Echo simulation method of multi-band double-station SAR non-walk-stop mode based on GPU
By using a GPU-based multi-band bistatic SAR non-stop-and-go mode echo simulation method, the problems of stop-and-go approximation error and multiple scattering effects in existing technologies are solved, achieving efficient and accurate echo signal simulation, which is suitable for the design of new SAR systems and the verification of imaging algorithms.
Patent Information
- Application Number
- CN202511879877.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-12
- Publication Date
- 2026-02-27
AI Technical Summary
Existing technologies suffer from stop-and-go approximation errors when simulating bistatic SAR echo signals, and fail to effectively consider the effects of multiple scattering from multi-band targets, resulting in large computational load, low efficiency, and insufficient phase accuracy in simulations.
A GPU-based multi-band bistatic SAR non-stop mode echo simulation method is adopted. The coordinates of the geocentric fixed coordinate system are obtained through the range-Doppler positioning equation. A non-stop pulse propagation model is constructed to compensate for the time delay effect caused by platform motion. The multiple scattering of the target is calculated by ray tracing. OptiX is used to accelerate ray tracing to achieve efficient modeling of multi-band targets.
It accurately simulates the echo signal of bistatic SAR on a continuously moving platform, eliminates the approximate error of walk-stop, and has simulation capabilities in multiple frequency bands, high phase accuracy, and complex scenarios. It is suitable for the design of new SAR systems and the verification of imaging algorithms.
Smart Images
Figure CN121578253A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a GPU-based echo simulation method for a multi-frequency band bistatic SAR non-stop mode, and belongs to the technical field of radar signal processing. BACKGROUND
[0002] A synthetic aperture radar (SAR) can realize all-weather and all-time observation capability, and has important significance in disaster monitoring, resource development and military affairs. With the increasing demand for earth observation, spaceborne SAR systems gradually develop towards high resolution and wide swath, and gradually move from single mode to multi-mode, from single channel to multi-channel, and from single base to multi-star networking collaborative work. Various advanced spaceborne SAR systems are emerging. Under this background, the importance of spaceborne SAR echo simulation in the design of new SAR systems and the verification of new imaging algorithms is increasing.
[0003] For the simulation algorithm of bistatic SAR raw data, it can be divided into time domain algorithm and frequency domain algorithm. Although the time domain algorithm can embed the influence of platform motion error, the simulation calculation amount is huge and the timeliness is low. The frequency domain algorithm has high calculation efficiency on the basis of supporting arbitrary bistatic configuration. An improved bistatic SAR echo simulation method based on sub-aperture is proposed by the University of Electronic Science and Technology of China, which reduces the calculation amount to a certain extent. Li Wenchao et al. proposed a raw data simulation framework for fluctuating terrain under arbitrary configuration bistatic SAR, but the simulation uses a simplified motion model of stop approximation, introduces phase error in the bistatic configuration, and reduces the interference coherence. In addition, the accurate calculation of the radar cross section (RCS) of the bistatic radar is an important part of the bistatic SAR raw data simulation. Beijing University of Chemical Technology and Xi'an University of Electronic Science and Technology use parallel programming tools and combine with GPU acceleration, which reduces the calculation time, but does not consider the influence of multiple scattering of different wave bands on the target. SUMMARY
[0004] The technical problem of the application is to overcome the shortcomings of the prior art and provide a GPU-based echo simulation method for a multi-frequency band bistatic SAR non-stop mode, which can accurately simulate the echo signal of the bistatic SAR under the continuous motion platform and eliminate the stop approximation error. The technical solution of the application is: A GPU-based echo simulation method for a multi-frequency band bistatic SAR non-stop mode comprises the following steps: Step 1: Obtain the coordinates of the target scene in the geocentric fixed coordinate system through the range-Doppler positioning equation; Step 2: Convert the coordinates of the geocentric fixed coordinate system into the coordinates of the WGS-84 coordinate system to realize strict geographical positioning of the target scene. Step 3: Construct a bistatic non-stop pulse propagation model of transceiver separation and compensate the time delay effect caused by continuous platform motion; Step 4: Read in the three-dimensional model of the target to be observed, and dynamically determine the distribution density of the ray tube array in the elevation and azimuth directions according to the target bounding box, incident wave geometry, and wavelength of the working frequency band; Step 5: Based on the determined ray tube array, emit rays from the initial pose of each ray tube, perform occlusion detection and capture effective collision points, update the electromagnetic wave propagation direction and field strength according to the law of specular reflection, and calculate the radar cross section (RCS) of the effective collision points based on the physical optics method; Step 6: Recursively iterate ray tracing and scattering field calculation according to the preset maximum bounce number to realize efficient modeling of multiple scattering of multi-frequency targets in complex scenes; Step 7: Perform simulation and imaging index analysis.
[0005] Further, the step one obtains the coordinates of the target scene in the earth-fixed coordinate system, specifically:
[0006]
[0007]
[0008] wherein, represents the three-dimensional position of the target point, represents the satellite position vector, is the slant range from the target to the radar, represents the satellite velocity vector relative to the target, and vary with time; is the radar imaging Doppler center, is the wavelength, and are the equatorial and polar radii, respectively, and , is a constant, is the target point elevation; , and are defined in the geodetic system, i.e., the earth-fixed coordinate system.
[0009] Further, the formula for converting the coordinates of the earth-fixed coordinate system to the coordinates of the WGS-84 coordinate system is:
[0010]
[0011] wherein, is the coordinate of the target point in the earth-fixed coordinate system, represents the coordinate of the target point in the WGS-84 coordinate system, is the correction term when calculating the latitude, is the radius of curvature of the prime vertical circle of the target point, is the equatorial radius of the reference ellipsoid, is the eccentricity of the earth.
[0012] Further, when calculating the WGS-84 coordinate system coordinate from the earth-fixed coordinate system coordinate, an iterative method is adopted, and the order of iteration is as follows: , the first iteration takes , the iteration is stopped when , is the number of iterations, , is the preset stopping threshold; the iteration value in H is h, and when the difference between and is greater than the set threshold, let , the target point elevation is recalculated, otherwise, the iteration is exited; wherein, is the preset target point elevation, is the assumed horizontal position of the target at this time, is the target elevation of the target point position transformed into the WGS-84 coordinate system of the digital elevation map at the point.
[0013] Further, the step 3 constructs a bistatic non-stop pulse propagation model of the transmitting-receiving separation and compensates for the time delay effect caused by the continuous platform motion, specifically comprising: Step 3.1: According to the transmission time and the receiving time of the radar pulse, the instantaneous positions of the transmission platform and the receiving platform at the corresponding time are obtained respectively; Step 3.2: Based on the instantaneous positions, the accurate propagation time delay of the signal under the bistatic configuration is calculated, that is, the bistatic non-stop echo time delay; Step 3.3: In the echo simulation process of the bistatic spaceborne SAR, the accurately calculated accurate propagation time delay can be used to compensate for the time delay effect caused by the continuous platform motion.
[0014] Further, the formula for obtaining the instantaneous positions of the transmission platform and the receiving platform at the corresponding time according to the transmission time and the receiving time of the radar pulse in step 3.1 is as follows:
[0015]
[0016]
[0017] The non-stopping is calculated, i.e. ; Wherein, is the target position, are the positions of the transmitting satellite and the receiving satellite at the transmitting moment respectively, is the position of the receiving satellite at the receiving moment, is the distance from the transmitting satellite to the target at the transmitting moment, is the distance from the receiving satellite to the target at the transmitting moment, is the distance from the receiving satellite to the target at the receiving moment.
[0018] 7. The echo simulation method of the GPU-based multi-band bistatic SAR non-stopping mode according to claim 6, wherein the formula for calculating the accurate propagation time delay of the signal based on the instantaneous position in step 3.2 under the bistatic configuration is:
[0019]
[0020]
[0021] The above formulas are solved simultaneously to obtain the echo time delay of the bistatic non-stopping, and the formula is:
[0022] Wherein, is the accurate propagation time delay calculated, i.e. the echo time delay of the bistatic non-stopping, is the velocity vector of the receiving satellite at the transmitting moment, is the angle between and , and is the speed of light.
[0023] Further, based on the determined ray tube array, the rays are emitted from the initial poses of the ray tubes, the occlusion detection is performed and the effective collision points are captured, the electromagnetic wave propagation direction and field strength are updated according to the law of specular reflection, and the radar cross section RCS of the point is calculated based on the physical optics method, specifically: During the ray generation stage, multiple scattering recursive modeling is achieved through loop control. The initial ray is determined based on the thread's two-dimensional index and the ray tube mesh parameters, and the OptiX's rtTrace function is called to perform ray tracing. After a ray collision, the ray origin is updated to the collision point position, the reflection direction is determined by the specular reflection vector, and the reflected electric field is used as the new incident field. The scattered field is recalculated in combination with the current frequency band material properties. When calculating the radar cross section (RCS), the vertex coordinates are indexed by the collision surface element ID and the normal vector is calculated for the reflection direction calculation. A verification ray is emitted towards the receiver. If it is not blocked, it is determined to be a valid scattering path. The physical optics method is used to calculate the RCS values of different frequency bands for the valid path, and the dispersion scattering parameters are packaged and written into the CPU memory. The dispersion scattering parameters include the RCS value, collision point coordinates, and path length.
[0024] Furthermore, step 6 recursively iterates through ray tracing and scattering field calculations according to a preset maximum number of bounces to achieve efficient modeling of multiple scattering of multi-frequency targets in complex scenes. The ray tracing thread is terminated when the number of collisions exceeds a preset maximum value.
[0025] Furthermore, step 7 involves analyzing simulation data and imaging indicators, including: Step 7.1: Simulation setup and data generation; A complex terrain area was selected as the simulation scenario, and nine point targets were evenly distributed. X-band SAR data, X-band interferometric SAR data, and Ku-band interferometric SAR data were generated, and the point target echo information was integrated simultaneously. Step 7.2: Image processing and index analysis; Imaging processing was performed on X-band SAR simulation data, and the locations of point targets were identified. Then, all point targets in the scene were evaluated, including range resolution, azimuth resolution, and absolute phase accuracy. Under a 500-meter baseline condition, interferometric phase maps of X-band and Ku-band interferometric SAR data were obtained and their performance was analyzed.
[0026] The advantages of this invention compared to the prior art are: The echo simulation method of this invention can accurately simulate the echo signal of bistatic SAR on a continuously moving platform, eliminate the approximate error of walk-stop, and has simulation capabilities in multiple frequency bands, high phase accuracy and complex scenarios. It is suitable for the design of new SAR systems and the verification of imaging algorithms. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the geocentric fixed coordinate system of the "distance-Doppler" model provided by the present invention; Figure 2 This is a schematic diagram of dual-station non-stop-go delay calculation provided by the present invention; Figure 3 This is a flowchart of the GPU processing of the OptiX module provided by the present invention; Figure 4 This is a schematic diagram of the optical image of the simulated scene provided by the present invention; Figure 5 This invention provides a digital elevation map (DEM) of a simulated scene after positioning. Figure 6 This is a schematic diagram of the imaging results of X-band SAR simulation data provided by the present invention; Figure 7 This is a schematic diagram of the interferometric phase of X-band InSAR data provided by the present invention; Figure 8 This is a schematic diagram of the interferometric phase of Ku-band InSAR data provided by the present invention; Figure 9 This is a flowchart of the method of the present invention. Detailed Implementation
[0028] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.
[0029] This invention provides a GPU-based method for simulating echoes in multi-band bistatic SAR non-stop-go mode. Example 1. Currently, simulation algorithms for bistatic SAR raw data can be divided into time-domain algorithms and frequency-domain algorithms. While time-domain algorithms can incorporate the influence of platform motion errors, they suffer from massive computational complexity and low timeliness. Frequency-domain algorithms, on the other hand, offer higher computational efficiency while supporting arbitrary bistatic configurations. Improved sub-aperture-based bistatic SAR echo simulation methods reduce computational load to some extent. In existing raw data simulation frameworks, a simplified motion model using a stop-and-go approximation is employed, and phase errors are introduced into the bistatic configuration to reduce interferometric coherence. Furthermore, accurate calculation of the bistatic radar cross-section (RCS) is a crucial component of bistatic SAR raw data simulation. Existing methods utilize parallel programming tools combined with GPU acceleration, which reduces computation time but fails to consider the effects of multiple scattering of the target by different wavebands.
[0030] To address the aforementioned problems, this embodiment provides a GPU-based multi-band bistatic SAR non-stop-go mode echo simulation method. Accurate localization of the simulation scene is achieved through the range-Doppler (RD) positioning equation. A non-stop-go pulse propagation model under bistatic configuration is established and the time delay effect caused by continuous platform motion is compensated. Combined with the bistatic configuration, target multiple scattering is calculated using GPU-Optix accelerated ray tracing. For example... Figure 9 As shown, the method includes: Step 1: Obtain the geocentric coordinates of the target scene using the distance-Doppler positioning equation.
[0031] Specifically, please see Figure 1 , Figure 1 This is a schematic diagram of the geocentric fixed coordinate system of the "distance-Doppler" model provided in this embodiment of the invention. The formula for obtaining the geocentric fixed coordinate system coordinates of the target scene is:
[0032]
[0033]
[0034] in, Indicates the three-dimensional position of the target point. Represents the satellite position vector. This represents the velocity vector of the satellite relative to the target. and It changes over time. For radar imaging Doppler center, For wavelength, The slant range from the target to the radar. and These are the equatorial and polar radii, respectively, and , It is a constant. The elevation of the target point. , and All are defined in the geocentric fixed coordinate system (referred to as the geocentric system).
[0035] Step 2: Convert the geocentric fixed coordinate system coordinates to WGS-84 coordinate system coordinates to achieve strict geolocation of the target scene.
[0036] Specifically, the formula for converting coordinates from the geocentric fixed coordinate system to the WGS-84 coordinate system is as follows:
[0037]
[0038] in, Let G be the coordinates of any target point in the Earth-fixed system. This indicates the coordinates of the point in the WGS-84 coordinate system. This is a correction term for latitude inverse calculation. Let be the radius of curvature of the zonal loop at that point. For reference, the equatorial radius of the ellipsoid, This is the Earth's eccentricity.
[0039] In one embodiment of the present invention, when determining the coordinates in the WGS-84 coordinate system from the known coordinates in the geocentric fixed coordinate system, an iterative method is used, and the order of iteration is as follows: In the first iteration, take Iterate to Stop at time The iteration count. When and When the difference is greater than the set threshold, let If the target point elevation is not found, recalculate it; otherwise, exit the iteration.
[0040] in, To preset the elevation of the target point, Assuming the target's horizontal position at this moment, To transform the location of the target point to the target elevation in the WGS-84 coordinate system where the digital elevation map (DEM) is located.
[0041] Step 3: Construct a dual-station non-stop pulse propagation model with separate transmit and receive terminals and compensate for the time delay effect caused by continuous platform motion.
[0042] Furthermore, step 3 specifically includes: Step 3.1: Based on the transmission and reception times of the radar pulses, obtain the instantaneous positions of the transmitting and receiving platforms at the corresponding times; Specifically, please see Figure 2 , Figure 2 This is a schematic diagram of dual-station non-stop-go delay calculation provided in an embodiment of the present invention. The formulas for obtaining the instantaneous positions of the transmitting and receiving platforms at corresponding moments based on the radar pulse transmission and reception times are as follows:
[0043]
[0044]
[0045] Calculation is not a "walk-stop" operation, that is, calculation .
[0046] in, For the target location, These represent the positions of the satellite launching and receiving at the launch time, respectively. These represent the positions of the satellite transmitting and receiving at the time of reception. The distance from the satellite to the target at the time of launch. To receive the distance between the satellite and the target at the time of launch, To receive the distance from the satellite to the target at the receiving time.
[0047] Step 3.2: Based on the instantaneous position, calculate the precise propagation delay of the signal in the bistation configuration. .
[0048] Specifically, combining the trigonometric cosine theorem, the formula for calculating the precise propagation delay of the signal in a bistatic configuration based on the instantaneous position is as follows:
[0049]
[0050]
[0051] Solving the above equations simultaneously, we can obtain the echo delay for bistation non-stop operation, as shown in the formula:
[0052] in, To calculate the echo delay of the bistation non-stop operation, The velocity vector of the satellite received at the time of launch. for and The included angle, It is the speed of light.
[0053] Step 3.3: Compensate for the time delay effect caused by continuous platform motion.
[0054] Specifically, in the echo simulation process of bistatic satellite-borne SAR, precise calculations are used. This can compensate for the time delay caused by continuous platform motion.
[0055] Step 4: Read in the three-dimensional model of the target to be observed, and dynamically determine the distribution density of the X-ray tube array in the elevation and azimuth directions based on the target bounding box, the geometric relationship of the incident wave and the wavelength of the working frequency band.
[0056] Specifically, please see Figure 3 , Figure 3 This is a flowchart of the GPU processing of the OptiX module provided in an embodiment of the present invention.
[0057] Step 5: Based on the determined ray tube array, emit rays from the initial pose of each ray tube, perform occlusion detection and capture effective collision points, update the electromagnetic wave propagation direction and field strength according to the specular reflection law, and calculate the radar cross section (RCS) of the point based on the physical optics method.
[0058] Specifically, in the ray generation stage, multiple scattering recursive modeling is achieved through loop control. The initial ray is determined based on the thread's two-dimensional index and the ray tube mesh parameters, and ray tracing is performed using OptiX's rtTrace function. After a ray collision, the ray origin is updated to the collision point position, the reflection direction is determined by the specular reflection vector, and the reflected electric field is used as the new incident field. The scattered field is recalculated in conjunction with the current frequency band material properties. When calculating the radar cross section (RCS), the vertex coordinates are indexed by the collision surface element ID, and the normal vector is calculated for the reflection direction solution. A verification ray is emitted towards the receiver; if it is not blocked, it is considered a valid scattering path. The physical optics method is used to calculate the RCS values for different frequency bands on the valid path, and the dispersion scattering parameters (RCS, collision point coordinates, path length) are packaged and written into CPU memory.
[0059] Step 6: Recursively iterate and perform ray tracing and scattering field calculations according to the preset maximum number of bounces to achieve efficient modeling of multiple scattering of multi-band targets in complex scenes.
[0060] Specifically, the ray tracing thread is terminated when the number of collisions exceeds a preset maximum value.
[0061] The correctness and effectiveness of the GPU-based multi-band bistatic SAR non-stop-go mode echo simulation method provided in the embodiments of the present invention will be demonstrated below.
[0062] The proof process includes the following steps: Step 7: Analysis of simulation data and imaging indicators.
[0063] Furthermore, step 7.1 specifically includes: Step 7.1: Simulation Setup and Data Generation: Please see Figure 4 and Figure 5 , Figure 4 These are simulated scene optical images provided in embodiments of the present invention. Figure 5 This is a digital elevation image (DEM) of a simulated scene after positioning, provided in this embodiment of the invention. A complex terrain area is selected as the simulation scene, and nine point targets are evenly distributed. The simulation parameters are set according to Table 1, and the scene optical image and the positioned DEM are shown in Table 1. Figure 4 , Figure 5 As shown, the method presented in this paper generates X-band SAR data, X-band interferometric SAR data, and Ku-band interferometric SAR data, and simultaneously integrates point target echo information.
[0064] Table 1 Simulation Parameters
[0065] Further, step 7.2: Image processing and index analysis: Please seeFigure 6 , Figure 7 and Figure 8 , Figure 6 This is the imaging result of X-band SAR simulation data provided in the embodiments of the present invention. Figure 7 This refers to the interferometric phase of the X-band InSAR data provided in this embodiment of the invention. Figure 8 This refers to the interferometric phase of the Ku-band InSAR data provided in this embodiment of the invention. Imaging processing is performed on the X-band SAR simulation data, and the results are as follows... Figure 6 As shown in the figure, the red box marks the location of the point target. Further evaluation of all point targets in the scene was performed, including range resolution, azimuth resolution, and absolute phase accuracy; specific data are shown in Table 2. The results show that the absolute phase accuracy of the X-band is better than 2°, verifying the high accuracy of the bistatic non-stop simulation model presented in this paper. Under a 500-meter baseline condition, the interferometric phase diagram of the X-band and Ku-band interferometric SAR data was obtained, as shown in Table 2. Figure 7 , Figure 8 As shown in the figure, the X-band interference fringes are sparser and the Ku-band is denser under the same baseline and scene, which is consistent with the theoretical expectation of electromagnetic wave frequency band differences. This indicates that the present method can effectively realize multi-band, high-reliability interferometric SAR simulation in complex scenes.
[0066] Table 2 Evaluation Data
[0067] The echo simulation method of this invention can accurately simulate the echo signal of bistatic SAR on a continuously moving platform, eliminate the approximate error of walk-stop, and has simulation capabilities in multiple frequency bands, high phase accuracy and complex scenarios. It is suitable for the design of new SAR systems and the verification of imaging algorithms.
[0068] The parts of this invention not described in detail are common knowledge to those skilled in the art.
Claims
1. A GPU-based multi-band bistatic SAR non-stop-go mode echo simulation method, characterized in that... include: Step 1: Obtain the geocentric fixed coordinates of the target scene using the range-Doppler positioning equation; Step 2: Convert the geocentric fixed coordinate system coordinates to the WGS-84 coordinate system coordinates to achieve strict geolocation of the target scene; Step 3: Construct a dual-station non-stop pulse propagation model with separate transmit and receive terminals and compensate for the time delay effect caused by continuous platform motion; Step 4: Read in the three-dimensional model of the target to be observed, and dynamically determine the distribution density of the X-ray tube array in the elevation and azimuth directions based on the target bounding box, the geometric relationship of the incident wave and the wavelength of the working frequency band. Step 5: Based on the determined ray tube array, emit rays from the initial pose of each ray tube, perform occlusion detection and capture effective collision points, update the electromagnetic wave propagation direction and field strength according to the specular reflection law, and calculate the radar cross section (RCS) of the effective collision point based on the physical optics method. Step 6: Recursively iterate and perform ray tracing and scattering field calculations according to the preset maximum number of bounces to achieve efficient modeling of multiple scattering of multi-band targets in complex scenes; Step 7: Perform simulation and imaging index analysis.
2. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 1, characterized in that: Step one, obtaining the geocentric fixed coordinates of the target scene, specifically involves: in, Indicates the three-dimensional position of the target point. Represents the satellite position vector. The slant range from the target to the radar. This represents the velocity vector of the satellite relative to the target. and It changes over time; For radar imaging Doppler center, For wavelength, and These are the equatorial and polar radii, respectively, and , It is a constant. The elevation of the target point; , and All are defined in the Earth-fixed system, which refers to the geocentric fixed coordinate system.
3. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 1, characterized in that: The formula for converting the geocentric fixed coordinate system coordinates to the WGS-84 coordinate system in step two is as follows: in, Let G be the coordinates of any target point in the Earth-fixed system. This indicates the coordinates of the target point in the WGS-84 coordinate system. This is a correction term used when calculating latitude inversely. Let be the radius of curvature of the zonal loop at that point. For reference, the equatorial radius of the ellipsoid, This is the Earth's eccentricity.
4. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 3, characterized in that: When calculating WGS-84 coordinates from a known geocentrically fixed coordinate system, an iterative method is used, and the order of iterations is as follows: In the first iteration, take Iterate to Stop at time For the number of iterations, , The preset stopping threshold is used; the iteration value in H is h, when... and When the difference is greater than the set threshold, let Recalculate the elevation of the target point; otherwise, exit the iteration. in, To preset the elevation of the target point, Assuming the target's horizontal position at this moment, To transform the location of the target point to the target elevation in the WGS-84 coordinate system where the digital elevation map is located.
5. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 1, characterized in that, Step 3 involves constructing a dual-station, non-stop pulse propagation model with separate transmit and receive terminals and compensating for the time delay caused by continuous platform motion. Specifically, this includes: Step 3.1: Based on the transmission and reception times of the radar pulses, obtain the instantaneous positions of the transmitting and receiving platforms at the corresponding times; Step 3.2: Based on the instantaneous position, calculate the precise propagation delay of the signal in the bistation configuration, i.e., the echo delay of the bistation non-stop mode; Step 3.3: In the echo simulation of bistatic satellite SAR, the time delay caused by continuous platform motion can be compensated by using the accurately calculated propagation time delay.
6. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 5, characterized in that: In step 3.1, the formulas for obtaining the instantaneous positions of the transmitting and receiving platforms at corresponding moments based on the radar pulse transmission and reception times are as follows: Calculate non-stop operation, i.e., calculate ; in, For the target location, These represent the positions of the satellite launching and receiving at the launch time, respectively. To receive the satellite's position at the designated time, The distance from the satellite to the target at the time of launch. To receive the distance between the satellite and the target at the time of launch, To receive the distance from the satellite to the target at the receiving time.
7. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 6, characterized in that: The formula for calculating the precise propagation delay of the signal in the bistatic configuration based on the instantaneous position in step 3.2 is as follows: Solving the above equations simultaneously, we can obtain the echo delay for bistation non-stop operation, as shown in the formula: in, To calculate the precise propagation delay, i.e. the echo delay of a two-station non-stop system, The velocity vector of the satellite received at the time of launch. for and The included angle, It is the speed of light.
8. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 1, characterized in that: Step 5, based on the determined ray tube array, emits rays from the initial pose of each ray tube, performs occlusion detection and captures valid collision points, updates the electromagnetic wave propagation direction and field strength according to the specular reflection law, and calculates the radar cross section (RCS) of that point based on physical optics methods. Specifically: During the ray generation stage, multiple scattering recursive modeling is achieved through loop control. The initial ray is determined based on the thread's two-dimensional index and the ray tube mesh parameters, and the OptiX's rtTrace function is called to perform ray tracing. After a ray collision, the ray origin is updated to the collision point position, the reflection direction is determined by the specular reflection vector, and the reflected electric field is used as the new incident field. The scattered field is recalculated in combination with the current frequency band material properties. When calculating the radar cross section (RCS), the vertex coordinates are indexed by the collision surface element ID and the normal vector is calculated for the reflection direction calculation. A verification ray is emitted towards the receiver. If it is not blocked, it is determined to be a valid scattering path. The physical optics method is used to calculate the RCS values of different frequency bands for the valid path, and the dispersion scattering parameters are packaged and written into the CPU memory. The dispersion scattering parameters include the RCS value, collision point coordinates, and path length.
9. The echo simulation method for multi-band bistatic SAR non-stop-go mode based on GPU according to claim 1, characterized in that: Step 6 recursively iterates through ray tracing and scattering field calculations according to a preset maximum number of bounces, enabling efficient modeling of multiple scattering of multi-frequency targets in complex scenes. The ray tracing thread is terminated when the number of collisions exceeds a preset maximum value.
10. The echo simulation method for multi-band bistatic SAR non-stop-and-go mode based on GPU according to any one of claims 1 to 9, characterized in that, Step 7 involves analyzing simulation data and imaging metrics, including: Step 7.1: Simulation setup and data generation; A complex terrain area was selected as the simulation scenario, and nine point targets were evenly distributed. X-band SAR data, X-band interferometric SAR data, and Ku-band interferometric SAR data were generated, and the point target echo information was integrated simultaneously. Step 7.2: Image processing and index analysis; Imaging processing was performed on X-band SAR simulation data, and the locations of point targets were identified. Then, all point targets in the scene were evaluated, including range resolution, azimuth resolution, and absolute phase accuracy. Under a 500-meter baseline condition, interferometric phase maps of X-band and Ku-band interferometric SAR data were obtained and their performance was analyzed.