Electromagnetic vortex wave SAR motion error estimation and compensation method

Abstract

This application relates to a method for estimating and compensating motion errors in electromagnetic vortex wave SAR. It establishes a geometric and signal model for motion errors in electromagnetic vortex wave SAR, designs a sub-aperture error estimation process, and solves the problem of wide-beam motion error estimation in electromagnetic vortex wave SAR. Furthermore, it designs an electromagnetic vortex wave amplitude and phase weighted compensation function, eliminating the influence of amplitude and phase weighting of electromagnetic vortex waves in SAR echo acquisition on motion error estimation, effectively solving the motion error estimation problem in electromagnetic vortex wave SAR. Under multi-platform deployment conditions, it can achieve precise focusing of electromagnetic vortex wave SAR, providing a reference for future multi-platform deployment electromagnetic vortex wave SAR experiments and applications.

Description

Technical Field

[0001] This application relates to the field of microwave remote sensing, specifically to a method for estimating and compensating motion errors in electromagnetic vortex wave SAR. Background Technology

[0002] Synthetic Aperture Radar (SAR) can perform observations around the clock and in all weather conditions, unaffected by weather or other factors. Electromagnetic vortex wave radar, a novel radar system carrying orbital angular momentum and possessing a helical phase wavefront, can acquire more observational information when combined with SAR systems. However, during electromagnetic vortex wave SAR imaging, especially when the radar platform (e.g., vehicle-mounted or airborne platforms) cannot move along an ideal straight trajectory (i.e., motion errors exist), the imaging quality of electromagnetic vortex wave SAR will be affected. Unlike traditional plane wave SAR motion error estimation and compensation, electromagnetic vortex wave radar is affected by Bessel antenna pattern modulation and additional vortex azimuth phase, which introduces additional amplitude weighting and phase modulation into the motion error estimation, impacting the estimation performance of traditional motion error estimation methods. Summary of the Invention

[0003] To overcome at least one deficiency in the prior art, this application provides a method for estimating and compensating motion errors in electromagnetic vortex wave SAR.

[0004] Firstly, a method for estimating and compensating motion errors in electromagnetic vortex wave SAR is provided, including:

[0005] Range pulse compression is performed on the echo signal of the scene target, and range blocks are divided to obtain multiple range blocks;

[0006] Perform distance migration correction on each distance block to obtain the distance migration corrected signal;

[0007] The distance migration corrected signal is divided into multiple sub-aperture data, with overlap between adjacent sub-aperture data;

[0008] Phase compensation is performed on each sub-aperture data to obtain phase-compensated sub-aperture data;

[0009] The phase-compensated sub-aperture data is dechirp-processed to obtain the dechirp-processed signal; the dechirp-processed signal includes multiple range cells.

[0010] Multiple range cells are sorted according to their energy intensity, and several range cells with higher energy are selected.

[0011] The electromagnetic vortex wave phase gradient estimation kernel is used to estimate the phase gradient based on several distance cells with strong energy, so as to obtain the electromagnetic vortex wave phase gradient estimate for each sub-aperture data.

[0012] The full aperture is synthesized based on the electromagnetic vortex wave phase gradient estimate to obtain the phase gradient estimate of the full aperture corresponding to each sub-range block; the phase gradient estimate of the full aperture corresponding to each sub-range block is integrated to obtain the motion phase error estimate of the full aperture corresponding to each sub-range block; the motion phase error estimate of the full aperture corresponding to all range blocks constitutes the final motion phase error estimate of the full aperture.

[0013] The final full-aperture motion phase error estimation result is used to compensate the echo signal after range pulse compression to obtain the compensated signal; range migration correction and azimuth matching filtering are then performed on the compensated signal to obtain the focused image.

[0014] In one embodiment, phase compensation is performed on each sub-aperture data to obtain phase-compensated sub-aperture data, including:

[0015] Perform an azimuth-to-Fourier transform on the sub-aperture data, multiply it with the phase compensation function, and then perform an inverse azimuth-to-Fourier transform to obtain the phase-compensated sub-aperture data.

[0016] The phase compensation function is:

[0017]

[0018]

[0019]

[0020] Among them, H sub (f a f is the phase compensation function. a For Doppler frequency, Let l be the phase, l be the mode number, and v be the radar platform velocity. For stationary phase point, x p For target X u Coordinates along the y-axis p For target Y u The coordinates along the axis, λ is the wavelength of the transmitted signal, and R B This is the nearest slope distance.

[0021] In one embodiment, an electromagnetic vortex wave phase gradient estimation kernel is used to estimate the phase gradient based on several high-energy range cells to obtain the electromagnetic vortex wave phase gradient estimate for each sub-aperture data, using the following formula:

[0022]

[0023] in, Here, p is the estimated phase gradient value of the electromagnetic vortex wave, n is the index of the range block, k′ is the index of the sub-aperture data, m is the index of the selected high-energy range cell, M is the number of selected high-energy range cells, and h is the index of the range cell. p,k′ Here, represents the weighting factor of the Bessel function for electromagnetic vortex waves, conj is the conjugate operation, arg is the angle operation, and s... n (m,k′) represents the azimuth coordinate signal of the k′th range cell selected from the mth range cell with relatively strong energy in the nth sub-aperture data.

[0024] In one embodiment, full aperture synthesis is performed based on the electromagnetic vortex wave phase gradient estimate to obtain the full aperture phase gradient estimate result for each sub-range block, including:

[0025] Subtract the phase gradients of electromagnetic vortex waves in the overlapping portions of two adjacent sub-aperture data, and perform linear fitting based on the subtraction result to obtain the linear fitting result.

[0026] The aligned sub-aperture data is obtained by subtracting the linear fitting result from the electromagnetic vortex wave phase gradient of the latter sub-aperture data in two adjacent sub-aperture data sets.

[0027] Before taking the first sub-aperture data The electromagnetic vortex wave phase gradient of the data length, where α is the overlap rate of adjacent sub-aperture data, and L sub The data length of the sub-aperture data, followed by the last sub-aperture data. The electromagnetic vortex wave phase gradient of the data length, and the intermediate (1-α)·L of other sub-aperture data. sub The phase gradient of the electromagnetic vortex wave over the data length, and the estimated phase gradient of the full aperture corresponding to the synthesized sub-range block.

[0028] Secondly, an electromagnetic vortex wave SAR motion error estimation and compensation device is provided, comprising:

[0029] The range block segmentation module is used to perform range pulse compression on the echo signal of the scene target and to segment it into range blocks to obtain multiple range blocks;

[0030] The distance migration correction module is used to perform distance migration correction on each distance block to obtain the distance migration corrected signal;

[0031] The sub-aperture segmentation module is used to divide the range migration corrected signal into multiple sub-aperture data, with overlap between adjacent sub-aperture data.

[0032] The phase compensation module is used to perform phase compensation on each sub-aperture data to obtain phase-compensated sub-aperture data;

[0033] The dechirp processing module is used to perform dechirp processing on the phase-compensated sub-aperture data to obtain the dechirp-processed signal; the dechirp-processed signal includes multiple range cells.

[0034] The sorting module is used to sort multiple distance cells according to their energy intensity and select several distance cells with stronger energy.

[0035] The phase gradient estimation module is used to perform phase gradient estimation based on several high-energy distance cells using the electromagnetic vortex wave phase gradient estimation kernel, and obtain the electromagnetic vortex wave phase gradient estimate value for each sub-aperture data.

[0036] The full aperture synthesis module is used to synthesize the full aperture based on the electromagnetic vortex wave phase gradient estimate, and obtain the phase gradient estimate result of the full aperture corresponding to each sub-range block; the phase gradient estimate result of the full aperture corresponding to each sub-range block is integrated to obtain the motion phase error estimate result of the full aperture corresponding to each sub-range block; the motion phase error estimate results of the full aperture corresponding to all range blocks constitute the final motion phase error estimate result of the full aperture.

[0037] The compensation module is used to compensate the echo signal after range pulse compression using the final full-aperture motion phase error estimation result to obtain the compensated signal; range migration correction and azimuth matching filtering are performed on the compensated signal to obtain the focused image.

[0038] In one embodiment, the phase compensation module is further used for:

[0039] Perform an azimuth-to-Fourier transform on the sub-aperture data, multiply it with the phase compensation function, and then perform an inverse azimuth-to-Fourier transform to obtain the phase-compensated sub-aperture data.

[0040] The phase compensation function is:

[0041]

[0042]

[0043]

[0044] Among them, H sub (f a f is the phase compensation function. a For Doppler frequency, Let l be the phase, l be the mode number, and v be the radar platform velocity. For stationary phase point, x p For target X u Coordinates along the y-axis p For target Yu The coordinates along the axis, λ is the wavelength of the transmitted signal, and R B This is the nearest slope distance.

[0045] In one embodiment, the phase gradient estimation module is further configured to obtain an estimated electromagnetic vortex wave phase gradient for each sub-aperture data using the following formula:

[0046]

[0047] in, Here, p is the estimated phase gradient value of the electromagnetic vortex wave, n is the index of the range block, k′ is the index of the azimuth coordinates of the sub-aperture data, m is the index of the selected high-energy range cell, M is the number of selected high-energy range cells, and h is the index of the range cell. p,k′ Here, represents the weighting factor of the Bessel function for electromagnetic vortex waves, conj is the conjugate operation, arg is the angle operation, and s... n (m,k′) represents the azimuth coordinate signal of the k′th range cell selected from the mth range cell with relatively strong energy in the nth sub-aperture data.

[0048] In one embodiment, the full-aperture synthesis module is also used for:

[0049] Subtract the phase gradients of electromagnetic vortex waves in the overlapping portions of two adjacent sub-aperture data, and perform linear fitting based on the subtraction result to obtain the linear fitting result.

[0050] The aligned sub-aperture data is obtained by subtracting the linear fitting result from the electromagnetic vortex wave phase gradient of the latter sub-aperture data in two adjacent sub-aperture data sets.

[0051] Before taking the first sub-aperture data The electromagnetic vortex wave phase gradient of the data length, where α is the overlap rate of adjacent sub-aperture data, and L sub The data length of the sub-aperture data, followed by the last sub-aperture data. The electromagnetic vortex wave phase gradient of the data length, and the intermediate (1-α)·L of other sub-aperture data. sub The phase gradient of the electromagnetic vortex wave over the data length, and the estimated phase gradient of the full aperture corresponding to the synthesized sub-range block.

[0052] Compared with the prior art, this application has the following beneficial effects: The electromagnetic vortex wave SAR motion error estimation and compensation method of this application establishes the geometric model and signal model of electromagnetic vortex wave SAR motion error, designs the sub-aperture error estimation process, and solves the problem of wide beam motion error estimation of electromagnetic vortex wave SAR; it designs the electromagnetic vortex wave amplitude and phase weighted compensation function, removes the influence of amplitude and phase weighting of electromagnetic vortex waves in SAR echo acquisition on motion error estimation, effectively solves the problem of electromagnetic vortex wave SAR motion error estimation, and can achieve precise focusing of electromagnetic vortex wave SAR under multi-platform loading conditions, providing reference and guidance for future multi-platform loading electromagnetic vortex wave SAR experiments and applications. Attached Figure Description

[0053] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings, which, together with the detailed description below, are incorporated in and form part of this specification. In the drawings:

[0054] Figure 1 A flowchart of the motion error estimation and compensation method for electromagnetic vortex wave SAR is shown.

[0055] Figure 2 A geometric model of electromagnetic vortex wave SAR considering motion errors is shown.

[0056] Figure 3 The image shows the electromagnetic vortex wave SAR imaging results without motion error compensation.

[0057] Figure 4 The image shows the results of electromagnetic vortex wave SAR imaging without using a phase compensation function and an electromagnetic vortex wave weighted phase gradient estimation kernel for motion error estimation and compensation.

[0058] Figure 5 The following image shows the electromagnetic vortex wave SAR imaging results after motion error estimation and compensation using the method of this application;

[0059] Figure 6 A block diagram of the electromagnetic vortex wave SAR motion error estimation and compensation device is shown. Detailed Implementation

[0060] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of the actual embodiments are described in the specification. However, it should be understood that many embodiment-specific decisions can be made in the development of any such actual embodiment to achieve the developer’s specific objectives, and these decisions may vary as the embodiments differ.

[0061] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the device structure closely related to the solution according to this application is shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0062] It should be understood that this application is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, embodiments may be combined with each other, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in one embodiment, where feasible.

[0063] This application provides a method for estimating and compensating motion errors in electromagnetic vortex wave SAR. The method is verified through simulation experiments, and all steps and conclusions are validated using Matlab R2017b. The parameters required for the simulation in this embodiment are shown in Table 1.

[0064] Table 1

[0065]

[0066]

[0067] The application scenario of this embodiment is as follows: This embodiment can be applied to vehicle-mounted and airborne electromagnetic vortex wave SAR imaging. The geometric and signal models of electromagnetic vortex wave SAR motion errors are suitable for electromagnetic vortex wave radars mounted on moving platforms and operating in SAR mode. This method solves the problem of focusing difficulties in electromagnetic vortex wave SAR when motion errors exist by establishing a geometric and signal model of electromagnetic vortex wave SAR motion errors, designing sub-aperture error estimation and electromagnetic vortex wave amplitude and phase weighted compensation functions.

[0068] Figure 1 A flowchart illustrating the motion error estimation and compensation method for electromagnetic vortex wave SAR is shown. (See attached image.) Figure 1 The methods include:

[0069] Step S1: Perform range pulse compression on the echo signal of the scene target and divide it into range blocks to obtain multiple range blocks.

[0070] Establish a coordinate system O for a uniform circular array antenna u -X u Y u Z u The origin of the coordinate system is the center O of the circle. u Point, X u The axis is along the direction of motion of the radar platform, Z u The axis is perpendicular to the array plane and points in the direction of signal propagation. uThe axis is determined by the right-hand rule. The electromagnetic vortex wave signal employs a uniform circular array transmission and reception method. The geometric models of all embodiments are established in the uniform circular array antenna coordinate system.

[0071] Establish a motion error model, and define the ideal motion trajectory of the radar platform as P. r0 (t a )=(v·t a ,0,0) T The positional error of the radar platform deviating from the ideal trajectory can be expressed as ΔP. r (t a )=(ΔX r (t a ),ΔY r (t a ),ΔZ r (t a )) T The actual trajectory of the radar platform is P r (t a )=(v·t a +ΔX r (t a ),ΔY r (t a ),ΔZ r (t a )) T Where v is the speed of the radar platform, t a For azimuth and time, ΔX r (t a ), ΔY r (t a ), ΔZ r (t a ) are respectively t a The three-axis position error of the radar platform deviating from the ideal motion trajectory.

[0072] Let P be the coordinates of any target in the scene. target =(x p ,y p ,z p ) T The instantaneous pitch and azimuth angles introduced by the electromagnetic vortex wave are calculated as follows:

[0073]

[0074]

[0075] in,

[0076] It is the instantaneous slant range between the radar and the target, which includes the instantaneous slant range under the ideal flight trajectory. The instantaneous slant range error caused by motion error is expressed as ΔR(t) a )=R(t a )-R0(t a A uniform circular array is used to transmit and receive electromagnetic vortex waves of different modes. The uniform circular array transmits a linear frequency modulated signal with a modulation frequency of γ. An electromagnetic vortex wave SAR echo signal model s is established. r (t r ,t m ):

[0077]

[0078] Among them, t r Let c be the speed of light, and J be the speed of time. l (kasinθ(t a )) is a Bessel function of the first kind related to the modal number l, a r (·) is the range window function, λ is the wavelength of the transmitted signal, k is the wave number, and a is the array radius.

[0079] Range pulse compression is performed on the echo signal, including performing a range-directed FFT to transform it to the range frequency domain, and then comparing it with the range pulse compression function. Multiplication completes the range pulse compression, yielding the signal envelope after range pulse compression, where f r γ is the distance frequency. γ is the modulation frequency.

[0080] Considering that the amplitude and phase modulation of electromagnetic vortex waves introduced when the electromagnetic vortex wave radar operates in SAR mode varies with range, range segmentation is performed on the echo data after range pulse compression, dividing it into P = 5 range blocks. The segmentation criterion is that the spatial invariance of the amplitude and phase modulation of electromagnetic vortex waves can be ignored within each range block.

[0081] Step S2: Perform distance migration correction on each distance block to obtain the distance migration corrected signal.

[0082] Step S3: Divide the distance migration corrected signal into multiple sub-aperture data, with adjacent sub-aperture data overlapping.

[0083] The number of sub-apertures is designed to be N=32, and the overlap rate α between sub-aperture data can be set according to actual needs, for example, it can be 50%.

[0084] Step S4: Perform phase compensation on each sub-aperture data to obtain phase-compensated sub-aperture data.

[0085] Specifically, the sub-aperture data is subjected to azimuth-to-Fourier transform, multiplied with the phase compensation function, and then subjected to azimuth-to-inverse Fourier transform to obtain the phase-compensated sub-aperture data.

[0086] The phase compensation function is:

[0087]

[0088]

[0089]

[0090] Among them, H sub (f a f is the phase compensation function. a For Doppler frequency, Let l be the phase, l be the mode number, and v be the radar platform velocity. For stationary phase point, x p For target X u Coordinates along the y-axis p For target Y u The coordinates along the axis, λ is the wavelength of the transmitted signal, and R B This is the nearest slope distance.

[0091] Step S5: Perform dechirp processing on the phase-compensated sub-aperture data to obtain the dechirp-processed signal; the dechirp-processed signal includes multiple range cells. Dechirp processing is used to remove frequency modulation effects caused by velocity or distance variations, thereby extracting the required target information.

[0092] Here, the dechirp function is designed as follows: Where R s t is the reference slant distance at the scene center point. sub λ represents the azimuth time of the sub-aperture. λ is the wavelength of the transmitted signal, and v is the speed of the radar platform.

[0093] Step S6: Sort the multiple range cells according to their energy intensity and select several range cells with stronger energy.

[0094] Here, for example, the top 20% of the range cells in the sorting results can be considered as several range cells with relatively strong energy, or range cells with energy intensity greater than a set threshold can be considered as several range cells with relatively strong energy. Then, a frequency shift function is constructed to move several range cells with relatively strong energy to the center position of the sub-aperture and extract them by windowing, for the next step of phase gradient estimation.

[0095] Step S7: The electromagnetic vortex wave phase gradient estimation kernel is used to estimate the phase gradient based on several distance cells with strong energy, so as to obtain the electromagnetic vortex wave phase gradient estimate value of each sub-aperture data.

[0096] Specifically, the following formula is used:

[0097]

[0098] in, Here, p is the estimated phase gradient value of the electromagnetic vortex wave, n is the index of the range block, k′ is the index of the sub-aperture data, m is the index of the selected high-energy range cell, M is the number of selected high-energy range cells, and h is the index of the range cell. p，k′ Here, represents the weighting factor of the Bessel function for electromagnetic vortex waves, conj is the conjugate operation, arg is the angle operation, and s... n (m, k′) represents the azimuth coordinate signal of the k′th range cell selected from the mth range cell with relatively strong energy in the nth sub-aperture data.

[0099] Specifically, the weighting factor h of the Bessel function for electromagnetic vortex waves. p，k′ :

[0100]

[0101]

[0102] Among them, J l (kasinθ(t sub (k′))) is a Bessel function of the first kind related to the mode number l, where k is the wave number, a is the array radius, and α(t) is the wave number. sub (k′)) is t sub The instantaneous pitch angle at time (k′), t sub (k′) represents the discrete time of the sub-aperture azimuth direction, R0(t) sub (k′)) is t sub The instantaneous slope distance at time (k′). ΔX r (t sub (k′)) is t sub At time (k′), the radar platform deviates from its ideal trajectory by X. u Shaft position error.

[0103] Step S8: Perform full aperture synthesis based on the electromagnetic vortex wave phase gradient estimate to obtain the phase gradient estimate result of the full aperture corresponding to each sub-distance block; integrate the phase gradient estimate result of the full aperture corresponding to each sub-distance block to obtain the motion phase error estimate result of the full aperture corresponding to each sub-distance block; the motion phase error estimate results of the full aperture corresponding to all distance blocks constitute the final motion phase error estimate result of the full aperture.

[0104] Specifically, full-aperture synthesis is performed based on the estimated phase gradient values ​​of the electromagnetic vortex waves to obtain the phase gradient estimation results for the full aperture corresponding to each sub-range block, including:

[0105] Subtract the phase gradients of electromagnetic vortex waves in the overlapping portions of two adjacent sub-aperture data, and perform linear fitting based on the subtraction result to obtain the linear fitting result.

[0106] The aligned sub-aperture data is obtained by subtracting the linear fitting result from the electromagnetic vortex wave phase gradient of the latter sub-aperture data in two adjacent sub-aperture data sets.

[0107] Before taking the first sub-aperture data The electromagnetic vortex wave phase gradient of the data length, where α is the overlap rate of adjacent sub-aperture data, and L sub The data length of the sub-aperture data, followed by the last sub-aperture data. The electromagnetic vortex wave phase gradient of the data length, and the intermediate (1-α)·L of other sub-aperture data. sub The phase gradient of the electromagnetic vortex wave over the data length, and the estimated phase gradient of the full aperture corresponding to the synthesized sub-range block.

[0108] Step S9: The final full-aperture motion phase error estimation result is used to compensate the echo signal after range pulse compression to obtain the compensated signal; range migration correction and azimuth matching filtering are performed on the compensated signal to obtain the focused image.

[0109] In this embodiment, a geometric model and signal model for motion error of electromagnetic vortex wave SAR were established, and a sub-aperture error estimation process was designed, solving the problem of wide-beam motion error estimation in electromagnetic vortex wave SAR. An electromagnetic vortex wave amplitude and phase weighting compensation function was designed to remove the influence of amplitude and phase weighting of electromagnetic vortex waves in SAR echo acquisition on motion error estimation, effectively solving the motion error estimation problem of electromagnetic vortex wave SAR. Precise focusing of electromagnetic vortex wave SAR can be achieved under multi-platform deployment conditions, providing reference and guidance for future multi-platform deployment electromagnetic vortex wave SAR experiments and applications.

[0110] Figure 2 A geometric model diagram of electromagnetic vortex wave SAR considering motion errors is shown. Figure 3 The image shows the results of electromagnetic vortex wave SAR imaging without motion error compensation. It can be seen that when motion errors are present, electromagnetic vortex wave SAR cannot achieve image focusing, resulting in severe image defocusing. Figure 4The image shows the results of electromagnetic vortex wave SAR imaging without using a phase compensation function and an electromagnetic vortex wave weighted phase gradient estimation kernel for motion error estimation and compensation. It can be seen that the imaging results exhibit defocusing and sidelobe lifting, causing the main lobe energy to be unfocused. This is because traditional SAR motion error estimation methods do not consider the Bessel antenna pattern modulation and the additional phase of the vortex azimuth angle introduced by electromagnetic vortex wave SAR. When estimating phase error, the additional phase of the vortex azimuth angle is mixed into the motion error estimation results, and the weighting of the phase error by the Bessel antenna pattern leads to inaccurate estimation of the phase gradient kernel, making it impossible to achieve accurate imaging.

[0111] Figure 5 The image shows the electromagnetic vortex wave SAR imaging results after motion error estimation and compensation using the method of this application. The method of this application fully considers the influence of electromagnetic vortex waves on motion error estimation, designs a phase compensation function and an electromagnetic vortex wave SAR Bessel weighted phase gradient estimation kernel, realizes accurate estimation of electromagnetic vortex wave SAR motion error, and finally realizes accurate imaging of electromagnetic vortex wave SAR when the motion trajectory of the mounted platform deviates from the ideal trajectory.

[0112] Based on the same inventive concept as the electromagnetic vortex wave SAR motion error estimation and compensation method, this embodiment also provides a corresponding electromagnetic vortex wave SAR motion error estimation and compensation device. Figure 6 The block diagram of the electromagnetic vortex wave SAR motion error estimation and compensation device is shown, including:

[0113] The range block division module 61 is used to perform range pulse compression on the echo signal of the scene target and divide it into range blocks to obtain multiple range blocks;

[0114] The distance migration correction module 62 is used to perform distance migration correction on each distance block to obtain the distance migration corrected signal;

[0115] Sub-aperture segmentation module 63 is used to divide the range migration corrected signal into multiple sub-aperture data, with overlap between adjacent sub-aperture data;

[0116] Phase compensation module 64 is used to perform phase compensation on each sub-aperture data to obtain phase-compensated sub-aperture data;

[0117] The dechirp processing module 65 is used to perform dechirp processing on the phase-compensated sub-aperture data to obtain the dechirp-processed signal; the dechirp-processed signal includes multiple range cells.

[0118] The sorting module 66 is used to sort multiple range cells according to their energy intensity and select several range cells with stronger energy.

[0119] The phase gradient estimation module 67 is used to perform phase gradient estimation based on several distance cells with strong energy using an electromagnetic vortex wave phase gradient estimation kernel, so as to obtain the electromagnetic vortex wave phase gradient estimate value for each sub-aperture data.

[0120] The full aperture synthesis module 68 is used to synthesize the full aperture based on the electromagnetic vortex wave phase gradient estimate to obtain the phase gradient estimate result of the full aperture corresponding to each sub-distance block; the phase gradient estimate result of the full aperture corresponding to each sub-distance block is integrated to obtain the motion phase error estimate result of the full aperture corresponding to each sub-distance block; the motion phase error estimate results of the full aperture corresponding to all distance blocks constitute the final motion phase error estimate result of the full aperture.

[0121] The compensation module 69 is used to compensate the echo signal after range pulse compression using the final full aperture motion phase error estimation result to obtain the compensated signal; range migration correction and azimuth matching filtering are performed on the compensated signal to obtain the focused image.

[0122] The electromagnetic vortex wave SAR motion error estimation and compensation device of this embodiment has the same inventive concept as the electromagnetic vortex wave SAR motion error estimation and compensation method described above. Therefore, the specific implementation of this device can be found in the embodiment section of the electromagnetic vortex wave SAR motion error estimation and compensation method described above, and its technical effect corresponds to the technical effect of the above method, so it will not be repeated here.

[0123] The above descriptions are merely various embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for estimating and compensating motion errors in electromagnetic vortex wave SAR, characterized in that, include: Range pulse compression is performed on the echo signal of the scene target, and range blocks are divided to obtain multiple range blocks; Perform distance migration correction on each distance block to obtain the distance migration corrected signal; The distance migration corrected signal is divided into multiple sub-aperture data, with adjacent sub-aperture data overlapping. Phase compensation is performed on each sub-aperture data to obtain phase-compensated sub-aperture data; The phase-compensated sub-aperture data is subjected to dechirp processing to obtain the dechirp-processed signal; The signal processed by dechirp includes multiple distance units; The multiple distance units are sorted according to their energy intensity, and several distance units with stronger energy are selected. The electromagnetic vortex wave phase gradient estimation kernel is used to estimate the phase gradient based on several distance cells with relatively strong energy, so as to obtain the electromagnetic vortex wave phase gradient estimate value for each sub-aperture data. Based on the estimated phase gradient of the electromagnetic vortex wave, the full aperture is synthesized to obtain the phase gradient estimation result of the full aperture corresponding to each sub-distance block; the phase gradient estimation result of the full aperture corresponding to each sub-distance block is integrated to obtain the motion phase error estimation result of the full aperture corresponding to each sub-distance block. The motion phase error estimation results for the entire aperture corresponding to all distance blocks constitute the final motion phase error estimation result for the entire aperture. The final full-aperture motion phase error estimation result is used to compensate the echo signal after range pulse compression to obtain the compensated signal; The compensated signal is subjected to distance migration correction and azimuth matching filtering to obtain a focused image.

2. The method as described in claim 1, characterized in that, in, Phase compensation is performed on each sub-aperture data to obtain phase-compensated sub-aperture data, including: The sub-aperture data is subjected to an azimuth-to-Fourier transform, multiplied with a phase compensation function, and then subjected to an inverse azimuth-to-Fourier transform to obtain phase-compensated sub-aperture data. The phase compensation function is: Among them, H sub (f a f is the phase compensation function. a For Doppler frequency, Let l be the phase, l be the mode number, and v be the radar platform velocity. For stationary phase point, x p For target X u Coordinates along the y-axis p For target Y u The coordinates along the axis, λ is the wavelength of the transmitted signal, and R B This is the nearest slope distance.

3. The method as described in claim 1, characterized in that, in, The electromagnetic vortex wave phase gradient estimation kernel is used to estimate the phase gradient based on several range cells with relatively strong energy, thereby obtaining the electromagnetic vortex wave phase gradient estimate for each sub-aperture data, using the following formula: in, Here, p is the estimated phase gradient value of the electromagnetic vortex wave, n is the index of the range block, k′ is the index of the sub-aperture data, m is the index of the selected high-energy range cell, M is the number of selected high-energy range cells, and h is the index of the range cell. p,k′ Here, represents the weighting factor of the Bessel function for electromagnetic vortex waves, conj is the conjugate operation, arg is the angle operation, and s... n (m,k′) represents the azimuth coordinate signal of the k′th range cell selected from the mth range cell with relatively strong energy in the nth sub-aperture data. n (m,k′+1) represents the azimuth coordinate signal of the (k′+1)th azimuth cell selected from the m-th range cell with relatively strong energy in the n-th sub-aperture data.

4. The method as described in claim 1, characterized in that, in, Based on the estimated electromagnetic vortex wave phase gradient, full aperture synthesis is performed to obtain the phase gradient estimation results for the full aperture corresponding to each sub-range block, including: Subtract the phase gradients of electromagnetic vortex waves in the overlapping portions of two adjacent sub-aperture data, and perform linear fitting based on the subtraction result to obtain the linear fitting result. The aligned sub-aperture data is obtained by subtracting the linear fitting result from the electromagnetic vortex wave phase gradient of the latter sub-aperture data in two adjacent sub-aperture data sets. Before taking the first sub-aperture data The electromagnetic vortex wave phase gradient of the data length, where α is the overlap rate of adjacent sub-aperture data, and L sub The data length of the sub-aperture data, followed by the last sub-aperture data. The electromagnetic vortex wave phase gradient of the data length, and the intermediate (1-α)·L of other sub-aperture data. sub The phase gradient of the electromagnetic vortex wave over the data length is used to synthesize the phase gradient estimation result of the full aperture corresponding to the sub-distance block.

5. A device for estimating and compensating motion errors in electromagnetic vortex wave SAR, characterized in that, include: The range block segmentation module is used to perform range pulse compression on the echo signal of the scene target and to segment it into range blocks to obtain multiple range blocks; The distance migration correction module is used to perform distance migration correction on each distance block to obtain the distance migration corrected signal; The sub-aperture segmentation module is used to divide the distance migration corrected signal into multiple sub-aperture data, with adjacent sub-aperture data overlapping. The phase compensation module is used to perform phase compensation on each sub-aperture data to obtain phase-compensated sub-aperture data; The dechirp processing module is used to perform dechirp processing on the phase-compensated sub-aperture data to obtain the dechirp-processed signal. The signal processed by dechirp includes multiple distance units; The sorting module is used to sort the multiple distance units according to their energy intensity and select several distance units with stronger energy. The phase gradient estimation module is used to perform phase gradient estimation based on several distance cells with relatively strong energy using an electromagnetic vortex wave phase gradient estimation kernel, so as to obtain the electromagnetic vortex wave phase gradient estimation value of each sub-aperture data. The full aperture synthesis module is used to synthesize the full aperture based on the electromagnetic vortex wave phase gradient estimate to obtain the phase gradient estimate result of the full aperture corresponding to each sub-distance block; and to integrate the phase gradient estimate result of the full aperture corresponding to each sub-distance block to obtain the motion phase error estimate result of the full aperture corresponding to each sub-distance block. The motion phase error estimation results for the entire aperture corresponding to all distance blocks constitute the final motion phase error estimation result for the entire aperture. The compensation module is used to compensate the echo signal after range pulse compression using the final full aperture motion phase error estimation result to obtain the compensated signal. The compensated signal is subjected to distance migration correction and azimuth matching filtering to obtain a focused image.

6. The apparatus as claimed in claim 5, characterized in that, The phase compensation module is also used for: The sub-aperture data is subjected to an azimuth-to-Fourier transform, multiplied with a phase compensation function, and then subjected to an inverse azimuth-to-Fourier transform to obtain phase-compensated sub-aperture data. The phase compensation function is: Among them, H sub (f a f is the phase compensation function. a For Doppler frequency, Let l be the phase, l be the mode number, and v be the radar platform velocity. For stationary phase point, x p For target X u Coordinates along the y-axis p For target Y u The coordinates along the axis, λ is the wavelength of the transmitted signal, and R B This is the nearest slope distance.

7. The apparatus as claimed in claim 5, characterized in that, The phase gradient estimation module is also used to obtain the electromagnetic vortex wave phase gradient estimate for each sub-aperture data using the following formula: in, Here, p is the estimated phase gradient value of the electromagnetic vortex wave, n is the index of the range block, k′ is the index of the azimuth coordinates of the sub-aperture data, m is the index of the selected high-energy range cell, M is the number of selected high-energy range cells, and h is the index of the range cell. p,k′ Here, represents the weighting factor of the Bessel function for electromagnetic vortex waves, conj is the conjugate operation, arg is the angle operation, and s... n (m,k′) represents the azimuth coordinate signal of the k′th range cell selected from the mth range cell with relatively strong energy in the nth sub-aperture data. n (m,k′+1) represents the azimuth coordinate signal of the (k′+1)th azimuth cell selected from the m-th range cell with relatively strong energy in the n-th sub-aperture data.

8. The apparatus as claimed in claim 5, characterized in that, The full-aperture synthesis module is also used for: Subtract the phase gradients of electromagnetic vortex waves in the overlapping portions of two adjacent sub-aperture data, and perform linear fitting based on the subtraction result to obtain the linear fitting result. The aligned sub-aperture data is obtained by subtracting the linear fitting result from the electromagnetic vortex wave phase gradient of the latter sub-aperture data in two adjacent sub-aperture data sets. Before taking the first sub-aperture data The electromagnetic vortex wave phase gradient of the data length, where α is the overlap rate of adjacent sub-aperture data, and L sub The data length of the sub-aperture data, followed by the last sub-aperture data. The electromagnetic vortex wave phase gradient of the data length, and the intermediate (1-α)·L of other sub-aperture data. sub The phase gradient of the electromagnetic vortex wave over the data length is used to synthesize the phase gradient estimation result of the full aperture corresponding to the sub-distance block.

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