Method for recovering phase correlation of dechirp echo based on radar gate hopping prior

Abstract

The application discloses a method for recovering the phase correlation of despread echoes based on radar gate hopping priori, which comprises the following steps: obtaining despread radar echo data; processing the despread radar echo data to obtain echo envelope, estimating the position change of the echo envelope corresponding to adjacent pulses through the maximum position of the result of correlation processing, obtaining vector P0, then performing hopping compensation to obtain smooth target position change, performing difference processing on the smooth target position change to obtain the estimation of target radial velocity, and constructing a high-speed compensation function; multiplying the high-speed compensation function with the despread radar echo data to obtain first compensation data; performing residual video term compensation on the first compensation data, then performing hopping compensation to obtain data after the compensation of the gate hopping node, then performing two-dimensional fast Fourier transform to obtain target Doppler spectrum, performing unified compensation on the target Doppler spectrum, and then performing distance direction and azimuth direction Fourier transform to obtain a radar image. The application can improve the final ISAR focusing quality.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing technology, specifically relating to a method for deslanting echo coherence recovery based on radar gate jump prior. Background Technology

[0002] Inverse-Synthetic-Aperture-Radar (ISAR) is widely used in airborne and aerospace target observation due to its all-weather, all-day, high-resolution, and long-range capabilities. Acquiring radar signals in ISAR imaging involves various methods, including de-sampling, direct sampling, and stepped sampling. De-sampling reduces signal bandwidth and sampling rate. It involves multiplying the received echo with the transmitted signal after a certain time delay, typically determined by a reference distance. This reference distance remains constant for a certain period but changes abruptly after the target deviates from the reference distance. Adjusting the reference distance at this point ensures complete reception of the echo. Furthermore, the sampling gate, also determined by the reference distance, is used to acquire the target echo at the correct time. This abrupt change in reference distance leads to abrupt changes in the pulse compression envelope and phase of the received echo, severely compromising the coherence of the radar signal.

[0003] In related technologies, common methods for restoring radar coherence include envelope alignment and phase autofocus. Envelope alignment utilizes the similarity between adjacent echoes, determining the envelope's shift position by maximizing the correlation function, thus restoring envelope coherence. Phase autofocus leverages the property that different scattering points have the same error phase. It extracts the error phase difference by performing conjugate multiplication on adjacent pulses and weighted summation on different range cells. Finally, it integrates the extracted phase to obtain the error phase, and constructs a compensation function based on the estimated error phase to improve the phase coherence of the echo data. Existing methods process the envelope and phase separately, thus failing to accurately restore the echo data's coherence, affecting the accuracy of parameter estimation and precise focusing during imaging.

[0004] Therefore, it is urgent to improve the aforementioned defects in the existing technology. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a method for deslanting echo coherence recovery based on radar gate transition priors. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for deslanting echo coherence recovery based on radar gate transition prior, comprising:

[0007] Acquire deslant radar echo data;

[0008] Perform range-direction fast Fourier transform on the deslant radar echo data to obtain the echo envelope;

[0009] The echo envelopes corresponding to adjacent pulses are correlated to obtain the correlation results. The positional change of the echo envelopes corresponding to adjacent pulses is estimated by the maximum position of the correlation results to obtain vector P0.

[0010] The vector P0 is unwound to obtain the unwound target position P3. Based on the unwound target position, the reference distance change and the smoothed target position change are obtained. The smoothed target position change is differentially processed to obtain the estimate of the target radial velocity.

[0011] Based on the estimate of the target radial velocity, a high-speed compensation function is constructed;

[0012] The high-speed compensation function is multiplied with the deslant radar echo data to obtain the first compensation data;

[0013] The first compensation data is processed by distance-to-Fourier transform, and then the remaining video items are compensated to obtain the data after the remaining video items are compensated.

[0014] The data after compensation of the remaining video terms are processed by inverse Fourier transform in the range direction. Based on the reference range change, the smooth target position change, and the target radial velocity estimation, a jump compensation function is constructed. The jump compensation function is then multiplied with the data after compensation of the remaining video terms to perform jump compensation, resulting in data after gate jump node compensation and dynamic coarseness compensation.

[0015] Two-dimensional fast Fourier transform is performed on the data after compensation for the gate jump node and the translational coarse compensation to obtain the target Doppler spectrum. The noise regions at both ends of the target Doppler spectrum are discarded, and then an inverse fast Fourier transform is performed in the azimuth direction to obtain the Doppler filtered data.

[0016] The Doppler-filtered data is uniformly compensated, and then Fourier transforms are performed in the range and azimuth directions to obtain the inverse synthetic aperture radar image of the target focus.

[0017] The beneficial effects of this invention are:

[0018] This invention provides a method for restoring the coherence of deslanted echoes based on radar gate jump priors. On the one hand, it fully utilizes the radar's prior information, enabling precise estimation of the jump reference range and gate using envelope position changes estimated by envelope alignment. This information is then used to accurately restore the echo coherence by directly constructing a compensation function, significantly enhancing both the accuracy of coherence restoration and noise resistance. On the other hand, it considers the modulation of the deslanted echoes by high-speed target motion, deriving an accurate deslanted echo expression. The echoes are compensated by directly constructing an accurate compensation function, resulting in high processing efficiency and motion compensation accuracy, which is beneficial for improving the final ISAR focusing quality.

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a flowchart of a method for deslanting echo coherence recovery based on radar gate jump prior provided in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the relative positions of target scattering points in a simulation experiment provided in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of a target distance variation curve provided in an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of a target velocity change curve provided in an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the target deslant echo distance pulse compression result provided in an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the distance envelope slice of the last pulse processed by the method provided by the present invention and conventional methods, as provided in an embodiment of the present invention;

[0026] Figure 7 This is a schematic diagram of the pulse compression envelope after translational compensation of the deslant echo using the method of the present invention, provided in an embodiment of the present invention.

[0027] Figure 8(a) is a schematic diagram of an ideal ISAR imaging result provided by an embodiment of the present invention;

[0028] Figure 8(b) is a schematic diagram of the ISAR imaging results provided by the method in the embodiment of the present invention;

[0029] Figure 9(a) is a schematic diagram of the contour map of point 1 under ideal conditions provided by an embodiment of the present invention;

[0030] Figure 9(b) is a schematic diagram of the contour map of the method marking point 1 provided in the embodiment of the present invention;

[0031] Figure 9(c) is a schematic diagram of a distance slice of marker point 1 provided in an embodiment of the present invention;

[0032] Figure 9(d) is a schematic diagram of the orientation slice of marker point 1 provided in an embodiment of the present invention;

[0033] Figure 10(a) is a schematic diagram of the contour map of point 2 under ideal conditions provided by an embodiment of the present invention;

[0034] Figure 10(b) is a schematic diagram of the contour plot of the method marking point 2 provided in the embodiment of the present invention;

[0035] Figure 10(c) is a schematic diagram of a distance slice of marker point 2 provided in an embodiment of the present invention;

[0036] Figure 10(d) is a schematic diagram of the orientation slice of marker point 2 provided in an embodiment of the present invention;

[0037] Figure 11(a) is a schematic diagram of the contour map of point 3 under ideal conditions provided by an embodiment of the present invention;

[0038] Figure 11(b) is a schematic diagram of the contour plot of the method marking point 3 provided in the embodiment of the present invention;

[0039] Figure 11(c) is a schematic diagram of a distance slice of marker point 3 provided in an embodiment of the present invention;

[0040] Figure 11(d) is a schematic diagram of the orientation slice of marker point 3 provided in an embodiment of the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0042] In the existing technology, firstly, the signal-to-noise ratio requirement of the echo signal is high, and it is easily affected by noise; secondly, the existing technology processes the envelope and phase separately, ignoring the coupling between them; and thirdly, the existing technology does not accurately consider the intra-pulse Doppler modulation of the deslant echo by high-speed motion.

[0043] In view of this, the present invention provides a coherent recovery method for deslant echoes based on radar gate transition priors. First, by utilizing the prior information that the smallest unit of gate transition in an actual radar system is fixed, and combining it with the envelope transition position estimated by envelope alignment, the influence of noise on envelope transition estimation and compensation can be greatly reduced. Second, by considering the intra-pulse Doppler modulation caused by the high-speed motion of the target on the deslant echo, an accurate expression for radar deslant echo is derived. By directly constructing a high-speed motion compensation function, the intra-pulse Doppler modulation caused by the high-speed motion of the target is compensated. By directly constructing an envelope phase coupling compensation function, unified compensation of envelope and phase is achieved, thereby improving the compensation accuracy.

[0044] Please see Figure 1 As shown, Figure 1 This is a flowchart of a deslant echo coherence recovery method based on radar gate transition prior provided by an embodiment of the present invention. The deslant echo coherence recovery method based on radar gate transition prior provided by the present invention includes:

[0045] S101, Acquire deslant radar echo data.

[0046] Specifically, in this embodiment, the process of acquiring deslant radar echo data includes:

[0047] S1011: After the inverse synthetic aperture radar transmits a linear frequency modulated signal to a high-speed moving target, it acquires the echo signal of the transmitted linear frequency modulated signal.

[0048] S1012. Multiply the echo signal with the preset radar deskewing reference signal by conjugate to obtain the deskewing radar echo data, and sample and record the deskewing echo data.

[0049] S102. Perform range-direction fast Fourier transform on the deslant radar echo data to obtain the echo envelope.

[0050] S103. Perform correlation processing on the echo envelopes corresponding to adjacent pulses to obtain the correlation results. Estimate the position change of the echo envelopes corresponding to adjacent pulses based on the maximum position of the correlation results to obtain vector P0.

[0051] S104. Unwrap vector P0 to obtain the unwrap target position P3. Based on the unwrap target position, obtain the reference distance change and the smooth target position change. Perform differential processing on the smooth target position change to obtain the estimate of the target radial velocity.

[0052] Specifically, in this embodiment, the above process includes:

[0053] S1041. Perform a difference operation on vector P0 to obtain vector P1;

[0054] S1042. Calculate the maximum value A of vector P1;

[0055] S1043. Obtain the position P2 of the element in vector P1 whose absolute value is greater than a preset threshold; where the preset threshold T0 = 0.75A;

[0056] S1044. Subtract the preset minimum jump gate Rq from the value at position P2+1 in vector P0 to obtain the target position P3 for unwinding.

[0057] Specifically, iterate through the element values ​​in P2. For each P2(n) (where n represents the index of the element in P2), if the value of the P2(n)th element of vector P1 is negative, subtract the minimum transition gate Rq preset in the radar parameters from all element values ​​in vector P0 that have an index after P2(n). If the value of the P2(n)th element of vector P1 is positive, add the minimum transition gate Rq preset in the radar parameters to all element values ​​in vector P0 that have an index after P2(n).

[0058] S1045. Quantize the target position P3 using a preset minimum jump gate Rq to obtain the reference distance change.

[0059] S1046. Perform a 5th-order polynomial fitting on the target position P3 to obtain a smooth target position change R. T0 ;

[0060] S1047, Smooth the target position change R T0 Differential processing is performed to obtain an estimate of the target's radial velocity.

[0061] It should be noted that in existing technologies, most ground-based radar imaging processing is achieved through non-fully coherent methods, requiring a high signal-to-noise ratio (SNR) for imaging, making it difficult to achieve refined target imaging under low SNR conditions. In this embodiment, by analyzing the radar imaging mechanism and radar hardware, a deeper understanding of the factors affecting radar coherence and their impact on radar imaging performance is gained. The prior information of the fixed minimum jump gate is fully utilized, and the precise changes in the gate and reference range are retrieved through envelope alignment, thereby accurately restoring the coherence of the echo data.

[0062] In this embodiment, prior information about the fixed minimum jump gate of the prior radar is used to compensate for jump changes in the envelope position.

[0063] S105. Based on the estimate of the target radial velocity, construct a high-speed compensation function.

[0064] Specifically, in this embodiment, based on the estimation of the target radial velocity Constructing a high-speed compensation function H vIts expression is:

[0065]

[0066]

[0067]

[0068] Where exp(·) is the exponential function, j is the imaginary unit, π is pi, c is the speed of light, and f c For carrier frequency parameters, For the sake of speed, i = -Nr / 2, -Nr / 2+1, ..., Nr / 2, where i is the index of the distance cell (based on the middle position), F s Where is the distance sampling rate, and Nr is the number of sampling points in the distance direction.

[0069] S106. Multiply the high-speed compensation function with the deslant radar echo data to obtain the first compensation data.

[0070] Specifically, in this embodiment, the problem of intra-pulse Doppler modulation caused by high-speed moving targets is considered. By deriving the accurate expression of the deslant echo, a high-speed compensation function is constructed to compensate for the intra-pulse Doppler modulation caused by the high-speed movement of the target. The high-speed compensation function is multiplied with the deslant radar echo data to compensate for the influence of intra-pulse Doppler modulation caused by high-speed movement.

[0071] S107. Perform distance-to-Fourier transform on the first compensation data, and then perform compensation on the remaining video items to obtain the data after compensation for the remaining video items.

[0072] Specifically, in this embodiment, the above process includes:

[0073] S1071. Perform a distance-to-Fourier transform on the first compensation data to transform the first compensation data to the frequency domain, and obtain the first processed data.

[0074] S1072. Construct the remaining video item compensation function H RVP Its expression is:

[0075]

[0076] Among them, f r f is the distance frequency. r =i·F s / Nr,i=-Nr / 2,-Nr / 2+1,…Nr / 2, where γ is the modulation frequency of the transmitted signal;

[0077] S1073, Use the residual video item compensation function H RVPThe phase at the peak of the scattering point pulse compression is used to approximate the phase of the RVP (Residual Video Phase), and the first processed data is compensated to obtain the data after compensation of the residual video item.

[0078] S108. Perform range-directed inverse Fourier transform on the data after compensation for the remaining video terms. Based on the estimation of the reference distance change, the smoothed target position change, and the target radial velocity, construct a jump compensation function. Multiply the jump compensation function with the data after compensation for the remaining video terms to perform jump compensation, and obtain the data after gate jump node compensation and dynamic coarseness compensation.

[0079] Specifically, in this embodiment, the above process includes:

[0080] S1081. Perform distance-directed inverse Fourier transform on the data after compensation of the remaining video items to obtain the second processed data.

[0081] S1082, Based on the smooth target position change R T0 Estimation of target radial velocity Constructing the jump compensation function H com1 Its expression is:

[0082]

[0083] Where v is the velocity of the high-speed moving target. For speed-related factors;

[0084] S1083, Using the jump compensation function H com1 The second processed data is compensated to obtain data after gate transition node compensation and dynamic coarseness compensation.

[0085] It should be noted that the jump compensation function is for envelope jump compensation and phase jump compensation.

[0086] S109. Perform a two-dimensional fast Fourier transform on the data after compensation of the gate transition node to obtain the target Doppler spectrum. Discard the noise regions at both ends of the target Doppler spectrum and then perform an inverse fast Fourier transform in the azimuth direction to obtain the Doppler filtered data.

[0087] S110. The Doppler filtered data is uniformly compensated, and then Fourier transforms are performed in the range and azimuth directions to obtain the inverse synthetic aperture radar image of the target focus.

[0088] Specifically, in this embodiment, the above process includes:

[0089] S1101. Extract the azimuth error phase from the Doppler-filtered data using the phase gradient autofocusing method.

[0090] S1102, Using azimuth error phase Invert target distance change R T1 Its expression is:

[0091]

[0092] Where λ is the wavelength of the electromagnetic wave emitted by the radar;

[0093] S1103, Based on the change in target distance R T1 Construct a unified compensation function H com2 Its expression is:

[0094]

[0095] S1104. Use a unified compensation function to compensate the data after Doppler filtering to obtain the third processed data;

[0096] S1105. Perform distance-to-Fourier transform on the third-processed data, and then perform keystone transform migration correction to obtain the fourth-processed data.

[0097] S1106. Perform azimuth-to-Fourier transform on the fourth processing data to obtain the inverse synthetic aperture radar image of the target focus.

[0098] In summary, this invention provides a deskewing echo coherence recovery method based on radar gate jump priors. Based on radar principles, it derives an accurate radar deskewing echo data expression for high-speed moving targets, and estimates the position of the echo pulse compression envelope using envelope alignment. Based on the prior information that the minimum gate jump distance remains unchanged, it performs jump compensation processing on the estimated envelope position. It then fits the envelope to estimate the target's range and velocity variations relative to the radar. A high-speed compensation function for the deskewing echo is constructed to compensate for intra-pulse Doppler modulation. A residual video term compensation function is constructed to compensate for the spatially varying phase error of the range. An envelope phase unified compensation function is constructed based on the fitted range and velocity to compensate for the effects of jump envelopes and target motion. Azimuth Doppler filtering is performed to improve the echo signal-to-noise ratio. Phase gradient self-focusing extracts the error phase of the echo, and an envelope phase unified compensation function is constructed to perform motion-based fine compensation for the echo. A fast Fourier transform (FFT) is performed in the azimuth direction to obtain the target's range-Doppler ISAR imaging results.

[0099] In an optional embodiment of the present invention, the effectiveness of the proposed method for deslanting echo coherence recovery based on radar gate transition prior is verified by simulation experiments.

[0100] I. Simulation Content

[0101] Please refer to Table 1 for setting the parameters of the simulation experiment. Table 1 contains the simulation radar parameters. Please refer to Table 2 for the target parameters.

[0102] Table 1 Simulation Radar Parameters

[0103] Center frequency bandwidth Pulse width Pulse repetition frequency Sampling rate Pulse count 9.5GHz 1.3GHz 200us 150Hz 120MHz 1024

[0104] Table 2 Target Parameters

[0105] Initial radial velocity radial acceleration initial distance 1000m / s <![CDATA[500m / s 2 ]]> 500km

[0106] Please see Figure 2 As shown, Figure 2 This is a schematic diagram illustrating the relative positions of target scattering points in a simulation experiment provided in this embodiment of the invention, wherein the target is 40m long and 10m wide. Figure 2 It includes three marker points: marker point 1, marker point 2, and marker point 3.

[0107] In the simulation experiment, the simulation data were processed using the method provided by this invention and the actual parameters, respectively. Please refer to [link / reference]. Figure 3 As shown, Figure 3 This is a schematic diagram of a target distance variation curve provided in an embodiment of the present invention. Figure 3 The solid line represents the target position change curve with the first pulse target position as the reference point, while the dashed line represents the target position change curve estimated by the method provided in this invention. The solid and dashed lines almost overlap, indicating that the method provided in this invention can effectively estimate the target position change curve. Please refer to [link to other documentation]. Figure 4 As shown, Figure 4 This is a schematic diagram of a target velocity change curve provided in an embodiment of the present invention. Figure 4 The solid line represents the target's velocity variation curve relative to the radar, and the dashed line represents the target's radial velocity variation curve estimated by the method provided in this invention. The solid and dashed lines almost overlap, indicating that the method provided in this invention can effectively estimate the target's radial velocity variation curve; please refer to... Figure 5 As shown, Figure 5 This is a schematic diagram of the target deslant echo distance pulse compression result provided in an embodiment of the present invention. Figure 5 This is the range pulse compression result of radar deslant echo data at a signal-to-noise ratio of 0dB; please refer to [link / reference]. Figure 6 As shown, Figure 6This is a schematic diagram of the range envelope slice of the last pulse processed by the method provided by this invention and conventional methods, as provided in this embodiment of the invention. Conventional methods do not consider intra-pulse Doppler modulation, resulting in severe range defocus in the pulse compression results, making it impossible to clearly distinguish scattering points. The method provided by this invention considers intra-pulse Doppler modulation and uses the estimated velocity to construct a high-speed compensation function for compensation. The pulse compression results show eight clear peaks, representing eight scattering points of the target, and the pulse compression results have a smaller main lobe and lower side lobes. See also... Figure 7 As shown, Figure 7 This is a schematic diagram of the pulse compression envelope after translational compensation of the deskewing echo using the method of this invention, provided in an embodiment of the invention. The pulse compression envelope has been compensated into a horizontal straight line, indicating that the method provided by this invention has high accuracy; see also Figures 8(a) to 8(b) As shown, Figure 8(a) is a schematic diagram of the ideal ISAR imaging result provided by the embodiment of the present invention, and Figure 8(b) is a schematic diagram of the method ISAR imaging result provided by the embodiment of the present invention. It can be seen that all scattering points in the imaging result are well focused, the separation between the main lobe and the side lobe is high, and the side lobe presents a standard cross shape.

[0108] To further illustrate the results, Figure 2 The three marker points are magnified for analysis, and their two-dimensional contour maps and impulse response functions (IRF) in the range and azimuth directions are plotted. Figure 9(a) is a schematic diagram of the contour map of marker point 1 under ideal conditions provided by the embodiment of the present invention. Figure 9(b) is a schematic diagram of the contour map of marker point 1 under the method provided by the embodiment of the present invention. Figure 9(c) is a schematic diagram of the range slice of marker point 1 under the embodiment of the present invention. Figure 9(d) is a schematic diagram of the azimuth slice of marker point 1 under the embodiment of the present invention. Figure 10(a) is a schematic diagram of the contour map of marker point 2 under ideal conditions provided by the embodiment of the present invention. Figure 10(b) is a schematic diagram of the contour map of marker point 2 under the method provided by the embodiment of the present invention. Figure 10(c) is a schematic diagram of the contour map of marker point 2 under ideal conditions provided by the embodiment of the present invention. Figure 10(d) is a schematic diagram of a distance slice of marker point 2 provided in an embodiment of the present invention. Figure 11(a) is a schematic diagram of a contour map of marker point 3 under ideal conditions provided in an embodiment of the present invention. Figure 11(b) is a schematic diagram of a contour map of marker point 3 provided in an embodiment of the present invention. Figure 11(c) is a schematic diagram of a distance slice of marker point 3 provided in an embodiment of the present invention. Figure 11(d) is a schematic diagram of a contour map of marker point 3 provided in an embodiment of the present invention. The correctness, effectiveness and reliability of the present invention have been verified through simulation experiments.

[0109] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0110] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0111] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for coherent recovery of deslanted echoes based on radar gate transition priors, characterized in that, include: Acquire deslant radar echo data; Perform range-direction fast Fourier transform on the deslant radar echo data to obtain the echo envelope; The echo envelopes corresponding to adjacent pulses are correlated to obtain correlation results. The positional change of the echo envelopes corresponding to adjacent pulses is estimated based on the maximum position of the correlation results, resulting in a vector. ; For the vector Perform untangling to obtain the target untangling position. Based on the target position of the unwound object, the reference distance change and the smoothed target position change are obtained. The smoothed target position change is then differentially processed to obtain an estimate of the target radial velocity. Based on the estimated radial velocity of the target, a high-speed compensation function is constructed; Multiply the high-speed compensation function with the deslant radar echo data to obtain the first compensation data; The first compensation data is processed by distance-to-Fourier transform, and then the remaining video items are compensated to obtain the data after the remaining video items are compensated. The data after compensation of the remaining video items is processed by inverse Fourier transform in the distance direction. Based on the change of the reference distance, the change of the smoothed target position, and the estimation of the target radial velocity, a jump compensation function is constructed. The jump compensation function is multiplied with the data after compensation of the remaining video items to perform jump compensation, and the data after gate jump node compensation and dynamic coarseness compensation is obtained. A two-dimensional fast Fourier transform is performed on the data after compensation for the gate jump node and coarse translation to obtain the target Doppler spectrum. The noise regions at both ends of the target Doppler spectrum are discarded, and then an inverse fast Fourier transform is performed in the azimuth direction to obtain the data after Doppler filtering. The Doppler-filtered data is uniformly compensated, and then Fourier transforms are performed in the range and azimuth directions to obtain an inverse synthetic aperture radar image of the target focus.

2. The method for deslanting echo coherence recovery based on radar gate transition prior as described in claim 1, characterized in that, The acquisition of deslant radar echo data includes: Acquire echo signal; The echo signal is multiplied by the conjugate of a preset deskewing reference signal to obtain the deskewing echo data.

3. The method for deslanting echo coherence recovery based on radar gate transition prior as described in claim 1, characterized in that, For the vector Perform untangling to obtain the target untangling position. Based on the unwinding target position, a reference distance change and a smoothed target position change are obtained. The smoothed target position change is then differentially processed to obtain an estimate of the target radial velocity, including: For the vector Perform difference processing to obtain a vector. ; Calculate the vector maximum value ; Obtain the vector The position of elements whose absolute value is greater than a preset threshold Wherein, the preset threshold ; The vector Central The position value minus the preset minimum transition gate The target position for untangling is obtained. ; For the target location With preset minimum transition gate Quantization is performed to obtain the change in reference distance. ; The target location A 5th-order polynomial fitting was performed to obtain a smooth target position change. ; The smooth target position change Differential processing is performed to obtain an estimate of the target's radial velocity. .

4. The method for deslanting echo coherence recovery based on radar gate transition prior as described in claim 1, characterized in that, The high-speed compensation function The expression is: ； ； ； in, It is an exponential function. The imaginary unit, Pi At the speed of light, For carrier frequency parameters, For the sake of speed, , The subscript for the distance cell. For distance sampling rate, These are sampling points in the distance direction.

5. The method for deslanting echo coherence recovery based on radar gate transition prior as described in claim 1, characterized in that, The step of performing a distance-to-Fourier transform on the first compensated data, followed by compensation for the remaining video items, to obtain the data after compensation for the remaining video items includes: The first compensation data is subjected to a distance-to-Fourier transform to obtain the first processed data; Construct the compensation function for the remaining video items Its expression is: ； in, For distance frequency, , For the frequency modulation of the transmitted signal, The imaginary unit; Using the remaining video item compensation function The first processed data is compensated to obtain the compensated data for the remaining video items.

6. The method for deslanting echo coherence recovery based on radar gate transition prior as described in claim 1, characterized in that, The data after compensation for the remaining video terms is processed by inverse Fourier transform in the range direction. Based on the changes in the reference distance, the smoothed changes in the target position, and the estimated radial velocity of the target, a jump compensation function is constructed. The jump compensation function is then multiplied by the data after compensation for the remaining video terms to perform jump compensation, resulting in data after gate jump node compensation and motion coarsening compensation, including: The remaining video data after compensation is processed by inverse Fourier transform in the distance direction to obtain the second processed data; Based on the smooth target position change and the estimation of the target radial velocity Construct a jump compensation function Its expression is: in, For the estimated target radial velocity, For speed-related factors, The imaginary unit, For carrier frequency parameters, At the speed of light, To save time; Using the jump compensation function The second processed data is compensated to obtain the data after gate switching node compensation and translational coarseness compensation.

7. The method for deslanting echo coherence recovery based on radar gate transition prior as described in claim 1, characterized in that, The process of uniformly compensating the Doppler-filtered data and then performing range and azimuth Fourier transforms to obtain an inverse synthetic aperture radar image of the focused target includes: The azimuth error phase was extracted from the Doppler-filtered data using the phase gradient autofocusing method. ; Using the aforementioned azimuth error phase Invert target distance change Its expression is: ； in, The wavelength of the electromagnetic waves emitted by the radar; Based on the change in target distance Construct a unified compensation function Its expression is: ； in, The imaginary unit, For carrier frequency parameters, At the speed of light, To save time, The estimated target radial velocity; The unified compensation function is used to compensate the Doppler filtered data to obtain the third processed data; The third processed data is subjected to distance-to-Fourier transform and then Keystone transform migration correction to obtain the fourth processed data. The fourth processed data is subjected to azimuth-to-Fourier transform to obtain an inverse synthetic aperture radar image of the target focus.

Images