission is sequentially performed from the transmission antennas corresponding to the at least two virtual antennas of the plurality of transmission antennas. Transmission intervals of the transmission signals are equal intervals.

In the radar device of the present disclosure, the transmission circuit transmits the transmission signal in a predetermined transmission pattern using the plurality of antennas.

In the radar device of the present disclosure, in the transmission pattern, the plurality of antennas includes a transmission antenna that transmits the transmission signal multiple times.

In the radar apparatus of the present disclosure, the transmitting antenna that transmits the transmission signal multiple times in the transmission pattern is a transmitting antenna other than the transmitting antenna that is farthest from the center of gravity in the antenna arrangement of the plurality of transmitting antennas.

In the radar device of the present disclosure, the plurality of virtual antennas corresponding to at least one transmitting antenna among the plurality of transmitting antennas are arranged to overlap the virtual antennas corresponding to other transmitting antennas at a plurality of arrangement positions. be.

In the radar device of the present disclosure, the transmission circuit continuously transmits the transmission signal from transmission antennas corresponding to the at least two virtual antennas among the plurality of transmission antennas.

In the radar device of the present disclosure, the transmission signals are simultaneously transmitted from at least two transmission antennas out of three or more transmission antennas, and the arrangement positions of the at least two virtual antennas are the phase centers between the at least two transmission antennas. Determined based on points.

The radar apparatus of the present disclosure further comprises a receiving circuit that receives reflected wave signals of the transmission signal reflected by a target using three or more receiving antennas, and the receiving circuit includes the three or more and combining the reflected wave signals received by at least two receiving antennas out of the receiving antennas, and positioning positions of the at least two virtual antennas are determined based on a phase center point between the at least two receiving antennas.

In the radar device of the present disclosure, the plurality of transmitting antennas are two-dimensionally arranged.

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

Reference Signs List 10, 10a, 10b radar device 100, 100a, 100b radar transmission section 101, 101a, 401 radar transmission signal generation section 102 code generation section 103 modulation section 104, 503 LPF
105 switching control unit 106, 106a transmission switching unit 107, 107a transmission radio unit 108 transmission antenna 111 code storage unit 112 DA conversion unit 200, 200b radar reception unit 201 antenna system processing unit 202 reception antenna 203, 501 reception radio unit 204 amplifier 205 Frequency converter 206 Quadrature detector 207, 207b Signal processing unit 208, 208b, 209 AD conversion unit 210 Correlation calculation unit 211 Output switching unit 212 Doppler analysis unit 213 CFAR unit 214 Direction estimation unit 300 Reference signal generation unit 402 Modulation signal generation unit 403 VCOs
404 directional coupling section 502 mixer section 504 R-FFT section

Claims (9)

a plurality of transmit antennas;
a plurality of receiving antennas;
Every predetermined number of transmission cycles the plurality of transmit antennaseach transmitting antenna ofofat least oncea transmission circuit that transmits a transmission signal using
a receiving circuit for receiving a reflected wave signal in which the transmission signal is reflected by a target;
and
Said A virtual receive array comprising a plurality of receive antennas and a plurality of virtual antennas configured based on the plurality of transmit antennas.teeth,Placement position is the samevirtual antenna containing at least two
The transmission circuit is SaidPlacement position is the samecorresponds to the virtual antennaAll oftransmitting antennausing, at intervals shorter than the predetermined number of transmission cycles,said transmission signalto send,
radar equipment. The transmission circuit transmits the transmission signal in a predetermined transmission pattern using the plurality of transmission antennas.
The radar device according to claim 1. In the transmission pattern, the transmission antennas corresponding to the virtual antennas having the same placement position include transmission antennas that transmit the transmission signal multiple times.
The radar device according to claim 2. In the transmission pattern, the transmission antenna that transmits the transmission signal multiple times is a transmission antenna other than the transmission antenna farthest from the center of gravity in the antenna arrangement of the plurality of transmission antennas.
The radar device according to claim 3. The plurality of virtual antennas corresponding to at least one transmitting antenna among the plurality of transmitting antennas are arranged to overlap with the virtual antennas corresponding to other transmitting antennas in a plurality of arrangement positions.
The radar device according to claim 1. wherein the transmission circuit continuously transmits the transmission signal from, among the plurality of transmission antennas, a transmission antenna corresponding to a virtual antenna having the same arrangement position ;
The radar device according to claim 1. the plurality of transmitting antennas are three or more transmitting antennas;
SaidThe transmission signals are simultaneously transmitted from at least two transmission antennas out of three or more transmission antennas,
SaidPlacement position is the sameThe placement position of the virtual antenna is determined based on the phase center point between the at least two transmitting antennas;
The radar device according to claim 1. The plurality of receiving antennas are three or more receiving antennas,
The receiving circuit combines the reflected wave signals received by at least two receiving antennas out of the three or more receiving antennas,
SaidPlacement position is the sameThe placement position of the virtual antenna is determined based on the phase center point between the at least two receiving antennas;
The radar device according to claim 1. The plurality of transmitting antennas are two-dimensionally arranged,
The radar device according to claim 1.

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