Bistatic synthetic aperture radar rapid imaging method, electronic equipment and storage medium
By performing deskewing and interpolation transformations in bistatic SAR, combined with nonlinear scaling processing, the problems of spectral broadening and azimuth aliasing in spotlight mode were solved, improving imaging quality and accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QIANYUAN NATIONAL LABORATORY
- Filing Date
- 2026-03-06
- Publication Date
- 2026-05-12
AI Technical Summary
Existing bistatic SAR imaging algorithms have failed to effectively address the issues of spectral broadening and azimuth aliasing caused by beam rotation in spotting mode, thus affecting imaging performance.
By using signal processing based on the transmitter's spotlight mode, the deskewing parameters are determined and deskewing is performed. Combined with interpolation transformation and nonlinear scaling, the final SAR image is obtained using azimuth-directed Fourier transform, thus solving the spectral broadening and imaging blurring caused by Doppler centroid spatial variation.
It improves imaging quality and effect, solves the problem of spectral broadening caused by the spatial variation of the Doppler centroid of the target point in the down-oriented mode, and achieves higher imaging accuracy and efficiency.
Smart Images
Figure CN122017839A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of radar technology, and more specifically, to a dual-base synthetic aperture radar rapid imaging method, electronic device, and storage medium. Background Technology
[0002] Synthetic Aperture Radar (SAR) enables all-weather, day-and-night imaging observations, playing a crucial role in topographic mapping, resource exploration, ocean current and hydrological observation, disaster monitoring, and vegetation analysis. Compared to monostatic SAR, bistatic SAR, due to its separate transmit and receive configuration, offers advantages such as strong concealment, high anti-interference capabilities, and high survivability. It allows for lightweight, miniaturized, low-cost, and diversified receiving stations, and provides omnidirectional imaging capabilities including forward-looking, side-looking, and backward-looking views. Among these, complex trajectory bistatic SAR with a spotlight mode refers to the use of more complex motion trajectories by the transmit and receive stations during data acquisition, such as satellite platforms or mobile platforms. By rotating the beams of the transmit and receive platforms, spotlight mode imaging is achieved, enabling the acquisition of long-term echo data, a wider observation angle, and thus higher azimuth resolution.
[0003] However, existing research on bistatic SAR nonlinear variable-scale imaging algorithms only focuses on algorithm optimization for bistatic SAR shift-variable configurations, without considering the impact of beam rotation in spotting mode on spectral broadening and spatial variability. Therefore, the constructed perturbation function cannot effectively solve the azimuth spatial variation problem and will cause azimuth aliasing, thus seriously affecting the imaging effect. Summary of the Invention
[0004] The purpose of this application is to address the shortcomings of the prior art by providing a dual-base synthetic aperture radar rapid imaging method, electronic device, and storage medium to solve the problem of poor imaging performance in the prior art.
[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows: In a first aspect, one embodiment of this application provides a fast imaging method for dual-base synthetic aperture radar, applied to a receiving station, the method comprising: Based on the transmitted signal emitted in the beam-focusing mode of the transmitting station, the echo signal is received and acquired; Based on the echo signal, the deskewing parameters are determined, and the echo signal is deskewed according to the deskewing parameters to obtain the deskewed echo signal; The de-skewed echo signal is subjected to interpolation transformation to obtain the interpolated echo signal; The interpolated echo signal is nonlinearly scaled in the azimuth direction, and the nonlinear scaling parameters are calculated. The final SAR image is obtained by azimuth Fourier transform.
[0006] Optionally, the echo signal is represented as: ; in, Indicates the target point The scattering coefficient, Indicates the coordinates of the target point. and These represent the range and azimuth antenna radiation patterns, respectively. Indicates distance in terms of time. Indicates the range frequency. Indicates the range-direction frequency modulation slope. Represents the speed of light. Indicates the pulse width. Indicates direction in slow time; j is the imaginary sign in the complex number. Indicates the time for synthesizing the aperture. Indicates the time of illumination at the center of the target point; After receiving and acquiring the echo signal from the transmitted signal emitted in the beam-focusing mode of the transmitting station, the method further includes: The echo signal is subjected to range pulse compression based on the compensation phase to obtain the compensated echo signal, wherein the compensation phase is... The compensated echo signal is represented as follows: .
[0007] Optionally, the Represented as: ; in, The ground projection representing the oblique angle of the receiving station. Indicates the beamwidth of the receiving station. This indicates the ground movement speed of the receiving station beam. , This indicates the velocity of the receiving station along the y-axis. This represents the beam control factor of the receiving station and is expressed as a function of the antenna's azimuth and rotation speed. Decide; Represented as: ;in, Indicates the location and time Reference distance of the receiving station A marker indicating the beam imaging mode of the receiving station; where, .
[0008] Optionally, determining deskewing parameters based on the echo signal and deskewing the echo signal based on the deskewing parameters to obtain a deskewing echo signal includes: The deskewing parameter is determined based on the echo spectrum of the echo signal. , This represents the first-order coefficient of the Doppler coefficients with respect to the azimuth center time, where, ,in, Indicates the first-order slope of the distance; Based on the de-skew parameters, the de-skew phase is obtained. ; The echo signal is multiplied sequentially by the filtered phase and the de-skewed phase to obtain the de-skewed echo signal, wherein the filtered phase is represented as follows: .
[0009] Optionally, the step of performing interpolation transformation on the de-skewed echo signal to obtain the interpolated echo signal includes: The de-skewed echo signal is interpolated to obtain the interpolated echo signal, which is represented as follows: The interpolation method used is: .
[0010] Optionally, the step of performing azimuth nonlinear scaling on the interpolated echo signal, calculating and obtaining the nonlinear scaling parameters, and obtaining the final SAR image through azimuth Fourier transform includes: Determine the azimuth rate adjustment factor and the positioning factor; Based on the azimuth scaling factor and the positioning factor, the processed echo signal is subjected to higher-order phase compensation and a first perturbation to obtain the echo signal after the first perturbation. Based on the azimuth scaling factor and the positioning factor, the echo signal after the first disturbance is subjected to azimuth phase compensation and a second disturbance to obtain the echo signal after the second disturbance. The azimuth-direction inverse Fourier transform is performed on the echo signal after the secondary perturbation to obtain the final SAR image.
[0011] Optionally, determining the azimuth scaling factor and the positioning factor includes: Based on the preset expression, determine the range of values for the azimuth scaling factor and the range of values for the positioning factor that satisfy the preset conditions.
[0012] Optionally, the step of performing higher-order phase compensation and a first perturbation on the processed echo signal based on the azimuth scaling factor and the positioning factor to obtain a perturbed echo signal includes: Based on the azimuth scaling factor and the positioning factor, obtain the phase expression corresponding to the first disturbance; The processed echo signal is subjected to high-order phase compensation, and a perturbation is performed according to the phase expression corresponding to the first perturbation. The step of performing azimuth phase compensation and secondary perturbation on the echo signal after the first perturbation based on the azimuth scaling factor and the positioning factor to obtain the echo signal after the second perturbation includes: Based on the azimuth scaling factor and the positioning factor, obtain the phase expression corresponding to the secondary disturbance; The echo signal after the first disturbance is subjected to azimuth phase compensation, and a second disturbance is performed according to the phase expression corresponding to the second disturbance.
[0013] Secondly, another embodiment of this application provides an electronic device, including: a processor and a memory, the memory storing machine-readable instructions executable by the processor, the processor being configured to execute the machine-readable instructions to perform the dual-base synthetic aperture radar rapid imaging method as described in any of the first aspects above.
[0014] Fourthly, another embodiment of this application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the dual-base synthetic aperture radar rapid imaging method as described in any of the first aspects above.
[0015] The beneficial effects of this application are: In this embodiment, based on bistatic SAR, the echo signal is received based on the transmitted signal emitted in the spotlight mode of the transmitting station. Based on the echo signal, a deskewing parameter is determined, and the echo signal is deskewed according to the deskewing parameter to obtain a deskewed echo signal. The deskewed echo signal is then interpolated to obtain an interpolated echo signal. The interpolated echo signal is then subjected to azimuth nonlinear scaling, and the nonlinear scaling parameter is calculated. Finally, the azimuth-to-Fourier transform is performed to obtain the final SAR image. By using deskewing and interpolation, the problem of spectral broadening caused by the Doppler centroid variation along the azimuth towards the target point in spotlight mode can be solved, avoiding image blurring. Furthermore, this significantly improves the imaging quality and effect. Attached Figure Description
[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 A structural diagram of a dual-base SAR fast imaging system provided in this application embodiment; Figure 2 A flowchart illustrating a fast imaging method for dual-base synthetic aperture radar provided in an embodiment of this application; Figure 3 A flowchart illustrating a fast imaging method for dual-base synthetic aperture radar provided in another embodiment of this application; Figure 4 This is a schematic diagram illustrating an application scenario of a dual-base synthetic aperture radar fast imaging method provided in an embodiment of this application; Figure 5 This is a schematic diagram of the simulated imaging results in a dual-base synthetic aperture radar fast imaging method provided in an embodiment of this application. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.
[0019] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
[0020] It should be noted that the term "comprising" will be used in the embodiments of this application to indicate the presence of the features declared thereafter, but does not exclude the addition of other features.
[0021] First, let me explain the professional data required for this application: 1. Bistatic Synthetic Aperture Radar (SAR) refers to a SAR system in which the transmitting station and receiving station are located on different platforms, with at least one platform being a moving platform. Conceptually, it belongs to the category of bistatic radar.
[0022] This application is further applied to complex trajectory bistatic SAR (BiSAR), which refers to the two stations taking non-linear motion and having higher-order motion parameters.
[0023] 2. Spotlight mode refers to the use of physical beam rotation by the two base stations of SAR to adjust the beam direction and achieve long-term observation of a certain area, thereby obtaining higher resolution observation results for that area.
[0024] 3. Keystone transform refers to the decoupling of echo data through interpolation.
[0025] 4. Nonlinear scaling refers to introducing a higher-order perturbation factor into the SAR echo signal to perturb the azimuth phase factor, making the coefficient with spatial variation zero, thereby achieving spatial variation removal.
[0026] Figure 1 A structural diagram of a dual-static SAR fast imaging system provided in this application embodiment is shown below. Figure 1 As shown, the system includes a transmitter station 01 and a receiver station 02. In a dual-base SAR scenario, the transmitter station 01 and the receiver station 02 operate in preset modes. The transmitter station 01 transmits signals, and the receiver station 02 can receive signals without transmitting them, thus obtaining the echo signal.
[0027] In this embodiment, the main focus is on scenarios with complex trajectories, where neither the transmitting station 01 nor the receiving station 02 necessarily travels in a straight line.
[0028] Furthermore, both launch station 01 and receiving station 02 employ focused beam imaging. For example, assuming launch station 01 is a low-Earth orbit satellite and receiving station 02 is a missile, the low-Earth orbit satellite provides illumination to the missile. The missile observes forward, and with the low-Earth orbit satellite and missile beams aligned, both illuminating a specific area, the missile can approach the illuminated target area quickly without emitting electromagnetic waves, achieving precision strike by silently receiving the signal. The focused beam mode can be either a staring focused beam mode or a sliding focused beam mode; no specific limitation is made here.
[0029] The coordinate system of the above system can be represented as (x, y, z) as shown in the figure. The location of the target point in the space where the system is located can be recorded using this coordinate system.
[0030] However, in current bistatic SAR imaging methods, the Doppler centroid varies along the azimuth towards the target point in spotting mode, causing spectral broadening. The pulse repetition frequency (PRF) is lower than the broadened spectrum, leading to image blurring. This application provides a novel imaging method to ensure the quality of rapid imaging.
[0031] Figure 2 This is a flowchart illustrating a fast imaging method for dual-base synthetic aperture radar according to an embodiment of this application. The method is executed by the aforementioned receiving station. Figure 2 As shown, the method includes: S201. Based on the transmitted signal emitted in the beam-focusing mode of the transmitting station, receive and acquire the echo signal.
[0032] As explained above, in a bistatic SAR scenario, the receiving station in this embodiment can receive and acquire echo signals.
[0033] S202. Based on the above echo signal, determine the deskewing parameters, and deskew the echo signal according to the deskewing parameters to obtain the deskewed echo signal.
[0034] The aforementioned echo signal can be expanded into an echo spectrum using an expression. Based on this expression, the deskewing parameter can be obtained. Deskewing can resolve the imaging blurring problem caused by the Doppler centroid variation along the azimuth towards the target point in spotting mode, which results in spectral broadening.
[0035] S203. Perform interpolation transformation on the above de-skewing echo signal to obtain the interpolated echo signal.
[0036] During the deskewing process, additional Doppler phase is introduced. This problem can be solved by performing an interpolation process and using the Keystone transform.
[0037] S204. Perform azimuth nonlinear scaling on the echo signal after the above interpolation transformation, calculate and obtain the nonlinear scaling parameters, and obtain the final SAR image by azimuth to Fourier transform.
[0038] For scenarios with complex trajectories, this application embodiment also uses a nonlinear orientation scaling method to balance the orientation towards spatial variation, thereby facilitating consistent focusing of the orientation towards the target point.
[0039] In this embodiment, based on bistatic SAR, the echo signal is received based on the transmitted signal emitted in the spotlight mode of the transmitting station. Based on the echo signal, a deskewing parameter is determined, and the echo signal is deskewed according to the deskewing parameter to obtain a deskewed echo signal. The deskewed echo signal is then interpolated to obtain an interpolated echo signal. The interpolated echo signal is then subjected to azimuth nonlinear scaling, and the nonlinear scaling parameter is calculated. Finally, the azimuth-to-Fourier transform is performed to obtain the final SAR image. By using deskewing and interpolation, the problem of spectral broadening caused by the Doppler centroid variation along the azimuth towards the target point in spotlight mode can be solved, avoiding image blurring. Furthermore, this significantly improves the imaging quality and effect.
[0040] Furthermore, the received echo signal is represented as: ; in, Indicates the target point The scattering coefficient, Indicates the coordinates of the target point. and These represent the range and azimuth antenna radiation patterns, respectively. Indicates distance in terms of time. Indicates the range frequency. Indicates the range-direction frequency modulation slope. Represents the speed of light. Indicates the pulse width. Indicates direction in slow time; j is the imaginary sign in the complex number. Indicates the time for synthesizing the aperture. This indicates the time of illumination at the center of the target point.
[0041] Furthermore, after receiving and acquiring the echo signal from the transmitted signal emitted in the beam-focusing mode of the transmitting station, the process also includes: The echo signal is subjected to range pulse compression based on the compensation phase to obtain the compensated echo signal.
[0042] Wherein, the compensation phase is The compensated phase is multiplied by the above echo signal to obtain the compensated echo signal, which is expressed as follows: .
[0043] Furthermore, the above echo signal is expanded as follows: Represented as: ; in, The ground projection representing the oblique angle of the receiving station. Indicates the beamwidth of the receiving station. This indicates the ground movement speed of the receiving station beam. , This indicates the velocity of the receiving station along the y-axis. This represents the beam control factor of the receiving station and is expressed as a function of the antenna's azimuth and rotation speed. Decide; Represented as: ;in, Indicates the location and time Reference distance of the receiving station A marker indicating the beam imaging mode of the receiving station; where, .
[0044] Furthermore, in this embodiment, the distance history of complex trajectory bistatic SAR (BiSAR) is... It can be represented as: ; in, , Let represent the position vectors of the transmitting station and the receiving station, respectively, and can be expressed as ; in, , , , , and Let represent the three-dimensional spatial coordinates of the transmitting and receiving stations, as shown below: ; ; in, , and This indicates the position of the illumination source at reference time zero of the transmitting station (e.g., a satellite). , and Indicates the speed of the irradiation source at the transmitting station. , and This indicates the acceleration of the irradiation source at the transmitting station. , and Indicates the position of the receiving station at reference time zero. , and Indicates the speed of the receiving station. , and This indicates the acceleration of the receiving station.
[0045] Further, the above-mentioned determination of deskewing parameters based on the echo signal, and deskewing of the echo signal according to the deskewing parameters to obtain the deskewing echo signal, includes: 1. Determine the deskewing parameters based on the echo spectrum of the echo signal. , This represents the first-order coefficient of the Doppler coefficients with respect to the azimuth center time.
[0046] in, , This represents the first-order slope of the distance.
[0047] More specifically, ; ; 2. Based on the deskew parameters, obtain the deskew phase. .
[0048] Based on the aforementioned Doppler analysis, due to the spatial variation of the Doppler centroid, azimuth spectrum may aliasing. In this case, it is necessary to equalize the centroid to achieve spectrum normalization. The aforementioned deskewing phase can be used as the spectrum normalization function.
[0049] 3. Multiply the echo signal sequentially with the filtered phase and the de-skewing phase to obtain the de-skewing echo signal.
[0050] The filter phase is represented as: .
[0051] It should be noted that during the de-tilting process, a linear distance migration correction function can be constructed first to compensate for the linear component of the RCM at the center reference point of the imaging scene and correct the spectral tilt, that is, to construct the above-mentioned filter phase.
[0052] After the above deskewing process, the de-encountered echo signal can be expressed as: .
[0053] Based on the above embodiments, the above-mentioned interpolation transformation of the de-skewed echo signal to obtain the interpolated echo signal includes: The de-skewed echo signal is then subjected to interpolation transformation to obtain the interpolated echo signal, which is represented as follows: The interpolation method used is: .
[0054] Specifically, in this embodiment, the de-skewed echo signal is subjected to Keystone transformation, specifically using an interpolation method. After the keystone transformation, the sampling rate in the azimuth direction changes, and the new sampling rate is denoted as... , and by Therefore, the echo signal after interpolation transformation can be expressed as: .
[0055] The first phase term represents the reference center point compensation phase; the second phase term includes the additional RCM introduced by azimuth deskewing and the azimuth spectral equalization phase; the third phase term includes higher-order RCM, secondary range frequency modulation phase, and azimuth phase. Furthermore, the range RCM contains a higher-order spatial variation term, and the Keystone transform introduces an additional range frequency modulation. In this embodiment, compensation is performed on the higher-order RCM and the range frequency modulation: The first step is to perform range migration correction by multiplying the transformed echo signal by the phase. : ; The second step involves a second range-direction pulse compression, followed by further multiplying the echo signal by its phase: ; The third step is to perform a distance-to-inverse Fourier transform.
[0056] Based on the above embodiments, range-oriented segmentation is performed, dividing the data into different strip-shaped sub-blocks along the range direction. Different sub-blocks are processed in parallel, and the Doppler parameters of each order in the sub-blocks are calculated. After performing range pulse compression on the echo signal as described above, the space-varying factor is calculated on the range history. Specifically, the range history is calculated with respect to the Doppler centroid. The space-variable factor. Among them, the Doppler centroid... as follows: ; in, To represent any target point, it can be expressed as: . and These represent the inner product of the velocity vector and position vector of the transmitting station and the receiving station, respectively.
[0057] Furthermore, it can be expressed as: .
[0058] in, and These represent the velocity vectors of the transmitting station and the receiving station, respectively. .
[0059] Furthermore, the Doppler modulation frequency is expressed as: ; in, , , and These represent the inner products of the corresponding vectors: ; ; ; ; in, and Let represent the acceleration vectors of the transmitting station and the receiving station, respectively, and they can be expressed as: ; .
[0060] Furthermore, the second and third order Doppler frequencies can be obtained, specifically as follows: ; .
[0061] in, , , and Let represent the inner product of the corresponding vectors, and let be calculated using the following expressions: ; ; ; .
[0062] Furthermore, based on the above embodiments, the Doppler space-variable coefficients of each order can be Taylor expanded to obtain... ; in, , and These represent the Doppler parameters of each order with respect to the Doppler centroid. The spatial variation coefficient.
[0063] It should be noted that multiple perturbations will be performed before subsequent imaging, because the Doppler parameters are related to the Doppler centroid. The spatially varying coefficients of each order have a significant impact on the calculation of the scaling factor. Furthermore, as the number of perturbations increases, the error of the spatially varying coefficients may have a greater impact on the scaling factor. In this embodiment, a more accurate method for calculating the scaling factor is further obtained.
[0064] The above , and It can be represented as: ; because It is about , The function is to find the Doppler space-variable coefficients of each order with respect to... The derivative function requires the introduction of the zero-time bistatic SAR range history. , can be represented as: ; Zero-time bistatic SAR distance history The expression is a double radical. If we want to solve it... , about and The analytical expression, and thus the calculation , and Therefore, for the bistatic SAR in this example, the calculation method for the rate of change of each order of distance history coefficients with respect to the azimuth center illumination time can be expressed as: ; ; ; In the above embodiments, iterative calculation formulas for each order of Doppler spatial variation coefficients are given, wherein the derivation process of the first order of each coefficient is as follows: ; in, , , , They are represented as follows: ; ; ; ; in, , , , , , These represent the inner product of any two vectors, with the subscript T or R indicating whether the variable belongs to the transmitting or receiving station, as shown below: ; ; ; ; ; ; It should be noted that the corresponding parameters can be in the same form for the receiving station.
[0065] in, , , and They can be represented as: ; ; ; ; ; also, , , and The higher-order components can be calculated using iterative formulas. and The derivation can be obtained through the following formula: ; This expression is also about Taking the derivative, we can obtain equation (1): ; in, , , and It can be calculated using the following expression: ; ; ; ; Based on the above derivation, equation (1) can be solved to obtain... and .
[0066] Figure 3A flowchart illustrating a fast imaging method for dual-base synthetic aperture radar according to another embodiment of this application is shown below. Figure 3 As shown, the above-mentioned method involves performing azimuth nonlinear scaling on the interpolated echo signal, calculating and obtaining the nonlinear scaling parameters, and then performing azimuth Fourier transform to obtain the final SAR image, including: S301. Determine the azimuth and orientation factors and the positioning factors.
[0067] Optionally, the range of values for the azimuth scaling factor and the range of values for the positioning factor that satisfy the preset conditions can be determined according to a preset expression.
[0068] The azimuth scaling factor can also be denoted as the perturbation factor corresponding to each order. , , , , and The positioning factor can be denoted as .
[0069] To achieve consistent processing of the azimuth signal, the spatially variable coupling term of the echo signal needs to be removed. , , , , and The expression can be written as: ; Since the denominators of each order component are all derived from... and The composition of each order of terms, then , This means that as the order increases, the components of the signal in the time domain decrease, so that while introducing disturbances, the inherent characteristics of the signal can be preserved as much as possible, thereby avoiding distortion or aliasing during time-frequency conversion. Furthermore, the following condition needs to be met: , ; And in settings When introducing disturbance terms, If the original characteristics of the signal are not affected during the process, then... ; In addition, due to the existence Therefore, it can be deduced that ; Combining the above equations and inequalities, the range of values for the positioning factor is: ; The range of values for the scaling factor can also be obtained as follows: , In summary, based on the above numerical derivation, we can obtain... , , , , , , .
[0070] S302. Based on the azimuth scaling factor and the positioning factor, perform high-order phase compensation and a first perturbation on the processed echo signal to obtain the echo signal after the first perturbation.
[0071] In the above Doppler calculation process, it can be seen that the spatial invariance of higher-order Doppler parameters can be ignored, and the higher-order phase compensation function can be obtained as follows: ; Furthermore, based on the aforementioned azimuth scaling factor and positioning factor, the phase expression corresponding to a single disturbance can be obtained: ; The processed echo signal can be multiplied sequentially by the higher-order phase compensation function and the phase expression corresponding to the first disturbance, and then subjected to an azimuth-to-Fourier transform to obtain the echo signal after the first disturbance.
[0072] After this, the echo signal can be converted to the azimuth frequency domain, and the azimuth phase can be expressed as: ; The first phase term represents the phase of the non-space-variable constant term, which can be compensated through consistent processing. The second, third, fourth, and fifth phase terms represent the space-variable coupling phases, respectively. , , and The non-space variable azimuth frequency modulation coefficient can be represented as follows: .
[0073] S303. Based on the azimuth scaling factor and the positioning factor, perform azimuth phase compensation and secondary perturbation on the echo signal after the first perturbation to obtain the echo signal after the second perturbation.
[0074] Among them, the non-empty variable term of azimuth phase compensation is multiplied by the azimuth compensation phase. : ; To introduce more azimuth degrees of freedom and to achieve azimuth spatial phase transformation, a second perturbation is performed.
[0075] Optionally, the phase expression corresponding to the secondary perturbation is obtained based on the azimuth scaling factor and the positioning factor. : ; That is, the echo signals after the above-mentioned perturbations are multiplied by... , The echo signal after the second disturbance is obtained.
[0076] S304. Perform an inverse Fourier transform on the echo signal after the above-mentioned secondary perturbation to obtain the final SAR image.
[0077] Optionally, after performing an inverse Fourier transform in the azimuth direction on the echo signal after the above-mentioned secondary perturbation, a secondary phase compensation in the azimuth direction can be performed. Specifically, it can be multiplied by a secondary compensation phase. The echo signal after secondary compensation is obtained, where: ; At this point, different target points have different Doppler centroids. Therefore, the signals fall in different locations. Then, an azimuth-to-Fourier transform is performed on the secondary compensated echo signal to obtain the final SAR image.
[0078] Based on the above embodiments, a complete imaging process of the dual-base synthetic aperture radar fast imaging method example in this application may include: 1. Obtain the echo signal.
[0079] 2. Perform a range-to-Fourier transform on the echo signal.
[0080] 3. Perform range pulse compression on the echo signal.
[0081] 4. Obtain the de-scratching parameters.
[0082] 5. Perform linear distance motion correction on the echo signal.
[0083] 6. De-skewing the echo signal.
[0084] 7. Perform interpolation transformation (keystone transformation) on the echo signal.
[0085] 8. Higher-order distance motion correction for echo signals.
[0086] 9. Secondary range pulse compression of the echo signal.
[0087] 10. Distance to Fourier Transform.
[0088] 11. Distance-oriented partitioning.
[0089] 12. Calculation of Doppler parameters for each sub-block.
[0090] 13. Sub-block Doppler parameters regarding Calculation of expansion coefficients.
[0091] 14. Calculation of nonlinear scaling parameters.
[0092] 15. Higher-order phase compensation for echo signals.
[0093] 16. A disturbance to the echo signal.
[0094] 17. Aspect-to-Fourier Transform.
[0095] 18. Azimuth phase compensation for echo signals.
[0096] 19. Secondary disturbance to the echo signal.
[0097] 20. Aspect-direction inverse Fourier transform.
[0098] 21. Secondary phase compensation for the azimuth direction of the echo signal.
[0099] 22. Azimuth Fourier transform is performed to obtain the final SAR image.
[0100] In this embodiment, the azimuth spectrum aliasing and range-azimuth two-dimensional coupling problems are solved simultaneously by de-skewing keystone transformation. Expanding the Doppler coefficients of each order about the Doppler centroid can effectively reduce the spatial variation order of the first-order azimuth phase term. Furthermore, the expansion about the Doppler centroid has good adaptability to the dual-base SAR imaging mode with beam rotation such as the spotting mode. This is because the Doppler centroid at different points along the azimuth in the imaging region is always changing. The expansion relative to the beam center illumination time can also be applied to the staring spotting mode, where the beam always points to a fixed point on the ground. The beam center illumination time at different points along the azimuth is zero, and azimuth equalization cannot be performed based on the beam center illumination time.
[0101] Furthermore, by introducing a limited number of degrees of freedom, azimuth equalization can be achieved in this embodiment, effectively reducing the number of azimuth Fourier transforms. In the clustering mode, conventional processing algorithms include time-domain back-projection and polar coordinate format algorithms. Time-domain algorithms require phase compensation and curve integration for each target point, resulting in low processing efficiency. Polar coordinate format algorithms in the clustering mode typically require compensation for higher-order wavefront bending errors, necessitating two-dimensional block division. However, this embodiment only requires block division along the range direction, effectively improving processing efficiency compared to traditional clustering mode processing algorithms.
[0102] Figure 4This is a schematic diagram of an application scenario in a dual-base synthetic aperture radar fast imaging method provided in an embodiment of this application. Since imaging processing methods usually have a better focusing effect on the center point, while the edge points usually have a relatively poor processing effect due to the spatial variability of azimuth phase and range history.
[0103] like Figure 4 As shown, multiple target points are specified in this application scenario. Optionally, the rectangular scene is sampled at equal intervals, and nine target points are set. The effectiveness of the proposed method can be demonstrated by the imaging effect of the scene center point (target 5) and all edge points (other target points).
[0104] Furthermore, the above-mentioned dual-base synthetic aperture radar fast imaging method was verified using simulation parameters, which are shown in Table 1 below: Table 1
[0105] Figure 5 This is a schematic diagram of the simulated imaging result in a dual-base synthetic aperture radar fast imaging method provided in the embodiments of this application, namely... Figure 5 (a)-(i) is based on Figure 4 The simulation results for the target are shown in the figure. (e) represents the imaging result corresponding to the center point (target 5), and the other images represent the imaging results corresponding to the target points at the edge of the imaging scene. As can be seen from the figure, high-precision focusing can be achieved for both the center point and the target points at the edge of the scene. Therefore, it can be shown that the method in this embodiment can achieve high-precision spectral normalization, two-dimensional decoupling of echoes, and azimuth equalization of complex trajectory dual-baseline SAR echoes in the spotting mode.
[0106] In summary, it can be seen that the above-mentioned rapid imaging method of bistatic synthetic aperture radar can effectively realize the imaging processing of complex trajectories of bistatic SAR in large-angle-focused spotting mode, and can achieve precise focusing of bistatic SAR echoes.
[0107] This application also provides an electronic device, including a processor and a memory, and optionally, a bus. The memory stores machine-readable instructions executable by the processor. When the electronic device is running, the processor communicates with the memory via the bus, and the processor executes the machine-readable instructions to perform the aforementioned dual-base synthetic aperture radar rapid imaging method.
[0108] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the above-described dual-base synthetic aperture radar rapid imaging method.
[0109] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.
Claims
1. A fast imaging method for dual-base synthetic aperture radar, characterized in that, Applied to receiving stations, including: Based on the transmitted signal emitted in the beam-focusing mode of the transmitting station, the echo signal is received and acquired; Based on the echo signal, the deskewing parameters are determined, and the echo signal is deskewed according to the deskewing parameters to obtain the deskewed echo signal; The de-skewed echo signal is subjected to interpolation transformation to obtain the interpolated echo signal; The interpolated echo signal is nonlinearly scaled in the azimuth direction, and the nonlinear scaling parameters are calculated. The final SAR image is obtained by azimuth Fourier transform.
2. The method according to claim 1, characterized in that, The echo signal is represented as: ； in, Indicates the target point The scattering coefficient, Indicates the coordinates of the target point. and These represent the range and azimuth antenna radiation patterns, respectively. Indicates distance in terms of time. Indicates the range frequency. Indicates the range-direction frequency modulation slope. Represents the speed of light. Indicates the pulse width. Indicates direction in slow time; j is the imaginary sign in the complex number. Indicates the time for synthesizing the aperture. Indicates the time of illumination at the center of the target point; After receiving and acquiring the echo signal from the transmitted signal emitted in the beam-focusing mode of the transmitting station, the method further includes: The echo signal is subjected to range pulse compression based on the compensation phase to obtain the compensated echo signal, wherein the compensation phase is... The compensated echo signal is represented as follows: 。 3. The method according to claim 2, characterized in that, The Represented as: ； in, The ground projection representing the oblique angle of the receiving station. Indicates the beamwidth of the receiving station. This indicates the ground movement speed of the receiving station beam. , This indicates the velocity of the receiving station along the y-axis. This represents the beam control factor of the receiving station and is expressed as a function of the antenna's azimuth and rotation speed. Decide; Represented as: ;in, Indicates the location and time Reference distance of the receiving station A marker indicating the beam imaging mode of the receiving station; where, 。 4. The method according to claim 2, characterized in that, The step of determining deskewing parameters based on the echo signal and deskewing the echo signal based on the deskewing parameters to obtain a deskewing echo signal includes: The deskewing parameter is determined based on the echo spectrum of the echo signal. , This represents the first-order coefficient of the Doppler coefficients with respect to the azimuth center time, where, ,in, Indicates the first-order slope of the distance; Based on the de-skew parameters, the de-skew phase is obtained. ; The echo signal is multiplied sequentially by the filtered phase and the de-skewed phase to obtain the de-skewed echo signal, wherein the filtered phase is represented as follows: 。 5. The method according to claim 4, characterized in that, The step of interpolating the de-skewed echo signal to obtain the interpolated echo signal includes: The de-skewed echo signal is interpolated to obtain the interpolated echo signal, which is represented as follows: The interpolation method used is: .
6. The method according to claim 5, characterized in that, The step of performing azimuth nonlinear scaling on the interpolated echo signal, calculating and obtaining the nonlinear scaling parameters, and obtaining the final SAR image through azimuth Fourier transform includes: Determine the azimuth rate adjustment factor and the positioning factor; Based on the azimuth scaling factor and the positioning factor, the processed echo signal is subjected to higher-order phase compensation and a first perturbation to obtain the echo signal after the first perturbation. Based on the azimuth scaling factor and the positioning factor, the echo signal after the first disturbance is subjected to azimuth phase compensation and a second disturbance to obtain the echo signal after the second disturbance. The azimuth-direction inverse Fourier transform is performed on the echo signal after the secondary perturbation to obtain the final SAR image.
7. The method according to claim 6, characterized in that, The determination of the azimuth calibration factor and the positioning factor includes: Based on the preset expression, determine the range of values for the azimuth scaling factor and the range of values for the positioning factor that satisfy the preset conditions.
8. The method according to claim 6, characterized in that, The step of performing high-order phase compensation and a first perturbation on the processed echo signal based on the azimuth scaling factor and the positioning factor to obtain a perturbed echo signal includes: Based on the azimuth scaling factor and the positioning factor, obtain the phase expression corresponding to the first disturbance; The processed echo signal is subjected to high-order phase compensation, and a perturbation is performed according to the phase expression corresponding to the first perturbation. The step of performing azimuth phase compensation and secondary perturbation on the echo signal after the first perturbation based on the azimuth scaling factor and the positioning factor to obtain the echo signal after the second perturbation includes: Based on the azimuth scaling factor and the positioning factor, obtain the phase expression corresponding to the secondary disturbance; The echo signal after the first disturbance is subjected to azimuth phase compensation, and a second disturbance is performed according to the phase expression corresponding to the second disturbance.
9. An electronic device, characterized in that, include: A processor and a memory, the memory storing machine-readable instructions executable by the processor, the processor executing the machine-readable instructions to perform the dual-base synthetic aperture radar rapid imaging method as described in any one of claims 1 to 8.
10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, performs the dual-base synthetic aperture radar rapid imaging method as described in any one of claims 1 to 8.