Ocean current inversion method and equipment based on shipborne ground wave radar and electromagnetic vector sensor

Abstract

The present invention relates to shipborne ground wave radar ocean current inversion technology, and more specifically to a shipborne ground wave radar ocean current inversion method and equipment based on an electromagnetic vector sensor. The method comprises the following steps: acquiring shipborne radar echo data and real-time ship motion data, including latitude and longitude information, speed information, and attitude angles (yaw, pitch, and roll); pre-estimating azimuth using the MUSIC method; compensating for speed-induced phase offset using ship speed data; compensating for echo Doppler modulation effects using oscillating motion data; and re-estimating azimuth using the MUSIC method after echo motion compensation. This method analyzes the modulation effect of platform motion on radar echoes and uses real-time motion data collected by a posture sensor to compensate for the echoes. This method can effectively reduce the impact of platform motion on azimuth estimation of ocean wave signals and improve the accuracy of ocean current estimation.

Description

Technical Field

[0001] The present invention belongs to the technical field of shipborne ground wave radar ocean current inversion, and in particular relates to a shipborne ground wave radar ocean current inversion method and equipment based on an electromagnetic vector sensor. Background Art

[0002] Ocean currents are a crucial parameter in a wide range of fields, including physical oceanography, marine environmental protection, and marine resource development. Current detection not only has practical applications in marine navigation and fishery management, but also plays a vital role in safeguarding the marine environment. High-frequency ground-wave radar (HFSGWR) utilizes the Bragg scattering of high-frequency electromagnetic waves by the ocean surface, using the Doppler effect to monitor ocean currents. Its advantages include long detection range, large coverage, and all-weather operation, leading to its increasingly widespread application in the marine sector. However, due to the limited detection range of a single radar, shore-based HFSGWR is only suitable for monitoring waters within 100-200 km of the coast. Shipborne HFSGWR represents a further development of shore-based HFSGWR technology. It inherits the advantages of shore-based radar while offering greater flexibility and maneuverability, making it suitable for detecting ocean surface information far from the coastline. Portable HFSGWR uses electromagnetic vector sensors as receiving antennas. Each receiving antenna consists of a monopole and two orthogonally arranged loop antennas. Compared to uniform linear arrays, it is smaller, occupies less space, and is easier to install, making it adaptable to various ship platforms.

[0003] Due to the complex ocean environment, shipborne platforms experience various motion forms, including non-uniform motion, rotation, and rolling. A right-handed Cartesian coordinate system is established with the platform's rotation center as the origin and the navigation direction as the X-axis. A typical ship motion model can be decomposed into six degrees of freedom: three translational degrees of freedom (translational motion of the ship along the coordinate axes) and three rotational degrees of freedom (rotational motion of the ship about the coordinate axes). These motions cause the radar transmitting and receiving antennas mounted on the platform to move, altering the coupling relationship between the radar antenna radio waves and the sea surface. Radar ocean echoes typically require a certain amount of coherent integration to extract Doppler information. During this period, ship motion introduces additional Doppler modulation effects on the echoes, shifting the Bragg peak amplitude and broadening the spectral peaks. This reduces the accuracy of the signal's direction estimation and increases the error in current estimation. Therefore, mitigating the modulation effects caused by platform maneuverability is crucial for improving the accuracy of ocean current inversion using shipborne ground wave radar. Summary of the Invention

[0004] The present invention provides a method and device for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor, which is used to solve the problem in the prior art that the modulation effect caused by the platform's maneuverability affects the accuracy of ocean current inversion using a shipborne ground wave radar, thereby reducing the influence of the platform's motion on the estimation of the azimuth angle of the ocean wave signal and improving the accuracy of ocean current estimation.

[0005] The present invention provides a method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor. The method uses a posture sensor to collect shipborne platform motion data to compensate for radar echoes. The posture sensor can obtain the platform's latitude and longitude information, speed information, and attitude angle (yaw angle, pitch angle, roll angle) information. The four oscillatory motions of drift, roll, pitch and yaw motion cause the array manifold to change within the coherent accumulation time. In the time domain, the oscillatory motion is equivalent to a modulator of the radar echo, and in the Doppler domain, it manifests as the convolution of the modulation function on the echo signal. The present invention uses the Wiener filtering method to demodulate the time domain echo signal to suppress the frequency modulation effect caused by the oscillatory motion. In addition, the forward motion of the platform causes the Doppler of the ocean echo to change, and the velocity information is used to compensate for the echo Doppler to reduce the impact of the platform motion on the azimuth estimation of the wave signal and improve the accuracy of the ocean current estimation. The following specific steps are included:

[0006] Step 1: Obtain shipborne radar echo data and shipborne platform motion data, pre-process the motion data, synchronize the radar echo data with the motion data, and obtain the motion data within the coherent accumulation time;

[0007] Step 2: Perform Fourier transform on the shipborne radar echo data to obtain the Doppler spectrum corresponding to each range element, and use the difference spectrum method to select the effective frequency point of the first-order peak area;

[0008] Step 3: Use the multiple signal classification method MUSIC to classify each effective frequency point f di Make an initial direction of arrival estimate and get the estimated azimuth value

[0009] Step 4: Determine the azimuth angle estimation error range θ based on the signal-to-noise ratio threshold m ; Estimated value in azimuth For the center angle, select is the motion compensation angle search range, θ c is the compensation angle;

[0010] Step 5: Use the shipborne platform motion data and the compensation angle to construct a set of platform velocity compensation factors to perform velocity compensation on the radar echo data;

[0011] Step 6: Determine the modulation function of the oscillation motion on the shipborne radar echo using the shipborne platform motion data and the compensation angle;

[0012] Step 7: Recover the motion-modulated echo signal and design the demodulator of each channel echo using the modulation function with the minimum mean square error as the criterion;

[0013] Step 8: Demodulate the velocity-compensated echo data and obtain the demodulated echo expression;

[0014] Step 9: Use the MUSIC method to perform a second azimuth estimation on the echo data after velocity and oscillation motion compensation, construct a two-dimensional spatial spectrum, and use the azimuth corresponding to the peak of the two-dimensional spatial spectrum as the azimuth estimation value of the wave signal;

[0015] Step 10: Calculate the echo Doppler f di Radial flow velocity corresponding to the frequency point;

[0016] Step 11: Divide the detected sea area into grids according to the radar range resolution and angular resolution, and integrate the radial flow results obtained from a data inversion. If there are multiple currents in a grid, take the middle value as the radial flow result in the grid; for grids without currents, interpolate the original radial flow field to finally obtain the radial flow field.

[0017] According to the shipborne ground wave radar ocean current inversion method based on electromagnetic vector sensor provided by the present invention, firstly, the echo data matrix X(t) = [x1(t)x2(t)x3(t)] of the shipborne radar is obtained. T , where x1(t), x2(t) and x3(t) are the echo data of the three array element channels of the electromagnetic vector sensor, and T represents the transpose of the matrix. At the same time, the motion data of the shipborne platform is obtained, including the ship speed v p (t), drift motion displacement w(t), roll angle α(t), pitch angle β(t) and yaw angle Secondly, the motion data is preprocessed, the radar echo data and the motion data are time synchronized, and the motion data within the coherent accumulation time is obtained.

[0018] According to the ocean current inversion method of shipborne ground wave radar based on electromagnetic vector sensor provided by the present invention, the echo signals of the three channels of the shipborne radar are subjected to a Fourier transform process to obtain the Doppler spectrum X(f) = [x1(f)x2(f)x3(f)] corresponding to each range element. T The effective frequency point of the first-order peak region is selected by using the difference spectrum method. First, the echo Doppler spectrum is smoothed at m points, and then the adjacent spectrum points of the smoothed Doppler spectrum are subtracted to obtain the difference spectrum, and the Bragg frequency f is selected. B The maximum extreme point on the left is taken as the left boundary of the first-order peak, and the minimum extreme point on the right is taken as the right boundary. A signal-to-noise ratio threshold is set, and finally the spectrum point that meets the signal-to-noise ratio threshold is selected in the first-order peak area as the effective frequency point {f d1 ,f d2 ,...,f di ,...f dK}, K represents the number of effective frequency points.

[0019] According to the shipborne ground wave radar current inversion method based on electromagnetic vector sensor provided by the present invention, the multiple signal classification method (Multiple Signal Classification, MUSIC) is used to classify each effective frequency point f di Make an initial direction of arrival estimate and get the estimated azimuth value

[0020] According to the shipborne ground wave radar current inversion method based on electromagnetic vector sensor provided by the present invention, the azimuth estimation error range θ is determined according to the signal-to-noise ratio threshold. m .by For the center angle, select Angle search range for motion compensation.

[0021] According to the shipborne ground wave radar ocean current inversion method based on electromagnetic vector sensor provided by the present invention, the velocity data v p (t) and compensation angle θ c Construct a set of platform velocity compensation factors:

[0022]

[0023] in v p (t) represents the ship speed in the tth frequency sweep cycle, is the average ship speed during the coherent integration time, is the yaw angle of the t-th sweep cycle, and λ represents the radar wavelength. Velocity compensation is performed on the echo data X(t), and the echo data after velocity compensation is expressed as:

[0024] y cn (t) = g c (t)·x n (t)

[0025] where x n (t) represents the echo data of the nth channel, and n=1, 2, 3 represents three channels.

[0026] According to the shipborne ground wave radar current inversion method based on electromagnetic vector sensor provided by the present invention, the drift motion displacement w(t), roll angle α(t), pitch angle β(t) and yaw angle are used to calculate the current inversion method. and compensation angle θ c Determine the modulation functions of the oscillatory motion on the echoes of the three channels, which are:

[0027]

[0028]

[0029]

[0030] where λ is the radar wavelength.

[0031] According to the ocean current inversion method of shipborne ground wave radar based on electromagnetic vector sensor provided by the present invention, in order to restore the echo signal modulated by motion, the demodulator h of each channel echo is designed by using the modulation function with the minimum mean square error as the criterion. cn (t), calculated by the following formula

[0032]

[0033] Where * represents a conjugate complex number, n=1, 2, 3 represents three channels, and γ represents the echo signal-to-noise ratio.

[0034] According to the shipborne ground wave radar ocean current inversion method based on electromagnetic vector sensor provided by the present invention, the velocity compensated echo data y cn (t) is demodulated to suppress the influence of oscillation motion. The demodulated echo can be expressed as

[0035] z cn (t) = h cn (t)·y cn (t).

[0036] According to the shipborne ground wave radar current inversion method based on electromagnetic vector sensor provided by the present invention, the echo data z after velocity and oscillation motion compensation is processed by MUSIC method. cn (t) Perform a second azimuth estimation and construct a two-dimensional spatial spectrum:

[0037]

[0038] where a(θ i )=[1cos(θ i +45°)sin(θ i +45°)] T is the antenna steering vector, θ i Indicates the azimuth search angle, U N (θ c ) is the noise subspace obtained by eigendecomposition of the compensated echo covariance matrix, and H represents the conjugate transpose of the matrix. The azimuth θ corresponding to the peak of the two-dimensional spatial spectrum is i As an estimate of the direction of the sea wave signal.

[0039] According to the shipborne ground wave radar ocean current inversion method based on electromagnetic vector sensor provided by the present invention, the average ship speed is used to Echo Doppler f di and the estimated value θ i The radial flow velocity corresponding to this frequency point is calculated by the following formula:

[0040]

[0041] where f B is the Bragg frequency.

[0042] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor as described above is implemented.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This solution uses an electromagnetic vector sensor as the receiving antenna for the shipborne radar system and utilizes a posture sensor to obtain real-time motion data to compensate for the Doppler modulation effect of the echo caused by the platform's maneuverability. Considering the wide-beam characteristics of the electromagnetic vector sensor and the fact that the modulation effect of the platform's motion on the echo is related to the azimuth of the incoming wave, this solution performs a Fourier transform on the radar echo and performs motion compensation after separating the Doppler dimension. First, the initial azimuth of the wave signal is estimated. Next, the phase offset caused by the platform's velocity and the modulation function of the four oscillatory motions of drift, roll, pitch, and yaw on the echo are determined. Velocity compensation and oscillatory motion compensation are performed on the echo, respectively. This can effectively reduce the azimuth and radial flow estimation errors and improve the current inversion performance.

[0045] The present invention analyzes the modulation effect of platform motion on radar echoes and uses posture sensors to collect real-time motion data to compensate for the echoes, which can effectively reduce the impact of platform motion on the azimuth estimation of wave signals and improve the accuracy of ocean current estimation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 This is a flow chart of a single process of a method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor provided by an embodiment of the present invention;

[0048] Figure 2 is the measured ship speed data provided by the embodiment of the present invention;

[0049] FIG3( a ) is the drift displacement information provided by an embodiment of the present invention;

[0050] FIG3( b ) is the roll motion information provided by an embodiment of the present invention;

[0051] FIG3( c ) is pitch motion information provided by an embodiment of the present invention;

[0052] FIG3( d ) is yaw motion information provided by an embodiment of the present invention;

[0053] Figure 4 It is a structural diagram of an electronic device provided by an embodiment of the present invention.

[0054] Reference numerals:

[0055] Among them: 410 - processor, 420 - communication interface, 430 - memory, 440 - communication bus. DETAILED DESCRIPTION

[0056] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0057] The present embodiment uses a shipborne ground wave radar current inversion method based on an electromagnetic vector sensor, and mainly includes the following five steps: obtaining shipborne radar echo data and real-time ship motion data, including latitude and longitude information, speed information, and attitude angles (yaw angle, pitch angle, and roll angle); pre-estimating the azimuth angle based on the MUSIC method; compensating for the phase offset caused by speed using the ship speed data; compensating for the echo Doppler modulation effect using the oscillating motion data; and re-estimating the azimuth angle using the MUSIC method after echo motion compensation.

[0058] When implementing it specifically, Figure 1 As shown in FIG, the method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor includes the following steps:

[0059] Step 1: First, obtain the echo data matrix X(t) = [x1(t)x2(t)x3(t)] of the three channels of the shipborne radar T , and the shipboard platform motion data, including the ship speed v p (t), drift motion displacement w(t), roll angle α(t), pitch angle β(t) and yaw angle Secondly, the motion data is preprocessed, and the radar echo data and the motion data are synchronized with the accuracy of 1s to obtain the motion data within the coherent accumulation time. The motion data after preprocessing is as follows Figure 2 As shown in FIG3(a), FIG3(b), FIG3(c), and FIG3(d), the present invention selects the coherent accumulation frame number N=1024, the radar sweep period T c= 0.27s, and assuming that the platform motion parameters remain unchanged during the sweep period, so t = 1, 2, ..., N, where N is the number of accumulated frames;

[0060] Step 2: Perform a Fourier transform on the echo signals of the three channels of the shipborne radar to obtain the Doppler spectrum corresponding to each range element X(f) = [x1(f)x2(f)x3(f)] T , the effective frequency point of the first-order peak area is selected by using the difference spectrum method. First, the echo Doppler spectrum is smoothed by 512 points, and then the adjacent spectrum points of the smoothed Doppler spectrum are subtracted to obtain the difference spectrum, and the Bragg frequency f is selected. B The maximum extreme point on the left is taken as the left boundary of the first-order peak, and the minimum extreme point on the right is taken as the boundary. The signal-to-noise ratio threshold is set to 10dB. Finally, the spectrum point that meets the signal-to-noise ratio threshold is selected in the first-order peak area as the effective frequency point {f d1 ,f d2 ,...,f di ,...f dK}, K represents the number of effective frequency points;

[0061] Step 3: Use Multiple Signal Classification (MUSIC) to classify each valid frequency point f di Make an initial direction of arrival estimate and get the estimated azimuth value

[0062] Step 4: Determine the azimuth angle estimation error range θ by the signal-to-noise ratio threshold m According to the angle estimation variance formula of the MUSIC method when the electromagnetic vector sensor is used as the receiving antenna:

[0063]

[0064] Where N is the number of snapshots, SNR is the signal-to-noise ratio, and it can be seen that when the signal-to-noise ratio threshold is 10dB, the angle estimation error is less than 10°. For the center angle, select Angle search range for motion compensation;

[0065] Step 5: Using velocity data v p (t) and compensation angle θ c Construct a set of platform velocity compensation factors:

[0066]

[0067] in v p (t) represents the ship speed in the tth frequency sweep cycle, is the average ship speed during the coherent integration time, is the yaw angle of the t-th sweep cycle, and λ represents the radar wavelength. Velocity compensation is performed on the echo data X(t), and the echo data after velocity compensation is expressed as:

[0068] y cn (t) = g c (t)·x n (t)

[0069] where x n (t) represents the echo data of the nth channel, where n=1, 2, 3 represent three receiving channels;

[0070] Step 6: Use the drift motion displacement w(t), roll angle α(t), pitch angle β(t) and yaw angle and compensation angle θ c Determine the modulation functions of the oscillatory motion on the echoes of the three channels, which are:

[0071]

[0072]

[0073]

[0074] Where λ represents the radar wavelength;

[0075] Step 7: Using the modulation function p c1 (t), p c2 (t) and p c3 (t) Design the demodulator h for each channel echo cn (t), calculated by the following formula:

[0076]

[0077] Where * represents conjugate complex number, n=1, 2, 3 represents three channels, and γ represents echo signal-to-noise ratio;

[0078] Step 8: Echo data y after velocity compensation cn (t) is demodulated to suppress the influence of oscillation motion. The demodulated echo z cn (t) can be expressed as

[0079] z cn (t) = h cn (t)·y cn (t)

[0080] Step 9: Use the MUSIC method to compensate the echo data z after velocity and oscillation motion cn (t) Make a second azimuth angle estimate and construct a two-dimensional spatial spectrum

[0081]

[0082] where a(θ i )=[1cos(θ i +45°)sin(θ i +45°)] T is the antenna steering vector, θ i Indicates the azimuth search angle, U N (θ c ) is the noise subspace obtained by eigendecomposition of the compensated echo covariance matrix, and H represents the conjugate transpose of the matrix. The azimuth θ corresponding to the peak of the two-dimensional spatial spectrum is i As an estimate of the bearing of the sea wave signal;

[0083] Step 10: Using Average Boat Speed Echo Doppler f di and the estimated value θ i The radial flow velocity corresponding to this frequency point is calculated by the following formula:

[0084]

[0085] where f B is the Bragg frequency, the average ship speed

[0086] Step 11: Grid the detected sea area based on the radar's range and angular resolutions. In this embodiment, the radar range cell width is ΔR = 2.5 km, and the angular cell width is Δθ = 3°. The radial flow results obtained from the inversion of a field of data are integrated. For grids with multiple currents, the median value is taken as the final radial flow result for that grid. For grids without currents, the original radial flow field is interpolated to obtain the final radial flow field.

[0087] Figure 4 An example of a physical structure diagram of an electronic device is shown below. Figure 4 As shown, the electronic device may include: a processor 410, a communication interface 420, a memory 430, and a communication bus 440, wherein the processor 410, the communication interface 420, and the memory 430 communicate with each other via the communication bus 440. The processor 410 may call logic instructions in the memory 430 to execute the shipborne ground wave radar ocean current inversion method based on the electromagnetic vector sensor.

[0088] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0089] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiments.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. The method for inverting ocean currents using shipborne ground wave radar based on electromagnetic vector sensors is characterized by: The following steps are involved: Acquire shipborne radar echo data and shipborne platform motion data, preprocess the motion data, synchronize the radar echo data with the motion data, and obtain the motion data within the coherent accumulation time; the shipborne radar echo data is represented by a matrix: X(t) = [x1(t)x2(t)x3(t)] T , where x1(t), x2(t) and x3(t) are the echo data of the three array element channels of the electromagnetic vector sensor, and T represents the transpose of the matrix; the shipborne platform motion data, including the ship speed v p (t), drift motion displacement w(t), roll angle α(t), pitch angle β(t) and yaw angle The shipborne radar echo data is Fourier transformed to obtain the Doppler spectrum corresponding to each range element, and the effective frequency point of the first-order peak area is selected using the difference spectrum method; The multiple signal classification method MUSIC is used to classify each effective frequency point f di Make an initial direction of arrival estimate and get the azimuth angle estimate Determine the azimuth angle estimation error range θ based on the signal-to-noise ratio threshold m ; Estimated value in azimuth For the center angle, select is the motion compensation angle search range, θ c is the compensation angle; A set of platform velocity compensation factors is constructed using the shipborne platform motion data and compensation angles. Velocity compensation of radar echo data includes: Using ship speed v p (t) and compensation angle θ c Construct a set of platform velocity compensation factors: in v p (t) represents the ship speed in the tth frequency sweep cycle, is the average ship speed during the coherent integration time, is the yaw angle of the t-th sweep cycle, and λ represents the radar wavelength. Velocity compensation is performed on the echo data X(t), and the echo data after velocity compensation is expressed as: y cn (t)=g c (t)·x n (t) where x n (t) represents the echo data of the nth channel, where n=1, 2, 3 represents three channels; The modulation function of the oscillation motion on the shipborne radar echo is determined using the shipborne platform motion data and compensation angle; Recover the motion-modulated echo signal and design the demodulator of each channel echo using the modulation function with the minimum mean square error as the criterion; Demodulate the velocity-compensated echo data and obtain the demodulated echo expression; The MUSIC method is used to perform a second azimuth estimation on the echo data after velocity and oscillation motion compensation, and a two-dimensional spatial spectrum is constructed. The azimuth corresponding to the peak of the two-dimensional spatial spectrum is used as the azimuth estimation value of the wave signal. Calculate the echo Doppler f di Radial flow velocity corresponding to the frequency point; The detected sea area is divided into grids according to the radar range resolution and angular resolution, and the radial flow results obtained from a data inversion are integrated. When there are multiple currents in a grid, the middle value is taken as the radial flow result in the grid; for grids without currents, the original radial flow field is interpolated to obtain the radial flow field.

2. The method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor according to claim 1, characterized in that: The shipborne radar echo data is Fourier transformed to obtain the Doppler spectrum corresponding to each range element. The effective frequency points of the first-order peak area are selected using the difference spectrum method, including: 1) Perform a Fourier transform on the echo data of the three array element channels of the shipborne radar to obtain the Doppler spectrum corresponding to each range element: X(f)=[x1(f)x2(f)x3(f)] T ; 2) Use the difference spectrum method to select the effective frequency points in the first-order peak area; Perform m-point smoothing on the echo Doppler spectrum, then make a difference between the adjacent points of the smoothed Doppler spectrum to obtain the difference spectrum, and select the Bragg frequency f B The maximum extreme point on the left is taken as the left boundary of the first-order peak, and the minimum extreme point on the right is taken as the right boundary. A signal-to-noise ratio threshold is set, and the spectrum points that meet the signal-to-noise ratio threshold are selected in the first-order peak area as the effective frequency points {f d1 ,f d2 ,...,f di ,...f dK }, K represents the number of effective frequency points.

3. The method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor according to claim 1, characterized in that: The modulation function of the oscillatory motion on the shipborne radar echo includes: Using the drift motion displacement w(t), roll angle α(t), pitch angle β(t) and yaw angle and compensation angle θ c The modulation functions of the oscillatory motion on the echoes of the three channels are determined as follows: where λ is the radar wavelength.

4. The method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor according to claim 3, characterized in that: The demodulator of each channel echo is: Wherein, * represents a conjugate complex number, n=1, 2, 3 represents three channels, and γ represents the echo signal-to-noise ratio.

5. The method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor according to claim 3, characterized in that: The expression of the demodulated echo is: z cn (t)=h cn (t)·y cn (t) Among them, z cn (t) is the demodulated echo data, y cn (t) is the echo data after velocity compensation, h cn (t) is the demodulator of each channel echo.

6. The method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor according to claim 5, characterized in that: The second azimuth angle estimation of the echo data after velocity and oscillation motion compensation using the MUSIC method includes: constructing a two-dimensional spatial spectrum: where a(θ i )=[1cos(θ i +45°)sin(θ i +45°)] T is the antenna steering vector, θ i Indicates the azimuth search angle, U N (θ c ) is the noise subspace obtained by eigendecomposition of the compensated echo covariance matrix, H represents the conjugate transpose of the matrix; the azimuth θ corresponding to the peak of the two-dimensional spatial spectrum is i As an estimate of the direction of the sea wave signal.

7. The method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor according to claim 6, characterized in that: Calculate the echo Doppler f di The radial flow velocities corresponding to the frequency points include: Using average ship speed Echo Doppler f di and the estimated value θ i The radial flow velocity corresponding to this frequency point is calculated by the following formula: where f B is the Bragg frequency.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method for inverting ocean currents using a shipborne ground wave radar based on an electromagnetic vector sensor as claimed in any one of claims 1 to 7 is implemented.

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