Satellite-borne multi-channel SAR channel amplitude and phase consistency monitoring method

Abstract

The application provides a kind of on-board multi-channel SAR channel amplitude-phase consistency monitoring method, comprising: selecting SAR different working mode bandwidth, according to the design of whole array receiving calibration test instruction package, sequentially obtaining the linear frequency modulation signal of each receiving channel of antenna whole array, the original amplitude and phase value of each receiving channel are obtained by pulse compression processing;Establish amplitude-phase characteristic basic data matrix, catalog into database;Phase basic data in amplitude-phase characteristic basic data matrix is unwrapped and unwrapped between channels;The amplitude-phase data of each channel after phase unwrapping is normalized by difference with reference channel, statistical characteristic analysis is carried out, and cataloged into database;Establish amplitude-phase consistency monitoring database;The analysis data of each channel amplitude-phase of database export is analyzed, and the statistical analysis of the analysis data is carried out.The application focuses on solving the problem of on-board azimuth multi-channel SAR amplitude-phase consistency monitoring in time dimension.

Description

Technical Field

[0001] This invention relates to the field of space remote sensing instruments, and more specifically, to a method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels. Background Technology

[0002] With the development of spaceborne SAR technology, high resolution and wide mapping bandwidth have become the future development trends of spaceborne SAR. Azimuth resolution and range mapping bandwidth are two mutually restrictive technical indicators in spaceborne SAR. Expanding the mapping bandwidth of a spaceborne SAR system requires sacrificing azimuth resolution, and vice versa. To alleviate the contradiction between high azimuth resolution and wide range coverage, various new technologies and ideas have been proposed both domestically and internationally. Among them, the most classic and feasible is the use of azimuth multi-channel technology. Azimuth multi-channel technology utilizes the "Displaced Phase Centre Antenna (DPCA) principle," which can significantly reduce the pulse repetition frequency of the SAR system, thereby improving the ambiguity index of the SAR system and achieving the expansion of mapping bandwidth under high-resolution conditions.

[0003] However, a prominent problem with multi-channel systems is false targets. Amplitude and phase inconsistencies between channels can introduce false targets into the image, affecting image quality and, in severe cases, even causing target misjudgment. Suppressing false targets requires strict control of amplitude and phase inconsistency errors between channels, and monitoring the amplitude and phase consistency of the receiving channels during the engineering development process to verify the effectiveness of the design and control, and to provide a reference for on-orbit compensation.

[0004] After the spaceborne multi-channel SAR is integrated into the satellite, it requires full-satellite-level mechanical, electrical, and thermal testing. This testing is time-consuming and complex, and the numerous microwave components in the SAR transceiver system make it impossible to monitor the performance of each component in real time. Failures in any of these components can cause errors in the system's receiving channels, impacting the overall performance of the SAR system. To ensure the performance of the SAR system during testing, channel amplitude and phase consistency monitoring up to the transmission time dimension is necessary to ensure the spaceborne SAR operates normally in orbit.

[0005] Traditional methods for testing channel consistency mainly involve sequentially acquiring the amplitude and phase information of each component of the SAR receiving system, then using system simulation to obtain the amplitude and phase of the entire system's multiple receiving channels, thereby estimating amplitude and phase consistency. To verify the on-orbit amplitude and phase consistency of spaceborne SAR, tests must be conducted in an anechoic chamber and under thermal vacuum conditions. This method is difficult and time-consuming, making it impossible to quickly and effectively achieve inter-channel amplitude and phase consistency observation.

[0006] Patent document CN107390192 discloses a method for rapid amplitude and phase consistency measurement of phased array weather radar. This method directly utilizes an external signal generator and a parabolic antenna to transmit radio frequency signals to the radar under test. The amplitude and phase are then acquired through multiple receiving channels, and the phase difference between channels is used for correction. This method requires an external signal generator and a reflector antenna, and the transmitted radio frequency signal must meet plane wave conditions to reach the phased array under test. Spaceborne SAR antennas are typically large (on the order of 10 meters), requiring a large reflector antenna aperture, which is difficult to manufacture and makes amplitude and phase consistency testing challenging. This invention, however, does not require external equipment and utilizes in-system calibration to achieve amplitude and phase consistency testing, making the experiment much easier.

[0007] Patent document CN108279404 discloses a dual-channel SAR phase error correction method based on spatial spectrum estimation, which uses the echo signal received by the dual-channel SAR system from the scene target to obtain the phase error between channels. This method requires the acquisition of real-time scene echo signals. However, during ground testing of spaceborne SAR, it is impossible to obtain the real echo signal between the satellite and the ground, making it impossible to use this method for monitoring and error correction of the amplitude and phase consistency between channels.

[0008] Patent document CN112698137 discloses a test method and system for the consistency of amplitude and phase changes with temperature. Through a scientific experimental scheme and test data algorithm logic, it tests and screens the amplitude and phase consistency index of cables at each frequency and temperature point. This method can monitor the amplitude and phase consistency of cables. However, SAR system amplitude and phase consistency measurement involves not only TR components, power dividers, and cables, but also a large number of devices. Using this method to achieve amplitude and phase consistency testing results in a long testing cycle and is difficult, making it unsuitable for monitoring the entire satellite across all temperatures and cycles.

[0009] Patent document CN110018455 discloses a calibration and measurement method for amplitude and phase consistency error between satellite-borne SAR imaging receiving channels, which eliminates the need to measure the amplitude and phase consistency error between imaging receiving channels under microwave anechoic chamber pre-scanning conditions. This method enables amplitude and phase consistency monitoring during the SAR whole-satellite testing phase, but does not establish an amplitude and phase statistical characteristic database.

[0010] Patent document CN111965602 discloses a method and system for monitoring the amplitude and phase consistency of a phased array radar, which maintains the consistency of the phased array antenna radar by pre-setting elements and probes. This method can maintain and adjust the amplitude and phase consistency; however, in the face of the complex force and heat environment in the whole-satellite testing of SAR satellites, the installation of external elements and probes is complex and difficult.

[0011] Based on the search of the aforementioned patents and the methods combined with existing technologies, there is an urgent need to research and establish a method for monitoring amplitude and phase consistency over long periods of time. This method should monitor the amplitude and phase consistency of the receiving channel under simulated satellite orbit insertion and on-orbit environmental conditions, establish an amplitude and phase consistency database, and conduct long-term amplitude and phase consistency monitoring. This is crucial for achieving normal imaging of spaceborne SAR. The key technologies to be solved and the established technology platform can support the performance testing of multi-channel SAR satellites. Summary of the Invention

[0012] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels.

[0013] A method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to the present invention includes the following steps:

[0014] Step 1: Select the working bandwidth of different SAR working modes, design the full array receiving calibration test command packet according to the imaging requirements, and sequentially obtain the linear frequency modulation signal of each receiving channel of the full array antenna. After pulse compression processing, obtain the original amplitude and phase values ​​of each receiving channel.

[0015] Step 2: Perform an amplitude and phase consistency test on the receiving channels, generating M×N amplitude and phase data respectively, and establish an M×N amplitude and phase characteristic basic data matrix, which is then cataloged and stored in the database; where: N is the number of receiving channels, and M is the number of full-array normal receiving calibration pulses in this test;

[0016] Step 3: Perform intra-channel phase unwrapping and inter-channel phase unwrapping on the phase fundamental data in the amplitude-phase characteristic fundamental data matrix;

[0017] Step 4: Normalize the amplitude and phase data of each channel after phase unwrapping by subtracting from the reference channel to obtain the amplitude and phase data between channels, perform statistical characteristic analysis on it, and catalog the amplitude and phase statistical analysis data after statistical analysis and the amplitude and phase data from Step 2 into the database.

[0018] Step 5: Repeat steps 1 to 4 to obtain multiple amplitude-phase consistency test data and establish an amplitude-phase consistency monitoring database;

[0019] Step Six: After a certain test phase is completed or all ground tests are completed, export the analysis data of the amplitude phase of each channel in each test from the amplitude phase consistency monitoring database, and perform statistical analysis on the analysis data of each test.

[0020] Preferably, in step one, the full-array receiving calibration is set to non-delayed receiving calibration, and the calibration is performed during the imaging process, or continuous test calibration is performed without imaging.

[0021] Preferably, in step three, the in-channel phase unwrapping method involves sequentially selecting each column of the in-channel phase to obtain the maximum and minimum values ​​of the in-channel phase.

[0022] Preferably, when the difference between the maximum and minimum values ​​in a channel is greater than 180, then 360 is added to all phases in that channel that are less than 0.

[0023] Preferably, in step three, the inter-channel phase unwrapping method involves selecting a certain channel phase as a reference channel and calculating the maximum and minimum values ​​of the phases of other channels relative to the reference channel.

[0024] Preferably, when the difference between the maximum and minimum phase values ​​between channels is greater than 180, then all channels with phase values ​​less than 0 are incremented by 360.

[0025] Preferably, in step four, the statistical characteristic analysis involves plotting the variation curves of the amplitude and phase data of each channel after difference normalization, as well as the variation curves of each channel after "zero mean normalization", to graphically display the results of this amplitude and phase consistency test.

[0026] Preferably, in step six, statistical analysis is performed on the data from each analysis, and the maximum value of the peak-to-peak value of each channel amplitude phase in each test is taken to obtain the monitoring results of amplitude phase consistency between channels in each test.

[0027] Preferably, in step six, statistical analysis is performed on the data from each analysis. By taking the maximum value of the maximum value and the minimum value of the minimum value of each channel amplitude phase in each test, the extreme value envelope of the amplitude phase change of each channel in each test is obtained.

[0028] Preferably, in step six, statistical analysis is performed on the data from each analysis, and based on the mean amplitude of each channel in each test, an amplitude-phase consistency curve for each channel in each test is plotted to obtain an intuitive graphical result of the amplitude-phase consistency of each test.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention establishes a method for monitoring amplitude and phase consistency over a long period of time. Under simulated satellite orbit insertion and on-orbit environmental conditions, the method monitors the amplitude and phase consistency of the receiving channel, establishes an amplitude and phase consistency database, and conducts amplitude and phase consistency monitoring over a long period of time.

[0031] 2. This invention solves the problem of monitoring the amplitude and phase consistency of spaceborne azimuth multi-channel SAR in the time dimension. At the same time, in order to improve measurement accuracy and ease of implementation, it ensures the channel performance indicators of spaceborne SAR.

[0032] 3. From SAR integration testing to satellite launch, this invention can periodically test channel amplitude and phase data at each testing stage, thereby monitoring the amplitude and phase changes of the channel over time at different stages, providing a reference for decision-making on channel amplitude and phase error compensation for on-orbit SAR. Attached Figure Description

[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0034] Figure 1 This is a flowchart of the satellite-borne multi-channel SAR channel amplitude and phase consistency monitoring process of the present invention.

[0035] Figure 2 This is a schematic diagram illustrating the statistical characteristics of amplitude data in each channel of a single test in this invention.

[0036] Figure 3 This is a schematic diagram illustrating the statistical characteristics analysis of phase data of each channel in a single test of the present invention.

[0037] Figure 4 This is a graph showing the amplitude consistency analysis results of a single test data in this invention.

[0038] Figure 5 This is a graph showing the phase consistency analysis results of a single test data in this invention.

[0039] Figure 6 This is a graph showing the consistency monitoring results of the average amplitude of each channel in all tests of this invention.

[0040] Figure 7 This is a graph showing the monitoring results of the consistency of the average phase values ​​of each channel in each test of this invention. Detailed Implementation

[0041] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0042] like Figures 1 to 7As shown, a method for monitoring the amplitude and phase consistency of a satellite-borne multi-channel SAR channel according to the present invention includes the following steps: Step 1: Selecting the working bandwidth of different SAR working modes, designing a full-array receiver calibration test command packet according to imaging needs, sequentially acquiring the linear frequency modulated signals of each receiver channel of the full array antenna, and obtaining the original amplitude and phase values ​​of each receiver channel through pulse compression processing; Step 2: Performing a receiver channel amplitude and phase consistency test, generating M×N amplitude data and phase data respectively, establishing an M×N amplitude and phase characteristic basic data matrix, and cataloging it into a database; where: N is the number of receiver channels, and M is the number of full-array normal receiver calibration pulses in this test; Step 3: [The text abruptly ends here, likely due to an incomplete sentence or a missing section.] Step 1: Unwrap the phase data in the basic data matrix within each channel and between channels; Step 2: Normalize the phase data of each channel after phase unwrapping by subtracting from the reference channel to obtain the phase data between channels, and perform statistical characteristic analysis on it. Then, catalog the statistically analyzed phase data and the phase data from Step 2 into the database; Step 3: Repeat Steps 1 to 4 to obtain multiple phase consistency test data and establish a phase consistency monitoring database; Step 4: At the end of a certain test phase or after all ground tests are completed, export the analysis data of each channel's phase from the phase consistency monitoring database and perform statistical analysis on the analysis data.

[0043] Furthermore, in step one, the full-array receiving calibration is set to non-delayed receiving calibration, and calibration is performed during the imaging process, or continuous test calibration is performed without imaging.

[0044] In step three, the intra-channel phase unwrapping method involves sequentially selecting each column of phases within the channel and calculating the maximum and minimum values ​​of the phases within that channel. When the difference between the maximum and minimum values ​​within a channel is greater than 180, then 360 is added to all phases within that channel that are less than 0. The inter-channel phase unwrapping method involves selecting a certain channel phase as a reference channel and calculating the maximum and minimum values ​​of the phases of other channels relative to the reference channel. When the difference between the maximum and minimum values ​​of the inter-channel phases is greater than 180, then 360 is added to all channel phases corresponding to phases less than 0.

[0045] In step four, the statistical characteristic analysis involves plotting the variation curves of the amplitude and phase data of each channel after difference normalization, as well as the variation curves of each channel after "zero mean normalization", to graphically display the results of this amplitude and phase consistency test.

[0046] In step six, statistical analysis is performed on the data from each analysis. By taking the maximum value of the peak-to-peak value of each channel's amplitude phase in each test, the monitoring results of amplitude phase consistency between channels are obtained. By taking the maximum value of the maximum value and the minimum value of the amplitude phase in each channel in each test, the extreme value envelope of the amplitude phase change in each channel in each test is obtained. Based on the mean value of the amplitude phase in each channel in each test, an amplitude phase consistency curve for each channel in each test is plotted to obtain a visual graphical result of the amplitude phase consistency in each test.

[0047] In a more detailed explanation, according to the embodiments provided by the present invention, the spaceborne SAR has been integrated, the antenna array has been deployed, and imaging is possible. The operating bandwidth of different SAR operating modes is selected, the imaging wavefront and receiving channel parameters are chosen, and the data is processed into a full-array receiving calibration test command packet. This packet is sent to the SAR radar computer via a ground command transmission device. The SAR sequentially acquires the linear frequency modulated signals of each receiving channel of the full antenna array according to the test command requirements. After pulse compression processing, the original amplitude and phase values ​​of each receiving channel are obtained, and the results are displayed as shown below. Figure 2 .

[0048] Two M×N amplitude and phase characteristic basic data matrices are generated from each test result, cataloged according to the test time, and stored in the amplitude and phase consistency monitoring database.

[0049] Phase unwrapping is performed on the basic phase data of the received channels. Phase unwrapping includes two steps: the first step is intra-channel phase unwrapping, and the second step is inter-channel phase unwrapping. The intra-channel phase unwrapping method sequentially calculates the maximum and minimum values ​​of the phase within each channel. If the difference between the maximum and minimum values ​​of a channel is greater than 180, then all phases in that channel with values ​​less than 0 are incremented by 360. The inter-channel phase unwrapping method selects a specific row of data from a channel's phase, typically the first channel, and calculates the maximum and minimum values ​​of the inter-channel phase. If the difference between the maximum and minimum values ​​of the inter-channel phase is greater than 180, then all channel phases with values ​​less than 0 are incremented by 360.

[0050] The amplitude and phase data of each channel after phase unwrapping are normalized by subtracting from the reference channel (usually the first receiving channel), resulting in normalized amplitude and phase data. Statistical characteristic analysis is then performed on these data, calculating the maximum, minimum, peak-to-peak, and mean amplitude values, as well as the maximum, minimum, peak-to-peak, and mean phase values. This amplitude and phase statistical analysis data is then cataloged and stored. For the sum of the subtracted and normalized amplitude and phase data of each channel, variation curves are plotted, along with the variation curves after "zero-mean normalization" for each channel. The results of this amplitude and phase consistency test are graphically displayed, such as... Figure 3 As shown.

[0051] During ground testing, the amplitude and phase consistency results of each test are cataloged and stored in a database to establish an amplitude and phase consistency monitoring database.

[0052] At the end of a certain testing phase or after all ground tests are completed, the analysis data (including maximum, minimum, peak-to-peak and average values) of each channel of each test are exported from the database, and statistical analysis is performed on the analysis data of each test.

[0053] like Figure 4 As shown, after completing multiple ground tests, a statistical characteristic database of amplitude-phase consistency was formed. The peak-to-peak value of the amplitude phase of each channel in each test was taken as the maximum value to obtain the amplitude-phase consistency monitoring results between channels in each test. The maximum value of the maximum value and the minimum value of the amplitude phase of each channel in each test were taken as the maximum value and the minimum value to obtain the extreme value envelope of the amplitude-phase change of each channel in each test. Based on the mean value of the amplitude phase of each channel in each test, the amplitude-phase consistency curve of each channel in each test was plotted to obtain an intuitive graphical result of the amplitude-phase consistency of each test, providing a reference for the granular decision-making of amplitude-phase error compensation between channels.

[0054] In summary, this invention fills a gap in the prior art, establishes an amplitude and phase consistency monitoring database under various on-orbit simulation conditions across all ground testing time periods, ensures consistency between the design polarity and the actual polarity of remote sensing data, and provides a basis for channel error compensation decisions during SAR on-orbit operation.

[0055] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels, characterized in that, Includes the following steps: Step 1: Select the working bandwidth of different SAR working modes, design the full array receiving calibration test command packet according to the imaging requirements, and sequentially obtain the linear frequency modulation signal of each receiving channel of the full array antenna. After pulse compression processing, obtain the original amplitude and phase values ​​of each receiving channel. Step 2: Perform an amplitude and phase consistency test on the receiving channels, generating M×N amplitude and phase data respectively, and establish an M×N amplitude and phase characteristic basic data matrix, which is then cataloged and stored in the database; where: N is the number of receiving channels, and M is the number of full-array normal receiving calibration pulses in this test; Step 3: Perform intra-channel phase unwrapping and inter-channel phase unwrapping on the phase fundamental data in the amplitude-phase characteristic fundamental data matrix; Step 4: Normalize the amplitude and phase data of each channel after phase unwrapping by subtracting from the reference channel to obtain the amplitude and phase data between channels, perform statistical characteristic analysis on it, and catalog the amplitude and phase statistical analysis data after statistical analysis and the amplitude and phase data from Step 2 into the database. Step 5: Repeat steps 1 to 4 to obtain multiple amplitude-phase consistency test data and establish an amplitude-phase consistency monitoring database; Step Six: After a certain test phase is completed or all ground tests are completed, export the analysis data of the amplitude phase of each channel in each test from the amplitude phase consistency monitoring database, and perform statistical analysis on the analysis data of each test.

2. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 1, characterized in that, In step one, the full-array receiver calibration is set to non-delayed receiver calibration, and calibration is performed during imaging, or continuous test calibration is performed without imaging.

3. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 1, characterized in that, In step three, the in-channel phase unwrapping method involves sequentially selecting each column of the in-channel phase to obtain the maximum and minimum values ​​of the in-channel phase.

4. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 3, characterized in that, When the difference between the maximum and minimum values ​​in a channel is greater than 180, add 360 to all phases in that channel that are less than 0.

5. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 1, characterized in that, In step three, the inter-channel phase unwrapping method involves selecting a certain channel phase as the reference channel and calculating the maximum and minimum values ​​of the phases of other channels relative to the reference channel.

6. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 5, characterized in that, When the difference between the maximum and minimum phase values ​​between channels is greater than 180, then all channels with phase values ​​less than 0 are incremented by 360.

7. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 1, characterized in that, In step four, the statistical characteristic analysis involves plotting the variation curves of the amplitude and phase data of each channel after difference normalization, as well as the variation curves of each channel after "zero mean normalization", to graphically display the results of this amplitude and phase consistency test.

8. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 1, characterized in that, In step six, statistical analysis is performed on the data from each analysis. By taking the maximum value of the peak value of each channel amplitude phase in each test, the monitoring results of amplitude phase consistency between channels in each test are obtained.

9. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 1, characterized in that, In step six, statistical analysis is performed on the data from each analysis. By taking the maximum value of the amplitude and the minimum value of each channel in each test, the extreme value envelope of the amplitude and phase changes of each channel in each test is obtained.

10. The method for monitoring the amplitude and phase consistency of spaceborne multi-channel SAR channels according to claim 1, characterized in that, In step six, statistical analysis is performed on the data from each analysis. Based on the mean amplitude of each channel in each test, amplitude consistency curves for each channel in each test are plotted to obtain intuitive graphical results of amplitude consistency in each test.

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