Phase synchronization compensation method and device for distributed satellite synthetic aperture radar

Abstract

The present invention provides a distributed satellite synthetic aperture radar phase synchronization compensation method and device, relating to the technical field of distributed satellite SAR. The method comprises: in a distributed satellite SAR system, extracting synchronization data of the primary and auxiliary satellites from the echo data of the primary and auxiliary satellites, respectively, wherein the synchronization data includes the first synchronization phase data, the interpolation synchronization phase data, and the tail synchronization phase data; unwrapping the synchronization data of the primary and auxiliary satellites; calculating the gradient information of the unwrapped synchronization data, and judging whether the interpolation synchronization phase data is damaged based on the gradient information; if it is determined that the interpolation synchronization phase data is not damaged, unwrapping the unwrapped synchronization data; performing pulse compression on the unwrapped synchronization data to extract the peak phase; generating a compensation phase based on the difference between the peak phases of the primary and auxiliary satellites, and interpolating the compensation phase; and using the interpolated compensation phase to perform point-by-point compensation on the echo data of the auxiliary satellite.

Description

Technical Field

[0001] The present invention relates to the technical field of distributed satellite SAR, and in particular to a distributed satellite synthetic aperture radar phase synchronization compensation method and device. Background Art

[0002] Distributed satellite synthetic aperture radar (SAR) systems typically consist of two or more satellites, one of which (the primary satellite) transmits radar signals and receives echoes, while the other satellites (the secondary satellites) passively receive echoes. However, the distributed design of the primary and secondary satellites introduces phase synchronization issues, primarily due to two reasons: First, the primary and secondary satellites use independent crystal oscillators as frequency sources, resulting in frequency inconsistencies and, consequently, phase deviations; second, the transmit and receive phase noise of the primary and secondary satellites are decorrelated and cannot cancel each other out as in traditional single-satellite systems. Therefore, to ensure phase synchronization, distributed or dual-satellite formation SAR systems must employ appropriate phase compensation methods.

[0003] Currently, the pulse alternating transmission method is considered one of the more reliable engineering solutions. This method was proposed by Younis of DLR and successfully applied to the TerraSAR-X / TanDEM-X system. The pulse alternating transmission method can significantly improve synchronization stability by establishing a dedicated synchronization link between the primary and secondary satellites and using bidirectional transmission of synchronization pulses. However, since the radar reference frequency sources of the primary and secondary satellites each use a high-stability crystal oscillator, and the frequency accuracy of the crystal oscillator is generally 10 -6 The carrier frequency difference of the X-band radars of the primary and secondary satellites may be close to 20 kHz, which is much larger than the repetition frequency of the synchronization pulse, making the error extraction of phase synchronization more complicated.

[0004] To further improve the accuracy, existing technologies have adopted GPS disciplined crystal oscillators as frequency sources based on the pulse alternating transmission method. -12 This ensures a frequency accuracy of orders of magnitude, which minimizes the radar carrier frequency difference between the primary and secondary satellites. When the frequency difference drops below 1 Hz, a 10 Hz synchronization pulse repetition frequency can meet the Nyquist sampling requirements for the phase synchronization error signal.

[0005] However, existing solutions primarily focus on reducing the probability of phase synchronization failure and lack a recovery mechanism for post-phase synchronization failures. Within a complete phase synchronization cycle, the sampling sequence of synchronization pulses typically includes head synchronization, interpolation synchronization, and tail synchronization. Due to issues such as transmission link instability, channel noise, or hardware switching, the interpolation synchronization signal may be lost or the data may be corrupted. When the synchronization signal (especially the interpolation synchronization portion) in a distributed satellite SAR system is lost, traditional methods are unable to accurately recover its phase information, resulting in large errors in subsequent phase compensation and, consequently, phase synchronization loss. This loss of lock can cause the image to lose focus or interferometry to be impossible, severely impacting system performance. Directly using fixed interpolation or simple algorithms to restore the synchronization signal cannot fully reflect the dynamic phase trend, resulting in large residual phase errors, which in turn affects the interferogram accuracy and imaging focusing performance. Summary of the Invention

[0006] In view of the above problems, the present invention provides a distributed satellite synthetic aperture radar phase synchronization compensation method and device, which can automatically determine and recover the interpolation synchronization phase data lost due to the loss of the synchronization signal, realize accurate phase synchronization compensation, and ensure the accuracy of SAR image focusing and interference processing.

[0007] On one hand, the present invention provides a distributed satellite synthetic aperture radar phase synchronization compensation method, comprising: in a distributed satellite SAR system, extracting synchronization data of a primary satellite and a secondary satellite from the echo data of the primary and secondary satellites respectively, wherein the synchronization data includes head synchronization phase data, interpolation synchronization phase data and tail synchronization phase data; unwrapping the synchronization data of the primary satellite and the secondary satellite; calculating gradient information of the unwrapped synchronization data, and judging whether the interpolation synchronization phase data is damaged according to the gradient information; when it is determined that the interpolation synchronization phase data is not damaged, unwrapping the unwrapped synchronization data; performing pulse compression on the unwrapped synchronization data and extracting the peak phase; generating a compensation phase according to the difference between the peak phases of the primary satellite and the secondary satellite, and interpolating the compensation phase; and using the interpolated compensation phase to perform point-by-point compensation on the echo data of the secondary satellite.

[0008] On the other hand, the present invention provides a distributed satellite synthetic aperture radar phase synchronization compensation device, including: a synchronization data acquisition module, used to extract the synchronization data of the main satellite and the auxiliary satellite from the echo data of the main and auxiliary satellites in the distributed satellite SAR system, wherein the synchronization data includes the first synchronization phase data, the interpolation synchronization phase data and the tail synchronization phase data; an unwrapping module, used to unwrap the synchronization data of the main satellite and the auxiliary satellite; a damage judgment module, used to calculate the gradient information of the unwrapped synchronization data, and judge whether the interpolation synchronization phase data is damaged according to the gradient information; a winding module, used to wind the unwrapped synchronization data when it is determined that the interpolation synchronization phase data is not damaged; a pulse compression module, used to perform pulse compression on the interpolated synchronization data and extract the peak phase; a compensation phase generation module, used to generate the compensation phase according to the difference between the peak phases of the main satellite and the auxiliary satellite, and interpolate the compensation phase; and a phase compensation module, used to use the interpolated compensation phase to compensate the echo data of the auxiliary satellite point by point.

[0009] Compared with the prior art, the distributed satellite synthetic aperture radar phase synchronization compensation method and device provided by the present invention have at least the following beneficial effects:

[0010] (1) The present invention can automatically determine whether the insertion synchronization phase data is damaged and can actively detect damaged data, thereby improving the efficiency and accuracy of data processing.

[0011] (2) The present invention uses the joint slope estimated by the least squares method to fit the interpolation synchronization phase data, which can dynamically capture real-time changes, accurately restore data, and ensure the accuracy of phase compensation.

[0012] (3) As an upgraded solution for the bidirectional phase synchronization pulse transmission of GPS tamed crystal oscillators, the present invention can actively detect and recover damaged data when phase synchronization is lost, thereby enhancing the reliability and accuracy of the system and improving the overall performance of the distributed satellite SAR system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0014] Figure 1 Schematically shows one of the flow charts of a distributed satellite synthetic aperture radar phase synchronization compensation method according to an embodiment of the present invention;

[0015] Figure 2 The second flowchart of the distributed satellite synthetic aperture radar phase synchronization compensation method according to an embodiment of the present invention is schematically shown;

[0016] Figure 3It schematically shows a flow chart of determining whether the insertion synchronization phase data is damaged according to an embodiment of the present invention;

[0017] Figure 4 Schematically shows a pseudo code for determining whether insertion synchronization phase data is damaged according to an embodiment of the present invention;

[0018] Figure 5 A flowchart of recovering damaged interleaving synchronization phase data according to an embodiment of the present invention is schematically shown;

[0019] Figure 6 The block diagram of the distributed satellite synthetic aperture radar phase synchronization compensation device according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0021] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise," "include," etc. used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0022] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0023] Before describing specific embodiments of the present invention in detail, technical terms are first explained to facilitate a better understanding of the present invention.

[0024] Head synchronization, interleaving synchronization, and tail synchronization are key synchronization processes in distributed satellite SAR systems. Head synchronization and tail synchronization typically use higher-frequency synchronization pulses that match the radar's pulse repetition frequency (PRF), resulting in higher synchronization data stability. Interleaving synchronization, on the other hand, uses a low-frequency synchronization signal (e.g., 10 Hz) to supplement the synchronization signals between head synchronization and tail synchronization, ensuring that the system remains synchronized for a long time. The low frequency of interleaving synchronization makes it more susceptible to interference, making its data integrity crucial. Loss of interleaving synchronization can lead to loss of phase synchronization lock, impacting subsequent data processing.

[0025] Wrapping and Unwrapping: Wrapping involves remapping phase data back to a valid range when it exceeds its periodic range (e.g., 0 to 2π) to maintain the phase data within an acceptable range. Unwrapping, on the other hand, restores the unwrapped phase data to a continuous state, eliminating periodic jumps and ensuring a true phase trend. In distributed satellite SAR systems, unwrapping is crucial for ensuring phase data accuracy and avoiding erroneous data due to periodicity limitations.

[0026] The least squares method is a mathematical optimization method widely used in data fitting and estimation. In embodiments of the present invention, the least squares method is used to fit the joint slope of the first and last synchronization phase data, and to recover the damaged interpolation phase data using this joint slope. The goal of the least squares method is to minimize the sum of squares of the fitting errors to obtain the optimal fitting result.

[0027] Gradient analysis: Gradient analysis is used to analyze data trends. In this embodiment of the present invention, the gradient information of the unwrapped synchronization data is calculated and used to determine whether the interpolated synchronization phase data is corrupted. Gradient analysis captures the direction of data change, providing an effective means of detecting corrupted data.

[0028] In view of this, an embodiment of the present invention provides a distributed satellite synthetic aperture radar phase synchronization compensation method and device, which can automatically determine and recover the interpolation synchronization phase data lost due to the loss of the synchronization signal, achieve accurate phase synchronization compensation, and ensure the accuracy of SAR image focusing and interference processing.

[0029] Figure 1 One of the flow charts of the distributed satellite synthetic aperture radar phase synchronization compensation method according to an embodiment of the present invention is schematically shown. Figure 2 The second flowchart of the distributed satellite synthetic aperture radar phase synchronization compensation method according to an embodiment of the present invention is schematically shown.

[0030] like Figure 1 and Figure 2 As shown, the distributed satellite synthetic aperture radar phase synchronization compensation method according to this embodiment may include steps S1 to S7.

[0031] Step S1: In a distributed satellite SAR system, the synchronization data of the primary satellite and the auxiliary satellite are respectively extracted from the echo data of the primary and auxiliary satellites, wherein the synchronization data includes the first synchronization phase data, the interleaving synchronization phase data and the tail synchronization phase data.

[0032] In a distributed satellite SAR system, the primary satellite and the secondary satellite are responsible for transmitting and receiving radar signals respectively. In order to ensure the phase synchronization of the primary and secondary satellites, it is necessary to first extract the synchronization data from the original echo data of the primary and secondary satellites. In the embodiment of the present invention, the synchronization data of the primary and secondary satellites include the first synchronization phase data. , insert synchronous phase data and tail synchronization phase data .

[0033] Typically, the frame frequency of the leading and trailing synchronization phase data matches the radar's pulse repetition frequency (PRF), making errors in their synchronization data rare. In contrast, the frame frequency of the interpolation phase data is lower, typically around 10 Hz, making it susceptible to signal interference and other factors, leading to phase loss. Therefore, in subsequent processing, embodiments of the present invention require simultaneous assessment of the integrity of the interpolation phase data from both the primary and secondary satellites, and appropriate measures to restore it.

[0034] Step S2: untangle the synchronization data of the primary satellite and the auxiliary satellite.

[0035] The distribution range of phase data values ​​is , through the first synchronization phase data of the main satellite and the auxiliary satellite , insert synchronous phase data and tail synchronization phase data By performing unwrapping, we can obtain the cumulative change trend of the phase.

[0036] For example, the synchronous data of the primary and secondary stars are untangled according to the following formula:

[0037]

[0038] Where n is the frame sequence of phase synchronization pulses, and k is a natural number; The nth frame data of any one of the first synchronization phase data, the inserted synchronization phase data and the tail synchronization phase data; It is the nth frame data of the unwrapped synchronization data.

[0039] After unwrapping operation, the first synchronization phase data that changes continuously along the frame sequence can be obtained , insert synchronous phase data Synchronous phase data with tail .

[0040] Step S3: Calculate the gradient information of the unwrapped synchronization data, and determine whether the interpolated synchronization phase data is damaged based on the gradient information.

[0041] Taking into account that the insertion synchronization phase data may be damaged due to signal interference, noise and other factors during the transmission process, the insertion synchronization phase data of the primary and secondary satellites can be judged whether they are damaged to determine whether the insertion synchronization phase data needs to be repaired in the subsequent processing process.

[0042] Figure 3 The flowchart of determining whether the insertion synchronization phase data is damaged according to an embodiment of the present invention is schematically shown.

[0043] like Figure 3 As shown, in this embodiment, the above step S3 calculates the gradient information of the unwrapped synchronization data, and determines whether the interpolated synchronization phase data is damaged according to the gradient information, which can further include the following steps S31 to S32.

[0044] Step S31 : for any frame of data in the unwrapped interpolated synchronization phase data, calculate the phase difference between the next frame of data and the frame of data, and determine the gradient information corresponding to the frame of data according to the phase difference.

[0045] For example, the interpolated phase data after unwrapping Perform gradient calculation. Since the synchronization data is discrete data, you can choose to use frames as units and calculate the gradient information corresponding to any frame of the interpolated synchronization phase data after unwrapping according to the following formula:

[0046]

[0047] Where, is the gradient information corresponding to the nth frame data of the interpolated synchronous phase data, is the nth frame data of the interpolated synchronization phase data after unwrapping, The next frame of data after the nth frame of data.

[0048] Step S32 , counting the positive and negative value ratios of the multi-frame gradient information of the unwrapped interpolation synchronization phase data, and determining whether the interpolation synchronization phase data is damaged according to the positive and negative value ratios.

[0049] For example, determining whether the interpolation synchronization phase data is damaged based on the positive-negative value ratio includes: counting the positive value ratio and the negative value ratio of multiple frames of gradient information; judging whether the positive value ratio is greater than a preset ratio threshold or whether the negative value ratio is greater than a preset ratio threshold, and if so, determining that the interpolation synchronization phase data is not damaged; otherwise, determining that the interpolation synchronization phase data is damaged.

[0050] Figure 4 The pseudo code for determining whether the interleaving synchronization phase data is damaged according to an embodiment of the present invention is schematically shown.

[0051] For ease of understanding, remember the gradient information The total number of frames is , then the above step S32 can be used as follows Figure 4 The pseudo code shown is shown. is a non-negative number of frames, is the number of frames with negative value; T is the preset ratio threshold, which can be set or adjusted according to the actual situation. Figure 4 As can be seen, this embodiment of the present invention extracts gradient information from the unwrapped interpolation synchronization phase data and calculates the ratio of positive and negative values ​​in the gradient information. If either the positive ratio (condition 1) is greater than a preset ratio threshold, or the negative ratio (condition 2) is greater than a preset ratio threshold, is not met (i.e., if a majority of symbols are absent), then the unwrapped interpolation synchronization phase data does not conform to normal phase accumulation patterns and is considered corrupted. If the data is not corrupted, the process proceeds to step S4. If the data is corrupted, the interpolation synchronization phase data will need to be repaired in subsequent processing.

[0052] In this way, embodiments of the present invention analyze the unwrapped interpolation synchronization phase data to obtain a cumulative change trend of the interpolation synchronization phase data. Based on this cumulative change trend, gradient information is calculated, and the positive and negative signs of the gradient are used for threshold detection to determine whether the interpolation synchronization phase data is corrupted.

[0053] Step S4: When it is determined that the inserted synchronization phase data is not damaged, the unwrapped synchronization data is rewound.

[0054] It should be noted that, since the correctness detection and repair of the insertion synchronization phase data must be performed after unwrapping, therefore, if it is determined in step S3 that the insertion synchronization phase data is damaged and the damaged insertion synchronization phase data is detected and repaired, or if it is determined in step S3 that the insertion synchronization phase data is not damaged, the synchronization data of the primary and auxiliary satellites after unwrapping can be rewound and the data can be remapped back to the original range to keep the data wrapped, thus ensuring that subsequent processing operations are not affected.

[0055] For example, the unwrapped synchronization data is entangled according to the following formula:

[0056]

[0057] Where, means taking x modulo y, It is the nth frame data of the synchronous data after winding.

[0058] After phase wrapping, the first synchronous phase data of the primary and secondary satellites that continuously change along the frame sequence can be obtained. , insert synchronous phase data Synchronous phase data with tail .

[0059] Step S5: performing pulse compression on the wrapped synchronization data to extract the peak phase.

[0060] The synchronized data from the primary and secondary satellites can be pulse compressed using a matched filter or other pulse compression algorithm to improve the signal's temporal resolution. After pulse compression, the peak phase of the signal can be extracted for subsequent phase compensation.

[0061] Step S6: generating a compensation phase according to the difference between the peak phases of the primary satellite and the secondary satellite, and interpolating the compensation phase.

[0062] In this embodiment, half of the difference obtained by subtracting the peak phase of the auxiliary satellite from the peak phase of the primary satellite can be used as the compensation phase; and the compensation phase is interpolated according to the azimuth number of the auxiliary satellite's echo data.

[0063] For example, the compensation phase is generated according to the following formula:

[0064]

[0065] Where, is the peak phase of the primary star, is the peak phase of the auxiliary star, To compensate the phase.

[0066] The generated compensation phase also needs to be interpolated to align with the azimuth of the auxiliary satellite's echo data. For example, interpolation can be performed based on the resolution and sampling rate of the auxiliary satellite's echo data to ensure that the compensation phase accurately matches the echo data in space and time.

[0067] Step S7: Using the interpolated compensation phase, the echo data of the auxiliary satellite is compensated point by point.

[0068] After obtaining the interpolated compensation phase, the auxiliary satellite's echo data is compensated point by point to ensure synchronization with the primary satellite's echo data. After compensation is completed, the synchronization and consistency of the auxiliary satellite's echo data can be verified. If the data meets the accuracy requirements, the subsequent image processing and analysis steps can be carried out as needed.

[0069] Figure 5 The flowchart of recovering damaged interleaving synchronization phase data according to an embodiment of the present invention is schematically shown.

[0070] like Figure 2 and Figure 5 As shown, in this embodiment, the distributed satellite synthetic aperture radar phase synchronization compensation method further includes steps S41 and S42 after the above step S3.

[0071] Step S41 : when it is determined that the interleaved synchronization phase data is damaged, estimating the joint slope of the unwrapped first synchronization phase data and the unwrapped last synchronization phase data.

[0072] Assume that the total number of frames of the first synchronization phase data and the last synchronization phase data are 、 , the first synchronization phase data after unwrapping can be obtained based on the least squares method. Synchronous phase data with tail The joint slope of is estimated.

[0073] For example, the joint slope of the unwrapped first synchronization phase data and the tail synchronization phase data is estimated based on the least squares method according to the following formula:

[0074]

[0075] Where N is the sum of the number of frames of the first synchronization phase data and the last synchronization phase data, , is the phase value of the first synchronization phase data and the tail synchronization phase data after unwrapping, With the phase value The corresponding frame sequence value; and They are and The mean of is the joint slope.

[0076] In step S42, linear interpolation is performed using the joint slope and the unwrapped first synchronization phase data, and the damaged interpolated synchronization phase data is restored using the interpolated data, and the process returns to step S4 to perform an intertwining operation on the unwrapped synchronization data.

[0077] Within a single operating cycle (including the initial, interpolation, and tail synchronization phase data), due to the short time span, it can be assumed that the frequency sources of the primary and secondary satellites remain stable. Therefore, the slope of the synchronization data from both satellites relative to the frame time should remain essentially unchanged. In other words, the slope values ​​of the initial and tail synchronization phase data for both the primary and secondary satellites can be used as an estimate of the interpolation synchronization slope. Based on this assumption, the previously estimated joint slope can be used to recover damaged interpolation synchronization phase data through interpolation.

[0078] For example, using the joint slope With the first synchronization phase data after unwrapping Perform linear interpolation and use the interpolated data to restore the interpolation synchronization phase data:

[0079]

[0080] Where n is the number of sequences of interpolated synchronization phase data; b is the intercept term, which is the last frame phase value of the first synchronization phase data after unwrapping, that is, ; is the pulse repetition frequency of the interleaved synchronization phase data, for example 10 Hz; It is the restored data of the n-th frame data of the interleaved synchronization phase data after de-wrapping.

[0081] In this way, the embodiment of the present invention uses the least squares method to estimate a joint slope based on the unwrapped head and tail synchronization phase data. Assuming that the frequency sources of the primary and secondary satellites remain stable over a short period of time, this joint slope is used to determine the phase variation trend between the primary and secondary satellites. This provides the slope required for fitting interpolation to recover damaged interpolation phase data. This embodiment of the present invention can automatically determine whether interpolation phase data is corrupted and proactively detect damaged data, thereby improving data processing efficiency and accuracy.

[0082] It should be noted that in addition to the least squares method, the joint slope of the unwrapped first synchronization phase data and the tail synchronization phase data can also be estimated based on fitting methods such as polynomial fitting, spline interpolation or robust fitting (such as RANSAC), thereby restoring the damaged interpolated synchronization phase data.

[0083] In summary, an embodiment of the present invention provides a distributed satellite synthetic aperture radar phase synchronization compensation method that combines unwrapping and gradient analysis to actively detect interpolation synchronization phase data, enabling real-time detection and discovery of data corruption. By combining the slope estimated by least squares fitting with linear interpolation to recover damaged data, a new data repair technology is proposed. The method provided by the present invention can accurately capture the phase change trend between the primary and secondary satellites, thereby recovering the lost interpolation synchronization signal, effectively reducing the residual phase error, and ensuring the accuracy of subsequent phase compensation.

[0084] Compared with traditional simple interpolation methods, the method provided by the present invention has stronger robustness in processing noisy and dynamically changing data, and can maintain high reliability even when the data is highly random and the interference environment is complex.

[0085] The method provided by this invention ensures that the system can continue to operate normally even if some synchronization signals are lost. Through active detection and data repair, the system can still maintain normal operation even if the interpolation phase data synchronization is lost. This technical improvement significantly improves the overall quality of SAR imaging and interferometric processing, resulting in more accurate and stable imaging results.

[0086] The method provided by this invention is based on the actual data processing flow of a distributed satellite SAR system. The proposed technical approach has high engineering applicability. It is highly compatible with existing systems, facilitating technology upgrades on existing platforms. The solution of this invention can be quickly integrated into existing SAR systems, improving processing efficiency and data quality, thus possessing significant practical value.

[0087] Based on the method disclosed in the above embodiment, the present invention also provides a distributed satellite synthetic aperture radar phase synchronization compensation device, which will be combined with Figure 6 The device is described in detail.

[0088] Figure 6 The block diagram of the distributed satellite synthetic aperture radar phase synchronization compensation device according to an embodiment of the present invention is schematically shown.

[0089] like Figure 6 As shown, according to this embodiment, the distributed satellite synthetic aperture radar phase synchronization compensation device 600 includes a synchronization data acquisition module 610, an unwrapping module 620, a damage judgment module 630, a winding module 640, a pulse compression module 650, a compensation phase generation module 660 and a phase compensation module 670.

[0090] The synchronization data acquisition module 610 is used to extract the synchronization data of the primary satellite and the auxiliary satellite from the echo data of the primary and auxiliary satellites in the distributed satellite SAR system, wherein the synchronization data includes the first synchronization phase data, the insertion synchronization phase data and the tail synchronization phase data.

[0091] The unwrapping module 620 is used to unwrap the synchronization data of the primary satellite and the auxiliary satellite.

[0092] The damage judgment module 630 is used to calculate the gradient information of the unwrapped synchronization data and judge whether the interpolation synchronization phase data is damaged according to the gradient information.

[0093] The wrapping module 640 is configured to wrap the unwrapped synchronization data when it is determined that the inserted synchronization phase data is not damaged.

[0094] The pulse compression module 650 is used to perform pulse compression on the wrapped synchronization data and extract the peak phase.

[0095] The compensation phase generating module 660 is configured to generate a compensation phase according to the difference between the peak phases of the primary satellite and the secondary satellite, and to interpolate the compensation phase.

[0096] The phase compensation module 670 is used to compensate the echo data of the auxiliary satellite point by point using the interpolated compensation phase.

[0097] It should be noted that the embodiment of the device part is similar to the embodiment of the method part, and the technical effects achieved are also similar. For specific details, please refer to the above-mentioned method embodiment part, which will not be repeated here.

[0098] According to an embodiment of the present invention, any multiple of the synchronous data acquisition module 610, the dewrapping module 620, the damage determination module 630, the wrapping module 640, the pulse compression module 650, the compensated phase generation module 660, and the phase compensation module 670 may be combined into a single module, or any one of these modules may be split into multiple modules. Alternatively, at least part of the functionality of one or more of these modules may be combined with at least part of the functionality of other modules and implemented in a single module. According to an embodiment of the present invention, at least one of the synchronous data acquisition module 610, the dewrapping module 620, the damage determination module 630, the wrapping module 640, the pulse compression module 650, the compensated phase generation module 660, and the phase compensation module 670 may be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application-specific integrated circuit (ASIC), or may be implemented in hardware or firmware through any other suitable means of circuit integration or packaging, or implemented in any one of software, hardware, and firmware, or any suitable combination of these. Alternatively, at least one of the synchronous data acquisition module 610, the unwrapping module 620, the damage judgment module 630, the winding module 640, the pulse compression module 650, the compensation phase generation module 660 and the phase compensation module 670 can be at least partially implemented as a computer program module, and when the computer program module is run, the corresponding function can be performed.

[0099] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, program segment, or a part of code, and the above-mentioned module, program segment, or a part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart, can be implemented with a dedicated hardware-based system that performs the specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0100] It will be understood by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or coupled in various ways, even if such combinations or couplings are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention may be combined and / or coupled in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or couplings fall within the scope of the present invention.

[0101] The above describes embodiments of the present invention. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A distributed satellite synthetic aperture radar phase synchronization compensation method, characterized in that: include: In a distributed satellite SAR system, synchronization data of the primary satellite and the auxiliary satellite are respectively extracted from the echo data of the primary and auxiliary satellites, wherein the synchronization data includes the first synchronization phase data, the insertion synchronization phase data and the tail synchronization phase data; Untangling the synchronization data of the primary satellite and the auxiliary satellite; Calculating gradient information of the unwrapped synchronization data, and determining whether the interpolated synchronization phase data is damaged according to the gradient information; When it is determined that the insertion synchronization phase data is not damaged, reeling the unreeled synchronization data; Perform pulse compression on the wrapped synchronous data and extract the peak phase; generating a compensation phase according to the difference between the peak phases of the primary satellite and the secondary satellite, and interpolating the compensation phase; Using the interpolated compensation phase, compensating the echo data of the auxiliary satellite point by point; The step of calculating the gradient information of the unwrapped synchronization data and determining whether the interpolation synchronization phase data is damaged according to the gradient information includes: For any frame of data in the unwrapped interpolated synchronization phase data, calculating a phase difference between the next frame of data and the frame of data, and determining gradient information corresponding to the frame of data according to the phase difference; The positive and negative value ratios of the gradient information of multiple frames of the unwrapped interpolation synchronization phase data are counted, and whether the interpolation synchronization phase data is damaged is determined according to the positive and negative value ratios.

2. The method according to claim 1, characterized in that The synchronization data of the primary and secondary satellites are untangled according to the following formula: Where n is the frame sequence of phase synchronization pulses, and k is a natural number; The nth frame data of any one of the first synchronization phase data, the interleaved synchronization phase data and the tail synchronization phase data; It is the nth frame data of the unwrapped synchronization data.

3. The method according to claim 1, characterized in that Determining whether the insertion synchronization phase data is damaged according to the positive-negative value ratio includes: Counting the positive value ratio and the negative value ratio of the gradient information of multiple frames; It is determined whether the positive value ratio is greater than a preset ratio threshold or whether the negative value ratio is greater than a preset ratio threshold. If so, it is determined that the interpolation synchronization phase data is not damaged; otherwise, it is determined that the interpolation synchronization phase data is damaged.

4. The method according to claim 1, wherein The method further comprises: When it is determined that the interleaved synchronization phase data is damaged, estimating a joint slope of the unwrapped first synchronization phase data and the unwrapped tail synchronization phase data; Linear interpolation is performed using the joint slope and the unwrapped first synchronization phase data, the damaged interpolation synchronization phase data is restored using the interpolated data, and the operation of wrapping the unwrapped synchronization data is returned.

5. The method according to claim 4, characterized in that The joint slope of the unwrapped first synchronization phase data and the tail synchronization phase data is estimated according to the following formula: Where N is the sum of the number of frames of the first synchronization phase data and the last synchronization phase data, is the phase value of the first synchronization phase data and the tail synchronization phase data after unwrapping, With the phase value The corresponding frame sequence value; and They are and The mean of is the joint slope.

6. The method according to claim 5, characterized in that The linear interpolation is performed using the joint slope and the unwrapped first synchronization phase data according to the following formula, and the interpolated synchronization phase data is restored using the interpolated data: Where n is the number of sequences of interpolated synchronization phase data; b is the intercept term, which is the last frame phase value of the first synchronization phase data after unwrapping. is the pulse repetition frequency of the interleaved synchronization phase data, It is the restored data of the n-th frame data of the interleaved synchronization phase data after de-wrapping.

7. The method according to claim 1, characterized in that The unwrapped synchronization data is entangled according to the following formula: Where, means taking x modulo y, It is the nth frame data of the synchronous data after winding.

8. The method according to claim 1, characterized in that Generating a compensation phase according to the difference between the peak phases of the primary star and the secondary star, and interpolating the compensation phase, comprises: half of the difference obtained by subtracting the peak phase of the auxiliary satellite from the peak phase of the primary satellite is used as the compensation phase; The compensation phase is interpolated according to the azimuth number of the echo data of the auxiliary satellite.

9. A distributed satellite synthetic aperture radar phase synchronization compensation device, characterized in that: include: A synchronization data acquisition module is used to extract synchronization data of the primary satellite and the auxiliary satellite from the echo data of the primary and auxiliary satellites in the distributed satellite SAR system, wherein the synchronization data includes the first synchronization phase data, the insertion synchronization phase data and the tail synchronization phase data; An unwrapping module, configured to unwrap the synchronization data of the primary satellite and the auxiliary satellite; a damage judgment module, configured to calculate, for any frame of data in the unwrapped interpolation synchronization phase data, a phase difference between the next frame of data and the frame of data, and determine gradient information corresponding to the frame of data based on the phase difference; and to calculate a positive-negative value ratio of the gradient information of multiple frames of the unwrapped interpolation synchronization phase data, and determine whether the interpolation synchronization phase data is damaged based on the positive-negative value ratio; a winding module, configured to, when determining that the insertion synchronization phase data is not damaged, wind the unwound synchronization data; A pulse compression module is used to perform pulse compression on the wrapped synchronous data and extract the peak phase; a compensation phase generating module, configured to generate a compensation phase according to the difference between the peak phases of the primary satellite and the secondary satellite, and to interpolate the compensation phase; The phase compensation module is used to compensate the echo data of the auxiliary satellite point by point using the interpolated compensation phase.

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