Antenna pattern measurement method based on segmented gain variable threshold single-bit receiver

Abstract

The invention specifically discloses an antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver, and relates to the technical field of synthetic aperture radar radiometric calibration. The method comprises the following steps: analyzing a monotonic relationship between quantized signal power and STR, and establishing a quantitative model; constructing a received signal amplitude reconstruction strategy of all sampling rates and SAR bandwidth ratios; determining the maximum amplitude and the minimum amplitude of the received signal, segmenting the amplitude of the received signal, and setting a threshold value; analyzing the signal spectrum and estimating quantized signal power; calculating the STR and the actual received signal power; and calculating azimuth and distance antenna pattern sampling values, calculating azimuth dimension and pitching dimension gains of the radar antenna according to a radar equation, and reconstructing an antenna pattern by using polynomial fitting. According to the invention, the structure of a radar pattern gain measurement receiver is simplified, the cost is reduced, the measurement precision is guaranteed, and the large-scale deployment and high-precision estimation requirements of an SAR radiometric calibration active receiver can be met.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of synthetic aperture radar radiation calibration, and in particular to an antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver. BACKGROUND

[0002] Synthetic aperture radar (SAR) has been widely applied in key fields such as disaster dynamic monitoring, ecological environment evaluation and national defense security warning due to its stable observation ability and high-resolution imaging advantage. In recent years, with the continuous breakthrough of miniaturization technology, the rapid rise of commercial aerospace industry and low-altitude economy promotes the transformation of SAR remote sensing technology from traditional qualitative analysis to high-precision quantitative research, which puts forward higher requirements for the accuracy of SAR system performance calibration.

[0003] Radiation calibration, as the core technology to ensure the performance calibration of the SAR system, is an important basis for ensuring the consistency and comparability of SAR data at different times and in different regions, and the accurate measurement of the antenna pattern is an indispensable key link in the radiation calibration process, and the measurement accuracy directly affects the reliability of SAR quantitative application.

[0004] At present, the commonly used antenna pattern measurement methods in the industry mainly include corner reflector method, natural distribution target method, ground receiver method and model-based measurement method, but the existing technical solutions all have significant limitations: the corner reflector method has the characteristics of simple structure and convenient operation, but it can only effectively measure the antenna pattern in the distance direction and cannot realize full coverage; the natural distribution target method is limited by geographical environment, has a narrow application area, and is subject to the satellite revisit period, so the timeliness of measurement is poor, and it is difficult to meet the rapid measurement demand in emergency scenarios; the ground receiver method, as one of the current mainstream methods, has a complex structure design and needs to integrate a large number of high-precision components, resulting in high engineering implementation cost, which is not conducive to the large-scale popularization and application of the technology.

[0005] In summary, the existing antenna pattern measurement technology cannot balance the measurement accuracy, cost control and scene applicability, and a low-cost, high-precision and highly adaptable technical solution is needed to solve the current industry pain points. SUMMARY

[0006] The purpose of the application is to provide an antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver, to solve the problems of complex structure, high cost of traditional ground receivers, poor applicability and insufficient timeliness of existing antenna pattern measurement methods, and to ensure accurate measurement of the antenna pattern and meet the measurement needs of various SAR systems.

[0007] To achieve the above object, the application provides an antenna pattern measurement method based on segmented gain variable threshold single-bit receiver, and the specific steps are as follows. Step S1, different signal amplitude to threshold ratio STR is set, the signal is single-bit sampled, the sampling result is subjected to fast Fourier transform (FFT) and the quantized signal power is calculated; Step S2, the quantized signal power-STR relationship curve is drawn, the monotonic relationship between the quantized signal power and STR is analyzed, and the quantitative model between the quantized signal power and STR is established; Step S3, based on the energy conservation principle, the stability of the quantized signal power under undersampling and normal sampling is determined, and the radar antenna pattern reconstruction strategy applied to the ratio of different sampling rates and synthetic aperture radar (SAR) signal bandwidth is constructed; Step S4, according to the measurement bandwidth and the theoretical antenna pattern gain, the maximum and minimum amplitudes of the received signal are determined, the amplitudes are segmented according to the interval of STR when the quantized signal power changes monotonously with STR, and the fixed threshold of each segment is calculated; Step S5, the single-bit sampled signal is subjected to spectrum analysis, the single-frequency harmonic component is removed, and the quantized signal power is accurately calculated; Step S6, according to the quantitative model in step S2 and the quantized signal power in step S5, the STR is calculated, and the mean value of the original amplitude of the received signal is determined according to the segmented threshold in step S4, so that the actual received signal power is obtained; Step S7, the single receiver data and the multiple receiver data are processed respectively to obtain the azimuth antenna pattern sampling value and the range antenna pattern sampling value; Step S8, according to the radar equation, the azimuth antenna gain and the elevation antenna gain are calculated; Step S9, according to the calculated azimuth antenna gain and elevation antenna gain, the azimuth antenna pattern is reconstructed by linear interpolation, and the range antenna pattern is reconstructed by cubic polynomial fitting.

[0008] Preferably, in step S2, the monotonic relationship between the quantized signal power and STR is analyzed, the quantitative relationship between the quantized signal power and STR is determined by segmentation, and segmented linear fitting is performed, and the formula is as follows: ; Wherein, is the quantized signal power, and are the first-order coefficient and constant coefficient of the linear function of the first segment, respectively.

[0009] Preferably, in step S3, the antenna pattern reconstruction strategy is as follows: when ​When it is less than 1, it is in undersampling condition, and the spectrum of the signal will be aliased. According to the law of conservation of energy, the receiver sampling rate The corresponding frequency range ( ), the obtained quantized signal power remains unchanged, and the actual amplitude of the received signal is restored according to the quantitative model in step S2; when When it is greater than or equal to 1, the signal spectrum has no aliasing phenomenon and the quantized signal power is calculated normally; that is, regardless of the SAR signal bandwidth Regardless of size, the receiver only needs to use a fixed sampling rate , it is possible to recover the actual amplitude information of the received signal and reconstruct the radar antenna pattern.

[0010] Preferably, in step S4, the amplitude of the received signal is determined by the elevation antenna pattern gain and azimuth-dimensional antenna pattern gain Jointly decide, among others, is the angle between the SAR's closest slant range to the survey swath and the SAR's slant range to the receiver, is the instantaneous slant angle in azimuth; the maximum amplitude of the received signal The minimum amplitude of the received signal is obtained when the receiver is located at the center of the survey swath. Obtained when the receiver is simultaneously at the edge of the azimuth beam and the edge of the swath, where is the slant distance from the SAR to the center of the swath, and are the shortest and longest slant ranges from SAR to the survey swath, respectively.

[0011] Preferably, the amplitude of the received signal is segmented according to the interval of STR when the quantized signal power changes monotonically with STR, and the steps are as follows: Step S41: Calculate the threshold of the first segment of the received signal amplitude using the following formula: ; in, is the threshold of the first segment of the received signal amplitude, is the maximum value of STR in the monotonically changing interval; Step S42: Calculate the minimum amplitude of the first segment using the following formula: ; in, is the minimum amplitude of the first segment of the received signal amplitude, is the minimum value of the monotonically changing interval STR; Step S43: The minimum amplitude of the first segment of the received signal amplitude is As the maximum amplitude of the second segment of the received signal amplitude , the threshold value of the second segment of the received signal amplitude is calculated ; Step S44, repeating steps S41-S43, the threshold value and the minimum amplitude of each subsequent segment are calculated in turn until the last segment of the received signal amplitude is calculated The minimum amplitude is less than or equal to the minimum amplitude of the received signal .

[0012] Preferably, in step S6, the STR is calculated according to the piecewise linear fitting relationship, and the formula is as follows: ; Wherein, is the quantized signal power under the instantaneous squint angle , , is the number of sampling points in the azimuth direction, is the signal threshold ratio at the th azimuth point; The formula for calculating the actual received signal power is as follows: ; ; Wherein, is the actual received signal power under the instantaneous squint angle , is the mean value of the original amplitude of the received signal under the instantaneous squint angle , is the corresponding threshold value of the instantaneous squint angle .

[0013] Preferably, in step S8, the radar equation is calculated as follows: ; Wherein, and are the received signal power and the transmitted signal power respectively, is the wavelength, is the slant range between the SAR and the receiver, is the azimuth antenna gain, is the elevation antenna gain; The formula for calculating the azimuth antenna gain is as follows: ; Wherein, is the azimuth antenna gain under the instantaneous squint angle ; is the elevation antenna gain under the included angle , and the formula is as follows: ; wherein, is the received signal actual power at zero Doppler moment, is the included angle between the nearest slant range of SAR to the mapping band and the slant range of SAR to the first receiver, is the first receiver, is the first receiver, is the instantaneous slant angle of SAR and receiver at zero Doppler moment.

[0014] Therefore, the application proposes an antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver, which has the following beneficial effects: (1) The application adopts a single-frequency threshold single-bit quantization strategy, which reduces the data storage amount, avoids the complex high-precision component design of traditional ground receivers, greatly simplifies the structure, reduces the hardware cost and operating power consumption, solves the pain point of high engineering implementation cost of traditional ground receivers, and is more conducive to large-scale popularization and application.

[0015] (2) The application optimizes the stability of the quantized signal power-STR relationship curve through Monte Carlo experiments, and establishes a quantitative model in the STR monotonic interval; at the same time, in view of the problem of large dynamic range of signal amplitude, a segmented fixed threshold strategy is adopted to ensure that the STR of each signal is in the monotonic interval, effectively restores the actual amplitude of the signal, guarantees the antenna pattern measurement accuracy, and meets the accuracy requirements of SAR radiation calibration.

[0016] (3) The application proposes an adaptive scheme of different sampling rate and SAR signal bandwidth ratio based on the principle of energy conservation, and the receiver only needs a fixed sampling rate to meet the antenna pattern measurement requirements of different bandwidth SAR systems, without the need to adjust the sampling rate according to the SAR type, breaking through the strict limitation of the traditional method on the sampling rate, and having stronger adaptability.

[0017] The technical solutions of the application will be further described in detail below with the aid of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a flowchart of an antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver of the application; Figure 2 is a schematic diagram of the geometric scene of a synthetic aperture radar (SAR) in the embodiment of the application. DETAILED DESCRIPTION

[0019] To make the technical solutions, advantages, and objectives of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The described embodiments are part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0021] Example like Figure 1 As shown, the present invention provides an antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver, and the specific steps are as follows: S1. Set different signal amplitude to threshold ratios (STR), perform single-bit sampling on the signal, perform fast Fourier transform (FFT) on the sampling results, and calculate the quantized signal power. Finally, draw a quantized signal power-STR relationship curve, analyze the monotonic relationship between the quantized signal power and STR, and establish a quantitative model between the quantized signal power and STR. During the single-frequency threshold single-bit sampling process of the signal, intermodulation occurs between the signal harmonics and the single-frequency threshold harmonics. The amplitude of the intermodulation component between the first-order harmonic of the signal and the threshold exhibits a monotonic characteristic with the change of STR within a large STR range. This relationship can be used to recover the amplitude information of the signal, as follows: By setting different STRs, the signal is sampled single-bit, the sampling results are subjected to a Fast Fourier Transform (FFT), and the quantized signal power is calculated. Finally, a quantized signal power-STR relationship curve is plotted. Given that the initial phase of the single-frequency threshold is random, resulting in unstable results, a Monte Carlo experiment is performed to obtain a more stable curve relationship. For example, when the STR is within the range of -20dB to -5dB, the quantitative relationship between the quantized signal power and the STR is determined segment by segment, and a piecewise linear fit is performed. The formula is as follows: ; in, To quantify the signal power, and Respectively The coefficients of the linear term and the constant term of a piecewise linear function.

[0022] S2. Based on the principle of energy conservation, the stability of the quantized signal power under undersampling and normal sampling conditions is determined, and an antenna pattern reconstruction strategy applicable to different ratios of sampling rate to synthetic aperture radar (SAR) signal bandwidth is constructed. The specific strategy is as follows: Receiver sampling rate is fixed, however there are many types of SAR and their signal bandwidth In order to meet the measurement requirements of various SAR antenna patterns, a system suitable for different ratios of sampling rate to signal bandwidth ( ) antenna pattern reconstruction strategy. When it is less than 1, it is in undersampling condition, and the spectrum of the signal will be aliased. According to the law of conservation of energy, the receiver sampling rate The corresponding frequency range ( ), the estimated quantized signal power remains basically unchanged, so the actual amplitude of the received signal can still be restored according to the quantitative model in step 1; when When σ is greater than or equal to 1, the signal spectrum is free of aliasing, and the quantized signal power can be directly estimated normally. This shows that regardless of the SAR signal bandwidth, the receiver only needs to use a fixed sampling rate to recover the actual amplitude information of the received signal and thus reconstruct the radar antenna pattern.

[0023] S3. Determine the maximum and minimum amplitudes of the received signal based on the swath width and the theoretical antenna pattern gain, segment the amplitude based on the STR interval when the quantized signal power changes monotonically with the STR, and calculate the fixed threshold for each segment; like Figure 2 As shown, the amplitude of the received signal is determined by the antenna pattern gain in the elevation dimension. and azimuth-dimensional antenna pattern gain Jointly decide, among others, is the angle between the SAR's closest slant range to the survey swath and the SAR's slant range to the receiver, is the instantaneous slant angle in azimuth; the maximum amplitude of the received signal The minimum amplitude of the received signal is obtained when the receiver is located at the center of the survey swath. Obtained when the receiver is simultaneously at the edge of the azimuth beam and the edge of the swath, where is the slant distance from the SAR to the center of the swath, and are the shortest and longest slant ranges from SAR to the survey swath, respectively.

[0024] Due to the different placement of the receiver and the movement of the SAR platform, the amplitude of the received signal has a large dynamic range. In order to control the STR within a monotonic range, it is necessary to segment the amplitude of the received signal and set a different threshold for each segment. The specific steps are as follows: S31. Calculate the threshold of the first segment of the received signal amplitude using the following formula: ; in, is the threshold of the first segment of the received signal amplitude, is the maximum value of STR in the monotonically changing interval; S32. Calculate the minimum amplitude of the first segment using the following formula: ; in, is the minimum amplitude of the first segment of the received signal amplitude, is the minimum value of the monotonically changing interval STR; S33, the minimum amplitude of the first segment of the received signal amplitude As the maximum amplitude of the second segment of the received signal amplitude , calculate the threshold of the second segment of the received signal amplitude ; S34, repeat steps S31-S33, and calculate the threshold and minimum amplitude of each subsequent segment in sequence until the minimum amplitude calculated in the last segment of the received signal amplitude is less than or equal to the minimum amplitude of the received signal .

[0025] S4. After the signal is sampled using a single-bit single-frequency threshold, harmonic components of the single-frequency threshold are introduced into the signal spectrum. The presence of these harmonic components can lead to unstable estimation of the quantized signal power. To more accurately estimate the quantized signal power, spectrum analysis is performed on the signal after single-bit sampling to remove the single-frequency harmonic components. S5. Calculate STR based on the quantitative model in step S1 and the quantized signal power in step S4, determine the original amplitude of the received signal based on the segmented threshold in step S3, and obtain the actual received signal power; When the SAR's azimuth beam coverage area completely sweeps over a receiver, the receiver records different instantaneous slant angles. The received signal is , is the number of sampling points in the azimuth direction. Since the receiver uses single-frequency threshold single-bit sampling, the recorded data is a quantized signal. It is necessary to restore the actual amplitude of the received signal to calculate the actual received power. When the instantaneous slant angle between the SAR and the receiver is When , the original amplitude mean of the signal received by the receiver is , there is a monotonic relationship between the known quantized signal power and STR in step S1, combined with the quantized signal power estimated in step S4 , STR is calculated based on the piecewise linear fitting relationship, and the formula is as follows: ; in, Instantaneous squint angle The quantized signal power under For the Signal threshold ratio at each azimuth point; Then determine the current instantaneous squint angle according to the segmentation of step S3 The corresponding threshold , calculate the mean of the original amplitude of the received signal, the formula is as follows: ; in, Instantaneous squint angle The mean of the original amplitude of the received signal under Instantaneous squint angle The corresponding threshold.

[0026] The actual received signal power is obtained from the average of the original amplitudes of the received signal. The formula is as follows: ; in, Instantaneous squint angle The actual received signal power under S6. Processing data from a single receiver separately and comprehensively processing data from multiple receivers to obtain azimuth antenna pattern sampling values ​​and range antenna pattern sampling values, and reconstructing azimuth and range antenna patterns; At the zero Doppler moment, each receiver records the received signal at that moment. According to the method in step S5, the actual power of the received signal of each receiver at the zero Doppler moment is calculated. , Corresponding to different angles The actual power of the received signal under The SAR is the closest slant range to the survey swath and the SAR is the closest slant range to the first The angle between the slant ranges of the receivers (after zero Doppler calibration), For the A receiver.

[0027] S7. Calculate the azimuth antenna gain and the elevation antenna gain according to the radar equation; The radar equation calculation formula is as follows: ; in, and are the received signal power and the transmitted signal power, respectively. is the wavelength, is the slant distance between the SAR and the receiver, is the antenna gain in azimuth dimension, is the antenna gain in the elevation dimension; Azimuth antenna gain The calculation formula is as follows: ; wherein, is the azimuth antenna gain under the instantaneous squint angle ; is the range antenna gain under the included angle , and the calculation formula is as follows: ; wherein, is the instantaneous squint angle of SAR and the receiver at the zero Doppler moment.

[0028] S8, according to the calculated azimuth antenna gain and elevation antenna gain, the azimuth antenna pattern is reconstructed by linear interpolation, and the range antenna pattern is reconstructed by cubic polynomial fitting.

[0029] It is worth noting that the contents not elaborated in the present application are all prior art and are well known to those skilled in the art.

[0030] Therefore, the present application provides an antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver, which reduces data storage, simplifies the receiver structure, reduces hardware cost and power consumption through a single-frequency threshold single-bit quantization strategy, solves the problem of high cost of traditional ground receivers, and at the same time, combines the segmented fixed threshold strategy to recover the signal amplitude, guarantees the measurement accuracy to meet the SAR radiation calibration requirements, and also based on the principle of energy conservation, makes the receiver adapt to different bandwidth SARs at a fixed sampling rate, breaks through the limitation of traditional sampling rate, and has stronger adaptability.

[0031] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements also cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for measuring antenna pattern based on a segmented gain variable threshold single-bit receiver, characterized in that: The specific steps are as follows: Step S1, setting different ratios of signal amplitude to threshold STR, performing single-bit sampling on the signal, performing fast Fourier transform FFT on the sampling result and calculating the quantized signal power; Step S2, drawing a quantization signal power-STR relationship curve, analyzing the monotonic relationship between the quantization signal power and STR, and establishing a quantitative model between the quantization signal power and STR; Step S3: Based on the principle of energy conservation, the stability of the quantized signal power under undersampling and normal sampling conditions is determined, and a radar antenna pattern reconstruction strategy applicable to all ratios of sampling rate to synthetic aperture radar (SAR) signal bandwidth is constructed; Step S4: Determine the maximum and minimum amplitudes of the received signal based on the swath width and the theoretical antenna pattern gain, segment the amplitude based on the STR interval when the quantized signal power changes monotonically with the STR, and calculate the fixed threshold for each segment; Step S5: performing spectrum analysis on the signal after single-bit sampling, removing single-frequency harmonic components, and accurately calculating the quantized signal power; Step S6: Calculate STR based on the quantitative model in step S2 and the quantized signal power in step S5, and determine the mean of the original amplitude of the received signal based on the segmented threshold in step S4 to obtain the actual received signal power; Step S7: processing the data of a single receiver separately and comprehensively processing the data of multiple receivers to obtain the azimuth antenna pattern sampling value and the range antenna pattern sampling value; Step S8: Calculate the azimuth antenna gain and the elevation antenna gain according to the radar equation; Step S9: Reconstruct the azimuth antenna pattern using linear interpolation based on the calculated azimuth antenna gain and elevation antenna gain, and reconstruct the range antenna pattern using cubic polynomial fitting.

2. The antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver according to claim 1, characterized in that: In step S2, the monotonic relationship between the quantized signal power and STR is analyzed, the quantitative relationship between the quantized signal power and STR is determined segment by segment, and a segmented linear fit is performed. The formula is as follows: ； in, To quantify the signal power, and Respectively The coefficients of the linear term and the constant term of a piecewise linear function.

3. The antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver according to claim 1, characterized in that: In step S3, the antenna pattern reconstruction strategy is specifically as follows: When it is less than 1, it is in undersampling condition, and the spectrum of the signal will be aliased. According to the law of conservation of energy, the receiver sampling rate The corresponding frequency range ( ), the obtained quantized signal power remains unchanged, and the actual amplitude of the received signal is restored according to the quantitative model in step S2; when When it is greater than or equal to 1, the signal spectrum has no aliasing phenomenon and the quantized signal power is calculated normally; that is, regardless of the SAR signal bandwidth Regardless of size, the receiver only needs to use a fixed sampling rate , it is possible to recover the actual amplitude information of the received signal and reconstruct the radar antenna pattern.

4. The antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver according to claim 2, characterized in that: In step S4, the amplitude of the received signal is determined by the elevation antenna pattern gain and azimuth-dimensional antenna pattern gain Jointly decide, among others, is the angle between the SAR's closest slant range to the survey swath and the SAR's slant range to the receiver, is the instantaneous slant angle in azimuth; the maximum amplitude of the received signal The minimum amplitude of the received signal is obtained when the receiver is located at the center of the survey swath. Obtained when the receiver is simultaneously at the edge of the azimuth beam and the edge of the swath, where is the slant distance from the SAR to the center of the swath, and are the shortest and longest slant ranges from SAR to the survey swath, respectively.

5. The antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver according to claim 4, characterized in that: The amplitude of the received signal is segmented according to the interval of STR when the quantized signal power changes monotonically with STR. The steps are as follows: Step S41: Calculate the threshold of the first segment of the received signal amplitude using the following formula: ； in, is the threshold of the first segment of the received signal amplitude, is the maximum value of STR in the monotonically changing interval; Step S42: Calculate the minimum amplitude of the first segment using the following formula: ； in, is the minimum amplitude of the first segment of the received signal amplitude, is the minimum value of the monotonically changing interval STR; Step S43: The minimum amplitude of the first segment of the received signal amplitude is As the maximum amplitude of the second segment of the received signal amplitude , calculate the threshold of the second segment of the received signal amplitude ; Step S44: Repeat steps S41 to S43 to calculate the threshold and minimum amplitude of each subsequent segment in sequence until the minimum amplitude calculated for the last segment of the received signal amplitude is less than or equal to the minimum amplitude of the received signal. .

6. The antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver according to claim 2, characterized in that: In step S6, STR is calculated based on the piecewise linear fitting relationship, and the formula is as follows: ； in, Instantaneous squint angle The quantized signal power under , is the number of sampling points in the azimuth direction, For the Signal threshold ratio at each azimuth point; The calculation formula for the actual received signal power is as follows: ； ； in, Instantaneous squint angle The actual received signal power under Instantaneous squint angle The mean of the original amplitude of the received signal under Instantaneous squint angle The corresponding threshold.

7. The antenna pattern measurement method based on a segmented gain variable threshold single-bit receiver according to claim 6, characterized in that: In step S8, the radar equation calculation formula is as follows: ； in, and are the received signal power and the transmitted signal power, respectively. is the wavelength, is the slant distance between the SAR and the receiver, is the antenna gain in azimuth dimension, is the antenna gain in the elevation dimension; Azimuth antenna gain The calculation formula is as follows: ； in, Instantaneous squint angle Antenna gain in azimuth dimension under ; Angle The antenna gain in the elevation dimension is calculated as follows: ； in, is the actual power of the received signal at zero Doppler moment, The minimum slant range from SAR to the survey swath and the minimum slant range from SAR to the first The angle between the slant ranges of the receivers, For the A receiver, is the instantaneous slant angle between the SAR and the receiver at zero Doppler moment.

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