WO2019239584A1 - レーダ装置および目標距離算出方法 - Google Patents
レーダ装置および目標距離算出方法 Download PDFInfo
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- WO2019239584A1 WO2019239584A1 PCT/JP2018/022934 JP2018022934W WO2019239584A1 WO 2019239584 A1 WO2019239584 A1 WO 2019239584A1 JP 2018022934 W JP2018022934 W JP 2018022934W WO 2019239584 A1 WO2019239584 A1 WO 2019239584A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/292—Extracting wanted echo-signals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/288—Coherent receivers
- G01S7/2883—Coherent receivers using FFT processing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
- G01S13/18—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein range gates are used
Definitions
- the present invention relates to a radar apparatus that calculates a target distance.
- a transmission high-frequency signal (hereinafter referred to as a transmission RF signal) is radiated into the air, and a reflected high-frequency signal (hereinafter referred to as reflection) of the transmission RF signal reflected by the target. (Referred to as RF signal).
- a conventional radar apparatus generates a sum signal and a difference signal by setting reception gates having different gate widths with respect to the reception signal, and a ratio between the sum signal and the difference signal and a distance to a target (hereinafter referred to as a target distance). The target distance is measured using a discrete pattern indicating the relationship with
- the present invention solves the above-described problem, and an object of the present invention is to obtain a radar apparatus that can accurately measure a target distance even when a plurality of targets are present in a reception gate.
- the radar apparatus includes a transmission unit, a reception unit, a gate processing unit, a frequency domain conversion unit, and a target distance calculation unit.
- the transmission unit radiates a transmission signal to space.
- the reception unit receives a reception signal that is a signal that is transmitted and reflected by a target in space.
- the gate processing unit performs gate processing in which a plurality of reception gates are set on the reception signal, and generates a signal after gate processing.
- the frequency domain transform unit performs frequency domain transform on the gate-processed signal to generate a frequency domain signal.
- the target distance calculation unit calculates the target distance based on at least one of a real part and an imaginary part of the frequency domain signals of the plurality of reception gates generated by the frequency domain conversion unit.
- a gate process in which a plurality of reception gates are set is performed on a reception signal, a frequency domain conversion process is performed on the signal after the gate process, and a real part of a frequency domain signal of the plurality of reception gates And a target distance is calculated based on at least one of the imaginary part.
- FIG. 3 is a block diagram illustrating a configuration of a transmission unit according to Embodiment 1.
- FIG. 3 is a block diagram showing a configuration of a receiving unit in Embodiment 1.
- FIG. 4A is a block diagram showing a hardware configuration for realizing the function of the radar apparatus according to Embodiment 1.
- FIG. 4B is a block diagram illustrating a hardware configuration for executing software that implements the functions of the radar apparatus according to Embodiment 1.
- 3 is a flowchart showing an operation of the radar apparatus according to the first embodiment.
- 3 is a flowchart illustrating an operation of a transmission unit in the first embodiment.
- FIG. 3 is a flowchart illustrating an operation of a reception unit in the first embodiment.
- FIG. 8A is a diagram illustrating a waveform of a transmission RF signal.
- FIG. 8B is a diagram illustrating a waveform of a reception RF signal.
- FIG. 8C is a diagram illustrating a waveform of a received video signal.
- 3 is a flowchart showing operations of a gate processing unit and a frequency domain conversion unit in the first embodiment.
- FIG. 10A is a diagram illustrating a waveform of a received video signal.
- FIG. 10B is a diagram illustrating a waveform of a signal after gate processing of gate number 10.
- FIG. 10C is a diagram illustrating a waveform of a signal after gate processing of gate number 11.
- FIG. 10A is a diagram illustrating a waveform of a transmission RF signal.
- FIG. 8B is a diagram illustrating a waveform of a reception RF signal.
- FIG. 8C
- FIG. 10D is a diagram illustrating a waveform of a signal after gate processing of gate number 12.
- FIG. 11A is a diagram illustrating observed values of signals in a plurality of target frequency domains in the reception gate.
- FIG. 11B is a diagram illustrating a frequency-domain signal for each target in the reception gate. It is a figure which shows the amplitude of the received signal reflected by the some target in a receiving gate.
- FIG. 13A is a diagram showing a reception signal ratio of reflected signals reflected by a target in the reception gate.
- FIG. 13B is a diagram illustrating a waveform of a received video signal.
- FIG. 13C is a diagram illustrating a waveform of a signal after gate processing of gate number 10.
- FIG. 13D is a diagram illustrating a waveform of a signal after gate processing of gate number 11.
- FIG. 13E is a diagram illustrating a waveform of a signal after gate processing of gate number 12.
- FIG. 14A is a diagram showing a phase relationship of sampling numbers in the frequency domain where the signal in the frequency domain of target 1 has a maximum amplitude value.
- FIG. 14B is a diagram showing a phase relationship of sampling numbers in the frequency domain in which the signal in the frequency domain of target 2 has a maximum amplitude value.
- FIG. 15A is a diagram showing, for each target, the reception signal ratio of the reflected signal reflected by the target in the reception gate and the real part of the reflected signal reflected by the target.
- 15B is a diagram showing, for each target, the reception signal ratio of the reflected signal reflected by the target in the reception gate and the imaginary part of the reflected signal reflected by the target.
- 3 is a flowchart illustrating an operation example of a target distance calculation unit in the first embodiment.
- 10 is a flowchart illustrating another example of the operation of the target distance calculation unit according to the first embodiment. It is a figure which shows the relationship between the combination of the sampling number of the target 1, the sampling number of the target 2, and the evaluation value of a target distance candidate. It is a block diagram which shows the structure of the signal processing part of the radar apparatus which concerns on Embodiment 2 of this invention.
- FIG. 10 is a flowchart illustrating an operation example of a target distance calculation unit in the second embodiment.
- FIG. 1 is a block diagram showing a configuration of a radar apparatus 1 according to Embodiment 1 of the present invention.
- the radar apparatus 1 radiates a transmission RF signal to space, receives a reception RF signal that is a reflected RF signal reflected by the target, and calculates a distance to the target (target distance) based on the reception RF signal. It is a device to calculate.
- the radar apparatus 1 includes an antenna 2, a transmission unit 3, a transmission / reception switching unit 4, a reception unit 5, a signal processing unit 6, and a display 7.
- the signal processing unit 6 includes a gate processing unit 60, a frequency domain conversion unit 61, and a target distance calculation unit 62.
- the transmission unit 3 radiates a transmission RF signal to space via the antenna 2.
- the transmission / reception switching unit 4 switches the output of the transmission RF signal from the transmission unit 3 to the antenna 2 and the output of the reception RF signal from the antenna 2 to the reception unit 5 at the timing set by the transmission unit 3.
- the receiving unit 5 receives the received RF signal via the antenna 2.
- the signal processing unit 6 is a component that calculates the target distance based on the received RF signal, and causes the display 7 to display the calculated target distance.
- the gate processing unit 60 receives the received RF signal from the receiving unit 5, performs gate processing in which a plurality of reception gates are set on the received RF signal, and generates a signal after gate processing.
- the frequency domain transform unit 61 performs a frequency domain transform process on the signal after the gate processing by the gate processing unit 60 to generate a frequency domain signal.
- the target distance calculation unit 62 calculates the target distance based on at least one of the real part and the imaginary part of the frequency domain signals of the plurality of reception gates generated by the frequency domain conversion unit 61.
- FIG. 2 is a block diagram showing a configuration of the transmission unit 3.
- the transmission unit 3 includes a transmitter 30, a pulse modulator 31, and a local oscillator 32.
- the transmitter 30 outputs the transmission signal pulsed by the pulse modulator 31 to the antenna 2 through the transmission / reception switching unit 4.
- the pulse modulator 31 performs pulse modulation on the local oscillation signal input from the local oscillator 32 to generate a transmission RF signal.
- the local oscillator 32 generates a local oscillation signal and outputs it to the receiving unit 5 and the pulse modulator 31.
- FIG. 3 is a block diagram showing a configuration of the receiving unit 5.
- the receiving unit 5 includes a receiver 50 and an A / D converter 51.
- the receiver 50 inputs the received RF signal received by the antenna 2 through the transmission / reception switching unit 4 and outputs it to the A / D converter 51.
- the A / D converter 51 converts the received RF signal input from the receiver 50 into a digital signal and outputs the digital signal to the gate processing unit 60 included in the signal processing unit 6.
- the radar apparatus 1 includes a processing circuit for executing processes from step ST1 to step ST5 described later with reference to FIG.
- This processing circuit may be dedicated hardware, or may be a CPU (Central Processing Unit) that executes a program stored in the memory.
- CPU Central Processing Unit
- FIG. 4A is a block diagram showing a hardware configuration for realizing the functions of the radar apparatus 1.
- FIG. 4B is a block diagram illustrating a hardware configuration that executes software that implements the functions of the radar apparatus 1.
- the antenna 100 is the antenna 2 shown in FIG. 1
- the display device 101 is the display device 7 shown in FIG.
- the input / output interface 102 is an interface that relays the output of the transmission RF signal from the transmission unit 3 shown in FIG. 1 to the antenna 100 and the output of the reception RF signal from the antenna 100 to the reception unit 5 shown in FIG. is there. That is, the input / output interface 102 has the function of the transmission / reception switching unit 4 shown in FIG. Further, the input / output interface 102 also functions as an interface that relays an output signal to the display device 101.
- the external storage device 103 is a storage device that stores various setting data and signal data used for signal processing performed by the signal processing unit 6 shown in FIG.
- the external storage device 103 may be a volatile memory such as a synchronous dynamic random access memory (SDRAM), a hard disk drive device (HDD), or a solid state drive device (SSD).
- SDRAM synchronous dynamic random access memory
- HDD hard disk drive device
- SSD solid state drive device
- a program including an operating system (OS) may be stored in the external storage device 103.
- the memory 107 shown in FIG. 4B may be constructed in the external storage device 103.
- the external storage device 103 may be a storage device that is provided independently of the radar device 1 and is communicably connected to the radar device 1, for example, a storage device provided on a cloud.
- the signal path 105 is a bus through which signal data is transmitted.
- the input / output interface 102, the external storage device 103, and the processing circuit 104 are connected to each other by the signal path 105.
- the input / output interface 102, the external storage device 103, the processor 106, and the memory 107 are connected to each other by a signal path 105.
- the processing circuit 104 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, or an ASIC (Application Specific Integrated). Circuit), FPGA (Field-Programmable Gate Array), or a combination thereof.
- the functions of the transmitter 3, the receiver 5, the gate processor 60, the frequency domain converter 61, and the target distance calculator 62 in the radar apparatus 1 may be realized by separate processing circuits. It may be realized by one processing circuit.
- the processing circuit is the processor 106 shown in FIG. 4B
- the functions of the transmission unit 3, the reception unit 5, the gate processing unit 60, the frequency domain conversion unit 61, and the target distance calculation unit 62 in the radar apparatus 1 are software and firmware. Alternatively, it is realized by a combination of software and firmware.
- the software or firmware is described as a program and stored in the memory 107.
- the processor 106 reads out and executes the program stored in the memory 107, thereby functioning the transmitter 3, the receiver 5, the gate processor 60, the frequency domain converter 61, and the target distance calculator 62 in the radar device 1.
- the radar apparatus 1 includes a memory 107 for storing a program that, when executed by the processor 106, results in the processing from step ST1 to step ST5 shown in FIG. These programs cause the computer to execute the procedure or method of the transmission unit 3, the reception unit 5, the gate processing unit 60, the frequency domain conversion unit 61, and the target distance calculation unit 62.
- the memory 107 may be a computer-readable storage medium storing a program for causing a computer to function as the transmission unit 3, the reception unit 5, the gate processing unit 60, the frequency domain conversion unit 61, and the target distance calculation unit 62. .
- the memory 107 includes, for example, a non-volatile memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically-EPROM), or a volatile memory.
- a non-volatile memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically-EPROM), or a volatile memory.
- RAM Random Access Memory
- ROM Read Only Memory
- flash memory an EPROM (Erasable Programmable Read Only Memory)
- EEPROM Electrically-EPROM
- Magnetic disks, flexible disks, optical disks, compact disks, mini disks, DVDs, and the like are applicable.
- a part of the functions of the transmission unit 3, the reception unit 5, the gate processing unit 60, the frequency domain conversion unit 61, and the target distance calculation unit 62 may be realized by dedicated hardware, and a part may be realized by software or firmware.
- the transmission unit 3 and the reception unit 5 realize the functions by the processing circuit 104 that is dedicated hardware, and the processor 106 stores the gate processing unit 60, the frequency domain conversion unit 61, and the target distance calculation unit 62 in the memory 107.
- the function is realized by reading and executing the stored program.
- the processing circuit can realize the above functions by hardware, software, firmware, or a combination thereof.
- FIG. 5 is a flowchart showing the operation of the radar apparatus 1 according to the first embodiment, and shows the target distance calculation method according to the first embodiment.
- the transmission unit 3 radiates a transmission RF signal to space via the antenna 2 (step ST1).
- the receiving unit 5 receives a reception RF signal that is a reflected RF signal that is returned after the transmission RF signal is reflected by a target in space (step ST2).
- the gate processing unit 60 performs gate processing in which a plurality of reception gates are set on the reception RF signal, and generates a signal after gate processing (step ST3).
- the frequency domain transform unit 61 performs frequency domain transform on the signal after the gate processing by the gate processing unit 60 to generate a frequency domain signal (step ST4).
- the target distance calculation unit 62 calculates a target distance based on at least one of the real part and the imaginary part of the frequency domain signals of the plurality of reception gates generated by the frequency domain conversion unit 61 (step ST5).
- FIG. 6 is a flowchart showing the operation of the transmission unit 3, and shows the details of the processing in step ST1 of FIG.
- the transmitter 3 includes a transmitter 30, a pulse modulator 31, and a local oscillator 32.
- the local oscillator 32 generates a local oscillation signal L 0 (t) having a constant frequency expressed by the following formula (1) (step ST1a).
- the local oscillator 32 outputs the local oscillation signal L 0 (t) to the pulse modulator 31 and the receiving unit 5.
- t is the time
- a L is the amplitude of the local oscillation signal L 0 (t)
- f 0 is the transmission frequency.
- ⁇ 0 is the initial phase of the local oscillation signal L 0 (t)
- T obs is the observation time
- j is an imaginary unit.
- the pulse modulator 31 performs pulse modulation according to the following equation (2) on the local oscillation signal L 0 (t) using a preset pulse repetition period T pri and pulse width T 0 , and transmits a transmission RF signal.
- Tx (t) is generated (step ST2a).
- the transmission RF signal Tx (t) is output from the pulse modulator 31 to the transmitter 30 of the transmission unit 3.
- h is a hit number and H is the number of hits.
- the hit number H is expressed by the following formula (3).
- floor (X) means an integer obtained by rounding down the decimal point of the variable X.
- FIG. 8A is a diagram illustrating a waveform of the transmission RF signal Tx (t).
- FIG. 7 is a flowchart showing the operation of the receiving unit 5, and shows details of the processing in step ST2 of FIG.
- the receiving unit 5 includes a receiver 50 and an A / D converter 51.
- the reflected RF signal which is the reflected RF signal radiated from the air and reflected by the target, is incident on the antenna 2.
- the antenna 2 receives the incident reflected RF signal and outputs it to the receiver 50 as a received RF signal Rx (t) expressed by the following equation (4) (step ST1b).
- n tgt is a target number
- N tgt is a target number
- the received RF signal Rx ntgt (t) of the target number n tgt is expressed by the following equation (5).
- a R, Ntgt is the amplitude of the received RF signal Rx ntgt (t) of the target number n tgt
- R 0, ntgt is the initial target relative distance of the received RF signal Rx ntgt (t) of the target number n tgt
- v ntgt is the target relative speed of the received RF signal Rx ntgt (t) of the target number n tgt
- C is the speed of light.
- the receiver 50 down-converts the received RF signal Rx (t) input from the antenna 2 using the local oscillation signal L 0 (t) expressed by the above formula (1) (step ST2b).
- the receiver 50 passes the down-converted received RF signal Rx (t) through a bandpass filter, performs amplification and phase detection, and receives the received video signal V 0 represented by the following equation (6).
- (T) is generated and output to the A / D converter 51.
- V 0, ntgt (t) is a received video signal having a target number n tgt represented by the following equation (7)
- AV ntgt is a received video signal having a target number n tgt.
- FIG. 8B is a diagram illustrating a waveform of the reception RF signal Rx (t).
- the reception RF signal Rx (t) is a signal obtained by combining the reception RF signals reflected from the plural targets.
- FIG. 8B shows a case where the target has a target of target number 1 and a target of target number 2, and the received RF signal indicated by symbol b is reflected from the target of target number 1 indicated by symbol b1.
- This is a signal obtained by combining the received RF signal and the received RF signal reflected from the target of the target number 2 indicated by symbol b2.
- the received video signal V 0 (t) is also a signal obtained by synthesizing the received video signal derived from the received RF signal reflected from each of the plural targets.
- the received video signal indicated by reference symbol c is a signal obtained by combining the received video signal corresponding to target number 1 indicated by reference symbol c1 and the received video signal corresponding to target number 2 indicated by reference symbol c2.
- mod (X, Y) represents the remainder after the variable X is divided by the variable Y.
- the A / D converter 51 performs A / D conversion on the received video signal V 0 (t) input from the receiver 50 to generate a received video signal V (m ′) represented by the following equation (8) ( Step ST3b).
- the received video signal V (m ′) is output from the A / D converter 51 to the signal processing unit 6.
- V 0, n tgt (m ′) is a received video signal obtained by A / D converting the received video signal V 0, n tgt (t) corresponding to the target number n tgt represented by the following equation (9).
- m ′ is the sampling number
- M ′ is the number of samplings
- ⁇ t is the sampling interval of the received video signal after A / D conversion.
- the received video signal V (m ′) shown in FIG. 8C is a sampled signal.
- FIG. 9 is a flowchart showing the operations of the gate processing unit 60 and the frequency domain conversion unit 61, and shows details of the processing of step ST3 and step ST4 of FIG.
- the gate processing unit 60 is based on a preset gate slide amount ⁇ m G and a gate width for the received video signal V (m ′).
- the signal V G (n G , m ′) after gate processing is generated according to the following equation (10) (step ST1c).
- n G is a gate number.
- FIG. 10A is a diagram showing a waveform of the received video signal V (m ′).
- FIG. 10B is a diagram illustrating a waveform of the signal V G (10, m ′) after gate processing of the gate number 10.
- FIG. 10C is a diagram illustrating a waveform of the signal V G (11, m ′) after the gate processing of the gate number 11.
- FIG. 10D is a diagram illustrating a waveform of the signal V G (12, m ′) after the gate processing of the gate number 12.
- the gate processing unit 60 receives the received video signal V (m ′) of the symbol c shown in FIG. 10A, and receives the received gates G10 to G12 having gate numbers 10 to 12, for example, with respect to the received video signal V (m ′). To set the gate. As a result, a signal V G (10, m ′) after gate processing indicated by the symbol d in FIG. 10B is generated, and a signal V G (11, m ′) after gate processing indicated by the symbol e in FIG. 10C is generated. , The gate-processed signal V G (12, m ′) indicated by the symbol f in FIG. 10D is generated.
- the gated signal V G (n G , m ′) is also a signal obtained by synthesizing the gated signal derived from the received RF signal reflected from each of the plural targets.
- the signal V G (10, m ′) after gate processing indicated by reference symbol d is the target number 1 of gate number 10 indicated by reference symbol d1.
- a signal after gate processing corresponding to the target number 2 of the gate number 10 indicated by the symbol d2 are synthesized.
- the gate-processed signal V G (11, m ′) indicated by reference sign e is a gate-processed signal corresponding to target number 1 of gate number 11 indicated by reference sign e1 and gate number 11 indicated by reference sign e2.
- the signal after the gate processing corresponding to the target number 2 is a synthesized signal.
- the gate-processed signal V G (12, m ′) indicated by reference numeral f is the signal after gate processing corresponding to the target number 1 of gate number 12 indicated by reference numeral f1 and the gate number 12 indicated by reference numeral f2. This is a signal obtained by combining the gate-processed signal corresponding to the target number 2.
- the reception gate G11 is a gate that is slid by the gate slide amount ⁇ m G from the reception gate G10
- the reception gate G12 is a gate that is further slid by the gate slide amount ⁇ m G from the reception gate G11.
- the gate processing unit 60 performs narrow-band filter processing (band-pass filter processing) for allowing the signal V G (n G , m ′) after gate processing to pass a signal in the band around the center spectrum in the frequency domain.
- the gate processing unit 60 re-samples the signal V G (n G , m) after the narrow band filter processing (after the band pass filter processing) represented by the following formula (11), which is resampled as a sine wave. Is generated (step ST2c).
- m is the sampling number of the signal after the narrowband filter processing
- M is the sampling number of the signal after the narrowband filter processing.
- V G, ntgt (n G , m) is a signal after the narrow band filter processing of the gate number n G of the target number n tgt represented by the following equation (12).
- a nG, ntgt is the amplitude of the signal after the narrow band filter processing of the gate number n G of the target number n tgt .
- the gate processing unit 60 outputs the signal V G (n G , m) after the narrowband filter processing to the frequency domain conversion unit 61. Further, the gate processing unit 60 outputs the signal after the gate processing to the frequency domain conversion unit 61 even when the narrowband filter processing is not performed.
- the frequency domain transform unit 61 performs a Fourier transform process according to the following equation (13) as a frequency domain transform process on the signal V G (n G , m) after the narrowband filter process input from the gate processing unit 60.
- the frequency domain signal f d (n G , k) is generated (step ST3c).
- k is a sampling number in the frequency domain
- M fft is the number of frequency domain transform points.
- the frequency domain is represented by discrete Fourier transform, but the frequency domain transform processing may be realized by fast Fourier transform or chirp z transform.
- the frequency domain conversion unit 61 similarly performs frequency domain conversion according to the following equation (13). To generate a frequency domain signal f d (n G , k). The frequency domain converter 61 outputs the frequency domain signal f d (n G , k) to the target distance calculator 62.
- FIG. 11A is a diagram illustrating observed values of signals in a plurality of target frequency domains in the reception gate.
- a signal waveform S is a synthesized wave obtained by synthesizing the target 1 signal and the target 2 signal.
- FIG. 11B is a diagram illustrating a frequency-domain signal for each target in the reception gate.
- the signal waveform S1 is the signal waveform of the target 1
- the signal waveform S2 is the signal waveform of the target 2.
- the conventional technique described in Patent Document 1 is used. Even the target distance can be calculated. However, if the target 1 and the target 2 have the same speed, the target cannot be separated based on the Doppler frequency as shown in FIG. 11A. For this reason, when there are a plurality of target numbers at the same speed, it becomes difficult to calculate the target distance due to interference of a plurality of signals. That is, as shown in FIG. 11B, when there are reflected RF signals from a plurality of targets having the same speed in the reception gate, the discrepancy pattern is different from the case where the number of targets is one. It becomes difficult to calculate.
- FIG. 12 is a diagram illustrating the amplitude of the received RF signal reflected by a plurality of targets in the reception gate.
- the amplitude and phase of the signals observed at each of the gate number n G by a difference of a plurality of targets of amplitude and phase (composite wave) are different, it is difficult to calculate the respective target distance become.
- m G (n G ) is a sampling number m ′ corresponding to the gate start bin of the gate number n G.
- the target distance calculation unit 62 in the first embodiment has the same speed as the target and there are reflected RF signals from a plurality of targets that cannot be separated based on the Doppler frequency in the reception gate, A target distance for each of the plurality of targets can be calculated.
- the target number N tgt is 2 will be described as an example.
- the frequency domain signal f d (n G , k) is given by This is a composite wave of the frequency domain signals f d, ntgt (n G , k) of a plurality of target numbers n tgt represented by (14).
- the signal f d, ntgt (n G , k) in the frequency domain of the target number n tgt at the gate number n G is expressed by the following equation (15). From the following equation (15), when the relationship of the following equation (16) is satisfied, the signal f d, ntgt (n G , k) in the frequency domain of the target number n tgt at the gate number n G indicates the maximum amplitude value. .
- the frequency domain signal f d, ntgt (n G , k) of the target number n tgt for the gate number n G is the frequency domain sampling number k indicating the maximum amplitude value, and the frequency domain sampling It is represented by the number k peak .
- the frequency domain signal f d, ntgt (n G , k peak ) of the target number n tgt of the sampling number k peak of the frequency domain indicating the maximum amplitude value can be developed as in the following equation (17).
- x (m G (n G ), m ntgt ) is a ratio (reception signal ratio) that the reflected RF signal from the target of the target number n tgt is present in the reception gate of the gate number n G.
- M p is the number of sampling points of the pulse
- a ntgt is the amplitude when all the reflected RF signals of the target number n tgt are present in the reception gate.
- m Ntgt is the sampling number of the initial relative distance of the target number n tgt R 0, ntgt the incoming video signal V (m '), ⁇ ntgt is an initial relative distance R 0, Ntgt phase of the target number n tgt ,
- is the absolute value of the variable X.
- the sampling number m ntgt of the received video signal V (m ′) of the initial relative distance R 0, ntgt of the target number n tgt is expressed by the following equation (18). Note that the sampling number m ntgt does not have to be an integer as shown in the following formula (18), and may have a value after the decimal point.
- FIG. 13A is a diagram showing a reception signal ratio of a reflected RF signal reflected by a target in the reception gate.
- FIG. 13B is a diagram illustrating a waveform of a received video signal.
- FIG. 13C is a diagram illustrating a waveform of a signal after gate processing of gate number 10.
- FIG. 13D is a diagram illustrating a waveform of a signal after gate processing of gate number 11.
- FIG. 13E is a diagram illustrating a waveform of a signal after gate processing of gate number 12. Since the gate processing unit 60 is provided with a plurality of reception gates, as shown in FIG. 13A, from the above equation (17), the ratio of the reflected RF signal from each target (reception signal ratio) x ( m G (n G ), m ntgt ) is different for each reception gate.
- the passage start of the reception gate with the gate number 12 starts from the sampling number 12.
- the frequency domain transform unit 61 starts the frequency domain transform process from the same time (same sampling number) regardless of the position of each reception gate, as shown in the above equation (13). Therefore, it is possible to perform control such that the phase of the sampling number k peak in the frequency domain indicating the maximum amplitude value of the signal after frequency domain conversion of each target does not change. That is, the phase ⁇ ntgt of the initial relative distance R 0, ntgt of the target number n tgt is shown regardless of the gate number n G. As a result, since the unknowns are reduced, it is possible to obtain a radar apparatus that can calculate a plurality of target distances with a small number of calculations.
- the real part z ⁇ (n G ) and imaginary part z ⁇ of the signal f d (n G , k peak ) in the frequency domain of the sampling number k peak in the frequency domain of the gate number n G (N G ) is observed.
- ⁇ 1 is the real part of the signal in the frequency domain of target 1 that has the maximum amplitude value.
- ⁇ 1 is the imaginary part of the signal in the frequency domain of target 1 that has the maximum amplitude value.
- ⁇ 2 is the real part of the signal in the frequency region of target 2 that is the maximum amplitude value.
- ⁇ 2 is the imaginary part of the signal in the frequency domain of target 2 that is the maximum amplitude value.
- ⁇ ′ 1 is the real part of the signal in the frequency domain of target 1 when target 1 is present in the reception gate of gate number n ′ G indicating the maximum amplitude
- ⁇ ′ 1 is the target 1 is an imaginary part of the signal in the frequency domain of the target 1 when present in the receiving gate of the gate number n 'G showing the amplitude maximum value
- ⁇ ′ 2 is the real part of the signal in the frequency domain of the target 2 when the target 1 exists in the reception gate of the gate number n ′ G indicating the maximum amplitude
- ⁇ ′ 2 is the maximum amplitude of the target 1 an imaginary part of the signal in the frequency domain of the target 2 when present in gate number n 'in the receiving gate of G shown.
- ⁇ ′′ 1 is the real part of the signal in the frequency domain of target 1 when target 2 is present in the receiving gate of gate number n ′′ G indicating the maximum amplitude
- ⁇ ′′ 1 is the target 2 is the imaginary part of the signal in the frequency domain of the target 1 when it exists in the reception gate of the gate number n ′′ G indicating the maximum amplitude value.
- ⁇ ′′ 2 is the real part of the signal in the frequency domain of the target 2 when the target 2 exists in the reception gate of the gate number n ′′ G indicating the maximum amplitude
- ⁇ ′′ 2 is the maximum amplitude of the target 2 This is the imaginary part of the signal in the frequency domain of the target 2 when it exists in the reception gate of the gate number n ′′ G indicating the value.
- gate number n "G gate number n 'G and the target second target 1 indicates the amplitude maximum value indicates a maximum amplitude value may be a real number.
- gate number n Regardless of G without changing the phase ⁇ ntgt of each target, only the ratio at which the reflected RF signal from each target is present in the receiving gate is changed based on the gate number n G.
- FIG. 15A is a diagram showing, for each target, the reception signal ratio of the reflected RF signal reflected by the target in the reception gate and the real part of the reflected RF signal reflected by the target.
- C3 is the real part of the observed value of the reflected RF signal from the target present in the receiving gate of the gate number n G.
- FIG. 15B is a diagram showing, for each target, the reception signal ratio of the reflected RF signal reflected by the target in the reception gate and the imaginary part of the reflected RF signal reflected by the target.
- D3 is the imaginary part of the observed value of the reflected RF signal from the target present in the receiving gate of the gate number n G.
- the gate processing is performed so that only the real part and the imaginary part of the reflected RF signal (received RF signal) are changed.
- the target distance calculation unit 62 can calculate each target distance even when a plurality of targets having different target distances that cannot be separated from each other at the Doppler frequency exist in the reception gate. It is.
- FIG. 16 is a flowchart showing an operation example of the target distance calculation unit 62 in the first embodiment, and shows details of the processing in step ST5 of FIG.
- FIG. 17 is a flowchart showing another example of the operation of the target distance calculation unit 62 in the first embodiment.
- the real part z ⁇ (n G ) and the imaginary part z ⁇ (n G ) of the reflected RF signal existing in the reception gate of the observed gate number n G are expressed by the following formula (19) and the following formula (20). Is done.
- the sampling number of the target 1 to be assumed is calculated using the following equation (21).
- M ′ 1 the sampling number of the target 2 to be assumed is m ′ 2
- a simultaneous equation is derived, and the simultaneous equations are solved according to the following equation (22), whereby the sampling number m ′ 1 of the target 1 and the target 2
- the real part ⁇ ′ 1, m′1, m′2 of the reflected RF signal from the target of the target number n tgt 1 when the sampling number is m ′ 2 and the sampling numbers m ′ 1 and 2 of the target 1
- the imaginary part ⁇ ′ 2, m′1, and m′2 of the reflected RF signal from are calculated. The process so far is step ST1d.
- m st is a combination of a plurality of target distance assumed (hereinafter referred to as the target distance candidate) is a target sampling starting number of, Delta] m, the interval of the sampling number of the target envisaged, m ed is assumed N G, 1 is a gate number of a preset number 1 and n G, 2 is a gate number of a preset number 2.
- the real part and imaginary part of the signal in the frequency domain within the plurality of reception gates the real part and imaginary part of the signal used for calculating the target distance may be selected based on the signal strength of the signal.
- the target distance calculation unit 62 when using the observed value of a number of received gate than the target number N tgt when calculating the target distance, according to the following equation (24), the sampling number of the target 1 to assume m '1 and then, it derives the simultaneous equations sampling number of the target 2 as m '2.
- the following formula (24) shows a case where all the reception gates are used, but it is sufficient that there are more reception values of reception gates than the target number N tgt .
- the target distance calculation unit 62 performs partial differentiation on the simultaneous equations represented by the following expression (24) by the reception signal ratio x (m G (n G ), m ntgt ), and the target distance candidate is determined according to the following expression (25). An evaluation value is calculated. Subsequently, the target distance calculation unit 62 defines the following formula (25) as the following formula (26).
- the matrix X m′1, m′2 related to the signal ratio, the matrix A m′1, m′2 related to the real part and the imaginary part of the target signal, and the matrix Z m′1, m′2 related to the observed value are as follows : It is represented by equation (27).
- the target distance calculation unit 62 solves the above equation (26) by the least square method according to the following equation (28), thereby obtaining a matrix A m′1 related to the real part and the imaginary part of the reflected RF signal from the target.
- M′2 is calculated (step ST1e).
- Y ⁇ 1 represents an inverse matrix of the matrix Y.
- the target distance calculation unit 62 performs real part ⁇ ′ ntgt, m′1, m′2 of each combination of the sampling number m ′ 1 of the target 1 and the sampling number m ′ 2 of the target 2 according to the following equation (29). And the imaginary part ⁇ ′ ntgt, m′1, m′2 and the real part z ⁇ (n G ) and the imaginary part z ⁇ (n G ) of the observed value, that is, the real part residual ⁇ ⁇ (M ′ 1 , m ′ 2 ) and imaginary part residual ⁇ ⁇ (m ′ 1 , m ′ 2 ) are calculated.
- FIG. 18 is a diagram illustrating the relationship between the combination of the sampling number of the target 1 and the sampling number of the target 2 and the evaluation value of the target distance candidate.
- the vertical axis is the sampling number m ′ 1 for target 1
- the horizontal axis is the sampling number m ′ 2 for target 2.
- the target distance calculation unit 62 uses the real part residual ⁇ ⁇ (m ′ 1 , m ′ 2 ) and the imaginary part residual ⁇ ⁇ (m ′ 1 , m ′ 2 ).
- the evaluation value ⁇ (m ′ 1 , m ′ 2 ) is calculated according to the following formula (30).
- the target distance calculation unit 62 calculates the sampling number m ′′ 1 of target 1 and the sampling number m ′′ 2 of target 2 that maximize the evaluation value ⁇ (m ′ 1 , m ′ 2 ) according to the following equation (31). To do.
- argmax ⁇ (p, q) is a function for calculating arguments p and q that maximize the evaluation value ⁇ (p, q) of the target distance candidate.
- the target distance calculation unit 62 calculates the target distance R ′′ 0, ntgt of the target number n tgt using the following equation (32) (step ST2d, step ST2e).
- the target distance calculation unit 62 can calculate a plurality of target distances even if only the real part or the imaginary part is used. Further, the target distance calculation unit 62 can calculate the target distance even if the target number is one. When the target number is 1, it may be calculated as m ′ 1 only.
- the target distance calculation unit 62 outputs the target distance R ′′ 0, ntgt of the target number n tgt to the display unit 7.
- the display unit 7 outputs the target distance R ′′ 0 of the target number n tgt input from the target distance calculation unit 62. , Ntgt are displayed on the screen as target information.
- the radar apparatus 1 performs gate processing in which a plurality of reception gates are set on the received RF signal, performs frequency domain conversion processing on the signal after gate processing, and performs multiple processing.
- the target distance is calculated based on at least one of the real part and the imaginary part of the signal in the frequency domain of the receiving gate.
- the gate processing unit 60 sets a plurality of reception gates, generates a signal after narrowband filtering so that signals in a target frequency domain existing in each reception gate have the same phase, and performs frequency domain conversion.
- the unit 61 performs frequency domain conversion on the signal existing in each reception gate from the same sampling number to generate a frequency domain signal.
- the gate processor 60 regardless of the gate number n G, for performing gated such that only the real part and the imaginary part of each of the target is changed, the target distance calculation unit 62, by utilizing this characteristic, assuming The target distance is calculated based on at least one of the received signal ratio and the observed and real part and imaginary part even if there are reflected signals from multiple targets in the receiving gate at the same speed can do.
- the target distance calculation unit 62 uses at least one of the real part and the imaginary part of the signals in the frequency domain of the plurality of reception gates, and uses the target in each reception gate.
- the target distance candidate simultaneous equation based on the ratio of received signals from is solved to calculate an evaluation value of the target distance candidate, and the target distance is calculated based on the evaluation value of the target distance candidate.
- the evaluation value it is possible to calculate a plurality of target distances with a small amount of calculation.
- the target distance calculation unit 62 uses at least one of the real part and the imaginary part of the signals in the frequency domain of the plurality of reception gates, and the target in each reception gate.
- a target distance candidate simultaneous equation is derived based on the ratio of received signals from, and the target distance candidate evaluation value is calculated by solving the derived simultaneous equation using the least squares method. Based on this, the target distance is calculated. Since the evaluation value is calculated using the least square method, the influence of noise is further reduced, and the ranging accuracy is improved.
- the target number N tgt is set to 2, but even if it is a natural number other than 2, it is possible to calculate the target distance for the target number similarly.
- FIG. FIG. 19 is a block diagram showing the configuration of the signal processing unit 6A of the radar apparatus according to Embodiment 2 of the present invention.
- the radar apparatus according to the second embodiment includes an antenna 2, a transmission unit 3, a transmission / reception switching unit 4, a reception unit 5, and a display 7, as in FIG.
- a signal processing unit 6A is provided instead of the signal processing unit 6.
- the signal processing unit 6A includes a gate processing unit 60, a frequency domain conversion unit 61, a target distance calculation unit 62A, and a target candidate detection unit 63.
- the target distance calculation unit 62A calculates the target distance based on at least one of the real part and the imaginary part of the signal in the frequency domain of the target candidate detected by the target candidate detection unit 63.
- the target candidate detection unit 63 detects a target candidate based on the signal strength of the frequency domain signal generated by the frequency domain conversion unit 61.
- the frequency domain transform unit 61 outputs the frequency domain signal f d (n G , k) to the target candidate detection unit 63.
- the target candidate detection unit 63 detects a target candidate based on the signal strength of the signal f d (n G , k) in the frequency domain. For example, the target candidate detection unit 63 detects a target candidate by CA-CFAR (Cell Average Constant False Alarm Rate) processing.
- CA-CFAR Cell Average Constant False Alarm Rate
- FIG. 20 is a diagram illustrating the relationship between the amplitude of the reflected RF signal from the target in the reception gate, the amplitude of the reflected RF signal from the target candidate, and noise.
- E1 is the amplitude of the reflected RF signal from the target present in the receiving gate of the gate number n G.
- z ⁇ (n G ) is the real part of the reflected RF signal of gate number n G
- z ⁇ (n G ) is the imaginary part.
- E3 is noise.
- the target candidate detection unit 63 receives the frequency domain signal f d (n G , k) input from the frequency domain conversion unit 61 and the gate number n G, tgt of the reception gate where the target candidate n tgt detected by the CFAR processing is present. And the sampling number k in the frequency domain are output to the target distance calculation unit 62A.
- FIG. 21 is a flowchart illustrating an operation example of the target distance calculation unit 62A in the second embodiment.
- the range of the target number to be assumed is 1 to N ′ tgt .
- the target distance calculation unit 62A sets the target number n ′ tgt within the range of the assumed target number (step ST1f).
- the target distance calculation unit 62A derives simultaneous equations according to the following equation (33) according to the assumed target number n ′ tgt .
- m G (n G, tgt ) is a sampling number m ′ corresponding to the gate start bin of the gate number n G, tgt of the target candidate n tgt .
- the target distance calculation unit 62A uses the simultaneous equations expressed by the above equation (33) as a ratio (reception signal ratio) x (m G (n G ) that the reflected RF signal from each target exists in the reception gate. , Tgt ), mn'tgt ), and is expressed by the following formula (34). Next, the target distance calculation unit 62A defines the following formula (34) as the following formula (35).
- the matrices Z m′1,..., M′n′tgt are represented by the following formula (36).
- the target distance calculation unit 62A solves the above equation (36) by the least square method according to the following equation (37) , whereby the matrix A m′1,..., M′n′tgt related to the real and imaginary parts of the target signal. Is calculated (step ST2f).
- Y ⁇ 1 is an inverse matrix of the matrix Y
- Y T represents the transpose of the matrix Y.
- the target distance calculation unit 62A follows the following formula (38), and the real part ⁇ ′ n′tgt, m′1,... Of the combination of the sampling numbers m n′tgt of each target when the target number is n ′ tgt .
- the target distance calculation unit 62A includes a real part residual ⁇ ⁇ (m ′ 1 ,..., M ′ n′tgt ) and an imaginary part residual ⁇ ⁇ (m ′ 1 ,..., M ′ n ′.
- the target distance candidate evaluation value ⁇ (m ′ 1 , m ′ 2 ) is calculated according to the following formula (39) using tgt ).
- Target distance calculation unit 62A in accordance with the following equation (40), the evaluation value ⁇ of the target distance candidate (m '1, ⁇ , m 'n'tgt) to maximize the target number N "tgt, each The target sampling number mn'tgt is calculated, where argmax ⁇ (q, p, ..., q) maximizes the evaluation value ⁇ (q, p, ..., q) of the target distance candidate. This is a function for calculating a variable q and arguments p,.
- the target distance calculation unit 62A calculates the target distance R ′′ 0, ntgt of the target number n tgt according to the following formula (41) (step ST3f).
- the amount of information is increased and the ranging accuracy is improved, and the target distances of a plurality of targets can be calculated using only one of the real part and the imaginary part.
- the target distance calculation unit 62A derives the simultaneous equations expressed by the above equation (33) according to the target number, and further solves the simultaneous equations by the least square method according to the above equation (37), thereby , M′n′tgt related to the imaginary part and the imaginary part are calculated, and the evaluation value ⁇ (m ′ 1 ,..., M ′ n′tgt of the target distance candidate is calculated according to the above equation (40). ) To obtain the maximum target number N ′′ tgt and each target sampling number mn′tgt . Therefore, even if the target number is set in advance, the relative distance corresponding to the target number is calculated. Can be calculated.
- the radar apparatus detects the target candidate based on the signal strength of the frequency domain signal f d (n G , k) generated by the frequency domain transform unit 61.
- a portion 63 is provided.
- the target distance calculation unit 62A calculates the target distance based on at least one of the real part and the imaginary part of the frequency domain signal f d (n G , k) of the target candidate detected by the target candidate detection unit 63. . That is, since the target distance candidate is calculated based on the observation value of the signal in the target candidate reception gate, it is not necessary to set the reception gate in advance.
- the target candidate detection unit 63 since the target candidate is detected based on the signal strength, the target distance is calculated in a situation where the signal-to-noise ratio is high. Thereby, the target distance can be calculated with high accuracy.
- the target candidate detection unit 63 further selects a target candidate based on the signal strength, so that the target distance can be calculated with higher accuracy.
- the radar apparatus according to the present invention can accurately measure the target distance even when there are a plurality of targets in the reception gate, it can be used for various radar apparatuses.
- 1 radar device 2,100 antenna, 3, transmission unit, 4 transmission / reception switching unit, 5 reception unit, 6, 6A signal processing unit, 7, 101 display, 30 transmitter, 31 pulse modulator, 32 local oscillator, 50 reception Machine, 51 A / D converter, 60 gate processing unit, 61 frequency domain conversion unit, 62, 62A target distance calculation unit, 63 target candidate detection unit, 102 input / output interface, 103 external storage device, 104 processing circuit, 105 signal Road, 106 processor, 107 memory.
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Abstract
Description
実施の形態1.
図1は、本発明の実施の形態1に係るレーダ装置1の構成を示すブロック図である。
レーダ装置1は、送信RF信号を空間に放射し、送信RF信号が目標で反射された反射RF信号である受信RF信号を受信し、受信RF信号に基づいて目標までの距離(目標距離)を算出する装置である。図1に示すように、レーダ装置1は、空中線2、送信部3、送受切替部4、受信部5、信号処理部6および表示器7を備える。信号処理部6は、ゲート処理部60、周波数領域変換部61および目標距離算出部62を備える。
レーダ装置1における、送信部3、受信部5、ゲート処理部60、周波数領域変換部61および目標距離算出部62の機能は、処理回路によって実現される。
すなわち、レーダ装置1は、図5を用いて後述するステップST1からステップST5までの処理を実行するための処理回路を備える。この処理回路は、専用のハードウェアであってもよいが、メモリに記憶されたプログラムを実行するCPU(Central Processing Unit)であってもよい。
レーダ装置1における、送信部3、受信部5、ゲート処理部60、周波数領域変換部61および目標距離算出部62の機能を別々の処理回路で実現してもよく、これらの機能をまとめて1つの処理回路で実現してもよい。
図5は、実施の形態1に係るレーダ装置1の動作を示すフローチャートであり、実施の形態1に係る目標距離算出方法を示している。
送信部3が、空中線2を介して送信RF信号を空間に放射する(ステップST1)。
受信部5が、送信RF信号が空間内の目標で反射されて戻ってきた反射RF信号である受信RF信号を受信する(ステップST2)。
ゲート処理部60が、受信RF信号に対して複数の受信ゲートを設定したゲート処理を行い、ゲート処理後の信号を生成する(ステップST3)。
周波数領域変換部61が、ゲート処理部60によるゲート処理後の信号に対して周波数領域変換を行い、周波数領域の信号を生成する(ステップST4)。
目標距離算出部62が、周波数領域変換部61によって生成された複数の受信ゲートの周波数領域の信号の実部および虚部のうちの少なくとも一方に基づいて、目標距離を算出する(ステップST5)。
図6は、送信部3の動作を示すフローチャートであり、図5のステップST1の処理の詳細を示している。送信部3は、図2に示したように、送信機30、パルス変調器31、および局部発振器32を備えている。
図8Aは、送信RF信号Tx(t)の波形を示す図である。図8Aに示すように、送信RF信号Tx(t)は、予め設定されたパルス繰り返し周期Tpriおよびパルス幅a(=T0)の信号である。
図7は、受信部5の動作を示すフローチャートであり、図5のステップST2の処理の詳細を示している。受信部5は、図3に示したように、受信機50およびA/D変換器51を備えている。
下記式(4)において、ntgtは目標番号、Ntgtは目標数である。目標番号ntgtの受信RF信号Rxntgt(t)は、下記式(5)で表される。AR,ntgtは目標番号ntgtの受信RF信号Rxntgt(t)の振幅であり、R0,ntgtは目標番号ntgtの受信RF信号Rxntgt(t)の初期目標相対距離であり、vntgtは目標番号ntgtの受信RF信号Rxntgt(t)の目標相対速度である。また、cは光速である。
次に、受信機50は、ダウンコンバートした受信RF信号Rx(t)を、帯域フィルタを通過させた後、増幅および位相検波を行って、下記式(6)で表される受信ビデオ信号V0(t)を生成してA/D変換器51に出力する。下記式(6)において、V0,ntgt(t)は、下記式(7)で表される目標番号ntgtの受信ビデオ信号であり、AV,ntgtは、目標番号ntgtの受信ビデオ信号V0,ntgt(t)の振幅である。
図8Bは、受信RF信号Rx(t)の波形を示す図である。目標数が複数である場合、受信RF信号Rx(t)は、複数の目標のそれぞれから反射された受信RF信号が合成された信号となる。例えば、図8Bでは、目標が、目標番号1の目標と目標番号2の目標がある場合を示しており、符号bで示す受信RF信号は、符号b1で示す目標番号1の目標から反射された受信RF信号と符号b2で示す目標番号2の目標から反射された受信RF信号とが合成された信号である。
図8Cは、受信ビデオ信号V0(t)の波形を示す図である。目標数が複数であると、受信ビデオ信号V0(t)も、複数の目標のそれぞれから反射された受信RF信号に由来する受信ビデオ信号が合成された信号となる。例えば、図8Cでは、符号cで示す受信ビデオ信号は、符号c1で示す目標番号1に対応する受信ビデオ信号と符号c2で示す目標番号2に対応する受信ビデオ信号とが合成された信号である。ただし、図8A、図8B、図8Cにおいて、mod(X,Y)は、変数Xを変数Yで割った後の剰余を表している。
V0,ntgt(m’)は、下記式(9)で表される目標番号ntgtに対応する受信ビデオ信号V0,ntgt(t)がA/D変換された受信ビデオ信号である。m’はサンプリング番号、M’はサンプリング数であり、Δtは、A/D変換された受信ビデオ信号のサンプリング間隔である。図8Cに示す受信ビデオ信号V(m’)は、サンプリングされた信号となる。
図9は、ゲート処理部60および周波数領域変換部61の動作を示すフローチャートであり、図5のステップST3およびステップST4の処理の詳細を示している。
ゲート処理部60は、A/D変換器51から受信ビデオ信号V(m’)を入力すると、受信ビデオ信号V(m’)に対し、予め設定されたゲートスライド量ΔmGおよびゲート幅に基づいて、下記式(10)に従いゲート処理後の信号VG(nG,m’)を生成する(ステップST1c)。nGはゲート番号である。
なお、ゲート処理部60は、ゲート幅をパルス幅とみなしてゲート処理を行っている。ただし、ゲートの位置およびゲート幅は、任意に設定された値であってもよい。
図10Aは、受信ビデオ信号V(m’)の波形を示す図である。図10Bは、ゲート番号10のゲート処理後の信号VG(10,m’)の波形を示す図である。図10Cは、ゲート番号11のゲート処理後の信号VG(11,m’)の波形を示す図である。図10Dは、ゲート番号12のゲート処理後の信号VG(12,m’)の波形を示す図である。
ゲート処理部60は、図10Aに示す符号cの受信ビデオ信号V(m’)を入力して、受信ビデオ信号V(m’)に対して、例えばゲート番号10~12の受信ゲートG10~G12を設定してゲート処理を行う。これにより、図10Bの符号dで示すゲート処理後の信号VG(10,m’)が生成され、図10Cの符号eで示すゲート処理後の信号VG(11,m’)が生成され、図10Dの符号fで示すゲート処理後の信号VG(12,m’)が生成される。目標数が複数であると、ゲート処理後の信号VG(nG,m’)も複数の目標のそれぞれから反射された受信RF信号に由来するゲート処理後の信号が合成された信号となる。例えば、目標が、目標番号1の目標と目標番号2の目標がある場合、符号dで示すゲート処理後の信号VG(10,m’)は、符号d1で示すゲート番号10の目標番号1に対応するゲート処理後の信号と、符号d2で示すゲート番号10の目標番号2に対応するゲート処理後の信号とが合成された信号である。同様に、符号eで示すゲート処理後の信号VG(11,m’)は、符号e1で示すゲート番号11の目標番号1に対応するゲート処理後の信号と、符号e2で示すゲート番号11の目標番号2に対応するゲート処理後の信号とが合成された信号である。さらに、符号fで示すゲート処理後の信号VG(12,m’)は、符号f1で示すゲート番号12の目標番号1に対応するゲート処理後の信号と、符号f2で示すゲート番号12の目標番号2に対応するゲート処理後の信号とが合成された信号である。
また、受信ゲートG11は、受信ゲートG10からゲートスライド量ΔmGスライドされたゲートであり、受信ゲートG12は、受信ゲートG11から、さらにゲートスライド量ΔmGスライドされたゲートである。
なお、下記式(11)において、mは、狭帯域フィルタ処理後の信号のサンプリング番号であり、Mは狭帯域フィルタ処理後の信号のサンプリング数である。
VG,ntgt(nG,m)は、下記式(12)で表される目標番号ntgtのゲート番号nGの狭帯域フィルタ処理後の信号である。AnG,ntgtは、目標番号ntgtのゲート番号nGの狭帯域フィルタ処理後の信号の振幅である。
狭帯域フィルタ処理を行うことで、周波数領域の中心スペクトルの情報を損なわずに、サンプリング間隔が粗いリサンプリングが可能となる。これにより、信号点数を減らしてもよくなって演算量が低減されるので、ハードウェア規模を小さくしたレーダ装置1を実現することができる。
周波数領域変換部61は、ゲート処理部60から入力した狭帯域フィルタ処理後の信号VG(nG,m)に対して、下記式(13)に従うフーリエ変換処理を、周波数領域変換処理として行い、周波数領域の信号fd(nG,k)を生成する(ステップST3c)。ここで、kは、周波数領域のサンプリング番号であり、Mfftは、周波数領域変換点数である。下記式(13)では、周波数領域を離散フーリエ変換で表しているが、高速フーリエ変換またはチャープz変換で周波数領域変換処理を実現してもよい。
また、周波数領域変換部61は、ゲート処理部60から入力した信号が、狭帯域フィルタ処理が行われなかったゲート処理後の信号である場合も、同様に下記式(13)に従い周波数領域変換を行って、周波数領域の信号fd(nG,k)を生成する。
周波数領域変換部61は、周波数領域の信号fd(nG,k)を目標距離算出部62に出力する。
図11Aは、受信ゲート内にある複数の目標の周波数領域の信号の観測値を示す図である。図11Aにおいて、信号波形Sは、目標1の信号と目標2の信号が合成された合成波である。図11Bは、受信ゲート内にある目標ごとの周波数領域の信号を示す図である。図11Bにおいて、信号波形S1は目標1の信号波形であり、信号波形S2は目標2の信号波形である。目標数が1つである場合、あるいは、目標数が複数であっても速度が異なるか、距離がパルス幅以上で十分に異なる場合であれば、特許文献1に記載された従来の技術であっても目標距離を算出することができる。ただし、目標1と目標2とが同じ速度であると、図11Aに示すように、ドップラー周波数に基づいて目標を分離することができなくなる。このため、同じ速度の目標数が複数である場合、複数の信号が干渉して目標距離を算出することが困難になる。すなわち、図11Bに示すように、受信ゲート内に、同じ速度の複数の目標からの反射RF信号が存在する場合、目標数が1つである場合とはディスクリパターンが異なるため、目標距離を算出することが困難になる。
また、振幅A3は、ゲート番号nGの反射RF信号(受信RF信号)の観測値の振幅であり、A3=(zα(nG)2+zβ(nG)2)1/2である。zα(nG)はゲート番号nGの反射RF信号の実部であり、zβ(nG)は虚部である。
図12に示すように、複数の目標の振幅および位相の差によって各々のゲート番号nGで観測される信号(合成波)の振幅および位相が異なるため、各々の目標距離を算出することが困難になる。mG(nG)は、ゲート番号nGのゲート開始ビンに相当するサンプリング番号m’である。
目標が同じ速度であり、ドップラー周波数に基づいて分離することができない2つの目標からの反射RF信号が受信ゲート内に存在する場合、周波数領域の信号fd(nG,k)は、下記式(14)で表される、複数の目標番号ntgtの周波数領域の信号fd,ntgt(nG,k)の合成波となる。
なお、目標番号ntgtの初期相対距離R0,ntgtの受信ビデオ信号V(m’)のサンプリング番号mntgtは、下記式(18)で表される。なお、サンプリング番号mntgtは、下記式(18)式に示すように、整数でなくてもよく小数点以下の値が存在してもよい。
このため、各々の目標の周波数領域変換後の信号の振幅最大値を示す周波数領域のサンプリング番号kpeakの位相が変化しないような制御が可能になる。
すなわち、ゲート番号nGによらず、目標番号ntgtの初期相対距離R0,ntgtの位相θntgtを示す。この結果、未知数が減るため、少ない演算で複数の目標距離が算出可能なレーダ装置を得ることが可能になる。
α1は、振幅最大値となる目標1の周波数領域の信号の実部である。
β1は、振幅最大値となる目標1の周波数領域の信号の虚部である。
α2は、振幅最大値となる目標2の周波数領域の信号の実部である。
β2は、振幅最大値となる目標2の周波数領域の信号の虚部である。
一方、図13Aから図13Eに示したように、ゲート番号nGによらず、各々の目標の位相θntgtを変化させずに、ゲート番号nGに基づいて各々の目標からの反射RF信号が受信ゲート内に存在している割合だけが変化している。すなわち、実施の形態1に係るレーダ装置1では、反射RF信号(受信RF信号)の実部および虚部のみが変化するようにゲート処理が行われる。目標距離算出部62では、この特性を利用して、ドップラー周波数で互いに分離できない目標距離の異なる複数の目標が受信ゲート内に存在する場合であっても、各々の目標距離を算出することが可能である。
図16および図17において、目標距離算出部62は、予め設定された目標数Ntgt=2である場合を前提として目標距離を算出する。
観測されたゲート番号nGの受信ゲート内に存在する反射RF信号の実部zα(nG)と虚部zβ(nG)は、下記式(19)および下記式(20)で表される。
さらに、目標距離算出部62は、下記式(23に従って連立方程式を解くことにより、目標1のサンプリング番号m’1および目標2のサンプリング番号m’2である場合の目標番号ntgt=1の目標からの反射RF信号の虚部β’1,m’1,m’2と、目標1のサンプリング番号m’1および目標2のサンプリング番号m’2である場合の目標番号ntgt=2の目標からの反射RF信号の虚部β’2,m’1,m’2とを算出する。
ここまでの処理がステップST1dである。なお、mstは、想定する複数の目標距離の組み合わせ(以下、目標距離候補と記載する)の目標のサンプリング開始番号であり、Δmは、想定する目標のサンプリング番号の間隔、medは、想定する複数の目標距離候補の目標のサンプリング終了番号であり、nG,1は、予め設定された番号1のゲート番号、nG,2は、予め設定された番号2のゲート番号である。
なお、複数の受信ゲート内の周波数領域の信号の実部および虚部のうち、目標距離の算出に用いる信号の実部および虚部は、当該信号の信号強度に基づいて選択してもよい。
下記式(24)は、全ての受信ゲートを用いた場合を示しているが、目標数Ntgtより多い受信ゲートの観測値があればよい。なお、複数の受信ゲートのうち、受信ゲート内の信号の信号強度に基づいて、目標距離の算出に使用する受信ゲートを選択してもよい。
目標距離算出部62は、下記式(24)で表される連立方程式を、受信信号比率x(mG(nG),mntgt)で偏微分し、下記式(25)に従って目標距離候補の評価値を算出する。続いて、目標距離算出部62は、下記式(25)を、下記式(26)のように定義する。ここで、信号比率に関する行列Xm’1,m’2、目標信号の実部および虚部に関する行列Am’1,m’2、観測値に関する行列Zm’1,m’2は、下記式(27)で表される。
図18は、目標1のサンプリング番号と目標2のサンプリング番号の組み合わせと目標距離候補の評価値との関係を示す図である。図18において、縦軸は目標1のサンプリング番号m’1であり、横軸は目標2のサンプリング番号m’2である。図18に示すように、目標距離算出部62は、実部の残差εα(m’1,m’2)および虚部の残差εβ(m’1,m’2)を用いて、下記式(30)に従い、評価値ε(m’1,m’2)を算出する。目標距離算出部62は、下記式(31)に従い、評価値ε(m’1,m’2)を最大にする目標1のサンプリング番号m”1と目標2のサンプリング番号m”2とを算出する。ここで、argmaxε(p,q)は、目標距離候補の評価値ε(p,q)を最大にする引数p,qを算出する関数である。
この後、目標距離算出部62は、下記式(32)を用いて、目標番号ntgtの目標距離R”0,ntgtを算出する(ステップST2d、ステップST2e)。
このように実部および虚部の情報を用いることで、測距精度が向上する効果がある。
目標距離算出部62は、実部あるいは虚部のみを用いても、複数の目標距離算出は可能である。また、目標距離算出部62は、目標数が1つであっても目標距離の算出が可能である。目標数が1である場合、m’1のみとして算出すればよい。
例えば、ゲート処理部60が、複数の受信ゲートを設定して狭帯域フィルタ後の信号を各々の受信ゲート内に存在する目標の周波数領域の信号が同じ位相になるように生成し、周波数領域変換部61が、各々の受信ゲート内に存在する信号に対して同じサンプリング番号から周波数領域変換して周波数領域の信号を生成する。ゲート処理部60は、ゲート番号nGによらず、各々の目標の実部および虚部だけが変化するようにゲート処理を行うため、目標距離算出部62は、この特性を利用して、想定する受信信号比率と観測値である実部および虚部のうちの少なくとも一方に基づいて、同じ速度で、受信ゲート内に複数の目標からの反射信号が存在した場合であっても目標距離を算出することができる。
なお、実施の形態1では、目標数Ntgtを2としたが、2以外の自然数であっても同様に目標数分の目標距離を算出することは可能である。
図19は、本発明の実施の形態2に係るレーダ装置の信号処理部6Aの構成を示すブロック図である。図19において図1と同一の構成要素には同一の符号を付して説明を省略する。実施の形態2に係るレーダ装置は、図1と同様に、空中線2、送信部3、送受切替部4、受信部5および表示器7を備えている。実施の形態2に係るレーダ装置では、信号処理部6の代わりに、信号処理部6Aが設けられている。
目標距離算出部62Aは、目標候補検出部63によって検出された目標候補の周波数領域の信号の実部および虚部のうちの少なくとも一方に基づいて目標距離を算出する。
目標候補検出部63は、周波数領域変換部61によって生成された周波数領域の信号の信号強度に基づいて目標候補を検出する。
目標距離算出部62Aは、想定する目標数の範囲内で目標数n’tgtを設定する(ステップST1f)。目標距離算出部62Aは、想定する目標数n’tgtに応じて下記式(33)に従って連立方程式を導出する。mG(nG,tgt)は、目標候補ntgtのゲート番号nG,tgtのゲート開始ビンに相当するサンプリング番号m’である。
目標距離算出部62Aは、実部の残差εα(m’1,・・・,m’n’tgt)および虚部の残差εβ(m’1,・・・,m’n’tgt)を用いて下記式(39)に従い、目標距離候補の評価値ε(m’1,m’2)を算出する。
目標距離算出部62Aは、下記式(40)に従い、目標距離候補の評価値ε(m’1,・・・,m’n’tgt)を最大にする、目標数N”tgtと、各々の目標のサンプリング番号mn’tgtを算出する。なお、argmaxε(q,p,・・・,q)は、目標距離候補の評価値ε(q,p,・・・,q)を最大にする変数q、引数p,・・・,qを算出する関数である。
目標候補検出部63によって検出された目標候補のうち、目標候補検出部63がさらに信号強度に基づいて目標候補を選定することで、目標距離をさらに高精度に算出することが可能となる。
Claims (13)
- 送信信号を空間に放射する送信部と、
前記送信信号が空間内の目標で反射されて戻った信号である受信信号を受信する受信部と、
前記受信信号に対して複数の受信ゲートを設定したゲート処理を行い、ゲート処理後の信号を生成するゲート処理部と、
前記ゲート処理後の信号に対して周波数領域変換を行い、周波数領域の信号を生成する周波数領域変換部と、
前記周波数領域変換部によって生成された複数の受信ゲートの周波数領域の信号の実部および虚部のうちの少なくとも一方に基づいて、目標距離を算出する目標距離算出部とを備えたこと
を特徴とするレーダ装置。 - 前記目標距離算出部は、複数の受信ゲートの周波数領域の信号の実部および虚部のうちの少なくとも一方を用いて、各々の受信ゲート内にある目標からの受信信号比率に基づく目標距離候補の連立方程式を解いて目標距離候補の評価値を算出し、目標距離候補の評価値に基づいて目標距離を算出すること
特徴とする請求項1記載のレーダ装置。 - 前記目標距離算出部は、複数の受信ゲートの周波数領域の信号の実部および虚部のうちの少なくとも一方を用いて、各々の受信ゲート内にある目標からの受信信号比率に基づく目標距離候補の連立方程式を導出し、導出した前記連立方程式を最小二乗法を用いて解くことにより目標距離候補の評価値を算出し、目標距離候補の評価値に基づいて目標距離を算出すること
特徴とする請求項1記載のレーダ装置。 - 前記目標距離算出部は、目標距離候補と観測値に基づいて目標距離候補の評価値を算出すること
を特徴とする請求項2または請求項3記載のレーダ装置。 - 前記目標距離算出部は、予め設定された目標数に基づいて目標距離を算出すること
を特徴とする請求項1記載のレーダ装置。 - 前記目標距離算出部は、目標距離候補の評価値に基づいて目標数を算出し、目標数分の目標距離を算出すること
を特徴とする請求項2または請求項3記載のレーダ装置。 - 前記周波数領域変換部は、各々の受信ゲート内にある目標の周波数領域変換後の信号の位相が同じになるように、各々の受信ゲートの位置によらず、同時刻に周波数領域変換を開始すること
を特徴とする請求項1記載のレーダ装置。 - 前記ゲート処理部は、ゲート処理に加え、前記受信信号に対して帯域通過フィルタ処理を行い、帯域通過フィルタ処理後の信号を生成すること
を特徴とする請求項1記載のレーダ装置。 - 前記ゲート処理部は、各々の受信ゲート内にある目標の周波数領域変換後の信号の位相が同じになるように、各々の受信ゲートの位置によらず、同時刻に帯域通過フィルタ処理を開始すること
を特徴とする請求項8記載のレーダ装置。 - 前記周波数領域変換部によって生成された周波数領域の信号の信号強度に基づいて目標候補を検出する目標候補検出部を備え、
前記目標距離算出部は、前記目標候補検出部によって検出された目標候補の周波数領域の信号の実部および虚部のうちの少なくとも一方に基づいて、目標距離を算出すること
を特徴とする請求項1記載のレーダ装置。 - 前記目標距離算出部は、予め設定した複数の受信ゲートの周波数領域の信号の実部および虚部のうちの少なくとも一方を用いて目標距離を算出すること
特徴とする請求項1記載のレーダ装置。 - 前記目標距離算出部は、信号強度に基づいて選択した複数の受信ゲートの周波数領域の信号の実部および虚部のうちの少なくとも一方を用いて目標距離を算出すること
特徴とする請求項1記載のレーダ装置。 - 送信部が、送信信号を空間に放射するステップと、
受信部が、前記送信信号が空間内の目標で反射されて戻った信号である受信信号を受信するステップと、
ゲート処理部が、前記受信信号に対して複数の受信ゲートを設定したゲート処理を行い、ゲート処理後の信号を生成するステップと、
周波数領域変換部が、前記ゲート処理後の信号に対して周波数領域変換を行い、周波数領域の信号を生成するステップと、
目標距離算出部が、前記周波数領域変換部によって生成された複数の受信ゲートの周波数領域の信号の実部および虚部のうちの少なくとも一方に基づいて、目標距離を算出するステップとを備えたこと
を特徴とする目標距離算出方法。
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