Ocean wave inversion method and system based on time Doppler spectrum of S-band wave measuring radar

Abstract

The present invention provides a wave inversion method and system based on the time Doppler spectrum of an S-band wave measuring radar. The method comprises the following steps: comparing and estimating the left and right bandwidth boundary frequencies of an ocean echo signal in a single Doppler spectrum to obtain the bandwidth frequency of the single Doppler spectrum; calculating the average bandwidth frequency of the entire time Doppler spectrum; adding a constraint factor to obtain a corrected average bandwidth frequency; re-determining the bandwidth boundary frequencies based on the corrected average bandwidth frequency; obtaining a single Doppler spectrum frequency shift based on a spectral moment method to obtain a velocity time series, thereby eliminating the influence of other velocity components; obtaining a wave spectrum at a radar illumination direction angle based on the velocity time series of a fixed distance element; and fusing the complete undirected wave spectrum to obtain a wave inversion result. The method effectively eliminates the influence of wave breaking by performing correlation processing only on time domain data, thereby improving the accuracy of microwave radar wave inversion.

Description

Technical Field

[0001] The invention belongs to the field of microwave radar signal processing, and in particular relates to a scheme for inverting ocean waves using microwave radar. Background Art

[0002] In ocean monitoring, wave parameters, such as significant wave height and mean wave period, are crucial for marine engineering, hazard prediction, and oceanographic research. Thanks to its high temporal and spatial resolution, coherent microwave radar has garnered significant attention for detecting and retrieving ocean waves. The transmitted signals of coherent microwave radars have a defined phase angle, enabling them to obtain Doppler information of the ocean surface and, consequently, Doppler radial velocity. Using the conversion relationship between radial velocity and wave height spectra, wave parameters such as significant wave height and mean wave period can be derived.

[0003] At the same time, higher spatial and temporal resolution also enables coherent microwave radar to detect detailed information on the ocean surface, such as wave breaking. Breaking waves exhibit some nonlinear characteristics in the wavenumber frequency spectrum observed by radar, such as "group lines," which cause low-frequency components to appear in the radar-observed ocean wave spectrum, leading to inaccurate estimates of ocean wave parameters. To eliminate the impact of wave breaking, many researchers use high-pass filters to remove noise and nonlinear features before inverting ocean wave parameters. Some researchers have designed various filters based on linear wave theory and the analysis of the influence of various frequency components in the wavenumber frequency spectrum. Some researchers have also decomposed and reconstructed the space-time velocity series observed by radar. In this process, feature analysis methods are used to remove non-wave components and the reconstructed velocity is used to perform wave inversion.

[0004] In the prior art, the closest patent documents are as follows:

[0005] A method and device for suppressing breaking wave interference in an S-band Doppler radar (CN105487056A) uses empirical mode decomposition to decompose radar echo signals affected by breaking waves into multiple intrinsic mode functions (IMFs). Based on the characteristic that breaking wave signals have a higher frequency than general ocean echo signals, the higher-frequency components of all IMFs are removed, and the remaining IMFs are reconstructed to obtain a signal processed by breaking waves.

[0006] A method for inverting ocean wave parameters using X-band navigation radar based on a novel wave dispersion relation bandpass filter (CN103969643B) includes five parts: radar image acquisition, radar image preprocessing, sea clutter image spectrum acquisition, wave information extraction, and sea surface information inversion. The sea clutter image spectrum is obtained through Fourier transform, and a novel bandpass filter is used to extract wave energy from the sea clutter image spectrum.

[0007] The above methods all focus on processing in the space-time domain and require a large amount of space-time data. However, when spatial or temporal observations are missing (e.g., due to occlusion or large changes in seabed topography), these methods will fail. Summary of the Invention

[0008] In order to address the shortcomings of the above-mentioned space-time domain processing methods, the present invention starts from the mechanism of "group line" generation and analyzes the impact of wave breaking on the Doppler spectrum. A wave inversion method that uses the time Doppler spectrum to eliminate the impact of breaking is proposed. This method only uses time domain data.

[0009] The technical solution of the present invention is a wave inversion method based on the time Doppler spectrum of the S-band wave measuring radar, comprising the following steps:

[0010] Step 1: At each radar illumination azimuth, at a fixed range element and at a fixed time point, a single echo Doppler spectrum is obtained. A corresponding threshold is set for the single Doppler spectrum, and the left and right bandwidth boundary frequencies of the ocean echo signal in the single Doppler spectrum are estimated by comparing the thresholds, thereby obtaining the bandwidth frequency of the single Doppler spectrum.

[0011] Step 2: At each radar illumination azimuth, a fixed range element is used to obtain a time Doppler spectrum, and the average bandwidth frequency of the entire time Doppler spectrum is calculated based on the bandwidth frequency of a single Doppler spectrum in the time Doppler spectrum;

[0012] Step 3: Wave breaking will broaden the Doppler spectrum. A constraint factor is added to the average bandwidth frequency of the time Doppler spectrum of the fixed range element to obtain the corrected average bandwidth frequency.

[0013] Step 4: Determine the broadening of a single Doppler spectrum. If it broadens to the right, redefine the right bandwidth boundary frequency based on the left bandwidth boundary frequency and the corrected average bandwidth frequency. If it broadens to the left, redefine the left bandwidth boundary frequency based on the right bandwidth boundary frequency and the corrected average bandwidth frequency. The redetermined bandwidth boundary frequency does not include the broadening portion caused by wave breaking.

[0014] Step 5: Within the re-determined bandwidth boundary frequency, the frequency shift of a single Doppler spectrum is obtained using the spectral moment method, and then the velocity at the fixed range element and fixed time point at the radar illumination azimuth is obtained. For the time Doppler spectrum of the fixed range element, a velocity time series is obtained, and the influence of other velocity components is eliminated, and detrending processing is performed;

[0015] Step 6: Based on the linear wave theory of coherent microwave radar, the wave spectrum at the radar illumination direction angle is obtained according to the velocity time series of the fixed range element;

[0016] Step 7: The wave spectra at each radar illumination angle are fused to obtain a complete undirected wave spectrum, and the wave parameters are obtained through the undirected wave spectrum to obtain the wave inversion result.

[0017] Furthermore, in step 1, let It represents the nth radar illumination azimuth. The Doppler spectrum of a single echo at a fixed distance element and a fixed time point on the radar illumination azimuth is defined as Where r0 represents the radial distance between the fixed range element and the radar, t i represents a fixed time point, and f represents the Doppler frequency caused by the motion of the waves relative to the radar;

[0018] The threshold of a single Doppler spectrum is defined as κ, and the calculation formula is,

[0019]

[0020] Among them A noise Represents the average amplitude of the noise floor in a single Doppler spectrum, and max() represents the maximum value;

[0021] The left bandwidth boundary frequency of the ocean echo signal in a single Doppler spectrum is defined as The determination method is to first determine the maximum amplitude of a single Doppler spectrum, start from the maximum amplitude and traverse to the left, if the amplitude of a continuous segment is less than or equal to (κ+A noise ), the Doppler frequency corresponding to the leftmost amplitude of the segment is determined as the left bandwidth boundary frequency of the single Doppler spectrum;

[0022] The right bandwidth boundary frequency of the ocean echo signal in a single Doppler spectrum is defined as The determination method is to first determine the maximum amplitude of a single Doppler spectrum, start from the maximum amplitude and traverse to the right, if the amplitude of a continuous segment is less than or equal to (κ+A noise ), the Doppler frequency corresponding to the rightmost amplitude of the segment is determined as the right bandwidth boundary frequency of the single Doppler spectrum;

[0023] Bandwidth frequency of a single Doppler spectrum The calculation method is

[0024]

[0025] Moreover, in step 2, the average bandwidth frequency of the entire time Doppler spectrum is expressed as ABW, which is calculated as follows:

[0026]

[0027] Where P is the number of time series points.

[0028] Moreover, in step 3, the constraint factor used to correct the average bandwidth frequency of the time Doppler spectrum is defined as β, and 0<β≤1;

[0029] The corrected average bandwidth frequency of the time Doppler spectrum is defined as MABW, which is calculated as follows:

[0030] MABW=βABW.

[0031] Furthermore, in step 4, the left bandwidth boundary frequency of the re-determined single Doppler spectrum is defined as For a single Doppler spectrum, the left bandwidth boundary frequency is redefined The calculation method is as follows,

[0032]

[0033] In step 4, the right bandwidth boundary frequency of the re-determined single Doppler spectrum is defined as For a single Doppler spectrum, the right bandwidth boundary frequency is redefined The calculation method is as follows,

[0034]

[0035] Furthermore, in step 5, the frequency shift of a single Doppler spectrum is defined as Obtained by spectral moment method within the redefined bandwidth boundary frequency The calculation method is,

[0036]

[0037] Velocity at a fixed distance element and a fixed time point on the radar azimuth It is derived from the Doppler effect, that is,

[0038]

[0039] Where λ0 represents the wavelength of electromagnetic wave;

[0040] For a fixed range element, the time Doppler spectrum The corresponding speed time series is defined as The detrending term of the speed time series is processed as follows:

[0041]

[0042] Among them, mean() is the average value, is the processed velocity time series.

[0043] Furthermore, in step 6, the wave spectrum of a fixed range element on the radar illumination azimuth is defined as Among them, fwave represents the wave frequency, which is related to the time series t. According to the linear wave theory of coherent microwave radar, the conversion relationship between the velocity time series of a fixed distance element on the radar illumination azimuth and the wave spectrum of a fixed distance element is:

[0044]

[0045] Among them, FFT represents fast Fourier transform, and the transfer function TF is expressed as follows,

[0046]

[0047] In the above formula, k represents the wave number, d represents the water depth at a fixed distance, ω represents the wave angular frequency, and Δf wave represents the wave frequency resolution, and θ represents the antenna incidence angle.

[0048] Moreover, in step 7, the complete undirected wave spectrum of a fixed distance element is defined as S(r0,f wave ), calculated as follows,

[0049]

[0050] The two wave parameters of significant wave height and mean wave period mentioned in step 7 are defined as H s 、T av , through the complete undirected wave spectrum S(r0,f wave ) is obtained, and the calculation is as follows,

[0051]

[0052]

[0053]

[0054] On the other hand, the present invention also provides an ocean wave inversion system based on the time Doppler spectrum of an S-band wave measuring radar, which is used to implement the above-mentioned ocean wave inversion method based on the time Doppler spectrum of an S-band wave measuring radar.

[0055] Furthermore, the invention comprises a processor and a memory, wherein the memory is used to store program instructions, and the processor is used to call the stored instructions in the memory to execute the above-mentioned ocean wave inversion method based on the time Doppler spectrum of the S-band wave measuring radar.

[0056] The improvements and effects of the present invention relative to the prior art are as follows:

[0057] The wave inversion method based on the time Doppler spectrum of the S-band wave measuring radar described in the present invention starts from the time Doppler spectrum observed by the radar. Compared with the space-time domain processing method, its advantage is that it only uses time domain data, the data volume is small, and it solves the problem of missing space domain or time domain data due to obstruction, large changes in seabed topography, etc. The method is flexible in application and can adapt to complex and changeable marine environments, and has great research and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is an overall flow chart of the method according to an embodiment of the present invention.

[0059] Figure 2 FIG1 is a schematic diagram of a time Doppler spectrum of a fixed range element at a radar illumination azimuth according to an embodiment of the present invention, wherein the white dotted lines represent the left and right bandwidth boundary frequencies of the ocean echo determined according to step 1, and the white solid lines represent the corrected left and right bandwidth boundary frequencies determined according to step 4.

[0060] Figure 3 This is a velocity time series comparison diagram of a fixed distance element at a certain radar illumination azimuth according to an embodiment of the present invention.

[0061] Figure 4 Schematic diagram of the comparison of ocean wave spectra for fixed distance elements on a certain radar illumination azimuth according to an embodiment of the present invention, where Tav_W, Tav_P, and Tav_Buoy represent the average wave periods of the unprocessed, the time-domain processed, and the buoy observation, respectively. DETAILED DESCRIPTION

[0062] In order to more clearly illustrate the purpose, technical solutions and significant effects of the present invention, the following is a detailed description with reference to the accompanying drawings and specific implementation examples. It should be understood that the specific implementation of the present invention is not limited to the example description here.

[0063] As attached Figure 1 As shown, an embodiment of the present invention provides a method for inverting ocean waves based on the time Doppler spectrum of an S-band wave measuring radar, comprising the following specific steps:

[0064] Step 1: At each radar illumination azimuth, at a fixed range element and at a fixed time point, obtain a single echo Doppler spectrum (referred to as a single Doppler spectrum). Calculate a threshold for the single Doppler spectrum and estimate the left and right bandwidth boundary frequencies of the ocean echo signal in the single Doppler spectrum by comparing the thresholds. This results in the bandwidth frequency of the single Doppler spectrum.

[0065] Each radar illumination azimuth described in step 1 is defined as:

[0066]

[0067] in, Indicates the nth radar illumination azimuth, n is an integer, and N represents the number of radar illumination azimuths;

[0068] The Doppler spectrum of a single echo at a fixed distance element and a fixed time point on the radar illumination azimuth described in step 1 is defined as Where r0 represents the radial distance between the fixed range element and the radar, which is a constant, t i represents a fixed time point, which is a constant, and f represents the Doppler frequency generated by the motion of the waves relative to the radar;

[0069] The threshold of a single Doppler spectrum in step 1 is defined as κ, which is calculated as follows:

[0070]

[0071] Among them A noise Represents the average amplitude of the noise floor in a single Doppler spectrum, and max() represents the maximum value;

[0072] The left bandwidth boundary frequency of the ocean echo signal in the single Doppler spectrum described in step 1 is defined as The determination method is as follows: first determine the maximum amplitude of a single Doppler spectrum, start from the maximum amplitude and traverse to the left, if the amplitude of a continuous segment is less than or equal to (κ+A noise ), the Doppler frequency corresponding to the leftmost amplitude of the segment is determined as the left bandwidth boundary frequency of the single Doppler spectrum;

[0073] The right bandwidth boundary frequency of the ocean echo signal in the single Doppler spectrum described in step 1 is defined as The determination method is as follows: first determine the maximum amplitude of a single Doppler spectrum, start from the maximum amplitude and traverse to the right, if the amplitude of a continuous segment is less than or equal to (κ+A noise ), the Doppler frequency corresponding to the rightmost amplitude of the segment is determined as the right bandwidth boundary frequency of the single Doppler spectrum;

[0074] The bandwidth frequency of the single Doppler spectrum described in step 1 is calculated as follows:

[0075]

[0076] Step 2: At each radar illumination azimuth, fix the range element to obtain the time Doppler spectrum, and calculate the average bandwidth frequency of the entire time Doppler spectrum based on the bandwidth frequency of a single Doppler spectrum in the time Doppler spectrum;

[0077] The time Doppler spectrum of a fixed range element on the radar illumination azimuth described in step 2 is defined as Where r0 represents the radial distance between the fixed range element and the radar, which is a constant, t represents the time series, and f represents the Doppler frequency generated by the motion of the waves relative to the radar. It represents the nth radar illumination azimuth, which is a constant;

[0078] The average bandwidth frequency of the entire time Doppler spectrum described in step 2 is denoted as ABW, which is calculated as follows:

[0079]

[0080] Where P is the number of time series points, i is the label of the time series point, i = 1, 2,…, P.

[0081] Step 3: Wave breaking will broaden the Doppler spectrum. A constraint factor is added to the average bandwidth frequency of the time Doppler spectrum of the fixed range element to obtain the corrected average bandwidth frequency. The constraint factor should be between 0 and 1.

[0082] The constraint factor for correcting the average bandwidth frequency of the time Doppler spectrum in step 3 is defined as β, and 0<β≤1;

[0083] The average bandwidth frequency of the corrected time Doppler spectrum described in step 3 is defined as MABW, which is calculated as follows:

[0084] MABW=βABW

[0085] Step 4: Determine the broadening of a single Doppler spectrum. If it broadens to the right, redefine the right bandwidth boundary frequency based on the left bandwidth boundary frequency and the corrected average bandwidth frequency. If it broadens to the left, redefine the left bandwidth boundary frequency based on the right bandwidth boundary frequency and the corrected average bandwidth frequency. The redetermined bandwidth boundary frequency does not include the broadening part caused by wave breaking, so it can be considered that the influence of breaking has been eliminated.

[0086] The left bandwidth boundary frequency of the re-determined single Doppler spectrum described in step 4 is defined as For a single Doppler spectrum, the left bandwidth boundary frequency is redefined is calculated as follows:

[0087]

[0088] The right bandwidth boundary frequency of the re-determined single Doppler spectrum described in step 4 is defined as For a single Doppler spectrum, the right bandwidth boundary frequency is redefined is calculated as follows:

[0089]

[0090] Step 5: Within the redefined bandwidth boundary frequency, the frequency shift of a single Doppler spectrum is obtained using the spectral moment method. This allows the velocity at the radar illumination azimuth at a fixed range element and time point to be obtained. For the time Doppler spectrum of a fixed range element, a velocity time series can be obtained. To eliminate the influence of other velocity components in the velocity time series, such as the seawater velocity, detrending terms are performed on the velocity time series.

[0091] The frequency shift of a single Doppler spectrum described in step 5 is defined as Obtained by spectral moment method within the redefined bandwidth boundary frequency The calculation method is:

[0092]

[0093] Where Af is the differential of the Doppler frequency f;

[0094] The fixed distance element and the speed at the fixed time point of the radar illumination azimuth described in step 5 It can be derived from the Doppler effect, that is:

[0095]

[0096] Where λ0 represents the wavelength of electromagnetic wave;

[0097] For a fixed range element, the time Doppler spectrum The speed time series can be obtained and defined as The detrending term of the speed time series is processed as follows:

[0098]

[0099] Among them, mean() is the average value, is the processed velocity time series.

[0100] Step 6: Based on the linear wave theory of coherent microwave radar, the wave spectrum at the radar illumination angle can be obtained according to the velocity time series of fixed range elements;

[0101] The wave spectrum of a fixed distance element on the radar illumination azimuth described in step 6 is defined as Among them, f wave It represents the wave frequency and is related to the time series t. According to the linear wave theory of coherent microwave radar, the conversion relationship between the velocity time series of a fixed distance element on the radar illumination azimuth and the wave spectrum of the fixed distance element is:

[0102]

[0103] Among them, FFT represents fast Fourier transform, and the transfer function TF is expressed as follows:

[0104]

[0105] In the above formula, k represents the wave number, d represents the water depth at a fixed distance, ω represents the wave angular frequency, and Δf wave represents the wave frequency resolution, θ represents the antenna incident angle, and tanh 2 kd represents the square of tanh(kd), where tanh() is the hyperbolic tangent function.

[0106] Step 7: The wave spectra at each radar illumination angle are fused to obtain a complete undirected wave spectrum. Wave parameters such as significant wave height and average wave period can be obtained through the undirected wave spectrum to obtain the wave inversion result.

[0107] The complete undirected wave spectrum of the fixed distance element described in step 7 is defined as S(r0,f wave ), which is calculated as follows:

[0108]

[0109] Where N represents the number of radar illumination azimuth angles.

[0110] The two wave parameters of significant wave height and mean wave period mentioned in step 7 are defined as H s 、T av , which can be obtained through the complete undirected wave spectrum S(r0,f wave ) is obtained and calculated as follows:

[0111]

[0112]

[0113]

[0114] Among them, m0 is the zero-order moment of the wave spectrum, m1 is the first-order moment of the wave spectrum, and m n is the nth moment of the wave spectrum and n=0,1,…, is the nth power of the wave frequency, df wave is the differential of the wave frequency.

[0115] The advantage of the above method flow is that the influence of wave breaking can be effectively removed by using only time domain data for correlation processing, thereby improving the accuracy of microwave radar wave inversion. Compared with the space-time domain processing method, the method proposed in the present invention requires a small amount of data and is easier to obtain. In addition, the method is simple to operate, highly flexible, and can adapt to complex and changeable marine environments, and has great research and application value.

[0116] As an example, there are N = 6 radar illumination azimuths, the 70th range element is selected, the range resolution is 7.5m, then r0 = 70 × 7.5m = 525m, the time series t has 256 points, the time resolution is 0.526s, the constraint factor β is set to 0.8, and the attached Figure 2 This is the time Doppler spectrum when the sea conditions are more severe. It is the time when wave breaking occurs frequently, causing the Doppler spectrum to broaden to the right. The white dotted lines represent the left and right bandwidth boundary frequencies of the ocean echo determined according to step 1, and the white solid lines represent the corrected left and right bandwidth boundary frequencies determined according to step 4. The re-determined bandwidth boundary frequencies do not include the broadening caused by wave breaking, and it can be considered that the impact of breaking has been eliminated. The unprocessed frequency shift can be obtained by the spectral moment method within the left and right bandwidth boundary frequencies of the ocean echo determined according to step 1. The frequency shift after time domain processing can be obtained by the spectral moment method within the left and right bandwidth boundary frequencies of the ocean echo determined according to step 4. The wavelength of the electromagnetic wave emitted by the S-band radar is λ0≈0.11m. The velocity time series before processing and after time domain processing can be obtained through the Doppler effect. The comparison after detrending is shown in the attached figure. Figure 3 As shown. Water depth d = 18m, antenna height H = 40m, so the antenna incident angle θ = cos -1 (H / r0), the wave spectrum of a fixed distance element on a certain radar azimuth is shown in the following figure Figure 4 As shown, it can be found that after processing using the time domain method proposed in the present invention, the low-frequency component of the wave spectrum is significantly reduced, and the inverted average wave period is also relatively consistent with the observation value of the buoy.

[0117] The ocean wave parameter inversion method based on the time Doppler spectrum of the S-band wave measuring radar described in the present invention starts from the influence of wave breaking on the Doppler spectrum and uses the time domain data of radar observation for correlation processing. The measured data results show that the method proposed by the present invention can effectively eliminate the influence of wave breaking using only time domain data, thereby improving the inversion accuracy of microwave radar ocean wave parameters and overcoming the problem of inconsistency of space-time domain data and thus failure of space-time domain processing methods due to factors such as obstruction and large changes in seabed topography. The method uses a small amount of data, is simple to operate, has high flexibility, and has broad application prospects.

[0118] In specific implementation, the method proposed in the technical solution of the present invention can be automatically run by those skilled in the art using computer software technology. System devices that implement the method, such as computer-readable storage media that store the corresponding computer program of the technical solution of the present invention and computer equipment that runs the corresponding computer program, should also be within the scope of protection of the present invention.

[0119] In some possible embodiments, a wave inversion system based on the time Doppler spectrum of an S-band wave measurement radar is provided, comprising a processor and a memory, wherein the memory is used to store program instructions, and the processor is used to call the stored instructions in the memory to execute the wave inversion method based on the time Doppler spectrum of an S-band wave measurement radar as described above.

[0120] In some possible embodiments, a wave inversion system based on the time Doppler spectrum of an S-band wave measurement radar is provided, comprising a readable storage medium on which a computer program is stored. When the computer program is executed, the wave inversion method based on the time Doppler spectrum of an S-band wave measurement radar as described above is implemented.

[0121] The above description is only a detailed description of the present invention in combination with specific implementation examples, and does not limit the scope of the present invention. Any use of the technology described in the present invention directly or indirectly in other related technical fields should be considered within the scope of protection of the present invention.

Claims

1. A method for inverting ocean waves based on the time Doppler spectrum of an S-band wave measuring radar, characterized by: The following steps are included: Step 1: At each radar illumination azimuth, at a fixed range element and at a fixed time point, a single echo Doppler spectrum is obtained. A corresponding threshold is set for the single Doppler spectrum, and the left and right bandwidth boundary frequencies of the ocean echo signal in the single Doppler spectrum are estimated by comparing the thresholds, thereby obtaining the bandwidth frequency of the single Doppler spectrum. Step 2: At each radar illumination azimuth, a fixed range element is used to obtain a time Doppler spectrum, and the average bandwidth frequency of the entire time Doppler spectrum is calculated based on the bandwidth frequency of a single Doppler spectrum in the time Doppler spectrum; Step 3: Wave breaking will broaden the Doppler spectrum. A constraint factor is added to the average bandwidth frequency of the time Doppler spectrum of the fixed range element to obtain the corrected average bandwidth frequency. Step 4: Determine the broadening of a single Doppler spectrum. If it broadens to the right, redefine the right bandwidth boundary frequency based on the left bandwidth boundary frequency and the corrected average bandwidth frequency. If it broadens to the left, redefine the left bandwidth boundary frequency based on the right bandwidth boundary frequency and the corrected average bandwidth frequency. The redetermined bandwidth boundary frequency does not include the broadening portion caused by wave breaking. Step 5: Within the re-determined bandwidth boundary frequency, the frequency shift of a single Doppler spectrum is obtained using the spectral moment method, and then the velocity at the fixed range element and fixed time point at the radar illumination azimuth is obtained. For the time Doppler spectrum of the fixed range element, a velocity time series is obtained, and the influence of other velocity components is eliminated, and detrending processing is performed; Step 6: Based on the linear wave theory of coherent microwave radar, the wave spectrum at the radar illumination direction angle is obtained according to the velocity time series of the fixed range element; Step 7: The wave spectra at each radar illumination angle are fused to obtain a complete undirected wave spectrum, and the wave parameters are obtained through the undirected wave spectrum to obtain the wave inversion result.

2. The ocean wave inversion method based on S-band wave radar time Doppler spectrum according to claim 1, characterized in that: In step 1, set It represents the nth radar illumination azimuth. The Doppler spectrum of a single echo at a fixed distance element and a fixed time point on the radar illumination azimuth is defined as Where r0 represents the radial distance between the fixed range element and the radar, t i represents a fixed time point, and f represents the Doppler frequency caused by the motion of the waves relative to the radar; The threshold of a single Doppler spectrum is defined as κ, and the calculation formula is, Among them A noise Represents the average amplitude of the noise floor in a single Doppler spectrum, and max() represents the maximum value; The left bandwidth boundary frequency of the ocean echo signal in a single Doppler spectrum is defined as The determination method is to first determine the maximum amplitude of a single Doppler spectrum, start from the maximum amplitude and traverse to the left, if the amplitude of a continuous segment is less than or equal to (κ+A noise ), the Doppler frequency corresponding to the leftmost amplitude of the segment is determined as the left bandwidth boundary frequency of the single Doppler spectrum; The right bandwidth boundary frequency of the ocean echo signal in a single Doppler spectrum is defined as The determination method is to first determine the maximum amplitude of a single Doppler spectrum, start from the maximum amplitude and traverse to the right, if the amplitude of a continuous segment is less than or equal to (κ+A noise ), the Doppler frequency corresponding to the rightmost amplitude of the segment is determined as the right bandwidth boundary frequency of the single Doppler spectrum; Bandwidth frequency of a single Doppler spectrum The calculation method is 3. The ocean wave inversion method based on S-band wave radar time Doppler spectrum according to claim 2, characterized in that: In step 2, the average bandwidth frequency of the entire time Doppler spectrum is expressed as ABW, which is calculated as follows: Where P is the number of time series points.

4. The ocean wave inversion method based on S-band wave radar time Doppler spectrum according to claim 3, characterized in that: In step 3, the constraint factor for correcting the average bandwidth frequency of the time Doppler spectrum is defined as β, and 0<β≤1; The corrected average bandwidth frequency of the time Doppler spectrum is defined as MABW, which is calculated as follows: MABW=βABW.

5. The ocean wave inversion method based on S-band wave radar time Doppler spectrum according to claim 4, characterized in that: In step 4, the left bandwidth boundary frequency of the re-determined single Doppler spectrum is defined as For a single Doppler spectrum, the left bandwidth boundary frequency is redefined The calculation method is as follows, In step 4, the right bandwidth boundary frequency of the re-determined single Doppler spectrum is defined as For a single Doppler spectrum, the right bandwidth boundary frequency is redefined The calculation method is as follows, 6. The ocean wave inversion method based on S-band wave radar time Doppler spectrum according to claim 5, characterized in that: In step 5, the frequency shift of a single Doppler spectrum is defined as Obtained by spectral moment method within the redefined bandwidth boundary frequency The calculation method is, Velocity at a fixed distance element and a fixed time point on the radar azimuth It is derived from the Doppler effect, that is, Where λ0 represents the wavelength of electromagnetic wave; For a fixed range element, the time Doppler spectrum The corresponding speed time series is defined as The detrending term of the speed time series is processed as follows: Among them, mean() is the average value, is the processed velocity time series.

7. The ocean wave inversion method based on S-band wave radar time Doppler spectrum according to claim 6, characterized in that: In step 6, the wave spectrum of a fixed distance element on the radar illumination azimuth is defined as Among them, f wave represents the wave frequency, which is related to the time series t. According to the linear wave theory of coherent microwave radar, the conversion relationship between the velocity time series of a fixed distance element on the radar illumination azimuth and the wave spectrum of a fixed distance element is: Among them, FFT represents fast Fourier transform, and the transfer function TF is expressed as follows, In the above formula, k represents the wave number, d represents the water depth at a fixed distance, ω represents the wave angular frequency, and Δf wave represents the wave frequency resolution, and θ represents the antenna incidence angle.

8. The ocean wave inversion method based on S-band wave radar time Doppler spectrum according to claim 7, characterized in that: In step 7, the complete undirected wave spectrum of a fixed distance element is defined as S(r0,f wave ), N represents the number of radar azimuth angles, and is calculated as follows: The two wave parameters of significant wave height and mean wave period mentioned in step 7 are defined as H s 、T av , through the complete undirected wave spectrum S(r0,f wave ) is obtained, and the calculation is as follows, Among them, m0 is the zero-order moment of the wave spectrum, m1 is the first-order moment of the wave spectrum, and m n is the nth moment of the wave spectrum and n=0,1,…, is the nth power of the wave frequency, df wave is the differential of the wave frequency.

9. A wave inversion system based on S-band wave radar time Doppler spectrum, characterized by: Used to implement the wave inversion method based on S-band wave measurement radar time Doppler spectrum as described in any one of claims 1-8.

10. A wave inversion device based on the time Doppler spectrum of an S-band wave measuring radar, characterized by: The invention comprises a processor and a memory, the memory is used to store program instructions, and the processor is used to call the stored instructions in the memory to execute the wave inversion method based on the time Doppler spectrum of the S-band wave measuring radar as described in any one of claims 1 to 8.

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