Sea surface current field inversion method and device based on electromagnetic vortex wave radar data

Abstract

This application relates to the fields of SAR signal processing and marine remote sensing applications, and provides a method and apparatus for sea surface current field inversion based on electromagnetic vortex wave radar data. The method determines the Doppler spectrum using electromagnetic vortex wave radar image data, obtains the measured frequency position of the trough feature point in the Doppler spectrum, and determines the theoretical frequency position using the position and angle of the two main lobes and the angle of the trough feature point in the radar antenna pattern. Then, the difference between the measured frequency position and the theoretical frequency position is used to obtain the anomalous frequency offset. Next, the Doppler frequency offset caused by wind and wave motion is removed from this anomalous frequency offset to obtain the target Doppler frequency offset. Finally, the radial velocity of the sea surface is calculated using the Doppler frequency offset, thus realizing sea surface current field inversion. This effectively expands the applicability of the Doppler frequency shift-based ocean current inversion method and improves the application potential of electromagnetic vortex wave radar in sea surface current field detection.

Description

Technical Field

[0001] This application relates to the fields of SAR signal processing and marine remote sensing application technology, and in particular to a method and apparatus for inverting sea surface current fields based on electromagnetic vortex wave radar data. Background Technology

[0002] Ocean currents are important dynamic parameters characterizing ocean material transport and energy exchange processes. They have significant scientific and applied value for studying global climate change, maintaining marine ecological balance, promoting the sustainable use of marine resources, and supporting human socio-economic development.

[0003] Synthetic Aperture Radar (SAR), as an active microwave remote sensing method, is one of the important technical approaches for observing sea surface current fields. Related techniques typically invert the radial current field at the sea surface by analyzing the anomalous offset between the observed Doppler centroid values ​​of radar images and the theoretical Doppler centroid values ​​calculated based on the radar platform's orbital parameters and motion attitude. These methods are usually based on plane-wave radar, whose Doppler spectrum exhibits an approximately Gaussian distribution under ideal conditions, allowing the estimated Doppler centroid to be estimated from the spectral peak positions.

[0004] In recent years, with the continuous development of electromagnetic vortex wave theory and antenna technology, electromagnetic vortex waves carrying orbital angular momentum have been gradually introduced into the field of radar imaging. Compared with traditional plane wave radar, electromagnetic vortex wave radar has a helical wavefront structure and special antenna pattern characteristics, showing potential advantages in target detection and imaging. However, due to the more complex antenna pattern and imaging characteristics of electromagnetic vortex wave radar, the Doppler spectrum corresponding to its imaging data usually exhibits multi-peak, non-Gaussian distribution characteristics, making it impossible to directly estimate the Doppler centroid observation value using the peak values. Therefore, for electromagnetic vortex wave radar data, a new sea surface current field inversion technique needs to be proposed to effectively extract sea surface current field information from electromagnetic vortex wave radar imaging data. Summary of the Invention

[0005] In view of this, the present application provides a method and apparatus for inverting sea surface current field based on electromagnetic vortex wave radar data, in order to solve the problem in the prior art that when the radar system uses vortex waves, the position offset of the spectral peak cannot be directly used to invert the sea surface current field.

[0006] A first aspect of this application provides a method for inverting sea surface current fields based on electromagnetic vortex wave radar data, comprising:

[0007] Acquire electromagnetic vortex wave radar image data and electromagnetic vortex wave radar antenna pattern;

[0008] The Doppler spectrum is determined based on electromagnetic vortex wave radar image data, and the measurement frequency position of the trough feature point in the Doppler spectrum is determined; wherein, the trough feature point is the trough point between the first main lobe and the second main lobe in the Doppler spectrum;

[0009] Obtain the position and angle of the first and second main lobes in the electromagnetic vortex wave radar antenna pattern, as well as the angle of the valley feature point in the electromagnetic vortex wave radar antenna pattern.

[0010] The theoretical frequency position of the trough feature point in the Doppler spectrum is determined based on the position and angle of the two main lobes and the angle of the trough feature point.

[0011] The difference between the measured frequency location and the theoretical frequency location is determined as the abnormal frequency offset;

[0012] Determine the Doppler frequency shift caused by wind and wave motion, and determine the difference between the abnormal frequency shift and the Doppler frequency shift caused by wind and wave motion as the target Doppler frequency shift.

[0013] The radial velocity of the sea surface is calculated using the target Doppler frequency offset, thus realizing the inversion of the sea surface flow field.

[0014] A second aspect of this application provides a sea surface current field inversion device based on electromagnetic vortex wave radar data, comprising:

[0015] The acquisition module is configured to acquire electromagnetic vortex wave radar image data and electromagnetic vortex wave radar antenna pattern.

[0016] The measurement location determination module is configured to determine the Doppler spectrum based on electromagnetic vortex wave radar image data, and to determine the measurement frequency location of the trough feature point in the Doppler spectrum; wherein, the trough feature point is the trough point between the first main lobe and the second main lobe in the Doppler spectrum;

[0017] The acquisition module is also configured to acquire the position and angle of the first main lobe and the second main lobe in the electromagnetic vortex wave radar antenna pattern, as well as the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern.

[0018] The theoretical position determination module is configured to determine the theoretical frequency position of the trough feature point in the Doppler spectrum based on the position and angle of the two main lobes and the angle of the trough feature point.

[0019] The abnormal offset determination module is configured to determine the difference between the measured frequency position and the theoretical frequency position as the abnormal frequency offset;

[0020] The target offset determination module is configured to determine the Doppler frequency offset caused by wind and wave motion, and to determine the difference between the abnormal frequency offset and the Doppler frequency offset caused by wind and wave motion as the target Doppler frequency offset.

[0021] The inversion module is configured to calculate the radial velocity of the sea surface using the target Doppler frequency offset, thereby realizing the inversion of the sea surface flow field.

[0022] A third aspect of this application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method.

[0023] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0024] The beneficial effects of the embodiments in this application compared with the prior art are:

[0025] This application embodiment determines the Doppler spectrum using electromagnetic vortex wave radar image data, obtains the measured frequency position of the trough feature point in the Doppler spectrum, and determines the theoretical frequency position of the trough feature point in the electromagnetic vortex wave radar antenna pattern using the position and angle of the two main lobes and the angle of the trough feature point. Then, the difference between the measured frequency position and the theoretical frequency position is used to obtain the abnormal frequency offset. The Doppler frequency offset caused by wind and wave motion is then removed from the abnormal frequency offset to obtain the target Doppler frequency offset. Finally, the radial velocity of the sea surface is calculated using the Doppler frequency offset to achieve sea surface current field inversion. This effectively expands the applicability of the Doppler frequency shift-based ocean current inversion method and improves the application potential of electromagnetic vortex wave radar in sea surface current field detection. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating a sea surface current field inversion method based on electromagnetic vortex wave radar data provided in this application embodiment.

[0028] Figure 2 This is a schematic diagram of a Doppler spectrum provided in an embodiment of this application.

[0029] Figure 3 This is a schematic diagram of a radar antenna radiation pattern provided in an embodiment of this application.

[0030] Figure 4 This is a schematic diagram showing the result of sea surface current field inversion using the technical solution provided in the embodiments of this application.

[0031] Figure 5 This is a schematic diagram of a sea surface current field inversion device based on electromagnetic vortex wave radar data provided in an embodiment of this application.

[0032] Figure 6 This is a schematic diagram of the electronic device provided in the embodiments of this application. Detailed Implementation

[0033] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0034] The following will describe in detail, with reference to the accompanying drawings, a method and apparatus for inverting sea surface current fields based on electromagnetic vortex wave radar data according to embodiments of this application.

[0035] As mentioned above, current sea surface current field inversion methods based on synthetic aperture radar (SAR) Doppler information are mainly designed for plane wave radar imaging systems. Under ideal conditions, the Doppler spectrum of a plane wave radar exhibits a single-peak, approximately Gaussian distribution. During the current field inversion process, the observed Doppler centroid is typically estimated using the position of the spectral peak. Then, the theoretical value caused by the radar platform's orbital parameters and motion attitude is subtracted from the observed Doppler centroid value to obtain the Doppler frequency shift related to sea surface motion.

[0036] However, when radar systems employ vortex waves, the spiral wavefront structure of electromagnetic vortex waves results in significant differences in radar antenna patterns and imaging mechanisms compared to traditional plane wave radars. This leads to complex characteristics in their Doppler spectra, such as multi-peak, non-Gaussian distributions. In this case, it is impossible to directly invert the sea surface current field using the positional shift of the spectral peaks.

[0037] Therefore, this application provides a sea surface current field inversion method based on electromagnetic vortex wave radar data. By combining the morphological characteristics of the azimuth pattern of the vortex wave radar antenna, Doppler spectrum feature points are found, and then the Doppler anomaly offset of these feature points is estimated. This anomaly offset reflects the characteristics of sea surface motion and can therefore be used to achieve sea surface current field inversion. This method improves the applicability of electromagnetic vortex wave radar in sea surface current field detection.

[0038] Figure 1 This is a schematic flowchart illustrating a sea surface current field inversion method based on electromagnetic vortex wave radar data provided in an embodiment of this application. Figure 1 As shown, the method includes the following steps:

[0039] In step S101, electromagnetic vortex wave radar image data and electromagnetic vortex wave radar antenna pattern are acquired.

[0040] In step S102, the Doppler spectrum is determined based on the electromagnetic vortex wave radar image data, and the measurement frequency position of the trough feature point is determined in the Doppler spectrum.

[0041] Among them, the trough feature point is the trough point between the first main lobe and the second main lobe in the Doppler spectrum.

[0042] In step S103, the positions and angles of the first and second main lobes in the electromagnetic vortex wave radar antenna pattern, as well as the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern, are obtained; based on the positions and angles of the two main lobes and the angle of the trough feature point, the theoretical frequency position of the trough feature point in the Doppler spectrum is determined.

[0043] In step S104, the difference between the measured frequency position and the theoretical frequency position is determined as the abnormal frequency offset.

[0044] In step S105, the Doppler frequency shift caused by the wind and wave motion is determined, and the difference between the abnormal frequency shift and the Doppler frequency shift caused by the wind and wave motion is determined as the target Doppler frequency shift.

[0045] In step S106, the radial velocity of the sea surface is calculated using the target Doppler frequency offset, thereby realizing the inversion of the sea surface flow field.

[0046] In some embodiments of this application, the method may be executed by a server or by a terminal device with certain processing capabilities.

[0047] In some embodiments of this application, electromagnetic vortex wave radar image data and electromagnetic vortex wave radar antenna pattern can be acquired first. Then, on the one hand, the Doppler spectrum can be determined based on the electromagnetic vortex wave radar image data, and the measurement frequency position of the trough feature point can be determined in the Doppler spectrum. On the other hand, the position and angle of the first main lobe and the second main lobe in the electromagnetic vortex wave radar azimuth antenna pattern, as well as the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern, can be acquired.

[0048] Among them, the electromagnetic vortex wave radar antenna pattern refers to the azimuth antenna pattern of the electromagnetic vortex wave radar receiving the far field.

[0049] In some embodiments of this application, the theoretical frequency position of the trough feature point in the Doppler spectrum can be determined based on the positions and angles of the two main lobes and the angle of the trough feature point. Furthermore, the difference between the measured frequency position and the theoretical frequency position can be determined as the abnormal frequency offset. The positions of the two main lobes can be the corresponding frequency positions of the two main lobes in the Doppler spectrum.

[0050] In some embodiments of this application, the Doppler frequency shift caused by wind and wave motion can be determined, and the difference between the abnormal frequency shift and the Doppler frequency shift caused by wind and wave motion can be used as the target Doppler frequency shift. Finally, the radial velocity of the sea surface can be calculated using the target Doppler frequency shift, thus realizing the inversion of the sea surface current field.

[0051] According to the technical solution provided in the embodiments of this application, the Doppler spectrum is determined by using electromagnetic vortex wave radar image data. The measured frequency position of the trough feature point is obtained in the Doppler spectrum, and the theoretical frequency position of the trough feature point is determined by using the position and angle of the two main lobes and the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern. Then, the difference between the measured frequency position and the theoretical frequency position is used to obtain the abnormal frequency offset. The Doppler frequency offset caused by wind and wave motion is then removed from the abnormal frequency offset to obtain the target Doppler frequency offset. Finally, the radial velocity of the sea surface is calculated using the Doppler frequency offset to realize the inversion of the sea surface current field. This effectively expands the applicability of the Doppler frequency shift-based ocean current inversion method and improves the application potential of electromagnetic vortex wave radar in sea surface current field detection.

[0052] In some embodiments of this application, electromagnetic vortex wave radar image data can be determined in the following manner: acquiring raw electromagnetic vortex wave radar data; performing imaging processing on the raw electromagnetic vortex wave radar data to obtain complex electromagnetic vortex wave radar image data; performing Doppler zeroing processing on the complex electromagnetic vortex wave radar image data based on the flight inertial navigation data of the radar flight platform to obtain electromagnetic vortex wave radar image data; the electromagnetic vortex wave radar image data is radar image complex data that has eliminated the theoretical Doppler shift caused by the motion and attitude of the radar flight platform.

[0053] In other words, the raw data of the electromagnetic vortex wave radar can be acquired first, and then image processing can be performed on this raw data to obtain complex electromagnetic vortex wave radar image data. Next, based on the flight inertial navigation data of the radar flight platform, Doppler zeroing processing is performed on the obtained complex electromagnetic vortex wave radar image data to eliminate the theoretical Doppler shift caused by the motion and attitude of the radar flight platform, thus obtaining preprocessed complex radar image data. This complex radar image data will serve as the basis for subsequent Doppler spectrum calculations.

[0054] In some embodiments of this application, determining the Doppler spectrum based on electromagnetic vortex wave radar image data may include: performing a Fourier transform on the electromagnetic vortex wave radar image data in the azimuth direction to obtain the azimuth power spectrum; and averaging the azimuth power spectrum along the range direction to obtain the Doppler spectrum.

[0055] The Fourier transform of the electromagnetic vortex wave radar image data in the azimuth direction can be expressed as follows: ; This refers to electromagnetic vortex wave radar image data, i.e., the radar image complex data after the above preprocessing. , , This represents the number of echo points in the azimuth direction. arrive All are distance units, and Greater than .

[0056] Averaging the power spectrum in the azimuth direction along the distance can be expressed as: ;in, For the Doppler spectrum, For the first The Doppler spectrum of a distance unit.

[0057] Figure 2 This is a schematic diagram of a Doppler spectrum provided in an embodiment of this application. For example... Figure 2 As shown, the horizontal axis of the Doppler spectrum represents frequency in Hertz (Hz), and the vertical axis represents amplitude in decibels (dB).

[0058] In some embodiments of this application, determining the measurement frequency position of a trough feature point in the Doppler spectrum may include: performing morphological analysis on the Doppler spectrum to identify the first main lobe and the second main lobe; determining the lowest amplitude point between the first main lobe and the second main lobe as the trough feature point; and determining the frequency value of the trough feature point as the measurement frequency position.

[0059] In other words, morphological analysis can be performed on the calculated Doppler spectrum to identify the number of peaks, peak distribution characteristics, etc. Among them, peak distribution characteristics can include the positional distribution characteristics of the peaks, such as whether the peaks are located on both sides of the center of the spectrum, whether the peaks are approximately symmetrically distributed, etc. Peak distribution characteristics can also include the amplitude distribution of the peaks, such as the amplitude of the largest peak, the second largest peak, and whether the amplitudes of the left and right peaks are close, etc.

[0060] Based on the morphological analysis results, the first and second main lobes can be identified. Furthermore, the lowest amplitude point between the first and second main lobes is determined as the trough feature point. Finally, the frequency value of this trough feature point in the Doppler spectrum is recorded as the measurement frequency position. .

[0061] In some embodiments of this application, the theoretical frequency location of the trough feature point can also be determined using the antenna pattern of an electromagnetic vortex wave radar. .

[0062] In some implementations, the theoretical frequency position of the trough feature point in the Doppler spectrum can be determined as follows: the difference in angle between the two main lobes is determined as the angle width; the difference in the corresponding frequencies of the two main lobes in the Doppler spectrum is determined as the frequency width; the ratio of the angle of the trough feature point to the angle width is calculated; and the product of the ratio and the frequency width is determined as the theoretical frequency position of the trough feature point in the Doppler spectrum.

[0063] Figure 3 This is a schematic diagram of an antenna radiation pattern provided in an embodiment of this application. For example... Figure 3 As shown, the horizontal axis of the antenna pattern represents angle in degrees (deg), and the vertical axis represents amplitude in dB.

[0064] The first and second main lobes can be found in the antenna pattern, and their corresponding frequency positions in the Doppler spectrum can be denoted as follows: and The angular positions in the antenna pattern are denoted as follows: and Furthermore, the trough feature point between the first and second main lobes can be found, and its angular position in the antenna pattern can be denoted as... .

[0065] The angular width between the two main lobes can be calculated. And calculate the frequency width between the two main lobes. Alternatively, the angular width between the two main lobes can be calculated. At this time, the frequency width between the two main lobes Then, based on the linear mapping relationship between the antenna pattern angular domain and the Doppler frequency domain, the angular position of the mid-valley feature point in the main lobe of the antenna pattern is converted into its theoretical frequency position in the Doppler spectrum. .

[0066] In the calculation and Then, the difference between the two can be used as the abnormal frequency offset. ,Right now .

[0067] The abnormal frequency offset obtained at this time In addition to the Doppler shift caused by sea surface currents, the Doppler shift also includes that caused by wind and wave motion. Therefore, it is necessary to calculate the Doppler frequency shift caused by wind and wave motion. , from the abnormal frequency offset After removing the middle part, the true Doppler frequency shift is obtained, and then the sea surface current field is inverted based on it.

[0068] In some embodiments of this application, determining the Doppler frequency shift caused by wind and wave motion may include: acquiring background wind field data corresponding to electromagnetic vortex wave radar image data; and calculating the Doppler frequency shift caused by wind and wave motion using an empirical Doppler model based on the background wind field data and radar parameters. The empirical Doppler model may be an empirical geophysical model function, and the corresponding empirical Doppler model can be selected according to the electromagnetic vortex wave band.

[0069] For example, if the electromagnetic vortex wave is in the C-band, the C-band Empirical Doppler Frequency (CDOP) model can be used to calculate the Doppler frequency shift caused by wind and wave motion. Similarly, if the electromagnetic vortex wave is in the X-band, the X-band Empirical Doppler Frequency (XDOP) model can be used to calculate the Doppler frequency shift caused by wind and wave motion. And so on, which will not be elaborated further here.

[0070] For ease of description and explanation, the following explanation will use electromagnetic vortex waves as the C-band and the empirical Doppler model as CDOP.

[0071] Among them, the Doppler frequency shift caused by wind and wave motion is calculated using the CDOP model. It can be represented as .

[0072] Among them, the function ; ; ; ; , , , , , , , , , , , , and These are all preset coefficients of the model, and their values ​​can be determined through experimental fitting. and All of these took into account the wind direction along the radar's line of sight. , , The wind speed is 10 meters above the sea surface. The incident angle of the radar wave.

[0073] In some embodiments of this application, after determining Then, further steps can be taken using formulas. The radial velocity at the sea surface was calculated. ;in, This is the abnormal frequency offset. This represents the Doppler frequency shift caused by wind and wave motion. The wavenumber is the incident wave number of the radar. The technical solution provided in this application first performs Doppler spectrum analysis on the electromagnetic vortex wave radar image data. Under multi-peak Doppler spectrum conditions, and considering the morphological characteristics of the antenna pattern in the azimuth direction of the electromagnetic vortex wave radar antenna, Doppler spectrum feature points are selected. Then, based on the frequency difference between the actual and theoretical frequency positions of the feature points in the Doppler spectrum, the Doppler anomaly frequency shift caused by sea surface motion is obtained. Finally, the sea surface radial current velocity is inverted based on the Doppler anomaly frequency shift.

[0074] In other words, the technical solution provided in this application addresses the characteristic of the Doppler spectrum in electromagnetic vortex wave radar image data exhibiting a multi-peak, non-Gaussian distribution. By combining the antenna pattern of the electromagnetic vortex wave radar, the characteristic points of the multi-peak Doppler spectrum are determined, thereby realizing the inversion of the sea surface current field under the electromagnetic vortex wave radar imaging system.

[0075] Figure 4 This is a schematic diagram illustrating the results of sea surface current field inversion using the technical solution provided in the embodiments of this application. Figure 4 As shown, the marked coordinates are the coordinates of the image scene center, the arrows indicate the radial flow direction, and 0.36 m / s represents the magnitude of the radial current velocity along the radar line of sight obtained through inversion. Meanwhile, the magnitude of the radial current velocity along the radar line of sight obtained using numerical model data is 0.3~0.45 m / s. It can be seen that the results obtained from the two models are basically consistent.

[0076] The technical solution provided in this application overcomes the limitations of single-peak Doppler spectra, enhances the application potential of electromagnetic vortex wave radar in sea surface current field detection, and provides technical support for the application of vortex wave radar in the field of marine dynamic environment detection. Furthermore, this application's embodiments, by combining the morphological characteristics of the antenna pattern in the azimuth direction of the electromagnetic vortex wave radar antenna, determine the positions of characteristic points in the Doppler spectrum, ensuring the rationality of the Doppler frequency offset estimation.

[0077] All of the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments of this application, and will not be described in detail here.

[0078] The following are embodiments of the apparatus described in this application, which can be used to execute the embodiments of the method described in this application. For details not disclosed in the apparatus embodiments of this application, please refer to the embodiments of the method described in this application.

[0079] Figure 5 This is a schematic diagram of a sea surface current field inversion device based on electromagnetic vortex wave radar data provided in an embodiment of this application. Figure 5 As shown, the device includes:

[0080] The acquisition module 501 is configured to acquire electromagnetic vortex wave radar image data and electromagnetic vortex wave radar antenna pattern.

[0081] The measurement location determination module 502 is configured to determine the Doppler spectrum based on electromagnetic vortex wave radar image data, and to determine the measurement frequency location of the trough feature point in the Doppler spectrum; wherein, the trough feature point is the trough point between the first main lobe and the second main lobe in the Doppler spectrum.

[0082] The theoretical position determination module 503 is configured to acquire the position and angle of the first main lobe and the second main lobe in the electromagnetic vortex wave radar antenna pattern, as well as the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern; and determine the theoretical frequency position of the trough feature point in the Doppler spectrum based on the position and angle of the two main lobes and the angle of the trough feature point.

[0083] The abnormal offset determination module 504 is configured to determine the difference between the measured frequency position and the theoretical frequency position as the abnormal frequency offset.

[0084] The target offset determination module 505 is configured to determine the Doppler frequency offset caused by wind and wave motion, and to determine the difference between the abnormal frequency offset and the Doppler frequency offset caused by wind and wave motion as the target Doppler frequency offset.

[0085] The inversion module 506 is configured to calculate the radial velocity of the sea surface using the target Doppler frequency offset, thereby realizing the inversion of the sea surface flow field.

[0086] According to the technical solution provided in the embodiments of this application, the Doppler spectrum is determined by using electromagnetic vortex wave radar image data. The measured frequency position of the trough feature point is obtained in the Doppler spectrum, and the theoretical frequency position of the trough feature point is determined by using the position and angle of the two main lobes and the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern. Then, the difference between the measured frequency position and the theoretical frequency position is used to obtain the abnormal frequency offset. The Doppler frequency offset caused by wind and wave motion is then removed from the abnormal frequency offset to obtain the target Doppler frequency offset. Finally, the radial velocity of the sea surface is calculated using the Doppler frequency offset to realize the inversion of the sea surface current field. This effectively expands the applicability of the Doppler frequency shift-based ocean current inversion method and improves the application potential of electromagnetic vortex wave radar in sea surface current field detection.

[0087] In some implementations, electromagnetic vortex wave radar image data is determined as follows: acquiring raw electromagnetic vortex wave radar data; performing imaging processing on the raw electromagnetic vortex wave radar data to obtain complex electromagnetic vortex wave radar image data; performing Doppler zeroing processing on the complex electromagnetic vortex wave radar image data based on the flight inertial navigation data of the radar flight platform to obtain electromagnetic vortex wave radar image data; the electromagnetic vortex wave radar image data is radar image complex data that has eliminated the theoretical Doppler shift caused by the motion and attitude of the radar flight platform.

[0088] In some implementations, determining the Doppler spectrum based on electromagnetic vortex wave radar image data includes: performing a Fourier transform on the electromagnetic vortex wave radar image data in the azimuth direction to obtain the azimuth power spectrum; and averaging the azimuth power spectrum along the range direction to obtain the Doppler spectrum.

[0089] In some implementations, determining the measurement frequency location of a trough feature point in the Doppler spectrum includes: performing morphological analysis on the Doppler spectrum to identify the first main lobe and the second main lobe; determining the lowest amplitude point between the first main lobe and the second main lobe as the trough feature point; and determining the frequency value of the trough feature point as the measurement frequency location.

[0090] In some implementations, the theoretical frequency position of the trough feature point in the Doppler spectrum is determined as follows: the difference in angle between the two main lobes is determined as the angle width; the difference in the corresponding frequencies of the two main lobes in the Doppler spectrum is determined as the frequency width; the ratio of the angle of the trough feature point to the angle width is calculated; and the product of the ratio and the frequency width is determined as the theoretical frequency position of the trough feature point in the Doppler spectrum.

[0091] In some implementations, determining the Doppler frequency shift caused by wind and wave motion includes: acquiring background wind field data corresponding to electromagnetic vortex wave radar image data; and calculating the Doppler frequency shift caused by wind and wave motion using an empirical Doppler model based on the background wind field data and radar parameters.

[0092] In some implementations, the step of calculating the radial velocity of the sea surface using the target Doppler frequency shift includes: using the formula The radial velocity at the sea surface was calculated. ;in, This is the abnormal frequency offset. This represents the Doppler frequency shift caused by wind and wave motion. The radar incident wave number. The incident angle of the radar wave.

[0093] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0094] Figure 6 This is a schematic diagram of an electronic device provided in an embodiment of this application. Figure 6 As shown, the electronic device 6 of this embodiment includes a processor 601, a memory 602, and a computer program 603 stored in the memory 602 and executable on the processor 601. When the processor 601 executes the computer program 603, it implements the steps in the various method embodiments described above. Alternatively, when the processor 601 executes the computer program 603, it implements the functions of each module / unit in the various device embodiments described above.

[0095] Electronic device 6 can be a desktop computer, laptop, handheld computer, cloud server, or other electronic device. Electronic device 6 may include, but is not limited to, processor 601 and memory 602. Those skilled in the art will understand that... Figure 6 This is merely an example of electronic device 6 and does not constitute a limitation on electronic device 6. It may include more or fewer components than shown, or different components.

[0096] The processor 601 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0097] The memory 602 can be an internal storage unit of the electronic device 6, such as a hard disk or RAM of the electronic device 6. The memory 602 can also be an external storage device of the electronic device 6, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, Flash Card, etc., equipped on the electronic device 6. The memory 602 can also include both internal and external storage units of the electronic device 6. The memory 602 is used to store computer programs and other programs and data required by the electronic device.

[0098] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0099] If an integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program may include computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. A computer-readable medium may include: any entity or device capable of carrying computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0100] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for inverting sea surface current fields based on electromagnetic vortex wave radar data, characterized in that, include: Acquire electromagnetic vortex wave radar image data and electromagnetic vortex wave radar antenna pattern; The Doppler spectrum is determined based on electromagnetic vortex wave radar image data, and the measurement frequency position of the trough feature point in the Doppler spectrum is determined; wherein, the trough feature point is the trough point between the first main lobe and the second main lobe in the Doppler spectrum; Obtain the position and angle of the first and second main lobes in the electromagnetic vortex wave radar antenna pattern, as well as the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern; determine the theoretical frequency position of the trough feature point in the Doppler spectrum based on the position and angle of the two main lobes and the angle of the trough feature point. The difference between the measured frequency position and the theoretical frequency position is determined as the abnormal frequency offset; Determine the Doppler frequency shift caused by wind and wave motion, and determine the difference between the abnormal frequency shift and the Doppler frequency shift caused by wind and wave motion as the target Doppler frequency shift. The radial velocity of the sea surface is calculated using the target Doppler frequency offset, thus realizing the inversion of the sea surface flow field.

2. The sea surface current field inversion method based on electromagnetic vortex wave radar data according to claim 1, characterized in that, The electromagnetic vortex wave radar image data is determined in the following way: Acquire raw data from electromagnetic vortex wave radar; The original data of the electromagnetic vortex wave radar is processed to obtain electromagnetic vortex wave radar image complex data. The electromagnetic vortex wave radar image data is obtained by performing Doppler zeroing processing on the complex data of the electromagnetic vortex wave radar image based on the flight inertial navigation data of the radar flight platform; the electromagnetic vortex wave radar image data is the complex radar image data that has eliminated the theoretical Doppler offset caused by the motion and attitude of the radar flight platform.

3. The sea surface current field inversion method based on electromagnetic vortex wave radar data according to claim 1, characterized in that, Determining the Doppler spectrum based on electromagnetic vortex wave radar image data includes: A Fourier transform is performed on the electromagnetic vortex wave radar image data in the azimuth direction to obtain the azimuth power spectrum. The Doppler spectrum is obtained by averaging the power spectrum along the range direction in the azimuth direction.

4. The sea surface current field inversion method based on electromagnetic vortex wave radar data according to claim 3, characterized in that, Determining the measurement frequency location of trough feature points in the Doppler spectrum includes: Morphological analysis of the Doppler spectrum was performed to identify the first and second main lobes; The lowest amplitude point between the first main lobe and the second main lobe is determined as the trough feature point; The frequency value of the trough feature point is determined to be the measurement frequency location.

5. The sea surface current field inversion method based on electromagnetic vortex wave radar data according to claim 1, characterized in that, The theoretical frequency position of the trough feature point in the Doppler spectrum is determined as follows: The angle difference between the two main lobes is defined as the angular width; The frequency difference between the two main lobes in the Doppler spectrum is defined as the frequency width. Calculate the ratio of the angle of the valley feature point to the width of the angle; The product of the ratio and the frequency width is determined as the theoretical frequency position of the trough feature point in the Doppler spectrum.

6. The sea surface current field inversion method based on electromagnetic vortex wave radar data according to claim 1, characterized in that, Determine the Doppler frequency shift caused by wind and wave motion, including: Acquire background wind field data corresponding to electromagnetic vortex wave radar image data; Based on the background wind field data and radar parameters, the Doppler frequency shift caused by wind and wave motion is calculated using an empirical Doppler model that matches the electromagnetic vortex wave band.

7. The sea surface current field inversion method based on electromagnetic vortex wave radar data according to claim 1, characterized in that, The steps for calculating the radial velocity of the sea surface using the target Doppler frequency offset include: Using formula The radial velocity at the sea surface was calculated. ; in, This is the abnormal frequency offset. This represents the Doppler frequency shift caused by wind and wave motion. The radar incident wave number, The incident angle of the radar wave.

8. A sea surface current field inversion device based on electromagnetic vortex wave radar data, characterized in that, include: The acquisition module is configured to acquire electromagnetic vortex wave radar image data and electromagnetic vortex wave radar antenna pattern. The measurement location determination module is configured to determine the Doppler spectrum based on electromagnetic vortex wave radar image data, and to determine the measurement frequency location of the trough feature point in the Doppler spectrum; wherein, the trough feature point is the trough point between the first main lobe and the second main lobe in the Doppler spectrum; The theoretical position determination module is configured to acquire the position and angle of the first and second main lobes in the electromagnetic vortex wave radar antenna pattern, as well as the angle of the trough feature point in the electromagnetic vortex wave radar antenna pattern; and determine the theoretical frequency position of the trough feature point in the Doppler spectrum based on the position and angle of the two main lobes and the angle of the trough feature point. An abnormal offset determination module is configured to determine the difference between the measured frequency position and the theoretical frequency position as the abnormal frequency offset; The target offset determination module is configured to determine the Doppler frequency offset caused by wind and wave motion, and to determine the difference between the abnormal frequency offset and the Doppler frequency offset caused by wind and wave motion as the target Doppler frequency offset. The inversion module is configured to calculate the radial velocity of the sea surface using the target Doppler frequency offset, thereby realizing the inversion of the sea surface flow field.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the sea surface current field inversion method based on electromagnetic vortex wave radar data as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the sea surface current field inversion method based on electromagnetic vortex wave radar data as described in any one of claims 1 to 7.

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