Staggered PRI mode spaceborne SAR echo signal reconstruction method and system

Abstract

The invention discloses a staggered PRI mode spaceborne SAR echo signal reconstruction method and system, and relates to the technical field of radar echo signal reconstruction, and the method comprises the steps: obtaining a first distance azimuth two-dimensional echo signal matrix, and enabling echo signals lost in the azimuth direction in any range gate in the first distance azimuth two-dimensional echo signal matrix to be discontinuous; recovering signals lost due to emission interference in the azimuth direction in each range gate in the first range azimuth two-dimensional echo signal matrix by using an interpolation method; and reconstructing a distance azimuth two-dimensional echo signal of azimuth equal-interval sampling by using an interpolation method. According to the method, the recovery signal with good continuity and high accuracy can be obtained, then the distance azimuth two-dimensional echo signal sampled at the azimuth equal interval is accurately reconstructed, and the method is small in data reconstruction calculation amount, high in reconstruction efficiency and high in reconstruction accuracy. Based on the method, wide SAR image reconstruction can be simple, efficient and accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of radar echo signal reconstruction, and in particular to a method and system for reconstructing an interleaved PRI mode spaceborne SAR echo signal. Background Art

[0002] Stagger PRI mode is a radar signal processing technology. Compared with the traditional spaceborne SAR (synthetic aperture radar) working mode, the continuous change of pulse transmission interval (StaggerPRI) can make the transmission interference area change continuously in the corresponding position in the scene, so that there will be no fixed blind area in the wide scene, so as to ensure the continuity and integrity of the wide scene observation. The azimuth echo sampling in this mode is no longer equal-interval sampling, but non-equal-interval sampling based on the pulse transmission interval change method, with a pulse transmission interval change period; on the other hand, at different azimuth sampling moments, the position of the range blind area is also different, resulting in the inability to image using the traditional spaceborne SAR imaging processing method based on uniform sampling.

[0003] Spaceborne synthetic aperture radar requires imaging processing based on radar echo signals, including data signal reconstruction. However, the existing processing efficiency and reconstruction accuracy of echo signals for Stagger PRI mode are low. Therefore, there is an urgent need to develop a method and system for reconstructing spaceborne SAR echo signals in staggered PRI mode. Summary of the invention

[0004] In view of the above problems, the present invention provides a method and system for reconstructing spaceborne SAR echo signals in an interleaved PRI mode.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0006] In a first aspect, the present invention provides a method for reconstructing an interleaved PRI mode spaceborne SAR echo signal, comprising:

[0007] Step 1, obtaining a first range-azimuth two-dimensional echo signal matrix, wherein the echo signal lost upward in any range gate in the first range-azimuth two-dimensional echo signal matrix is ​​discontinuous;

[0008] Step 2: Using an interpolation method, recover the signal lost in each range gate in the first range-azimuth two-dimensional echo signal matrix due to transmission interference in the azimuth upward direction;

[0009] Step 3: Use the interpolation method to reconstruct the range and azimuth two-dimensional echo signal sampled at equal intervals.

[0010] In a preferred embodiment, the first range-azimuth two-dimensional echo signal matrix is ​​specifically an echo signal of SAR transmitting pulses according to equidistant pulse transmission intervals.

[0011] In a preferred embodiment, the step 2 comprises:

[0012] Step 2.1, determine the location of the interference emitted by the spaceborne SAR;

[0013] Step 2.2, establishing the first Lagrangian interpolation kernel function according to the interference position of the spaceborne SAR;

[0014] Step 2.3, recovering the signal lost in the azimuth upward direction in each range gate in the first range-azimuth two-dimensional echo signal matrix due to the transmission interference to obtain a recovered signal;

[0015] Step 2.4, evaluate the continuity of the restored signal. If the continuity of all restored signals meets the first requirement, proceed to step 3. Otherwise, optimize the interpolation kernel of the first Lagrangian interpolation kernel function corresponding to the restored signal whose continuity does not meet the first requirement, and return to step 2.3.

[0016] In a preferred embodiment, the first requirement is that the real part and the imaginary part of the restored signal in the first range-azimuth two-dimensional echo signal matrix having the restored signal are both continuous.

[0017] In a preferred embodiment, the step 3 comprises:

[0018] Step 3.1, determine the sampling interval and sampling time of equally spaced azimuth sampling;

[0019] Step 3.2: Establish a second Lagrangian interpolation kernel function, and calculate the sampling signals at the sampling moments of equally spaced azimuth sampling according to the range-azimuth two-dimensional echo signal matrix restored in step 2.

[0020] Step 3.3: Determine the validity of the sampling signal. If the validity index requirement is met, the echo signal reconstruction is completed. Otherwise, return to step 3.1 or step 3.2.

[0021] In a preferred embodiment, the validity index requirements include that the spectrum amplitude characteristic meets the second requirement and / or the pulse compression result meets the third requirement.

[0022] In a second aspect, the present invention provides a staggered PRI mode spaceborne SAR echo signal reconstruction system, comprising:

[0023] An acquisition module, used for acquiring a first range-azimuth two-dimensional echo signal matrix, wherein the echo signal lost upward in any range gate in the first range-azimuth two-dimensional echo signal matrix is ​​discontinuous;

[0024] A first interpolation module, used for recovering the signal lost due to transmission interference in the azimuth upward direction in each range gate in the first range-azimuth two-dimensional echo signal matrix by using an interpolation method;

[0025] The second interpolation module is used to reconstruct the range and azimuth two-dimensional echo signals sampled at equal intervals by using an interpolation method.

[0026] In a third aspect, the present invention provides a method for reconstructing target imaging in an interleaved PRI mode SAR system, comprising: focusing the range-azimuth two-dimensional echo signal sampled at equal intervals in azimuth reconstructed in the first aspect to reconstruct the target imaging.

[0027] In a fourth aspect, the present invention provides an electronic device comprising: a memory; one or more processors; one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing an interleaved PRI mode spaceborne SAR echo signal reconstruction method according to the first aspect.

[0028] In a fifth aspect, the present invention provides a storage medium storing a computer program, characterized in that when the computer program is executed by a processor, the steps of a method for reconstructing an interleaved PRI mode spaceborne SAR echo signal described in the first aspect are implemented.

[0029] The interleaved PRI mode spaceborne SAR echo signal reconstruction method and system of the present invention interpolates the lost signal based on the discontinuous first range-azimuth two-dimensional echo signal matrix of the echo signal lost in azimuth within any range gate, so as to obtain a restored signal with good continuity and high accuracy. Based on the accurately restored and completed echo signal matrix, the interpolation method is used to reconstruct the range-azimuth two-dimensional echo signal sampled at equal intervals in azimuth, so that the reconstructed signal has high accuracy. Based on the method and system, the spaceborne SAR has a small amount of data reconstruction calculation, high reconstruction efficiency and high reconstruction accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a method for reconstructing echo signals of spaceborne SAR in interleaved PRI mode;

[0031] Figure 2 This is an example diagram of the two-dimensional echo signal matrix of the first range and azimuth in a method for reconstructing echo signals of spaceborne SAR in an interleaved PRI mode;

[0032] Figure 3 It is a specific flow chart of a method for reconstructing echo signals of spaceborne SAR in interleaved PRI mode;

[0033] Figure 4This is an example diagram of the second range and azimuth two-dimensional echo signal matrix in a staggered PRI mode spaceborne SAR echo signal reconstruction method;

[0034] Figure 5 This is an example diagram of a two-dimensional echo signal matrix of the third range and azimuth in a method for reconstructing echo signals of spaceborne SAR in an interleaved PRI mode;

[0035] Figure 6 This is a schematic diagram of the transmission interference characteristics of the target echo area in the StaggerPRI mode;

[0036] Figure 7 It is the first distance and azimuth two-dimensional echo signal diagram of the scene center point target in Stagger PRI mode;

[0037] Figure 8 is the azimuth a = Range echo data diagram at -0.2631s;

[0038] Fig. 9 The distance to R c = Azimuth echo data diagram at the position of 725.6km;

[0039] Fig.10 for Fig. 9 A partial map of

[0040] Fig.11 is the recovered direction t a = Schematic diagram of distance echo signal at the moment of -0.2631s;

[0041] Fig.12 is the recovered direction t a =Range echo signal spectrum at -0.2631s;

[0042] Fig.13 is the recovered azimuth t a =-0.2631s time range echo signal pulse pressure result (rectangular window);

[0043] Fig.14 is the recovered azimuth t a =-0.2631s time range echo signal pulse pressure result (Hamming window);

[0044] Fig.15 The distance to R c = The result of azimuth echo data recovery and equal-interval sampling at the position of 725.6km;

[0045] Fig.16 for Fig.15 A partial map of

[0046] Fig.17 To restore the spectrum amplitude characteristics of the azimuth signal sampled at equal intervals;

[0047] Fig.18 To recover the pulse compression result (rectangular window) of the azimuth signal sampled at equal intervals;

[0048] Fig.19 To recover the pulse compression result (Hamming window) of the azimuth signal sampled at equal intervals;

[0049] Fig. 20 This is a framework diagram of an interleaved PRI mode spaceborne SAR echo signal reconstruction system. DETAILED DESCRIPTION

[0050] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0052] It should be noted that the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application. The "and / or" mentioned in the present invention refers to any and all combinations of one or more of the relevant listed items.

[0053] The present invention provides a method for reconstructing an interleaved PRI mode spaceborne SAR echo signal, comprising the following steps:

[0054] Step 1, obtaining a first range-azimuth two-dimensional echo signal matrix, wherein the echo signal lost upward in azimuth within any range gate in the first range-azimuth two-dimensional echo signal matrix is ​​discontinuous;

[0055] Step 2: In the first range-azimuth two-dimensional echo signal matrix, an interpolation method is used to recover the signal lost in the azimuth direction in each range gate in the first range-azimuth two-dimensional echo signal matrix due to transmission interference (called the azimuth direction signal), and a recovered signal is obtained, that is, a first range-azimuth two-dimensional echo signal matrix with a recovered signal is obtained, which is called the second range-azimuth two-dimensional echo signal matrix;

[0056] Step 3: Based on the first range-azimuth two-dimensional echo signal matrix with restored signals, an interpolation method is used to reconstruct the range-azimuth two-dimensional echo signal sampled at equal intervals in azimuth, so as to obtain a third range-azimuth two-dimensional echo signal matrix.

[0057] like Figure 2 As shown, it is an example of the range-azimuth two-dimensional echo signal matrix obtained in the step 1, wherein the red area represents the lost echo signal, and the black circles in other areas represent the collected echo signals. It can be seen that the first range-azimuth two-dimensional echo signal matrix formed by the black circles is a two-dimensional echo signal with non-uniform intervals in the azimuth direction and missing in the range direction.

[0058] The method of this embodiment is based on the spaceborne SAR in the staggered PRI mode. The SAR changes the pulse transmission interval according to a variable pulse transmission interval sequence. One variable pulse transmission interval sequence serves as a pulse transmission interval change cycle.

[0059] In this embodiment, the first range-azimuth two-dimensional echo signal matrix is ​​the echo signal corresponding to the pulses transmitted by the SAR in accordance with an increasing or decreasing variable pulse transmission interval sequence. Specifically, the variable pulse transmission interval sequence is an arithmetic progression.

[0060] In this embodiment, within any range gate, two or more azimuth sampling signals will not be lost continuously, that is, in the azimuth direction, the lost sampling signals are discontinuous, and there are several non-lost sampling signals as intervals between two lost sampling signals.

[0061] The design method of the variable pulse transmission interval sequence is:

[0062] S1. Obtaining the system parameters of the spaceborne wide-band SAR in the interleaved PRI mode;

[0063] S2. Design a variable pulse emission interval sequence, wherein the variable pulse emission interval sequence is an arithmetic progression, including: S2.1. Determine the pulse emission interval starting value PRI1, S2.2. Determine the pulse emission interval change Δ between adjacent pulse emission intervals PRI , S2.3, determine the sequence length M;

[0064] S3, determine whether all pulse emission intervals in the variable pulse emission interval sequence are in

[0065] [PRI min ,PRI max ] within the scope of the PRI min Indicates the minimum value of the variable pulse transmission interval, PRI max Indicates the maximum value of the variable pulse transmission interval; if not, return to S2.1 or return to S2.3, if so, proceed to S4;

[0066] S4. Determine whether transmitting pulses according to the variable pulse transmission interval sequence can ensure that the azimuth echo signal within any range gate of the wide-band SAR scene will not be lost continuously. If so, the design is completed; if not, return to S2.1 or return to S2.2.

[0067] After the variable pulse transmission interval sequence is designed, the spaceborne SAR transmits pulses according to the variable pulse transmission interval sequence and receives echo signals at the same time. It can be understood that the echo signals described herein are sampling signals.

[0068] For each range gate signal, the operation of recovering the lost signal and reconstructing the signal sampled at equal intervals in azimuth is performed. For the specific process of the method of the present invention, see Figure 3 .

[0069] In this embodiment, in step 2, interpolation processing is performed according to the interference periodicity characteristics caused by the periodicity of the transmission pulse interval change to effectively restore the signal lost due to the transmission interference. The specific implementation steps are as follows:

[0070] Step 2.1: Determine the position where the azimuth sampling signal is lost in each complete pulse transmission interval variation cycle of the staggered PRI mode. The position where the azimuth sampling signal is lost corresponds to the moment of SAR transmission interference.

[0071] The pulse transmission interval variation cycle is set to M, that is, the variable pulse transmission interval sequence has a total of M items. Therefore, for the echo signal, within any range gate, its blind zone interference position is also periodic. For example, the azimuth position where the echo signal is lost within one cycle in azimuth is (p1, p2, …, p N ), where N is the number of signal losses within a pulse transmission interval variation cycle, then the interference position within a certain cycle is

[0072] P int =(p1,p2,…,p N )+N×n' (1)

[0073] Wherein, n' is an integer greater than or equal to 1, and is used to represent the n'th pulse emission interval variation period.

[0074] Step 2.2: According to the interference position of the spaceborne SAR, a Lagrangian interpolation kernel function is established, which is referred to as the first Lagrangian interpolation kernel function.

[0075] Step 2.3, based on the first Lagrangian interpolation kernel function and the first range-azimuth two-dimensional echo signal matrix, restore the signal lost in each range gate in the first range-azimuth two-dimensional echo signal matrix due to transmission interference in the azimuth direction to obtain a restored signal, and obtain a second range-azimuth two-dimensional echo signal matrix.

[0076] Since the transmission interference position presents a periodic characteristic, N interpolation kernel functions can be established to restore the signal value at the transmission interference position using the first range-azimuth two-dimensional echo signal matrix.

[0077] Suppose the azimuth time corresponding to a certain transmission interference is t int , the interpolation kernel length of the first Lagrangian interpolation kernel function is N p , then in the sampling signal obtained in the first range-azimuth two-dimensional echo signal matrix azimuth, according to the time t int Sort the intervals from small to large and pick out N p The sampling signals are usually selected in sequence according to the degree of proximity. The sampling times corresponding to these sampling signals are

[0078] t=[t(1),t(2),…,t(N p )] (2)

[0079] The corresponding sampling signal is

[0080] SIG=[sig(1),sig(2),…,sig(N p )] (3)

[0081] According to the sampling time, construct the Lagrange interpolation matrix LAG, which is an N p ×N p A matrix whose elements are defined as

[0082]

[0083] Among them, ii represents the row of the matrix and jj represents the column of the matrix.

[0084] From the LAG matrix, the Lagrange interpolation kernel function can be obtained as

[0085] Lag=prod(LAG) (5)

[0086] The interpolation kernel function is a 1×N p The vector of t can be recovered according to SIG and Lag int The signal value lost due to transmission interference at this moment is

[0087] sig(t int )=SIG·Lag (6)

[0088] It is the scalar product of SIG and Lag.

[0089] Similarly, by using the above method to establish the corresponding first Lagrangian interpolation kernel function for the other N-1 pulse loss moments, all the lost signals in the single pulse emission interval variation period can be restored.

[0090] Because each spaceborne SAR transmission interference position in a pulse transmission interval variation cycle has a corresponding first Lagrangian interpolation kernel function, in other pulse transmission interval sequence cycles, the signal lost due to transmission interference is calculated and the continuity is evaluated based on the N first Lagrangian interpolation kernel functions that have been obtained.

[0091] Step 2.4: Evaluate the continuity of the restored signal, that is, evaluate the first range-azimuth two-dimensional echo signal matrix with the restored signal.

[0092] To ensure the validity of the signal recovered by the above interpolation method, the continuity of the azimuth sampling signal within the range gate is evaluated to see whether it meets the first requirement. The first requirement is: the real and imaginary parts of the recovered signal are both continuous. That is, the real and imaginary parts of the second range-azimuth two-dimensional echo signal matrix at the recovered signal point are both continuous, and no jumping zero values ​​appear. If the first requirement is met, the recovered lost signal is considered valid. If all the recovered signals are continuous, proceed to step 3; if there are still some incoherent recovered signals, it is necessary to optimize the interpolation kernel for the corresponding first Lagrangian interpolation kernel function, including the interpolation kernel length and precision, and return to step 2.3 to recover the lost signal and evaluate again to ensure that the finally recovered signal is continuous and valid.

[0093] like Figure 4 As shown, a second range-azimuth two-dimensional echo signal matrix is ​​shown. Figure 4 The red circle in the middle shows the signal lost in azimuth restored by interpolation of each range gate, and the black circle represents the echo signal in the first range-azimuth two-dimensional echo signal matrix obtained in step 1.

[0094] After using step 2 to supplement the azimuth sampling loss of each range gate caused by transmission interference and solving the problem of missing range upward, the next step is to perform step 3 to convert it into an azimuth equally spaced sampling signal.

[0095] Step 3: Determine the sampling interval of equally spaced azimuth sampling, and determine the sampling time according to the sampling interval. Perform interpolation processing according to the result of step 2 to effectively determine the equally spaced sampling signal in azimuth, and then obtain the range and azimuth two-dimensional echo signal, which is called the third range and azimuth two-dimensional echo signal or the azimuth equally spaced data matrix.

[0096] Step 3.1: Determine the equally spaced azimuth sampling times t uni .

[0097] In order to establish an equally spaced sampling distribution, we first need to determine the azimuth sampling interval dt for reconstructing the range-azimuth two-dimensional echo signal matrix. a According to the original StaggerPRI pulse emission interval, the duration of a complete pulse emission interval change cycle is:

[0098]

[0099] Among them, PRI m It represents the mth pulse emission interval in the pulse emission interval variation cycle. There are a total of M pulse emission intervals in the pulse emission interval variation cycle, that is, M sampling signals are actually emitted in one pulse emission interval variation cycle.

[0100] Assume that M1 sampling signals are emitted at equal time intervals in one cycle, and the sampling interval of these M1 sampling signals is

[0101]

[0102] In order to ensure that the signal is sufficiently sampled and there is no information redundancy, the constraints that M1 needs to meet are:

[0103] α·T s_pri ·B dop ≤M1≤M (9)

[0104] Among them, α is the azimuth oversampling factor, B dop is the instantaneous Doppler frequency of the echo signal in azimuth.

[0105] In order to ensure that the azimuth sampling signals in each cycle are coherent and equally spaced, the azimuth sampling time of the third range azimuth two-dimensional echo signal matrix can be defined as

[0106] t uni (n) = t(1) + dt a / 2+(n-1)·dt a (10)

[0107] Among them, t uni (n) is the nth equally spaced sampling moment, t(1) is the first sampling moment in the azimuth direction in the staggered PRI mode, that is, this moment is the first sampling moment of equally spaced sampling, dt a is the azimuth sampling interval for reconstructing a data matrix with equal spacing in azimuth.

[0108] Here, it is necessary not only to consider that the intervals between adjacent cycles also satisfy equal intervals, but also to consider whether M1 sampling signals can be emitted at equal time intervals in other cycles except the first cycle.

[0109] Step 3.2: Design M1 Lagrangian interpolation kernels to reconstruct the equally spaced sampling signals in azimuth.

[0110] Based on the second distance-azimuth two-dimensional echo signal matrix of the recovered sampling values ​​at the transmission interference position obtained in step 2, combined with the azimuth equally spaced sampling time t given in step 3.1 uni (n), using a method similar to step 2.2, establish its M1 Lagrangian interpolation kernels, and use the second Lagrangian interpolation kernel function to restore the signal value sig(t uni ).

[0111] Specifically, if the length of the interpolation kernel function is N p , then in the signal obtained in step 2, sort N according to the interval from the time tuni(n) from small to large p signals, and the sampling times corresponding to these signals are

[0112] t=[t(1),t(2),…,t(N p )] (2)

[0113] The corresponding signal is

[0114] SIG=[sig(1),sig(2),…,sig(N p )] (3)

[0115] According to the sampling time, construct the Lagrange interpolation matrix LAG, which is an N p ×N p A matrix whose elements are defined as

[0116]

[0117] Among them, ii represents the row of the matrix and jj represents the column of the matrix.

[0118] From the LAG matrix, the Lagrange interpolation kernel function can be obtained as

[0119] Lag=prod(LAG) (5)

[0120] The interpolation kernel function is a 1×N p The vector of t can be recovered according to SIG and Lag int The signal value lost due to transmission interference at this moment is

[0121] sig(t int )=SIG·Lag (6)

[0122] It is the scalar product of SIG and Lag.

[0123] Step 3.3: Determine whether the validity of the sampling signal at the sampling moment of equally spaced azimuth sampling (azimuth equally spaced sampling signal) meets the validity index requirements. If so, the echo signal reconstruction is completed. Otherwise, return to step 3.1 to re-determine the sampling interval and sampling moment of equally spaced azimuth sampling or return to step 3.2 to re-establish the second Lagrangian interpolation kernel function and recalculate the sampling signal at the sampling moment of equally spaced azimuth sampling.

[0124] In order to evaluate the effectiveness of the azimuth equally spaced sampling signal obtained by the above method, the azimuth signal can be evaluated by signal spectrum analysis and performance index evaluation after pulse compression. If the result finally achieved by this embodiment meets the effectiveness index requirements, the method of this embodiment is considered effective; otherwise, it is necessary to further optimize the azimuth sampling interval, interpolation kernel function, etc., return to step 3.1 or return to step 3.2 to finally ensure that the index meets the requirements.

[0125] The validity index requirements described in this embodiment include but are not limited to the spectrum amplitude characteristic meeting the second requirement and / or the pulse compression result meeting the third requirement.

[0126] An example of the third range-azimuth two-dimensional echo signal matrix obtained in step 3 can be found in Figure 5 .

[0127] The following introduces a specific application example of the present invention, taking a StaggerPRI spaceborne SAR system as an example to illustrate the effectiveness of the present invention in reconstructing the echo matrix obtained by varying the pulse transmission interval.

[0128] Table 1 gives the operating parameters of the StaggerPRI mode spaceborne SAR system. The satellite flight orbit altitude is 600 km and the system carrier frequency is 9.8 GHz.

[0129] Table 1

[0130] project Parameter Value Satellite orbit altitude 600km System carrier frequency 9.8GHz Transmit pulse width 20μs Transmit bandwidth 20MHz Data sampling rate 40MHz Antenna azimuth beamwidth 0.35° Observation scene near-end perspective 30° Observation scene near ground distance 352.21km Observation scene near-end slant distance 704.06km Observe the scene from a distance 35° Observation scene far distance 430.64km Slant distance at the far end of the observation scene 750.23km Range mapping width 75km Azimuth survey length 75km Pulse emission interval variation cycle 50 Start pulse transmission interval 1 / 6000s Pulse emission interval variation 1.129μs

[0131] Under the parameters in Table 1 above, we first analyze the echo interference and reconstruction recovery of a single point target. Figure 6 The transmission interference characteristics in StaggerPRI mode are given. Since the pulse transmission interval changes in period M = 50, the transmission interference is also periodic. It can be seen that the signal sampling characteristics of the 1st to 50th sampling points and the 51st to 100th sampling points in the azimuth direction are the same.

[0132] See also Figure 7, gives the two-dimensional echo of the scene center point target in StaggerPRI mode. From the distribution of the echo, its azimuth time range is -0.3s to 0.3s, and the upward slant range spans 724.1km to 727.1km.

[0133] exist Figure 7 A row of range echo data and a column of azimuth echo data are extracted from the echo data for analysis. Figure 8 and Fig. 9 The position and time t are given respectively a =-0.2631s range echo data and slant range R c = azimuth echo data at the position of 725.6km, Fig.10 for Fig. 9 A magnified view of a certain area. Figure 8 It can be seen that most of the range echo data is lost due to transmission interference; Fig. 9 and Fig.10 It can be seen that the azimuth echo data is lost intermittently.

[0134] Through the echo signal reconstruction method provided by the present invention, the restored t a = The distance echo signal at the moment of -0.2631s is as follows Fig.11 Its spectrum is shown as Fig.12 As shown in the figure, it can be seen that the signal has been completely restored and the spectrum is smooth. The corresponding signal bandwidth is B = 20MHz, which is consistent with the signal transmission bandwidth, indicating that the signal has been effectively restored. Pulse compression uses rectangular window and Hamming window respectively. The results are shown in Fig.13 and 14 As shown in the figure, the performance indicators of pulse compression processing after windowing are shown in Table 2. The indicator results are ideal and meet the corresponding technical requirements.

[0135] Table 2

[0136] Main lobe aspect ratio Peak-to-sidelobe ratio Integrated sidelobe ratio Rectangular window 0.9876 -13.2398dB -9.6928dB Hamming Window 1.4814 -41.8477dB -28.9979dB

[0137] Fig.15 The figure shows the results of azimuth echo data recovery and equal-interval sampling. Fig.16 for Fig.15 A partial enlarged schematic diagram of Fig.17 for Fig.15 Schematic diagram of the spectrum amplitude characteristics, and the pulse compression characteristics under the two window functions can be found in Fig.18 and Fig.19 The performance indexes of pulse compression processing after windowing are shown in Table 3. It can be seen from these results that the reconstruction method of the present invention still achieves an ideal effect in azimuth.

[0138] Table 3

[0139] Main lobe aspect ratio Peak-to-sidelobe ratio Integrated sidelobe ratio Rectangular window 0.9480 -13.4444dB -9.6467dB Hamming Window 1.2992 -35.1960dB -28.9469dB

[0140] The present invention provides a staggered PRI mode spaceborne SAR echo signal reconstruction system, see Fig. 20 , the system includes:

[0141] The obtaining module 10 is used to obtain a first range-azimuth two-dimensional echo signal matrix, wherein the echo signal lost upward in any range gate in the first range-azimuth two-dimensional echo signal matrix is ​​discontinuous;

[0142] A first interpolation module 20 is used to recover the signal lost in each range gate in the first range-azimuth two-dimensional echo signal matrix due to transmission interference in the azimuth upward direction by using an interpolation method;

[0143] The second interpolation module 30 is used to reconstruct the range and azimuth two-dimensional echo signals sampled at equal intervals in azimuth by using an interpolation method.

[0144] The first interpolation module 20 comprises:

[0145] A location determination unit, used to determine the location of interference emitted by the spaceborne SAR;

[0146] The first function establishment unit is used to establish a first Lagrangian interpolation kernel function according to the spaceborne SAR transmission interference position; and is used to optimize the interpolation kernel of the first Lagrangian interpolation kernel function corresponding to the restored signal whose continuity does not meet the first requirement;

[0147] The first calculation unit is used to recover the signal lost in the azimuth direction in each range gate in the first range-azimuth two-dimensional echo signal matrix due to transmission interference to obtain a recovered signal; the first evaluation unit is used to evaluate whether the continuity of the recovered signal meets the first requirement.

[0148] The second interpolation module 30 includes:

[0149] A second determining unit is used to determine the sampling interval and sampling time of equally spaced azimuth sampling;

[0150] The second function calculation unit is used to establish a second Lagrangian interpolation kernel function, and calculate the sampling signals at the sampling time of equally spaced azimuth sampling according to the restored two-dimensional echo signal matrix of range and azimuth;

[0151] A first judging unit, used to judge whether the sampling signal meets the validity index requirement;

[0152] The second determination unit is further used to re-determine the sampling interval and sampling time of the equally spaced azimuth sampling when the first determination unit determines that the sampling signal does not meet the validity index requirement;

[0153] The second function calculation unit is also used to re-determine the establishment of a second Lagrangian interpolation kernel function and recalculate the sampling signals of the sampling time of equally spaced azimuth sampling based on the restored two-dimensional echo signal matrix of range and azimuth when the first judgment unit determines that the sampling signal does not meet the validity index requirements.

[0154] When the interleaved PRI mode spaceborne SAR echo signal reconstruction system is implemented, the interleaved PRI mode spaceborne SAR echo signal reconstruction method in any of the above embodiments may be referred to to implement echo signal reconstruction, and the specific implementation steps will not be repeated herein.

[0155] The present invention provides a target imaging reconstruction method under an interleaved PRI mode SAR system, comprising:

[0156] The reconstructed two-dimensional echo signals of the range and azimuth with equal interval sampling are obtained, focused, and the target imaging is reconstructed.

[0157] According to the method of the present invention, an electronic device can be implemented, and the electronic device includes: a memory; one or more processors; one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing an interlaced PRI mode spaceborne SAR echo signal reconstruction method according to any of the above embodiments.

[0158] The present invention also provides a computer-readable storage medium, which includes instructions. When the instructions are executed on a computer, the computer executes each step of the interleaved PRI mode spaceborne SAR echo signal reconstruction method described in any of the above embodiments.

[0159] The effects of the interleaved PRI mode spaceborne SAR echo signal reconstruction method and system of the present invention are as follows: the present invention interpolates the lost signal based on the discontinuous first range-azimuth two-dimensional echo signal matrix of the echo signal lost in azimuth within any range gate, and can obtain a restored signal with good continuity and high accuracy; based on the accurately restored and completed echo signal matrix, an interpolation method is used to reconstruct the range-azimuth two-dimensional echo signal sampled at equal intervals in azimuth, so that the reconstructed signal has high accuracy; based on the method and system, the spaceborne SAR has a small amount of data reconstruction calculation, high reconstruction efficiency and high reconstruction accuracy.

[0160] On this basis, the traditional imaging algorithm can be used to process the reconstructed two-dimensional echo signals of range and azimuth with equal intervals of sampling, so as to finally obtain a complete wide-width SAR image. The interlaced PRI mode spaceborne SAR echo signal reconstruction method based on the present invention makes the reconstruction of wide-width SAR images simple, efficient and accurate.

[0161] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0162] Those skilled in the art will appreciate that the present invention may be implemented in the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may be implemented in the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0163] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concept is known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for reconstructing spaceborne SAR echo signals in interleaved PRI mode, characterized in that: include: Step 1, obtaining a first range-azimuth two-dimensional echo signal matrix, wherein the echo signal lost upward in any range gate in the first range-azimuth two-dimensional echo signal matrix is ​​discontinuous; Step 2: Using an interpolation method, recover the signal lost in each range gate in the first range-azimuth two-dimensional echo signal matrix due to transmission interference in the azimuth upward direction; Step 3: Use the interpolation method to reconstruct the range and azimuth two-dimensional echo signal sampled at equal intervals.

2. The method for reconstructing the echo signal of spaceborne SAR in interleaved PRI mode according to claim 1, characterized in that: The first range-azimuth two-dimensional echo signal matrix is ​​specifically an echo signal of a SAR transmitting pulse according to an equidistant pulse transmitting interval.

3. The method for reconstructing spaceborne SAR echo signals in interleaved PRI mode as claimed in claim 1, characterized in that: The step 2 comprises: Step 2.1, determine the location of the interference emitted by the spaceborne SAR; Step 2.2, establishing the first Lagrangian interpolation kernel function according to the interference position of the spaceborne SAR; Step 2.3, recovering the signal lost in the azimuth upward direction in each range gate in the first range-azimuth two-dimensional echo signal matrix due to the transmission interference to obtain a recovered signal; Step 2.4, evaluate the continuity of the restored signal. If the continuity of all restored signals meets the first requirement, proceed to step 3. Otherwise, optimize the interpolation kernel of the first Lagrangian interpolation kernel function corresponding to the restored signal whose continuity does not meet the first requirement, and return to step 2.

3.

4. The method for reconstructing the echo signal of spaceborne SAR in interleaved PRI mode as claimed in claim 3, characterized in that: The first requirement is that the real part and the imaginary part of the restored signal in the first range-azimuth two-dimensional echo signal matrix having the restored signal are both continuous.

5. The method for reconstructing spaceborne SAR echo signals in interleaved PRI mode as claimed in claim 1, characterized in that: The step 3 comprises: Step 3.1, determine the sampling interval and sampling time of equally spaced azimuth sampling; Step 3.2: Establish a second Lagrangian interpolation kernel function, and calculate the sampling signals at the sampling moments of equally spaced azimuth sampling according to the range-azimuth two-dimensional echo signal matrix restored in step 2. Step 3.3: Determine the validity of the sampling signal. If the validity index requirement is met, the echo signal reconstruction is completed. Otherwise, return to step 3.1 or step 3.

2.

6. The method for reconstructing the echo signal of spaceborne SAR in interleaved PRI mode as claimed in claim 5, characterized in that: The effectiveness index requirements include that the spectrum amplitude characteristic meets the second requirement and / or the pulse compression result meets the third requirement.

7. An interleaved PRI mode spaceborne SAR echo signal reconstruction system, characterized in that: include: An acquisition module, used for acquiring a first range-azimuth two-dimensional echo signal matrix, wherein the echo signal lost upward in any range gate in the first range-azimuth two-dimensional echo signal matrix is ​​discontinuous; A first interpolation module, used for recovering the signal lost due to transmission interference in the azimuth upward direction in each range gate in the first range-azimuth two-dimensional echo signal matrix by using an interpolation method; The second interpolation module is used to reconstruct the range and azimuth two-dimensional echo signals sampled at equal intervals by using an interpolation method.

8. A target imaging reconstruction method in an interleaved PRI mode SAR system, characterized in that: include: The two-dimensional echo signals in range and azimuth reconstructed with equal interval sampling in azimuth according to any one of claims 1-6 are focused to reconstruct the target imaging.

9. An electronic device, characterized in that: include: Memory; one or more processors; One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for executing any method in the interleaved PRI mode spaceborne SAR echo signal reconstruction method according to claims 1-6.

10. A storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of a method for reconstructing an interleaved PRI mode spaceborne SAR echo signal as described in any one of claims 1 to 6 are implemented.

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