JP7109710B2 - Radar device and radar signal processing method - Google Patents

Description

The present disclosure relates to radar equipment and radar signal processing methods.

Conventionally, a radar device using a plurality of antennas has been developed. For example, Patent Literature 1 discloses a radar apparatus using a plurality of transmitting antennas and a plurality of receiving antennas. In the radar device described in Patent Document 1, a plurality of transmitting antennas and a plurality of receiving antennas are arranged so as to be orthogonal to each other. As a result, it is intended to expand the antenna aperture in the horizontal direction and to expand the antenna aperture in the vertical direction.

WO2018/122926

By using a plurality of antennas, one antenna having a large aperture can be equivalently realized. Normally, the antenna aperture length in a radar system is proportional to the angular resolution of the radar system. Therefore, by using a plurality of antennas, the angular resolution of the radar system can be improved.

However, in this case, a situation occurs in which the angle value corresponding to the target is different for each antenna. That is, a situation occurs in which the target is located in the near field with respect to multiple antennas. As a result, integration for angle measurement becomes difficult, and there is a problem that the amount of calculation for angle measurement increases.

The present disclosure has been made to solve the problems described above, and aims to reduce the amount of computation for angle measurement in a radar device using a plurality of antennas.

A radar device according to the present disclosure includes a plurality of antennas including one or more transmitting antennas and a plurality of receiving antennas, and a radar signal processing device, wherein the radar signal processing device comprises a plurality of by grouping the receiving antennas to set a plurality of integration groups; A first integration unit that generates a plurality of first integration signals respectively corresponding to the integration groups of and a second integration unit that generates a second integration signal by performing second coherent integration on the plurality of first integration signals An integrator and an angle calculator that calculates an angle value corresponding to each target candidate using the second integrated signal.

According to the present disclosure, since it is configured as described above, integration for angle measurement can be facilitated. As a result, the amount of calculation for angle measurement can be reduced.

1 is a block diagram showing a main part of a radar device according to Embodiment 1; FIG. 3 is a block diagram showing the main part of the first antenna module in the radar device according to Embodiment 1; FIG. 3 is a block diagram showing the essential parts of a first signal processor in the radar device according to Embodiment 1; FIG. 3 is a block diagram showing the hardware configuration of the main part of the first signal processor in the radar device according to Embodiment 1; FIG. 4 is a block diagram showing another hardware configuration of the main part of the first signal processor in the radar device according to Embodiment 1; FIG. 4 is a block diagram showing another hardware configuration of the main part of the first signal processor in the radar device according to Embodiment 1; FIG. 4 is a flow chart showing the operation of the first signal processor in the radar device according to Embodiment 1; FIG. 4 is an explanatory diagram showing an example of a plurality of distance/velocity signals, distance bin numbers corresponding to individual distance/velocity signals, and velocity bin numbers corresponding to individual distance/velocity signals; FIG. 4 is an explanatory diagram showing an example of an incoherent integrated signal, a distance bin number corresponding to the incoherent integrated signal, and a velocity bin number corresponding to the incoherent integrated signal; FIG. 4 is an explanatory diagram showing an example of arrival distance differences and azimuth angles when one target is located in the far field with respect to a plurality of receiving antennas; FIG. 4 is an explanatory diagram showing an example of arrival distance difference and azimuth angle when one target is located in the near field with respect to a plurality of receiving antennas; FIG. 4 is an explanatory diagram showing an example of a plurality of integral groups; FIG. 4 is an explanatory diagram showing an example of one integration group out of a plurality of integration groups; FIG. 4 is an explanatory diagram showing examples of receiving antenna positions corresponding to individual integration groups, transform start azimuth angles corresponding to individual integration groups, and transform end azimuth angles corresponding to individual integration groups; FIG. 10 is an explanatory diagram showing an example of azimuth bin numbers indicating the maximum power of the first integrated signal corresponding to each integration group; FIG. 11 is an explanatory diagram showing another example of azimuth bin numbers indicating the maximum power of the first integrated signal corresponding to each integration group; FIG. 4 is an explanatory diagram showing an example of a plurality of first integration signals respectively corresponding to a plurality of integration groups and a second integration signal corresponding to the plurality of first integration signals; FIG. 10 is a block diagram showing a main part of a radar device according to Embodiment 2; FIG. FIG. 10 is a block diagram showing a main part of a second antenna module in the radar device according to Embodiment 2; FIG. 4 is a block diagram showing main parts of a first signal processor and a second signal processor in a radar device according to Embodiment 2; FIG. 4 is an explanatory diagram showing an example of a plurality of integration groups corresponding to a plurality of antenna modules one-to-one; FIG. 4 is an explanatory diagram showing an example of a plurality of antenna arrangement intervals different from each other, and an example of a state in which the plurality of antennas are virtually arranged at equal intervals; FIG. 4 is an explanatory diagram showing an example of a state in which the grating level exceeds a desired level; FIG. 4 is an explanatory diagram showing an example of a state in which the grating level is suppressed below a desired level; FIG. 9 is a block diagram showing the hardware configuration of the main part of a second signal processor in the radar device according to Embodiment 2; FIG. 9 is a block diagram showing another hardware configuration of the main part of the second signal processor in the radar device according to Embodiment 2; FIG. 9 is a block diagram showing another hardware configuration of the main part of the second signal processor in the radar device according to Embodiment 2; 9 is a flow chart showing the operation of a second signal processor in the radar device according to Embodiment 2; 9 is a flow chart showing the operation of the first signal processor in the radar device according to Embodiment 2;

Hereinafter, in order to describe this disclosure in more detail, embodiments for carrying out this disclosure will be described with reference to the accompanying drawings.

Embodiment 1.
FIG. 1 is a block diagram showing a main part of a radar device according to Embodiment 1. FIG. 2 is a block diagram showing a main part of the first antenna module in the radar device according to Embodiment 1. FIG. 3 is a block diagram showing a main part of the first signal processor in the radar device according to Embodiment 1. FIG. A radar apparatus according to Embodiment 1 will be described with reference to FIGS. 1 to 3. FIG.

The radar device 1 includes a plurality of antenna groups. Each antenna group contains one or more antennas. More specifically, the plurality of antenna groups includes one or more transmit antenna groups and one or more receive antenna groups. Each transmit antenna group includes one or more transmit antennas. Each receive antenna group includes a plurality of receive antennas.

Here, the radar device 1 includes one or more antenna modules. Each antenna group is provided in a corresponding one of the one or more antenna modules.

That is, each antenna module includes at least one transmit antenna group and at least one receive antenna group. Alternatively, each antenna module contains at least one receiving antenna group. Alternatively, each antenna module contains at least one transmit antenna group.

Hereinafter, an antenna module including at least one transmitting antenna group and at least one receiving antenna group may be referred to as a "first antenna module". Also, an antenna module including at least one receiving antenna group may be referred to as a "second antenna module". Also, an antenna module including at least one transmitting antenna group may be referred to as a "third antenna module".

Individual antenna modules are provided, for example, in vehicles. More specifically, the individual antenna modules are provided, for example, on the edge of the front window of the vehicle, the edge of the rear window of the vehicle, the pillar of the vehicle, the front bumper of the vehicle, or the rear bumper of the vehicle. ing.

Hereinafter, in Embodiment 1, an example in which one first antenna module is provided will be mainly described. Also, in the second embodiment, an example in which one first antenna module and a plurality of second antenna modules are provided will be mainly described.

As shown in FIG. 1, the radar device 1 includes a first antenna module 2_1, a first signal processor 3_1 and a display 4. As shown in FIG. The first antenna module 2_1 includes a transmitter 5 and a first receiver 6_1. The main part of the radar signal processing device 7 is configured by the first signal processor 3_1.

As shown in FIG. 2, the transmitter 5 includes a local oscillation signal generator 11, a code modulator 12, a plurality of transmitters 13 and a plurality of transmission antennas 14. FIG. A plurality of transmitting antennas 14 constitute a transmitting antenna group 15 . The first receiving section 6_1 includes a plurality of receiving antennas 21, a plurality of receivers 22 and a plurality of analog-digital converters (hereinafter referred to as "A/D converters") 23. A reception antenna group 24 is configured by the plurality of reception antennas 21 .

In the figure, N _Tx indicates the number of transmission channels (hereinafter referred to as "the number of transmission channels"). The number of transmission channels N _Tx corresponds to the number of transmission antennas 14 . That is, the number of transmission channels N _Tx corresponds to the number of transmitters 13 . Hereinafter, the number _nTx indicating an individual transmission channel may be referred to as a "transmission channel number".

In the figure, _NRx indicates the number of reception channels (hereinafter referred to as "the number of reception channels"). The number of reception channels N _Rx corresponds to the number of reception antennas 21 . That is, the number of reception channels N _Rx corresponds to the number of receivers 22 and the number of A/D converters 23 . Hereinafter, the number _nRx indicating an individual receiving channel may be referred to as a "receiving channel number".

Hereinafter, RF (Radio Frequency) signals transmitted by individual transmission antennas 14 or RF signals transmitted by individual transmission antennas 14 are collectively referred to as "transmission RF signals" or "transmission signals". Also, the RF signal received by each receiving antenna 21 is called a "reflected RF signal". An RF signal received by each receiving antenna 21 is called a "received RF signal".

The local oscillation signal generator 11 is for generating a local oscillation signal. The local oscillation signal generation section 11 outputs the generated local oscillation signal to the code modulation section 12 . Also, the local oscillation signal generator 11 outputs the generated local oscillation signal to each receiver 22 . The local oscillation signal generator 11 is configured by, for example, a dedicated circuit.

The code modulation section 12 acquires the local oscillation signal output from the local oscillation signal generation section 11 . The code modulation unit 12 performs code modulation on the acquired local oscillation signal. This produces a transmit RF signal corresponding to each transmit channel. The code modulation section 12 outputs the generated transmission RF signal to the corresponding transmitter 13 . The code modulation unit 12 is composed of, for example, a dedicated circuit.

Each transmitter 13 acquires the transmission RF signal output from the code modulation section 12 . Each transmitter 13 outputs the acquired transmission RF signal to the corresponding transmission antenna 14 .

Each transmission antenna 14 receives the transmission RF signal output by the corresponding transmitter 13 . Each transmission antenna 14 radiates the input transmission RF signal into space.

A transmit RF signal emitted by an individual transmit antenna 14 is reflected by the target. This produces a reflected RF signal. The generated reflected RF signal is incident on each receiving antenna 21 . Each receiving antenna 21 outputs a received RF signal corresponding to the incident reflected RF signal to the corresponding receiver 22 .

Each receiver 22 acquires the local oscillation signal output by the local oscillation signal generator 11 . Also, each receiver 22 acquires a received RF signal output from the corresponding receiving antenna 21 . Each receiver 22 uses the acquired local oscillation signal and the acquired received RF signal to generate a beat signal corresponding to the corresponding receive channel. Each receiver 22 outputs the generated beat signal to the corresponding A/D converter 23 .

That is, the N _Rx receivers 22 generate N _Rx beat signals corresponding to the N _Rx reception channels. A beat signal corresponding to each receive channel includes components corresponding to N _Tx transmit channels (ie, components corresponding to N _Tx transmit RF signals). A beat signal corresponding to each reception channel is hereinafter referred to as a "reception beat signal". Also, the received RF signal or the received beat signal may be collectively referred to as a "received signal".

Each A/D converter 23 acquires the received beat signal output by the corresponding receiver 22 . Each A/D converter 23 converts the acquired received beat signal from an analog signal to a digital signal. Each A/D converter 23 outputs the converted reception beat signal to the first signal processor 3_1.

As shown in FIG. 3, the first signal processor 3_1 includes a separation unit 31, a signal generation unit 32, an incoherent integration unit 33, a target candidate detection unit 34, an integration unit calculation unit 35, a first integration unit 36, a second integration It has a section 37 and an angle calculation section 38 . The integral unit calculator 35 , the first integrator 36 and the second integrator 37 constitute a main part of the coherent integrator 39 .

The separating section 31 acquires the received beat signal output from each A/D converter 23 . The separating unit 31 demodulates the acquired received beat signal. The received beat signal after demodulation is separated into signals corresponding to individual transmission channels and separated into signals corresponding to individual reception channels. The separation unit 31 outputs the received beat signal after demodulation to the signal generation unit 32 .

The signal generator 32 acquires the received beat signal output by the separator 31 . The signal generator 32 executes a discrete Fourier transform on the acquired received beat signal. As a result, a signal corresponding to the distance of each target candidate and the speed of each target candidate (hereinafter referred to as "distance/velocity signal") is generated for each transmission channel and each reception channel. The signal generator 32 outputs the generated distance velocity signal to the incoherent integrator 33 .

The incoherent integrator 33 acquires the distance velocity signal output by the signal generator 32 . The incoherent integrator 33 performs incoherent integration on the obtained distance velocity signal. The incoherent integrator 33 outputs a signal generated by executing such incoherent integration (hereinafter referred to as “incoherent integrated signal”) to the target candidate detector 34 .

The target candidate detection unit 34 acquires the incoherent integrated signal output from the incoherent integration unit 33 . The target candidate detection unit 34 uses the acquired incoherent integrated signal to calculate a distance value corresponding to each target candidate and a velocity value corresponding to each target candidate. This allows individual target candidates to be detected.

The target candidate detector 34 also identifies the distance/velocity signal corresponding to each target candidate, the velocity bin number corresponding to each target candidate, and the distance bin number corresponding to each target candidate. Here, the speed bin number indicates the sampling number for the speed direction. Also, the distance bin number indicates the sampling number for the distance direction. The target candidate detection unit 34 outputs the specified distance/velocity signal, the specified speed bin number, and the specified distance bin number to the coherent integration unit 39 .

The integration unit calculator 35 sets a plurality of groups for integration (hereinafter referred to as “integration groups” or “integration units”) by grouping the plurality of receiving antennas 21 . At this time, the integration unit calculation unit 35 sets a plurality of integration groups so that each target candidate is approximated to be positioned in the far field for each integration group.

For each target candidate, the first integration unit 36 performs coherent integration (hereinafter referred to as "first coherent integration") on signals corresponding to individual integration groups (hereinafter referred to as "integration group signals"). is. Here, as described above, a plurality of integration groups are set such that each target candidate is approximated to be located in the far field for each integration group. Thus, the first coherent integration is based on the far field even if the corresponding candidate target is located in the near field with respect to the receive antennas 24 .

The first integration section 36 outputs a signal generated by executing the first coherent integration (hereinafter referred to as “first integration signal”) to the second integration section 37 . That is, the first integration section 36 outputs a first integration signal corresponding to each integration group to the second integration section 37 .

The second integration section 37 acquires the first integration signal output by the first integration section 36 . The second integrator 37 performs coherent integration (hereinafter referred to as “second coherent integration”) on the obtained second integrated signal for each target candidate. The second integration section 37 outputs a signal (hereinafter referred to as “second integration signal”) generated by executing the second coherent integration to the angle calculation section 38 .

The angle calculator 38 acquires the second integrated signal output by the second integrator 37 . The angle calculator 38 uses the obtained second integrated signal to calculate an angle value corresponding to each target candidate. Each angle value indicates the azimuth angle of the corresponding target candidate.

The display device 4 acquires the distance value calculated by the target candidate detection unit 34 , the velocity value calculated by the target candidate detection unit 34 , and the angle value calculated by the angle calculation unit 38 . The display 4 displays these values.

Hereinafter, the processing executed by the separation unit 31 may be collectively referred to as “separation processing”. Also, the processing executed by the signal generation unit 32 may be collectively referred to as “signal generation processing”. Further, the processing executed by the incoherent integration unit 33 may be collectively referred to as “incoherent integration processing”. Further, the processing executed by the target candidate detection unit 34 may be collectively referred to as "target candidate detection processing". Further, the processing executed by the integration unit calculation section 35 may be collectively referred to as "integration unit calculation processing". Further, the processing executed by the first integration section 36 may be collectively referred to as "first integration processing". Also, the processing executed by the second integration section 37 may be collectively referred to as “second integration processing”. Further, the processing executed by the angle calculation unit 38 may be collectively referred to as "angle calculation processing".

Hereinafter, the functions of the separation unit 31 may be collectively referred to as "separation function". Also, the functions of the signal generation unit 32 may be collectively referred to as "signal generation function". Also, the functions of the incoherent integration section 33 may be collectively referred to as an "incoherent integration function". Also, the functions of the target candidate detection unit 34 may be collectively referred to as a "target candidate detection function". Also, the functions of the integration unit calculation section 35 may be collectively referred to as "integration unit calculation function". Also, the functions of the first integration section 36 may be collectively referred to as "first integration function". Also, the functions of the second integration section 37 may be collectively referred to as a "second integration function". Also, the functions of the angle calculator 38 may be collectively referred to as "angle calculation function".

Hereinafter, the code "F1" may be used for the separation function. Also, the code "F2" may be used for the signal generation function. Also, the code "F3" may be used for the incoherent integration function. Moreover, the code|symbol of "F4" may be used for a target candidate detection function. In addition, the code "F5" may be used for the integration unit calculation function. Also, the code "F6" may be used for the first integration function. Also, the code "F7" may be used for the second integration function. Also, the code "F8" may be used for the angle calculation function.

Next, the hardware configuration of the main part of the first signal processor 3_1 will be described with reference to FIGS. 4 to 6. FIG.

As shown in FIG. 4, the first signal processor 3_1 has a processor 41 and a memory . The memory 42 has a plurality of functions (including a separation function, a signal generation function, an incoherent integration function, a target candidate detection function, an integration unit calculation function, a first integration function, a second integration function, and an angle calculation function) F1. A program corresponding to F8 is stored. The processor 41 reads and executes programs stored in the memory 42 . Thereby, a plurality of functions F1 to F8 are realized.

Alternatively, the first signal processor 3_1 has a processing circuit 43 as shown in FIG. The processing circuit 43 executes processing corresponding to a plurality of functions F1-F8. Thereby, a plurality of functions F1 to F8 are realized.

Alternatively, the first signal processor 3_1 has a processor 41, a memory 42 and a processing circuit 43, as shown in FIG. The memory 42 stores programs corresponding to some of the functions F1 to F8. The processor 41 reads and executes programs stored in the memory 42 . This implements some of these functions. The processing circuit 43 also executes processing corresponding to the remaining functions among the plurality of functions F1 to F8. This implements such residual functionality.

The processor 41 is composed of one or more processors. The individual processors are, for example, CPUs (Central Processing Units), GPUs (Graphics Processing Units), microprocessors, microcontrollers or DSPs (Digital Signal Processors).

The memory 42 is composed of one or more nonvolatile memories. Alternatively, the memory 42 is composed of one or more nonvolatile memories and one or more volatile memories. That is, the memory 42 is composed of one or more memories. Each memory uses, for example, a semiconductor memory, a magnetic disk, an optical disk, a magneto-optical disk, a magnetic tape, or a magnetic drum. More specifically, each volatile memory uses RAM (Random Access Memory), for example. In addition, individual nonvolatile memories include, for example, ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), solid state drives, hard disk drives, flexible disks, A compact disc, a DVD (Digital Versatile Disc), a Blu-ray disc, or a mini disc is used.

The processing circuit 43 is composed of one or more digital circuits. Alternatively, the processing circuit 43 is composed of one or more digital circuits and one or more analog circuits. That is, the processing circuit 43 is composed of one or more processing circuits. Individual processing circuits are, for example, ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), FPGA (Field Programmable Gate Array), SoC (System on a Chip), or system LSI (Large Scale) is.

Here, when the processor 41 is composed of a plurality of processors, the correspondence relationship between the plurality of functions F1 to F8 and the plurality of processors is arbitrary. That is, each of the plurality of processors may read and execute a program corresponding to one or more functions among the plurality of functions F1 to F8. Processor 41 may include dedicated processors corresponding to each of the plurality of functions F1-F8.

Further, when the memory 42 is composed of a plurality of memories, the correspondence relationship between the plurality of functions F1 to F8 and the plurality of memories is arbitrary. That is, each of the plurality of memories may store a program corresponding to one or more functions among the plurality of functions F1 to F8. The memory 42 may include dedicated memory corresponding to each of the plurality of functions F1-F8.

Further, when the processing circuit 43 is composed of a plurality of processing circuits, the correspondence relationship between the plurality of functions F1 to F8 and the plurality of processing circuits is arbitrary. That is, each of the plurality of processing circuits may execute processing corresponding to one or more functions among the plurality of functions F1 to F8. The processing circuitry 43 may include dedicated processing circuitry corresponding to each of the plurality of functions F1-F8.

Next, the operation of the first signal processor 3_1 will be described with reference to the flowchart shown in FIG.

First, the separation unit 31 executes separation processing (step ST1). Next, the signal generator 32 executes signal generation processing (step ST2). Next, the incoherent integrator 33 performs incoherent integration processing (step ST3). Next, the target candidate detection unit 34 executes target candidate detection processing (step ST4). Next, the integration unit calculation section 35 executes integration unit calculation processing (step ST5). Next, the first integration section 36 executes the first integration process (step ST6). Next, the second integration section 37 executes a second integration process (step ST7). Next, the angle calculator 38 executes angle calculation processing (step ST8).

Next, detailed operation of the first antenna module 2_1 will be described.

Hereinafter, when an arbitrary element in an arbitrary mathematical expression is written in a sentence, the element is written in non-italic font regardless of whether the typeface of the relevant element in the mathematical expression is italic. Also, regardless of whether or not the typeface of the element in the mathematical expression is boldface, the element is written in non-boldface. This is primarily due to the demand for electronic filing. Regarding the typeface of each element, the typeface in the formula is correct.

<Local oscillation signal generator 11>
A local oscillation signal generator 11 generates a local oscillation signal L ₁ (h, t). The local oscillation signal generation unit 11 outputs the generated local oscillation signal L ₁ (h, t) to the code modulation unit 12 and individually receives the generated local oscillation signal L ₁ (h, t). output to the machine 22. A local oscillation signal L ₁ (h, t) is represented by the following equation (1).

In equation (1), j is the imaginary unit. φ ₀ is the initial phase of the local oscillation signal. h is the hit number. H is the number of hits. _AL is the amplitude of the local oscillation signal. f ₀ is the transmit frequency of the transmit RF signal. B ₀ is the modulation band of the transmitted RF signal. T ₀ is the modulation time. t is time. T _chp is the transmission repetition period of the transmission RF signal corresponding to the transmission channel number n _Tx . T _chp is represented by the following equation (2).

In equation (2), T _Tx is the transmission repetition period. T _Tx is represented by the following equation (3).

In equation ( ₃ ), T1 is the time until the next modulation is performed.

<Code modulation unit 12>
The code modulation section 12 acquires the local oscillation signal L ₁ (h, t) output by the local oscillation signal generation section 11 . The code modulation unit 12 performs code modulation on the acquired local oscillation signal L ₁ (h, t). At this time, the code modulation unit 12 adds a modulation code to the obtained local oscillation signal L ₁ (h, t) to obtain a transmission RF signal Tx(n _Tx , h, t) corresponding to each transmission channel. ).

In other words, the local oscillator signal L ₁ (h,t) corresponding to each transmission channel is code-modulated. Thereby, the orthogonality of the radio waves transmitted by the individual transmitting antennas 14 can be improved. As a result, separation of signals corresponding to individual transmission channels can be facilitated. In addition, it is possible to suppress the occurrence of interference between transmission channels, and it is possible to suppress the occurrence of interference with the radar device 1 due to external radio waves.

A specific example of code modulation will now be described. The following specific example uses a cyclic code that is a pseudo-random number.

First, the code modulation unit 12 cyclically shifts the cyclic code C ₀ (h) by the cyclic shift amount Δh(n _Tx ) according to the following equation (4). The cyclic code C ₀ (h) is preset. The cyclic shift amount Δh(n _Tx ) is set for each transmission channel.

A modulation code Code ₁ (n _Tx , h) corresponding to each transmission channel is generated by executing such a cyclic shift. The cyclic code C ₀ (h) may use an M sequence (Maximal Length Sequence), a Gold sequence, or a half-length sequence.

Next, the code modulation unit 12 uses the local oscillation signal L ₁ (h, t) and the modulation code Code ₁ (n _Tx , h) to calculate the transmission RF corresponding to each transmission channel according to the following equation (5). Generate a signal Tx(n _Tx , h, t).

Next, the code modulation unit 12 outputs the generated transmission RF signal Tx(n _Tx , h, t) to the corresponding transmitter 13 .

<Transmitter 13>
Each transmitter 13 acquires the transmission RF signal Tx(n _Tx , h, t) output by the code modulation section 12 . Each transmitter 13 outputs the acquired transmission RF signal Tx(n _Tx , h, t) to the corresponding transmission antenna 14 .

<Transmitting antenna 14>
Each transmission antenna 14 receives an input of transmission RF signal Tx(n _Tx , h, t) output by the corresponding transmitter 13 . Each transmission antenna 14 radiates the input transmission RF signal Tx(n _Tx , h, t) into space.

<Receiving antenna 21>
A transmit RF signal Tx(n _Tx ,h,t) emitted by an individual transmit antenna 14 is reflected by the target. This produces a reflected RF signal. The generated reflected RF signal is incident on each receiving antenna 21 . Each receiving antenna 21 outputs a received RF signal Rx ₁ (n _Rx , h, t) corresponding to the incident reflected RF signal to the corresponding receiver 22 . The received RF signal Rx ₁ (n _Rx , h, t) is represented by the following equation (6).

As shown in equation (6), the received RF signal Rx ₁ (n _Rx , h, t) corresponding to each receive channel is divided into N _Tx reflected RF signals Rx ₀ (n _Tx , n _Rx , h, t) is represented by the sum of The N _Tx reflected RF signals Rx ₀ (n _Tx , n _Rx , h, t) correspond to the N _Tx transmission channels, respectively. A reflected RF signal Rx ₀ (n _Tx , n _Rx , h, t) corresponding to each transmission channel is represented by Equation (7) below.

In equation (7), A _R is the amplitude of the received RF signal. R _Tx (n _Tx ,h,t) is the distance between each transmit channel and the target. R _Rx (n _Rx ,h,t) is the distance between each received channel and the target. c is the speed of light. t' is the time within one hit.

<Receiver 22>
Each receiver 22 acquires the local oscillation signal L ₁ (h, t) output by the local oscillation signal generator 11 . Also, each receiver 22 acquires the received RF signal Rx ₁ (n _Rx , h, t) output by the corresponding receiving antenna 21 .

Each receiver 22 downconverts the acquired received RF signal Rx ₁ (n _Rx ,h,t) using the acquired local oscillator signal L ₁ (h,t). Individual receivers 22 then filter the downconverted signals using bandpass filters. Each receiver 22 then amplifies the strength of the filtered signal. Individual receivers 22 then perform phase detection using the amplified signal.

By executing these processes, a reception beat signal V′ ₁ (n _Rx , h, t) corresponding to the corresponding reception channel is generated in each receiver 22 . That is, in the N _Rx receivers 22, N _Rx reception beat signals V′ ₁ (n _Rx , h, t) corresponding to the N _Rx reception channels are respectively generated. A reception beat signal V′ ₁ (n _Rx , h, t) corresponding to each reception channel is represented by the following equation (13).

In equation (13), A _V is the amplitude of the received beat signal V′ ₁ (n _Rx ,h,t). As shown in Equation (13), the received beat signal V' ₁ (n _Rx , h, t) corresponding to each received channel is obtained by combining N _Tx received beat signals V' ₀ (n _Tx , n _Rx , h, t). The N _Tx received beat signals V′ ₀ (n _Tx , n _Rx , h, t) respectively correspond to the N _Tx transmission channels. A received beat signal V′ ₀ (n _Tx , n _Rx , h, t) corresponding to each transmission channel is represented by the following equation (14).

Each receiver 22 outputs the received beat signal V′ ₁ (n _Rx , h, t) thus generated to the corresponding A/D converter 23 .

<A/D converter 23>
Each A/D converter 23 obtains the received beat signal V′ ₁ (n _Rx ,h,t) output by the corresponding receiver 22 . Each A/D converter 23 converts the obtained received beat signal V′ ₁ (n _Rx , h, t) from an analog signal to a digital signal. As a result, a received beat signal V ₁ (n _Rx , h, m) shown in the following equation (15) is generated.

The reception beat signal V ₁ (n _Rx , h, m) shown in Equation (15) corresponds to each reception channel. As shown in equation (15), the reception beat signal V ₁ (n _Rx , h, m) corresponding to each reception channel is obtained by N _Tx reception beat signals V ₀ (n _Tx , n _Rx , h, m) is represented by the sum of The N _Tx received beat signals V ₀ (n _Tx , n _Rx , h, m) respectively correspond to the N _Tx transmission channels. A received beat signal V ₀ (n _Tx , n _Rx , h, m) corresponding to each transmission channel is represented by the following equation (16).

In equation (16), Δt is the sampling interval within the modulation time _T0 . m is the sampling number of the received beat signal sampled within the modulation time _T0 . M is the number of samples of the received beat signal within the modulation time _T0 . In equation (16), terms including Δt ² and 1/c ² are approximated.

Each A/D converter 23 outputs the received beat signal V ₁ (n _Rx , h, m) thus generated to the first signal processor 3_1.

Next, detailed operation of the first signal processor 3_1 will be described. That is, detailed algorithms in each of steps ST1 to ST8 shown in FIG. 7 will be described.

<Separation unit 31 (step ST1)>
The separating unit 31 acquires the received beat signal V ₁ (n _Rx , h, m) output from each A/D converter 23 . The separating unit 31 demodulates the obtained reception beat signal V ₁ (n _Rx , h, m) using the modulation code Code ₁ (n _Tx , h) corresponding to each transmission channel. That is, the separation unit 31 demodulates the acquired reception beat signal V ₁ (n _Rx , h, m) according to the following equation (17).

As a result, demodulated received beat signals V _1,C (n _Tx , n _Rx , h, m) are generated. The received beat signals V _1,C (n _Tx ,n _Rx ,h,m) after demodulation correspond to individual transmission channels and individual reception channels. In other words, the demodulated received beat signals V _1,C ( _nTx , _nRx ,h,m) are separated into signals corresponding to individual transmission channels, and signals are separated.

However, for the received beat signals V _{1, C} (n _Tx , n _Rx , h, m) after demodulation, a signal that matches the corresponding modulation code Code ₁ (n _Tx , h), that is, the autocorrelated signal V _{0 , C} (n _Tx , n _Rx , h, m) are represented by the following equation (18). On the other hand, the received beat signals V _1,C (n _Tx ,n _Rx ,h,m) after demodulation do not match the corresponding modulation code Code ₁ (n _Tx ,h), that is, the cross-correlated signal V′ _{0, C} (n' _Tx , n _Rx , h, m) is represented by the following equation (19). Here, n' _Tx ≠n _Tx .

The separating unit 31 outputs the demodulated received beat signals V _1,C (n _Tx , n _Rx , h, m) to the signal generating unit 32 .

<Signal generator 32 (step ST2)>
The signal generator 32 acquires the demodulated received beat signals V _1,C (n _Tx , n _Rx , h, m). The signal generator 32 performs a discrete Fourier transform on the acquired received beat signal V _1,C (n _Tx , n _Rx , h, m). Specifically, for example, the signal generator 32 performs a discrete Fourier transform according to Equation (20) below.

A distance velocity signal f _b,1 (n _Tx , n _Rx , q, k) is generated by performing such a discrete Fourier transform. The range velocity signals f _b,1 (n _Tx , n _Rx , q, k) correspond to individual transmit channels and to individual receive channels. In other words, a distance velocity signal f _b,1 (n _Tx , n _Rx , q, k) is generated for each transmission channel and for each reception channel by executing the discrete Fourier transform. where q is the speed bin number. k is the distance bin number.

At this time, a discrete Fourier transform is performed for each sampling number m and for each hit number h to obtain a distance velocity signal f _b,1 (n _Tx , n _Rx , q, k) corresponding to each target candidate. ) is generated. As a result, the target candidate detection unit 34, which will be described later, can calculate a distance value corresponding to each target candidate, and can also calculate a velocity value corresponding to each target candidate.

Also, in the radar device 1, the signal to noise ratio (SNR) is improved according to 10log ₁₀ (HM). As a result, the target detection capability of the radar device 1 can be improved.

Note that the signal generator 32 may use a fast Fourier transform (FFT) instead of the discrete Fourier transform. By using the fast Fourier transform, the amount of computation in the signal generator 32 can be reduced. Also, the processing speed of the signal generator 32 can be increased. As a result, the cost of the radar device 1 can be reduced, and the processing time of the radar signal processing device 7 can be shortened.

The signal generator 32 outputs the distance velocity signal f _b,1 (n _Tx , n _Rx , q, k) thus generated to the incoherent integrator 33 .

<Incoherent Integrator 33 (Step ST3)>
The incoherent integrator 33 acquires the distance velocity signal f _b,1 (n _Tx , n _Rx , q, k) output by the signal generator 32 . The incoherent integrator 33 performs incoherent integration on the obtained distance velocity signal f _b,1 (n _Tx , n _Rx , q, k). Specifically, for example, the incoherent integrator 33 performs incoherent integration according to Equation (21) below.

By performing such incoherent integration, an incoherent integration signal f _b,1,inch (q,k) is generated. The incoherent integrator 33 outputs the generated incoherent integrated signal f _b,1,inch (q,k) to the target candidate detector 34 .

FIG. 8 shows a distance velocity signal f _b,1 (n _Tx , n _Rx , q, k) and a distance velocity signal f _b,1 (n _Tx , n _Rx , q) for each transmission channel and each reception channel. , k) and the velocity bin number corresponding to the range velocity signal f _b,1 (n _Tx , n _Rx , q, k). As shown in FIG. 8, a noise component is superimposed on the distance velocity signal f _b,1 (n _Tx , n _Rx , q, k).

In contrast, FIG. 9 shows the incoherent integrated signal f _b,1,inch (q,k), the range bin number corresponding to the incoherent integrated signal f _b,1,inch (q,k), and the incoherent FIG. 11 shows an example of velocity bin numbers corresponding to the integrated signal f _b,1,inch (q,k).

Power in a plurality of distance velocity signals f _b,1 (n _Tx , n _Rx , q, k) is integrated by performing the incoherent integration shown in Equation (21). That is, signal strengths of N _Tx ×N _Rx distance velocity signals f _b,1 (n _Tx , n _Rx , q, k) are integrated. This averages the noise components (see FIGS. 8 and 9). As a result, the target detection capability of the radar device 1 can be improved.

<Target candidate detection unit 34 (step ST4)>
The target candidate detection unit 34 acquires the incoherent integrated signal f _b,1,inch (q,k) output by the incoherent integration unit 33 . The target candidate detection unit 34 calculates a distance value corresponding to each target candidate based on the signal strength of the acquired incoherent integrated signal f _{b,1, inch} (q, k), and calculates the distance value corresponding to each target candidate. Calculate the velocity value corresponding to This allows individual target candidates to be detected. For detection of individual target candidates, for example, CA-CFAR (Cell Average Constant False Alarm Rate) processing is used. Hereinafter, the number _ntgt indicating each target candidate may be referred to as "target candidate number".

The target candidate detection unit 34 identifies the distance velocity signals f _b,1 (n _Tx , n _Rx , q _ntgt , k _ntgt ) corresponding to individual target candidates. Further, the target candidate detection unit 34 identifies the speed bin number _{q_ntgt} corresponding to each target candidate. The target candidate detection unit 34 also identifies the distance bin number _{k_ntgt} corresponding to each target candidate. The target candidate detection unit 34 detects the specified distance speed signal f _b,1 (n _Tx , n _Rx , q _ntgt , k _ntgt ), the specified speed bin number q _ntgt and the specified distance bin number k _ntgt to the coherent integrator 39 .

Here, before describing the detailed operation of the coherent integrator 39, the underlying principle and the like will be described with reference to FIGS. 10 to 13. FIG.

If a single target is located in the far field for multiple receive antennas, as shown in FIG. 10, then the target azimuth for each receive antenna can be assumed to be the same. In this case, the arrival distance difference Δr _nRx corresponding to each receiving antenna is represented by the following equation (22). Also, the target azimuth angle _{θnRx, θ0} for each receiving antenna is represented by the following equation (23).

where θ ₀ is the azimuth angle of the target with respect to the reference point. R _Rx,0 (n _Rx ) is the distance between each receive antenna and the target. R ₀ is the distance between the reference point and the target. Δr _Far,nRx,θ0 is the range-of-arrival difference corresponding to the individual receive antennas when the azimuth angle of the target relative to the reference point is _θ0 and the target is located in the far field. _dnRx is the receive antenna spacing. _dnTx is the transmit antenna spacing.

As shown in equation (23), the target azimuth angle θ _nRx, θ 0 for each receive antenna is approximated by the target azimuth angle θ ₀ for the reference point. That is, the target azimuth angle θ _nRx, θ 0 for each receive antenna is approximated by the same value.

Hereinafter, for each target candidate, the signal f _b,1 (n _Tx , n _Rx , q _ntgt , k _ntgt ) corresponding to each transmission channel and each reception channel is f _{b , 1} (n _Tx , n _Rx ).

From the equations (22) and (23), the signal f _b,1 (n _Tx , n _Rx ) is represented by the following equation (24).

For this, a discrete Fourier transform according to the following equation (25) shall be performed. It is also assumed that the condition shown in the following formula (26) is established. In this case, the azimuth angle θ ₀ that indicates the maximum power can be calculated.

where _s0 is the signal containing the phase represented by the distance difference between the reference point and the target. N _fft is the number of Fourier transform points. n _fft is the bin number after Fourier transform.

Thus, in the far field, the phase difference between the receive antennas is an integer multiple of d _Rx sin θ ₀ . Therefore, a fast Fourier transform can be performed. Thereby, coherent integration can be performed with a small amount of calculation for signals corresponding to a plurality of receiving antennas (that is, signals corresponding to all receiving antennas).

In a radar device, angular resolution can be improved by enlarging the antenna aperture. Therefore, it is conceivable to increase the antenna aperture by increasing the number of receiving antennas. However, due to the large antenna aperture, a single target may be located in the near field for multiple receive antennas, as shown in FIG. In this case, the azimuth angle of the target for each antenna will be different from each other.

In this case, the arrival distance difference Δr _nRx corresponding to each receiving antenna is represented by the following equation (27). Also, the target azimuth angle _{θnRx, θ0} for each receiving antenna is represented by the following equation (28).

As shown in Equation (28), the target azimuth angle θ _{nRx, θ0} for each receiving antenna has a different value from the target azimuth angle θ ₀ for the reference point. That is, the target azimuth angles _{θnRx, θ0} for the individual receiving antennas have different values.

Thus, in the near field, the target azimuth angles _{θnRx, θ0} for individual receiving antennas are different from each other. Therefore, it is difficult to perform a fast Fourier transform on signals corresponding to multiple receive antennas (ie, signals corresponding to all receive antennas). Therefore, the conventional radar apparatus uses the discrete Fourier transform to perform coherent integration on the signal. As a result, there is a problem that the amount of calculation increases as compared with the case of using the fast Fourier transform.

On the other hand, in the radar device 1, a plurality of integration groups are set so that each target candidate is approximated to be positioned in the far field for each integration group. Then, coherent integration (ie, first coherent integration) is performed on the signals corresponding to the individual integration groups (ie, signals within the integration group). This ensures that the first coherent integration is based on the far field, even if the individual targets are located in the near field with respect to the group of receive antennas. Therefore, the Fast Fourier Transform or Chirp Z-Transform (CZT) can be used for the first coherent integration. This is intended to reduce the amount of calculation.

FIG. 12 shows an example of multiple integration groups. FIG. 13 shows an example of one integration group out of a plurality of integration groups. In the figure, _NG indicates the number of integration groups (hereinafter referred to as "the number of integration groups"). Hereinafter, the number _nG indicating each integral group may be referred to as "integral group number". In the figure, _NRx,Far indicates the number of receiving antennas (hereinafter referred to as "the number of receiving antennas") included in each integration group. Hereinafter, the number _nRx,Far indicating each receiving antenna in each integral group is sometimes referred to as "receiving antenna number".

Here, Δr _Near,nG,θ0 is the arrival distance difference corresponding to the reception antenna corresponding to the reception antenna number n _Rx,Far =0 in each integration group, and indicates the arrival distance difference in the near field. . Also, Δr _{Far, nGNRx, Far+nRx, Far, θ0} are arrival distance differences corresponding to individual receiving antennas in individual integration groups, and indicate arrival distance differences in the far field.

In the figure, θ' indicates the azimuth angle of the target with respect to the receiving antenna corresponding to the receiving antenna number n _Rx,Far =0. θ″ indicates the target azimuth angle for the receiving antenna corresponding to the receiving antenna number n _Rx,Far =N _Rx,Far −1. Each integral group has an azimuth angle θ′ is set within a range that can be approximated to be the same value as .

That is, as shown in FIG. 12, the target is located in the near field for N _Rx,Far ×N _G receive antennas (ie, all receive antennas). In other words, the target is located in the near field for N _G integration groups. However, as shown in FIG. 13, the target is approximated to be located in the far field for each integral group.

Based on these principles and the like, the detailed operation of the coherent integrator 39 will be described below.

<Integral Unit Calculator 35 (Step ST5)>
In the integration unit calculator 35, the number of integration groups _NG and the number of receiving antennas _NRx,Far are set in advance. Alternatively, the integration unit calculator 35 calculates the number of integration groups _NG and the number of reception antennas _NRx,Far as follows.

That is, the integral unit calculator 35 calculates the aperture D _Far in each integral group based on the azimuth angle difference Δθ _Far in each integral group according to the desired angular resolution and desired integral performance. More specifically, the integration unit calculator 35 calculates the aperture D _Far that satisfies the condition shown in the following equation (29). where K _Far is a preset coefficient. D _Near is the overall aperture of the plurality of reception antennas 21 , that is, the aperture of the reception antenna group 24 .

Next, the integration unit calculator 35 calculates the number of receiving antennas N _Rx,Far by the following equation (30). Further, the integration unit calculation unit 35 calculates the number of integration groups _NG by the following equation (31). Here, floor(x) indicates the largest integer among integers smaller than the variable x.

The integration unit calculation _unit 35 _{calculates a plurality} of receive antennas 21 are grouped. Thereby, a plurality of integration groups are set.

<First integration unit 36 (step ST6)>
As shown in Equation (32) below, the signal f _b,1 (n _Tx , n _Rx ) is represented by the signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far} ). The signal f _b,1 (n _Tx , n _Rx ) is the signal corresponding to each transmit channel and to each receive channel for each target candidate. The signal f'b _,1 ( _nTx ,nG, _{nRx ,Far} ) is the signal corresponding to each transmission channel and to each integration group for each target candidate. .

That is, the signal f′ _b,1 (n _Tx ,n _G ,n _Rx,Far ) is represented by the far field within the integration group. On the other hand, the signal f′ _b,1 (n _Tx ,n _G ,n _Rx,Far ) is represented by the near field between integration groups. The signal f′ _b,1 (n _Tx ,n _G ,n _Rx,Far ) within the integration group is the signal corresponding to the individual integration group, ie, the integration group intra-group signal.

Based on such features, the first integration unit 36 performs a chirp Z transform on the in-integration-group signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far} ) for each target candidate. Specifically, for example, the first integrator 36 performs chirp Z transformation according to the following equation (33). This produces a first integration signal f _CZT (n _Tx , n _G , n _czt ) corresponding to each integration group.

where A _nG is the conversion start phase corresponding to each integration group. W _nG is the transform phase interval corresponding to each integration group. d _czt,nG is the transform distance interval corresponding to each integral group. θ _s,nG is the transform start azimuth angle corresponding to each integration group. θ _e,nG is the transformation ending azimuth angle corresponding to each integration group. _Nczt is the CZT score corresponding to each integration group. _nczt is the CZT azimuth bin number corresponding to the individual integration group.

_AnG is represented by the following equation (34). W _nG is represented by the following equation (35).

Hereinafter, the positions of the plurality of receiving antennas 21 included in each integral group may be referred to as "receiving antenna positions". FIG. 14 shows examples of receiving antenna positions corresponding to individual integration groups, transform start azimuth angles θ _s,nG corresponding to individual integration groups, and transform end azimuth angles _θe,nG corresponding to individual integration groups. ing.

As shown in FIG. 14, the transformation starting azimuth angle θ _s,nG corresponding to each integral group is the following azimuth angle. That is, the conversion start azimuth angle θ _s,nG is the azimuth when the target positioned at the conversion start azimuth angle θ _0,s with respect to the reference point is viewed from the receiving antenna 21 corresponding to the receiving antenna number n _Rx,Far =0. is a corner.

Also, the transformation end azimuth angle _θe,nG corresponding to each integral group is the following azimuth angle. That is, the transformation end azimuth angle θ _e,nG is the azimuth when the target located at the transformation end azimuth angle θ _0,e with respect to the reference point is viewed from the receiving antenna 21 corresponding to the receiving antenna number n _Rx,Far =0. is a corner.

From expression (33), when the condition shown in the following expression (36) is established, the target positioned at the azimuth angle θ ₀ with respect to the reference point is oriented with respect to the receiving antenna 21 corresponding to the receiving antenna number n _Rx,Far =0. The maximum power is shown at the angle _{θnG, θ0} .

That is, as shown in Equation (37) below, the first integrated signal f _CZT (n _Tx , n _G , n _czt ) is the same azimuth bin number n′ regardless of the receive antenna position in the corresponding integration group. Maximum power is denoted by _czt .

In such azimuth angle bin number n′ _{czt ,} the arrival distance difference Δr _Near,nG,θ0 is in phase with the phase based on That is, they are coherent. This indicates the maximum power.

If a fast Fourier transform is performed instead of the chirp Z transform shown in equation (33), then the first integrated signals corresponding to the individual integration groups are generated at different azimuth bin numbers, as shown in FIG. It indicates the maximum power. This requires a process of matching these azimuth bin numbers.

On the other hand, by executing the chirp Z transform shown in Equation (33), even if the target azimuth angle differs between the integration groups (see FIG. 14), the same azimuth bin number n′ _czt is integrated. (see FIG. 16). Therefore, the first integrated signal f _CZT (n _Tx , n _G , n _czt ) corresponding to each integration group exhibits maximum power at the same azimuth bin number n′ _czt . This eliminates the need for processing for matching the azimuth bin numbers. Therefore, the amount of calculation in the first integrating section 36 can be reduced. Also, the integration loss in the first integration section 36 can be reduced.

Also, the chirp Z-transform shown in equation (33) can be implemented using a fast Fourier transform. Thereby, the amount of calculation in the first integration section 36 can be reduced. Also, the processing time of the first integration unit 36 can be shortened.

Also, the first coherent integration can be performed in parallel for multiple integration groups. By using such parallel processing, the processing time of the first integrating section 36 can be shortened.

The first integration section 36 outputs the first integration signal f _CZT (n _Tx , n _G , _nczt ) thus generated to the second integration section 37 .

Note that the first integrating section 36 may execute a fast Fourier transform represented by the following formula (38) instead of executing the chirp Z transform represented by the formula (33). This produces a first integration signal f′ _fft (n _Tx , n _G , n _fft ) corresponding to each integration group.

From expression (38), when the condition shown in the following expression (39) is established, the target positioned at the azimuth angle θ ₀ with respect to the reference point is oriented with respect to the receiving antenna 21 corresponding to the receiving antenna number n _Rx,Far =0. The maximum power is shown at the angle _{θnG, θ0} .

By using the fast Fourier transform shown in equation (38), the amount of computation in the first integration unit 36 can be reduced compared to the case of using the discrete Fourier transform (that is, compared to the conventional radar device). . Also, the integration loss in the first integration section 36 can be reduced. However, as described above, the processing for matching the angle bin number indicating the maximum power is required (see FIG. 15).

<Second integration unit 37 (step ST7)>
The second integrator 37 acquires the first integrated signal f _CZT (n _Tx , n _G , _nczt ) output by the first integrator 36 . The second integrator 37 performs coherent integration on the acquired first integrated signal f _CZT (n _Tx , n _G , _nczt ). That is, the second integration section 37 performs the second coherent integration. This produces the second integrated signal f _DFT (n _czt ).

The second coherent integration is based on the near-field. Specifically, for example, the second integration section 37 performs coherent integration according to the following equation (40).

where _R'0 is the relative distance to each target candidate. P _nczt is the target position at the CZT azimuth bin number _nczt . P _nG is the position of the receive antenna 21 corresponding to receive antenna number n _Rx,Far =0 in each integration group.

_Pnczt is represented by the following equation (41). P _nG is represented by the following formula (42).

From equation (42), the azimuth angle θ ₀ that satisfies the condition shown in equation (43) below indicates the maximum power. The azimuth angle θ ₀ indicating the maximum power is hereinafter referred to as “θ _{0, peak} ”. Also, the azimuth bin number _nctz indicating the maximum power is described as " _nctz,peak ".

The second integration section 37 outputs the second integration signal f _DFT (n _czt ) thus generated to the angle calculation section 38 .

FIG. 17 shows an example of a plurality of first integration signals f _CZT (n _Tx , n _G , n _czt ) corresponding to a plurality of integration groups. That is, FIG. 17 shows an example of N _G first integration signals f _CZT (n _Tx , n _G , n _czt ) corresponding to N _G integration groups. Also, FIG. 17 shows an example of the second integrated signal f _DFT (n _czt ) corresponding to the N _G first integrated signals f _CZT (n _Tx , n _G , _nczt ).

As shown in FIG. 17, a second integrated signal f _DFT (n _czt ) is generated by coherent integration of a plurality of first integrated signals f _CZT (n _Tx , n _G , n _czt ). As a result, since the antenna aperture in the radar device 1 can be increased, the angular resolution of the radar device 1 can be improved. Moreover, since the power of the signal used for angle measurement (that is, the second integrated signal) can be increased, the angle measurement accuracy can be improved.

Moreover, in the radar apparatus 1, a virtual array can be formed by using a plurality of transmitting antennas 14 as well as using a plurality of receiving antennas 21 to increase the antenna aperture. This makes it possible to further increase the antenna aperture. As a result, angular resolution can be further improved.

Note that the modulation processing in the transmission RF signal corresponding to each transmission channel is not limited to code modulation (that is, code division) by the code modulation section 12 . Such modulation processing may be any one that enables separation of signals corresponding to individual transmission channels in the separating section 31 . For example, such modulation may employ time division, code division, frequency division, time division and code division, or frequency division and code division.

<Angle calculator 38 (step ST8)>
The angle calculator 38 acquires the second integrated signal f _DFT (n _czt ) output by the second integrator 37 . The angle calculator 38 uses the acquired second integrated signal f _DFT (n _czt ) to calculate angle values corresponding to individual target candidates.

Specifically, for example, the angle calculator 38 calculates the azimuth angle θ _0,peak corresponding to the corresponding azimuth angle bin number _nctz,peak for each target candidate. The azimuth angle θ _{0, peak} is calculated by the following equation (44).

Here, n _G,0 is the reception antenna number indicating the reception antenna corresponding to the reception antenna number n _RX,Far =0 in the integration group corresponding to the reference point.

As described above, the radar device 1 according to Embodiment 1 includes a plurality of antennas (14, 21) including one or more transmitting antennas 14 and a plurality of receiving antennas 21, the radar signal processing device 7, The radar signal processing device 7 includes an integral unit calculator 35 for setting a plurality of integral groups by grouping a plurality of receiving antennas 21, and each of the plurality of integral groups a first integration unit 36 for generating a plurality of first integration signals respectively corresponding to the plurality of integration groups by performing first coherent integration on the signals in the integration groups corresponding to the plurality of first integrations; a second integrator 37 that generates a second integrated signal by performing a second coherent integration on the signal; and an angle calculator 38 that uses the second integrated signal to calculate angle values corresponding to individual target candidates. , provided. Angular resolution can be improved by increasing the antenna aperture using multiple antennas (14, 21). Coherent integration for angle measurement can be facilitated by setting a plurality of integration groups. As a result, the amount of calculation can be reduced.

Further, the radar signal processing method according to Embodiment 1 includes a plurality of antennas (14, 21) including one or more transmitting antennas 14 and a plurality of receiving antennas 21, and the radar signal processing device 7. In the radar signal processing method in the radar device 1, the radar signal processing device 7 sets a plurality of integral groups by grouping a plurality of receiving antennas 21, step ST5, and the radar signal processing device 7, a step ST6 of generating a plurality of first integrated signals respectively corresponding to the plurality of integration groups by performing first coherent integration on signals within the integration groups corresponding to each of the plurality of integration groups; Step ST7 in which the processing device 7 generates second integrated signals by performing second coherent integration on the plurality of first integrated signals; and step ST7 in which the radar signal processing device 7 generates individual and a step ST8 of calculating an angle value corresponding to the target candidate. Angular resolution can be improved by increasing the antenna aperture using multiple antennas (14, 21). Coherent integration for angle measurement can be facilitated by setting a plurality of integration groups. As a result, the amount of calculation can be reduced.

Embodiment 2.
FIG. 18 is a block diagram showing a main part of a radar device according to Embodiment 2. FIG. 19 is a block diagram showing a main part of the second antenna module in the radar device according to Embodiment 2. FIG. FIG. 20 is a block diagram showing main parts of a first signal processor and a second signal processor in the radar device according to Embodiment 2. FIG. A radar device according to a second embodiment will be described with reference to FIGS. 18 to 20. FIG.

In FIG. 18, blocks similar to those shown in FIG. 1 are denoted by the same reference numerals, and descriptions thereof are omitted. Also, in FIG. 19, blocks similar to those shown in FIG. Also, in FIG. 20, the same reference numerals are given to the same blocks as those shown in FIG.

As shown in FIG. 18, the radar device 1a includes a first antenna module 2_1, a first signal processor 3_1 and a display 4. In FIG. In addition to this, the radar device 1a includes a plurality of second antenna modules 2_2. The radar device 1a also includes a plurality of second signal processors 3_2 in one-to-one correspondence with the plurality of second antenna modules 2_2. Each second signal processor 3_2 includes a second receiver 6_2. The first signal processor 3_1 and the plurality of second signal processors 3_2 constitute a main part of the radar signal processor 7a.

Note that FIG. 18 shows only one second antenna module 2_2 out of the plurality of second antenna modules 2_2. FIG. 18 shows only one second signal processor 3_2 out of the plurality of second signal processors 3_2.

As shown in FIG. 19, the second receiver 6_2 in each second antenna module 2_2 includes a local oscillation signal generator 11, a plurality of receiving antennas 21, a plurality of receivers 22, and a plurality of A/D converters. 23. A reception antenna group 24 is configured by the plurality of reception antennas 21 .

The local oscillation signal generator 11 in the second receiver 6_2 is similar to the local oscillation signal generator 11 in the transmitter 5 . The plurality of receiving antennas 21, the plurality of receivers 22, and the plurality of A/D converters 23 in the second receiving section 6_2 correspond to the plurality of receiving antennas 21, the plurality of receivers 22 in the first receiving section 6_1. and a plurality of A/D converters 23 . Therefore, detailed description is omitted.

Hereinafter, the number _NMDL of the antenna modules in the radar device 1a may be referred to as "the number of modules". Also, the number _nMDL indicating each antenna module in the radar device 1a may be referred to as a "module number".

The radar device 1a includes a plurality of antenna modules (including one first antenna module 2_1 and N _MDL -1 second antenna modules 2_2). The plurality of antenna modules may be arranged at equal intervals, or may be arranged at unequal intervals. An example in which a plurality of antenna modules are arranged at unequal intervals will be mainly described below.

Also, each antenna module includes a plurality of antennas (including N _Tx transmitting antennas 14 and N _Rx receiving antennas 21, or including N _Rx receiving antennas 21). The multiple antennas in each antenna module may be evenly spaced or unevenly spaced. An example in which a plurality of antennas in each antenna module are arranged at unequal intervals will be mainly described below.

As shown in FIG. 20, each second signal processor 3_2 includes a separator 31 and a signal generator 32 . The separator 31 and the signal generator 32 in each second signal processor 3_2 are the same as the separator 31 and the signal generator 32 in the first signal processor 3_1. Therefore, detailed description is omitted. Note that FIG. 20 shows only one second signal processor 3_2 out of the plurality of second signal processors 3_2.

As shown in FIG. 20, the first signal processor 3_1 in the radar device 1a includes a separation unit 31, a signal generation unit 32, an incoherent integration unit 33, a target candidate detection unit 34, an integration unit calculation unit 35, a first integration unit 36. , a second integrator 37 and an angle calculator 38 . In addition to this, the first signal processor 3_1 in the radar device 1a includes an arrangement equal spacing unit 51 . The integral unit calculator 35, the first integrator 36, the second integrator 37, and the equal spacing unit 51 constitute a main part of the coherent integrator 39a.

The radar device 1a includes _NMDL receiving antenna groups 24 . That is, the radar device 1a includes N _Rx ×N _MDL receiving antennas 21 . The integral unit calculator 35 sets _NMDL integral groups by grouping the _NRx × _NMDL receiving antennas 21 for each antenna module.

That is, as shown in FIG. 21, a plurality of integration groups are set in one-to-one correspondence with a plurality of antenna modules. In other words, N _G =N _MDL and n _G =n _MDL .

As described above, the plurality of antennas in each antenna module are arranged at uneven intervals. Therefore, each antenna module has a plurality of different antenna arrangement intervals _{dRx, nRx, and Far} . In other words, each integration group has a plurality of different antenna arrangement intervals d _{Rx, nRx, Far} (see FIG. 22).

The equal spacing unit 51 calculates the greatest common divisor Δd _Rx,Far in a plurality of antenna placement intervals d _Rx,nRx,Far for each integration group. Specifically, for example, the equal spacing unit 51 calculates the greatest common divisor Δd _Rx,Far by the following equation (45). Here, GCD(x) indicates the greatest common divisor in array x.

Further, based on the calculated greatest common divisor Δd _Rx,Far , the arrangement equal spacing unit 51 generates the following integration group signal f′ _b,1 (n _Tx ,n _G ,n _Rx,Far,GCD ). That is, the integration group intra-group signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ) is a signal corresponding to each transmission channel and each integration group. . In addition, the integration group internal signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ) is based on the calculated greatest common divisor Δd _{Rx, Far} , and the plurality of antennas are virtually arranged at regular intervals. FIG. 22 shows an example of such a state.

Specifically, for example, the equal spacing unit 51 generates the signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ) within the integration group according to the following equation (46). Here, _nRx,Far,GCD is the receiving antenna number in a state in which a plurality of antennas in the corresponding integral group are virtually arranged at regular intervals.

By using such an integration group intra-group signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ), when the plurality of receiving antennas 21 in each integration group are arranged at uneven intervals, , it is possible to use the Fast Fourier Transform or the Chirp Z Transform for the first coherent integration. As a result, as described in the first embodiment, it is possible to reduce the amount of calculation and shorten the processing time.

The equally spaced arrangement unit 51 outputs the integration group internal signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ) thus generated to the first integration unit 36 . .

The first integrator 36 acquires the in-integration-group signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ) output from the equal spacing unit 51 . When performing the first coherent integration, the first integration unit 36 replaces the in-integration-group signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far} ) described in the first embodiment with It is adapted to use the obtained integration group intra-group signal f′ _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ). As a result, even though the plurality of antennas included in each integration group are arranged at uneven intervals, the plurality of antennas are arranged at equal intervals in the first coherent integration. . A Fast Fourier Transform or a Chirp Z Transform is used for the first coherent integration.

A first coherent integration is performed to produce a first integrated signal f _CZT (n _Tx , n _G , n _czt ). The first integration section 36 outputs the generated first integration signal f _CZT (n _Tx , n _G , _nczt ) to the second integration section 37 .

The operation of the second integrating section 37 is the same as that described in the first embodiment. Also, the operation of the angle calculator 38 is the same as that described in the first embodiment. Therefore, detailed description is omitted.

Here, with reference to FIGS. 23 and 24, the effect of arranging a plurality of antenna modules at unequal intervals will be described. Also, the effect of arranging a plurality of antennas in each antenna module at unequal intervals will be described.

When a plurality of antenna modules are arranged at equal intervals, the grating level increases when the module arrangement interval exceeds the wavelength of radio waves (see FIG. 23). As a result, the grating level may exceed the desired level. This is the same when the antenna arrangement interval exceeds the wavelength of radio waves (see FIG. 23).

On the other hand, the grating can be made smaller by arranging a plurality of antenna modules at uneven intervals (see FIG. 24). Therefore, the total number of antenna modules (hereinafter referred to as "the total number of modules") in the radar device 1a can be reduced in suppressing the grating level to a desired level or less. Also, by arranging a plurality of antennas in each antenna module at uneven intervals, the grating can be made smaller (see FIG. 24). Therefore, in suppressing the grating level to a desired level or less, the total number of antennas in each antenna module (hereinafter referred to as "total number of antennas") can be reduced.

Hereinafter, the processes executed by the equal spacing unit 51 may be collectively referred to as "equal spacing processing". Also, the functions of the equal spacing unit 51 may be collectively referred to as "equally spaced layout function". Also, the code "F11" may be used for the equal spacing function.

The hardware configuration of the main part of the first signal processor 3_1 is the same as that described with reference to FIGS. 4 to 6 in the first embodiment. Therefore, detailed description is omitted.

That is, the first signal processor 3_1 has a plurality of functions (a separation function, a signal generation function, an incoherent integration function, a target candidate detection function, an integration unit calculation function, an arrangement equal spacing function, a first integration function, a second (including integration function and angle calculation function). Each of the plurality of functions F1-F8, F11 may be implemented by the processor 41 and memory 42, or may be implemented by the processing circuit 43. FIG. Here, the processor 41 may include a dedicated processor corresponding to each of the plurality of functions F1-F8, F11. Also, the memory 42 may include a dedicated memory corresponding to each of the plurality of functions F1 to F8, F11. Also, the processing circuit 43 may include a dedicated processing circuit corresponding to each of the plurality of functions F1 to F8, F11.

The hardware configuration of the essential part of the second signal processor 3_2 is the same as the hardware configuration of the essential part of the first signal processor 3_1. Therefore, detailed description is omitted.

That is, the second signal processor 3_2 has a plurality of functions (including separation function and signal generation function) F1 and F2. Each of the plurality of functions F1 and F2 may be implemented by the processor 41 and the memory 42, or may be implemented by the processing circuit 43 (FIGS. 25, 26 or 27). reference). Here, the processor 41 may include dedicated processors corresponding to each of the plurality of functions F1 and F2. Also, the memory 42 may include a dedicated memory corresponding to each of the plurality of functions F1 and F2. Also, the processing circuit 43 may include a dedicated processing circuit corresponding to each of the plurality of functions F1 and F2.

Next, the operation of the second signal processor 3_2 will be described with reference to the flowchart shown in FIG.

First, the separation unit 31 executes separation processing (step ST11). Next, the signal generator 32 executes signal generation processing (step ST12).

Next, the operation of the first signal processor 3_1 will be described with reference to the flowchart shown in FIG. 29, steps similar to those shown in FIG. 7 are denoted by the same reference numerals, and description thereof is omitted.

First, the processes of steps ST1 to ST5 are executed. However, in step ST5, the integral unit calculator 35 sets a plurality of integral groups in one-to-one correspondence with the plurality of antenna modules.

Next, the equal spacing unit 51 executes the equal spacing processing (step ST21).

Next, steps ST6 to ST8 are executed. However, in step ST6, the first integration unit 36 replaces the integration group signal f' _b,1 (n _Tx , n _G , n _{Rx, Far} ) with the integration group signal f' _b,1 (n _Tx , n _G , n _{Rx, Far, GCD} ).

As described above, in the radar device 1a according to Embodiment 2, the plurality of antenna modules (2_1, 2_1) are arranged at uneven intervals. As a result, the total number of modules can be reduced to achieve the desired grating level. As a result, the radar device 1a can be realized at low cost.

Also, the plurality of antennas (14, 21) are arranged at uneven intervals. As a result, the total number of antennas can be reduced to achieve the desired grating level. As a result, the radar device 1a can be realized at low cost.

In addition, the first integration unit 36 calculates the distance between the plurality of antennas (14, 21) at equal intervals based on the greatest common divisor of the plurality of arrangement intervals (antenna arrangement intervals) corresponding to the plurality of antennas (14, 21). , and the first coherent integration uses the Fast Fourier Transform. This facilitates the first coherent integration even when the plurality of antennas (14, 21) are arranged at uneven intervals. That is, it is possible to reduce the amount of calculation and shorten the processing time.

In addition, the first integration unit 36 calculates the distance between the plurality of antennas (14, 21) at equal intervals based on the greatest common divisor of the plurality of arrangement intervals (antenna arrangement intervals) corresponding to the plurality of antennas (14, 21). , and the first coherent integration uses the Chirp Z transform. This facilitates the first coherent integration even when the plurality of antennas (14, 21) are arranged at uneven intervals. That is, it is possible to reduce the amount of calculation and shorten the processing time.

In addition, within the scope of the disclosure of the present application, it is possible to freely combine each embodiment, modify any component of each embodiment, or omit any component in each embodiment. .

The radar signal processing method according to the present disclosure can be used in radar equipment. A radar device according to the present disclosure can be used, for example, in a vehicle.

1, 1a radar device, 2_1 first antenna module, 2_2 second antenna module, 3_1 first signal processor, 3_2 second signal processor, 4 display device, 5 transmitter, 6_1 first receiver, 6_2 second receiver 11 local oscillation signal generator 12 code modulator 13 transmitter 14 transmitting antenna 15 transmitting antenna group 21 receiving antenna 22 receiver 23 A/D converter 24 receiving antenna group 31 separation unit 32 signal generation unit 33 incoherent integration unit 34 target candidate detection unit 35 integration unit calculation unit 36 first integration unit 37 second integration unit 38 angle calculation unit 39 , 39a coherent integrator, 41 processor, 42 memory, 43 processing circuit, 51 equally spaced arrangement unit.

Claims (18)

A radar device comprising a plurality of antennas including one or more transmitting antennas and a plurality of receiving antennas, and a radar signal processing device,
The radar signal processing device is
an integral unit calculator that sets a plurality of integral groups by grouping the plurality of receiving antennas;
A first integrating section that generates a plurality of first integrated signals respectively corresponding to the plurality of integration groups by performing a first coherent integration on the signals within the integration groups corresponding to the plurality of integration groups. When,
a second integrator that generates a second integrated signal by performing a second coherent integration on the plurality of first integrated signals;
and an angle calculator that calculates an angle value corresponding to each target candidate using the second integrated signal. 2. The radar system according to claim 1, wherein said first coherent integration is based on far-field. 2. The radar apparatus according to claim 1, wherein said first coherent integration is such that said plurality of first integrated signals exhibit maximum power at the same angular bin number. 2. The radar system according to claim 1, wherein said first coherent integration uses a fast Fourier transform. 4. The radar system according to claim 3, wherein said first coherent integration uses chirp Z transform. 2. The radar apparatus according to claim 1, wherein each of said plurality of antennas is provided in a corresponding one of a plurality of antenna modules. 7. The radar apparatus according to claim 6, wherein said plurality of antenna modules are arranged at unequal intervals. 8. The radar apparatus according to claim 1, wherein said plurality of antennas are arranged at unequal intervals. The first integration unit performs the first coherent integration assuming that the plurality of antennas are arranged at regular intervals based on the greatest common divisor of the plurality of arrangement intervals corresponding to the plurality of antennas. and
The radar device according to claim 8, wherein the first coherent integration uses a fast Fourier transform. The first integration unit performs the first coherent integration assuming that the plurality of antennas are arranged at regular intervals based on the greatest common divisor of the plurality of arrangement intervals corresponding to the plurality of antennas. and
The radar apparatus according to claim 8, wherein the first coherent integration uses chirp Z transform. The radar signal processing device is
a signal generating unit that generates a range/velocity signal corresponding to each of the target candidates using the received signals received by the plurality of receiving antennas;
a target candidate detection unit that calculates a distance value corresponding to each of the target candidates and a velocity value corresponding to each of the target candidates using an incoherent integral signal corresponding to the distance/velocity signal. 2. The radar system according to claim 1. 12. The radar apparatus according to claim 11, wherein said radar signal processing device comprises an incoherent integration section that generates said incoherent integration signal by performing incoherent integration on said range/velocity signal. the one or more transmit antennas comprises a plurality of transmit antennas;
2. The radar apparatus according to claim 1, wherein modulation processing for separation is performed on transmission signals transmitted by each of said plurality of transmission antennas. 14. The radar apparatus according to claim 13, wherein said modulation processing uses time division, code division, frequency division, said time division and said code division, or said frequency division and said code division. 14. The radar apparatus according to claim 13, wherein said modulation processing uses a plurality of modulation codes respectively corresponding to said plurality of transmitting antennas. 2. The radar apparatus according to claim 1, wherein said plurality of antennas are provided on a vehicle. Each of the plurality of antennas is provided on the edge of the front window of the vehicle, the edge of the rear window of the vehicle, the pillar of the vehicle, the front bumper of the vehicle, or the rear bumper of the vehicle. 17. A radar system according to claim 16. A radar signal processing method in a radar device comprising a plurality of antennas including one or more transmitting antennas and a plurality of receiving antennas, and a radar signal processing device,
setting a plurality of integration groups by grouping the plurality of receiving antennas, by the radar signal processing device;
The radar signal processing device performs first coherent integration on signals within the integration groups corresponding to each of the plurality of integration groups, thereby generating a plurality of first integration signals respectively corresponding to the plurality of integration groups. a step of generating
the radar signal processor performing a second coherent integration on the plurality of first integrated signals to generate a second integrated signal;
the radar signal processing device calculating an angle value corresponding to each target candidate using the second integrated signal;
A radar signal processing method, comprising:

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