WO2020054031A1 - レーダ装置および目標距離計測方法 - Google Patents
レーダ装置および目標距離計測方法 Download PDFInfo
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- WO2020054031A1 WO2020054031A1 PCT/JP2018/034019 JP2018034019W WO2020054031A1 WO 2020054031 A1 WO2020054031 A1 WO 2020054031A1 JP 2018034019 W JP2018034019 W JP 2018034019W WO 2020054031 A1 WO2020054031 A1 WO 2020054031A1
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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
- G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
- G01S13/28—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses
Definitions
- the present invention relates to a radar device for measuring a target distance and a target distance measuring method.
- the radar device described in Patent Document 1 radiates a transmission high-frequency signal into the air and receives a transmission high-frequency signal reflected by a target.
- a conventional radar apparatus generates a sum signal and a difference signal by setting reception gates having different gate widths with respect to a reception high-frequency signal, and calculates a ratio between the sum signal and the difference signal and a distance to a target (hereinafter, target distance and target distance).
- the target distance is measured using a discriminant pattern indicating the relationship with the target distance.
- An object of the present invention is to solve the above problems and to provide a radar apparatus and a target distance measuring method capable of accurately measuring a target distance even when a plurality of targets exist in a reception gate.
- the radar device includes a transmission unit, a reception unit, a gate processing unit, a demodulation processing unit, a target candidate detection unit, and a target candidate distance calculation unit.
- the transmitting unit outputs a transmission signal that has been subjected to intra-pulse modulation.
- the receiving unit generates a reception signal based on the transmission signal reflected by a target in the space.
- the gate processing unit performs a gate process in which a plurality of reception gates are set on the received signal, and generates a signal after the gate process.
- the demodulation processing unit performs demodulation processing on the gated signal based on intra-pulse modulation to generate a demodulated signal.
- the frequency domain transform processing unit performs frequency domain transform on the demodulated signal to generate a frequency domain signal.
- the target candidate detection section detects a target candidate based on the intensity of the signal in the frequency domain.
- the target candidate distance calculation unit calculates the distance of the target candidate detected by the target candidate detection unit.
- gating processing in which a transmission signal subjected to intra-pulse modulation is radiated into space and a plurality of reception gates are set for a reception signal generated based on a transmission signal reflected by a target in space Perform demodulation processing on the gated signal, perform frequency domain conversion on the demodulated signal, detect target candidates based on the strength of the frequency domain signal, and determine the distance of the target candidate. calculate.
- the target distance can be accurately measured.
- FIG. 2 is a block diagram illustrating a configuration of a radar device according to Embodiment 1.
- FIG. 3 is a block diagram illustrating a configuration of a transmission unit according to Embodiment 1.
- 5 is a block diagram illustrating a configuration of a receiving unit according to Embodiment 1.
- FIG. 4A is a block diagram showing a hardware configuration for realizing the functions of the radar device according to Embodiment 1.
- FIG. 4B is a block diagram showing a hardware configuration for executing software for realizing the functions of the radar device according to Embodiment 1.
- 4 is a flowchart illustrating an operation of the radar device according to the first embodiment.
- FIG. 6A is a schematic diagram illustrating an outline of a process performed by the signal processing unit according to the first embodiment.
- FIG. 6A is a schematic diagram illustrating an outline of a process performed by the signal processing unit according to the first embodiment.
- FIG. 6B is a diagram illustrating signals in the frequency domain corresponding to a plurality of targets having the same speed ⁇ .
- FIG. 6C is a diagram illustrating a waveform of a signal in the frequency domain corresponding to the target of the speed ⁇ in the gate number direction.
- FIG. 6D is a diagram illustrating a waveform in the distance direction of the signal after the inverse frequency domain conversion processing corresponding to the target of the velocity ⁇ .
- 5 is a flowchart illustrating an operation of the transmission unit according to the first embodiment.
- FIG. 3 is a diagram illustrating a waveform of a transmission RF signal.
- 5 is a flowchart illustrating an operation of the receiving unit according to the first embodiment.
- FIG. 3 is a diagram illustrating a waveform of a received video signal.
- FIG. 6 is a flowchart illustrating an operation of the signal processing unit according to the first embodiment. It is a diagram showing a relationship between the received gate and the sampling number m 'of the gate number n G.
- FIG. 13A is a diagram showing a waveform of a received video signal.
- FIG. 13B is a diagram showing a waveform of a signal after gate processing corresponding to the reception gate G6.
- FIG. 13C is a diagram showing a waveform of a signal after gate processing corresponding to the reception gate G7.
- FIG. 13D is a diagram showing a waveform of a signal after gate processing corresponding to the reception gate G8.
- FIG. 14A is a diagram showing a waveform of a received video signal.
- FIG. 14A is a diagram showing a waveform of a received video signal.
- FIG. 14B is a diagram showing a waveform of a signal after demodulation processing corresponding to the reception gate G6.
- FIG. 14C is a diagram showing a waveform of a signal after demodulation processing corresponding to the reception gate G7.
- FIG. 14D is a diagram showing a waveform of a signal after demodulation processing corresponding to reception gate G8.
- FIG. 15A is a diagram illustrating a waveform of an observed value of a signal in a frequency domain corresponding to a plurality of targets having the same speed in the reception gate when the transmission signal is not intra-pulse-modulated.
- FIG. 15A is a diagram illustrating a waveform of an observed value of a signal in a frequency domain corresponding to a plurality of targets having the same speed in the reception gate when the transmission signal is not intra-pulse-modulated.
- FIG. 15B is a diagram showing the waveform of a signal in the frequency domain for each target at the same speed in the reception gate when the transmission signal is not intra-pulse-modulated.
- FIG. 15C is a diagram illustrating a waveform of an observation value of a signal in a frequency domain corresponding to a plurality of targets having the same speed in the reception gate when the transmission signal is intra-pulse-modulated.
- FIG. 15D is a diagram illustrating a waveform of a signal in the frequency domain for each target at the same speed in the reception gate when the transmission signal is intra-pulse-modulated.
- FIG. 16A is a diagram showing a waveform of a received video signal.
- FIG. 16B is a diagram illustrating a waveform in the gate number direction of an observation value of a signal in the frequency domain for each target at the same speed in the reception gate when the transmission signal is not intra-pulse-modulated.
- FIG. 16C is a diagram illustrating a waveform in the gate number direction of the observed value of the signal in the frequency domain for each target at the same speed in the reception gate when the transmission signal is intra-pulse-modulated.
- FIG. 17A is a diagram showing a waveform of a signal in a frequency domain corresponding to each of the same-speed targets in the reception gate.
- FIG. 17B is a diagram showing the waveform of the signal after the inverse frequency domain transform processing corresponding to each of the targets of the same speed in the reception gate.
- FIG. 1 is a block diagram illustrating a configuration of the radar device 1 according to the first embodiment.
- the radar apparatus 1 radiates a transmission high-frequency signal (hereinafter, referred to as a transmission RF signal) subjected to intra-pulse modulation to a space, and transmits a transmission RF signal reflected by a target in the space to a reception high-frequency signal (hereinafter, reception RF signal). (Referred to as a signal), and calculates the distance of a target candidate that can be an observation target based on the received video signal generated from the received RF signal.
- a transmission RF signal transmission high-frequency signal
- reception RF signal reception high-frequency signal
- the radar device 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 demodulation processing unit 61, a filter processing unit 62, a frequency domain conversion unit 63, a high precision processing unit 64, a target candidate detection unit 65, and a target candidate distance calculation unit 66. Note that the signal processing unit 6 may not include one or both of the filter processing unit 62 and the high-precision processing unit 64.
- the antenna 2 radiates the transmission RF signal input from the transmission / reception switching unit 4 into space.
- the transmission unit 3 outputs the transmission RF signal subjected to the intra-pulse modulation to the transmission / reception switching unit 4.
- the transmission / reception switching unit 4 switches output of a transmission RF signal from the transmission unit 3 to the antenna 2 and output of a reception RF signal from the antenna 2 to the reception unit 5 at a timing set by the transmission unit 3.
- the antenna 2 receives and receives the reflected wave of the transmission RF signal reflected by the target in the space.
- the receiving unit 5 receives the received RF signal received by the antenna 2 and generates a received video signal based on the received RF signal.
- the signal processing unit 6 calculates the distance of the target candidate based on the received video signal input from the receiving unit 5, and outputs the calculated distance of the target candidate to the display 7.
- the display 7 displays information on the distance between the target candidates.
- the information on the distance of the target candidate includes, for example, a target number set for each target candidate and information indicating the distance from the radar device 1 to the target candidate.
- the gate processing unit 60 receives the received video signal from the receiving unit 5 and performs a gate process on the received video signal by setting a plurality of reception gates to generate a gated signal.
- the demodulation processing unit 61 performs demodulation processing on the gated signal based on intra-pulse modulation, and generates a demodulated signal.
- the filter processing unit 62 performs band-pass filtering on the signal after demodulation, and generates a signal after band-pass filtering.
- the frequency domain transforming unit 63 performs a frequency domain transform process on the signal after the band pass filter process to generate a frequency domain signal.
- the frequency domain conversion unit 63 receives the demodulated signal from the demodulation processing unit 61 and performs frequency domain conversion on the demodulated signal. To generate a signal in the frequency domain.
- the high-precision processing unit 64 is a conversion processing unit that performs high-precision processing on a signal in the frequency domain and generates a signal after the high-precision processing.
- High-accuracy processing means that frequency domain conversion processing is performed on signals in a plurality of frequency domains corresponding to a plurality of reception gates, and the frequency-domain conversion processing is performed on the signal after the frequency domain conversion processing with a score greater than the frequency domain conversion score. This is a process for performing an inverse frequency domain conversion process.
- the signal after the high-precision processing is the signal after the inverse frequency domain conversion processing.
- the target candidate detection unit 65 detects a target candidate based on the intensity of the signal after the high precision processing.
- the target candidate detection unit 65 detects a target candidate based on the intensity of the signal in the frequency domain input from the frequency domain conversion unit 63.
- the target candidate distance calculation unit 66 calculates the distance of the target candidate detected by the target candidate detection unit 65.
- FIG. 2 is a block diagram showing the configuration of the transmission unit 3.
- the transmission unit 3 includes a transmitter 30, an intra-pulse modulator 31, a pulse modulator 32, and a local oscillator 33.
- the transmitter 30 outputs the transmission RF signal after intra-pulse modulation generated by the intra-pulse modulator 31 to the antenna 2 through the transmission / reception switching unit 4.
- the intra-pulse modulator 31 performs intra-pulse modulation on the transmission RF signal after the pulse modulation process generated by the pulse modulator 32 to generate a transmission RF signal after intra-pulse modulation.
- the pulse modulator 32 performs pulse modulation on a local oscillation signal input from the local oscillator 33, and generates a transmission RF signal after pulse modulation.
- the local oscillator 33 generates a local oscillation signal and outputs the signal to the receiving unit 5 and the pulse modulator 32 shown in FIG.
- 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 reception RF signal received by the antenna 2 through the transmission / reception switching unit 4.
- the receiver 50 down-converts the received RF signal based on the local oscillation signal input from the local oscillator 33, performs signal processing, and generates a received video signal.
- the signal processing includes, for example, band-pass filter processing, amplification processing, and phase detection processing.
- the received video signal generated by the receiver 50 is output to the A / D converter 51.
- the A / D converter 51 converts the received video signal input from the receiver 50 into a digital signal, and outputs the converted received video signal to the signal processing unit 6.
- the radar apparatus 1 includes a processing circuit for executing processing from step ST1 to step ST9 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 device 1.
- FIG. 4B is a block diagram illustrating a hardware configuration that executes software for realizing the functions of the radar device 1.
- the antenna 100 is the antenna 2 shown in FIG. 1
- the display 101 is the display 7 shown in FIG.
- the input / output interface 102 is an interface that relays the output of the transmission RF signal from the transmitter 3 to the antenna 100 shown in FIG. 1 and the output of the reflected RF signal from the antenna 100 to the receiver 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 for relaying an output signal to the display 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 illustrated in FIG.
- a volatile memory such as a synchronous dynamic random access memory (SDRAM), a hard disk drive (HDD), or a solid state drive (SSD) may be used.
- 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 provided independently of the radar device 1 and communicable with the radar device 1, for example, a storage device provided on a cloud.
- the signal path 105 is a bus for transmitting signal data.
- the input / output interface 102, the external storage device 103, and the processing circuit 104 are interconnected by the signal path 105.
- the input / output interface 102, the external storage device 103, the processor 106, and the memory 107 are interconnected by a signal path 105.
- the processing circuit 104 includes, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, and an ASIC (Application Specialized Integrated). (Circuit), FPGA (Field-Programmable Gate Array), or a combination thereof.
- the functions of the transmission unit 3, the reception unit 5, and the signal processing unit 6 in the radar device 1 may be realized by separate processing circuits, or these functions may be realized by one processing circuit.
- the processing circuit is the processor 106 illustrated in FIG. 4B
- the functions of the transmission unit 3, the reception unit 5, and the signal processing unit 6 in the radar device 1 are realized by software, firmware, or a combination of software and firmware. You.
- the software or firmware is described as a program and stored in the memory 107.
- the processor 106 realizes the functions of the transmission unit 3, the reception unit 5, and the signal processing unit 6 in the radar device 1 by reading and executing the program stored in the memory 107. That is, the radar apparatus 1 includes the memory 107 for storing a program that, when executed by the processor 106, results in the processing of steps ST1 to ST9 shown in FIG. These programs cause a computer to execute the procedure or method of the transmitting unit 3, the receiving unit 5, and the signal processing unit 6.
- 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, and the signal processing unit 6.
- the memory 107 includes, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), a nonvolatile semiconductor memory such as an EEPROM (Electrically-EROM), or the like.
- RAM Random Access Memory
- ROM Read Only Memory
- flash memory an EPROM (Erasable Programmable Read Only Memory)
- nonvolatile semiconductor memory such as an EEPROM (Electrically-EROM), or the like.
- a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, and the like are applicable.
- Some of the functions of the transmission unit 3, the reception unit 5, and the signal processing unit 6 may be partially realized by dedicated hardware and partially realized by software or firmware.
- the transmitting unit 3 and the receiving unit 5 realize their functions by the processing circuit 104 that is dedicated hardware, and the signal processing unit 6 executes the function by reading and executing the program stored in the memory 107 by the processor 106.
- 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 device 1 according to the first embodiment, and shows a target distance measuring method according to the first embodiment.
- Intra-pulse modulation includes intra-pulse code modulation and intra-pulse frequency modulation.
- FIG. 6A is a schematic diagram showing an outline of the processing by the signal processing unit 6.
- FIG. 6B is a diagram illustrating signals in the frequency domain corresponding to a plurality of targets having the same speed ⁇ .
- FIG. 6C is a diagram illustrating a waveform of a signal in the frequency domain corresponding to the target of the speed ⁇ in the gate number direction.
- FIG. 6D is a diagram illustrating a waveform in the distance direction of the signal after the inverse frequency domain conversion processing (the signal after the high precision processing) corresponding to the target of the velocity ⁇ .
- the transmission unit 3 outputs the transmission RF signal subjected to the intra-pulse code modulation to the transmission / reception switching unit 4 (step ST1).
- the transmission / reception switching unit 4 outputs a transmission RF signal to the antenna 2 at a timing set by the transmission unit 3.
- the antenna 2 radiates the transmission RF signal input from the transmission / reception switching unit 4 into space.
- the reflected wave of the transmission RF signal reflected by the target in the space is received by the antenna 2.
- the receiving unit 5 inputs the signal received by the antenna 2 as a received RF signal, and generates a received video signal based on the received RF signal (Step ST2).
- the received video signal generated by the receiving unit 5 is output to the signal processing unit 6.
- the gate processing unit 60 included in the signal processing unit 6 performs a gate process in which a plurality of reception gates are set on the received video signal, and generates a signal after the gate process (step ST3).
- the reception gate is set.
- the demodulation processing unit 61 performs a demodulation process on the gate-processed signal based on the intra-pulse modulation to generate a demodulated signal (step ST4).
- the demodulation processing unit 61 demodulates the code of the received video signal in the reception gate for each reception gate.
- the filter processing unit 62 performs a filter process on the signal after the demodulation process, and generates a signal after the filter process (step ST5).
- the filter processing unit 62 performs a narrow band filter process on the demodulated signal for each reception gate.
- the frequency domain transforming section 63 performs a frequency domain transform process on the signal after the filter process to generate a frequency domain signal (step ST6).
- the frequency domain transforming unit 63 performs a fast Fourier transform (hereinafter, referred to as FFT) on the signal subjected to the filtering process for each reception gate.
- the signal in the frequency domain is a signal including the Doppler frequency, that is, the velocity ⁇ , and information on the distance corresponding to the reception gate interval.
- the waveform of the signal shown in FIG. 6B is the waveform of the signal in the frequency domain corresponding to each of the plurality of targets having the same speed ⁇ .
- the signal in the frequency domain corresponding to the target of the speed ⁇ has a spectral waveform in the gate number direction as shown in FIG. 6C, and has the maximum power at the gate number n G of the receiving gate close to the target distance, and The target distance can be measured.
- IFFT inverse fast Fourier transform
- the signal in the frequency domain is sampled with high precision.
- the waveform of the signal after the high precision processing has a maximum peak near the target distance as shown in FIG. 6D.
- the signal after the high accuracy processing generated by the high accuracy processing unit 64 is output to the target candidate detection unit 65.
- the target candidate detection unit 65 performs a target candidate detection process based on the signal strength after the high accuracy processing (step ST8). Thereafter, the target candidate distance calculation unit 66 calculates the distance of the target candidate detected by the target candidate detection unit 65 (Step ST9).
- the display 7 displays information on the distance of the target candidate input from the target candidate distance calculation unit 66.
- FIG. 7 is a flowchart showing the operation of the transmission unit 3, and shows the details of the process of step ST1 in FIG.
- FIG. 8 is a diagram showing a waveform of the transmission RF signal Tx (t).
- the local oscillator 33 generates a local oscillation signal L 0 (t) having a constant frequency represented by the following equation (1) (step ST1a).
- Local oscillation signal L 0 (t) generated by local oscillator 33 is output to receiving section 5 and pulse modulator 32.
- t is time
- a L is the amplitude of the local oscillation signal L 0 (t)
- f 0 is the transmit frequency.
- ⁇ 0 is an initial phase of the local oscillation signal L 0 (t)
- T obs is an observation time
- j is an imaginary unit.
- the pulse modulator 32 performs a pulse modulation process on the local oscillation signal L 0 (t) according to the following equation (2) using a preset pulse repetition period T pri and pulse width T 0.
- the transmission RF signal Tx pls (t) is generated (step ST2a).
- the transmission RF signal Tx pls (t) generated by the pulse modulator 32 is output to the intra-pulse modulator 31.
- h is the hit number, and H is the number of hits.
- the number of hits H is represented by the following equation (3).
- floor (X) means an integer obtained by truncating the variable X below the decimal point.
- the intra-pulse modulator 31 uses the preset pulse repetition period T pri , pulse width T 0 and intra-pulse modulation ⁇ Mod (t) with respect to the transmission RF signal Tx pls (t) to obtain the following equation (4).
- T pri pulse repetition period
- T 0 pulse width
- ⁇ Mod intra-pulse modulation ⁇ Mod (t) with respect to the transmission RF signal Tx pls (t) to obtain the following equation (4).
- To generate a transmission RF signal Tx (t) (step ST3a).
- the transmission pulse a shown in FIG. 8 is a transmission pulse of the transmission RF signal Tx (t).
- the intra-pulse modulation code b of the transmission RF signal Tx (t) is an intra-pulse modulation code represented by a 4-bit Barker code shown in the following equation (5). Here, it is assumed that one bit is the sub-pulse width. The number of bits of the intra-pulse modulation code b may be other than 4 bits.
- the intra-pulse modulation applied to the transmission RF signal Tx pls (t) may be multi-level code modulation or intra-pulse frequency modulation.
- the transmitter 30 outputs the transmission RF signal Tx (t) input from the pulse modulator 32 to the transmission / reception switching unit 4 (step ST4a).
- the transmission / reception switching unit 4 outputs the transmission RF signal Tx (t) input from the transmission unit 3 to the antenna 2.
- the antenna 2 radiates the transmission RF signal Tx (t) into the air (space).
- FIG. 9 is a flowchart showing the operation of the receiving unit 5, and shows the details of the process of step ST2 in FIG.
- FIG. 10 is a diagram illustrating a waveform of the received video signal V (m ′).
- the transmission RF signal reflected by the target in the air enters the antenna 2.
- the signal incident on the antenna 2 is output to the receiver 50 as a reception RF signal Rx (t) represented by the following equation (6) (step ST1b).
- n tgt is a target number
- N tgt is a target number.
- the received RF signal Rx ntgt (t) corresponding to the target of the target number n tgt included in the above equation (6) is expressed by the following equation (7).
- a R, ntgt is the amplitude of the received RF signal Rx ntgt (t)
- R 0, ntgt is the initial target relative distance for the target with the target number n tgt
- v ntgt is the target number.
- 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) represented by the above equation (1), and further passes the band-pass filter. After that, signal processing such as amplification and phase detection is performed (step ST2b). As a result, a received video signal V 0 (t) represented by the following equation (8) is generated. The received video signal V 0 (t) generated by the receiver 50 is output to the A / D converter 51.
- V 0, ntgt (t) in the above equation (8) is a received video signal corresponding to the target of the target number n tgt represented by the following equation (9).
- AV, ntgt is the amplitude of the received video signal V 0, ntgt (t) corresponding to the target with the target number n tgt .
- the A / D converter 51 generates a received video signal V (m ′) represented by the following equation (10) by A / D converting the received video signal V 0 (t) input from the receiver 50. (Step ST3b).
- the received video signal V (m ′) generated by the A / D converter 51 is output to the signal processing unit 6.
- m ' is a sampling number and M' is a sampling number.
- V 0, n tgt (m ′) included in the above equation (10) is a received video signal obtained by A / D converting the received video signal V 0, n tgt (t) corresponding to the target with the target number n tgt. .
- the received video signal V 0, n tgt (m ′) is represented by the following equation (11).
- ⁇ t is a sampling interval of the received video signal V 0, n tgt (m ′) that has been A / D converted.
- the received video signal V (m ′) (received video signal c shown in FIG. 10) is a sampled signal.
- the received video signal V (m ') is a combination of a plurality of received video signals generated based on the signals reflected by the transmitted RF signal at each of the plurality of targets.
- a received video signal c1 corresponding to the target of the target number (1) and a received video signal c2 corresponding to the target of the target number (2) are combined.
- the intra-pulse modulation code c1 ' is set in the received video signal c1
- the intra-pulse modulation code c2' is set in the received video signal c2.
- mod (X, Y) is the remainder after dividing the variable X by the variable Y.
- FIG. 11 is a flowchart showing the operation of the signal processing unit 6, and shows details of the processing from step ST3 to step ST9 in FIG.
- the signal processing unit 6 receives the received video signal V (m ′) from the A / D converter 51 provided in the receiving unit 5.
- the gate processing unit 60 included in the signal processing unit 6 uses the gate slide amount ⁇ m G and the gate width set in advance for the received video signal V (m ′) and performs gate processing according to the following equation (12).
- signal V G (n G, m ' ) to produce a (step ST1c).
- M pri is the number of samplings in the pulse repetition period T pri
- M p is the number of samplings in the pulse.
- Figure 12 is a diagram showing the relationship between the receiving gate and the sampling number m 'of the gate number n G.
- the gate processing unit 60 is performing the gating regards the gate width and the pulse width T 0.
- the gate position and the gate width may be arbitrarily set values.
- the gate processor 60 may be set in a shorter gate width than the pulse width T 0 of each of the plurality of receiving gates.
- FIG. 13A is a diagram showing a waveform of the received video signal c.
- FIG. 13B is a diagram illustrating a waveform of the signal d after the gate processing corresponding to the reception gate G6.
- FIG. 13C is a diagram showing a waveform of the signal e after gate processing corresponding to the reception gate G7.
- FIG. 13D is a diagram showing a waveform of the signal f after the gate processing corresponding to the reception gate G8.
- the signal after the gate processing can be represented by V G (n G , m ′).
- Signal d after the gate processing is 'a
- the signal e after the gate processing the signal after gating V G (7, m signal V G after gating (6, m)' a)
- the subsequent signal f is the signal V G (8, m ′) after the gate processing.
- the gate d corresponding to the target having the target number (1) is included in the signal d after the gate processing.
- the processed signal d1 and the gated signal d2 corresponding to the target of target number (2) are combined.
- the gate-processed signal d1 includes the intra-pulse modulation code d1 '
- the gate-processed signal d2 includes the intra-pulse modulation code d2'.
- the gated signal e includes the gated signal e1 corresponding to the target of the target number (1) and the gated signal e2 corresponding to the target of the target number (2). And are synthesized.
- the signal e1 after the gate processing includes the intra-pulse modulation code e1 '
- the signal e2 after the gate processing includes the intra-pulse modulation code e2'.
- the gated signal f includes the gated signal f1 corresponding to the target of the target number (1) and the gated signal f2 corresponding to the target of the target number (2). And are synthesized.
- the signal f1 after the gate processing includes the intra-pulse modulation code f1 ′, and the signal f2 after the gate processing includes the intra-pulse modulation code f2 ′.
- the reception gate G7 is a gate that has been slid by a gate slide amount ⁇ m G from the reception gate G6, and the reception gate G8 is a gate that has been slid by a gate slide amount ⁇ m G from the reception gate G7. Since the gate processing unit 60 performs the gating process, it is not affected by noise other than the reception gate. Therefore, the signal-to-noise ratio (hereinafter, referred to as SNR) in the frequency-domain signal generated by the frequency-domain conversion unit 63. And the radar apparatus 1 with improved target detection performance can be obtained.
- SNR signal-to-noise ratio
- the demodulation processing unit 61 applies the gated signal V G (n G , m ′) generated by the gate processing unit 60 based on the intra-pulse demodulation D ⁇ (n G , m ′). by performing the demodulation processing in accordance with the following equation (13), the signal V G after demodulation process to generate a D (n G, m ') (step ST2c).
- the demodulation processing unit 61 calculates the intra-pulse demodulation D ⁇ (n G , m ′) according to the following equation (14), and uses it for demodulation processing.
- FIG. 14A is a diagram showing a waveform of the received video signal c.
- FIG. 14B is a diagram showing a waveform of signal g after demodulation processing corresponding to reception gate G6.
- FIG. 14C is a diagram showing a waveform of the signal h after demodulation processing corresponding to the reception gate G7.
- FIG. 14D is a diagram illustrating a waveform of the signal i after the demodulation processing corresponding to the reception gate G8.
- the demodulation processing unit 61 generates a signal g after demodulation processing shown in FIG. 14B by performing demodulation processing on the signal d after gate processing shown in FIG. 13B.
- the demodulation processing unit 61 performs a demodulation process on the signal e after the gate processing illustrated in FIG. 13C to generate a signal h after the demodulation processing illustrated in FIG. 14C.
- the demodulation processing unit 61 generates a signal i after the demodulation processing shown in FIG. 14D by performing a demodulation processing on the signal f after the gate processing shown in FIG. 13D.
- the signal after the demodulation processing can be expressed by V G, D (n G, m ').
- the demodulated signal g is the demodulated signal V G, D (6, m ′)
- the demodulated signal h is the demodulated signal V G, D (7, m ′).
- the signal i after the demodulation processing is the signal V G, D (8, m ′) after the demodulation processing.
- the demodulated signal V 0, ntgt, D (n G , m ′) generated based on the received RF signal corresponding to the target with the target number n tgt can be represented by the following equation (15).
- V 0, ntgt (n G , m ′) is a signal after gate processing generated based on the reception RF signal corresponding to the target of the target number n tgt , and ⁇ Mod, D (N G , m ′) is a code after the demodulation processing.
- the demodulated signal g1 corresponding to the target reception RF signal of the target number (1) in the reception gate G6 both the intra-pulse modulation code d1 ′ and the intra-pulse demodulation code match. Therefore, the modulation is unmodulated g1 ′.
- the signal g1 after the demodulation processing is coherently integrated when converted into a frequency-domain signal by the frequency-domain conversion unit 63.
- the demodulated signal g2 corresponding to the target reception RF signal of the target number (2) in the reception gate G6 has a modulation code g2 ′ because the intra-pulse modulation code d2 ′ and the intra-pulse demodulation code do not match. Remains.
- the demodulated signal g2 with the modulation code g2 'remaining is not coherently integrated when converted to a frequency domain signal.
- the demodulated signal g1 is coherently integrated, and the target of the target number (1) can be separated.
- the intra-pulse modulation code h1 ′ does not match the intra-pulse demodulation code. Therefore, the modulation code h1 'remains.
- the modulation code h2 ′ does not match the intra-pulse modulation code h2 ′. Remains.
- the demodulated signals h1 and h2 are not coherently integrated when converted into a frequency domain signal.
- the intra-pulse modulation code i1 ′ does not match the intra-pulse demodulation code. Therefore, the modulation code i1 'remains.
- the demodulated signal i2 corresponding to the target reception RF signal of the target number (2) in the reception gate G8 both the intra-pulse modulation code f2 'and the intra-pulse demodulation code match, so that no i2 '.
- the signal f2 after the demodulation processing is coherently integrated when converted into a frequency-domain signal by the frequency-domain conversion unit 63. In the receiving gate G8, the demodulated signal f2 is coherently integrated, and the target of the target number (2) can be separated.
- the demodulated signal after the modulation is not coherently integrated, but the unmodulated signal after the demodulation is coherently integrated, so that the target separation performance of the radar device 1 is improved.
- the radar apparatus 1 by applying a pulse in the code-modulated into a transmission signal, even if a plurality of targets is present in the one receiving the gate, it is possible to target separation at lower resolutions gate sliding amount Delta] m G.
- the demodulated signal V G, D (n G , m ′) generated by the demodulation processing unit 61 is output to the filter processing unit 62.
- the filter processing unit 62 performs a narrow-band filter process on the demodulated signal V G, D (n G , m ′) to pass a signal in a band around the center spectrum of the frequency domain, and performs narrow-band filtering.
- a signal after band-pass filtering is generated (step ST3c).
- the signal V G, D, f (n G , m) after the narrow band filter processing is represented by the following equation (16).
- m is the sampling number of the signal after the narrow band filter processing
- M is the sampling number of the signal after the narrow band filter processing.
- V G, D , f, ntgt (n G, m) is the signal after the narrowband filter processing expressed by the following formula (17), the gate number n G in the receive gate Corresponds to the target of the target number n tgt .
- a nG, Ntgt is the amplitude of the narrowband filtering the signal after V G, D, f, ntgt (n G, m).
- frequency domain transform section 63 a signal V G after narrowband filtering input from the filter processing unit 62, D, with respect to f (n G, m), frequency domain conversion processing according to the following equation (18)
- k is a sampling number in the frequency domain
- M fft is a frequency domain conversion point.
- the discrete Fourier transform expressed by the following equation (18) is used for the frequency domain transform processing, the frequency domain transform processing may be performed using FFT or chirp z-transform.
- the frequency domain conversion unit 63 similarly applies the frequency according to the above equation (18) to the demodulated signal input from the demodulation processing unit 61.
- a signal f d (n G , k) in the frequency domain is generated.
- the frequency-domain signal f d (n G , k) generated by the frequency-domain conversion unit 63 is output to the high-precision processing unit 64.
- the signal f d (n G , k) in the frequency domain is a signal including the speed ⁇ and information on the distance between the gates, as shown in FIG. 6B. Further, as shown in FIG. 6C, the signal in the frequency domain corresponding to the target of the speed ⁇ has a waveform in the gate number direction. This waveform indicates the maximum power at the reception gate close to the target distance, and the target distance can be measured using the signal in the reception gate. If the signal after demodulation is filtered, the shape of the pulse will be lost and converted to a sine wave. Become. This allows separation of the target each other approaches than the pulse width T 0.
- FIG. 15A is a diagram illustrating a waveform of an observed value of a signal in a frequency domain corresponding to a plurality of targets having the same speed ⁇ in the reception gate when the transmission RF signal is not intra-pulse-modulated.
- the waveforms indicated by solid lines are the gate start bins m G (n G -1), m G (n G ), m G (n G +1), and m G (n G +2) of the gate number n G.
- It is the waveform of the observation value of the signal of a frequency domain in each.
- a frequency domain signal corresponding to the target of the target number (1) and a frequency domain signal corresponding to the target of the target number (2) are synthesized.
- FIG. 15B is a diagram showing a waveform of a signal in the frequency domain for each target at the same speed ⁇ in the reception gate when the transmission RF signal is not intra-pulse-modulated.
- the waveform shown by the broken line is the waveform of the signal in the frequency domain corresponding to the target of target number (1)
- the waveform shown by the dashed line is the signal in the frequency domain corresponding to the target of target number (2). It is a waveform of.
- the waveform of the signal in the frequency domain corresponding to the target of the target number (1) has the maximum power at the distance corresponding to the gate start bin m G (n G ), but also at the distance corresponding to the other gate start bins. High power.
- the waveform of the signal in the frequency domain corresponding to the target of the target number (2) has the maximum power at the distance corresponding to the gate start bin m G (n G +1), but has the maximum power corresponding to the other gate start bins. But the power is high.
- FIG. 15C is a diagram illustrating a waveform of an observed value of a signal in a frequency domain corresponding to a plurality of targets having the same speed ⁇ in the reception gate when the transmission RF signal is intra-pulse-modulated.
- Observed value of the signal in the frequency domain at each of the gate start bins m G (n G ⁇ 1), m G (n G ), m G (n G +1), and m G (n G +2) of the gate number n G It is a waveform of.
- These frequency domain signals are combined with a frequency domain signal corresponding to the target of the target number (1) and a frequency domain signal corresponding to the target of the target number (2).
- FIG. 15D is a diagram showing a waveform of a signal in the frequency domain for each target at the same speed ⁇ in the reception gate when the transmission RF signal is intra-pulse-modulated.
- the waveform shown by the broken line is the waveform of the signal in the frequency domain corresponding to the target of the target number (1)
- the waveform shown by the dashed line is the signal in the frequency domain corresponding to the target of the target number (2).
- It is a waveform of.
- the waveform of the signal in the frequency domain corresponding to the target of target number (1) has the maximum power at the distance corresponding to the gate start bin m G (n G ), and has relatively low power at the distance corresponding to the other gate start bins. It has become.
- the waveform of the signal in the frequency domain corresponding to the target of the target number (2) has the maximum power at the distance corresponding to the gate start bin m G (n G +1) and is relatively low at the distance corresponding to the other gate start bins. Power.
- FIG. 16A is a diagram showing a waveform of the received video signal c.
- FIG. 16B is a diagram showing a waveform in the gate number direction of the observed value of the signal in the frequency domain for each target at the same speed ⁇ in the reception gate when the transmission signal is not intra-pulse-modulated.
- a waveform j1 is a waveform of a signal in a frequency domain generated based on a received video signal c1 obtained by receiving a transmission RF signal that is not intra-pulse-modulated.
- the waveform j2 is a waveform of a signal in the frequency domain generated based on the received video signal c2 obtained by receiving the transmission RF signal that is not modulated in the pulse.
- FIG. 16C is a diagram illustrating a waveform in the gate number direction of the observed value of the signal in the frequency domain for each target at the same speed ⁇ in the reception gate when the transmission RF signal is intra-pulse-modulated.
- a waveform k1 is a waveform of a signal in the frequency domain generated based on the received video signal c1 obtained by receiving the transmission RF signal modulated in the pulse.
- the waveform k2 is a waveform of a signal in the frequency domain generated based on the received video signal c2 obtained by receiving the transmission RF signal subjected to the intra-pulse modulation.
- intra-pulse modulation is not applied to the transmission signal
- the distance resolution in the radar device is reduced, and the distance measurement performance of the targets Deteriorates.
- the reception signal is subjected to gate processing, demodulation processing, filter processing, and frequency domain conversion processing, as shown in FIGS. 15C, 15D, and 16C.
- the range resolution in the radar device is improved, and the target ranging performance is improved.
- the following equation (19) is provided between the distance resolution ⁇ 0 of the radar apparatus when the transmission signal is not subjected to intra-pulse modulation and the distance resolution ⁇ b of the radar apparatus when the transmission signal is subjected to intra-pulse modulation. Holds.
- the distance resolution .DELTA..tau b is a high resolution than the distance resolution .DELTA..tau 0.
- the distance measurement accuracy ⁇ 0, accuracy of the radar device when the transmission signal is not subjected to intra-pulse modulation and the distance measurement accuracy ⁇ b, accuracy of the radar device when the transmission signal is subjected to intra-pulse modulation are: ,
- the following equation (20) holds.
- the ranging accuracy ⁇ b accuracy is higher than the ranging accuracy ⁇ 0, accuracy .
- snr is a signal-to-noise ratio.
- the signal f d, ntgt (n G , k) in the frequency domain corresponding to the target of the target number n tgt in the reception gate of the gate number n G is represented by the following equation (21).
- the signal f d, ntgt (n G , k) in the frequency domain indicates the maximum amplitude value.
- k peak is a sampling number k of the frequency-domain signal f d, ntgt (n G , k) indicating the maximum amplitude value.
- the gate processor 60 passes the start time of a plurality of receiving gates are different from each other, the signal after gating V G (n G, m ' ) and narrowband filtering the signal after V G (n G, In m), the time is synchronized between the reception gates.
- the frequency domain conversion unit 63 starts the frequency domain conversion processing at the same time (the same sampling number) regardless of the positions of the plurality of reception gates.
- the demodulation processing section 61 performs demodulation processing on the signal after the gate processing, and demodulates the intra-pulse modulation code. For this reason, in the radar apparatus 1, it is possible to perform control such that the sampling number k peak indicating the maximum amplitude of the signal in the frequency domain corresponding to each of the plurality of targets does not change.
- the high-precision processing unit 64 performs high-precision processing on the frequency-domain signal f d (n G , k) input from the frequency-domain conversion unit 63, and generates a signal after the high-precision processing.
- the high-precision processing unit 64 performs a Fourier transform process on the signal f d (n G , k) in the frequency domain corresponding to each of the plurality of reception gates according to the following equation (23), thereby obtaining the frequency.
- NG fft is the number of Fourier transform points (the number of frequency domain transform points between gates)
- q is the sampling number of the signal after the Fourier transform processing.
- the high-precision processing unit 64 performs an inverse Fourier transform process on the signal f d, G (q, k) in the frequency domain according to the following equation (24), as shown in the following equation (25), to obtain the number of Fourier transform points N
- the conversion is performed with the number of conversion points NG, ifft greater than G, fft , and the signal f ′ d, G (q ift , k) after the high-precision processing is generated.
- NG ifft is the number of inverse Fourier transform points (the number of inverse frequency domain transform points), and corresponds to the number of signals in the distance direction after the high-accuracy processing.
- q ift is a sampling number in the distance direction of the signal after the high precision processing.
- the distance sampling interval in the signal f ′ d, G (q ifft , k) after the high-precision processing is performed.
- .DELTA..tau b, ifft is, 1 / N G of Delta] m G as shown in the following formula (26), a multi.
- the distance sampling interval is subdivided from ⁇ m G to ⁇ b, ifft .
- FIG. 17A is a diagram showing a waveform of a signal in a frequency domain corresponding to each of the same-speed targets in the reception gate.
- the receiving gate of the gate number n G has 1/4 of the gate width of the pulse width T 0.
- a waveform L1 indicated by a broken line is a waveform of a signal in the frequency domain corresponding to the target of the target number (1)
- a waveform L2 indicated by a dashed line is a waveform of a signal in the frequency domain corresponding to the target of the target number (2). It is.
- FIG. 17B is a diagram showing a waveform of a signal after the high-precision processing corresponding to each of the targets at the same speed in the reception gate.
- the distance sampling interval corresponding to the gate number n G is subdivided from ⁇ m G ⁇ b, the ifft.
- a waveform m1 indicated by a solid line is a waveform of a signal after the high precision processing corresponding to the target of the target number (1)
- a waveform m2 indicated by a dashed line is a high precision improvement corresponding to the target of the target number (2). It is a signal waveform after processing.
- the distance sampling interval is obtained by performing high-precision processing on the signal in the frequency domain corresponding to the target of the target number (1) and the signal in the frequency domain corresponding to the target of the target number (2). Is subdivided into ⁇ b, ifft . Accordingly, even if a target goal and the number of the target number (1) (2) is closer than the pulse width T 0 without integration loss into a frequency domain signal, it can be detected with the separation of these goals is there.
- the signal f ′ d, G (q ift , k) after the high accuracy processing generated by the high accuracy processing unit 64 is output to the target candidate detection unit 65. If the signal processing unit 6 does not include the high-precision processing unit 64, the target candidate detection unit 65 receives the frequency domain signal f d (n G , k) from the frequency domain conversion unit 63.
- the target candidate detection unit 65 detects a target candidate based on the intensity of the signal f'd , G ( qift , k) after the high-accuracy processing (step ST6c). For example, the target candidate detection unit 65 detects a target candidate using cell average-constant false alarm probability (CA-CFAR) processing. In the CA-CFAR processing, target candidates are detected such that the false alarm probability Pfa has a fixed specified value. For this reason, the target candidate detection unit 65 can control erroneous detection of the target candidate, so that the target candidate is not detected as much as possible, and based on the intensity of the signal after the high-accuracy processing or the signal in the frequency domain. Can be detected. In addition, since the target candidate detection unit 65 detects a target candidate based on the signal strength, it is possible to control the strength of a signal corresponding to the target candidate, and to obtain distance accuracy based on the signal strength.
- CA-CFAR cell average-constant false alarm probability
- the target candidate detecting section 65 outputs the signal f ′ d, G (q ift , k) after the high-precision processing input from the high-precision processing section 64 and the target number n tgt detected by the CA-CFAR processing. , And outputs the sampling number q ift, ntgt in the distance direction and the sampling number k ntgt in the speed direction of the signal after the high-accuracy processing to the target candidate distance calculation unit 66 corresponding to the target candidate.
- the distance-direction value and the speed-direction value of the signal obtained by the series of processing shown in FIG.
- 6A are obtained by the distance-direction sampling number q ift, ntgt of the signal after the high-precision processing and the speed-direction sampling number k ntgt . Is specified (see the relationship between the distance and the speed shown in FIG. 6A).
- the target candidate detection unit 65 determines a target based on the intensity of the frequency-domain signal f d (n G , k) generated by the frequency-domain conversion unit 63. Detect candidates.
- the target candidate detection unit 65 detects the frequency domain signal f d (n G , k) input from the frequency domain conversion unit 63 and the frequency domain signal f d (n G , k) corresponding to the target candidate with the target number n tgt detected in the CA-CFAR processing.
- the gate number n G, ntgt of the signal and the sampling number k ntgt in the speed direction are output to the target candidate distance calculation unit 66.
- the target candidate distance calculation unit 66 calculates the distance R ′ 0, ntgt of the target candidate with the target number n tgt detected by the target candidate detection unit 65 according to the following equation (27) (step ST7c).
- the distance R ′ 0, ntgt calculated by the target candidate distance calculation unit 66 is output to the display 7.
- the display 7 displays the distance R ′ 0, ntgt of the target candidate with the target number n tgt input from the target candidate distance calculation unit 66 as target information on the screen.
- the target candidate distance calculation unit 66 calculates the distance R ′ 0, ntgt of the target candidate with the target number n tgt detected by the target candidate detection unit 65 as follows. It is calculated according to equation (28). The distance R ′ 0, ntgt calculated by the target candidate distance calculation unit 66 is output to the display 7. The display 7 displays the distance R ′ 0, ntgt of the target candidate with the target number n tgt input from the target candidate distance calculation unit 66 as target information on the screen.
- the target candidate distance calculating unit 66 may calculate the speed v ′ ntgt of the target candidate with the target number n tgt according to the following equation (29).
- V ′ ntgt calculated by the target candidate distance calculation unit 66 is output to the display 7.
- the display 7 displays on the screen the speed v ′ ntgt of the target candidate with the target number n tgt input from the target candidate distance calculation unit 66 as a target candidate.
- the radar apparatus 1 radiates a transmission RF signal subjected to intra-pulse modulation to a space, and generates a reception RF signal generated based on a transmission RF signal reflected by a target in the space.
- Performs gate processing with a plurality of reception gates set on the video signal performs demodulation processing on the gated signal, performs frequency domain conversion on the demodulated signal, and performs signal processing in the frequency domain.
- the target candidate is detected, and the distance of the target candidate is calculated.
- the target distance can be accurately measured.
- the radar apparatus 1 performs the high-accuracy processing on the frequency-domain signal generated by the frequency-domain conversion unit 63, thereby generating a signal after the high-accuracy processing.
- a part 64 is provided.
- the target candidate detection unit 65 detects a target candidate based on the signal intensity after the high precision processing. Since the filter shape loss is reduced by the high accuracy processing, the target detection performance of the radar device 1 is improved, and the target separation performance is also improved.
- the radar device 1 includes a filter processing unit 62 that performs band-pass filtering on a signal after demodulation and generates a signal after band-pass filtering.
- the frequency domain transform unit 63 performs frequency domain transform on the signal after the band pass filter processing, and generates a frequency domain signal. Performing the band-pass filter processing enables sampling with a coarse sampling interval. Thus, the number of signal points is reduced and the amount of calculation in signal processing is reduced, so that the radar apparatus 1 with a small hardware scale can be realized.
- the radar device can accurately measure the target distance even when a plurality of targets exist in the reception gate, and can be used for various radar devices.
- 1 radar device 2,100 antenna, 3 transmission unit, 4 transmission / reception switching unit, 5 reception unit, 6 signal processing unit, 7,101 display, 30 transmitter, 31 intra-pulse modulator, 32 pulse modulator, 33 local unit Oscillator, 50 receiver, 51 A / D converter, 60 gate processing unit, 61 demodulation processing unit, 62 filter processing unit, 63 frequency domain conversion unit, 64 high accuracy processing unit, 65 target candidate detection unit, 66 target candidate Distance calculation unit, 102 input / output interface, 103 external storage device, 104 processing circuit, 105 signal path, 106 processor, 107 memory.
Abstract
Description
図1は、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、パルス内変調を施した送信高周波信号(以下、送信RF信号と記載する)を空間に放射し、空間内の目標で反射された送信RF信号を受信高周波信号(以下、受信RF信号と記載する)として受信し、当該受信RF信号から生成した受信ビデオ信号に基づいて、観測対象となり得る目標候補の距離を算出する。
レーダ装置1における、送信部3、受信部5、および信号処理部6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ST9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。
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に係る目標距離計測方法を示している。なお、パルス内変調には、パルス内符号変調およびパルス内周波数変調がある。以降ではパルス内符号変調を例に挙げて説明する。また、図6Aは、信号処理部6による処理の概要を示す模式図である。図6Bは、同じ速度νの複数の目標に対応する周波数領域の信号を示す図である。図6Cは、速度νの目標に対応する周波数領域の信号のゲート番号方向の波形を示す図である。図6Dは、速度νの目標に対応する逆周波数領域変換処理後の信号(高精度化処理後の信号)の距離方向の波形を示す図である。
受信部5は、空中線2によって受信された信号を受信RF信号として入力し、受信RF信号に基づいて受信ビデオ信号を生成する(ステップST2)。受信部5によって生成された受信ビデオ信号は、信号処理部6に出力される。
ゲート番号nGは、受信ゲートの位置を示す番号であり、例えば、図6Aに示すようにゲート番号nG=0,1,2,・・・,NG-1に対応するそれぞれの位置に受信ゲートが設定される。
フィルタ処理部62は、復調処理後の信号に対してフィルタ処理を行い、フィルタ処理後の信号を生成する(ステップST5)。図6Aに示すように、フィルタ処理部62は、受信ゲートごとに、復調処理後の信号に対して狭帯域フィルタ処理を行う。
例えば、高精度化処理部64は、図6Aに示すように、ゲート番号nG=0,1,2,・・・,NG-1のそれぞれの受信ゲートに対応する複数の周波数領域の信号に対して、FFT処理を行う。次に、高精度化処理部64は、FFT処理後の信号に対して、FFTの点数よりも多い点数で逆高速フーリエ変換(以下、IFFTと記載する)を行う。
高精度化処理によって距離方向のサンプリング間隔が細分化されるので、周波数領域の信号が高精度にサンプリングされる。高精度化処理後の信号の波形は、図6Dに示すように目標距離の近くで最大のピークとなる。高精度化処理部64によって生成された高精度化処理後の信号は、目標候補検出部65へ出力される。
図7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。図8は、送信RF信号Tx(t)の波形を示す図である。
局部発振器33は、下記式(1)に示す一定の周波数の局部発振信号L0(t)を生成する(ステップST1a)。局部発振器33によって生成された局部発振信号L0(t)は、受信部5およびパルス変調器32に出力される。下記式(1)において、tは時刻であり、ALは局部発振信号L0(t)の振幅であり、f0は送信周波数である。さらに、φ0は局部発振信号L0(t)の初期位相であり、Tobsは観測時間であり、jは虚数単位である。
図9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。図10は、受信ビデオ信号V(m’)の波形を示す図である。
空中の目標で反射された送信RF信号は、空中線2に入射される。空中線2に入射された信号は、下記式(6)で表される受信RF信号Rx(t)として受信機50に出力される(ステップST1b)。下記式(6)において、ntgtは目標番号であり、Ntgtは目標数である。
図11は、信号処理部6の動作を示すフローチャートであって、図5のステップST3からステップST9までの処理の詳細を示している。
信号処理部6は、受信部5が備えるA/D変換器51から受信ビデオ信号V(m’)を入力する。信号処理部6が備えるゲート処理部60は、受信ビデオ信号V(m’)に対して、予め設定されたゲートスライド量ΔmGおよびゲート幅を用いて、下記式(12)に従って、ゲート処理後の信号VG(nG,m’)を生成する(ステップST1c)。ここで、Mpriは、パルス繰り返し周期Tpri内のサンプリング数であり、Mpは、パルス内サンプリング数である。
続いて、復調処理部61は、ゲート処理部60によって生成されたゲート処理後の信号VG(nG,m’)に対して、パルス内復調Dφ(nG,m’)に基づき、下記式(13)に従った復調処理を行うことで、復調処理後の信号VG,D(nG,m’)を生成する(ステップST2c)。
一方、受信ゲートG6内にある目標番号(2)の目標の受信RF信号に対応する復調処理後の信号g2は、パルス内変調符号d2’とパルス内復調符号が一致しないため、変調符号g2’が残る。変調符号g2’が残った復調処理後の信号g2は、周波数領域の信号に変換されたときにコヒーレントに積分されない。受信ゲートG6においては、復調処理後の信号g1がコヒーレントに積分され、目標番号(1)の目標が分離可能である。
続いて、フィルタ処理部62は、復調処理後の信号VG,D(nG,m’)に対して、周波数領域の中心スペクトル周辺の帯域の信号を通過させる狭帯域フィルタ処理を行い、狭帯域フィルタ処理後の信号を生成する(ステップST3c)。狭帯域フィルタ処理後の信号VG,D,f(nG,m)は下記式(16)で表される。下記式(16)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。
続いて、高精度化処理部64は、周波数領域変換部63から入力した周波数領域の信号fd(nG,k)に対して高精度化処理を行い、高精度化処理後の信号を生成する(ステップST5c)。例えば、高精度化処理部64は、複数の受信ゲートのそれぞれに対応する周波数領域の信号fd(nG,k)に対して、下記式(23)に従うフーリエ変換処理を行うことで、周波数領域の信号fd,G(q,k)を生成する。ただし、下記式(23)において、NG,fftはフーリエ変換点数(ゲート間の周波数領域変換点数)であり、qはフーリエ変換処理後の信号のサンプリング番号である。
Claims (11)
- パルス内変調を施した送信信号を出力する送信部と、
空間内の目標で反射された前記送信信号に基づいて受信信号を生成する受信部と、
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パルス内変調に基づいて復調処理を行い、復調処理後の信号を生成する復調処理部と、
前記復調処理後の信号に対して周波数領域変換処理を行い、周波数領域の信号を生成する周波数領域変換部と、
前記周波数領域の信号の強度に基づいて目標候補を検出する目標候補検出部と、
前記目標候補検出部によって検出された目標候補の距離を算出する目標候補距離算出部と、
を備えたことを特徴するレーダ装置。 - 前記送信部は、パルス内符号変調を施した前記送信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。 - 前記送信部は、パルス内周波数変調を施した前記送信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、複数の受信ゲートのそれぞれをパルス幅よりも短い間隔で設定すること
を特徴とする請求項1記載のレーダ装置。 - 前記周波数領域変換部は、前記ゲート処理部によって設定されたそれぞれの受信ゲートにおいて同時刻に周波数領域変換処理を開始すること
を特徴とする請求項1記載のレーダ装置。 - 複数の受信ゲートに対応する複数の前記周波数領域の信号に対して周波数領域変換処理を行い、周波数領域変換処理後の信号に対して周波数領域変換点数よりも多い変換点数で逆周波数領域変換処理を行って、逆周波数領域変換処理後の信号を生成する高精度化処理部を備え、
前記目標候補検出部は、前記逆周波数領域変換処理後の信号の強度に基づいて目標候補を検出すること
を特徴とする請求項1記載のレーダ装置。 - 前記復調処理後の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フィルタ処理部を備え、
前記周波数領域変換部は、前記帯域通過フィルタ処理後の信号に対して周波数領域変換を行い、前記周波数領域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。 - 前記フィルタ処理部は、前記ゲート処理部によって設定されたそれぞれの受信ゲートにおいて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7記載のレーダ装置。 - 送信部が、パルス内変調を施した送信信号を出力するステップと、
受信部が、空間内の目標で反射された前記送信信号に基づいて受信信号を生成するステップと、
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、
復調処理部が、前記ゲート処理後の信号に対してパルス内変調に基づいて復調処理を行い、復調後の信号を生成するステップと、
周波数領域変換部が、前記復調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、
目標候補検出部が、前記周波数領域の信号の強度に基づいて目標候補を検出するステップと、
目標候補距離算出部が、前記目標候補検出部によって検出された目標候補の距離を算出するステップと、
を備えたことを特徴する目標距離計測方法。 - 高精度化処理部が、複数の受信ゲートに対応する複数の前記周波数領域の信号に対して周波数領域変換処理を行い、周波数領域変換処理後の信号に対して周波数領域変換点数よりも多い変換点数で逆周波数領域変換処理を行って、逆周波数領域変換処理後の信号を生成するステップを備え、
前記目標候補検出部が、前記逆周波数領域変換処理後の信号の強度に基づいて目標候補を検出すること
を特徴とする請求項9記載の目標距離計測方法。 - フィルタ処理部が、前記復調後の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ステップを備え、
前記周波数領域変換部が、前記帯域通過フィルタ処理後の信号に対して周波数領域変換を行い、前記周波数領域の信号を生成すること
を特徴とする請求項9または請求項10記載の目標距離計測方法。
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JP2009257884A (ja) * | 2008-04-15 | 2009-11-05 | Mitsubishi Electric Corp | レーダ装置 |
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JP2013088347A (ja) * | 2011-10-20 | 2013-05-13 | Mitsubishi Electric Corp | レーダ装置 |
WO2016194044A1 (ja) * | 2015-05-29 | 2016-12-08 | 三菱電機株式会社 | 目標検出装置および目標検出方法 |
JP2017138230A (ja) * | 2016-02-04 | 2017-08-10 | 三菱電機株式会社 | 目標検出装置 |
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JPS60263878A (ja) * | 1984-06-13 | 1985-12-27 | Mitsubishi Electric Corp | 移動目標距離判定回路 |
JP2000147100A (ja) * | 1998-11-16 | 2000-05-26 | Mitsubishi Electric Corp | パルスドップラレーダ装置 |
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