Electromagnetic vortex wave SAR (Synthetic Aperture Radar) motion error estimation and compensation method

Abstract

The invention relates to an electromagnetic vortex wave SAR (Synthetic Aperture Radar) motion error estimation and compensation method, which establishes an electromagnetic vortex wave SAR motion error geometric model and a signal model, designs a sub-aperture error estimation process, and solves the problem of electromagnetic vortex wave SAR wide beam motion error estimation. According to the electromagnetic vortex wave SAR motion error estimation method, an electromagnetic vortex wave amplitude phase weighted compensation function is designed, the influence of amplitude phase weighting of electromagnetic vortex waves in SAR echo recording on motion error estimation is removed, the problem of electromagnetic vortex wave SAR motion error estimation is effectively solved, electromagnetic vortex wave SAR accurate focusing can be achieved under the multi-platform carrying condition, and the electromagnetic vortex wave SAR motion error estimation accuracy is improved. Reference and reference are provided for future multi-platform carrying electromagnetic vortex wave SAR test and application.

Description

Technical Field

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

[0002] Synthetic aperture radar can complete observations all day and all weather, and is not affected by factors such as weather. As a new type of radar that carries orbital angular momentum and has a spiral phase wavefront, electromagnetic vortex wave radar can obtain more observation information when combined with the SAR system. However, when performing electromagnetic vortex wave SAR imaging, especially when the radar-carrying platform (for example: vehicle-mounted platform, airborne platform) cannot move completely along the ideal straight line trajectory, that is, when there is motion error, the imaging quality of electromagnetic vortex wave SAR will be affected. Unlike the traditional plane wave SAR motion error estimation and compensation, the electromagnetic vortex wave radar will be affected by the Bessel antenna pattern modulation and the additional vortex azimuth phase, which will produce additional amplitude weighting and phase modulation on the motion error estimation, affecting the estimation performance of the traditional motion error estimation method. Summary of the invention

[0003] In order to overcome at least one deficiency in the prior art, the present application provides an electromagnetic vortex wave SAR motion error estimation and compensation method.

[0004] In a first aspect, a method for estimating and compensating electromagnetic vortex wave SAR motion error is provided, comprising:

[0005] Performing range pulse compression on the echo signal of the scene target and dividing it into range blocks to obtain multiple range blocks;

[0006] Performing range motion correction on each range block to obtain a signal after range motion correction;

[0007] Dividing the signal after range migration correction into a plurality of sub-aperture data, wherein two adjacent sub-aperture data overlap;

[0008] Performing phase compensation on each sub-aperture data to obtain sub-aperture data after phase compensation;

[0009] Performing dechirp processing on the phase-compensated sub-aperture data to obtain a dechirp-processed signal; the dechirp-processed signal includes a plurality of distance units;

[0010] Sort multiple distance units according to energy intensity, and select several distance units with stronger energy;

[0011] The electromagnetic vortex wave phase gradient estimation kernel is used to estimate the phase gradient based on several distance units with stronger energy, and the electromagnetic vortex wave phase gradient estimation value of each sub-aperture data is obtained;

[0012] Perform full aperture synthesis according to the electromagnetic vortex wave phase gradient estimation value to obtain the full aperture phase gradient estimation result corresponding to each sub-range block; integrate the full aperture phase gradient estimation result corresponding to each sub-range block to obtain the full aperture motion phase error estimation result corresponding to each sub-range block; the full aperture motion phase error estimation results corresponding to all range blocks constitute the final full aperture motion phase error estimation result;

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

[0014] In one embodiment, performing phase compensation on each sub-aperture data to obtain phase-compensated sub-aperture data includes:

[0015] Performing azimuth Fourier transform on the sub-aperture data, multiplying it with the phase compensation function, and performing azimuth inverse Fourier transform to obtain sub-aperture data after phase compensation;

[0016] The phase compensation function is:

[0017]

[0018]

[0019]

[0020] Among them, H sub (f a ) is the phase compensation function, f a is the Doppler frequency, is the phase, l is the mode number, v is the speed of the radar platform, is the stationary point, x p For target X u Axis coordinate, y p For target Y u axis direction, λ is the wavelength of the transmitted signal, R B is the minimum slope distance.

[0021] In one embodiment, an electromagnetic vortex wave phase gradient estimation kernel is used to perform phase gradient estimation based on a number of distance units with stronger energy to obtain an electromagnetic vortex wave phase gradient estimation value for each sub-aperture data, using the following formula:

[0022]

[0023] in, is the estimated value of the phase gradient of the electromagnetic vortex wave, p is the index of the range block, n is the index of the sub-aperture data, k′ is the index of the azimuth coordinate of the sub-aperture data, m is the index of the selected range unit with stronger energy, M is the number of the selected range units with stronger energy, and h p,k′ is the weighting factor of the electromagnetic vortex wave Bessel function, conj is the conjugate operation, arg is the angle operation, s n (m, k′) is the signal of the k′th azimuth coordinate in the mth range unit with stronger energy selected by the nth sub-aperture data.

[0024] In one embodiment, full aperture synthesis is performed according to the electromagnetic vortex wave phase gradient estimation value to obtain a full aperture phase gradient estimation result corresponding to each sub-range block, including:

[0025] Subtracting the phase gradients of the electromagnetic vortex waves in the overlapping part of the data of two adjacent sub-apertures, performing linear fitting based on the subtraction result, and obtaining a linear fitting result;

[0026] The phase gradient of the electromagnetic vortex wave of the latter sub-aperture data of two adjacent sub-aperture data is subtracted from the linear fitting result to obtain the aligned sub-aperture data;

[0027] Take the first sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length is: sub is the data length of the sub-aperture data, and the last sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length, the middle of other sub-aperture data (1-α)·L sub The phase gradient of the electromagnetic vortex wave of the data length and the phase gradient estimation result of the full aperture corresponding to the synthetic sub-range block.

[0028] In a second aspect, an electromagnetic vortex wave SAR motion error estimation and compensation device is provided, comprising:

[0029] A distance block division module is used to perform distance pulse compression on the echo signal of the scene target and divide the distance blocks to obtain multiple distance blocks;

[0030] A range motion correction module is used to perform range motion correction on each range block to obtain a signal after range motion correction;

[0031] A sub-aperture division module is used to divide the signal after range migration correction into a plurality of sub-aperture data, and two adjacent sub-aperture data overlap;

[0032] A phase compensation module, used to perform phase compensation on each sub-aperture data to obtain sub-aperture data after phase compensation;

[0033] A dechirp processing module is used to perform dechirp processing on the sub-aperture data after phase compensation to obtain a dechirp-processed signal; the dechirp-processed signal includes a plurality of distance units;

[0034] A sorting module is used to sort multiple distance units according to energy intensity and select several distance units with stronger energy;

[0035] A phase gradient estimation module is used to use an electromagnetic vortex wave phase gradient estimation kernel to perform phase gradient estimation based on a number of distance units with stronger energy, so as to obtain an electromagnetic vortex wave phase gradient estimation value for each sub-aperture data;

[0036] A full-aperture synthesis module is used to perform full-aperture synthesis according to the electromagnetic vortex wave phase gradient estimation value to obtain the full-aperture phase gradient estimation result corresponding to each sub-range block; integrate the full-aperture phase gradient estimation result corresponding to each sub-range block to obtain the full-aperture motion phase error estimation result corresponding to each sub-range block; the full-aperture motion phase error estimation results corresponding to all range blocks constitute the final full-aperture motion phase error estimation result;

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

[0038] In one embodiment, the phase compensation module is further configured to:

[0039] Performing azimuth Fourier transform on the sub-aperture data, multiplying it with the phase compensation function, and performing azimuth inverse Fourier transform to obtain sub-aperture data after phase compensation;

[0040] The phase compensation function is:

[0041]

[0042]

[0043]

[0044] Among them, H sub (f a ) is the phase compensation function, f a is the Doppler frequency, is the phase, l is the mode number, v is the speed of the radar platform, is the stationary point, x p For target X u Axis coordinate, y p For target Yu axis direction, λ is the wavelength of the transmitted signal, R B is the minimum slope distance.

[0045] In one embodiment, the phase gradient estimation module is further used to obtain the electromagnetic vortex wave phase gradient estimation value of each sub-aperture data by using the following formula:

[0046]

[0047] in, is the estimated value of the phase gradient of the electromagnetic vortex wave, p is the index of the range block, n is the index of the sub-aperture data, k′ is the index of the azimuth coordinate of the sub-aperture data, m is the index of the selected range unit with stronger energy, M is the number of the selected range units with stronger energy, and h p,k′ is the weighting factor of the electromagnetic vortex wave Bessel function, conj is the conjugate operation, arg is the angle operation, s n (m, k′) is the signal of the k′th azimuth coordinate in the mth range unit with stronger energy selected by the nth sub-aperture data.

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

[0049] Subtracting the phase gradients of the electromagnetic vortex waves in the overlapping part of the data of two adjacent sub-apertures, performing linear fitting based on the subtraction result, and obtaining a linear fitting result;

[0050] The phase gradient of the electromagnetic vortex wave of the latter sub-aperture data of two adjacent sub-aperture data is subtracted from the linear fitting result to obtain the aligned sub-aperture data;

[0051] Take the first sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length is: sub is the data length of the sub-aperture data, and the last sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length, the middle of other sub-aperture data (1-α)·L sub The phase gradient of the electromagnetic vortex wave of the data length and the phase gradient estimation result of the full aperture corresponding to the synthetic sub-range block.

[0052] Compared with the prior art, the present application has the following beneficial effects: the electromagnetic vortex wave SAR motion error estimation and compensation method of the present application establishes a geometric model and a signal model of the electromagnetic vortex wave SAR motion error, designs a sub-aperture error estimation process, and solves the electromagnetic vortex wave SAR wide beam motion error estimation problem; designs an electromagnetic vortex wave amplitude-phase weighted compensation function, removes the influence of the amplitude-phase weighting of the electromagnetic vortex wave in SAR echo acquisition on the motion error estimation, effectively solves the electromagnetic vortex wave SAR motion error estimation problem, and can achieve precise focusing of the electromagnetic vortex wave SAR under multi-platform conditions, providing reference and reference for future multi-platform electromagnetic vortex wave SAR experiments and applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The present application may be better understood by referring to the following description given in conjunction with the accompanying drawings, which together with the following detailed description are included in this specification and form a part of this specification. In the drawings:

[0054] Figure 1 A flowchart of a method for estimating and compensating electromagnetic vortex wave SAR motion errors is shown;

[0055] Figure 2 The geometric model diagram of electromagnetic vortex wave SAR considering motion error is shown;

[0056] Figure 3 The electromagnetic vortex wave SAR imaging result diagram without motion error compensation is shown;

[0057] Figure 4 The electromagnetic vortex wave SAR imaging result diagram is shown without using the phase compensation function and the electromagnetic vortex wave weighted phase gradient estimation kernel for motion error estimation and compensation;

[0058] Figure 5 The electromagnetic vortex wave SAR imaging result diagram after the motion error estimation and compensation are performed using the method of the present application is shown;

[0059] Figure 6 The structural block diagram of the electromagnetic vortex wave SAR motion error estimation and compensation device is shown. DETAILED DESCRIPTION

[0060] The exemplary embodiments of the present application will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual embodiments are described in the specification. However, it should be understood that many implementation-specific decisions can be made in the process of developing any such actual embodiments in order to achieve the specific goals of the developer, and these decisions may vary from embodiment to embodiment.

[0061] It is also necessary to explain here that, in order to avoid obscuring the present application due to unnecessary details, only the device structure closely related to the scheme according to the present application is shown in the drawings, while other details that are not closely related to the present application are omitted.

[0062] It should be understood that the present application is not limited to the described implementation forms due to the following description with reference to the accompanying drawings. In this article, where feasible, the embodiments can be combined with each other, features between different embodiments can be replaced or borrowed, and one or more features can be omitted in one embodiment.

[0063] The present application embodiment provides an electromagnetic vortex wave SAR motion error estimation and compensation method, which is verified by simulation experiment. All steps and conclusions are verified correctness on MatlabR2017b. The parameters required for the simulation of the embodiment are shown in Table 1.

[0064] Table 1

[0065]

[0066]

[0067] The usage scenario of this embodiment is: this embodiment can be applied to vehicle-mounted and airborne electromagnetic vortex wave SAR imaging. The electromagnetic vortex wave SAR motion error geometric model and signal model are suitable for electromagnetic vortex wave radars mounted on a moving platform and working in SAR mode. This method solves the problem of electromagnetic vortex wave SAR being difficult to focus when there is motion error by establishing an electromagnetic vortex wave SAR motion error geometric signal model, designing sub-aperture error estimation and electromagnetic vortex wave amplitude phase weighted compensation function,

[0068] Figure 1 The flowchart of the electromagnetic vortex wave SAR motion error estimation and compensation method is shown in FIG. Figure 1 , methods include:

[0069] Step S1, performing range pulse compression on the echo signal of the scene target and dividing it into range blocks to obtain a plurality of range blocks.

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

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

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

[0073]

[0074]

[0075] in,

[0076] is the instantaneous slant range between the radar and the target, which includes the instantaneous slant range during the ideal flight trajectory The instantaneous slope 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 modulation signal with a modulation frequency of γ. The electromagnetic vortex wave SAR echo signal model s is established. r (t r ,t m ):

[0077]

[0078] Among them, t r is the fast time, c is the speed of light, J l (kasinθ(t a )) is the first kind Bessel function related to the mode 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] Perform range pulse compression on the echo signal, including performing range FFT, transforming to the range frequency domain, and comparing it with the range pulse compression function. Multiply the distance pulse pressure to obtain the signal envelope after the distance pulse pressure, where f r is the distance frequency. γ is the modulation frequency.

[0080] Considering that the electromagnetic vortex wave amplitude and phase modulation introduced by the electromagnetic vortex wave radar working in SAR mode varies with the distance, the echo data after the range pulse compression is divided into P = 5 range blocks. The division criterion is that within the range block, the spatial variation of the electromagnetic vortex wave amplitude and phase modulation can be ignored.

[0081] Step S2, performing range migration correction on each range block to obtain a signal after range migration correction.

[0082] Step S3: Divide the signal after range migration correction into a plurality of sub-aperture data, and two adjacent sub-aperture data overlap.

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

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

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

[0086] The phase compensation function is:

[0087]

[0088]

[0089]

[0090] Among them, H sub (f a ) is the phase compensation function, f a is the Doppler frequency, is the phase, l is the mode number, v is the speed of the radar platform, is the stationary point, x p For target X u Axis coordinate, y p For target Y u axis direction, λ is the wavelength of the transmitted signal, R B is the minimum slope distance.

[0091] Step S5, performing dechirp processing on the phase-compensated sub-aperture data to obtain a dechirp-processed signal; the dechirp-processed signal includes a plurality of distance units. The dechirp processing is used to remove the frequency modulation effect caused by the speed or distance change, thereby extracting the required target information.

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

[0093] Step S6, sorting the multiple distance units according to energy intensity, and selecting several distance units with stronger energy.

[0094] Here, for example, the first 20% of the distance units in the sorting result can be used as several distance units with stronger energy, or the distance units with energy intensity greater than a set threshold can be used as several distance units with stronger energy. Then, a frequency shift function is constructed to move several distance units with stronger energy to the center of the sub-aperture and extract them by windowing, and then the next step of phase gradient estimation is performed.

[0095] Step S7, using the electromagnetic vortex wave phase gradient estimation kernel to perform phase gradient estimation based on a number of distance units with stronger energy, to obtain an electromagnetic vortex wave phase gradient estimation value for each sub-aperture data.

[0096] Specifically, the following formula is used:

[0097]

[0098] in, is the estimated value of the phase gradient of the electromagnetic vortex wave, p is the index of the range block, n is the index of the sub-aperture data, k′ is the index of the azimuth coordinate of the sub-aperture data, m is the index of the selected range unit with stronger energy, M is the number of the selected range units with stronger energy, and h p，k′ is the weighting factor of the electromagnetic vortex wave Bessel function, conj is the conjugate operation, arg is the angle operation, s n (m, k′) is the signal of the k′th azimuth coordinate in the mth range unit with stronger energy selected by the nth sub-aperture data.

[0099] Specifically, the electromagnetic vortex wave Bessel function weighting factor h p，k′ :

[0100]

[0101]

[0102] Among them, J l (kasinθ(t sub (k′))) is the first kind of Bessel function related to the mode number l, k is the wave number, a is the array radius, α(t sub (k′) is t sub (k′) is the instantaneous pitch angle at time t sub (k′) is the discrete time of the subaperture azimuth, R0(t sub (k′) is t sub The instantaneous slope distance at time (k′). ΔX r (t sub (k′) is t sub The radar platform deviates from the ideal motion trajectory at time (k′) u Axis position error.

[0103] Step S8, performing full aperture synthesis according to the electromagnetic vortex wave phase gradient estimation value to obtain the full aperture phase gradient estimation result corresponding to each sub-range block; integrating the full aperture phase gradient estimation result corresponding to each sub-range block to obtain the full aperture motion phase error estimation result corresponding to each sub-range block; the full aperture motion phase error estimation results corresponding to all range blocks constitute the final full aperture motion phase error estimation result.

[0104] Specifically, full aperture synthesis is performed according to the electromagnetic vortex wave phase gradient estimation value to obtain the full aperture phase gradient estimation result corresponding to each sub-range block, including:

[0105] Subtracting the phase gradients of the electromagnetic vortex waves in the overlapping part of the data of two adjacent sub-apertures, performing linear fitting based on the subtraction result, and obtaining a linear fitting result;

[0106] The phase gradient of the electromagnetic vortex wave of the latter sub-aperture data of two adjacent sub-aperture data is subtracted from the linear fitting result to obtain the aligned sub-aperture data;

[0107] Take the first sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length is: sub is the data length of the sub-aperture data, and the last sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length, the middle of other sub-aperture data (1-α)·L sub The phase gradient of the electromagnetic vortex wave of the data length and the phase gradient estimation result of the full aperture corresponding to the synthetic sub-range block.

[0108] Step S9, using the final full-aperture motion phase error estimation result to compensate the echo signal after the range pulse compression to obtain a compensated signal; performing range migration correction and azimuth matching filtering on the compensated signal to obtain a focused image.

[0109] In this embodiment, a geometric model and signal model of electromagnetic vortex wave SAR motion error are established, and a sub-aperture error estimation process is designed to solve the problem of electromagnetic vortex wave SAR wide beam motion error estimation; an electromagnetic vortex wave amplitude-phase weighted compensation function is designed to remove the influence of the amplitude-phase weighting of the electromagnetic vortex wave in SAR echo acquisition on the motion error estimation, effectively solving the problem of electromagnetic vortex wave SAR motion error estimation, and achieving precise focusing of the electromagnetic vortex wave SAR under multi-platform conditions, providing a reference and reference for future multi-platform electromagnetic vortex wave SAR experiments and applications.

[0110] Figure 2 The geometric model diagram of electromagnetic eddy wave SAR considering motion error is shown. Figure 3 The electromagnetic vortex wave SAR imaging result without motion error compensation is shown. It can be seen that when there is motion error, the electromagnetic vortex wave SAR cannot complete imaging focusing and the image is severely defocused. Figure 4The electromagnetic vortex wave SAR imaging result diagram without using phase compensation function and electromagnetic vortex wave weighted phase gradient estimation kernel for motion error estimation and compensation is shown. It can be seen that the imaging result has defocusing and sidelobe lifting, which makes the main lobe energy unfocused. This is because the traditional SAR motion error estimation method does not take into account the Bessel antenna pattern modulation and vortex azimuth additional phase introduced by electromagnetic vortex wave SAR. The vortex azimuth additional phase is mixed into the motion error estimation result during phase error estimation, and the Bessel antenna pattern weights the phase error, resulting in inaccurate phase gradient estimation kernel estimation, making it impossible to complete accurate imaging.

[0111] Figure 5 The figure shows the electromagnetic vortex wave SAR imaging result after motion error estimation and compensation using the method of the present application. The method of the present application fully considers the influence of the electromagnetic vortex wave on the motion error estimation, designs a phase compensation function and a Bessel weighted phase gradient estimation kernel of the electromagnetic vortex wave SAR, realizes the accurate estimation of the electromagnetic vortex wave SAR motion error, and finally realizes the accurate imaging of the electromagnetic vortex wave SAR when the motion trajectory of the carrying 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 structure block diagram of the electromagnetic vortex wave SAR motion error estimation and compensation device is shown, including:

[0113] The distance block division module 61 is used to perform distance pulse compression on the echo signal of the scene target and perform distance block division to obtain a plurality of distance blocks;

[0114] A range motion correction module 62, used to perform range motion correction on each range block to obtain a signal after range motion correction;

[0115] A sub-aperture division module 63, used to divide the signal after range migration correction into a plurality of sub-aperture data, and two adjacent sub-aperture data overlap;

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

[0117] A dechirp processing module 65 is used to perform dechirp processing on the sub-aperture data after phase compensation to obtain a dechirp-processed signal; the dechirp-processed signal includes a plurality of distance units;

[0118] A sorting module 66, for sorting the multiple distance units according to energy intensity, and selecting a number of distance units with stronger energy;

[0119] A phase gradient estimation module 67 is used to use an electromagnetic vortex wave phase gradient estimation kernel to perform phase gradient estimation based on a number of distance units with stronger energy, so as to obtain an electromagnetic vortex wave phase gradient estimation value for each sub-aperture data;

[0120] The full aperture synthesis module 68 is used to perform full aperture synthesis according to the electromagnetic vortex wave phase gradient estimation value to obtain the full aperture phase gradient estimation result corresponding to each sub-range block; integrate the full aperture phase gradient estimation result corresponding to each sub-range block to obtain the full aperture motion phase error estimation result corresponding to each sub-range block; the full aperture motion phase error estimation results corresponding to all range blocks constitute the final full aperture motion phase error estimation result;

[0121] The compensation module 69 is used to compensate the echo signal after the range pulse compression with the final full-aperture motion phase error estimation result to obtain a compensated signal; perform range migration correction and azimuth matching filtering on the compensated signal to obtain a 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 mentioned above. Therefore, the specific implementation method of the device can be seen in the embodiment part of the electromagnetic vortex wave SAR motion error estimation and compensation method mentioned above, and its technical effect corresponds to the technical effect of the above method, which will not be repeated here.

[0123] The above are only various implementations of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for estimating and compensating electromagnetic vortex wave SAR motion error, characterized in that: include: Performing range pulse compression on the echo signal of the scene target and dividing it into range blocks to obtain multiple range blocks; Performing range motion correction on each range block to obtain a signal after range motion correction; Dividing the range migration corrected signal into a plurality of sub-aperture data, wherein two adjacent sub-aperture data overlap; Performing phase compensation on each sub-aperture data to obtain sub-aperture data after phase compensation; Performing dechirp processing on the phase-compensated sub-aperture data to obtain a dechirp-processed signal; The dechirp processed signal includes a plurality of distance units; sorting the plurality of distance units according to energy intensity, and selecting a number of distance units with stronger energy; Using an electromagnetic vortex wave phase gradient estimation kernel to perform phase gradient estimation based on the plurality of distance units with stronger energy, to obtain an electromagnetic vortex wave phase gradient estimation value for each sub-aperture data; Performing full aperture synthesis according to the electromagnetic vortex wave phase gradient estimation value to obtain a full aperture phase gradient estimation result corresponding to each sub-range block; integrating the full aperture phase gradient estimation result corresponding to each sub-range block to obtain a full aperture motion phase error estimation result corresponding to each sub-range block; The full-aperture motion phase error estimation results corresponding to all range blocks constitute the final full-aperture motion phase error estimation result; Using the final full-aperture motion phase error estimation result to compensate the echo signal after the range pulse pressure to obtain a compensated signal; The compensated signal is subjected to range migration correction and azimuth matching filtering to obtain a focused image.

2. The method according to claim 1, characterized in that in, Perform phase compensation on each sub-aperture data to obtain sub-aperture data after phase compensation, including: Performing azimuth Fourier transform on the sub-aperture data, multiplying it with a phase compensation function, and performing azimuth inverse Fourier transform to obtain phase-compensated sub-aperture data; The phase compensation function is: Among them, H sub (f a ) is the phase compensation function, f a is the Doppler frequency, is the phase, l is the mode number, v is the speed of the radar platform, is the stationary point, x p For target X u Coordinate in the y-axis direction p For target Y u axis direction, λ is the wavelength of the transmitted signal, R B is the minimum slope distance.

3. The method according to claim 1, characterized in that in, The electromagnetic vortex wave phase gradient estimation kernel is used to perform phase gradient estimation based on the several distance units with stronger energy to obtain the electromagnetic vortex wave phase gradient estimation value of each sub-aperture data, using the following formula: in, is the estimated value of the phase gradient of the electromagnetic vortex wave, p is the index of the range block, n is the index of the sub-aperture data, k′ is the index of the azimuth coordinate of the sub-aperture data, m is the index of the selected range unit with stronger energy, M is the number of the selected range units with stronger energy, and h p,k′ is the weighting factor of the electromagnetic vortex wave Bessel function, conj is the conjugate operation, arg is the angle operation, s n (m, k′) is the signal of the k′th azimuth coordinate in the mth range unit with stronger energy selected by the nth sub-aperture data.

4. The method according to claim 1, characterized in that in, Full aperture synthesis is performed according to the electromagnetic vortex wave phase gradient estimation value to obtain a full aperture phase gradient estimation result corresponding to each sub-range block, including: Subtracting the phase gradients of the electromagnetic vortex waves in the overlapping part of the data of two adjacent sub-apertures, performing linear fitting based on the subtraction result, and obtaining a linear fitting result; Subtracting the linear fitting result from the electromagnetic vortex wave phase gradient of the latter subaperture data of two adjacent subaperture data to obtain aligned subaperture data; Take the first sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length is: sub is the data length of the sub-aperture data, and the last sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length, the middle of other sub-aperture data (1-α)·L sub The phase gradient of the electromagnetic vortex wave of the data length is synthesized to estimate the phase gradient of the full aperture corresponding to the sub-range block.

5. An electromagnetic vortex wave SAR motion error estimation and compensation device, characterized in that: include: A distance block division module is used to perform distance pulse compression on the echo signal of the scene target and divide the distance blocks to obtain multiple distance blocks; A range motion correction module is used to perform range motion correction on each range block to obtain a signal after range motion correction; A sub-aperture division module, used for dividing the signal after the range migration correction into a plurality of sub-aperture data, and two adjacent sub-aperture data overlap; A phase compensation module, used to perform phase compensation on each sub-aperture data to obtain sub-aperture data after phase compensation; A dechirp processing module, used for performing dechirp processing on the sub-aperture data after phase compensation to obtain a dechirp-processed signal; The dechirp processed signal includes a plurality of distance units; A sorting module, used to sort the multiple distance units according to energy intensity and select several distance units with stronger energy; A phase gradient estimation module, used to use an electromagnetic vortex wave phase gradient estimation kernel to perform phase gradient estimation based on the plurality of distance units with stronger energy, so as to obtain an electromagnetic vortex wave phase gradient estimation value for each sub-aperture data; A full-aperture synthesis module is used to perform full-aperture synthesis according to the electromagnetic vortex wave phase gradient estimation value to obtain a full-aperture phase gradient estimation result corresponding to each sub-range block; integrate the full-aperture phase gradient estimation result corresponding to each sub-range block to obtain a full-aperture motion phase error estimation result corresponding to each sub-range block; The full-aperture motion phase error estimation results corresponding to all range blocks constitute the final full-aperture motion phase error estimation result; A compensation module, used to compensate the echo signal after the range pulse pressure by using the final full-aperture motion phase error estimation result to obtain a compensated signal; The compensated signal is subjected to range migration correction and azimuth matching filtering to obtain a focused image.

6. The device according to claim 5, characterized in that The phase compensation module is also used for: Performing azimuth Fourier transform on the sub-aperture data, multiplying it with a phase compensation function, and performing azimuth inverse Fourier transform to obtain phase-compensated sub-aperture data; The phase compensation function is: Among them, H sub (f a ) is the phase compensation function, f a is the Doppler frequency, is the phase, l is the mode number, v is the speed of the radar platform, is the stationary point, x p For target X u Coordinate in the y-axis direction p For target Y u axis direction, λ is the wavelength of the transmitted signal, P B is the minimum slope distance.

7. The device according to claim 5, characterized in that The phase gradient estimation module is also used to obtain the electromagnetic vortex wave phase gradient estimation value of each sub-aperture data using the following formula: in, is the estimated value of the phase gradient of the electromagnetic vortex wave, p is the index of the range block, n is the index of the sub-aperture data, k′ is the index of the azimuth coordinate of the sub-aperture data, m is the index of the selected range unit with stronger energy, M is the number of the selected range units with stronger energy, and h p,k′ is the weighting factor of the electromagnetic vortex wave Bessel function, conj is the conjugate operation, arg is the angle operation, s n (m, k′) is the signal of the k′th azimuth coordinate in the mth range unit with stronger energy selected by the nth sub-aperture data.

8. The device according to claim 5, characterized in that The full aperture synthesis module is further used for: Subtracting the phase gradients of the electromagnetic vortex waves in the overlapping part of the data of two adjacent sub-apertures, performing linear fitting based on the subtraction result, and obtaining a linear fitting result; Subtracting the linear fitting result from the electromagnetic vortex wave phase gradient of the latter subaperture data of two adjacent subaperture data to obtain aligned subaperture data; Take the first sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length is: sub is the data length of the sub-aperture data, and the last sub-aperture data The phase gradient of the electromagnetic vortex wave of the data length, the middle of other sub-aperture data (1-α)·L sub The phase gradient of the electromagnetic vortex wave of the data length is synthesized to estimate the phase gradient of the full aperture corresponding to the sub-range block.

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