Radar echo frequency domain simulation and imaging system, method, medium and equipment

Abstract

The invention relates to the technical field of radar digital signal processing, in particular to a radar echo frequency domain simulation and imaging system and method, a medium and equipment. The radar echo frequency domain simulation and imaging system comprises: a backscattering coefficient matrix generation module for calculating a backscattering coefficient matrix in combination with an earth surface digital map; the satellite orbit simulation module is used for calculating and obtaining satellite orbit azimuth sampling point coordinates by combining the satellite orbit and the coordinates of the point, closest to the scene center, of the satellite orbit; the spaceborne synthetic aperture radar echo rapid generation module obtains a spaceborne synthetic aperture radar baseband echo signal by using an inverse omega K echo generation method; and the spaceborne synthetic aperture radar imaging processing module is used for processing by adopting an omega K imaging algorithm to obtain a spaceborne synthetic aperture radar image. According to the method, the calculation complexity of generating the synthetic aperture radar echo signal in the extended scene can be reduced, and the efficiency and precision of synthetic aperture radar echo generation and imaging are improved.

Description

Technical Field

[0001] The present invention relates to the field of radar digital signal processing technology, in particular to a radar echo frequency domain simulation and imaging system, method, medium and equipment. Background Art

[0002] Synthetic Aperture Radar (SAR) has the characteristics of all-day, all-weather, high resolution and strong penetration. As an active remote sensing technology, satellite-borne SAR continuously transmits electromagnetic signals through antennas and receives echoes after interacting with ground objects to obtain ground information. It has a high surveying and mapping bandwidth and stability and is not controlled by airspace sovereignty, and has broad application prospects.

[0003] Computer simulation technology can be used to simulate spaceborne SAR echo data and obtain SAR images that are close to the real thing. This can be used to view ground terrain features, detect changes in land use, etc. Spaceborne SAR simulation technology plays an indispensable role in the 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. The more commonly used algorithms include time domain algorithm, one-dimensional fast Fourier transform algorithm, two-dimensional frequency domain fast Fourier transform algorithm, etc. Among them, the time domain algorithm and one-dimensional fast Fourier transform algorithm have slow simulation speed and take a long time. Although the two-dimensional frequency domain fast Fourier transform algorithm improves the simulation speed to a certain extent, it 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 art, the present invention provides a radar echo frequency domain simulation and imaging system, method, medium and device, which can reduce the computational complexity of generating synthetic aperture radar echo signals in extended scenarios and improve the efficiency and accuracy of synthetic aperture radar echo generation and imaging.

[0006] In order 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 comprises:

[0008] A backscatter coefficient matrix generation module is used to calculate the backscatter coefficient matrix of the target scene in combination with the digital map of the surface;

[0009] 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. According to the geocentric earth-fixed coordinates of the scene center, the coordinates of the satellite orbit closest to the scene center are obtained. Combining the satellite orbit and the coordinates of the satellite orbit closest to the scene center, the coordinates of the satellite orbit azimuth sampling point are calculated.

[0010] A spaceborne synthetic aperture radar echo fast generation module is connected to the backscatter coefficient matrix generation module and the satellite orbit simulation module, and is used to receive the backscatter coefficient matrix calculated by the backscatter coefficient matrix generation module, and obtain a spaceborne synthetic aperture radar baseband echo signal based on the sampling point coordinates in the azimuth direction of the satellite orbit by using an inverse ωK echo generation method;

[0011] The satellite-borne synthetic aperture radar imaging processing module is connected to the satellite orbit simulation module and the satellite-borne synthetic aperture radar echo rapid generation module, and calculates the equivalent speed and equivalent slant angle based on the coordinates of the satellite orbit azimuth sampling points, transforms the satellite-borne synthetic aperture radar baseband echo signal into the two-dimensional frequency domain through the two-dimensional fast Fourier transform, uses the ωK imaging algorithm for processing, and obtains the satellite-borne synthetic aperture radar image through the two-dimensional inverse fast Fourier transform.

[0012] In the above scheme, the backscatter coefficient matrix of the target scene is calculated through the surface digital map of the target scene, the coordinates of the nearest point in the center of the scene and the six orbital elements are combined to simulate the satellite orbit, the coordinates of the sampling points in the azimuth direction of the satellite orbit are calculated, and the inverse ωK echo generation method is used to reduce the calculation complexity and improve the echo calculation efficiency. The baseband echo signal of the satellite-borne synthetic aperture radar is quickly calculated in combination with the GPU device, so that the real-time generation of the satellite-borne synthetic aperture radar echo in the extended scene can be realized, and the baseband echo signal of the satellite-borne synthetic aperture radar is processed by the ωK imaging algorithm to obtain the satellite-borne synthetic aperture radar image, so as to realize the full-link simulation of the satellite-borne synthetic aperture radar simulation technology from echo to imaging, thereby solving the problems of complex calculation of generating synthetic aperture radar echo signals in extended scenarios, low efficiency and low precision of synthetic aperture radar echo generation and imaging.

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

[0014] 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;

[0015] 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.

[0016] 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;

[0017] S4: The satellite-borne synthetic aperture radar imaging processing module receives the satellite-borne synthetic aperture radar baseband echo signal, and based on the coordinates of the sampling point in the azimuth direction of the satellite orbit, uses the ωK imaging algorithm to calculate the satellite equivalent velocity and equivalent slant angle, and transforms the satellite-borne synthetic aperture radar baseband echo signal into the two-dimensional frequency domain through the two-dimensional fast Fourier transform. Finally, the satellite-borne synthetic aperture radar image is obtained through the two-dimensional inverse fast Fourier transform by multiplying the reference function and performing complementary focusing.

[0018] In the above scheme, a full-link simulation method is constructed by combining digital maps, satellite orbits, radar echo frequency domain simulation and imaging algorithms. It can not only realize the frequency domain simulation of multi-mode spaceborne synthetic aperture radar echoes, but also realize spaceborne synthetic aperture radar imaging of target scenes under different satellite orbits, realizing the full-link simulation of multi-mode spaceborne synthetic aperture radar from echo generation to imaging processing.

[0019] S2 calculates the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system (x eci ,y eci ,z eci ),

[0020] S2-1, the process of calculating the coordinates (x0, y0, z0) of the satellite in the geocentric orbital plane coordinate system is:

[0021]

[0022] S2-2, based on the (x0, y0, z0) calculated in S2-1, the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system (x eci ,y eci ,z eci )The calculation process is:

[0023]

[0024] Among them, (x0, y0, z0) represents the coordinates of the satellite in the geocentric orbital plane coordinate system; a is the semi-major axis of the orbit; e is the orbital eccentricity; f is the true anomaly; (x eci ,y eci ,z eci ) represents the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system; Ω represents the right ascension of the ascending node; i represents the orbital inclination; ω is the argument of perigee.

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

[0026]

[0027] Among them, (x sce ,y sce ,z sce ) represents the Earth-fixed coordinate of the center of the scene; (x sat ,y sat ,z sat ) represents the Earth-centered, Earth-fixed coordinates of the satellite orbit.

[0028] In S3, the backscattering coefficient matrix γ(t,η) is preprocessed to obtain the preprocessed extended scene scattering coefficient matrix γ ′ The calculation process of (t,η) is:

[0029]

[0030] Where γ(t,η) represents the extended scene scattering coefficient matrix, t is the distance time, η is the azimuth time, R ref represents the reference distance, represents the distance from the center of the scene to the center of the sampling point in the satellite orbit, c represents the speed of light, γ ′ (t,η) represents the extended scene scattering coefficient matrix after preprocessing.

[0031] The frequency response function of the point target at the reference distance in S3 h(t,η,R ref )for:

[0032] H(f t ,f η ,R ref )=FFT2[h(t,η,R ref )],

[0033]

[0034] Among them, h(t,η,R ref) represents the point target response function at the reference distance; FFT2[·] represents the two-dimensional fast Fourier transform operation; t is the time in the range direction; η represents the time in the azimuth direction; R ref represents the reference distance; R represents the distance from the scene center to the sampling point in the azimuth of the satellite orbit; w(·) is the pulse envelope, which is approximately a rectangular window function, w r represents the range pulse envelope, w a represents the azimuth pulse envelope; c represents the speed of light; η c represents zero Doppler time; K r is the range frequency modulation slope; f0 represents the center frequency of the transmitting pulse.

[0035] 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 calculation process of the spaceborne synthetic aperture radar baseband echo signal s(t,η):

[0036] s(t,η)=IFFT2[S 2df (f t ,f η )],

[0037] Where s(t,η) represents the baseband echo signal of the spaceborne synthetic aperture radar; S 2df (f t ,f η ) is the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal; IFFT2[·] represents the two-dimensional inverse fast Fourier transform.

[0038] The equivalent speed v of the satellite in S4 r and the equivalent slant angle θ sq The calculation process is:

[0039]

[0040] Among them, v r represents the equivalent speed; θ sq represents the equivalent squint angle; λ represents the radar wavelength; f dc represents the Doppler center frequency; R ref represents the reference distance; f 1r Indicates the Doppler primary modulation frequency.

[0041] The calculation process of transforming the baseband echo signal of the spaceborne synthetic aperture radar into the two-dimensional frequency domain is:

[0042] S 2df (f t ,f η ) = FFT2[s(t,η)],

[0043] Where s(t,η) represents the baseband echo signal of the spaceborne synthetic aperture radar; FFT2[·] represents the two-dimensional fast Fourier transform.

[0044] The reference function is set as:

[0045]

[0046] Among them, R ref represents the reference distance; c represents the speed of light; f0 represents the carrier frequency; v r Indicates equivalent speed; K r Indicates the distance modulation frequency.

[0047] The distance frequency axis is changed by Stolt interpolation, and the original distance frequency f t Mapped to a new distance frequency f ′ t , which can be expressed as:

[0048]

[0049] The spaceborne synthetic aperture radar image is calculated by using the two-dimensional inverse fast Fourier transform on the Stolt interpolated signal:

[0050] I SAR =IFFT2[S Stolt (f t ,f η )],

[0051] Among them, I SAR represents the spaceborne synthetic aperture radar image; IFFT2[·] represents the two-dimensional inverse fast Fourier transform; S Stolt (f t ,f η ) represents the signal after Stolt interpolation.

[0052] A radar echo frequency domain simulation and imaging medium stores a computer program, which implements a radar echo frequency domain simulation and imaging method when the computer program is executed by a processor.

[0053] A radar echo frequency domain simulation and imaging device comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor.

[0054] The above solution has the following advantages:

[0055] 1. 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 in the center of the scene and the six orbital elements to simulate the satellite orbit, calculates the coordinates of the sampling points in the azimuth direction of the satellite orbit, uses the inverse ωK echo generation method, reduces the calculation complexity, improves the echo calculation efficiency, combines the GPU device to quickly calculate the baseband echo signal of the satellite-borne synthetic aperture radar, can realize the real-time generation of the satellite-borne synthetic aperture radar echo of the extended scene, and uses the ωK imaging algorithm to process the satellite-borne synthetic aperture radar baseband echo signal to obtain the satellite-borne synthetic aperture radar image, realizes the full-link simulation of the satellite-borne synthetic aperture radar simulation technology from echo to imaging, can reduce the calculation complexity of generating the synthetic aperture radar echo signal in the extended scene, and improves the efficiency and accuracy of the synthetic aperture radar echo generation and imaging.

[0056] 2. By combining digital maps, satellite orbits, radar echo frequency domain simulation and imaging algorithms, a full-link simulation method is constructed, which can not only realize the frequency domain simulation of multi-mode spaceborne synthetic aperture radar echoes, but also realize spaceborne synthetic aperture radar imaging of target scenes under different satellite orbits, realizing the full-link simulation of multi-mode spaceborne synthetic aperture radar from echo generation to imaging processing.

[0057] 3. The present invention adopts an inverse ωK echo generation method, which improves the high computational complexity of traditional time domain algorithms and one-dimensional fast Fourier transform algorithms, improves the computational efficiency of echoes, and takes into account the influence of motion errors and improves the computational accuracy compared to traditional two-dimensional frequency domain fast Fourier transform algorithms.

[0058] 4. The present invention combines GPU parallel computing with satellite-borne synthetic aperture radar echo simulation and imaging process, which can realize real-time generation of satellite-borne synthetic aperture radar echo signals in extended scenarios, thereby improving the efficiency of satellite-borne synthetic aperture radar imaging in extended scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0060] Figure 1 It is a flow chart of radar echo frequency domain simulation and imaging method;

[0061] Figure 2 This is a diagram showing the simulation results of point target echoes in the sliding spotlight mode of a spaceborne synthetic aperture radar using the method of the present invention;

[0062] Figure 3 This is a diagram showing the imaging result of a point target in the sliding spotlight mode of a spaceborne synthetic aperture radar using the method of the present invention;

[0063] Figure 4for Figure 2 A magnified view of part A in FIG.

[0064] Figure 5 This is a diagram showing the simulation results of the extended scene echo of the spaceborne synthetic aperture radar beamforming mode using the method of the present invention;

[0065] Figure 6 The present invention is used to expand the scene imaging result diagram of the spotlight mode of the spaceborne synthetic aperture radar using the method of the present invention. DETAILED DESCRIPTION

[0066] The following will be combined with the accompanying drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] In a specific embodiment 1, Figure 1 As shown, the radar of the present invention is a spaceborne synthetic aperture radar, and the radar echo frequency domain simulation and imaging system includes:

[0068] A backscatter coefficient matrix generation module is used to calculate the backscatter coefficient matrix of the target scene in combination with the digital map of the surface;

[0069] 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. According to the geocentric earth-fixed coordinates of the scene center, the coordinates of the satellite orbit closest to the scene center are obtained. Combining the satellite orbit and the coordinates of the satellite orbit closest to the scene center, the coordinates of the satellite orbit azimuth sampling point are calculated.

[0070] The spaceborne synthetic aperture radar echo fast generation module is connected to the backscatter coefficient matrix generation module and the satellite orbit simulation module, and is used to receive the backscatter coefficient matrix calculated by the backscatter coefficient matrix generation module, and obtain the spaceborne synthetic aperture radar baseband echo signal based on the sampling point coordinates in the azimuth direction of the satellite orbit by using the inverse ωK echo generation method;

[0071] The satellite-borne synthetic aperture radar imaging processing module is connected to the satellite orbit simulation module and the satellite-borne synthetic aperture radar echo rapid generation module. Based on the coordinates of the sampling points in the azimuth direction of the satellite orbit, the equivalent velocity and equivalent slant angle are calculated, and the satellite-borne synthetic aperture radar baseband echo signal is transformed into the two-dimensional frequency domain through the two-dimensional fast Fourier transform. The ωK imaging algorithm is used for processing, and the satellite-borne synthetic aperture radar image is obtained through the two-dimensional inverse fast Fourier transform.

[0072] The operation method of the radar echo frequency domain simulation and imaging system is as follows, including the following steps:

[0073] 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;

[0074] S2: S2-1, using the satellite orbit simulation module to calculate the coordinate position of the satellite in the Earth-centered Earth-fixed coordinate system according to the six satellite orbit numbers, and obtain the satellite orbit;

[0075] Calculate the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system (x eci ,y eci ,z eci ),

[0076] The process of calculating the satellite's coordinates (x0, y0, z0) in the geocentric orbital plane coordinate system is:

[0077]

[0078] Based on the satellite's coordinates in the geocentric orbital plane coordinate system (x0, y0, z0), the satellite's coordinates in the geocentric earth-fixed coordinate system (x eci ,y eci ,z eci )The calculation process is:

[0079]

[0080] Among them, (x0, y0, z0) represents the coordinates of the satellite in the geocentric orbital plane coordinate system; a is the semi-major axis of the orbit; e is the orbital eccentricity; f is the true anomaly; (x eci ,y eci ,z eci ) represents the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system; Ω represents the right ascension of the ascending node; i represents the orbital inclination; ω is the argument of perigee.

[0081] S2-2, based on the Earth-fixed coordinates of the scene center and the distance from the scene center to the orbit, obtain the coordinates of the point on the satellite orbit closest to the scene center;

[0082] The distance from the center of the scene to the track is:

[0083]

[0084] Among them, (x sce ,y sce ,z sce ) represents the Earth-fixed coordinate of the center of the scene; (xsat ,y sat ,z sat ) represents the Earth-centered, Earth-fixed coordinates of the satellite orbit.

[0085] S2-3, obtaining the coordinates of the satellite orbit azimuth sampling points according to the azimuth sampling times and the azimuth sampling time interval;

[0086] S3: The spaceborne synthetic aperture radar echo rapid generation module receives the backscatter coefficient matrix and preprocesses the backscatter coefficient matrix. The preprocessing calculation process is:

[0087]

[0088] Where γ(t,η) represents the extended scene scattering coefficient matrix, t is the distance time, η is the azimuth time, R ref represents the reference distance, represents the distance from the center of the scene to the center of the sampling point in the satellite orbit, c represents the speed of light, γ ′ (t,η) represents the extended scene scattering coefficient matrix after preprocessing;

[0089] The pre-processed backscatter coefficient matrix is ​​transformed into the two-dimensional frequency domain by two-dimensional fast Fourier transform and multiplied by the frequency response function of the point target at the reference distance to obtain the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal, where the frequency response function of the point target at the reference distance is:

[0090] H(f t ,f η ,R ref )=FFT2[h(t,η,R ref )],

[0091]

[0092] Among them, h(t,η,R ref ) represents the point target response function at the reference distance; FFT2[·] represents the two-dimensional fast Fourier transform operation; t is the time in the range direction; η represents the time in the azimuth direction; R ref represents the reference distance; R represents the distance from the scene center to the sampling point in the azimuth of the satellite orbit; w(·) is the pulse envelope, which is approximately a rectangular window function, w r represents the range pulse envelope, w a represents the azimuth pulse envelope; c represents the speed of light; η c represents zero Doppler time; K r is the frequency modulation slope in the range direction; f0 represents the center frequency of the transmitting pulse;

[0093] The calculation process of performing two-dimensional inverse fast Fourier transform on the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal to obtain the baseband echo signal s(t,η) of the spaceborne synthetic aperture radar is as follows:

[0094] s(t,η)=IFFT2[S 2df (f t ,f η )],

[0095] Where s(t,η) represents the baseband echo signal of the spaceborne synthetic aperture radar; S 2df (f t ,f η ) is the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal; IFFT2[·] represents the two-dimensional inverse fast Fourier transform.

[0096] S4: The satellite-borne synthetic aperture radar imaging processing module receives the satellite-borne synthetic aperture radar baseband echo signal, and calculates the satellite equivalent speed and equivalent squint angle based on the coordinates of the sampling point in the azimuth direction of the satellite orbit using the ωK imaging algorithm. The equivalent speed and equivalent squint angle of the satellite are calculated as follows:

[0097]

[0098] Among them, v r represents the equivalent speed; θ sq represents the equivalent squint angle; λ represents the radar wavelength; f dc represents the Doppler center frequency; R ref represents the reference distance; f 1r Indicates the Doppler primary modulation frequency.

[0099] The baseband echo signal of the spaceborne synthetic aperture radar is transformed into the two-dimensional frequency domain by two-dimensional fast Fourier transform, and the two-dimensional spectrum of the baseband echo signal of the spaceborne synthetic aperture radar is calculated as:

[0100] S 2df (f t ,f η ) = FFT2[s(t,η)],

[0101] Where s(t,η) represents the baseband echo signal of the spaceborne synthetic aperture radar; FFT2[·] represents the two-dimensional fast Fourier transform.

[0102] By multiplying the reference function, complementary focusing, the reference function is set to:

[0103]

[0104] Among them, R ref represents the reference distance; c represents the speed of light; f0 represents the carrier frequency; v r Indicates equivalent speed; Kr Indicates the distance modulation frequency.

[0105] The distance frequency axis is changed by Stolt interpolation, and the original distance frequency f t Mapped to a new distance frequency f ′ t , which can be expressed as:

[0106]

[0107] Finally, the two-dimensional inverse fast Fourier transform is used to calculate the signal after Stolt interpolation, and the spaceborne synthetic aperture radar image is obtained as follows:

[0108] I SAR =IFFT2[s Stolt (f t ,f η )],

[0109] Among them, I SAR represents the spaceborne synthetic aperture radar image; IFFT2[·] represents the two-dimensional inverse fast Fourier transform; S Stolt (f t ,f η ) represents the signal after Stolt interpolation.

[0110] 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 is implemented when the computer program is executed by a processor.

[0111] 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 in the memory and executable on the processor.

[0112] The present invention combines GPU parallel computing with spaceborne synthetic aperture radar echo simulation and imaging process, which can realize real-time generation of spaceborne synthetic aperture radar echo signals in extended scenarios, thereby improving the efficiency of spaceborne synthetic aperture radar imaging in extended scenarios.

[0113] The method of the present invention is used to perform satellite-borne synthetic aperture radar echo simulation and imaging processing on point targets. The satellite-borne synthetic aperture radar working mode is set to the sliding beam mode. The point target is located at 32° north latitude and 120° east longitude on the earth's surface and is set as a reference point. The coordinates of the closest point of the orbit to the target are calculated to obtain the coordinates of the satellite azimuth point sampling point. The sliding beam rotation point is selected on the extension line of the line connecting the reference point and the center of the satellite orbit. The distance from the sliding beam rotation point to the center of the satellite orbit is 1.01 times the distance from the reference point to the center of the orbit. The point target echo signal is quickly obtained by the inverse ωK echo generation method. The simulation results of the point target echo in the satellite-borne SAR sliding beam mode are as follows: Figure 2 As shown in the figure, the ωK imaging algorithm is used to process the echo signal to obtain the spaceborne synthetic aperture radar image. The point target echo imaging result is shown in Figure 3 , 4 shown.

[0114] Secondly, the method of the present invention is used to simulate and image the extended scene by using the spaceborne synthetic aperture radar echo. The spaceborne synthetic aperture radar working mode is set to the spotlight mode. The center of the scene is selected as the reference point. The spotlight mode spaceborne synthetic aperture radar echo of the selected area is calculated by the inverse ωK echo generation method. Figure 5 As shown in the figure, the extended scene echo signal is processed using the ωK imaging algorithm to obtain a spotlight mode spaceborne synthetic aperture radar image, as shown in Figure 6 shown.

[0115] It can be seen from the experimental results that the present invention can perform full-link simulation on various modes of spaceborne synthetic aperture radar echoes and imaging, is suitable for real-time applications in extended scenarios, and can improve the simulation efficiency of spaceborne synthetic aperture radar.

[0116] Obviously, the above embodiments are merely examples for clear explanation and are not limitations on the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the invention.

Claims

1. A radar echo frequency domain simulation and imaging system, wherein the radar is a spaceborne synthetic aperture radar, characterized in that: include: A backscatter coefficient matrix generation module is used to calculate the backscatter coefficient matrix of the target scene in combination with the digital map of the surface; 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. According to the geocentric earth-fixed coordinates of the scene center, the coordinates of the satellite orbit closest to the scene center are obtained. Combining the satellite orbit and the coordinates of the satellite orbit closest to the scene center, the coordinates of the satellite orbit azimuth sampling point are calculated. A spaceborne synthetic aperture radar echo fast generation module is connected to the backscatter coefficient matrix generation module and the satellite orbit simulation module, and is used to receive the backscatter coefficient matrix calculated by the backscatter coefficient matrix generation module, and obtain a spaceborne synthetic aperture radar baseband echo signal based on the sampling point coordinates in the azimuth direction of the satellite orbit by using an inverse ωK echo generation method; The satellite-borne synthetic aperture radar imaging processing module is connected to the satellite orbit simulation module and the satellite-borne synthetic aperture radar echo rapid generation module, and calculates the equivalent speed and equivalent slant angle based on the coordinates of the satellite orbit azimuth sampling points, transforms the satellite-borne synthetic aperture radar baseband echo signal into the two-dimensional frequency domain through the two-dimensional fast Fourier transform, uses the ωK imaging algorithm for processing, and obtains the satellite-borne synthetic aperture radar image through the two-dimensional inverse fast Fourier transform.

2. The operating method of the radar echo frequency domain simulation and imaging system according to claim 1 is as follows, characterized in that: The following steps are involved: 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 satellite-borne synthetic aperture radar imaging processing module receives the satellite-borne synthetic aperture radar baseband echo signal, and based on the coordinates of the sampling point in the azimuth direction of the satellite orbit, uses the ωK imaging algorithm to calculate the satellite equivalent velocity and equivalent slant angle, and transforms the satellite-borne synthetic aperture radar baseband echo signal into the two-dimensional frequency domain through the two-dimensional fast Fourier transform. Finally, the satellite-borne synthetic aperture radar image is obtained through the two-dimensional inverse fast Fourier transform by multiplying the reference function and performing complementary focusing.

3. The radar echo frequency domain simulation and imaging method according to claim 2, characterized in that: S2 calculates the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system (x eci ,y eci ,z eci ), S2-1, the process of calculating the coordinates (x0, y0, z0) of the satellite in the geocentric orbital plane coordinate system is: S2-2, based on the (x0, y0, z0) calculated in S2-1, the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system (x eci ,y eci ,z eci )The calculation process is: Among them, (x0, y0, z0) represents the coordinates of the satellite in the geocentric orbital plane coordinate system; a is the semi-major axis of the orbit; e is the orbital eccentricity; f is the true anomaly; (x eci ,y eci ,Z eci ) represents the coordinates of the satellite in the Earth-centered Earth-fixed coordinate system; Ω represents the right ascension of the ascending node; i represents the orbital inclination; ω is the argument of perigee.

4. The radar echo frequency domain simulation and imaging method according to claim 2, characterized in that: The distance from the center of the scene to the track in S2 is: Among them, (x sce ,y sce ,z sce ) represents the Earth-fixed coordinate of the center of the scene; (x sat ,y sat ,z sat ) represents the Earth-centered, Earth-fixed coordinates of the satellite orbit.

5. The radar echo frequency domain simulation and imaging method according to claim 2, characterized in that: In S3, the backscattering coefficient matrix γ(t,η) is preprocessed to obtain the calculation process of the preprocessed extended scene scattering coefficient matrix γ′(t,η): Where γ(t,η) represents the extended scene scattering coefficient matrix, t is the distance time, η is the azimuth time, R ref represents the reference distance, represents the distance from the center of the scene to the center of the sampling point in the azimuth of the satellite orbit, c represents the speed of light, and γ′(t,η) represents the preprocessed extended scene scattering coefficient matrix.

6. The radar echo frequency domain simulation and imaging method according to claim 2, characterized in that: The frequency response function of the point target at the reference distance in S3 h(t,η,R ref )for: H(f t ,f η ,R ref )=FFT2[h(t,η,R ref )], Among them, h(t,η,R ref ) represents the target response function at the reference distance; FFT2[·] represents the two-dimensional fast Fourier transform operation; t is the time in the range direction; η represents the time in the azimuth direction; R ref represents the reference distance; R represents the distance from the scene center to the sampling point in the azimuth of the satellite orbit; w(·) is the pulse envelope, which is approximately a rectangular window function, w r represents the range pulse envelope, w d represents the azimuth pulse envelope; c represents the speed of light; η c represents zero Doppler time; K r is the range frequency modulation slope; f0 represents the center frequency of the transmitting pulse.

7. The radar echo frequency domain simulation and imaging method according to claim 2, 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 calculation process of the spaceborne synthetic aperture radar baseband echo signal s(t,η): s(t,η)=IFFT2[S 2df (f t ,f η )], Where s(t,η) represents the baseband echo signal of the spaceborne synthetic aperture radar; S 2df (f t ,f η ) is the two-dimensional spectrum of the spaceborne synthetic aperture radar echo signal; IFFT2[·] represents the two-dimensional inverse fast Fourier transform.

8. The radar echo frequency domain simulation and imaging method according to claim 2, characterized in that: The equivalent speed v of the satellite in S4 r and the equivalent slant angle θ sq The calculation process is: Among them, v r represents the equivalent speed; θ sq represents the equivalent squint angle; γ represents the radar wavelength; f dc represents the Doppler center frequency; R ref represents the reference distance; f 1r Indicates the 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: s 2df (f t ,f η )=FFT2[s(t,η)], Where s(t,η) represents the baseband echo signal of the spaceborne synthetic aperture radar; FFT2[·] represents the two-dimensional fast Fourier transform. The reference function is set as: Among them, R ref represents the reference distance; c represents the speed of light; f0 represents the carrier frequency; v r Indicates equivalent speed; K r Indicates the distance modulation frequency. The distance frequency axis is changed by Stolt interpolation, and the original distance frequency f t Mapped to a new distance frequency f′ t , which can be expressed as: Use the two-dimensional inverse fast Fourier transform to calculate the spaceborne synthetic aperture radar image I after Stolt interpolation. SAR for: I SAR =IFFT2[S Stolt (f t ,f η )], Among them, I SAR represents the spaceborne synthetic aperture radar image; IFFT2[·] represents the two-dimensional inverse fast Fourier transform; S Stolt (f t ,f η ) represents the signal after Stolt interpolation.

9. 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, a radar echo frequency domain simulation and imaging method is implemented.

10. Radar echo frequency domain simulation and imaging equipment, characterized in that: The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor.

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