WO2022264187A1

WO2022264187A1 - Radar signal processing device, radar signal processing method, and radar device

Info

Publication number: WO2022264187A1
Application number: PCT/JP2021/022426
Authority: WO
Inventors: 智也山岡; 啓諏訪
Original assignee: 三菱電機株式会社
Priority date: 2021-06-14
Filing date: 2021-06-14
Publication date: 2022-12-22
Also published as: JP6961135B1; JPWO2022264187A1

Abstract

A radar signal processing device (40) comprises a pulse signal acquisition unit (41) for acquiring scattered pulse signals from a plurality of observation points included in an observation region (3) of a radar device, and a phase correction unit (46) for correcting the phases of the pulse signals on the basis of the distances between a point within the synthetic aperture (1) of the radar device and the points corresponding to the range cells of the pulse signals acquired by the pulse signal acquisition unit (41) from among a plurality of points on a projection line that is a line that has been obtained by projecting, onto the surface of the earth, a line connecting one point within the observation region (3) to the point within the synthetic aperture (1) of the radar device.

Description

RADAR SIGNAL PROCESSING DEVICE, RADAR SIGNAL PROCESSING METHOD AND RADAR DEVICE

The present disclosure relates to a radar signal processing device, a radar signal processing method, and a radar device.

As one of synthetic aperture radar systems, there is a DBS (Doppler Beam Sharpening) system (see Non-Patent Document 1). In the DBS method, the Doppler frequency of each observation point is calculated by performing a Fourier transform in the azimuth direction on pulse signals scattered by each of a plurality of observation points included in an observation area on the ground surface. It generates a DBS image showing the intensity of the Doppler frequency of the observation point. The phase of the pulse signal after scattering by each observation point changes with the movement of the platform on which the synthetic aperture is mounted.
In order to suppress the influence of phase changes due to movement of the platform, the conventional radar signal processing apparatus using the DBS method uses the distance between the center point of the observation area and the center point of the synthetic aperture to determine the post-scattering from each observation point. to compensate for the phase of the pulse signal.

The Doppler frequency of each observation point can be affected by the so-called squint angle and cause displacement. The squint angle is the angle formed between the direction perpendicular to the azimuth direction and the radiation direction of the pulse signal on the ground surface. The displacement amount of the Doppler frequency (hereinafter referred to as "frequency displacement amount") varies depending on the position of the observation point. Therefore, among the plurality of observation points, there is an observation point where the "displacement difference amount of the Doppler frequency", which will be described later, is larger than half of the PRF (Pulse Repetition Frequency) of the pulse signal emitted from the radar device. sometimes The Doppler frequency displacement difference amount is the difference between the absolute value of the frequency displacement amount at the observation point and the absolute value of the frequency displacement amount at the center point of the observation area. A pulse signal after being scattered by an observation point with a Doppler frequency displacement difference amount larger than half of the PRF becomes azimuth ambiguity, and as a result, the imaging of the observation point may be degraded.
The pulse signal phase compensation by the conventional radar signal processing apparatus is performed based on the distance between the center point of the observation area and the center point of the synthetic aperture regardless of the position of the observation point. Therefore, even if the conventional radar signal processing apparatus changes the Doppler frequency of each observation point by compensating for the phase of the pulse signal after scattering by each observation point, the displacement difference amount of the Doppler frequency is less than the PRF. There was a problem that the number of observation points larger than half does not always decrease.

The present disclosure has been made to solve the above problems, and is a radar signal processing apparatus and radar signal processing that can reduce the number of observation points where the displacement difference amount of the Doppler frequency is larger than half of the PRF. Aim to get a method.

A radar signal processing apparatus according to the present disclosure includes a pulse signal acquisition unit that acquires a pulse signal after scattering by each of a plurality of observation points included in an observation area of a radar apparatus, one point in the observation area, and a radar apparatus. Among a plurality of points existing on a projection line, which is a line projected onto the ground surface connecting a point in the synthetic aperture, the range cell of each pulse signal acquired by the pulse signal acquisition unit A phase compensator is provided for compensating the phase of each pulse signal based on the distance between the corresponding point and one point within the synthetic aperture.

According to the present disclosure, it is possible to reduce the number of observation points where the amount of Doppler frequency displacement difference is larger than half the PRF.

FIG. 1A is a perspective view showing the relationship between the synthetic aperture 1 and the observation area 3 of the radar apparatus according to Embodiment 1, and FIG. 1B is a plan view showing the observation area 3 on the ground surface. 1 is a configuration diagram showing a radar device including a radar signal processing device 40 according to Embodiment 1; FIG. 1 is a configuration diagram showing a radar signal processing device 40 according to Embodiment 1; FIG. 2 is a hardware configuration diagram showing hardware of the radar signal processing device 40 according to Embodiment 1. FIG. 2 is a hardware configuration diagram of a computer when the radar signal processing device 40 is realized by software, firmware, or the like. FIG. 4 is an explanatory diagram showing an example of measurement of Doppler frequencies on the ground surface including the observation area 3; FIG. 4 is a flowchart showing a radar signal processing method, which is a processing procedure of the radar signal processing device 40; 4 is an explanatory diagram showing an example of measurement of Doppler frequencies on the ground surface including the observation area 3; FIG.

Hereinafter, in order to describe the present disclosure in more detail, embodiments for carrying out the present disclosure will be described according to the attached drawings.

Embodiment 1.
FIG. 1 is an explanatory diagram showing the relationship between a synthetic aperture 1 and an observation area 3 that the radar device according to Embodiment 1 has.
FIG. 1A is a perspective view showing the relationship between a synthetic aperture 1 and an observation area 3 that the radar device according to Embodiment 1 has, and FIG. 1B is a plan view showing the observation area 3 on the ground surface.
A synthetic aperture 1 of the radar system is mounted on a platform and moves as the platform moves. The azimuth direction, which is the moving direction of the synthetic aperture 1, is the same as the moving direction of the platform. Platforms are, for example, satellites or airplanes.
Assuming that the length of the synthetic aperture 1 in the azimuth direction is D, the center point 1a of the synthetic aperture 1 is located at a distance of D/2 from one end of the synthetic aperture 1 in the azimuth direction. The point is that the distance from the edge is D/2. When the synthetic aperture 1 is represented on a two-dimensional plane as shown in FIG. 1A, the center point 1a of the synthetic aperture 1 is the distance from one end in the direction orthogonal to the azimuth direction and the distance from the azimuth direction on the two-dimensional plane. The difference is that the distance from the other end in the orthogonal direction is the same.
However, the center point 1a is not strictly limited to the center point of the synthetic aperture 1, and may be a point deviated from the center point of the synthetic aperture 1 within a practically acceptable range.

An observation area 3 is an observation area of the radar device that exists on the ground surface. A plurality of observation points 2 are present inside the observation area 3 .
FIG. 1 shows an example in which the observation area 3 has a rectangular shape, and C ₁ , C ₂ , C ₃ , and C ₄ indicate corner points of the observation area 3 . The shape of the observation area 3 is not limited to a rectangle, and the shape of the observation area 3 may be, for example, a polygon other than a rectangle, or a circle.
In the example of FIG. ₁ , the center point 3a of the observation area ₃ is the intersection of the line segment connecting C1 and C3 and the line segment connecting _C2 and _C4 .
θ _sq is the squint angle. The ground range line GRL is a line (projection line) obtained by projecting a line connecting the center point 3a of the observation region 3 and the center point 1a of the synthetic aperture 1 onto the ground surface.
Note that the center point 3a is not strictly limited to the center point of the observation area 3, and may be a point deviated from the center point of the observation area 3 within a practically acceptable range. Therefore, the ground range line GRL may be a line that connects a certain point within the observation area 3 and a certain point within the synthetic aperture 1 and is projected onto the ground surface.

FIG. 2 is a configuration diagram showing a radar device including the radar signal processing device 40 according to Embodiment 1. As shown in FIG.
FIG. 3 is a configuration diagram showing the radar signal processing device 40 according to Embodiment 1. As shown in FIG.
FIG. 4 is a hardware configuration diagram showing hardware of the radar signal processing device 40 according to the first embodiment.
The radar device shown in FIG. 2 includes a signal generation section 10, an analog circuit section 20, an antenna section 30, and a radar signal processing device 40. FIG.

The signal generation unit 10 includes a pulse signal generator 11 , an auxiliary information storage unit 12 , a digital signal storage unit 13 and a DBS image storage unit 14 .
The analog circuit section 20 includes an oscillation section 21, a multiplication section 22, an amplification section 23, a switching section 24, an amplification section 25, a multiplication section 26, a filter section 27, and an analog-to-digital converter (hereinafter referred to as "A/D converter") 28. ing.

The pulse signal generator 11 generates a pulse signal and outputs the pulse signal to the multiplier 22 .
The pulse signal generated by the pulse signal generator 11 may be a simple pulse signal whose signal level repeatedly changes between H level and L level, or may be a chirped pulse signal.
The auxiliary information storage unit 12 stores platform trajectory information, observation geometric information, radar specifications, and the like as auxiliary information.
The digital signal storage unit 13 temporarily stores the digital signal output from the A/D converter 28 and outputs the digital signal to the radar signal processing device 40 .
The DBS image storage unit 14 stores DBS images generated by the radar signal processing device 40 .

The oscillator 21 oscillates a carrier wave.
The multiplier 22 up-converts the frequency of the pulse signal by multiplying the pulse signal output from the pulse signal generator 11 by the carrier wave oscillated by the oscillator 21 .
The multiplier 22 outputs the up-converted pulse signal to the amplifier 23 .
The amplifying unit 23 amplifies the up-converted pulse signal output from the multiplying unit 22 and outputs the amplified pulse signal to the switching unit 24 .

Switching section 24 outputs the amplified pulse signal output from amplifying section 23 to antenna section 30 and outputs the received signal output from antenna section 30 to amplifying section 25 .
Amplification section 25 amplifies the reception signal output from switching section 24 and outputs the amplified reception signal to multiplication section 26 .
Multiplying section 26 multiplies the carrier wave oscillated by oscillating section 21 by the amplified received signal output from amplifying section 25, thereby down-converting the frequency of the received signal.
Multiplying section 26 outputs the down-converted received signal to filtering section 27 .

The filter unit 27 is implemented by, for example, a bandpass filter.
The filter unit 27 suppresses out-of-band components contained in the down-converted received signal output from the multiplication unit 26 and outputs the out-of-band component-suppressed received signal to the A/D converter 28 .
The A/D converter 28 converts the received signal after out-of-band component suppression output from the filter unit 27 from an analog signal to a digital signal, and outputs the digital signal to the digital signal storage unit 13 .

The antenna unit 30 radiates the pulse signal output from the switching unit 24 as a beam toward the observation area 3 .
Further, the antenna unit 30 receives pulse signals after scattering by each observation point 2 included in the observation area 3 and outputs the pulse signals after scattering to the switching unit 24 as received signals.

The radar signal processing device 40 includes a pulse signal acquisition section 41 , a phase compensation section 46 and an image generation section 47 .
The pulse signal acquisition unit 41 includes a Fourier transform unit 42 , a range compression unit 43 , a compensation processing unit 44 and an inverse Fourier transform unit 45 .
The pulse signal acquisition unit 41 acquires each digital signal stored in the digital signal storage unit 13 as a pulse signal after scattering by each of the plurality of observation points 2 included in the observation area 3 .

The Fourier transform unit 42 is realized by, for example, a Fourier transform circuit 51 shown in FIG.
The Fourier transform unit 42 acquires each digital signal from the digital signal storage unit 13 and Fourier transforms each digital signal in the range direction.
The Fourier transform unit 42 outputs each Fourier-transformed signal to the range compression unit 43 .

The range compression unit 43 is realized by, for example, the range compression circuit 52 shown in FIG.
The range compression unit 43 multiplies each Fourier-transformed signal output from the Fourier transform unit 42 by a reference function for range compression, thereby compressing the range of each Fourier-transformed signal.
The range compression unit 43 outputs each range-compressed signal to the compensation processing unit 44 .

The compensation processing unit 44 is realized by, for example, a compensation processing circuit 53 shown in FIG.
The compensation processing unit 44 performs range cell migration compensation on each range-compressed signal output from the range compression unit 43 .
The compensation processing unit 44 outputs each migration-compensated signal to the inverse Fourier transform unit 45 .

The inverse Fourier transform unit 45 is implemented by, for example, an inverse Fourier transform circuit 54 shown in FIG.
The inverse Fourier transform unit 45 inverse Fourier transforms the migration-compensated signals output from the compensation processing unit 44 in the range direction.
The inverse Fourier transform unit 45 outputs the signals after the inverse Fourier transform to the phase compensation unit 46 as the pulse signals acquired by the pulse signal acquisition unit 41 .

The phase compensator 46 is implemented by, for example, a phase compensator 55 shown in FIG.
The phase compensator 46 selects points corresponding to the range cells of the respective pulse signals acquired by the pulse signal acquirer 41 and the center point of the synthetic aperture 1 among a plurality of points existing on the ground range line GRL. Based on the distance from 1a, the phase of each pulse signal is compensated.
In the radar signal processing device 40 shown in FIG. 3, it is assumed that the ground range line GRL is a line that connects the center point 3a of the observation area 3 and the center point 1a of the synthetic aperture 1 and is projected onto the ground surface. doing. If one end of the ground range line GRL is a point other than the center point 3a of the observation area 3 and the other end of the ground range line GRL is a point other than the center point 1a of the synthetic aperture 1, phase compensation is performed. The unit 46 compensates the phase of the pulse signal by using a certain point within the synthetic aperture 1 instead of the center point 1a of the synthetic aperture 1 .
The phase compensator 46 outputs each phase-compensated pulse signal to the image generator 47 .

The image generation unit 47 is realized by, for example, the image generation circuit 56 shown in FIG.
The image generation unit 47 generates a DBS image by Fourier transforming the pulse signals after phase compensation by the phase compensation unit 46 in the azimuth direction.
The image generation unit 47 outputs the DBS image to the DBS image storage unit 14 .

3, each of the Fourier transform unit 42, the range compression unit 43, the compensation processing unit 44, the inverse Fourier transform unit 45, the phase compensation unit 46, and the image generation unit 47, which are components of the radar signal processing device 40, are shown in FIG. It is assumed to be realized by dedicated hardware as shown in . That is, it is assumed that the radar signal processing device 40 is implemented by a Fourier transform circuit 51, a range compression circuit 52, a compensation processing circuit 53, an inverse Fourier transform circuit 54, a phase compensation circuit 55 and an image generation circuit 56.

Each of the Fourier transform circuit 51, the range compression circuit 52, the compensation processing circuit 53, the inverse Fourier transform circuit 54, the phase compensation circuit 55 and the image generation circuit 56 may be, for example, single circuits, multiple circuits, programmed processors, parallel programs. processor, ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or a combination thereof.

The constituent elements of the radar signal processing device 40 are not limited to those realized by dedicated hardware, and the radar signal processing device 40 may be realized by software, firmware, or a combination of software and firmware. There may be.
Software or firmware is stored as a program in a computer's memory. A computer means hardware that executes a program, for example, a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor). do.

FIG. 5 is a hardware configuration diagram of a computer when the radar signal processing device 40 is implemented by software, firmware, or the like.
When the radar signal processing device 40 is realized by software, firmware, or the like, each A memory 61 stores a program for causing a computer to execute a processing procedure. A processor 62 of the computer then executes the program stored in the memory 61 .

4 shows an example in which each component of the radar signal processing device 40 is implemented by dedicated hardware, and FIG. 5 shows an example in which the radar signal processing device 40 is implemented by software, firmware, or the like. ing. However, this is only an example, and some components in the radar signal processing device 40 may be implemented by dedicated hardware, and the remaining components may be implemented by software, firmware, or the like.

FIG. 6 is an explanatory diagram showing a measurement example of the Doppler frequency of the ground surface including the observation area 3. In FIG.
In FIG. 6, the Doppler frequency of the central point 3a of the observation area 3 is used as the reference Doppler frequency, and the Doppler frequencies of the respective observation points 2 included in the observation area 3 are displayed on a contour map. The reference Doppler frequency is 0 [Hz], and the Doppler frequency at observation point 2 is the difference from the reference Doppler frequency. In the contour map shown in FIG. 6, for example, the higher the concentration, the lower the Doppler frequency.
The straight line shown in FIG. 6 is the ground range line GRL.

The Doppler frequency differs for each position of the observation point 2, as shown in FIG. For example, among observation point C ₁ , observation point C ₂ , observation point C ₃ , and observation point C ₄ , which are corner points of observation area 3, the Doppler frequencies of observation point C ₂ and observation point C ₄ are Although the Doppler frequency is close to the Doppler frequency of the center point 3a, the Doppler frequencies of the observation points C ₁ and C ₃ are significantly different from the Doppler frequency of the center point 3a of the observation area 3 . Therefore _, the difference in displacement between the Doppler frequencies at the observation points C1 and C3 may be larger than _half the PRF.
The reason why the Doppler frequencies of the observation points C ₁ and C ₃ differ greatly from the Doppler frequency of the center point 3a of the observation area 3 is that the squint angle θ _sq is not 0 and the radar equipment observes in an oblique direction. This is because the change in the frequency displacement amount becomes steeper as the region 3 is observed and the squint angle θ _sq increases. The difference between the absolute values of the Doppler frequencies at the observation points C ₁ and C ₃ and the absolute value of the Doppler frequency at the center point 3a of the observation area 3 changes with the change in the squint angle θ _sq .

The conventional radar signal processing device compensates the phase of the pulse signal after being scattered by each of the observation points C ₁ , C ₂ , C ₃ and C ₄ . However, the pulse signal phase compensation by the conventional radar signal processing apparatus is performed based on the distance between the center point 3a of the observation area 3 and the center point 1a of the synthetic aperture 1 regardless of the position of the observation point 2. . Therefore, the conventional radar signal processing apparatus compensates for the phase of the pulse signal after being scattered by each of the observation points C ₁ , C ₂ , C ₃ and C ₄ , so that the observation points C ₁ , Even if the Doppler frequencies at observation points C ₂ , C ₃ and C ₄ are changed, the Doppler frequency displacement at observation points with large frequency displacements such as observation points C ₁ and C ₃ The amount of difference may not be less than half the PRF. Unless the displacement difference amount of the Doppler frequency becomes less than half of the PRF _, the pulse signals after scattering by _each of the observation points C1 and C3 become azimuth ambiguity, and as a result, the observation _point C1 and the observation point C3 Each of the points C3 may not be imaged _on the image.

Among a plurality of points existing on the ground range line GRL, the difference between the Doppler frequency of the _point _R1 corresponding to the range cell of the pulse signal of the observation point C1 and the Doppler frequency of the observation _point C1 is the squint Even if the angle θ _sq is high, it is small compared to the difference between the Doppler frequency of the observation point C ₁ and the Doppler frequency of the central point 3 a of the observation area 3 .
Further _, among a plurality of points existing _on the ground range line GRL _, the difference between the Doppler frequency of the point R3 corresponding to the range cell of the pulse signal of the observation point C3 and the Doppler frequency of the observation point C3 is , the squint angle _.theta.sq increases and the amount of change in frequency displacement becomes steep, the difference is small compared to the difference between the Doppler frequency at the observation point C3 and the Doppler frequency at the center point 3a of the observation area _3. FIG.
Therefore, for the pulse signal at the observation point C1, if _phase compensation is performed based on the distance between the point _R1 and the center point 1a of the synthetic aperture 1, the center point 3a of the observation area 3 and the center of the synthetic aperture 1 Based on the distance from the point 1a, the displacement difference amount of the Doppler frequency becomes smaller than when phase compensation is performed.
In addition, for the pulse signal at the observation point C3 _, if phase compensation is performed based on the distance between the point R3 and the center point 1a of the synthetic aperture 1, the center point 3a of the observation area ₃ and the center of the synthetic aperture 1 Based on the distance from the point 1a, the displacement difference amount of the Doppler frequency becomes smaller than when phase compensation is performed.

Next, the operation of the radar device shown in FIG. 1 will be described.
FIG. 7 is a flowchart showing a radar signal processing method, which is a processing procedure of the radar signal processing device 40. As shown in FIG.
The pulse signal generator 11 of the signal generation section 10 generates a pulse signal and outputs the pulse signal to the multiplication section 22 of the analog circuit section 20 .

The oscillation section 21 of the analog circuit section 20 oscillates a carrier wave.
The oscillator 21 outputs carrier waves to the

multipliers

22 and 26, respectively.
Upon receiving the pulse signal from the pulse signal generator 11, the multiplier 22 multiplies the pulse signal by the carrier wave to up-convert the frequency of the pulse signal.
The multiplier 22 outputs the up-converted pulse signal to the amplifier 23 .
The amplifying unit 23 amplifies the up-converted pulse signal output from the multiplying unit 22 and outputs the amplified pulse signal to the switching unit 24 .

The switching unit 24 outputs the amplified pulse signal output from the amplifying unit 23 to the antenna unit 30 .
The antenna unit 30 radiates the pulse signal output from the switching unit 24 as a beam toward the observation area 3 .
A pulse signal emitted from the antenna section 30 is scattered by each observation point 2 included in the observation area 3 . The pulse signal after being scattered by each observation point 2 returns to the antenna section 30 .
The antenna unit 30 receives the pulse signal after scattering by each observation point 2 and outputs the pulse signal after scattering to the switching unit 24 as a received signal.
Switching section 24 outputs each received signal output from antenna section 30 to amplifying section 25 .

Amplifying section 25 amplifies each reception signal output from switching section 24 and outputs each amplified reception signal to multiplication section 26 .
Multiplying section 26, upon receiving each amplified received signal from amplifying section 25, multiplies each received signal by the carrier wave oscillated by oscillator 21, thereby down-converting the frequency of each received signal. .
Multiplying section 26 outputs each down-converted received signal to filtering section 27 .

The filter unit 27 suppresses out-of-band components contained in the down-converted received signals output from the multiplication unit 26, and outputs the out-of-band component-suppressed received signals to the A/D converter 28. Output.
When the A/D converter 28 receives the received signal after out-of-band component suppression from the filter unit 27, it converts the received signal from an analog signal to a digital signal s ₀ (n, h).
The A/D converter 28 outputs each digital signal s ₀ (n, h) to the digital signal storage section 13 .
n indicates the range cell number and h indicates the pulse number. The digital signal s ₀ (n,h) is expressed in range-hit dimensions.

The Fourier transform unit 42 of the radar signal processing device 40 acquires each digital signal s ₀ (n, h) from the digital signal storage unit 13 .
The Fourier transform unit 42 Fourier transforms each digital signal s ₀ (n, h) in the range direction (step ST1 in FIG. 7).
As means for Fourier transforming the digital signal s ₀ (n, h), the Fourier transform unit 42 can use FFT (Fast Fourier Transform). However, this is only an example, and the Fourier transform unit 42 may use, for example, DFT (Discrete Fourier Transform) to Fourier transform the digital signal s ₀ (n, h) in the range direction.
The Fourier transform unit 42 outputs each Fourier-transformed signal S ₀ (n, h) to the range compression unit 43 .

The range compression unit 43 acquires the signal S ₀ (n, h) after each Fourier transform from the Fourier transform unit 42 .
The range compression unit 43 multiplies each Fourier-transformed signal S ₀ (n, h) by a reference function G(n) for range compression, as shown in the following equation (1). The signal S ₀ (n, h) after the Fourier transform is range-compressed (step ST2 in FIG. 7). Since the reference function G(n) for range compression is a known function, detailed description thereof will be omitted.
The range compression unit 43 outputs the range-compressed signal S _comp (n, h) to the compensation processing unit 44 .

The compensation processing unit 44 acquires each of the range-compressed signals S _comp (n, h) from the range compression unit 43, and from the auxiliary information storage unit 12, platform trajectory information, observation geometry information, and Acquire radar specifications, etc.
Every time the compensation processing unit 44 acquires the range-compressed signal S _comp (n, h) from the range compression unit 43, based on the auxiliary information, the center point 3a of the observation region 3 and the center point of the synthetic aperture 1 Calculate the distance r ₀ (h) to 1a.
Here, for convenience of explanation, it is assumed that the coordinates of the central point 3a of the observation area 3 are [0, 0, 0]. A three-dimensional vector p(h) representing the coordinates of the center point 1a of the synthetic aperture 1 is obtained from the trajectory information of the platform or the like. The process of calculating the distance r ₀ (h) itself is a known technique, and detailed description thereof will be omitted.

The compensation processing unit 44 performs range cell migration compensation for each range-compressed signal S _comp (n, h) based on the distance r ₀ (h), as shown in the following equation (2) (Fig. 7 step ST3). By performing range cell migration compensation for each range-compressed signal S _comp (n, h), all hits are compensated so that the range cells of the same observation target 2 are located in the same range cells.
The compensation processing unit 44 outputs the migration-compensated signals S _mig (n, h) to the inverse Fourier transform unit 45 .

In equation (2), f(n) is the range frequency of the signal S _comp (n,h) after range compression, and c is the speed of light.

In the radar signal processing device 40 shown in FIG. 3, the compensation processing unit 44 performs range cell migration compensation using the center point 3a of the observation area 3 as a reference. However, this is only an example, and the compensation processing unit 44 may perform range cell migration compensation using a point other than the center point 3a of the observation area 3 as a reference.

The inverse Fourier transform unit 45 acquires the migration-compensated signals S _mig (n, h) from the compensation processing unit 44 .
The inverse Fourier transform unit 45 inverse Fourier transforms the migration-compensated signals S _mig (n, h) in the range direction (step ST4 in FIG. 7).
The inverse Fourier transform unit 45 can use IFFT (Inverse Fast Fourier Transform) as means for inverse Fourier transforming the migration-compensated signal S _mig (n, h). However, this is only an example, and the inverse Fourier transform unit 45 uses, for example, IDFT (Inverse Discrete Fourier Transform) to inverse Fourier transform each migration-compensated signal S _mig (n, h) in the range direction. You may make it
The inverse Fourier transform unit 45 outputs each signal s(n, h) after the inverse Fourier transform to the phase compensation unit 46 .

The phase compensator 46 acquires the signals s(n, h) after the respective inverse Fourier transforms from the inverse Fourier transform unit 45, and from the auxiliary information storage unit 12, platform trajectory information and observation geometric information as auxiliary information. and obtain radar specifications, etc.
The phase compensator 46 calculates the coordinates of the points corresponding to the range cells n of the signals s(n, h) after the inverse Fourier transform among the plurality of points existing on the ground range line GRL. Identify the vector p _g (n). The point corresponding to the range cell n of the signal s(n, h) after the inverse Fourier transform is, among a plurality of points present on the ground range line GRL, the signal s(n, h) after the inverse Fourier transform. h) is included in the isorange surface. For example, if the observation point is C1, the point corresponding to range cell _n is _R1 _, and if the observation point is C3 _, the point corresponding to range cell n is R3. A three-dimensional vector p _g (n) representing the coordinates of the point corresponding to range cell n is obtained from the auxiliary information.
The phase compensator 46 also identifies a three-dimensional vector p(h) representing the coordinates of the center point 1 a of the synthetic aperture 1 . The three-dimensional vector p(h) is obtained from platform trajectory information or the like.
The phase compensator 46 calculates the distance between the point corresponding to the range cell n of the signal s(n, h) after each inverse Fourier transform and the center point 1a of the synthetic aperture 1, as shown in the following equation (3). Calculate r(n,h).

The phase compensator 46 compensates the phase of each inverse Fourier transformed signal s(n, h) based on the distance r(n, h) as shown in the following equation (4) (FIG. 7 step ST5).
The phase compensator 46 outputs each phase-compensated signal s _ph (n, h) to the image generator 47 .

In equation (4), f _c is the center frequency of the signal s(n,h) after inverse Fourier transform.

The image generation unit 47 acquires the phase-compensated signals s _ph (n, h) from the phase compensation unit 46 .
The image generator 47 generates a DBS image S _dbs (n, h) by Fourier transforming each phase-compensated signal s _ph (n, h) in the azimuth direction (step ST6 in FIG. 7).
That is, the image generation unit 47 calculates the Doppler frequency of each observation point 2 by Fourier transforming each phase-compensated signal s _ph (n, h) in the azimuth direction, and calculates the Doppler frequency of each observation point 2 . Generate a DBS image S _dbs (n,h) showing the intensity of the Doppler frequency.
The image generation unit 47 outputs the DBS image S _dbs (n, h) to the DBS image storage unit 14 .
The DBS image S _dbs (n, h) stored in the DBS image storage unit 14 is displayed, for example, on a display (not shown).

The image generator 47 can use FFT as means for Fourier transforming the signal s _ph (n, h) after phase compensation. However, this is only an example, and the image generation unit 47 may use DFT to Fourier transform each phase-compensated signal s _ph (n, h) in the range direction.

In the first embodiment described above, the pulse signal acquisition unit 41 acquires the pulse signal after being scattered by each of the plurality of observation points included in the observation area 3 of the radar device, one point in the observation area 3, and the radar Each pulse signal obtained by the pulse signal obtaining unit 41 among a plurality of points existing on a projection line, which is a line projected onto the ground surface connecting a point in the synthetic aperture 1 of the apparatus. and a phase compensator 46 for compensating the phase of each pulse signal based on the distance between the point corresponding to the range cell and one point in the synthetic aperture 1. Therefore, the radar signal processing device 40 can reduce the number of observation points 2 having a Doppler frequency displacement difference amount larger than half the PRF.

Embodiment 2.
Embodiment 2 describes a radar signal processing device 40 in which a projection line is divided into a plurality of regions.
The configuration of the radar signal processing device 40 according to Embodiment 2 is the same as the configuration of the radar signal processing device 40 according to Embodiment 1, and the configuration diagram showing the radar signal processing device 40 according to Embodiment 2 is as follows: FIG.

FIG. 8 is an explanatory diagram showing a measurement example of the Doppler frequency of the ground surface including the observation area 3. In FIG.
In FIG. 8, the ground range line GRL, which is a projection line, is divided into M regions G ₁ to G _M . M is an integer of 2 or more. g _m (m=1, . . . , M) is a representative point among a plurality of points existing in the area G _m . The representative point _gm may be any point among a plurality of points existing in the area _Gm , but for example, a point located in the center of the area _Gm is used as the representative point _gm .
In the radar signal processing device 40 according to Embodiment 2, the phase compensator 46 determines that points corresponding to the range cells of the pulse signal after scattering by the respective observation points 2 in the M regions G ₁ to G _M are Identify the region G _m to which it belongs.
In FIG. 8, for example, if the observation _point is C1, the region to which the point corresponding to the range cell of the pulse signal belongs is identified as _GM , and if the observation point is C3 _, it corresponds to the range cell of the pulse signal. _G2 is identified as the region to which the points that _The representative point of the area G2 is _g2 , and the representative point of the area _GM is _gM .
The phase compensator 46 compensates the phase of the pulse signal based on the distance between the representative point _gm of each specified area _Gm and the central point 1a, which is one point in the synthetic aperture 1. FIG.

The phase compensation processing by the phase compensator 46 will be specifically described below.
The phase compensator 46 identifies a three-dimensional vector p _g ′(n) representing the coordinates of the representative point g _m of each identified region G _m . A three-dimensional vector p _g '(h) is obtained from the auxiliary information.
The phase compensator 46 calculates the distance r'( _n , _h ) between the representative point gm of each specified area Gm and the center point 1a of the synthetic aperture 1, as shown in the following equation (5). do.

The phase compensator 46 compensates the phase of each signal s(n, h) after the inverse Fourier transform based on the distance r'(n, h), as shown in Equation (6) below.
The phase compensator 46 outputs each phase-compensated signal s _ph (n, h) to the image generator 47 .

In the radar signal processing device 40 according to the second embodiment, as in the radar signal processing device 40 according to the first embodiment, the number of observation points 2 having a Doppler frequency displacement difference larger than half the PRF can be reduced. can be done.

It should be noted that the present disclosure allows free combination of each embodiment, modification of arbitrary constituent elements of each embodiment, or omission of arbitrary constituent elements in each embodiment.

The present disclosure is suitable for radar signal processing devices, radar signal processing methods, and radar devices.

1 Synthetic aperture 1a Center point 2 Observation point 3 Observation area 3a Center point 10 Signal generator 11 Pulse signal generator 12 Auxiliary information storage 13 Digital signal storage 14 DBS image storage 20 Analog circuit section, 21 oscillation section, 22 multiplication section, 23 amplification section, 24 switching section, 25 amplification section, 26 multiplication section, 27 filter section, 28 A/D converter, 30 antenna section, 40 radar signal processing device, 41 pulse signal acquisition unit, 42 Fourier transform unit, 43 range compression unit, 44 compensation processing unit, 45 inverse Fourier transform unit, 46 phase compensation unit, 47 image generation unit, 51 Fourier transform circuit, 52 range compression circuit, 53 compensation processing circuit, 54 inverse Fourier transform circuit, 55 phase compensation circuit, 56 image generation circuit, 61 memory, 62 processor.

Claims

a pulse signal acquisition unit that acquires a pulse signal after being scattered by each of a plurality of observation points included in an observation area of the radar device;
The pulse signal is obtained from among a plurality of points existing on a projection line, which is a line connecting one point in the observation area and one point in the synthetic aperture of the radar device, which is a line projected onto the ground surface. A radar signal processing apparatus comprising .
wherein the projection line is divided into a plurality of regions;
The phase compensator is
Among the plurality of regions, the region to which the point corresponding to the range cell of each pulse signal belongs is specified, and based on the distance between the representative point of each specified region and one point in the synthetic aperture, each 2. The radar signal processing device according to claim 1, wherein the phase of the pulse signal is compensated.
The radar signal processing apparatus according to claim 1, wherein one point within the observation area is the center point of the observation area, and one point within the synthetic aperture is the center point of the synthetic aperture.
The radar signal processing apparatus according to claim 1, further comprising an image generation section that generates an image by Fourier transforming the pulse signals after phase compensation by the phase compensation section in the azimuth direction.
The pulse signal acquisition unit is
a Fourier transform unit that Fourier transforms the pulse signal after scattering by each observation point in the range direction;
a compensation processing unit that performs range cell migration compensation for each signal after the Fourier transform by the Fourier transform unit;
Each signal after compensation by the compensation processing unit is subjected to inverse Fourier transform in the range direction, and each signal after inverse Fourier transform is output to the phase compensation unit as each pulse signal obtained by the pulse signal obtaining unit. 2. The radar signal processing apparatus according to claim 1, further comprising an inverse Fourier transform unit for performing
A pulse signal acquisition unit acquires a pulse signal after scattering by each of a plurality of observation points included in an observation area of the radar device,
Among a plurality of points where the phase compensating unit is located on a projection line, which is a line that connects one point in the observation area and one point in the synthetic aperture of the radar device and is a line projected onto the ground surface. and compensating the phase of each pulse signal based on the distance between the point corresponding to the range cell of each pulse signal acquired by the pulse signal acquisition unit and one point within the synthetic aperture.
A radar device comprising the radar signal processing device according to any one of claims 1 to 5.