Distributed satellite synthetic aperture radar phase synchronization compensation method and device

Abstract

The invention provides a distributed satellite synthetic aperture radar (SAR) phase synchronization compensation method and device, and relates to the technical field of distributed satellite SAR. The method comprises the steps that in a distributed satellite SAR system, synchronous data of a main satellite and synchronous data of auxiliary satellites are extracted from echo data of the main satellite and the auxiliary satellites respectively, and the synchronous data comprise first synchronous phase data, insertion synchronous phase data and tail synchronous phase data; unwrapping the synchronous 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 or not according to the gradient information; when it is determined that the insertion synchronization phase data is not damaged, winding the unwound synchronization data; performing pulse compression on the wound synchronous data, and extracting a 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 performing point-by-point compensation on the echo data of the auxiliary satellite by using the interpolated compensation phase.

Description

Technical Field

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

[0002] A distributed satellite synthetic aperture radar (SAR) system usually consists of two or more satellites. One satellite (the master satellite) is responsible for transmitting radar signals and receiving echo signals, while other satellites (slave satellites) only passively receive echo signals. However, the distributed design of the master and slave satellites brings about a phase synchronization problem, which mainly causes phase errors for the following two reasons: First, the master satellite and the slave satellites respectively use independent crystal oscillators as frequency sources, which results in inconsistent frequencies and thus generates phase deviations; Second, the transmitted phase noise and received phase noise of the master satellite and the slave satellites are uncorrelated and cannot cancel each other out as in the traditional single-satellite system. Therefore, in order to ensure phase synchronization, a suitable phase compensation method must be adopted for a distributed or dual-satellite formation SAR system.

[0003] Currently, the pulse alternation pair transmission method is considered to be one of the relatively reliable solutions in engineering. This method was proposed by Younis of DLR and successfully applied to the TerraSAR-X / TanDEM-X system. The pulse alternation pair transmission method can significantly improve the synchronization stability by establishing a dedicated synchronization link between the master and slave satellites and using bidirectional transmission of synchronization pulses. However, since the radar reference frequency sources of the master satellite and the slave satellites respectively use high-stability crystal oscillators, and the frequency accuracy of the crystal oscillators is usually on the order of 10 -6 magnitude, the X-band radar carrier frequency difference between the master satellite and the slave satellites may be close to 20 kHz, which is much larger than the repetition frequency of the synchronization pulses, making the extraction of phase synchronization errors more complicated.

[0004] To further improve the accuracy, the prior art has, on the basis of the pulse alternation pair transmission method, adopted a GPS-tamed crystal oscillator as the frequency source. Since the atomic clock used on GPS satellites has a frequency accuracy on the order of 10 -12 magnitude, the radar carrier frequency difference between the master satellite and the slave satellites is small enough. When the frequency difference drops below 1 Hz, using a synchronization pulse repetition frequency of 10 Hz can meet the Nyquist sampling requirements for the phase synchronization error signal.

[0005] However, existing solutions mainly focus on reducing the probability of phase synchronization failure and lack a recovery mechanism for dealing with phase synchronization failure. During a complete phase synchronization cycle, the sampling sequence of synchronization pulses usually includes initial synchronization, inserted synchronization, and end synchronization. Due to issues such as unstable transmission links, channel noise, or hardware switching, the inserted synchronization signal may be lost or data may be corrupted. When the synchronization signal (especially the inserted synchronization part) in a distributed satellite SAR system is lost, traditional methods cannot accurately recover its phase information, resulting in a large error in subsequent phase compensation, thus triggering phase synchronization unlocking. This unlocking will cause the image to be out of focus or unable to perform interferometric measurement, seriously affecting the working performance of the system. If a fixed interpolation or a simple algorithm is directly used to recover the synchronization signal, it cannot fully reflect the dynamic change trend of the phase, resulting in a large residual phase error, which in turn affects the accuracy of the interferogram and the imaging focusing performance. Summary of the Invention

[0006] In view of the above problems, the present invention provides a method and device for phase synchronization compensation of a distributed satellite synthetic aperture radar, which can automatically judge and recover the inserted synchronization phase data missing due to the loss of the synchronization signal, achieve accurate phase synchronization compensation, and ensure the accuracy of SAR image focusing and interferometric processing.

[0007] On the one hand, the present invention provides a method for phase synchronization compensation of a distributed satellite synthetic aperture radar, including: in a distributed satellite SAR system, extracting the synchronization data of the master satellite and the slave satellite from the echo data of the master and slave satellites respectively, where the synchronization data includes initial synchronization phase data, inserted synchronization phase data, and end synchronization phase data; unwrapping the synchronization data of the master satellite and the slave satellite; calculating the gradient information of the unwrapped synchronization data, and judging whether the inserted synchronization phase data is damaged according to the gradient information; in the case of determining that the inserted synchronization phase data is not damaged, wrapping the unwrapped synchronization data; performing pulse compression on the wrapped synchronization data to extract the peak phase; generating a compensation phase according to the difference between the peak phases of the master satellite and the slave satellite, and interpolating the compensation phase; using the interpolated compensation phase to perform point-by-point compensation on the echo data of the slave 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, configured to extract the synchronization data of the master satellite and the slave satellite from the echo data of the master and slave satellites respectively in a distributed satellite SAR system, wherein the synchronization data includes initial synchronization phase data, interpolation synchronization phase data, and tail synchronization phase data; an unwrapping module, configured to unwrap the synchronization data of the master satellite and the slave satellite; a damage determination module, configured to calculate the gradient information of the unwrapped synchronization data, and determine whether the interpolation synchronization phase data is damaged according to the gradient information; a wrapping module, configured to wrap the unwrapped synchronization data when it is determined that the interpolation synchronization phase data is not damaged; a pulse compression module, configured to perform pulse compression on the wrapped synchronization data to extract the peak phase; a compensation phase generation module, configured to generate a compensation phase according to the difference between the peak phases of the master satellite and the slave satellite, and perform interpolation on the compensation phase; and a phase compensation module, configured to perform point-by-point compensation on the echo data of the slave satellite by using the interpolated compensation phase.

[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 interpolation 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, can dynamically capture real-time changes, accurately recover the data, and ensure the phase compensation accuracy.

[0012] (3) As an upgraded solution to the two-way transmission phase synchronization pulse scheme of GPS-tamed crystal oscillators, the present invention can actively detect and recover damaged data when the phase synchronization is unlocked, enhance the reliability and accuracy of the system, and improve the overall performance of the distributed satellite SAR system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features, and advantages of the present invention will become more clear. In the drawings:

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

[0015] Figure 2 Schematically shows another flowchart of the distributed satellite synthetic aperture radar phase synchronization compensation method according to an embodiment of the present invention;

[0016] Figure 3Schematically shows a flowchart for determining whether the inserted synchronization phase data is damaged according to an embodiment of the present invention;

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

[0018] Figure 5 Schematically shows a flowchart for recovering the damaged inserted synchronization phase data according to an embodiment of the present invention;

[0019] Figure 6 Schematically shows a block diagram of a distributed satellite synthetic aperture radar phase synchronization compensation device according to an embodiment of the present invention. Detailed implementation manners

[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 merely exemplary and are not intended to limit the scope of the present invention. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a thorough understanding of the embodiments of the present invention. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present invention.

[0021] The terms used herein are merely for describing specific embodiments and are not intended to limit the present invention. The terms "including", "comprising", 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 the specific embodiments of the present invention in detail, technical terms are first explained to facilitate a better understanding of the present invention.

[0024] Initial synchronization, inserted synchronization, and end synchronization: are key synchronization processes in a distributed satellite SAR system. Among them, initial synchronization and end synchronization usually use synchronization pulses with a higher frequency, which match the pulse repetition frequency (PRF) of the radar, so the synchronization data has higher stability. The inserted synchronization uses a low-frequency synchronization signal (such as 10 Hz) to supplement the synchronization signal between the initial synchronization and the end synchronization, ensuring that the system remains synchronized for a long time. The low frequency of the inserted synchronization makes it more vulnerable to interference, so the integrity of its data is crucial. Once lost, it may cause the phase synchronization to unlock and affect subsequent data processing.

[0025] Wrapping and unwrapping: Wrapping refers to the process of remapping phase data back to the valid range when it exceeds its periodic range (such as 0 to 2π) to keep the phase data within an acceptable range. Unwrapping, on the other hand, is to restore the wrapped phase data to continuous variation, eliminate periodic jumps, and ensure the true variation trend of the phase. In a distributed satellite SAR system, the unwrapping operation is crucial for ensuring the accuracy of phase data, avoiding incorrect data caused by periodic limitations.

[0026] Least squares method: It is a mathematical optimization method widely used in data fitting and estimation. In the embodiments of the present invention, the least squares method is used to fit the combined slope of the head synchronization phase data and the tail synchronization phase data, and the damaged interpolation synchronization phase data is restored through this combined slope. The goal of the least squares method is to minimize the sum of the squares of the fitting errors to obtain the optimal fitting result.

[0027] Gradient analysis: Gradient analysis is used to analyze the variation trend of data. In the embodiments of the present invention, by calculating the gradient information of the unwrapped synchronization data and using the gradient information (positive and negative sign information) to determine whether the interpolation synchronization phase data is damaged. Gradient analysis provides an effective means for detecting damaged data by capturing the direction of data change.

[0028] In view of this, the embodiments of the present invention provide a distributed satellite synthetic aperture radar phase synchronization compensation method and device, which can automatically judge and restore the missing interpolation synchronization phase data 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 flowcharts of the distributed satellite synthetic aperture radar phase synchronization compensation method according to the embodiments of the present invention is schematically shown. Figure 2 Another flowchart of the distributed satellite synthetic aperture radar phase synchronization compensation method according to the embodiments of the present invention is schematically shown.

[0030] As Figure 1 and Figure 2 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, extract the synchronization data of the master satellite and the slave satellite from the echo data of the master and slave satellites respectively, where the synchronization data includes head synchronization phase data, interpolation synchronization phase data, and tail synchronization phase data.

[0032] In a distributed satellite SAR system, the master satellite and the slave satellite are respectively responsible for transmitting and receiving radar signals. To ensure the phase synchronization between the master and slave satellites, it is necessary to first extract synchronization data from the original echo data of the master and slave satellites. In the embodiments of the present invention, the synchronization data of the master satellite and the slave satellite both include the first synchronization phase data , the inserted synchronization phase data and the tail synchronization phase data .

[0033] Normally, the frame frequencies of the first synchronization phase data and the tail synchronization phase data match the pulse repetition frequency (PRF) of the radar. Therefore, errors in these two synchronization data rarely occur. Relatively speaking, the frame frequency of the inserted synchronization phase data is relatively low, usually about 10 Hz, and it is easily affected by signal interference or other factors, resulting in phase unlocking. Therefore, in the subsequent processing of the embodiments of the present invention, it is necessary to simultaneously judge the integrity of the inserted synchronization phase data of the master satellite and the slave satellite and take appropriate measures for recovery.

[0034] Step S2: Unwrap the synchronization data of the master satellite and the slave satellite.

[0035] The distribution range of the phase data values is . By unwrapping the first synchronization phase data , the inserted synchronization phase data and the tail synchronization phase data of the master satellite and the slave satellite, the cumulative change trend of the phase can be obtained.

[0036] For example, the synchronization data of the master satellite and the slave satellite are unwrapped according to the following formula:

[0037]

[0038] In the formula, n is the frame sequence of the phase synchronization pulse, and k is a natural number; is the nth frame data of any one of the first synchronization phase data, the inserted synchronization phase data, and the tail synchronization phase data; is the nth frame data of the unwrapped synchronization data.

[0039] After the unwrapping operation, the first synchronization phase data , the inserted synchronization phase data and the tail synchronization phase data that change continuously along the frame sequence can be obtained.

[0040] Step S3: Calculate the gradient information of the unwrapped synchronization data, and judge whether the inserted synchronization phase data is damaged according to the gradient information.

[0041] Considering that the interpolation synchronization phase data may be damaged during the transmission process due to factors such as signal interference and noise, it is possible to determine whether the interpolation synchronization phase data of the primary satellite and the secondary satellite is damaged, so as to decide whether it is necessary to repair the interpolation synchronization phase data during the subsequent processing.

[0042] Figure 3 Schematically shows a flowchart for determining whether the interpolation synchronization phase data is damaged according to an embodiment of the present invention.

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

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

[0045] For example, perform gradient calculation on the unwrapped interpolation synchronization phase data Since the synchronization data is discrete data, it is possible to select frames as the unit and calculate the gradient information corresponding to any one frame of data in the unwrapped interpolation synchronization phase data according to the following formula:

[0046]

[0047] In the formula, is the gradient information corresponding to the nth frame of data of the interpolation synchronization phase data, is the nth frame of data of the unwrapped interpolation synchronization phase data, is the next frame of data of this nth frame of data.

[0048] Step S32, count the positive and negative value ratios of the gradient information of multiple frames of the unwrapped interpolation synchronization phase data, and determine 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 according to the positive and negative value ratios includes: counting the positive value ratio and the negative value ratio of the gradient information of multiple frames; 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. 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.

[0050] Figure 4 Schematically shows the pseudocode for determining whether the interpolation synchronization phase data is damaged according to an embodiment of the present invention.

[0051] For ease of understanding, denote the total number of frames of the gradient information as , then the above step S32 can be represented by the pseudo-code as follows Figure 4 . Among them, is the number of frames with non-negative values, is the number of frames with negative values; T is the preset ratio threshold, which can be set or adjusted according to the actual situation. As can be seen from Figure 4 , in the embodiment of the present invention, the gradient information is taken for the unwrapped interpolation synchronization phase data, and the ratio of positive and negative values in the gradient information is statistically analyzed. If any one of the conditions that the positive value ratio in condition one is greater than the preset ratio threshold and the negative value ratio in condition two is greater than the preset ratio threshold cannot be satisfied, that is, there is no symbol in the majority proportion, it indicates that the unwrapped interpolation synchronization phase data does not conform to the normal phase accumulation law, and it is determined that the interpolation synchronization phase data is damaged. If the data is not damaged, the following step S4 is entered. If the data is damaged, the interpolation synchronization phase data needs to be repaired in the subsequent processing.

[0052] In this way, the embodiment of the present invention analyzes the unwrapped interpolation synchronization phase data, obtains the cumulative change trend of the interpolation synchronization phase data. Based on this cumulative change trend, the gradient information is calculated, and the threshold detection is performed using the positive and negative sign information of the gradient to determine whether there is damage to the interpolation synchronization phase data.

[0053] Step S4, when it is determined that the interpolation synchronization phase data is not damaged, the unwrapped synchronization data is wrapped.

[0054] It should be noted that since the correctness detection and repair of the interpolation synchronization phase data must be performed after unwrapping, therefore, after it is determined through the above step S3 that the interpolation synchronization phase data is damaged, and the damaged interpolation synchronization phase data is completed with detection and repair, or after it is determined through the above step S3 that the interpolation synchronization phase data is not damaged, then the synchronization data after unwrapping the primary satellite and the secondary satellite can be wrapped, and the data is remapped back to the original range to maintain the wrapped state of the data, so as to ensure that the subsequent processing operations are not affected.

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

[0056]

[0057] In the formula, represents taking the modulus of x by y, is the nth frame data of the wrapped synchronization data.

[0058] After phase wrapping, the first synchronization phase data , the interpolation synchronization phase data and the tail synchronization phase data that continuously change along the frame sequence of the primary satellite and the secondary satellite can be obtained.

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

[0060] The wrapped synchronization data of the primary satellite and the secondary satellite can be pulse-compressed through a matched filter or other pulse compression algorithms to improve the time resolution of the signal. After pulse compression, the peak phase of the signal can be extracted for subsequent phase compensation.

[0061] Step S6: Generate a compensation phase based on the difference between the peak phases of the primary satellite and the secondary satellite, and perform interpolation on the compensation phase.

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

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

[0064]

[0065] In the formula, is the peak phase of the primary satellite, is the peak phase of the secondary satellite, is the compensation phase.

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

[0067] Step S7: Use the interpolated compensation phase to perform point-by-point compensation on the echo data of the secondary satellite.

[0068] After obtaining the interpolated compensation phase, the echo data of the secondary satellite is compensated point by point to ensure the synchronization of the echo data of the secondary satellite and the echo data of the primary satellite. After the compensation is completed, the synchronization and consistency of the echo data of the secondary satellite can be continuously verified. If the data meets the accuracy requirements, subsequent image processing and analysis steps can be entered according to actual needs.

[0069] Figure 5 Schematically shows a flowchart for recovering damaged interpolation synchronization phase data according to an embodiment of the present invention.

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

[0071] Step S41: When it is determined that the interpolation synchronization phase data is damaged, estimate the combined slope of the unwrapped first synchronization phase data and the last synchronization phase data.

[0072] Let the total number of frames of the first synchronization phase data and the last synchronization phase data be 、 , respectively. Then, based on the least squares method, the combined slope of the unwrapped first synchronization phase data and the last synchronization phase data can be estimated.

[0073] For example, estimate the combined slope of the unwrapped first synchronization phase data and the last synchronization phase data based on the least squares method according to the following formula:

[0074]

[0075] In the formula, 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 unwrapped first synchronization phase data and the last synchronization phase data, is the frame sequence value corresponding to the phase value ; and are the means of and , respectively, and is the combined slope.

[0076] Step S42: Use the combined slope and the unwrapped first synchronization phase data for linear interpolation, and use the interpolated data to recover the damaged interpolation synchronization phase data, and return to the operation of winding the unwrapped synchronization data in step S4 above.

[0077] During one working cycle (including the first synchronization phase data, the interpolation synchronization phase data, and the last synchronization phase data), since the time span is short, it can be assumed that the frequency sources of the master satellite and the slave satellite remain stable. Therefore, the slopes of the synchronization data of the two satellites with respect to the frame time should remain basically unchanged. In other words, for both the master satellite and the slave satellite, the slope values of their respective first synchronization phase data and last synchronization phase data can be used as the slope estimates for interpolation synchronization. Based on this assumption, the damaged interpolation synchronization phase data can be recovered by interpolation using the previously estimated combined slope.

[0078] For example, linearly interpolate using the combined slope and the unwrapped first synchronization phase data according to the following formula to recover the interpolation synchronization phase data with the interpolated data:

[0079]

[0080] In the formula, n is the number of sequences of inserted synchronous phase data; b is the intercept term, and its value is the phase value of the last frame of the first synchronous phase data after phase unwrapping, that is ; is the pulse repetition frequency of the inserted synchronous phase data, for example, 10 Hz; is the restored data of the nth frame of the inserted synchronous phase data after phase unwrapping.

[0081] In this way, according to the first synchronous phase data and the last synchronous phase data after phase unwrapping, the embodiment of the present invention uses the least squares method to perform joint slope estimation. Assuming that the frequency sources of the master satellite and the slave satellite remain stable in a short period of time, the phase change trend between the master satellite and the slave satellite is obtained through this joint slope, and then the slope required for fitting interpolation is provided for the restoration of damaged inserted synchronous phase data. Thus, the embodiment of the present invention can automatically judge whether the inserted synchronous phase data is damaged, and can actively detect damaged data, thereby improving the efficiency and accuracy of data processing.

[0082] It should be noted that in addition to the least squares method, other fitting methods such as polynomial fitting, spline interpolation or robust fitting (such as RANSAC) can also be used to estimate the joint slope of the first synchronous phase data and the last synchronous phase data after phase unwrapping, so as to restore damaged inserted synchronous phase data.

[0083] In summary, the embodiment of the present invention provides a method for phase synchronization compensation of a distributed satellite synthetic aperture radar, which combines phase unwrapping and gradient analysis to actively detect inserted synchronous phase data, and can detect and discover data damage in real time. By fitting and estimating the slope by the joint least squares method and combining linear interpolation to restore 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 master satellite and the slave satellite, thereby restoring the lost inserted synchronous signal, effectively reducing the residual phase error, and ensuring the accuracy of subsequent phase compensation.

[0084] Compared with the traditional simple interpolation method, the method provided by the present invention has stronger robustness in processing noise and dynamically changing data, and can still maintain high reliability under the conditions of strong data randomness and complex interference environment.

[0085] The method provided by the present invention ensures that even if part of the synchronous signal is lost, the system can still operate continuously and normally. Through active detection and data repair, in the case of synchronous loss of the inserted synchronous phase data, the continuous normal operation of the system can still be ensured. This technical improvement significantly improves the overall quality of SAR imaging and interferometric processing, making the imaging effect more accurate and stable.

[0086] The method provided by the present invention is based on the actual data processing flow of a distributed satellite SAR system, and the proposed technical method has high engineering applicability. It has strong compatibility with existing systems and is convenient for implementing technology upgrades on existing platforms. Through the solution of the present invention, an existing SAR system can quickly introduce this technical solution to improve processing efficiency and data quality, and has significant practical value.

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

[0088] Figure 6 Schematically shows a block diagram of a distributed satellite synthetic aperture radar phase synchronization compensation device according to an embodiment of the present invention.

[0089] As Figure 6 shown, the distributed satellite synthetic aperture radar phase synchronization compensation device 600 according to this embodiment includes a synchronization data acquisition module 610, an unwrapping module 620, a damage judgment module 630, a wrapping 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 configured to extract the synchronization data of the master satellite and the slave satellite from the echo data of the master and slave satellites respectively in a distributed satellite SAR system, where the synchronization data includes head synchronization phase data, interpolation synchronization phase data, and tail synchronization phase data.

[0091] The unwrapping module 620 is configured to unwrap the synchronization data of the master satellite and the slave satellite.

[0092] The damage judgment module 630 is configured 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 interpolation synchronization phase data is not damaged.

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

[0095] The compensation phase generation module 660 is configured to generate a compensation phase according to the difference between the peak phases of the master satellite and the slave satellite and perform interpolation on the compensation phase.

[0096] The phase compensation module 670 is configured to perform point-by-point compensation on the echo data of the slave satellite by using the interpolated compensation phase.

[0097] It should be noted that the embodiments of the device part are correspondingly similar to those of the method part, and the achieved technical effects are also correspondingly similar. For specific details, please refer to the method embodiment part above and will not be elaborated here.

[0098] According to an embodiment of the present invention, any combination of the synchronization data acquisition module 610, the unwrapping module 620, the damage determination 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 integrated and implemented in one module, or any one of them can be split into multiple modules. Alternatively, at least part of the functions of one or more of these modules can be combined with at least part of the functions of other modules and implemented in one module. According to an embodiment of the present invention, at least one of the synchronization data acquisition module 610, the unwrapping module 620, the damage determination 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 hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on chip, a system on substrate, a system on package, an application specific integrated circuit (ASIC), or any other reasonable way of integrating or packaging circuits, etc., implemented by hardware or firmware, or implemented in any one of the three implementation manners of software, hardware, and firmware, or in an appropriate combination of any several of them. Alternatively, at least one of the synchronization data acquisition module 610, the unwrapping module 620, the damage determination 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 functions can be executed.

[0099] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the above-mentioned module, program segment, or 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 blocks may occur in a different order than that marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram or flowchart, and the combination of blocks in the block diagram or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

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

[0101] The above describes the 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 the various embodiments have been described separately above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Without departing from the scope of the present invention, those skilled in the art can make various substitutions and modifications, and all such substitutions and modifications should fall within the scope of the present invention.

Claims

1. A phase synchronization compensation method for distributed satellite synthetic aperture radar, characterized in that, including: In a distributed satellite SAR system, synchronizing data of the master satellite and the slave satellite are respectively extracted from the echo data of the master satellite and the slave satellite, wherein the synchronizing data includes initial synchronization phase data, interpolated synchronization phase data, and final synchronization phase data; unwrap the synchronizing data of the master satellite and the slave satellite; calculate gradient information of the unwrapped synchronizing data, and determine whether the interpolated synchronization phase data is damaged according to the gradient information; when it is determined that the interpolated synchronization phase data is not damaged, wrap the unwrapped synchronizing data; perform pulse compression on the wrapped synchronizing data, and extract the peak phase; generate a compensation phase according to the difference between the peak phases of the master satellite and the slave satellite, and interpolate the compensation phase; use the interpolated compensation phase to perform point-by-point compensation on the echo data of the slave satellite.

2. The method according to claim 1, wherein unwrap the synchronizing data of the master satellite and the slave satellite according to the following formula: Where n is the frame sequence of the phase synchronization pulse, and k is a natural number; is the n-th frame data of any one of the synchronization data of the head synchronization phase data, the interpolation synchronization phase data, and the tail synchronization phase data; is the n-th frame data of the synchronized data after phase unwrapping.

3. The method according to claim 1 or 2, characterized in that, The calculating the gradient information of the unwrapped synchronizing data and determining whether the interpolated synchronization phase data is damaged according to the gradient information includes: For any frame of data in the unwrapped interpolated synchronization phase data, calculate the phase difference between the next frame of data and this frame of data, and determine the gradient information corresponding to this frame of data according to the phase difference; count the positive and negative value ratios of multiple frames of the gradient information of the unwrapped interpolated synchronization phase data, and determine whether the interpolated synchronization phase data is damaged according to the positive and negative value ratios.

4. The method according to claim 3, wherein Determining whether the interpolated synchronization phase data is damaged according to the positive and negative value ratios includes: count the positive value ratio and the negative value ratio of multiple frames of the gradient information; judge whether the positive value ratio is greater than a preset ratio threshold or the negative value ratio is greater than the preset ratio threshold. If so, determine that the interpolated synchronization phase data is not damaged; otherwise, determine that the interpolated synchronization phase data is damaged.

5. The method according to claim 1, characterized in that, The method further includes: when it is determined that the interpolated synchronization phase data is damaged, estimate the joint slope of the unwrapped initial synchronization phase data and the final synchronization phase data; perform linear interpolation using the joint slope and the unwrapped initial synchronization phase data, and use the interpolated data to recover the damaged interpolated synchronization phase data, and return to the operation of wrapping the unwrapped synchronizing data.

6. The method according to claim 5, wherein Estimate the joint slope of the unwrapped initial synchronization phase data and the final synchronization phase data according to the following formula: Where N is the sum of the number of frames of the head synchronization phase data and the tail synchronization phase data, are the phase values of the head synchronization phase data and the tail synchronization phase data after phase unwrapping, is the frame sequence value corresponding to the phase value ; and are respectively and the mean values of, is the combined slope.

7. The method according to claim 6, characterized in that, Perform linear interpolation using the joint slope and the unwrapped initial synchronization phase data according to the following formula, and use the interpolated data to recover the interpolated synchronization phase data: where n is the number of sequences of inserted synchronous phase data; b is the intercept term, and its value is the phase value of the last frame of the first synchronous phase data after phase unwrapping, is the pulse repetition frequency of the inserted synchronous phase data, is the restored data of the nth frame of the inserted synchronous phase data after phase unwrapping.

8. The method according to claim 2, wherein Wrap the unwrapped synchronizing data according to the following formula: In the formula, represents taking the modulus of x with respect to y, is the nth frame data of the synchronized data after winding.

9. The method according to claim 1, wherein The generating a compensation phase according to the difference between the peak phases of the master satellite and the slave satellite and interpolating the compensation phase includes: take half of the difference obtained by subtracting the peak phase of the slave satellite from the peak phase of the master satellite as the compensation phase; interpolate the compensation phase according to the number of azimuth samples of the echo data of the slave satellite.

10. A distributed satellite synthetic aperture radar phase synchronization compensation device, characterized in that, including: a synchronization data acquisition module, configured to, in a distributed satellite SAR system, respectively extract synchronization data of the master satellite and the slave satellite from the echo data of the master satellite and the slave satellite, wherein the synchronization data includes initial synchronization phase data, interpolated synchronization phase data, and final synchronization phase data; The unwrapping module is used to unwrap the synchronization data of the primary satellite and the secondary satellite; The damage judgment module is used to calculate the gradient information of the unwrapped synchronization data and judge whether the inserted synchronization phase data is damaged according to the gradient information; The winding module is used to wind the unwrapped synchronization data when it is determined that the inserted synchronization phase data is not damaged; The pulse compression module is used to perform pulse compression on the wound synchronization data and extract the peak phase; The compensation phase generation module is used to generate a compensation phase according to the difference between the peak phases of the primary satellite and the secondary satellite and perform interpolation on the compensation phase; The phase compensation module is used to perform point-by-point compensation on the echo data of the secondary satellite by using the interpolated compensation phase.

Images