Synthetic Aperture Radar Frequency Shift Jam Azimuth Defocus Quantization and Compensation Method and Device

Abstract

This invention discloses a method and apparatus for quantifying and compensating for azimuth defocus in synthetic aperture radar (SAR) frequency-shift interference, belonging to the field of radar countermeasures technology. First, the intercepted SAR signal undergoes mixing processing and parameter estimation, and is sampled and stored to obtain a digital baseband signal. Then, a frequency shift amount is set according to the preset interference point position, and a frequency-shift modulation signal is generated. This signal is multiplied by the digital baseband SAR signal to obtain the uncompensated frequency-shift interference signal. Further, a mathematical relationship between the azimuth defocus amount and the frequency shift amount of the false target is established, a phase compensation value is calculated, and a phase compensation signal is generated. This phase compensation signal is multiplied by the uncompensated frequency-shift interference signal to complete the compensation modulation. Finally, after digital-to-analog conversion and up-conversion processing, the signal is relayed pulse-by-pulse to the target SAR system. This invention effectively addresses the frequency modulation mismatch and defocusing problems of frequency-shift interference by compensating only the azimuth phase, significantly improving the imaging quality and interference effect of false targets.

Description

Technical Field

[0001] This invention belongs to the field of radar countermeasures technology, specifically relating to a method and apparatus for quantifying and compensating for azimuth defocus in synthetic aperture radar frequency shift interference. Background Technology

[0002] Synthetic Aperture Radar (SAR) is a microwave-based Earth observation radar. Compared to optical radar, it offers all-weather, all-day operation and high resolution, making it widely used in fields where optical and infrared detection systems are limited, such as agricultural exploration, topographic mapping, marine monitoring, and military reconnaissance. Based on energy source, SAR jamming can be divided into passive and active jamming. Passive jamming derives its energy from external electromagnetic waves, altering the propagation and imaging characteristics of the SAR echo signal through reflection, scattering, or absorption, thus interfering with SAR imaging. Active jamming refers to jamming equipment actively emitting jamming signals, which, after processing by the SAR system, produce false patches, false moving targets, and false scenes, ultimately preventing the SAR system from correctly identifying the original ground targets. Based on the jamming effect, active jamming can be divided into suppression jamming and deception jamming. Suppression jamming requires the jammer to emit noise signals to mask the SAR echo signal, causing regional blurring in the imaging results and affecting image quality. Deception jamming utilizes jammers to emit jamming signals that simulate the scattering characteristics of specific targets, creating false targets or false scenes after processing by the SAR system. Frequency-shift jamming, as a typical active jamming technique, can generate false targets with shifted positions. However, the false targets generated by this jamming method suffer from azimuth defocusing, resulting in poor jamming effectiveness and making them easier to detect and identify. Therefore, this invention analyzes and studies this problem and proposes a compensation method for the azimuth defocusing problem of frequency-shift jamming.

[0003] CN119414345A proposes a method, apparatus, storage medium, and device for generating two-dimensional modulated jamming signals. It combines range-direction phase-coded modulation, azimuth-direction quadratic sine function modulation, range-direction frequency-shift modulation, and azimuth-direction frequency-shift modulation to flexibly generate six different types of two-dimensional jamming effects while precisely controlling the center position of the jamming result. CN119493084A proposes a region-adjustable intermittent sampling jamming method and system for UAV SAR platforms. This invention combines range-direction frequency-shift modulation and modulation based on the characteristics of false moving targets, generating false jamming signals with certain motion characteristics. Both inventions introduce frequency-shift modulation without compensation, resulting in defocusing issues in the jamming results of simulation experimental images. The imaging quality of false targets is poor, making them easily identifiable. Existing frequency-shift jamming technologies lack quantitative research on the azimuth defocusing problem of the jamming results. Summary of the Invention

[0004] This invention addresses the above-mentioned technical problems by proposing a method and apparatus for quantifying and compensating for azimuth defocus in synthetic aperture radar (SAR) frequency-shift interference. First, this invention analyzes the azimuth defocus problem inherent in frequency-shift interference, establishes the calculation relationship between the frequency shift amount and the azimuth broadening of the interference result, and further proposes a compensation method for azimuth defocus in the interference result. Furthermore, this invention only requires adding azimuth phase compensation to obtain good false targets, significantly improving the imaging effect of frequency-shift interference. The specific technical solution is as follows:

[0005] A method for quantifying and compensating for azimuth defocusing caused by frequency-shifting interference in synthetic aperture radar includes the following steps:

[0006] Step 1: The jammer first performs mixing processing on the intercepted SAR signal to obtain the baseband SAR signal. Then, it samples and stores the baseband SAR signal to obtain the digital baseband SAR signal. At the same time, it performs parameter estimation to obtain the signal operating frequency, pulse duration, and linear modulation frequency.

[0007] Step 2: The jammer sets the required frequency shift amount according to the preset jamming point location and signal detection parameters and generates the corresponding frequency shift modulation signal. Then, the frequency shift modulation signal is multiplied with the digital baseband SAR signal to complete the frequency shift modulation and obtain the frequency shift jamming digital signal before compensation.

[0008] Step 3: Pass the uncompensated frequency-shift interference digital signal through the imaging model to obtain the azimuth modulation frequency of the interference signal; at the same time, establish the mathematical relationship between the azimuth defocus of the false target generated by the uncompensated frequency-shift interference digital signal and the frequency shift based on the imaging model, further derive the phase compensation value required for the frequency-shift interference digital signal and generate the corresponding phase compensation signal, then the jammer multiplies the phase compensation signal with the uncompensated frequency-shift interference digital signal to complete the compensation modulation and obtain the compensated frequency-shift interference digital signal;

[0009] Step 4: The jammer converts the compensated frequency-shifting jamming digital signal into a frequency-shifting jamming analog signal through digital-to-analog conversion. Then, it up-converts the frequency-shifting jamming analog signal and forwards it pulse by pulse to the target SAR system. The target SAR system down-converts, performs analog-to-digital conversion, and imaging processing on the received frequency-shifting jamming analog signal to produce an imaging result that includes false point targets.

[0010] A synthetic aperture radar frequency shift interference azimuth defocus quantization and compensation device includes:

[0011] The system comprises the following modules: a signal receiving module for intercepting SAR signals; a down-conversion module for mixing the intercepted SAR signals to obtain baseband SAR signals; an analog-to-digital conversion module for converting baseband SAR signals into digital baseband SAR signals; a signal parameter measurement module for measuring the operating frequency, pulse duration, and linear frequency modulation parameters of the intercepted SAR signals; a frequency-shifting jamming module for setting the frequency shift amount and generating corresponding frequency-shifting jamming digital signals based on the target location and signal operating parameters; a defocusing quantization module for establishing the mathematical relationship between defocusing and frequency shifting under the specified operating parameters; a phase compensation module for obtaining an azimuth compensation phase signal through a mathematical model of the relationship between defocusing and frequency shifting, and multiplying this signal with the frequency-shifting jamming digital signal to obtain a compensated frequency-shifting jamming digital signal; a digital-to-analog conversion module for converting the compensated frequency-shifting jamming digital signal into a frequency-shifting jamming analog signal; an up-conversion module for mixing the frequency-shifting jamming analog signal with a high-frequency carrier to obtain a signal suitable for transmission; and a transmission module for sending the signal processed by the jammer back to the target SAR system.

[0012] An electronic device includes: one or more processors; and a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method.

[0013] A computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, cause the processor to implement the method described thereon.

[0014] The present invention has the following beneficial effects:

[0015] This invention proposes a method for quantifying the azimuth defocus of frequency-shift interference and a compensation method for the azimuth defocus problem. This method only requires adding an azimuth-related compensation phase to achieve good false target imaging results, thereby effectively improving the computational efficiency and real-time performance of the jammer.

[0016] This invention effectively quantifies the image defocus caused by frequency shift, providing a direct key parameter for phase compensation. Furthermore, by adding azimuth compensation phase, it effectively alleviates the frequency modulation mismatch and defocusing problems associated with frequency shift interference, significantly improving the imaging quality of frequency shift interference signals. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method of the present invention.

[0018] Figure 2 This is a physical model diagram of a jammer performing frequency-shifting jamming on a SAR system.

[0019] Figure 3This is a schematic diagram of frequency modulation mismatch proposed in this invention.

[0020] Figure 4 This is a simulation diagram of a point target under ideal conditions.

[0021] Figure 5 This is the image of the interference point target when the frequency shift is -15MHz.

[0022] Figure 6 This is the image of the interference point target when the frequency shift is 18MHz.

[0023] Figure 7 The image shows the results of the interference point target imaging before and after applying the compensation method proposed in this invention when the frequency shift is -15MHz.

[0024] Figure 8 The images show the results of the interference point target imaging before and after applying the compensation method proposed in this invention when the frequency shift is 18MHz.

[0025] Figure 9 This is an example diagram of the framework of a spaceborne synthetic aperture radar frequency shift interference azimuth defocus quantification and compensation device according to the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, the invention adopts the following technical solutions.

[0027] The purpose of this invention is to provide a method for quantifying and compensating for azimuth defocus in synthetic aperture radar frequency shift interference, comprising the following steps:

[0028] Step 1: The jammer first performs mixing processing on the intercepted SAR signal to obtain the baseband SAR signal. Then, it samples and stores the baseband SAR signal to obtain the digital baseband SAR signal. At the same time, it performs parameter estimation to obtain parameters such as signal operating frequency, pulse duration, and linear modulation frequency.

[0029] Step 2: The jammer sets the required frequency shift amount according to the preset jamming point location and signal detection parameters and generates the corresponding frequency shift modulation signal. Then, the frequency shift modulation signal is multiplied with the digital baseband SAR signal to complete the frequency shift modulation and obtain the frequency shift jamming digital signal before compensation.

[0030] Step 3: Calculate the azimuth modulation frequency of the frequency-shift interference signal before compensation based on the imaging model; at the same time, establish the mathematical relationship between the azimuth defocus of the false target generated by the frequency-shift interference digital signal before compensation and the frequency shift amount based on the imaging model, further derive the phase compensation value required for the frequency-shift interference digital signal and generate the corresponding phase compensation signal, then the jammer multiplies the phase compensation signal with the frequency-shift interference digital signal before compensation to complete the compensation modulation and obtain the compensated frequency-shift interference digital signal;

[0031] Step 4: The jammer converts the compensated frequency-shifting jamming digital signal into a frequency-shifting jamming analog signal via digital-to-analog conversion. Then, it up-converts the analog signal and forwards it pulse-by-pulse to the target SAR system. The target SAR system down-converts, performs analog-to-digital conversion, and performs imaging processing on the received analog signal to generate an imaging result that includes false point targets.

[0032] The present invention will now be described in detail with reference to the accompanying drawings.

[0033] The overall process of the synthetic aperture radar frequency shift interference azimuth defocus quantization and compensation method proposed in this invention is as follows: Figure 1 As shown. The geometric scenario of a jammer performing frequency-shifting jamming on a SAR system is as follows. Figure 2 As shown. The SAR system is set to operate in frontal-side-looking stripe mode at an altitude of H. It flies at high speed. Figure 2 Using the SAR system's velocity direction as the x-axis and the perpendicular direction of the velocity as the y-axis, a slow time is set. The projection of the SAR system onto the ground is taken as the origin. The jammer is positioned at the center of the strip along the positive x-axis, with its shortest slant range being... Then the instantaneous slant range of the jammer relative to the SAR system is .

[0034] After intercepting the SAR system's transmitted signal, the jammer first estimates the signal parameters, determining the operating frequency and other parameters. Then, it mixes the signal with the local oscillator signal using a mixer to obtain the baseband SAR signal. This baseband signal is further converted to a digital baseband SAR signal through analog-to-digital conversion. Subsequently, the jammer sets the required frequency shift based on the preset jamming point location and signal parameters, and compensates for it, generating a compensated frequency-shifted jamming digital signal. In the transmission module, the jammer first performs digital-to-analog conversion on the compensated frequency-shifted jamming digital signal to obtain a compensated frequency-shifted jamming analog signal. This signal is transmitted pulse-by-pulse at a certain power and is received and processed by the target SAR system, ultimately achieving the jamming effect on the target SAR system.

[0035] The specific implementation process of step one is as follows.

[0036] SAR system transmits radar signals The expression is as follows:

[0037] ;

[0038] Where τ represents the distance-time dimension, Indicates the pulse duration. Indicates the operating frequency. Indicates frequency modulation. The imaginary unit, For rectangle functions, This represents an exponential function.

[0039] After the radar signal propagates, the signal received by the jammer is expressed as follows:

[0040] ;

[0041] in, It is the speed of light.

[0042] The jammer's receiving module multiplies this signal by the local oscillator signal to obtain the baseband SAR signal, and then estimates the parameters contained in the SAR signal. , After considering the operating parameters, the digital baseband SAR signal expression is obtained through analog-to-digital conversion as follows:

[0043] ;

[0044] The specific implementation process of step two is as follows:

[0045] The jammer determines the frequency shift based on the signal's operating parameters and the preset target location of the jamming point. False target distance offset to position The mathematical relationship between the frequency shift and the frequency shift amount is shown below:

[0046] ;

[0047] Based on the frequency shift amount, the expression for the frequency-shifted modulation signal is as follows:

[0048] ;

[0049] Next, the jammer generates a corresponding frequency-shift modulation signal and multiplies it with the digital baseband SAR signal to obtain the following expression for the frequency-shift jamming digital signal:

[0050] ; in, Indicates the signal amplitude.

[0051] The specific implementation process of step three is as follows:

[0052] Based on the relevant parameters estimated from the intercepted SAR system transmitted signals and the preset frequency shift amount, the azimuth modulation frequency of the interference signal can be obtained. The expression is as follows:

[0053] ;

[0054] Frequency modulation of the azimuth echo of the ideal point target corresponding to the location of the false target The expression is as follows:

[0055] ;

[0056] in, The minimum slant distance of a false point target is represented by its relationship with... The relationship is as follows:

[0057] ;

[0058] Due to the frequency modulation of the interference signal's azimuth Frequency modulation of the azimuth echo of the ideal point target corresponding to the location of the false target There are differences between them. When the SAR system performs azimuth matched filtering on frequency-shifting interference signals, there is a frequency modulation mismatch, which ultimately leads to azimuth defocusing. A schematic diagram of frequency modulation mismatch is shown below. Figure 3 As shown. Azimuth defocusing amount The mathematical model for the frequency shift is shown below:

[0059] ;

[0060] To solve the azimuth defocusing problem, the jammer needs to add an azimuth compensation phase value to the jamming signal to match its frequency modulation (FM) with the matched filter. According to step two, the FM mismatch between the two can be expressed as follows:

[0061] ;

[0062] The expression for the compensation phase value added by the jammer is as follows:

[0063] ;

[0064] Therefore, the digital expression of the frequency shift interference signal after phase compensation by the jammer is as follows:

[0065] ;

[0066] The specific implementation process of step four is as follows:

[0067] The jammer converts the compensated digital frequency-shift interference signal to analog signal via digital-to-analog conversion and up-conversion to obtain a compensated analog frequency-shift interference signal, which is then transmitted to the target SAR system. The expression for the compensated analog frequency-shift interference signal is as follows:

[0068] ;

[0069] The SAR system performs down-conversion, quadrature demodulation, analog-to-digital conversion, and imaging processing on the received frequency-shifting interference signal. The results are shown below:

[0070] ; in, denoted as the synthesis aperture time, and sinc represents the sinusoidal basis function.

[0071] The above equation shows that after adding the compensation phase, the frequency shift interference signal can generate a well-focused false target with a distance-direction position shift, which effectively solves the problem of azimuth defocus of false targets in traditional frequency shift interference methods and improves the imaging quality of false targets.

[0072] The theoretical model of this invention will be verified and analyzed based on the simulation results below.

[0073] First, during the experimental verification process, the operating parameters of the SAR system were set as follows: the radar operating frequency was 5.3 GHz, the pulse duration was 40 μs, the effective velocity of the SAR system was 7100 m / s, the slant range of the scene center was 850 km, the radar signal modulation frequency was 0.5 × 10¹² Hz / s, and the azimuth resolution was 5 m. Under ideal conditions, its point target imaging simulation is as follows: Figure 4 As shown in (a) and (b). Figure 4 (a) is the image of the point target. Figure 4 (b) is an azimuth nematic slice with an azimuth PSLR of -12.5620dB, an azimuth ISLR of -11.7837dB, and an azimuth IRW of 4.9269m, which meets the imaging requirements and is consistent with the working parameters.

[0074] Next, the method for calculating the amount of defocus proposed in this invention was verified.

[0075] With the SAR system operating parameters unchanged and the frequency shift set to -15MHz, the proposed method calculates a theoretical defocusing value of 16.5676m. Substituting this value into the frequency shift value for simulation imaging yields the following results: Figure 5 As shown in (a) and (b), it is basically consistent with the theoretical analysis. Among them, Figure 5 (a) is the image of the point target. Figure 5 (b) is an azimuth nematic slice.

[0076] With the SAR system operating parameters unchanged and the frequency shift set to 18MHz, the method proposed in this invention calculates a theoretical defocus value of 19.8887m. Substituting this value into the frequency shift value for simulation imaging yields the following results: Figure 6 As shown in (a) and (b), it is basically consistent with the theoretical analysis. Among them, Figure 6 (a) Image result of the point target. Figure 6 (b) Azimuth nematic slice diagram.

[0077] The effectiveness of the defocusing compensation method proposed in this invention is then verified.

[0078] With the SAR system operating parameters unchanged and the frequency shift set to -15MHz, the compensation phase proposed in this invention is added to the interference signal for imaging simulation. The compensated azimuth PSLR and ISLR results should both be below -11dB, and the azimuth IRW should be around 5m. The results before and after compensation are as follows: Figure 7 As shown in (a), (b), (c), and (d), the results are basically consistent with the theoretical analysis. Figure 7 (a) is the image of the target at the point of compensation. Figure 7 (b) is a compensated front-side matrix slice. Figure 7 (c) is the image of the point target after compensation. Figure 7 (d) is the compensated azimuth nematic slice.

[0079] With the SAR system operating parameters unchanged and the frequency shift set to 18MHz, the compensation phase proposed in this invention is added to the interference signal for imaging simulation. The compensated azimuth PSLR and ISLR results should both be below -11dB, and the azimuth IRW should be around 5m. The results before and after compensation are as follows: Figure 8 As shown in (a), (b), (c), and (d), the results are basically consistent with the theoretical analysis. Figure 8 (a) is the image of the target at the point of compensation. Figure 8 (b) is a compensated front-side matrix slice. Figure 8 (c) is the image of the point target after compensation. Figure 8 (d) is the compensated azimuth nematic slice.

[0080] Based on the above theoretical model derivation and simulation results, it can be seen that the relationship model between the frequency shift and azimuth defocus of the spaceborne synthetic aperture radar proposed in this invention is basically accurate, and the azimuth compensation method can effectively alleviate the azimuth defocus problem caused by the frequency shift interference of the spaceborne synthetic aperture radar.

[0081] The present invention provides a synthetic aperture radar frequency shift interference azimuth defocus quantization and compensation device, such as... Figure 9As shown, its various modules can implement the various steps of the aforementioned method, specifically including:

[0082] The system comprises the following modules: a signal receiving module for intercepting radar signals transmitted by the SAR system; a down-conversion module for mixing the intercepted SAR signals to obtain baseband SAR signals; an analog-to-digital conversion module for converting analog baseband SAR signals into digital baseband SAR signals; a signal parameter measurement module for measuring the operating parameters of the intercepted SAR signals, such as operating frequency, pulse width, bandwidth, and frequency modulation; a frequency-shift jamming module for setting the frequency shift amount based on the target location and signal operating parameters and generating corresponding frequency-shift jamming digital signals; a defocus quantization module for establishing the mathematical relationship between defocus and frequency shift under the specified operating parameters; a phase compensation module for obtaining an azimuth compensation phase signal through a mathematical model of the relationship between defocus and frequency shift, and multiplying this signal with the frequency-shift jamming digital signal to obtain a compensated frequency-shift jamming digital signal; a digital-to-analog conversion module for converting the compensated frequency-shift jamming digital signal into a frequency-shift jamming analog signal; an up-conversion module for mixing the frequency-shift jamming analog signal with a high-frequency carrier to obtain a signal suitable for transmission; and a transmission module for sending the signal processed by the jammer back to the target SAR system.

[0083] The present invention also provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method.

[0084] The present invention also provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, cause the processor to implement the method described thereon. Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0085] The above description is based on flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowcharts and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0087] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0088] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

Claims

1. A method for quantifying and compensating azimuth defocusing of frequency shift jamming in synthetic aperture radar, characterized in that, Includes the following steps: Step 1: The jammer first performs mixing processing on the intercepted SAR signal to obtain the baseband SAR signal. Then, it samples and stores the baseband SAR signal to obtain the digital baseband SAR signal. At the same time, it performs parameter estimation to obtain the signal operating frequency, pulse duration, and linear modulation frequency. Step 2: The jammer sets the required frequency shift amount according to the preset jamming point location and signal detection parameters and generates the corresponding frequency shift modulation signal. Then, the frequency shift modulation signal is multiplied with the digital baseband SAR signal to complete the frequency shift modulation and obtain the frequency shift jamming digital signal before compensation. Step 3: Pass the uncompensated frequency-shift interference digital signal through the imaging model to obtain the azimuth modulation frequency of the interference signal; at the same time, establish the mathematical relationship between the azimuth defocus of the false target generated by the uncompensated frequency-shift interference digital signal and the frequency shift based on the imaging model, further derive the phase compensation value required for the frequency-shift interference digital signal and generate the corresponding phase compensation signal, then the jammer multiplies the phase compensation signal with the uncompensated frequency-shift interference digital signal to complete the compensation modulation and obtain the compensated frequency-shift interference digital signal; Step 4: The jammer converts the compensated frequency-shifting jamming digital signal into a frequency-shifting jamming analog signal through digital-to-analog conversion. Then, it up-converts the frequency-shifting jamming analog signal and forwards it pulse by pulse to the target SAR system. The target SAR system down-converts, performs analog-to-digital conversion, and imaging processing on the received frequency-shifting jamming analog signal to produce an imaging result that includes false point targets.

2. The method of claim 1, wherein, The specific implementation process of step one is as follows: SAR systems transmit radar signals The expression is as follows: ； where τ denotes the distance to time, denotes the pulse duration, denotes the operating frequency, denotes the frequency modulation rate, is the imaginary unit, is the rectangular function, denotes the exponential function; After the radar signal propagates, the SAR signal received by the jammer is expressed as follows: ； wherein, is the speed of light, is the instantaneous slant range of the jammer relative to the SAR system; the receiving module of the jammer multiplies the signal with the local signal to obtain the baseband SAR signal, and obtains the through parameter estimation , each working parameter, and finally through analog-digital conversion, the expression of the digital baseband SAR signal is as follows: 。 3. The method of claim 2, wherein the method comprises: determining a plurality of azimuthal defocus values for a plurality of azimuthal directions; and determining a plurality of azimuthal defocus compensation values for the plurality of azimuthal directions based on the plurality of azimuthal defocus values. The specific implementation process of step two is as follows: The jammer determines the frequency shift amount according to the working parameters of the signal and the preset target position of the jamming point , the false target distance position offset The mathematical relationship between the frequency shift amount and the jamming point target position is shown as follows: ； Based on the frequency shift amount, the expression for the frequency-shifted modulation signal is as follows: ； Next, the jammer generates a corresponding frequency-shift modulation signal and multiplies it with the digital baseband SAR signal to obtain the following expression for the frequency-shift jamming digital signal: ， wherein represents the signal amplitude.

4. The method of claim 3, wherein, in, The specific implementation process of step three is as follows: According to the correlation parameters estimated from the intercepted SAR system transmitting signal and the preset frequency shift amount, the frequency modulation rate of the interference signal in the azimuth direction is obtained The expression is as follows: ； This represents the shortest slant range between the jammer and the SAR system. For SAR system velocity, the azimuth modulation frequency of the echo from the ideal point target corresponding to the location of the false target. The expression is as follows: ； in, This represents the shortest slant range between the false point target and the SAR system, and its relationship with... The relationship is as follows: ； The jammer adds an azimuth-oriented compensation phase value to the jamming signal to match its frequency modulation (FM) with the matched filter. According to step two, the FM mismatch between the two can be expressed as follows: ； The expression for the compensation phase value added by the jammer is as follows: ； Therefore, the digital expression of the frequency shift interference signal after phase compensation by the jammer is as follows: 。 5. The method for quantifying and compensating for azimuth defocusing in synthetic aperture radar frequency shift interference according to claim 1, characterized in that, The specific implementation process of step four is as follows: The jammer converts the compensated digital frequency-shift interference signal to analog signal via digital-to-analog conversion and up-conversion to obtain a compensated analog frequency-shift interference signal, which is then transmitted to the target SAR system. The expression for the compensated analog frequency-shift interference signal is as follows: ； The target SAR system performs down-conversion, quadrature demodulation, analog-to-digital conversion, and imaging processing on the received frequency-shifting interference analog signal. The results are shown below: ， in, denoted as the synthesis aperture time, and sinc represents the sinusoidal basis function.

6. The method for quantifying and compensating for azimuth defocusing in synthetic aperture radar frequency shift interference according to claim 1, characterized in that, The specific geometric scenario for a jammer to perform frequency-shift jamming on a SAR system is as follows: The SAR system is set to a front-side-looking stripe operating mode and is on an orbit at altitude H... The system flies at a speed where the SAR system's velocity direction is the x-axis and the perpendicular direction to the velocity direction is the y-axis, with a slow time set. The projection of the SAR system onto the ground is taken as the origin. The jammer is positioned at the center of the strip along the positive x-axis, with its shortest slant range being... Then the instantaneous slant range of the jammer relative to the SAR system is .

7. The synthetic aperture radar frequency shift interference azimuth defocus quantization and compensation method according to claim 4, characterized in that, Azimuth defocus The mathematical model for the frequency shift is shown below: 。 8. A synthetic aperture radar frequency shift interference azimuth defocus quantization and compensation device, characterized in that, include: The signal receiving module is used to intercept SAR signals; The down-conversion module performs mixing processing on the intercepted SAR signal to obtain the baseband SAR signal; The analog-to-digital conversion module converts baseband SAR signals into digital baseband SAR signals; The signal parameter measurement module is used to measure the operating frequency, pulse duration, and linear frequency modulation parameters of the intercepted SAR signal; the frequency shift interference module is used to set the frequency shift amount according to the target location of the interference point and the signal operating parameters and generate the corresponding frequency shift interference digital signal; the defocus quantization module establishes the mathematical relationship between the defocus amount and the frequency shift amount under the operating parameters. The phase compensation module obtains the azimuth compensation phase signal through a mathematical relationship model between defocus and frequency shift, and multiplies this signal with the frequency shift interference digital signal to obtain the compensated frequency shift interference digital signal. The digital-to-analog converter module is used to convert the compensated frequency-shift interference digital signal into a frequency-shift interference analog signal; the up-conversion module is used to mix the frequency-shift interference analog signal with a high-frequency carrier to obtain a signal that is easy to transmit; the transmission module is used to send the signal processed by the jammer back to the target SAR system.

9. An electronic device, characterized in that, include: One or more processors; A memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the synthetic aperture radar frequency shift interference azimuth defocus quantization and compensation method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores executable instructions that, when executed by a processor, cause the processor to implement the synthetic aperture radar frequency shift interference azimuth defocus quantization and compensation method according to any one of claims 1 to 7.

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