Radar Echo Frequency Domain Simulation and Imaging Method, Medium and Device

Abstract

The present invention relates to the technical field of radar digital signal processing, specifically to a method, medium and device for radar echo frequency domain simulation and imaging. The method for radar echo frequency domain simulation and imaging includes the following steps: calculating a backscattering coefficient matrix in combination with a surface digital map; calculating the coordinates of satellite orbit azimuth sampling points in combination with the satellite operation orbit and the coordinates of the point on the satellite orbit closest to the scene center; obtaining the baseband echo signal of the spaceborne synthetic aperture radar using an inverse echo generation method; and processing with an imaging algorithm to obtain the spaceborne synthetic aperture radar image. The present invention can reduce the computational complexity of generating synthetic aperture radar echo signals in an extended scene, and improve the efficiency and accuracy of synthetic aperture radar echo generation and imaging.

Description

Technical Field

[0001] The present invention relates to the technical field of radar digital signal processing, and specifically to a method, medium and device for radar echo frequency domain simulation and imaging. Background Art

[0002] Synthetic Aperture Radar (SAR) has the characteristics of all-weather, all-day, high resolution, strong penetration, etc. As an active remote sensing technology, spaceborne SAR continuously emits electromagnetic signals through an antenna, and receives the echo after interacting with ground objects to obtain ground object information. Its mapping bandwidth is wide, stability is high, and it is not controlled by territorial sovereignty, so it has broad application prospects.

[0003] Through computer simulation technology, spaceborne SAR echo data can be simulated to obtain a SAR image close to the real one, which can be used to view ground terrain features, detect changes in land use, etc. Spaceborne SAR simulation technology plays an indispensable role in aspects such as theoretical research, system design, and effect evaluation of spaceborne SAR systems.

[0004] In spaceborne SAR simulation technology, SAR echo simulation is the key to improving SAR simulation efficiency and SAR imaging quality. Commonly used algorithms include time domain algorithms, one-dimensional fast Fourier transform algorithms, two-dimensional frequency domain fast Fourier transform algorithms, etc. Among them, time domain algorithms and one-dimensional fast Fourier transform algorithms have slow simulation speed and long time consumption, while the two-dimensional frequency domain fast Fourier transform algorithm, although improving the simulation speed to a certain extent, ignores the influence of motion errors and has great limitations in practical applications. Summary of the Invention

[0005] In order to solve the problems in the related technologies, the present invention provides a method, medium and device for radar echo frequency domain simulation and imaging, which can reduce the computational complexity of generating synthetic aperture radar echo signals in an extended scenario, and improve the efficiency and accuracy of synthetic aperture radar echo generation and imaging.

[0006] To solve the above problems, the following technical solutions are provided:

[0007] The radar of the present invention is a spaceborne synthetic aperture radar, and the radar echo frequency domain simulation and imaging system includes:

[0008] A backscattering coefficient matrix generation module, configured to calculate the backscattering coefficient matrix of the target scene in combination with the surface digital map;

[0009] Satellite orbit simulation module, which calculates the coordinate position of the satellite in the Earth-centered Earth-fixed coordinate system according to the six orbital elements of the satellite, obtains the satellite's operating orbit, and according to the Earth-centered Earth-fixed coordinates of the scene center, obtains the coordinates of the point on the satellite orbit closest to the scene center. Combining the satellite's operating orbit and the coordinates of the point on the satellite orbit closest to the scene center, calculates the coordinates of the sampling points in the azimuth direction of the satellite orbit;

[0010] Spaceborne synthetic aperture radar echo fast generation module, which is connected to the backscattering coefficient matrix generation module and the satellite orbit simulation module, is used to receive the backscattering coefficient matrix calculated by the backscattering coefficient matrix generation module, and based on the coordinates of the sampling points in the azimuth direction of the satellite orbit, uses the inverse echo generation method to obtain the baseband echo signal of the spaceborne synthetic aperture radar;

[0011] Spaceborne synthetic aperture radar imaging processing module, which is connected to the satellite orbit simulation module and the spaceborne synthetic aperture radar echo fast generation module, calculates the equivalent velocity and equivalent squint angle based on the coordinates of the sampling points in the azimuth direction of the satellite orbit, transforms the baseband echo signal of the spaceborne synthetic aperture radar into the two-dimensional frequency domain through two-dimensional fast Fourier transform, and uses imaging algorithm for processing, and obtains the spaceborne synthetic aperture radar image through inverse two-dimensional fast Fourier transform.

[0012] In the above solution, the backscattering coefficient matrix of the target scene is calculated through the surface digital map of the target scene, the satellite orbit is simulated by combining the coordinates of the closest point to the scene center and the six orbital elements, the coordinates of the sampling points in the azimuth direction of the satellite orbit are calculated, and the inverse echo generation method is used to reduce the computational complexity and improve the echo calculation efficiency. Combining with the GPU device to quickly calculate the baseband echo signal of the spaceborne synthetic aperture radar, it can realize the real-time generation of the echo of the spaceborne synthetic aperture radar for an extended scene, and use imaging algorithm to process the baseband echo signal of the spaceborne synthetic aperture radar to obtain the spaceborne synthetic aperture radar image, realizing the full-link simulation of the spaceborne synthetic aperture radar simulation technology from echo to imaging, thus solving the problems of high computational complexity in generating the synthetic aperture radar echo signal in an extended scene, low efficiency and low accuracy in synthetic aperture radar echo generation and imaging.

[0013] The operating method of radar echo frequency domain simulation and imaging is as follows, including the following steps:

[0014] S1: Through the backscattering coefficient matrix generation module, classify the targets according to the pixel blocks representing the ground objects in the surface digital map, set the backscattering coefficient amplitudes corresponding to different medium target objects, select the target scene area, calculate the backscattering coefficient matrix of the target scene, and transmit it to the spaceborne synthetic aperture radar echo fast generation module;

[0015] S2: The satellite orbit simulation module calculates the coordinate position of the satellite in the Earth-centered Earth-fixed coordinate system according to the six orbital elements of the satellite to obtain the satellite's operating orbit. Based on the Earth-centered Earth-fixed coordinates of the scene center and the distance from the scene center to the orbit, the coordinates of the point on the satellite orbit closest to the scene center are obtained. According to the number of azimuth sampling times and the azimuth sampling time interval, the azimuth sampling point coordinates of the satellite orbit are obtained;

[0016] S3: The on-board synthetic aperture radar echo fast generation module receives the backscattering coefficient matrix and preprocesses it. The point target frequency response function at the reference distance is calculated through the azimuth sampling point coordinates of the satellite orbit. The preprocessed backscattering coefficient matrix is transformed to the two-dimensional frequency domain through two-dimensional fast Fourier transform, multiplied by the point target frequency response function at the reference distance, to obtain the two-dimensional spectrum of the on-board synthetic aperture radar echo signal. The two-dimensional inverse fast Fourier transform is performed on the two-dimensional spectrum of the on-board synthetic aperture radar echo signal to obtain the on-board synthetic aperture radar baseband echo signal;

[0017] S4: The on-board synthetic aperture radar imaging processing module receives the on-board synthetic aperture radar baseband echo signal. Based on the azimuth sampling point coordinates of the satellite orbit, it uses an imaging algorithm to calculate the equivalent velocity and equivalent squint angle of the satellite. The on-board synthetic aperture radar baseband echo signal is transformed to the two-dimensional frequency domain through two-dimensional fast Fourier transform. Through multiplication by the reference function and complementary focusing, finally, the on-board synthetic aperture radar image is obtained through two-dimensional inverse fast Fourier transform.

[0018] In the above solution, by combining the digital map, satellite orbit, and radar echo frequency domain simulation and imaging algorithm, a full-link simulation method is constructed, which can not only realize the multi-mode on-board synthetic aperture radar echo frequency domain simulation, but also realize the on-board synthetic aperture radar imaging of the target scene under different satellite orbits, achieving the full-link simulation of the multi-mode on-board synthetic aperture radar from echo generation to imaging processing.

[0019] Calculating the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system in S2 ,

[0020] S2-1. The process of calculating the coordinates of the satellite in the Earth-centered orbital plane coordinate system is as follows:

[0021] ,

[0022] S2-2. Based on calculated in S2-1, the process of calculating the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system is as follows:

[0023] ,

[0024] Among them, represents the coordinates of the satellite in the geocentric orbital plane coordinate system; is the semi-major axis of the orbit; is the orbital eccentricity; is the true anomaly; represents the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system; represents the right ascension of the ascending node; represents the orbital inclination; is the argument of perigee.

[0025] The distance from the scene center to the orbit in S2 is:

[0026] ,

[0027] Among them, represents the Earth-centered Earth-fixed coordinates of the scene center; represents the Earth-centered Earth-fixed coordinates of the satellite orbit.

[0028] In S3, the backscattering coefficient matrix is preprocessed to obtain the preprocessed extended scene scattering coefficient matrix The calculation process is as follows:

[0029] ,

[0030] Among them represents the extended scene scattering coefficient matrix, is the range-time, represents the azimuth-time, represents the reference range, which is the distance from the scene center to the center of the azimuth sampling points of the satellite orbit, represents the speed of light, represents the preprocessed extended scene scattering coefficient matrix.

[0031] The point target frequency response function at the reference range in S3 is:

[0032] ,

[0033] ,

[0034] Among them, represents the point target response function at the reference range; represents the two-dimensional fast Fourier transform operation; is the range-time; represents the azimuth-time; represents the reference range; Indicates the distance from the scene center to the azimuth sampling points on the satellite orbit; is the pulse envelope, approximately a rectangular window function, represents the range pulse envelope, represents the azimuth pulse envelope; represents the speed of light; represents the zero Doppler time; is the range chirp rate; represents the center frequency of the transmitted pulse.

[0035] In S3, the two-dimensional inverse fast Fourier transform is performed on the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal to obtain the spaceborne synthetic aperture radar baseband echo signal The calculation process is:

[0036] ,

[0037] where, represents the spaceborne synthetic aperture radar baseband echo signal; the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal; represents the two-dimensional inverse fast Fourier transform.

[0038] The equivalent velocity and the equivalent squint angle in S4 are calculated as follows:

[0039] ,

[0040] ,

[0041] where, represents the equivalent velocity; represents the equivalent squint angle; represents the radar wavelength; represents the Doppler center frequency; represents the reference range; represents the first Doppler modulation rate.

[0042] The calculation process of transforming the spaceborne synthetic aperture radar baseband echo signal into the two-dimensional frequency domain is:

[0043] ,

[0044] where, represents the spaceborne synthetic aperture radar baseband echo signal; represents the two-dimensional fast Fourier transform.

[0045] The reference function is set as:

[0046] ,

[0047] Among them, represents the reference distance; represents the speed of light; represents the carrier frequency; represents the equivalent speed; represents the range modulation frequency.

[0048] By using Stolt interpolation to change the range - frequency axis, mapping the original range - frequency to the new range - frequency , it can be expressed as:

[0049] ,

[0050] Using the two - dimensional inverse fast Fourier transform for the signal after Stolt interpolation, the spaceborne synthetic aperture radar image is calculated as:

[0051] ,

[0052] Among them, represents the spaceborne synthetic aperture radar image; represents the two - dimensional inverse fast Fourier transform; represents the signal after Stolt interpolation.

[0053] The radar echo frequency - domain simulation and imaging medium stores a computer program, and the radar echo frequency - domain simulation and imaging method implemented when the computer program is executed by a processor.

[0054] The radar echo frequency - domain simulation and imaging device includes a memory, a processor, and a computer program stored on the memory and executable on the processor.

[0055] Adopting the above - mentioned scheme, there are the following specific advantages:

[0056] 1. Since the present invention calculates the backscattering coefficient matrix of the target scene through the surface digital map of the target scene, combines the coordinates of the nearest point to the scene center and the six orbital elements to simulate the satellite orbit, calculates the coordinates of the azimuth sampling points of the satellite orbit, uses the inverse echo generation method, reduces the computational complexity, improves the echo calculation efficiency, combines the GPU device to quickly calculate the spaceborne synthetic aperture radar baseband echo signal, can realize the real - time generation of the extended - scene spaceborne synthetic aperture radar echo, and uses the imaging algorithm to process the spaceborne synthetic aperture radar baseband echo signal to obtain the spaceborne synthetic aperture radar image, realizing the full - link simulation of the spaceborne synthetic aperture radar simulation technology from echo to imaging, which can reduce the computational complexity of generating the synthetic aperture radar echo signal in the extended - scene, and improve the efficiency and accuracy of the synthetic aperture radar echo generation and imaging.

[0057] 2. By combining digital maps, satellite orbits, and radar echo frequency domain simulation and imaging algorithms, a full-link simulation method is constructed, which can not only achieve multi-mode spaceborne synthetic aperture radar echo frequency domain simulation, but also realize spaceborne synthetic aperture radar imaging of target scenes under different satellite orbits, achieving full-link simulation of multi-mode spaceborne synthetic aperture radar from echo generation to imaging processing.

[0058] 3. The present invention adopts an inverse echo generation method, which improves the problem of high computational complexity of traditional time domain algorithms and one-dimensional fast Fourier transform algorithms, improves the computational efficiency of echoes, and considers the influence of motion errors compared with traditional two-dimensional frequency domain fast Fourier transform algorithms, improving the computational accuracy.

[0059] 4. The present invention combines GPU parallel computing with spaceborne synthetic aperture radar echo simulation and imaging processes, enabling real-time generation of spaceborne synthetic aperture radar echo signals in extended scenarios and improving the efficiency of spaceborne synthetic aperture radar imaging in extended scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to specific embodiments of the present invention in combination with the drawings, where:

[0061] Figure 1 is the flowchart of the radar echo frequency domain simulation and imaging method;

[0062] Figure 2 is the simulation result diagram of the spaceborne synthetic aperture radar sliding spotlight mode point target echo using the method of the present invention;

[0063] Figure 3 is the imaging result diagram of the spaceborne synthetic aperture radar sliding spotlight mode point target using the method of the present invention;

[0064] Figure 4 is Figure 2 the enlarged view of part A in

[0065] Figure 5 is the simulation result diagram of the spaceborne synthetic aperture radar spotlight mode extended scenario echo using the method of the present invention;

[0066] Figure 6 is the imaging result diagram of the spaceborne synthetic aperture radar spotlight mode extended scenario using the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0067] Next, in conjunction with the accompanying drawings of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0068] In a specific embodiment 1, as Figure 1 shown, the radar of the present invention is a spaceborne synthetic aperture radar, and the radar echo frequency domain simulation and imaging system includes:

[0069] A backscattering coefficient matrix generation module, configured to calculate the backscattering coefficient matrix of the target scene in combination with the digital terrain map.

[0070] A satellite orbit simulation module, which calculates the coordinate position of the satellite in the Earth-centered Earth-fixed coordinate system according to the six orbital elements of the satellite to obtain the satellite's operating orbit, and obtains the coordinates of the point on the satellite orbit closest to the scene center according to the Earth-centered Earth-fixed coordinates of the scene center. Combining the satellite's operating orbit and the coordinates of the point on the satellite orbit closest to the scene center, the coordinate of the sampling point in the azimuth direction of the satellite orbit is calculated.

[0071] A spaceborne synthetic aperture radar echo fast generation module, connected to the backscattering coefficient matrix generation module and the satellite orbit simulation module, is configured to receive the backscattering coefficient matrix calculated by the backscattering coefficient matrix generation module, and based on the coordinate of the sampling point in the azimuth direction of the satellite orbit, use the inverse echo generation method to obtain the baseband echo signal of the spaceborne synthetic aperture radar.

[0072] A spaceborne synthetic aperture radar imaging processing module, connected to the satellite orbit simulation module and the spaceborne synthetic aperture radar echo fast generation module, calculates the equivalent velocity and equivalent squint angle based on the coordinate of the sampling point in the azimuth direction of the satellite orbit, transforms the baseband echo signal of the spaceborne synthetic aperture radar to the two-dimensional frequency domain through two-dimensional fast Fourier transform, and uses an imaging algorithm for processing, and obtains the spaceborne synthetic aperture radar image through inverse two-dimensional fast Fourier transform.

[0073] The operation method of the radar echo frequency domain simulation and imaging is as follows, including the following steps:

[0074] S1: Through the backscattering coefficient matrix generation module, classify the target according to the pixel blocks representing the ground object targets in the digital terrain map, set the amplitude of the backscattering coefficient corresponding to different medium target objects, select the target scene area, calculate the backscattering coefficient matrix of the target scene, and transmit it to the spaceborne synthetic aperture radar echo fast generation module.

[0075] S2: S2-1. Calculate the coordinate position of the satellite in the Earth-Centered Earth-Fixed (ECEF) coordinate system based on the six orbital elements of the satellite orbit through the satellite orbit simulation module, and obtain the satellite's operating orbit.

[0076] Calculate the coordinates of the satellite in the Earth-Centered Earth-Fixed coordinate system ,

[0077] The process of calculating the coordinates of the satellite in the geocentric orbital plane coordinate system is as follows: The process is:

[0078] ,

[0079] Based on the coordinates of the satellite in the geocentric orbital plane coordinate system , and the coordinates of the satellite in the Earth-Centered Earth-Fixed coordinate system The calculation process is as follows:

[0080] ,

[0081] Among them, represents the coordinates of the satellite in the geocentric orbital plane coordinate system; is the semi-major axis of the orbit; is the eccentricity of the orbit; is the true anomaly; represents the coordinates of the satellite in the Earth-Centered Earth-Fixed coordinate system; represents the right ascension of the ascending node; represents the orbital inclination; is the argument of perigee.

[0082] S2-2. Obtain the coordinates of the point on the satellite orbit closest to the scene center based on the Earth-Centered Earth-Fixed coordinates of the scene center and the distance from the scene center to the orbit.

[0083] The distance from the scene center to the orbit is:

[0084] ,

[0085] Among them, represents the Earth-Centered Earth-Fixed coordinates of the scene center; represents the Earth-Centered Earth-Fixed coordinates of the satellite orbit.

[0086] S2-3. Obtain the azimuth sampling point coordinates of the satellite orbit based on the number of azimuth sampling times and the azimuth sampling time interval.

[0087] S3: The spaceborne synthetic aperture radar echo fast generation module receives the backscattering coefficient matrix and performs preprocessing on the backscattering coefficient matrix. The calculation process of the preprocessing is as follows:

[0088] ,

[0089] Among them denotes the extended scene scattering coefficient matrix, is the range time, denotes the azimuth time, denotes the reference range, which is the distance from the scene center to the center of the azimuth sampling points on the satellite orbit, denotes the speed of light, denotes the preprocessed extended scene scattering coefficient matrix;

[0090] The preprocessed backscattering coefficient matrix is transformed to the two-dimensional frequency domain by two-dimensional fast Fourier transform and multiplied by the point target frequency response function at the reference range to obtain the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal, where the point target frequency response function at the reference range is:

[0091] ,

[0092] ,

[0093] where, denotes the point target response function at the reference range; denotes the two-dimensional fast Fourier transform operation; is the range time; denotes the azimuth time; denotes the reference range; denotes the distance from the scene center to the azimuth sampling points on the satellite orbit; is the pulse envelope, approximately a rectangular window function, denotes the range pulse envelope, denotes the azimuth pulse envelope; denotes the speed of light; denotes the zero Doppler time; is the range frequency modulation slope; denotes the center frequency of the transmitted pulse;

[0094] The two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal is subjected to two-dimensional inverse fast Fourier transform to obtain the spaceborne synthetic aperture radar baseband echo signal The calculation process of

[0095] ,

[0096] where, denotes the spaceborne synthetic aperture radar baseband echo signal; the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal; denotes the two-dimensional inverse fast Fourier transform.

[0097] S4: The spaceborne synthetic aperture radar imaging processing module receives the spaceborne synthetic aperture radar baseband echo signal. Based on the satellite orbit azimuth sampling point coordinates, using the imaging algorithm, calculate the equivalent velocity and equivalent squint angle of the satellite. The calculation formula for the equivalent velocity and equivalent squint angle of the satellite is:

[0098] ,

[0099] ,

[0100] where, represents the equivalent velocity; represents the equivalent squint angle; represents the radar wavelength; represents the Doppler center frequency; represents the reference distance; represents the first-order Doppler frequency modulation rate.

[0101] Transform the spaceborne synthetic aperture radar baseband echo signal to the two-dimensional frequency domain through two-dimensional fast Fourier transform. The calculation formula for the two-dimensional spectrum of the spaceborne synthetic aperture radar baseband echo signal is:

[0102] ,

[0103] where, represents the spaceborne synthetic aperture radar baseband echo signal; represents the two-dimensional fast Fourier transform.

[0104] Through multiplying by the reference function and complementary focusing, the reference function is set as:

[0105] ,

[0106] where, represents the reference distance; represents the speed of light; represents the carrier frequency; represents the equivalent velocity; represents the range frequency modulation rate.

[0107] Change the range frequency axis through Stolt interpolation, and map the original range frequency to the new range frequency , which can be expressed as:

[0108] ,

[0109] Finally, use the two-dimensional inverse fast Fourier transform for the signal after Stolt interpolation to calculate the spaceborne synthetic aperture radar image as:

[0110] ,

[0111] Among them, represents the spaceborne synthetic aperture radar image; represents the two-dimensional inverse fast Fourier transform; represents the signal after Stolt interpolation.

[0112] In a specific embodiment 2, the difference between this embodiment and embodiment 1 is that this embodiment also discloses a radar echo frequency domain simulation and imaging medium, which stores a computer program, and the radar echo frequency domain simulation and imaging method implemented when the computer program is executed by a processor.

[0113] In a specific embodiment 3, the difference between this embodiment and embodiment 1 is that this embodiment also discloses a radar echo frequency domain simulation and imaging device, including a memory, a processor, and a computer program stored on the memory and executable on the processor.

[0114] The present invention combines GPU parallel computing with the process of spaceborne synthetic aperture radar echo simulation and imaging, and can realize the real-time generation of spaceborne synthetic aperture radar echo signals in an extended scenario, improving the efficiency of spaceborne synthetic aperture radar imaging in the extended scenario.

[0115] Using the method of the present invention to perform spaceborne synthetic aperture radar echo simulation and imaging processing on a point target, set the working mode of the spaceborne synthetic aperture radar to the sliding spotlight mode, let the point target be located at 32° north latitude and 120° east longitude on the earth's surface, and set it as the reference point, calculate the coordinates of the point closest to the target on the orbit, obtain the satellite azimuth point sampling point coordinates, select the sliding spotlight rotation point on the extension line of the connection between the reference point and the satellite orbit center, and its distance to the satellite orbit center is 1.01 times the distance from the reference point to the orbit center. Through the inverse echo generation method, quickly obtain the point target echo signal. The simulation result of the point target echo in the spaceborne SAR sliding spotlight mode is as Figure 2 shown. Using the imaging algorithm to process the echo signal to obtain the spaceborne synthetic aperture radar image. The imaging result of the point target echo is as Figure 3 , 4 shown.

[0116] Secondly, use the method of the present invention to perform spaceborne synthetic aperture radar echo simulation and imaging processing on an extended scenario. Set the working mode of the spaceborne synthetic aperture radar to the spotlight mode, select the center of the field target scene as the reference point, and calculate the spaceborne synthetic aperture radar echo in the spotlight mode of the selected area through the inverse echo generation method, as Figure 5 shown. Using the imaging algorithm to process the extended scenario echo signal to obtain the spaceborne synthetic aperture radar image in the spotlight mode, asFigure 6 as shown

[0117] It can be seen from the experimental results that the present invention can perform full-link simulation on the echoes and imaging of multi-mode spaceborne synthetic aperture radar, is applicable to real-time applications in extended scenarios, and can improve the simulation efficiency of spaceborne synthetic aperture radar.

[0118] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, based on the above description, other different forms of changes or variations can be made. It is not necessary and impossible to enumerate all the implementation manners here, and the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A radar echo frequency domain simulation and imaging method, wherein the radar is a spaceborne synthetic aperture radar, characterized in that: The method is as follows, comprising the following steps: S1: The backscatter coefficient matrix generation module classifies the targets according to the pixel blocks representing the ground objects in the surface digital map, sets the backscatter coefficient amplitudes corresponding to the target objects of different media, selects the target scene area, calculates the backscatter coefficient matrix of the target scene, and transmits it to the spaceborne synthetic aperture radar echo fast generation module; S2: The satellite orbit simulation module calculates the coordinate position of the satellite in the geocentric earth-fixed coordinate system according to the six satellite orbit numbers to obtain the satellite orbit. The coordinates of the closest point of the satellite orbit to the scene center are obtained according to the geocentric earth-fixed coordinates of the scene center and the distance from the scene center to the orbit. The coordinates of the azimuth sampling point of the satellite orbit are obtained according to the azimuth sampling number and the azimuth sampling time interval. S3: The spaceborne synthetic aperture radar echo fast generation module receives the backscatter coefficient matrix and preprocesses the backscatter coefficient matrix, calculates the frequency response function of the point target at the reference distance through the satellite orbit azimuth sampling point coordinates, transforms the preprocessed backscatter coefficient matrix into the two-dimensional frequency domain through the two-dimensional fast Fourier transform, multiplies it by the frequency response function of the point target at the reference distance, obtains the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal, performs two-dimensional fast Fourier inverse transform on the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal, and obtains the baseband echo signal of the spaceborne synthetic aperture radar; S4: The spaceborne synthetic aperture radar imaging processing module receives the baseband echo signal of the spaceborne synthetic aperture radar and uses the sampling point coordinates based on the satellite orbit azimuth. The imaging algorithm calculates the satellite equivalent velocity and equivalent slant angle, transforms the baseband echo signal of the spaceborne synthetic aperture radar into the two-dimensional frequency domain through the two-dimensional fast Fourier transform, multiplies by the reference function, complements the focusing, and finally obtains the spaceborne synthetic aperture radar image through the two-dimensional inverse fast Fourier transform.

2. The radar echo frequency domain simulation and imaging method according to claim 1, characterized in that: S2 calculates the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system , S2-1, calculate the coordinates of the satellite in the geocentric orbital plane coordinate system The process is: ， S2-2, calculated based on S2-1 , the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system The calculation process is: ， in, Represents the coordinates of the satellite in the geocentric orbital plane coordinate system; is the semi-major axis of the orbit; is the orbital eccentricity; is the true anomaly angle; It represents the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system; represents the right ascension of the ascending node; represents the orbital inclination; is the argument of perigee.

3. The radar echo frequency domain simulation and imaging method according to claim 1, characterized in that: The distance from the center of the scene to the track in S2 is: ， in, The Earth-fixed coordinates representing the center of the scene; Represents the Earth-centered, Earth-fixed coordinates of the satellite's orbit.

4. The radar echo frequency domain simulation and imaging method according to claim 1, characterized in that: Backscattering coefficient matrix in S3 Perform preprocessing to obtain the preprocessed extended scene scattering coefficient matrix The calculation process is: ， in represents the extended scene scattering coefficient matrix, is the distance to time, Indicates the direction and time, Indicates the reference distance, which is the distance from the center of the scene to the center of the sampling point in the satellite orbit. represents the speed of light, Represents the preprocessed extended scene scattering coefficient matrix.

5. The radar echo frequency domain simulation and imaging method according to claim 1, characterized in that: Frequency response function of point target at reference distance in S3 for: ， ， in, represents the point target response function at the reference distance; Represents a two-dimensional fast Fourier transform operation; For distance to time; Indicates direction and time; Indicates the reference distance; Indicates the distance from the scene center to the sampling point in the satellite orbit azimuth; is the pulse envelope, which is approximately a rectangular window function, represents the range pulse envelope, Indicates the azimuth pulse envelope; represents the speed of light; represents zero Doppler time; is the range frequency modulation slope; Indicates the center frequency of the transmitted pulse.

6. The radar echo frequency domain simulation and imaging method according to claim 1, characterized in that: In S3, the two-dimensional fast Fourier inverse transform is performed on the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal to obtain the baseband echo signal of the spaceborne synthetic aperture radar. The calculation process is: ， in, Represents the baseband echo signal of the spaceborne synthetic aperture radar; Two-dimensional spectrum of spaceborne synthetic aperture radar echo signal; Represents the two-dimensional inverse fast Fourier transform.

7. The radar echo frequency domain simulation and imaging method according to claim 1, characterized in that: Equivalent speed of satellite in S4 and equivalent squint angle The calculation process is: ， ， in, represents the equivalent speed; represents the equivalent oblique angle; represents the radar wavelength; represents the Doppler center frequency; Indicates the reference distance; Indicates Doppler primary modulation frequency; The calculation process of transforming the baseband echo signal of the spaceborne synthetic aperture radar into the two-dimensional frequency domain is: ， in, Represents the baseband echo signal of the spaceborne synthetic aperture radar; represents the two-dimensional fast Fourier transform; The reference function is set as: ， in, Indicates the reference distance; represents the speed of light; Indicates the carrier frequency; represents the equivalent speed; Indicates the range modulation frequency; The distance-frequency axis is changed by Stolt interpolation, and the original distance-frequency Mapping to new distance frequency , which can be expressed as: ， Use the two-dimensional inverse fast Fourier transform to calculate the spaceborne synthetic aperture radar image on the signal after Stolt interpolation for: ， in, Represents a spaceborne synthetic aperture radar image; represents the two-dimensional inverse fast Fourier transform; Represents the signal after Stolt interpolation.

8. Radar echo frequency domain simulation and imaging medium, characterized in that: A computer program is stored, and when the computer program is executed by a processor, the processor is caused to perform the steps of the method according to claim 1.

9. Radar echo frequency domain simulation and imaging equipment, characterized in that: The device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. The device acquires a spaceborne synthetic aperture radar image by executing the method according to claim 1.

Images