WO2019043749A1 - レーダ装置 - Google Patents
レーダ装置 Download PDFInfo
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- WO2019043749A1 WO2019043749A1 PCT/JP2017/030679 JP2017030679W WO2019043749A1 WO 2019043749 A1 WO2019043749 A1 WO 2019043749A1 JP 2017030679 W JP2017030679 W JP 2017030679W WO 2019043749 A1 WO2019043749 A1 WO 2019043749A1
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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
- G01S7/2923—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods
- G01S7/2926—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods by integration
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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
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S13/583—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
- G01S13/584—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets adapted for simultaneous range and velocity measurements
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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
- G01S13/003—Bistatic radar systems; Multistatic radar systems
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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
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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
- G01S13/282—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 using a frequency modulated carrier wave
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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
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/52—Discriminating between fixed and moving objects or between objects moving at different speeds
- G01S13/522—Discriminating between fixed and moving objects or between objects moving at different speeds using transmissions of interrupted pulse modulated waves
- G01S13/524—Discriminating between fixed and moving objects or between objects moving at different speeds using transmissions of interrupted pulse modulated waves based upon the phase or frequency shift resulting from movement of objects, with reference to the transmitted signals, e.g. coherent MTi
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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
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S13/581—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of interrupted pulse modulated waves and based upon the Doppler effect resulting from movement of targets
- G01S13/582—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of interrupted pulse modulated waves and based upon the Doppler effect resulting from movement of targets adapted for simultaneous range and velocity measurements
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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
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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
- G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
- G01S7/0232—Avoidance by frequency multiplex
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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
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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
- 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
- G01S7/282—Transmitters
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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
Definitions
- the present invention includes a plurality of transmission radars that transmit signals of transmission frequencies that are changed at predetermined intervals, and a reception radar that receives signals reflected by a target, and performs signal processing on the received signals to detect targets and measure distances. And a radar apparatus that performs speed measurement and angle measurement.
- Non-Patent Document 1 different transmission radars transmit transmission signals of transmission frequencies whose frequency is modulated in ascending order at different center frequencies and reflected at a target
- the reception radar receives the transmission signal as a reception signal. Then, on the premise that there is no influence of the target Doppler frequency, after separating received signals of different center frequencies, that is, received signals of different bands, side lobes generated due to cross-correlation of received signals of different bands are suppressed. In order to multiply and integrate (synthesize) the window function.
- Such a conventional radar device assumes that there is no influence of the target Doppler frequency, so that received signals of different center frequencies can be coherently integrated, and the distance is high resolution, and by multiplying the window function. It is possible to suppress side lobes generated by cross correlation.
- the present invention has been made to solve such a problem, and it is an object of the present invention to provide a radar apparatus capable of improving target detection performance even in the presence of the influence of a target Doppler frequency.
- the radar apparatus comprises a plurality of transmission radars that emit transmission signals of different frequencies generated using pulse signals and in-pulse modulation signals that modulate the pulse signals, and transmission signals that are reflected back from the target and returned
- a receiver for converting the received signal into a received video signal
- a distance direction frequency domain conversion unit for converting the received video signal into a signal based on the distance direction frequency, a signal based on the distance direction frequency, the change of the frequency of the transmission signal
- the hit direction frequency domain conversion unit which converts the target Doppler frequency into a signal based on the velocity and distance direction frequency so that the target Doppler frequency belongs to the same velocity bin number, and the output signal of the hit direction frequency domain conversion unit Correlation processing using a reference signal corresponding to the transmission frequency of the plurality of transmission radars and the velocity corresponding to the velocity bin number, and A correlation unit that generates a signal based on the velocity and the distance after correlation separated for each reception frequency, and an output signal of the correlation unit is integrated with the target arrival angle candidate, and
- the radar apparatus converts the received video signal into a signal based on the distance direction frequency in the distance direction frequency domain conversion unit, and in the hit direction frequency domain conversion unit, the target independently of the change in the frequency of the transmission signal.
- the Doppler frequency is converted into the hit direction frequency domain so that it belongs to the same velocity bin number, and the correlation unit generates a signal based on the velocity separated for each transmission frequency and the correlated distance.
- the integration unit generates a signal based on the band synthesized velocity and the distance after correlation, and the target candidate detection unit detects a target candidate based on the signal strength of the output signal of the integration unit.
- the target relative velocity / relative distance / arrival angle calculator calculates the relative velocity, relative distance and arrival angle of the target candidate. This makes it possible to improve the target detection performance even when there is an influence of the target Doppler frequency.
- 13A and 13B are explanatory diagrams showing a spectrum of a signal based on a received video signal and a distance frequency. It is explanatory drawing which shows the hit direction frequency domain conversion result with respect to the signal based on the distance direction frequency in the case of the target relative velocity v by FFT. It is explanatory drawing which shows the hit direction frequency domain conversion result with respect to the signal based on the distance direction frequency in the case of the target relative velocity v by CZT. It is an explanatory view showing the relation of input and output by hit direction frequency domain conversion processing. It is an explanatory view showing the relation of input and output by correlation processing.
- FIG. 20A, FIG. 20B, and FIG. 20C are explanatory diagrams showing the spectrum of the signal based on the velocity at the target relative distance of each transmission frequency and the distance after correlation.
- 21A is a comparison method
- FIG. 21B is an explanatory view showing a processing result in the case where there are a plurality of targets with different speeds in the method of the first embodiment.
- FIG. 22A is a diagram showing a ranging error of a signal based on the speed separated for each transmission frequency in the comparison system and the first embodiment and the distance after correlation
- FIG. 22A is a diagram showing a ranging error of a signal based on the speed separated for each transmission frequency in the comparison system and the first embodiment and the distance after correlation
- 22B is a diagram showing integration loss. It is explanatory drawing which shows the signal based on the speed and the distance after correlation with which the virtual image is not suppressed in case there exists speed ambiguity concerning Embodiment 1 of this invention. It is explanatory drawing which shows the signal based on the velocity (when the virtual image of a target is not suppressed) and the distance direction frequency which have speed ambiguity concerning Embodiment 1 of this invention. It is explanatory drawing which shows the relationship of the virtual image suppression degree evaluation value and threshold value at the time of changing modulation bandwidth. It is explanatory drawing which shows the signal based on the velocity (the target virtual image is suppressed) and the distance direction frequency in the case of the velocity ambiguity concerning Embodiment 1 of this invention.
- FIG. 28A is an explanatory diagram of a target and clutter in a general radar
- FIG. 28B is a diagram of the target and clutter in the first embodiment.
- It is a block diagram of the radar apparatus concerning Embodiment 2 of this invention.
- It is a block diagram of the transmission part of the radar apparatus concerning Embodiment 2 of this invention.
- It is a block diagram of the 1st signal processor of the radar apparatus concerning Embodiment 2 of this invention.
- 36C are explanatory drawings showing the influence of the Doppler frequency at the time of pulse compression when the frequency modulation of adjacent frequency bands is complex conjugate. It is explanatory drawing which shows the influence of the Doppler frequency at the time of band-combining the signal after correlation for every transmission frequency in case the frequency modulation of an adjacent frequency band is complex conjugate. It is explanatory drawing which shows the modification of the transmission frequency of a transmission radar of the radar apparatus concerning Embodiment 2 of this invention, the modulation
- FIG. 1 is a block diagram of the radar device according to the present embodiment.
- the transmission radar 100-n Tx is configured of an antenna 110-n Tx and a transmission unit 120-n Tx .
- the transmitter 120-n Tx is a transmitter 121-n Tx , a pulse modulator 122-n Tx , a local oscillator 123-n Tx , an in-pulse modulation signal generator 124-n Tx , an in-pulse modulation.
- the parameter setting unit 125-n Tx is configured of an antenna 110-n Tx and a transmission unit 120-n Tx .
- the transmitter 120-n Tx is a transmitter 121-n Tx , a pulse modulator 122-n Tx , a local oscillator 123-n Tx , an in-pulse modulation signal generator 124-n Tx , an in-pulse modulation.
- the parameter setting unit 125-n Tx is configured of an antenna 110-n Tx and a transmission unit 120-n Tx .
- the reception radar 200-1 includes an antenna 210-1, a reception unit 220-1, and a first signal processor 230-1.
- the receiver 220-1 includes a receiver 221-1 and an A / D converter 222-1.
- the first signal processor 230-1 includes a distance direction frequency domain conversion unit 231-1, a hit direction frequency domain conversion unit 232-1, a correlation unit 233-1, and an integration unit 234-1.
- the second signal processor 240 includes a target candidate detection unit 241 and a target relative speed / relative distance / arrival angle calculation unit 242.
- the transmission radar 100-n Tx is a transmission radar that emits transmission signals of different frequencies generated using a pulse signal and an in-pulse modulation signal that frequency-modulates the pulse signal.
- the antenna 110-n Tx is an antenna that radiates the signal transmitted from the transmission unit 120-n Tx as a transmission signal 130-n Tx .
- Transmitter 121-n Tx in the transmitter unit 120-n Tx is generating a transmission signal based on the pulse in the modulated signal from the pulse signal and the pulse in the modulation signal generator 124-n Tx from the pulse modulator 122-n Tx Processing unit.
- the pulse modulator 122-n Tx is a processing unit that generates a pulse signal based on the local oscillation signal from the local oscillator 123-n Tx .
- the local oscillator 123-n Tx is a processing unit that generates a local oscillation signal based on a preset period and pulse width.
- the in-pulse modulation signal generator 124-n Tx is a processing unit that generates an in-pulse modulation signal for frequency-modulating a pulse signal.
- the in-pulse modulation parameter setting unit 125-n Tx is a processing unit that sets parameters for modulating the inside of a pulse with predetermined modulation content. The setting contents of the in-pulse modulation parameter setting unit 125-n Tx are configured to be shared by the radar device.
- the reception radar 200-1 is a processing unit that receives a transmission signal emitted from the transmission radar 100-n Tx and reflected back at the target.
- An antenna 210-1 of the reception radar 200-1 is an antenna for receiving the reception signals 260-1-1 to 260-N Tx -1.
- the receiver 221-1 in the receiver 220-1 is a processing unit that converts a received signal received by the antenna 210-1 into a received video signal, and the A / D converter 222-1 receives the signal from the receiver 221-1. It is a processing unit that A / D converts the output received video signal.
- the distance direction frequency domain conversion unit 231-1 in the first signal processor 230-1 is a processing unit that converts the received video signal from the reception unit 220-1 into a signal based on the distance direction frequency.
- the hit direction frequency domain conversion unit 232-1 makes the signal based on the distance direction frequency converted by the distance direction frequency domain conversion unit 231-1 the same as the target Doppler frequency independently of the change of the frequency of the transmission signal. It is a processing unit that converts into a signal based on the velocity and distance direction frequency so as to belong to the velocity bin number.
- the correlation unit 233-1 performs correlation processing on the output signal of the hit direction frequency domain conversion unit 232-1 using the reference signal corresponding to the transmission frequency of the transmission radar 100-n Tx and the speed corresponding to the speed bin number.
- the integrating unit 234-1 is a processing unit that integrates the output signal of the correlation unit 233-1 with the target arrival angle candidate, and generates a signal based on the band synthesized velocity and the distance after correlation.
- the target candidate detection unit 241 in the second signal processor 240 is a processing unit that detects a target candidate based on the signal strength of the output signal of the integration unit 234-1.
- the target relative velocity / relative distance / arrival angle calculation unit 242 is a processing unit that calculates the relative velocity, relative distance and arrival angle of the target candidate.
- the display 250 is a display device for displaying the signal processing result.
- the radar apparatus comprises a processor 1, an input / output interface 2, a memory 3, an external storage device 4, and a signal path 5.
- the processor 1 is a processor for realizing the functions of the transmission radar 100-n Tx , the reception radar 200-1 and the second signal processor 240 in the radar apparatus.
- Output interface 2 is an interface transmitting and receiving the signal from antenna 210-1 of antenna 110-n Tx and receiver radar 200-1 in transmitted radar 100-n Tx, also at the interface of the output signal to the display unit 250 is there.
- the memory 3 is a program memory for storing various programs for realizing the radar device of the present embodiment, a work memory used when the processor 1 performs data processing, a ROM used as a memory for expanding signal data, etc. It is a storage unit such as a RAM.
- the external storage device 4 is used to store various data such as various setting data of the processor 1 and signal data.
- volatile memory such as SDRAM, HDD or SSD can be used.
- a variety of data such as programs including an operating system (OS), various setting data, and signal data can be stored.
- the data in the memory 3 can also be stored in the external storage device 4.
- the signal path 5 is a bus for interconnecting the processor 1, the input / output interface 2, the memory 3 and the external storage device 4.
- a plurality of processors 1 and memories 3 may be provided, and the plurality of processors 1 and memories 3 may be configured to perform signal processing in cooperation with each other. Furthermore, at least one of the transmission radar 100-n Tx , the reception radar 200-1 and the second signal processor 240 may be configured by dedicated hardware.
- the transmission operation of the transmission radar 100-n Tx will be described with reference to FIG.
- the antenna 110-n Tx may be dispersedly disposed, and antenna elements may be dispersedly disposed. That is, it may be realized by MIMO (multiple-input and multiple-output) radar or DBF (digital beam forming).
- the local oscillator 123-n Tx generates a local oscillation signal L 0 (t) as shown in equation (1) and outputs it to the pulse modulator 122-n Tx (Step ST11).
- a L is the amplitude of the local oscillation signal
- ⁇ 0 is the initial phase of the local oscillation signal
- f 0 is the central transmission frequency
- T obs is the observation time.
- the pulse modulator 122-n Tx based on the pulse repetition information indicating the period T pri and the pulse width T 0 set in advance, from equation (2), the local oscillation signal L 0 from the local oscillator 123-n Tx Pulse modulation is performed on (t) to generate a pulse signal L pls (h, t), which is output to the transmitter 121-n Tx (step ST12).
- h is the hit number
- H is the number of hits (represented by equation (3)
- floor (X) is an integer obtained by rounding off the decimal part of the variable X).
- the in-pulse modulation parameter setting unit 125-n Tx sets a predetermined frequency modulation amount B nTx and a modulation bandwidth ⁇ B nTx .
- the in-pulse modulation parameter setting unit 125-n Tx outputs the in-pulse modulation parameter to the in-pulse modulation signal generator 124-n Tx .
- the intra-pulse modulation signal generator 124-n Tx uses the frequency modulation amount B nTx and the modulation bandwidth ⁇ B nTx output from the intra-pulse modulation parameter setting unit 125-n Tx according to the equation (4) to generate a pulse signal.
- FIG. 5 shows the relationship between the frequency modulation amount B nTx of each transmission radar and the modulation bandwidth ⁇ B nTx . In the first embodiment, an effect when the modulation bandwidths of the transmission radars are the same will be described.
- the frequency modulation amount B 2 is zero.
- the transmitter 121-n Tx uses the pulse signal L pls (h, t) and the in-pulse modulation signal L chp (n Tx , h, t) according to the equation (5) to transmit the transmission signal T x (n Tx , h , T) are generated and output to the antenna 110-n Tx (step ST14). After that, the transmission signal T x (n Tx , h, t) is emitted to the air from the antenna 110-n Tx (step ST15).
- the transmission signal radiated into the air is reflected by the target and is incident on the antenna 210-1 as a reflection signal. Therefore, the antenna 210-1 receives the reflected signal that has been incident, and outputs it to the receiver 221-1 as the reception signal Rx (n Rx , h, t) of the reception radar 200-n Rx represented by the equation (6).
- Rx 0 (n Tx, n Rx, h, t) is the received signal received by the receiving radar 200-n Rx reflected signal of the transmitted radar 100-n Tx of the formula (7)
- a R is The amplitude of the reflected signal
- R 0 is the target initial relative distance
- v is the target relative velocity
- ⁇ is the target angle
- c is the speed of light
- t ′ is the time within one hit.
- phase difference ⁇ Tx (n Tx ) of the transmission radar 100-n Tx is expressed by equation (8)
- the phase difference ⁇ Rx (n Tx , n Rx ) of the reception radar 200-1 is expressed by equation (9) expressed.
- the receiver 221-1 uses the local oscillation signal L 0 (t) represented by the equation (1) for the reception signal Rx (n Tx , n Rx , h, t) input from the antenna 210-1. Down-convert and pass through a band-pass filter (not shown), then amplify and perform phase detection, and the received video signal V '(n Rx , h, t) of the receiving radar 200-n Rx expressed by equation (10) It is generated and output to the A / D converter 222-1 (step ST22).
- V 0 ′ (n Tx , n Rx , h, t) is a reception video signal generated by the reception radar 200-n Rx, which is the reception video signal of the transmission radar 100-n Tx represented by equation (11)
- AV is the amplitude of the received video signal.
- the A / D converter 222-1 performs A / D conversion on the reception video signal V ′ (n Rx , h, t) of the reception radar 200-n Rx input from the receiver 221-1,
- the reception video signal V (n Rx , h, m) of the reception radar 200-n Rx represented by the equation (12) is generated and output to the first signal processor 230-1 (step ST 23).
- V 0 (n Tx , n Rx , h, m) is a received video signal obtained by A / D converting the received video signal of the transmitting radar 100-n Tx expressed by the equation (13) by the receiving radar 200-n Rx
- a signal m is a sampling number in PRI (pulse repetition period)
- M in PRI is a sampling number.
- step ST31 is processing of distance direction frequency domain conversion unit 231-1
- step ST32 is processing of hit direction frequency domain conversion unit 232-1
- step ST33 is processing of correlation unit 233-1
- step ST34 shows the processing of the integration unit 234-1. That is, in step ST31, the distance direction frequency domain conversion unit 231-1 converts the received video signal into the distance direction frequency domain by converting the received video signal in the distance direction into the distance direction frequency domain, and generates a signal based on the distance direction frequency.
- the hit direction frequency domain conversion unit 232-1 converts the signal based on the distance direction frequency into the frequency domain according to the transmission frequency and modulation range of each transmission radar, and generates a signal based on the speed and the distance direction frequency.
- the correlation unit 233-1 performs correlation processing on the signal based on the velocity and distance direction frequency using the reference signal, and the velocity separated for each transmission frequency of each transmission radar and the distance after correlation Generate a signal based on.
- the integrating unit 234-1 integrates the signal based on the velocity separated for each transmission frequency and the distance after correlation, and generates a signal based on the velocity combined for band and the distance after correlation.
- the reception video signal V (n Rx , h, m) of the reception radar 200-n Rx is input to the distance direction frequency domain conversion unit 231-1 from the A / D converter 222-1.
- the reception video signal V (n Rx , h, m) of the reception radar 200-n Rx is a signal in which a plurality of transmission radars are modulated at different center frequencies as shown in equation (12).
- the first signal processor 230-1 can improve detection performance by separating the received signals transmitted by a plurality of transmission radars, reflected from the target, and received by each transmission radar and coherently integrating them. Do.
- FIG. 9A, FIG. 9B, and FIG. 9C show signals after correlation for each transmission radar when there is no influence of the Doppler frequency.
- 9A shows a transmission radar 100-1
- FIG. 9B shows a transmission radar 100-2
- FIG. 9C shows a signal after correlation of the transmission radar 100-3.
- FIGS. 9A to 9C since the band is different for each transmission radar, the reception signal for each transmission radar can be separated. It can be seen that the target relative distance is integrated.
- cross-correlation occurs due to the influence of adjacent bands, and the side lobes rise slightly (see section 901 in the figure).
- FIG. 9D, FIG. 9E, and FIG. 9F show signals after correlation for each transmission radar when there is an influence of Doppler frequency.
- FIG. 9D shows a signal after correlation of transmission radar 100-1
- FIG. 9E shows transmission radar 100-2
- FIG. 9F shows a correlation signal of transmission radar 100-3.
- the reception signal for each transmission radar can be separated.
- the target relative distance is affected by the influence of the Doppler frequency, and is compressed to a distance ⁇ R PC (n Tx ) different from the target relative distance as represented by equation (14), so that the distance measurement performance is deteriorated. is there.
- FIG. 10 shows the effect of Doppler frequency in the case of band combination.
- FIG. 10A when there is no influence of the Doppler frequency, signals in adjacent bands are coherently combined, power is increased, detection performance is improved, and distance resolution is improved (see section 1001 in the drawing).
- FIG. 10B when there is the influence of the Doppler frequency, there is a problem that the phases of the signals after correlation of adjacent bands are different and integration loss occurs (see arrow 1002 in the drawing).
- the distance to be compressed is different from the target relative distance (see the arrow 1003 in the figure).
- a section 1005 indicates a portion where the side lobe is rising due to the cross correlation.
- FIG. 11 is a flowchart showing the operation of each processing unit in the first signal processor 230-1.
- Distance direction frequency domain conversion unit 231-1 the received video signal V of the received radar 200-n Rx (n Rx, h, m) to get (step ST41), the received video signal V (n Rx, h, Fast Fourier transform (FFT) is performed on m) according to equation (17) to generate a signal F v (n Rx , h, k r ) based on the frequency in the distance direction (step ST 42).
- FFT Fast Fourier transform
- f samp is the sampling frequency
- M fft is the number of FFT points in the distance direction
- k r is the sampling number of the frequency in the distance direction.
- Distance direction distance after converted into the frequency domain direction frequency bin number k r of the distance direction frequency f r, samp (k r) is represented by the formula (18)
- the distance direction the frequency domain sampling interval Delta] f samp is the formula (19) Is represented by
- the distance direction frequency domain conversion unit 231-1 outputs the signal F V (n Rx , h, k r ) based on the distance direction frequency to the hit direction frequency domain conversion unit 232-1.
- FIG. 12 shows the relationship between input and output in distance direction frequency domain conversion processing.
- FIG. 13 shows the spectrum of the received video signal V (n Rx , h, m) and the signal F V (n Rx , h, kr ) based on the distance direction frequency.
- FIG. 13A represents the received video signal
- FIG. 13B represents the signal based on the distance frequency.
- the value of the distance indicated by the dotted line is the target initial relative distance R 0 and the distance R amb that can be measured without ambiguity.
- FIG. 13B is a sampling frequency.
- FIG. 13A illustrates that the distance received for each hit has changed by vT pri / 2.
- FIG. 13B it is explained that the Doppler frequency corresponding to the target relative velocity v is changed in all hits. Since the distance direction frequency domain conversion unit 231-1 generates the signal F V (n Rx , h, k r ) based on the distance direction frequency, it is possible to separate each frequency band of the transmission frequency of the transmission radar by the distance direction frequency Become.
- Equation (17) the term related to the frequency domain conversion of the signal F V (n Rx , h, kr ) based on the distance direction frequency in the hit direction is equation (20).
- Relative term of formula (20) by converting in accordance with equation (21) to the hit direction to the frequency domain, the distance direction frequency bins based on the hit direction Doppler frequency for each number k r signal F fft (h fft , K r ) are generated.
- the Doppler frequency bin h fft, peak (k r ) where the signal F fft (h fft , k r ) based on the hit direction Doppler frequency for each distance direction frequency bin number k r indicates an absolute value is As shown in 22), there is a problem that integration loss occurs because it changes according to the distance direction frequency bin.
- H fft is the hit direction FFT score
- h fft is the sampling number in the hit direction Doppler frequency domain.
- a section 1401 corresponds to the transmission radar 100-1 after the hit direction FFT of the signal F v (n Rv , h, k r ) based on the distance direction of the reception radar 200-n Rx in the case of the target relative velocity v.
- a corresponding portion is shown, a section 1402 shows a portion corresponding to the same transmission radar 100-2, and a section 1403 shows a portion corresponding to the transmission radar 100-3.
- ⁇ f FFT in the figure is the frequency sample interval in the hit direction frequency domain
- f prf is the pulse repetition frequency
- f r, st (n Tx , v) is the minimum of the transmission radar 100-n Tx at the target relative velocity v
- Distance direction frequency f r, en (n Tx , v) is the maximum distance direction frequency of the transmitting radar 100-n Tx at the target relative velocity v
- f d, st (n Tx , v) is the target relative velocity
- the minimum Doppler frequency of the transmission radar 100-n Tx in the case of v, f d, en (n Tx , v) is the maximum Doppler frequency of the transmission radar 100-n Tx in the case of the target relative velocity v.
- FIG. 14 when the target relative velocity v is unknown, it is difficult to generate a suitable reference signal without loss of pulse compression on the signal based on the distance frequency and the Doppler frequency. The Similar problems occur with
- the hit direction frequency domain conversion unit 232-1 is intended to perform pulse compression and coherent band synthesis without loss of the signal F V (n Rx , h, k r ) based on the distance direction frequency of the reception radar 200-n Rx. It is provided. Therefore, in the hit direction frequency domain conversion unit 232-1, the Doppler frequency interval is set for each distance direction frequency bin so that the Doppler velocity bin is the same for each different transmission frequency and modulation band, that is, for each distance direction frequency bin.
- the Chirp Z-Transform (CZT) is used to transform to the hit direction frequency domain while changing.
- FIG. 15 shows signals based on velocity and distance direction frequency which are the result of frequency domain conversion in the hit direction for signals based on distance direction frequency of the transmission radar 100-n Tx by CZT.
- ⁇ v CZT is the velocity sample interval in the hit direction frequency domain.
- FIG. 15 shows an example of frequency conversion of the hit direction so that the signal based on the distance direction frequency of the transmission radar 100-n Rx becomes the speed bin indicating the target relative velocity v, the transmission radar 100-1 having different overlapping bands, The signals of the transmission radar 100-2 and the transmission radar 100-3 are converted to the hit direction frequency in the same velocity bin.
- FIG. 15 shows signals based on velocity and distance direction frequency which are the result of frequency domain conversion in the hit direction for signals based on distance direction frequency of the transmission radar 100-n Tx by CZT.
- ⁇ v CZT is the velocity sample interval in the hit direction frequency domain.
- FIG. 15 shows an example of frequency conversion of the hit direction so that the signal based on the distance direction frequency of the transmission radar 100-
- a section 1501 is a portion corresponding to the transmission radar 100-1 of the signal F CZT (n R , h, k r ) based on the speed and distance direction of the reception radar 200-n Rx in the case of the target relative speed v.
- a section 1502 shows a portion corresponding to the same transmission radar 100-2, and a section 1503 shows a portion corresponding to the transmission radar 100-3.
- the hit direction frequency domain conversion unit 232-1 operates to change the CZT conversion function based on the distance direction frequency so that the Doppler velocity bins of the signal after the hit direction frequency domain conversion become the same.
- the hit direction frequency domain conversion unit 232-1 performs the CZT expressed by equation (24) on the signal F V (n Rx , h, k r ) based on the distance direction frequency of the reception radar 200-n Rx. converting the hit direction frequency domain by the signal F CZT based on speed and distance direction frequency (n Rx, h czt, k r) to generate (step ST43 in FIG. 11).
- z kr -h is a CZT conversion function corresponding to each distance direction frequency f r, samp (k r ), and A kr is a conversion start phase corresponding to each distance direction frequency f r, samp (k r ) Equation (25), W kr -hczt is the CZT conversion range function (Equation (26)) corresponding to each distance direction frequency f r, samp (k r ), v st is the conversion start speed, and v en is the conversion end
- the velocity, H czt is the sampling number after CZT.
- the relative velocity v CZT (h czt ) of the velocity bin number h czt after conversion to the hit direction frequency domain is expressed by equation (27).
- the velocity sampling interval ⁇ v czt in the hit direction frequency domain is expressed by equation (28).
- Equation (20) related to the hit direction frequency domain conversion of signal F V (n Rx , h, k r ) based on the distance direction frequency
- the hit direction using equations (24) to (26) The result of performing frequency domain conversion, that is, CZT is expressed by equation (29).
- Signal based on the speed and distance direction frequency F CZT (n Rx, h czt , k r) of the absolute value of the speed bin h czt showing the maximum value, peak is represented by the formula (30).
- the transmission frequency (f 0 + fr , samp (k r )) is obtained from the equations (29) and (30) by the processing of the hit direction frequency domain conversion unit 232-1 according to the equations (24) to (26).
- speed and distance based on the direction the frequency signal F CZT (n Rx, h czt , k r) is the same speed sampling interval conversion end speed v en from the conversion starting speed v st hit direction frequency direction Sampled at ⁇ v czt , targets are sampled to the same Doppler velocity bin.
- the sampling number H czt after CZT can be set arbitrarily, and it becomes possible to set a desired sampling interval.
- the conversion start speed v st and the conversion end speed v en it is possible to arbitrarily set the assumed relative speed. That is, regardless of the unambiguously measurable velocity v amb defined by the pulse repetition period T pri represented by the equation (31), it is possible to set as the equation (32). Therefore, it is possible to calculate the target in the desired speed range at once without the need to calculate for each range of the speed v amb that can be measured without ambiguity, and it is possible to reduce the amount of calculation and speed up.
- the hit direction frequency domain transform unit 232-1 uses the fast Fourier transform (FFT) represented by the equation (33) and the fast Fourier inverse transform (IFFT: Inverse FFT) represented by the equation (24).
- FFT fast Fourier transform
- IFFT Inverse FFT
- DFT Discrete Fourier Transform
- FIG. 16 shows the input / output relationship in the hit direction frequency domain conversion process.
- the signals based on the distance direction frequency have different Doppler frequencies according to the distance direction frequency, but as shown in FIG. 15, the hit direction frequency region of the hit direction frequency domain conversion unit 232-1 It is explained that the conversion appears in the target relative velocity bin.
- the formula (34 ) in accordance performs window function processing, the signal based on the distance direction frequency after the window function processing F V '(n Rx, h , to produce a k r).
- the Hamming window wham (h) represented by the equation (35) is described.
- a window function other than the Hamming window may be used.
- the hit direction frequency domain conversion unit 232-1 is based on the distance direction frequency after window function processing instead of the signal F V (n Rx , h, k r ) based on the distance direction frequency.
- the signal F V '(n Rx , h, k r ) is substituted and converted to the hit direction frequency domain according to the equation (24) or (33), and the signal F CZT (n Rx , h based on the velocity and distance direction frequency) czt, to generate a k r).
- Hit direction frequency domain conversion unit 232-1 the signal based on the speed and distance direction frequency F CZT (n Rx, h czt , k r) is output to correlator 233-1.
- a Doppler frequency that is, in the case of a moving target, there is a problem that the moving distance during the observation time becomes equal to or greater than the distance resolution, and the integral loss is degraded.
- the distance direction frequency domain conversion unit 231-1 is provided before the hit direction frequency domain conversion processing, the distance direction frequency bins are unified among the hits, and the influence of the movement distance during the observation time is Instead, it becomes possible to perform hit direction frequency domain conversion processing as coherent integration without integration loss.
- Correlator 233-1 a reference signal based on the speed corresponding to the transmission frequency and the speed bin, the signal based on the speed and distance direction frequency F CZT (n Rx, h czt , k r) correlation, i.e. pulse compression
- R PC n Tx , n Rx , h czt , k pc
- signals F CZT (n Rx , h czt , k r ) based on the velocity and distance direction frequency of correlation unit 233-1 correspond to the transmission frequency and each velocity bin of each transmission radar.
- the correlation processing in the frequency domain with the reference signal Ex (n Tx , h czt , m) based on velocity, that is, pulse compression will be described.
- process block 1701-1 the signal F CZT based on speed and distance direction the frequency of the received radar 200-n Rx (n Rx, h czt, k r) and the transmission frequency and the rate of transmitted radar 100-1
- the correlation processing pulse compression processing with the reference signal Ex (1, h czt , m) based on the velocity corresponding to the bin number h czt is shown.
- the processing block 1701-N is the signal based on the speed and distance direction the frequency of the received radar 200-n Rx F CZT (n Rx, h czt, k r) and transmitting the radar N Tx transmit frequency and each speed bin number h of
- the correlation processing pulse compression processing
- FIG. 18 shows a signal based on the velocity and the distance after correlation, and the value of the distance shown by a dotted line is the distance Ramb which can be measured without ambiguity.
- the received signal is a signal including a modulation component and a Doppler frequency component, but is compressed because the reference signal is a signal of only the modulation component.
- Problems such as distance shift and low correlation occur.
- the solid line indicates the transmission signals of the transmission radars 100-1 to 100-3, and the broken line indicates the reception signals affected by the Doppler frequency.
- the cross correlation with the adjacent band becomes high, the unnecessary peak becomes high as shown by the curve 1004 in FIG. 10B, and the distance is deviated as shown by the arrow 1003 and the equation (14).
- the correlation unit 233-1 performs the same frequency modulation amount B nTx and modulation bandwidth ⁇ B nTx of each transmission radar 100-n Tx as the in-pulse modulation signal L chp (n Tx , h, t).
- the reference signal Ex (n Tx , h czt , m) including the Doppler frequency corresponding to the velocity of each velocity bin is generated according to equation (36).
- the second term in the equation (36) represents the Doppler frequency corresponding to the velocity of each velocity bin, and is converted to the frequency domain in the hit direction by the hit direction frequency domain conversion unit 232-1 before pulse compression. .
- the signal integrated in the target relative velocity bin can be pulse compressed without the influence of the Doppler frequency, integrated to the target initial relative distance regardless of the stationary target and the moving target, and the distance measurement performance can be improved.
- the reference signal for each transmission frequency and for each speed corresponding to the speed bin is generated, the reception video signal from the target for each speed at each transmission frequency is affected by the Doppler frequency It is possible to perform pulse compression without noise. Since the distance direction frequency domain conversion unit 231-1 provided in front of the hit direction frequency domain conversion unit 232-1 converts the distance direction into the frequency domain, the signals based on the distance direction frequency have the same distance direction frequency bin among hits.
- the correlation unit 233-1 does not need to perform distance direction frequency domain conversion for each transmission radar n Tx , and obtains an effect that the amount of calculation is reduced. That is, the amount of calculation is reduced to 1 / N Tx as compared with the case where distance direction frequency domain conversion is performed for each transmission radar n Tx .
- the calculation amount reduction effect increases as the number of transmission radars N Tx increases.
- the correlation unit 233-1 performs fast Fourier transform (FFT) on the reference signal Ex (n Tx , h czt , m) according to equation (37), and then a signal F CZT (n It multiplies by Rx , h czt , k r ) (equation (38)).
- FFT fast Fourier transform
- * represents a complex conjugate.
- the correlation unit 233-1 performs inverse fast Fourier transform (IFFT) on the multiplication result F V ⁇ Ex (n Tx , n Rx , h czt , k r ) according to equation (39).
- IFFT inverse fast Fourier transform
- a signal R PC (n Tx , n Rx , h czt , k pc ) based on the velocity separated for each transmission frequency and the distance after correlation is generated (step ST45 in FIG. 11).
- the received signal corresponding to the reference signal corresponding to the transmitted radar 100-n Tx is pulsed compressed, transmitted radar 100-n Tx and bandwidth are different, the received signals of the other transmitted radar small correlation , And can be separated for each transmission frequency.
- signals 2001, 2002, and 2003 only the reception signal corresponding to the transmission radar 100-n Tx is separated and pulse-compressed without loss.
- FIG. 21 shows the processing result in the case where there are a plurality of targets having different speeds.
- FIG. 21A shows the case where the received video signal is compensated at the relative velocity v (1) of target 1, pulse compression is performed, and pulse compression is followed by hit direction frequency domain conversion processing (comparison system, general radar device
- FIG. 21B shows a signal based on the speed separated for each transmission frequency and the distance after correlation according to the first embodiment.
- target 1 is compensated with the relative velocity of target 1, it is integrated without loss in the initial relative distance of target 1, but integrated loss occurs in target 2 and a distance different from the initial relative distance It can be seen that the On the other hand, as shown in FIG.
- 22A and 22B are diagrams showing ranging error and integral loss of a signal based on the speed separated for each transmission frequency and the distance after correlation in the comparison system and the first embodiment.
- the alternate long and short dash line indicates the comparison method
- the solid line indicates the method of the first embodiment.
- the received signal from a target end speed v en the start velocity v st, integrating loss, the effect of ranging error is reduced.
- the correlation unit 233-1 outputs a signal R PC (n Tx , n Rx , h czt , k pc ) based on the velocity separated for each transmission frequency and the distance after correlation to the integration unit 234-1.
- the integrating unit 234-1 generates an equation for the signal R PC (n Tx , n Rx , h czt , k pc ) based on the velocity separated for each transmission frequency acquired from the correlation unit 233-1 and the distance after correlation. It performs integration in accordance with (40), band synthesized speed signal is based on the distance after correlation R ⁇ Tx (n ⁇ , n Rx , h czt, k pc) to generate (step ST46 in FIG. 11).
- ⁇ ′ (n ⁇ ) is the arrival angle candidate represented by equation (41)
- n ⁇ is the arrival angle candidate number
- N ⁇ is the number of arrival angle candidates
- ⁇ samp is the assumed target angle interval.
- the signal R PC (n Tx , n Rx , h czt , k pc ) based on the velocity separated for each transmission frequency and the distance after correlation is coherently integrated and band synthesized speed signal based on the distance after correlation R ⁇ Tx (n ⁇ , n Rx , h czt, k pc) indicates the maximum value.
- the integrator 234-1 transmits the signal R TxTx (n ⁇ , n Rx , h czt , k pc ) based on the band synthesized velocity and the correlated distance to the target candidate detector 241 in the second signal processor 240. Output.
- Target candidate detecting section 241 the signal based on the distance after correlation with band synthesis velocity obtained from the integration unit 234-1 R ⁇ Tx (n ⁇ , n Rx, h czt, k pc) relative to the signal strength Based on the target candidate is detected. More specifically, for example, CA-CFAR (Cell Average Constant False Alarm Rate) processing can be considered.
- CA-CFAR Cell Average Constant False Alarm Rate
- Target candidate detecting section 241 the signal based on the distance after correlation with band synthesis velocity R ⁇ Tx (n ⁇ , n Rx , h czt, k pc) and the arrival angle candidate number of the detected target candidates n theta ',
- the velocity bin number h czt ′ and the sampling number k pc ′ in the distance direction are output to the target relative velocity / relative distance / arrival angle calculation unit 242.
- the target with the true target relative velocity v is integrated without any loss into the true target initial relative distance R 0 without loss regardless of the measurable velocity v amb , but when suppressing the virtual image, the in-pulse modulation parameter setting unit 125 -N Tx has a function of calculating and setting an in-pulse modulation parameter for suppressing signals with different speed ambiguities based on the virtual image suppression degree evaluation value and a predetermined threshold value.
- the in-pulse modulation parameter setting unit 125-n Tx having this function is referred to as an in-pulse modulation parameter setting unit 125-n Tx B, and will be described below.
- the in-pulse modulation parameter setting unit 125-n Tx B performs in-pulse modulation parameters so that the virtual image suppression degree evaluation value L v, amb (n v, amb ) and the threshold L ' v, amb satisfy the condition of equation (43) Calculate and set.
- the in-pulse modulation parameter setting unit 125-n Tx B calculates the virtual image suppression degree evaluation value L v, amb (n v, amb ) according to Expression (44) using the in-pulse modulation parameter.
- the numerator in equation (44) is a signal R Tx Tx (n ⁇ , n Rx , h based on the band synthesized velocity and the correlated distance in the case of the velocity return number n v, amb with respect to the true target relative velocity v
- the denominator of equation (44) is the signal R Tx Tx (n ⁇ , n Rx) based on the band synthesized velocity and the correlated distance in the case of the true target relative velocity v , H czt , k pc ) (the theoretical value of the integration result).
- k r, st is the integration start bin of the distance frequency
- k r, en is the integration end bin of the distance frequency
- sinc (X) is a sinc function of the variable X
- ⁇ f d, v, amb (n v, n shown amb, k r) is the distance direction frequency bin number k r, velocity folding number n v, signal based on the speed and distance direction frequency during amb
- F CZT (n Rx, h czt, the absolute value of k r) is the maximum
- the difference from the Doppler frequency (Equation (45)), ⁇ f d, resol is the Doppler frequency resolution (Equation (46)). As shown in FIG.
- the in-pulse modulation parameter setting unit 125-n Tx B operates to calculate and set the in-pulse modulation parameter so that the virtual image is not integrated, that is, suppressed.
- Section 2401 represents a portion corresponding to transmission radar 100-1 of signal F CZT (n R , h, k r ) based on the velocity and distance direction of reception radar 200-n Rx at target relative velocity v
- a section 2402 shows a portion corresponding to the same transmission radar 100-2
- a section 2403 shows a portion corresponding to the transmission radar 100-3.
- the intra-pulse modulation parameter setting unit 125-n Tx B calculates the virtual image suppression degree evaluation value L v, amb (n v, amb ) and the threshold L ' v, amb based on the equations (44) to (46). Calculate the modulation bandwidth ⁇ B nTx of the in-pulse modulation parameter that satisfies the conditions of 43), the pulse repetition period T pri involved in the unambiguously measured velocity v amb , and the observation time T obs involved in the Doppler frequency resolution ⁇ f d, resol . For example, as shown in FIG.
- the intra-pulse modulation parameter setting unit 125-n Tx B evaluates the virtual image suppression degree evaluation value L v, amb (n v, amb ) and the threshold L 'when the modulation bandwidth is changed.
- v by utilizing the relationship amb, set desired threshold L or more L 'v, modulation bandwidth ⁇ B meet amb'.
- a section 2601 corresponds to the transmission radar 100-1 of the signal F CZT (n R , h, k r ) based on the speed and distance direction of the reception radar 200-n Rx in the case of the target relative speed v.
- a portion is shown, a section 2602 shows a portion corresponding to the same transmission radar 100-2, and a section 2603 shows a portion corresponding to the transmission radar 100-3.
- the SNR tgt which is the SNR (Signal to Noise Ratio) of the target after processing, and the processing of the target virtual image (velocity ambiguous number 1)
- SNR tgt, v, amb which is the SNR of
- equation (47) the SNR of the target virtual image (velocity ambiguity number 1) represented by equation (49)
- SNR tgt which is the target SNR represented by equation (48)
- SNR in is the SNR of the received video signal
- SNR ci imp is the SNR improvement by the hit direction frequency domain conversion
- SNR pc imp is the SNR improvement by pulse compression
- SNR Tx imp is the SNR improvement by band combining
- M p is the number of received pulse samples.
- the in-pulse modulation parameter setting unit 125-n Tx B can suppress a virtual image using a desired velocity fuzzy number and in-pulse modulation parameter, it is assumed that clutters having different velocity ambiguity numbers are used; By calculating and setting parameters, it becomes possible to suppress the influence of clutter. As shown in FIG. 28A, the target and clutter can not be separated by a general radar and detection is difficult. However, as shown in FIG. 28B, Embodiment 1 using the in-pulse modulation parameter setting unit 125-n Tx B In the in-pulse modulation parameter setting unit 125-n Tx B, the in-pulse modulation parameter is calculated and set so as to suppress clutters having different velocity ambiguities (see arrow 2801).
- n clt, v, amb is the velocity ambiguity number of clutter.
- the in-pulse modulation parameter setting unit 125-n Tx B outputs the in-pulse modulation parameter to the in-pulse modulation signal generator 124-n Tx .
- Target relative speed and the relative distance and angle of arrival calculator 242 the obtained arrival angle candidate number n theta target candidate ', velocity bin number h czt' based on the distance direction of the sampling number k pc ', according to equation (52) target candidate arrival angle theta 'the tgt, also target candidates relative speed v according to equation (53)' the tgt, further calculates a target candidate relative distance R 'tgt according to equation (54).
- ⁇ r IFFT is a sampling interval in the distance direction after correlation.
- the target relative velocity / relative distance / arrival angle calculator 242 displays a target candidate arrival angle ⁇ ′ tgt , a target candidate relative velocity v ′ tgt , and a target candidate relative distance R ′ tgt corresponding to the arrival angle candidate number n ⁇ ′. Output to 250.
- the display 250 displays the target candidate arrival angle ⁇ ′ tgt , the target candidate relative velocity v ′ tgt , and the target candidate relative distance R ′ tgt as target information on the screen as the signal processing result.
- a plurality of transmission radars transmit different transmission frequencies, and the reception radar reflected and received by the target receives the reception video signal of the different transmission frequencies without the influence of the Doppler frequency.
- distance direction frequency domain conversion section 231-1 performs distance direction frequency domain conversion on the received video signal to generate a signal based on distance direction frequency.
- the signals based on the distance direction frequency generated by the distance direction frequency domain conversion unit 231-1 are unified into the same distance direction frequency bin among the hits, and it becomes possible to integrate in the hit direction without integration loss, and the target for the movement target It becomes possible to obtain a radar device with improved detection performance.
- the correlation unit 233-1 correlates with the reference signal in the distance direction frequency domain
- the distance direction frequency domain transform unit 231-1 since the distance direction frequency domain transform unit 231-1 generates a signal based on the distance direction frequency, the distance direction frequency for each transmission radar It is not necessary to perform area conversion, and it is possible to obtain a similar radar apparatus with the same effect while reducing the amount of calculation.
- the hit direction frequency domain conversion unit 232-1 changes the Doppler frequency for each of the different transmission frequencies and distance direction frequency bins so that the Doppler speed bins become the same for each of the different transmission frequencies and modulation bands, that is, for each distance direction frequency bin. Convert to the hit direction frequency domain by Chirp z conversion while changing the interval.
- the conversion process to the hit direction frequency domain may be discrete Fourier transform. Since the hit direction frequency domain conversion unit 232-1 converts the target relative speed into the hit direction frequency domain so that the Doppler speed bins become the same for each different transmission frequency and modulation band, that is, for each distance direction frequency bin. It is not necessary to detect and calculate, and it is possible to obtain a radar apparatus in which the target detection performance of low SNR is improved without the influence of the modulation band changing the Doppler frequency.
- the correlation unit 233-1 is configured to receive the reference signal Ex (n Tx , h czt , m) based on each transmission frequency and each speed bin, and the signal F CZT (n Tx , n Rx based on the speed and distance direction frequency). , H czt , k r ), that is, pulse compression is performed to generate a signal R PC (n Tx , n Rx , h czt , k pc ) based on the velocity separated for each transmission frequency and the distance after correlation .
- the correlation unit 233-1 performs pulse compression using the reference signal Ex (n Tx , h czt , m) based on each transmission frequency and each velocity bin, pulse compression can be performed without the influence of Doppler frequency. Become. As a result, the stationary target and the moving target are both pulse-compressed to the target initial relative distance to improve the distance measurement performance, and a radar device capable of suppressing an increase in the unnecessary peak even for a received signal having a Doppler frequency. It is possible to get In addition, it is possible to obtain a radar device with improved detection performance.
- Integrator 234-1 integrated over signal R PC based on the distance after correlation with rate which is separated for each transmission frequency input from the correlation unit 233-1 (n Tx, n Rx, h czt, k pc) was carried out, the signal based on the distance after correlation with band synthesis velocity R ⁇ Tx (n ⁇ , n Rx , h czt, k pc) for generating a. That is, although the received video signal of different transmission frequency is integrated, when the transmission frequency is different, the Doppler frequency is also different, and as a result, the reception video signal of different transmission frequency is not coherent and out of phase, and integration loss occurs. There is.
- the correlation unit 233-1 becomes coherent because it uses the reference signal Ex (n Tx , h czt , m) based on each transmission frequency and the velocity corresponding to each velocity bin. It will be possible. Therefore, after integration, it is possible to obtain a radar device with increased power and improved detection performance.
- a plurality of transmission radars that emit transmission signals of different frequencies generated using the pulse signal and the in-pulse modulation signal that modulates the pulse signal
- a receiver for converting the received signal of the transmission signal reflected back at the target into a received video signal
- a distance direction frequency domain converter for converting the received video signal into a signal based on the distance direction frequency
- a distance direction frequency A hit direction frequency domain conversion unit that converts the signal into a signal based on the velocity and distance direction frequency so that the target Doppler frequency belongs to the same velocity bin number independently of changes in the frequency of the transmission signal
- a correlation unit that generates a signal based on the velocity separated for each transmission frequency of the plurality of transmission radars and the distance after correlation, and an output signal of the correlation unit is integrated with the target arrival angle candidate
- the plurality of transmission radars calculate and set the in-pulse modulation parameter for suppressing the signals having different speed ambiguous numbers based on the virtual image suppression degree evaluation value and the set threshold. Since the in-pulse modulation parameter setting unit is provided, it is possible to obtain a radar device in which the virtual image is suppressed, the detection performance in which the false alarm is suppressed, and the target speed measurement performance higher than the measurable speed without ambiguity. . In addition, it is possible to set the in-pulse modulation parameter so as to suppress clutters different in velocity ambiguity number, and it becomes possible to obtain a radar device with improved detection performance without the influence of clutter.
- the plurality of transmission radars modulate the frequency of the pulse signal, so that the target detection performance can be improved even when the target Doppler frequency has an influence.
- the plurality of transmission radars transmit transmission signals of different frequencies based on the transmission frequency frequency-modulated in the pulse in ascending or descending order at set frequency intervals.
- the plurality of transmission radars transmit transmission signals of different frequencies based on the transmission frequency frequency-modulated in the pulse in ascending or descending order at set frequency intervals.
- the hit direction frequency domain conversion unit performs the conversion process by applying window function processing to the signal based on the distance direction frequency, so that the hit direction frequency domain conversion is performed. Lateral side lobes in the velocity direction of the signal are reduced, and the target can be avoided from being buried in the side lobes.
- the hit direction frequency domain conversion unit samples the signal based on the velocity and distance direction frequency after the hit direction frequency domain conversion at the frequency interval set based on the change of the transmission frequency. Since the discrete Fourier transform is used to do this, it is possible to obtain a radar device with improved target detection performance.
- the chirp z-transform is used to sample the signal based on the velocity in the hit direction frequency domain and the distance direction frequency at an interval set based on the change of the transmission frequency.
- the distance direction frequency domain conversion unit performs distance direction frequency domain conversion to reduce the influence of the movement target, and the hit direction frequency domain conversion unit generates Doppler frequency differences due to modulation bands.
- the distance direction frequency domain conversion unit performs distance direction frequency domain conversion to reduce the influence of the movement target
- the hit direction frequency domain conversion unit generates Doppler frequency differences due to modulation bands.
- a plurality of configurations will be described in N Rx.
- FIG. 30 is a configuration diagram of the transmission units 120a-n Tx .
- the transmitters 120a-n Tx include a transmitter 121-n Tx , a pulse modulator 122-n Tx , a local oscillator 123-n Tx, and an in-pulse modulation signal generator 124a-n Tx .
- the intra-pulse modulation parameter setting unit 125-n Tx is the same as that of the first embodiment except for the intra-pulse modulation signal generator 124a-n Tx .
- FIG. 31 is a block diagram of the first signal processor 230a-n Rx .
- the first signal processor 230a-n Rx is an integration of the distance direction frequency domain conversion unit 231-n Rx , the hit direction frequency domain conversion unit 232-n Rx , the correlation unit 233a-n Rx , and integration. and a part 234-n Rx, configurations other than the correlator 233a-n Rx is the same as that of the first signal processor 230-1 in the first embodiment.
- the second signal processor 240 a is different from that of the first embodiment in that a second integrating unit 243 is provided.
- the intra-pulse modulation signal generators 124a-n Tx of the transmitters 120a-n Tx use the frequency modulation amount Bn Tx and the modulation bandwidth ⁇ Bn Tx according to the equation (55), and the frequency modulation of adjacent frequency bands is complex
- An intra-pulse modulation signal L chp (n Tx , h, t) for frequency modulating the pulse signal so as to be a conjugate is generated and output to the transmitter 121-n Tx .
- ⁇ uses the sign of ⁇ (that is, frequency modulation of down-chirp) when n Tx is odd (that is, frequency modulation of down-chirp) and the sign of + (that is, frequency modulation of up-chirp) that is even.
- FIG. 32 shows the relationship between the frequency modulation amount Bn Tx , the modulation bandwidth ⁇ Bn Tx, and the frequency modulation of each transmission radar.
- the frequency modulation amount B 2 is zero.
- in-pulse modulation ⁇ (n Tx ) may be replaced with frequency modulation and code modulation, for example, a pseudo random sequence may be used.
- the intra-pulse modulation ⁇ (n Tx ) may be replaced with non-linear frequency modulation instead of frequency modulation.
- the modulation of each transmission radar n Tx may be the same. Different modulations may be made to achieve modulation with high orthogonality for each transmission radar n Tx .
- inter-hit code modulation may be performed according to equation (57).
- ⁇ c (h) is an inter-hit modulation code.
- the inter-hit code when inter-hit code modulation is performed, as shown in FIG. 33, the inter-hit code is generated before the distance direction frequency domain conversion unit 231-n Rx as the first signal processor 230b-n Rx.
- a demodulator 235-n Rx is provided to demodulate the inter-hit code according to the equation (58).
- the target reception signal from the assumed distance ambiguity h c is demodulated and integrated without loss, but the reflected received signal having a distance ambiguity different from the assumed distance ambiguity h c is demodulated Not spread, and the phase spreads between hits, is not coherently integrated, and is spread (suppressed). Therefore, by adding a code in the hit direction, the SNR is improved only for the target reflected reception signal from the desired distance fuzzy number, and the reflected reception signal from, for example, clutter from different distance fuzzy numbers is suppressed, and target detection performance It is possible to obtain an improved radar system.
- the in-pulse modulation parameter setting unit 125-n Tx B The intrapulse modulation parameters are calculated and set so as to suppress clutters with different distance ambiguity numbers and velocity ambiguity numbers.
- a SNR after target processing SNR tgt and the hit direction code virtual image of clutter when the modulation is also performed (velocity ambiguity number n clt, v, amb, distance ambiguity number n clt, r, amb) of the processed
- the relationship of SNR clt, v, r, amb (n clt, v, amb , n clt, r, amb ) which is SNR of is expressed as equation (59), and the hit direction represented by equation (60)
- SNR clt, v, r which is the SNR after processing of the virtual image (velocity ambiguity number n clt, v, amb , distance ambiguity number n clt, r, amb ) of the clutter when code modulation is also performed (code spreads) , Amb ( nclt, v, amb , nclt, r, amb ),
- SNR clt, v, amb ( nb ) is the SNR after processing of the virtual image of the clutter (velocity ambiguity number n clt, v, amb , distance ambiguity number n clt, r, amb ) when hit direction code modulation is not performed.
- the virtual image of the clutter (velocity ambiguity number n clt, v, amb , distance ambiguity number n when the hit direction code modulation represented by equation (60) is also performed (the code is spread) compared to clt, v, amb ) SNR after processing clt, r, amb ) SNR clt, v, r, amb (n clt, v, amb , n clt, r, amb ) is suppressed and detection performance is less affected by clutter It is possible to obtain an improved radar device.
- Correlator 233a-n Rx a pulse in the modulated signal L chp (n Tx, h, t) and the same amount of frequency modulation B nTx of the transmitted radar 100a-n Tx and added to the modulation bandwidth DerutaBn Tx, of each speed bin
- a reference signal Ex (n Tx , h czt , m) including the Doppler frequency corresponding to the velocity is generated according to equation (61).
- the correlation units 233a-n Rx respectively transmit radars 100a-n Tx that are the same as the in-pulse modulation signal L chp (n Tx , h, t) according to equation (62).
- a reference signal Ex (n Tx , h czt , m) including the Doppler frequency corresponding to the velocity of each velocity bin is generated according to equation (62) Do.
- the reference signal Ex (n Tx , h czt , m) including the Doppler frequency corresponding to the velocity of each velocity bin is not affected by the Doppler frequency regardless of the intra-pulse modulation. Can be integrated coherently.
- (61) uses ⁇ sign when n Tx is odd (that is, frequency modulation of down-chirp) when n Tx is odd, and uses + sign (that is, frequency modulation of up-chirp when it is even) .
- the contents of the subsequent pulse compression processing are the same as in the correlation unit 233-1 of the first embodiment, and thus the description thereof is omitted here.
- the transmission radar 100a-n Tx transmits a transmission signal in which frequency modulation of adjacent bands is complex conjugate, and the effect when pulse compression is performed by the correlation unit 233a-n Rx will be described.
- FIG. 35 shows a received signal when there is a Doppler frequency.
- the transmission signals of the transmission radars 100a-n Tx are indicated by solid lines, and the reception signals affected by the Doppler frequency are indicated by broken lines. Since the frequency modulation of adjacent bands of the transmission signals of the transmission radars 100a-n Tx is made to be a complex conjugate, cross correlations are canceled out during pulse compression (refer to the arrow 3501), as shown in FIG.
- 36A shows a signal after correlation of the transmission radar 100a-1
- FIG. 36B shows a signal after correlation of the transmission radar 100a-2
- FIG. 36C shows a signal after correlation of the transmission radar 100a-3.
- the side lobe does not rise, and the integration result of the low side lobe can be obtained (see section 3701).
- the bands are combined, the power is increased, and the effect of improving the distance resolution is obtained (see section 3702). That is, it is possible to obtain a radar device with improved detection performance.
- frequency modulation of a target frequency band may be complex conjugate.
- the transmission signal of the transmission radar 100a-1 and the transmission signal of the transmission radar 100a-4, and the transmission signal of the transmission radar 100a-2 and the transmission signal of the transmission radar 100a-3 are complex conjugates. Even with such a configuration, it is possible to obtain the same effect as when transmitting a transmission signal in which frequency modulation of adjacent bands is complex conjugate.
- the second integrating unit 243 receives the signal R Tx Tx (n ⁇ , n Rx , k pc ) based on the velocity and the distance after correlation band-combined from the first signal processors 230 a-1 to N Rx .
- Second integrator section 243 the signal based on the distance after correlation with band synthesis velocity of each reception radar 200a-n Rx R ⁇ Tx (n ⁇ , n Rx, k pc) relative, according to equation (63) It performs integration signal based on the distance after correlation with integrated speed R ⁇ Tx, Rx (n ⁇ , h czt, k pc) for generating a.
- the signal R TxTx (n ⁇ , n Rx , k pc ) based on the band synthesized velocity and correlated distance for each reception radar 200a ⁇ n Rx is coherently integrated
- signal based on the distance after correlation with integrated speed R ⁇ Tx (n ⁇ , n Rx , h czt, k pc) is the arrival angle candidate number of the detected target candidates n theta ', velocity bin number h czt' and distance
- the power shows the maximum value at the sampling number k pc ′ of the direction frequency.
- Second integrator section 243 the signal R ShigumaTx based on distance after correlation with integrated velocity, Rx (n ⁇ , h czt , k pc) and the arrival angle candidate number of the detected target candidates n theta ', speed
- the bin number h czt ′ and the sampling number k pc ′ of the frequency in the distance direction are output to the target candidate detection unit 241.
- the operations after the target candidate detection unit 241 are the same as in the first embodiment.
- the frequency modulation of adjacent bands of transmission signals from the transmission radars 100a-n Tx is made to be a complex conjugate, so that cross correlations cancel each other during pulse compression, There is an effect that an unnecessary peak does not occur and a side lobe does not rise.
- the band synthesis is performed by the integration unit 234-1n Rx , the influence of the cross correlation is not generated, the side lobe does not rise, and the integration result of the low side lobe can be obtained. That is, it is possible to obtain a radar device with improved detection performance.
- the second integration unit 243 by integrating the signal of each of the reception radars 200a-n Rx by the second integration unit 243, it is possible to obtain a radar device in which the power is increased and the detection performance is improved. Furthermore, by integrating the signal of each of the reception radars 200a-n Rx , the antenna aperture length is virtually increased, so that the angle resolution can be improved.
- the signal based on the band synthesized velocity and the distance after correlation is integrated with the target arrival angle candidate, and the signal based on the integrated velocity and the distance after correlation Since the target candidate detection unit detects the target candidate for the output signal of the second integration unit instead of the integration unit, the power increases and the detection performance is increased. And the angular resolution can be improved.
- the plurality of transmission radars have different frequencies based on the transmission frequency in which the inside of the pulse is frequency-modulated in ascending order and descending order so that frequency modulation of adjacent frequency bands becomes complex conjugate. Since the transmission signal of (1) is radiated at the set frequency interval, the cross correlation is canceled at the time of pulse compression, an unnecessary peak is not generated, and the side lobe does not rise. As a result, a radar device with improved detection performance can be obtained.
- the plurality of transmission radars are different based on the transmission frequency in which the inside of the pulse is frequency-modulated in ascending order and descending order so that frequency modulation of the target frequency band becomes complex conjugate. Since the transmission signal of the frequency is radiated at the set frequency interval, the cross correlation is canceled in the pulse compression, the unnecessary peak is not generated, and the side lobe does not rise. As a result, a radar device with improved detection performance can be obtained.
- the plurality of transmission radars since the plurality of transmission radars perform code modulation or non-linear frequency modulation as intra-pulse modulation, there is no influence of Doppler frequency as in frequency modulation, and integration loss Thus, it is possible to obtain a radar device with improved detection performance and distance measurement performance. Also, since different code modulation or non-linear frequency with high degree of orthogonality is used for each transmission radar, cross correlation is canceled at the time of pulse compression, unnecessary peaks do not occur, and side lobes do not rise. As a result, a radar device with improved detection performance can be obtained.
- the plurality of transmission radars perform inter-hit code modulation in addition to intra-pulse modulation, and at the front stage of the distance direction frequency domain conversion unit Since the inter-hit code demodulation unit for demodulating the code is provided, only the target reflected reception signal from the desired distance ambiguity number improves the SNR, and the reflection reception signal from, for example, clutter from different distance ambiguity numbers is suppressed and target detection It is possible to obtain a radar device with improved performance.
- the present invention allows free combination of each embodiment, or modification of any component of each embodiment, or omission of any component in each embodiment. .
- the radar apparatus relates to a configuration capable of improving the target detection performance even in the presence of the influence of the target Doppler frequency, and is suitable for use in a MIMO radar or the like.
- 100-n Tx transmission radar 110-n Tx antenna, 120-n Tx , 120a-n Tx transmitter, 121-n Tx transmitter, 122-n Tx pulse modulator, 123-n Tx local oscillator, 124-n Tx , 124a-n Tx intra-pulse modulation signal generator, 125-n Tx intra-pulse modulation parameter setting unit, 200-1, 200-n Rx , 200 a-n Rx reception radar, 210-1, 210-n Rx antenna, 220-1, 220-n Rx receiver, 221-1, 221-n Rx receiver, 222-1, 222-n Rx A / D converter, 230-1, 230-n Rx , 230a-n Rx , 230b-n Rx first signal processor, 231-1,231-n Rx distance direction frequency domain transform unit, 232-1,232-n Rx hit direction frequency domain transform section, 33-1,233-n Rx, 233a-n Rx correlation unit, 2
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Abstract
Description
実施の形態1.
図1は、本実施の形態によるレーダ装置の構成図である。
本実施の形態によるレーダ装置は、図示のように、送信レーダ100-nTx(送信レーダ番号nTx、送信レーダ数NTxの場合、nTx=1,2,…,NTx)、受信レーダ200-1(受信レーダ番号nRx、受信レーダ数NRxの場合、nRx=1,2,…,NRx、実施の形態1ではNRx=1の構成を説明する)、第2の信号処理器240、表示器250で構成される。また、送信レーダ100-nTxは、空中線110-nTx、送信部120-nTxで構成される。送信部120-nTxは、図2に示すように送信機121-nTx、パルス変調器122-nTx、局部発振器123-nTx、パルス内変調信号発生器124-nTx、パルス内変調パラメータ設定部125-nTxで構成される。
レーダ装置は、プロセッサ1、入出力インタフェース2、メモリ3、外部記憶装置4、信号路5からなる。プロセッサ1は、レーダ装置における送信レーダ100-nTx、受信レーダ200-1及び第2の信号処理器240の機能を実現するためのプロセッサである。入出力インタフェース2は、送信レーダ100-nTxにおける空中線110-nTxと受信レーダ200-1における空中線210-1からの送受信信号のインタフェースであり、また、表示器250への出力信号のインタフェースである。メモリ3は、本実施の形態のレーダ装置を実現するための各種プログラムを記憶するプログラムメモリ、プロセッサ1がデータ処理を行う際に使用するワークメモリ及び信号データを展開するメモリ等として使用するROM及びRAM等の記憶部である。外部記憶装置4は、プロセッサ1の各種設定データや信号データなどの各種データを蓄積するために使用される。外部記憶装置4としては、たとえば、SDRAMなどの揮発性メモリ、HDDまたはSSDを使用することが可能である。OS(オペレーティングシステム)を含むプログラムや、各種設定データ、信号データ等の各種データを蓄積することができる。なお、この外部記憶装置4に、メモリ3内のデータを蓄積しておくこともできる。信号路5は、プロセッサ1、入出力インタフェース2、メモリ3及び外部記憶装置4を相互に接続するためのバスである。
また、プロセッサ1及びメモリ3は複数であってもよく、これら複数のプロセッサ1とメモリ3とが連携して信号処理を行うよう構成してもよい。
さらに、送信レーダ100-nTx、受信レーダ200-1及び第2の信号処理器240の少なくともいずれかを専用のハードウェアで構成してもよい。
まず、送信レーダ100-nTxの送信動作について、図4を参照して説明する。
ここで、送信レーダ100-nTxは、空中線110-nTxが分散配置されていれば良く、アンテナ素子を分散配置しても良い。すなわち、MIMO(multiple-input and multiple-output)レーダ、DBF(デジタルビームフォーミング)で実現しても良い。
送信レーダ100-nTxの送信動作では、局部発振器123-nTxは、式(1)に示すように、局部発振信号L0(t)を生成し、パルス変調器122-nTxに出力する(ステップST11)。
ここで、hはヒット番号、Hはヒット数(式(3)で表され、floor(X)は変数Xの小数点以下を切り捨てた整数である)である。
その後は、空中線110-nTxから送信信号Tx(nTx,h,t)が空中に放射される(ステップST15)。
空中に放射された送信信号は、目標で反射され、反射信号として空中線210-1に入射される。そこで、空中線210-1は、入射してきた反射信号を受信し、式(6)で表される受信レーダ200-nRxの受信信号Rx(nRx,h,t)として受信機221-1に出力する(ステップST21)。ここで、Rx0(nTx,nRx,h,t)は式(7)で表される送信レーダ100-nTxの反射信号を受信レーダ200-nRxが受信した受信信号、ARは反射信号の振幅、R0は目標初期相対距離、vは目標相対速度、θは目標角度、cは光速、t’は1ヒット内の時間である。
受信レーダ200-nRxの受信ビデオ信号V(nRx,h,m)は、式(12)で表されるように複数の送信レーダが異なる中心周波数で変調した信号が重畳されている。第1の信号処理器230-1は、複数の送信レーダが送信し、目標で反射して、受信した受信信号を送信レーダ毎に分離し、コヒーレントに積分することで、検出性能向上を可能とする。
一般的に、送信レーダ毎に受信信号を分離するために、送信レーダ毎の変調成分に基づく参照信号と受信信号を相関する、つまりパルス圧縮が行われている。図9A、図9B、図9Cは、ドップラ周波数の影響が無い場合の、送信レーダ毎の相関後の信号を示す。図9Aは送信レーダ100-1、図9Bは送信レーダ100-2、図9Cは送信レーダ100-3の相関後の信号を示している。これら図9A~図9Cに示すように、送信レーダ毎に帯域が異なるため、送信レーダ毎の受信信号を分離することができる。目標相対距離に積分されていることが分かる。また、隣り合う帯域の影響により相互相関が発生し、サイドローブが若干上昇している(図中、区間901参照)。
距離方向周波数領域変換部231-1は、受信レーダ200-nRxの受信ビデオ信号V(nRx,h,m)を取得する(ステップST41)と、この受信ビデオ信号V(nRx,h,m)に対して式(17)に従い高速フーリエ変換(FFT:Fast Fourier Transform)を行い、距離方向周波数に基づく信号FV(nRx,h,kr)を生成する(ステップST42)。式(17)において、fsampはサンプリング周波数、Mfftは距離方向FFT点数、krは距離方向周波数のサンプリング番号である。距離方向周波数領域に変換後の距離方向周波数ビン番号krの距離方向周波数fr,samp(kr)は式(18)で表され、距離方向周波数領域のサンプリング間隔Δfsampは式(19)で表される。
また、図13に受信ビデオ信号V(nRx,h,m)と、距離方向周波数に基づく信号FV(nRx,h,kr)のスペクトルを示す。図13Aは受信ビデオ信号、図13Bは距離方向周波数に基づく信号を表す。図13Aにおいて、点線で示す距離の値は、目標初期相対距離R0とあいまいさなく計測可能な距離Rambである。また、図13Bのfsampはサンプリング周波数である。図13Aでは、ヒット毎に受信される距離がvTpri/2だけ変化していることを説明している。一方、図13Bでは、全ヒットで目標相対速度vに相当するドップラ周波数だけ変化していることを説明している。距離方向周波数領域変換部231-1が距離方向周波数に基づく信号FV(nRx,h,kr)を生成したため、送信レーダの送信周波数の帯域毎に距離方向周波数で分離することが可能になる。また、距離方向が時間軸だった受信ビデオ信号では、移動目標の場合、ヒット間で同じ距離ビンでなく、積分損失が発生する可能性があったが、距離方向周波数に基づく信号ではヒット間で同じ距離方向周波数ビンに統一され、積分損失なくヒット方向に積分することが可能になる。
ヒット方向周波数領域変換部232-1は、距離方向周波数に基づきCZTの変換関数を変化させることで、ヒット方向周波数領域変換後の信号のドップラ速度ビンを同じになるように動作する。
図14に示すように距離方向周波数に基づく信号は距離方向周波数に応じてドップラ周波数が異なっているのに対して、図15に示すようにヒット方向周波数領域変換部232-1のヒット方向周波数領域変換によって目標相対速度ビンに現れることを説明している。
窓関数処理を行った場合、ヒット方向周波数領域変換部232-1は、距離方向周波数に基づく信号FV(nRx,h,kr)に代えて、窓関数処理後の距離方向周波数に基づく信号FV’(nRx,h,kr)を代入し、式(24)あるいは式(33)に従いヒット方向周波数領域に変換し、速度と距離方向周波数に基づく信号FCZT(nRx,hczt,kr)を生成する。
ヒット方向周波数領域変換部232-1は、速度と距離方向周波数に基づく信号FCZT(nRx,hczt,kr)を相関部233-1に出力する。
ドップラ周波数がある場合、つまり、移動目標の場合、観測時間中の移動距離が距離分解能以上になり、積分損失が劣化する問題がある。実施の形態1は、ヒット方向周波数領域変換処理の前に、距離方向周波数領域変換部231-1を設けているため、ヒット間で距離方向周波数ビンが統一され、観測時間中の移動距離の影響なく、ヒット方向周波数領域変換処理をコヒーレント積分として積分損失なく行うことが可能になる。
図17及び図18を参照して、相関部233-1の速度と距離方向周波数に基づく信号FCZT(nRx,hczt,kr)と各送信レーダの送信周波数及び各速度ビンに対応した速度に基づく参照信号Ex(nTx,hczt,m)との周波数領域での相関処理、つまりパルス圧縮について説明する。図17において、処理ブロック1701-1は、受信レーダ200-nRxの速度と距離方向周波数に基づく信号FCZT(nRx,hczt,kr)と送信レーダ100-1の送信周波数及び各速度ビン番号hcztに対応した速度に基づく参照信号Ex(1,hczt,m)との相関処理(パルス圧縮処理)を示す。また、処理ブロック1701-Nは、受信レーダ200-nRxの速度と距離方向周波数に基づく信号FCZT(nRx,hczt,kr)と送信レーダNTxの送信周波数及び各速度ビン番号hcztに対応した速度に基づく参照信号Ex(NTx,hczt,m)との相関処理(パルス圧縮処理)を示している。また、図18は速度と相関後の距離に基づく信号を示し、点線で示す距離の値は、あいまいさなく計測可能な距離Rambである。
相関部233-1は、送信周波数毎に分離した速度と相関後の距離に基づく信号RPC(nTx,nRx,hczt,kpc)を積分部234-1に出力する。
パルス内変調パラメータ設定部125-nTxBは、パルス内変調パラメータをパルス内変調信号発生器124-nTxに出力する。
表示器250は、信号処理結果として、目標情報として目標候補到来角θ’tgt、目標候補相対速度v’tgt、目標候補相対距離R’tgtを画面上に表示する。
実施の形態2に係わるレーダ装置は、図29に示すように、送信レーダ100a-nTx(送信レーダ番号nTx、送信レーダ数NTxの場合、nTx=1,2,…,NTx)、受信レーダ200a-nRx(受信レーダ番号nRx、受信レーダ数NRxの場合、nRx=1,2,…,NRxであり、実施の形態2ではNRxが複数の構成を説明する)、第2の信号処理器240a、表示器250で構成される。
図30は、送信部120a-nTxの構成図である。図示のように、送信部120a-nTxは、送信機121-nTxと、パルス変調器122-nTxと、局部発振器123-nTxと、パルス内変調信号発生器124a-nTxと、パルス内変調パラメータ設定部125-nTxとを備え、パルス内変調信号発生器124a-nTx以外は実施の形態1と同様である。
第2の信号処理器240aでは、第2の積分部243を備える点が実施の形態1とは異なる。
図32に各送信レーダの周波数変調量BnTxと変調帯域幅ΔBnTxと周波数変調の関係を示す。周波数変調量B2は0である。
式(61)中の±はnTxが奇数の場合は-の符号(つまり、ダウンチャープの周波数変調になる)、偶数の場合は+の符号(つまり、アップチャープの周波数変調になる)を用いる。以降のパルス圧縮処理内容は、実施の形態1の相関部233-1と同様であるので、ここでの説明は省略する。
Claims (13)
- パルス信号と当該パルス信号を変調するパルス内変調信号とを用いて生成したそれぞれ異なる周波数の送信信号を放射する複数の送信レーダと、
目標で反射して戻った前記送信信号の受信信号を受信ビデオ信号に変換する受信部と、
前記受信ビデオ信号を、距離方向周波数に基づく信号に変換する距離方向周波数領域変換部と、
前記距離方向周波数に基づく信号を、前記送信信号の周波数の変化とは独立して目標のドップラ周波数が同一の速度ビン番号に属するように、速度と距離方向周波数に基づく信号に変換するヒット方向周波数領域変換部と、
前記ヒット方向周波数領域変換部の出力信号に対して、前記複数の送信レーダの送信周波数と速度ビン番号に対応する速度に対応した参照信号を用いて相関処理を行い、前記複数の送信レーダの送信周波数毎に分離された速度と相関後の距離に基づく信号を生成する相関部と、
前記相関部の出力信号を目標到来角候補で積分し、帯域合成された速度と相関後の距離に基づく信号を生成する積分部と、
前記積分部の出力信号に対して、信号強度に基づき目標候補を検出する目標候補検出部と、
前記目標候補の相対速度、相対距離及び到来角を算出する目標相対速度・相対距離・到来角算出部とを備えたことを特徴とするレーダ装置。 - 前記帯域合成された速度と相関後の距離に基づく信号を目標到来角候補で積分し、当該積分された速度と相関後の距離に基づく信号を生成する第2の積分部を備え、前記目標候補検出部は、前記積分部に代えて当該第2の積分部の出力信号に対して目標候補の検出を行うことを特徴とする請求項1記載のレーダ装置。
- 前記複数の送信レーダは、虚像抑圧度評価値と設定された閾値とに基づき速度あいまい数の異なる信号を抑圧するパルス内変調パラメータを算出及び設定するパルス内変調パラメータ設定部を備えたことを特徴とする請求項1または請求項2記載のレーダ装置。
- 前記複数の送信レーダは、パルス信号を周波数変調することを特徴とする請求項1または請求項2記載のレーダ装置。
- 前記複数の送信レーダは、パルス内を昇順または降順に周波数変調させた送信周波数に基づく異なる周波数の送信信号を、設定された周波数間隔で放射することを特徴とする請求項3記載のレーダ装置。
- 前記複数の送信レーダは、隣り合う周波数帯域の周波数変調が複素共役になるようにパルス内を昇順と降順に周波数変調させた送信周波数に基づく異なる周波数の送信信号を設定された周波数間隔で放射することを特徴とする請求項3記載のレーダ装置。
- 前記複数の送信レーダは、対象的な周波数帯域の周波数変調が複素共役になるようにパルス内を昇順と降順に周波数変調させた送信周波数に基づく異なる周波数の送信信号を設定された周波数間隔で放射することを特徴とする請求項3記載のレーダ装置。
- 前記複数の送信レーダは、パルス信号を符号変調またはノンリニア周波数変調することを特徴とする請求項1または請求項2記載のレーダ装置。
- 前記複数の送信レーダは、パルス内変調に加えてヒット間符号変調を行うと共に、
前記距離方向周波数領域変換部の前段に、距離あいまい数に基づきヒット間符号を復調するヒット間符号復調部を備えたことを特徴とする請求項1または請求項2記載のレーダ装置。 - 前記ヒット方向周波数領域変換部は、前記距離方向周波数に基づく信号に対して窓関数処理を加えて変換処理を行うことを特徴とする請求項1または請求項2記載のレーダ装置。
- 前記ヒット方向周波数領域変換部は、ヒット方向周波数領域変換後の速度と距離方向周波数に基づく信号を送信周波数の変化に基づき設定された周波数間隔でサンプリングするのに離散フーリエ変換を用いることを特徴とする請求項1または請求項2記載のレーダ装置。
- 前記ヒット方向周波数領域変換部は、ヒット方向周波数領域変換後の速度と距離方向周波数に基づく信号を送信周波数の変化に基づき設定された間隔でサンプリングするのにチャープz変換を用いることを特徴とする請求項1または請求項2記載のレーダ装置。
- 前記複数の送信レーダのうち、いずれか一つの送信レーダのみを動作させることを特徴とする請求項1または請求項2記載のレーダ装置。
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