Sea wave directional spectrum inversion method based on FMCW millimeter wave MIMO radar

Abstract

The invention relates to the technical field of radar measurement, in particular to a wave direction spectrum inversion method based on an FMCW millimeter wave MIMO radar, which comprises the following steps: determining the required radar ranging resolution and ranging range so as to set the waveform parameters of the FMCW millimeter wave MIMO radar; the FMCW millimeter wave MIMO radar is arranged on an observation sea surface so as to measure radar echo data; preprocessing the radar echo data to obtain a radar echo data power spectrum; processing the radar echo data power spectrum by using a beam forming technology to obtain a wave height time sequence of a sea surface observation point in a required direction, and calculating a sea wave cross spectrum of the observation area according to the wave height time sequence of the sea surface observation point in the required direction; and calculating the sea wave direction spectrum according to the sea wave cross spectrum of the observation area and the preset observation point array space arrangement. Therefore, the problems of high equipment cost, high deployment difficulty, inconvenience in maintenance and the like of the traditional sea wave direction measurement are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of radar measurement, and particularly relates to a method for retrieving the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar. Background Art

[0002] At present, there are still many limitations in the observation methods of ocean wave direction spectra in practical applications. Traditional methods for measuring ocean wave direction spectra mainly rely on technical means such as buoys, satellite remote sensing, and radar remote sensing. However, these methods often face the following problems in practical applications: First, although buoy measurements can provide high-precision ocean wave data, their spatial coverage is limited, and the deployment and maintenance costs are relatively high, making it difficult to meet the needs of large-scale ocean environmental monitoring. Buoys usually require regular maintenance, especially in harsh ocean environments, where the risk of equipment damage and data loss is relatively high, which limits the practical application of buoy measurements to a certain extent. Second, although satellite remote sensing technology can achieve large-scale ocean wave observations, its spatial resolution and temporal resolution are limited, and it is greatly affected by weather conditions (such as cloud cover), resulting in insufficient continuity and reliability of data acquisition. When satellite remote sensing technology obtains ocean wave direction spectrum information, it often relies on complex inversion algorithms, which may be interfered by factors such as sea surface wind waves and cloud cover in practical applications, leading to an increase in the uncertainty of measurement results. In addition, the temporal resolution of satellite remote sensing technology is usually low, making it difficult to capture rapidly changing ocean wave dynamic processes, which to a certain extent limits its application in real-time monitoring and emergency response. Summary of the Invention

[0003] The present invention provides a method for retrieving the ocean wave direction spectrum based on an FMCW (Frequency Modulated Continuous Wave) millimeter-wave MIMO (Multiple-Input Multiple-Output) radar, so as to solve the problems faced by traditional ocean wave direction measurements, such as high equipment costs, difficult deployment, and inconvenient maintenance.

[0004] An embodiment of the first aspect of the present invention provides a method for retrieving the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar, comprising the following steps: determining the required radar ranging resolution and ranging range, and setting the waveform parameters of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar according to the radar ranging resolution and the ranging range; placing the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters on the observation sea surface according to the preset placement requirements to obtain radar echo data; preprocessing the radar echo data to obtain the power spectrum of the radar echo data; using beamforming technology to process the power spectrum of the radar echo data to obtain the wave height time series of the sea surface observation points in the required direction, and calculating the ocean wave cross-spectrum of the observation area according to the wave height time series of the sea surface observation points in the required direction; calculating the ocean wave direction spectrum according to the ocean wave cross-spectrum of the observation area and the preset spatial arrangement of the observation point array, wherein the ocean wave direction spectrum includes the direction distribution spectrum of the low-frequency segment of the ocean waves in the observation area and the main wave direction of the observation area.

[0005] Optionally, when the ranging range is 1 - 25 m and the wave height accuracy is 5 cm, set the frequency modulation slope of the frequency-modulated continuous-wave signal of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar to 60 MHz / μs, the duration of the frequency-modulated continuous-wave signal to 60 μs, the sampling frequency of the analog-to-digital converter to 10 MSPS, one frame of results consists of 16 cycles, 12 transmitting antennas work sequentially in each cycle, and the frame period is 100 ms.

[0006] Optionally, the preset placement requirements are as follows:

[0007] Install the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters in a wide sea area, and make the RF board of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters parallel to the sea surface so that the electromagnetic wave irradiates the sea surface vertically;

[0008] The distance between different sea surface observation points is determined according to the installation height and observation angle of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters, and the distance between any two observation points should be less than 1 / 2 of the observation wavelength.

[0009] Optionally, the preprocessing of the radar echo data to obtain the power spectrum of the radar echo data includes:

[0010] Multiplying the radar echo data by a calibration matrix to obtain calibrated radar echo data;

[0011] Performing a fast Fourier transform on the calibrated radar echo data to obtain the power spectrum of the radar echo data.

[0012] Optionally, processing the power spectrum of the radar echo data using beamforming technology to obtain the wave height time series of the sea surface observation points in the required direction, and calculating the sea wave cross-spectrum of the observation area according to the wave height time series of the sea surface observation points in the required direction, including:

[0013] Extract the maximum value points and their index values in the power spectrum of the radar echo data, and multiply the index values by the radar ranging resolution to obtain the vertical distance between the radar and the sea surface at each observation moment;

[0014] Perform a mean calculation on the vertical distances between the radar and the sea surface at each observation moment to obtain the standard distance between the radar and the sea level;

[0015] Construct a three-dimensional rectangular coordinate system with the standard distance between the radar directly below the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar after setting the waveform parameters and the sea level as the origin;

[0016] Based on the three-dimensional rectangular coordinate system, subtract the standard distance between the radar and the sea level from the vertical distances between the radar and the sea surface at each observation moment respectively to obtain the wave height time series of the radar vertical points; [[ID=##ID=14]]

[0017] Use beamforming technology to enhance the signal intensity in the power spectrum of the radar echo data, obtain the power spectrum after beamforming, and subtract the power spectrum after beamforming from the power spectrum of the radar echo data to obtain the difference power spectrum;

[0018] Extract the maximum value points and their index values in the difference power spectrum, and multiply the index values by the radar ranging resolution to obtain the slant range between the radar and the sea surface observation points in the required direction at each observation moment;

[0019] Project the slant range between the radar and the sea surface observation points in the required direction at each observation moment onto the z-axis in the three-dimensional rectangular coordinate system to obtain the vertical distance between the radar and the sea surface observation points in the required direction at each observation moment;

[0020] Subtract the standard distance between the radar and the sea level from the vertical distances between the radar and the sea surface observation points in the required direction at each observation moment respectively to obtain the wave height time series of the sea surface observation points in the required direction;

[0021] Draw the vertical point wave height time series diagram of the wave height time series of the radar vertical points and the wave height time series diagram in the required direction of the wave height time series of the sea surface observation points in the required direction respectively, and perform median filtering on the outliers in the vertical point wave height time series diagram and the wave height time series diagram in the required direction to obtain the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction;

[0022] Perform a fast Fourier transform on the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction to obtain the fast Fourier transform result;

[0023] Find the frequency band with the highest sea wave energy distribution at each observation point in the fast Fourier transform result, and sequentially conjugate multiply the Fourier transform results of every two points in order to obtain the sea wave cross spectrum of the observation area.

[0024] Optionally, the calculating the sea wave direction spectrum according to the sea wave cross spectrum of the observation area and the preset spatial arrangement of the observation point array includes:

[0025] Based on the Bayesian direction spectrum estimation method, calculate the direction distribution spectrum of the low-frequency band of the sea waves in the observation area according to the sea wave cross spectrum of the observation area and the preset spatial arrangement of the observation point array;

[0026] Analyze the wave direction distribution of each frequency band of the sea waves in the sea wave cross spectrum of the observation area to output a sea wave main direction-frequency diagram;

[0027] Determine the main wave direction of the observation area in the sea wave main direction-frequency diagram according to the direction distribution of the frequency band with the highest sea wave energy distribution at each observation point.

[0028] An embodiment of the second aspect of the present invention provides a sea wave direction spectrum inversion device based on an FMCW millimeter wave MIMO radar, including: a parameter setting module for determining the required radar ranging resolution and ranging range, and setting the waveform parameters of the frequency-modulated continuous wave millimeter wave multiple input multiple output radar according to the radar ranging resolution and the ranging range; an observation module for placing the frequency-modulated continuous wave millimeter wave multiple input multiple output radar with the waveform parameters set according to the preset placement requirements on the observation sea surface to measure radar echo data; a preprocessing module for preprocessing the radar echo data to obtain the radar echo data power spectrum; a first calculation module for using beamforming technology to process the radar echo data power spectrum to obtain the wave height time series of the sea surface observation points in the required direction, and calculating the sea wave cross spectrum of the observation area according to the wave height time series of the sea surface observation points in the required direction; a second calculation module for calculating the sea wave direction spectrum according to the sea wave cross spectrum of the observation area and the preset spatial arrangement of the observation point array, wherein the sea wave direction spectrum includes the direction distribution spectrum of the low-frequency band of the sea waves in the observation area and the main wave direction of the observation area.

[0029] An embodiment of the third aspect of the present invention provides an electronic device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to implement the sea wave direction spectrum inversion method based on an FMCW millimeter wave MIMO radar as described in the above embodiments.

[0030] In the fourth aspect of the present invention, an embodiment provides a computer program product, and when the computer program / instructions are executed by a processor, the above-mentioned method for inverting the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar is implemented.

[0031] In the fifth aspect of the present invention, an embodiment provides a computer-readable storage medium, and the computer-readable storage medium stores a computer program, and when the program is executed by a processor, the above-mentioned method for inverting the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar is implemented.

[0032] The method for inverting the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar proposed in the embodiments of the present invention solves the problems faced by traditional ocean wave direction measurement, such as high equipment cost, difficult deployment, and inconvenient maintenance. The equipment is simply installed, not affected by weather and ocean conditions, and can realize all-day and all-weather ocean wave observation; compared with other millimeter-wave radar inversion ocean wave reverse spectrum schemes, the present invention can achieve high-precision measurement of the ocean wave direction under the condition of only using one radar through the MIMO radar system and beamforming technology; the embodiments of the present invention can accurately measure the ocean wave direction distribution in each frequency band and determine the main wave direction in a simpler way by improving the data processing method and designing the ocean wave observation point array, making the FMCW millimeter-wave MIMO radar likely to become a new type of efficient observation device in the field of wave direction observation in the future; compared with the traditional wave direction inversion method, the scheme proposed in the embodiments of the present invention has high economic value, higher feasibility, better equipment maintainability, and high measurement accuracy, and has a wide range of application scenarios.

[0033] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0034] The above-mentioned and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0035] Figure 1 is a flowchart of a method for inverting the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar provided by an embodiment of the present invention;

[0036] Figure 2 is a diagram of an ocean surface observation point array provided by a specific embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of the input directional ocean wave spectrum during simulation provided by a specific embodiment of the present invention;

[0038] Figure 4Schematic diagram of the simulated sea surface at a certain moment provided by a specific embodiment of the present invention;

[0039] Figure 5 Comparison diagram of the output directional distribution spectrum and the input directional distribution spectrum during simulation provided by a specific embodiment of the present invention;

[0040] Figure 6 Main wave direction - frequency diagram of the waves output during simulation provided by a specific embodiment of the present invention;

[0041] Figure 7 Time - series diagram of the wave surface height at the detection point directly below the radar during the wave pool experiment provided by another specific embodiment of the present invention;

[0042] Figure 8 Schematic diagram of the output directional distribution spectrum during the wave - making pool experiment provided by another specific embodiment of the present invention;

[0043] Figure 9 Block diagram of a device for retrieving the sea - wave direction spectrum based on an FMCW millimeter - wave MIMO radar provided by an embodiment of the present invention;

[0044] Figure 10 Schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. Detailed implementation manners

[0045] The embodiments of the present invention are described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0046] The method for retrieving the sea - wave direction spectrum based on an FMCW millimeter - wave MIMO radar according to the embodiments of the present invention is described below with reference to the accompanying drawings. In view of the problems mentioned in the above - mentioned background technology that traditional sea - wave direction measurement faces high equipment costs, difficult deployment, and inconvenient maintenance, the present invention provides a method for retrieving the sea - wave direction spectrum based on an FMCW millimeter - wave MIMO radar, and determines a data acquisition and data - processing process to calculate the accurate sea - wave direction spectrum and the main wave direction.

[0047] It can be understood that as an emerging means of detecting ocean wave directions, millimeter-wave radar exhibits great application potential. Millimeter-wave radar features high resolution and all-weather operation, and can effectively overcome many limitations of traditional methods. By emitting high-frequency electromagnetic waves and receiving sea surface reflection signals, millimeter-wave radar can achieve high-precision measurement of the ocean wave direction spectrum. Compared with traditional methods, millimeter-wave radar can not only provide more detailed ocean wave direction spectrum information, but also obtain real-time three-dimensional spatial distribution information of ocean waves, providing richer and more comprehensive data support for ocean dynamics research. In addition, the cost of millimeter-wave radar equipment is relatively low, and it is easy to integrate and deploy, providing feasibility for large-scale ocean environment monitoring.

[0048] The advantages of millimeter-wave radar in ocean wave direction spectrum observation are mainly reflected in the following aspects: First, millimeter-wave radar has high spatial resolution and time resolution, and can capture fast-changing ocean wave dynamics processes, providing strong support for real-time monitoring and emergency response. Second, millimeter-wave radar has the ability to work all-weather and can operate stably under various weather conditions, overcoming the dependence of traditional methods on weather conditions. In addition, the antenna size of millimeter-wave radar is small, greatly reducing the installation and maintenance difficulty of the equipment. In the future, with the further development and application promotion of millimeter-wave radar technology, its application prospect in the field of ocean wave direction spectrum observation will be broader.

[0049] Specifically, Figure 1 FIG. is a schematic flow chart of a method for retrieving ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar provided by an embodiment of the present invention.

[0050] As Figure 1 shown, the method for retrieving ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar includes the following steps:

[0051] In step S101, determine the required radar ranging resolution and ranging range, and set the waveform parameters of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar according to the radar ranging resolution and ranging range.

[0052] In some embodiments, when the ranging range is 1 - 25 m and the wave height accuracy is 5 cm, set the frequency modulation slope of the frequency-modulated continuous-wave signal of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar to 60 MHz / μs, the duration of the frequency-modulated continuous-wave signal to 60 μs, the sampling frequency of the analog-to-digital converter to 10 MSPS, one frame result consists of 16 cycles, 12 transmitting antennas work sequentially in each cycle, and the frame period is 100 ms.

[0053] In the actual execution process, the frequency of the radar's transmitted signal linearly increases with time. This signal has a certain initial frequency and operating frequency band. When the signal frequency reaches the limit of the operating frequency band, it will pause and start linear frequency modulation again from the initial frequency in the next cycle. This signal is also called a linearly frequency-modulated pulse. The time-frequency relationship of this signal can be expressed by the following formula:

[0054]

[0055] This signal can be expressed as:

[0056]

[0057] In the formula, A represents the amplitude of the transmitted signal, f c is the carrier frequency, t is the sea surface time, B is the modulation bandwidth, is the initial phase of the transmitted signal. Assume there is a stationary target at a distance R from the radar. Then the radar signal is received by the receiving antenna after The echo signal at this time can be expressed as:

[0058]

[0059] In the formula, K r is the object reflection coefficient, w(t) is the additive Gaussian white noise in the radar signal propagation channel, c is the speed of light, and T is the frequency modulation period. After the radar receives the echo signal, it shifts the phase of the signal transmitted by the transmitting antenna by half a cycle and mixes it with the received echo signal. After passing through a low-pass filter, the intermediate frequency signal and the accompanying noise can be obtained. The intermediate frequency signal can be expressed as:

[0060]

[0061] In actual situations is a small quantity, so the τ 2 term can be ignored. Then the above formula can be simplified to:

[0062]

[0063] From this, it can be seen that the frequency of the intermediate frequency signal is related to the distance between the radar and the target. By performing a fast Fourier transform on the sampled discrete intermediate frequency signal to obtain the discrete spectrum of the intermediate frequency signal, and analyzing the spectrum, the distance between the radar and the object can be deduced.

[0064] When multiple targets appear within the radar beam range, echo signals with different time delays will be generated. After mixing and filtering the echo signals, intermediate-frequency signals with different frequencies will be obtained. By analyzing the frequency components of the signals, the distance information of different targets can be obtained. When using a millimeter-wave radar to observe the sea surface, the distance between the radar and different observation points will be affected by two factors: the signal angle and the sea surface wave height. Therefore, when the beamforming technology is used in the embodiments of the present invention to improve the signal-to-noise ratio at the angle where the observation point is located, the wave height situation of the observation point at this time can be analyzed according to the frequency information of the echo signal.

[0065] To meet the needs of sea surface observation, the waveform parameters of the FMCW millimeter-wave MIMO radar set in the embodiments of the present invention are as follows: the frequency modulation slope of the frequency-modulated continuous-wave signal Chirp is set to 60 MHz / us, the duration of Chirp is 60 us, the sampling frequency of the analog-to-digital converter is 10 MSPS, one frame of results consists of 16 loop cycles, 12 transmitting antennas work in sequence in each loop, the frame period is 100 ms, the number of sampling points for a single chirp is 512 points. At this time, the distance resolution of the radar is 5 cm, and the maximum detection distance is 25 m.

[0066] In step S102, the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set is placed on the observed sea surface according to the preset placement requirements to obtain radar echo data.

[0067] In some embodiments, the preset placement requirements are as follows:

[0068] The frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set is installed in a wide sea area, and the RF board of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set is parallel to the sea level, so that the electromagnetic wave irradiates the sea surface vertically;

[0069] The distance between different sea surface observation points is determined by the installation height and observation angle of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set, and the distance between any two observation points should be less than 1 / 2 of the observation wavelength.

[0070] In the actual implementation process, during the process of wave observation, an open sea area should be selected to avoid the influence of structures such as bridges or ships on the propagation of electromagnetic waves and the propagation of waves. At the same time, an appropriate installation height should be determined. The distance between different sea surface observation points is determined by the installation height and observation angle of the FMCW millimeter-wave MIMO radar after setting the waveform parameters. The distance between any two observation points is preferably less than 1 / 2 of the main wavelength of the observed waves. The RF board of the FMCW millimeter-wave MIMO radar after setting the waveform parameters should be parallel to the sea level, that is, to make the electromagnetic waves vertically irradiate the sea surface. If there is an inclination in the installation of the FMCW millimeter-wave MIMO radar after setting the waveform parameters, it may affect the measurement accuracy.

[0071] In step S103, the radar echo data is preprocessed to obtain the power spectrum of the radar echo data.

[0072] In some embodiments, preprocessing the radar echo data to obtain the power spectrum of the radar echo data includes:

[0073] Multiplying the radar echo data by a calibration matrix to obtain calibrated radar echo data;

[0074] Performing a fast Fourier transform on the calibrated radar echo data to obtain the power spectrum of the radar echo data.

[0075] In the actual implementation process, due to a series of factors such as the deviation of the antenna distance in the actual evaluation board (which may not be half a wavelength), calibration can, to a certain extent, help improve the accuracy of radar ranging. Therefore, in the embodiments of the present invention, the radar echo data is multiplied by a calibration matrix to calibrate the radar echo data; the calibrated data is subjected to a fast Fourier transform to obtain the power spectrum of the radar echo data, thereby completing the preprocessing of the radar echo data.

[0076] In step S104, beamforming technology is used to process the power spectrum of the radar echo data to obtain the wave height time series of the sea surface observation point in the required direction, and the cross-spectrum of the waves in the observation area is calculated based on the wave height time series of the sea surface observation point in the required direction.

[0077] In some embodiments, using beamforming technology to process the power spectrum of the radar echo data to obtain the wave height time series of the sea surface observation point in the required direction, and calculating the cross-spectrum of the waves in the observation area based on the wave height time series of the sea surface observation point in the required direction includes:

[0078] Extracting the maximum value point and its index value in the power spectrum of the radar echo data, and multiplying the index value by the radar ranging resolution to obtain the vertical distance between the radar and the sea surface at each observation moment;

[0079] Calculate the mean of the vertical distances between the radar and the sea surface at each observation time to obtain the standard distance between the radar and the sea level;

[0080] Construct a three-dimensional rectangular coordinate system with the standard distance between the point directly below the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar after setting the waveform parameters and the sea level as the origin;

[0081] Based on the three-dimensional rectangular coordinate system, subtract the standard distance between the radar and the sea level from the vertical distance between the radar and the sea surface at each observation time to obtain the wave height time series of the radar vertical point;

[0082] Use beamforming technology to enhance the signal intensity in the power spectrum of the radar echo data, obtain the power spectrum after beamforming, and subtract the power spectrum after beamforming from the power spectrum of the radar echo data to obtain the difference power spectrum;

[0083] Extract the maximum point and its index value in the difference power spectrum, and multiply the index value by the radar ranging resolution to obtain the slant range between the radar and the sea surface observation point in the required direction at each observation time;

[0084] Project the slant range between the radar and the sea surface observation point in the required direction at each observation time onto the z-axis in the three-dimensional rectangular coordinate system to obtain the vertical distance between the radar and the sea surface observation point in the required direction at each observation time;

[0085] Subtract the standard distance between the radar and the sea level from the vertical distance between the radar and the sea surface observation point in the required direction at each observation time to obtain the wave height time series of the sea surface observation point in the required direction;

[0086] Draw the vertical point wave height time series diagram of the wave height time series of the radar vertical point and the wave height time series diagram in the required direction of the wave height time series of the sea surface observation point in the required direction respectively, and perform median filtering on the outliers in the vertical point wave height time series diagram and the wave height time series diagram in the required direction to obtain the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction;

[0087] Perform fast Fourier transform on the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction to obtain the fast Fourier transform result;

[0088] Find the frequency band with the highest sea wave energy distribution at each observation point in the fast Fourier transform result, and multiply the Fourier transform results of every two points in sequence to obtain the cross spectrum of the sea waves in the observation area.

[0089] In the actual execution process, when there are multiple targets within the radar beam coverage area, these targets will reflect echo signals with different time delays; after mixing and filtering these echo signals, intermediate-frequency signals with different frequencies can be obtained; by analyzing the frequency characteristics of the signals, the distance information of each target can be determined; when using a millimeter-wave radar to observe the sea surface, the distance between the radar and different observation points is not only affected by the signal incident angle but also closely related to the sea surface wave height. Therefore, when beamforming technology is used to enhance the signal-to-noise ratio in the target area, the current wave height situation of the observation point can be deduced by analyzing the frequency characteristics of the echo signals.

[0090] Therefore, in the embodiment of the present invention, the maximum value point of each frame of radar echo power spectrum is extracted from the radar echo data power spectrum, and the index value of the maximum value point is multiplied by the radar ranging resolution. The obtained value is the vertical distance between the radar and the sea surface at each observation moment. The average value of the vertical distances between the radar and the sea surface at each observation moment is calculated to obtain the standard distance R between the radar and the sea level. mean 。

[0091] Taking the point directly below the radar at R mean as the origin, that is, regarded as the sea level point, the line where R mean is located is the z-axis, the xOy plane is parallel to the sea level, a three-dimensional rectangular coordinate system is established, and the standard distance R mean minus the vertical distance between the radar and the sea surface at each observation moment, the wave height time series h of the radar vertical point can be obtained 1i , i ∈ [1,..., N].

[0092] After obtaining the wave height time series of the radar vertical point, it can be plotted through a plotting software to obtain the wave height time series diagram of the vertical point, so as to observe the amplitude and period of the sea wave movement.

[0093] Using beamforming technology, the signal strength of the echo signal in a certain direction in the radar echo data power spectrum is enhanced, and the difference spectrum is obtained by subtracting the power spectrum after beamforming from the total power spectrum of the radar echo data. The maximum value point of the obtained difference spectrum is taken, and the index value of the maximum value point is multiplied by the radar ranging resolution. The obtained value is the slant range between the radar and the sea surface observation point in the required direction at each observation moment. Projecting the slant range onto the z-axis in the three-dimensional rectangular coordinate system to obtain the vertical distance R' between the radar and the sea surface observation point in the required direction at each observation moment mi , i ∈ [1,..., N], and then subtracting R' mean from the standard distance R mi to obtain the wave height time series h of the sea surface observation point in the required direction mi , i ∈ [1,..., N].

[0094] It should be noted that beamforming technology sums up the data collected by each element of the array after linear time-invariant filtering to obtain the beam output. Assuming that the received signal x(n) of the array is an M*N-dimensional matrix, where M is the number of elements and N is the number of sampling points, the beamforming weight vector is an M*1-dimensional vector with respect to . For different azimuth angles and elevation angles, that is, , there are different weight vectors. The beamforming output y(n) can be obtained by the following formula:

[0095]

[0096] Beamforming technology includes various types. The one used in the present invention is conventional beamforming, and the value of conventional beamforming is:

[0097]

[0098] Among them, is the steering vector, and M is the number of elements. Conventional beamforming is also called delay-and-sum beamforming. When a far-field signal is incident on the array, time delays are generated among the elements due to different spatial arrangements. Conventional beamforming performs the opposite time-delay compensation and then adds them up, so that the signals in the desired direction are in-phase superimposed, while the noise and interference are not in-phase superimposed, thereby improving the output signal-to-noise ratio. For each , the beamforming output result in its direction can be obtained. After obtaining the beamforming output result, its power spectrum is calculated and subtracted from the power spectrum of the radar echo data to obtain the difference power spectrum. The significance of calculating the difference power spectrum is to further remove the interference information in other directions. Since beamforming improves the signal-to-noise ratio in a specific direction, it will be more obvious in the difference spectrum.

[0099] After obtaining the wave height time series of the sea surface observation points in the required direction, a wave height time series diagram in the required direction can be drawn through a drawing software, and median filtering is performed on the outliers in the vertical point wave height time series diagram and the wave height time series diagram in the required direction to obtain the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction.

[0100] Furthermore, the fast Fourier transform is performed on the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction. According to the Fourier transform result, the frequency band with the highest sea wave energy distribution at each observation point is found. At the same time, the Fourier transform results of every two points are conjugated and multiplied in sequence to obtain the cross spectrum of the sea waves in the observation area.

[0101] Such as Figure 2As shown in the figure, when calculating the cross-spectrum of ocean waves in the observation area, since there are 9 points in the preset sea surface observation point array in the embodiment of the present invention, and the cross-spectrum requires conjugate multiplication of the Fourier transform results of every two points, there are 36 groups of cross-spectrum results available for inverting the ocean wave direction spectrum. At the same time, since the frame duration of the FMCW millimeter-wave MIMO radar is set to 100 ms in the early stage of the embodiment of the present invention, it can be considered that the observation frequency of the FMCW millimeter-wave MIMO radar for the sea surface is 10 Hz, while the frequencies of ocean waves mostly concentrate between 0.1 - 0.3 Hz. It can be seen that the high observation frequency of the FMCW millimeter-wave MIMO radar will result in a low resolution of the fast Fourier transform result, thus affecting the effect of inverting the ocean wave direction spectrum. Therefore, in the embodiment of the present invention, the wave height data will be grouped before calculating the fast Fourier transform, and the specific implementation steps are as follows:

[0102] Data can be divided into groups at intervals of 3 points. In this way, for a single observation point, the data can be divided into 4 groups, that is

[0103] After such implementation, the observation frequency of the FMCW millimeter-wave MIMO radar is reduced to 2.5 Hz. At this time, a higher ocean wave frequency resolution can be achieved with fewer observation points. After performing the fast Fourier transform on each group of data, the average of the results of the four groups can be used as the discrete spectrum of this observation point.

[0104] In step S105, the ocean wave direction spectrum is calculated according to the cross-spectrum of ocean waves in the observation area and the spatial arrangement of the preset observation point array. Among them, the ocean wave direction spectrum includes the direction distribution spectrum of the low-frequency band of ocean waves in the observation area and the main wave direction of the observation area.

[0105] In some embodiments, calculating the ocean wave direction spectrum according to the cross-spectrum of ocean waves in the observation area and the spatial arrangement of the preset observation point array includes:

[0106] Based on the Bayesian direction spectrum estimation method, the direction distribution spectrum of the low-frequency band of ocean waves in the observation area is calculated according to the cross-spectrum of ocean waves in the observation area and the spatial arrangement of the preset observation point array;

[0107] Analyze the wave direction distribution of each frequency band of ocean waves in the cross-spectrum of ocean waves in the observation area to output the ocean wave main direction - frequency diagram;

[0108] Determine the main wave direction of the observation area in the ocean wave main direction - frequency diagram according to the direction distribution of the frequency band with the highest ocean wave energy distribution at each observation point.

[0109] In the actual implementation process, based on the Bayesian direction spectrum estimation method, the direction distribution spectrum of the low-frequency band of ocean waves in the observation area is calculated according to the cross-spectrum of ocean waves in the observation area and the spatial arrangement of the preset observation point array. Among them, when applying the Bayesian direction spectrum estimation method to measure the direction distribution spectrum of ocean waves, at least three or more ocean wave height measurement points are required. At the same time, the more prediction points there are, the higher the accuracy of the direction spectrum estimation, and the fewer the number of iterations required to obtain the correct direction spectrum. However, this also means a larger amount of data, which will reduce the efficiency of the algorithm operation to a certain extent.

[0110] As Figure 2 shown, in the embodiment of the present invention, through the beamforming technology mentioned above, a total of nine points of observation data can be obtained. Among them, there is a point directly below the radar, and the other eight points are arranged in a square, with a distance of 1 meter between every two adjacent points.

[0111] The Bayesian direction spectrum estimation method is specifically manifested as follows. Assuming that the wave amplitude is composed of the superposition of multiple component waves, it can be known that the cross-spectrum between any two wave characteristics is equal to the Fourier transform of the product of the transfer function between the corresponding wave characteristics and the wave surface and the wave direction spectrum, that is:

[0112]

[0113] Among them, is the cross-spectrum between two wave characteristics m and n, ω is the ocean wave frequency, k is the wave number vector, H m and H n are the transfer functions of two wave characteristics. In the present invention, since the detected quantity is only the sea surface wave height, the values of the transfer functions are all 1. G(θ|k) is the direction spectrum expressed in terms of wave number. The inverse transform of the above formula is used to represent the direction spectrum with an expression containing the cross-spectrum. Since G(θ|ω)>0 always holds, it is discretized:

[0114] lnG(θ k |ω) = x k (ω)

[0115]

[0116] Then the original formula can be expressed as:

[0117]

[0118] When the number of estimated directions is large:

[0119] a ik = exp{-ik(x n -x m )}Δθ

[0120] Then the original formula can be further simplified as:

[0121]

[0122] Physically speaking, the value of the direction distribution function should be smooth and continuous, which means that the second-order difference of the estimated value should be close to 0. Thus, by Bayesian statistical method, the estimation of the direction distribution function is reduced to minimizing the following formula:

[0123]

[0124] where is the simplified result of the cross-spectrum, K is the total number of directions, and μ is the second-order difference hyperparameter.

[0125] During the calculation, it is assumed that the initial distribution of the direction distribution function is substituted into the above formula, and the new distribution value is obtained by the least squares method. Then, iterative calculation is carried out, and the solution corresponding to the minimum value of ABIC is the final result.

[0126] Finally, analyze the wave direction distribution of each frequency band in the sea wave cross-spectrum of the observation area to output the sea wave main direction-frequency diagram, and determine the main wave direction of the observation area according to the direction distribution of the frequency band with the highest energy distribution.

[0127] Next, the feasibility of the sea wave observation method based on FMCW millimeter-wave MIMO radar proposed in the embodiments of the present invention is analyzed through two specific simulation embodiments.

[0128] Based on the simulation, the feasibility of the above scheme is analyzed. First, the input directional sea wave spectrum is obtained by using the JONSWAP sea wave spectrum and the Longuet-Higgins direction distribution function. Then, the simulation sea surface is obtained from the input directional sea wave spectrum through the single superposition method. Input the directional sea wave spectrum and the simulation sea surface situation at a certain moment as shown in Figure 3 and 4 . After obtaining the simulation sea surface, determine the specific positions of the observation points according to the array arrangement of the observation points, and record the time series of the wave heights of these observation points. After obtaining the wave height data of these observation points, perform fast Fourier transform on the wave height time series obtained from the eight observation points respectively, and calculate the sea wave cross-spectrum of the observation area according to the fast Fourier transform results. Based on the Bayesian direction spectrum estimation method, according to the calculated sea wave cross-spectrum and the preset spatial arrangement of the observation point array, calculate the direction distribution spectrum of each frequency band, find the maximum point of the direction distribution of each frequency band and record it. Finally, output the sea wave main direction-frequency diagram and the main wave direction of the observation area. As shown in Figure 5 , compare the direction distribution spectrum of the frequency band with the highest energy distribution with the input direction distribution spectrum, and the overall error is within 1%. It can be seen that the inversion effect of the sea wave direction distribution spectrum is good, and at the same time, the sea wave main direction-frequency diagram shows that the judgment of the wave direction in the frequency band with energy distribution is basically correct.

[0129] Secondly, the proposed method for inverse calculation of ocean wave direction spectrum is verified through wave pool experiments. First, a high platform is built 15 meters above the pool and a radar is installed. The radar is started and waiting for the wave pool to start working. First, the wave height conditions within the observation points are detected. The wave height time series diagram of the detection center point is as Figure 6 shown, and it can be seen that there are obvious wave undulations. Then, the cross spectrum of ocean waves is calculated from the observation results at multiple points, and the ocean wave direction distribution spectrum within each frequency band is calculated according to the Bayesian direction spectrum estimation method. The ocean wave direction distribution diagram of the highest energy distribution frequency band is as Figure 8 shown. From the results, it can be known that the main wave direction of the ocean waves is at -110 degrees, and there is also a small distribution at 135 degrees. Through analysis, it can be seen that the judgment of the main wave direction is reasonable, and the echo of the ocean waves is detected to a certain extent. Through the analysis of the wave pool experiment results, it can be seen that using the FMCW millimeter-wave MIMO radar to inverse the ocean wave direction spectrum has a certain reliability.

[0130] In summary, according to the method for inverse calculation of ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar proposed in the embodiments of the present invention, the following beneficial effects are obtained:

[0131] (1) It solves the problems faced by traditional ocean wave direction measurement, such as high equipment cost, difficult deployment, and inconvenient maintenance. The equipment installation is simple, not affected by weather and ocean conditions, and can realize all-day and all-weather ocean wave observation;

[0132] (2) Compared with other millimeter-wave radar inverse ocean wave direction spectrum schemes, the present invention can achieve high-precision measurement of ocean wave direction under the condition of only using one radar through the MIMO radar system and beamforming technology;

[0133] (3) In the embodiments of the present invention, by improving the data processing method and designing the ocean wave observation point array, the ocean wave direction distribution in each frequency band can be accurately measured and the main wave direction can be determined in a simpler way, making the FMCW millimeter-wave MIMO radar likely to become a new type of efficient observation device in the field of wave direction observation in the future;

[0134] (4) Compared with the traditional wave direction inverse calculation method, the scheme proposed in the embodiments of the present invention has high economic value, higher feasibility, better equipment maintainability, and high measurement accuracy, and has a wide range of application scenarios.

[0135] Secondly, a device for inverse calculation of ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar proposed in the embodiments of the present invention is described with reference to the accompanying drawings.

[0136] Figure 9 is a block schematic diagram of a device for inverse calculation of ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar according to the embodiments of the present invention.

[0137] As Figure 9As shown in the figure, the device 90 for inverting the ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar includes: a parameter setting module 901, an observation module 902, a preprocessing module 903, a first calculation module 904, and a second calculation module 905.

[0138] Among them, the parameter setting module 901 is used to determine the required radar ranging resolution and ranging range, and set the waveform parameters of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar according to the radar ranging resolution and ranging range. The observation module 902 is used to place the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters on the observation sea surface according to the preset placement requirements to obtain radar echo data. The preprocessing module 903 is used to preprocess the radar echo data to obtain the power spectrum of the radar echo data. The first calculation module 904 is used to process the power spectrum of the radar echo data by using beamforming technology to obtain the wave height time series of the sea surface observation points in the required direction, and calculate the ocean wave cross-spectrum of the observation area according to the wave height time series of the sea surface observation points in the required direction. The second calculation module 905 is used to calculate the ocean wave direction spectrum according to the ocean wave cross-spectrum of the observation area and the preset spatial arrangement of the observation point array, where the ocean wave direction spectrum includes the direction distribution spectrum of the low-frequency band of the ocean waves in the observation area and the main wave direction of the observation area.

[0139] In some embodiments, when the ranging range is 1 - 25 m and the wave height accuracy is 5 cm, the frequency modulation slope of the frequency-modulated continuous-wave signal of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar is set to 60 MHz / μs, the duration of the frequency-modulated continuous-wave signal is 60 μs, the sampling frequency of the analog-to-digital converter is 10 MSPS, one frame of results consists of 16 cycles, 12 transmitting antennas work in sequence in each cycle, and the frame period is 100 ms.

[0140] In some embodiments, the preset placement requirements are: install the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters in a wide sea area, and make the RF board of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters parallel to the sea surface so that the electromagnetic wave irradiates the sea surface vertically; the distance between different sea surface observation points is determined according to the placement height and observation angle of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the set waveform parameters, and the distance between any two observation points should be less than 1 / 2 of the observation wavelength.

[0141] In some embodiments, the preprocessing module 903 includes:

[0142] A calibration unit, which is used to multiply the radar echo data by a calibration matrix to obtain calibrated radar echo data;

[0143] A first transformation unit, which is used to perform a fast Fourier transform on the calibrated radar echo data to obtain the power spectrum of the radar echo data.

[0144] In some embodiments, the first calculation module 904 includes:

[0145] A first extraction unit, configured to extract the maximum value point and its index value in the power spectrum of the radar echo data, and multiply the index value by the radar ranging resolution to obtain the vertical distance between the radar and the sea surface at each observation moment;

[0146] A uniform calculation unit, configured to perform a mean calculation on the vertical distance between the radar and the sea surface at each observation moment to obtain the standard distance between the radar and the sea level;

[0147] A construction unit, configured to construct a three-dimensional rectangular coordinate system with the standard distance between the radar directly below the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar after setting the waveform parameters and the sea level as the origin;

[0148] A first difference unit, configured to, based on the three-dimensional rectangular coordinate system, subtract the standard distance between the radar and the sea level from the vertical distance between the radar and the sea surface at each observation moment to obtain the wave height time series of the radar vertical point;

[0149] A second difference unit, configured to use beamforming technology to enhance the signal intensity in the power spectrum of the radar echo data, obtain the power spectrum after beamforming, and subtract the power spectrum after beamforming from the power spectrum of the radar echo data to obtain the difference power spectrum;

[0150] A second extraction unit, configured to extract the maximum value point and its index value in the difference power spectrum, and multiply the index value by the radar ranging resolution to obtain the slant range between the radar and the sea surface observation point in the required direction at each observation moment;

[0151] A projection unit, configured to project the slant range between the radar and the sea surface observation point in the required direction at each observation moment onto the z-axis in the three-dimensional rectangular coordinate system to obtain the vertical distance between the radar and the sea surface observation point in the required direction at each observation moment;

[0152] A third difference unit, configured to subtract the standard distance between the radar and the sea level from the vertical distance between the radar and the sea surface observation point in the required direction at each observation moment to obtain the wave height time series of the sea surface observation point in the required direction; [[ID=X]] [[ID=Y]]

[0153] A plotting unit, configured to respectively plot the vertical point wave height time series diagram of the wave height time series of the radar vertical point and the wave height time series diagram in the required direction of the wave height time series of the sea surface observation point in the required direction, and perform median filtering on the outliers in the vertical point wave height time series diagram and the wave height time series diagram in the required direction to obtain the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction;

[0154] A second transformation unit, configured to perform fast Fourier transform on the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction to obtain a fast Fourier transform result;

[0155] A first calculation unit, configured to find the frequency band with the highest ocean wave energy distribution at each observation point in the fast Fourier transform result, and sequentially conjugate multiply the Fourier transform results of every two points in order to obtain the ocean wave cross spectrum of the observation area.

[0156] In some embodiments, the second calculation module 905 includes:

[0157] A second calculation unit, configured to calculate the directional distribution spectrum of the low-frequency band of ocean waves in the observation area based on the Bayesian direction spectrum estimation method according to the ocean wave cross spectrum of the observation area and the preset spatial arrangement of the observation point array;

[0158] An analysis unit, configured to analyze the wave direction distribution of each frequency band of ocean waves in the ocean wave cross spectrum of the observation area to output an ocean wave main direction-frequency diagram;

[0159] A determination unit, configured to determine the main wave direction of the observation area in the ocean wave main direction-frequency diagram according to the direction distribution of the frequency band with the highest ocean wave energy distribution at each observation point.

[0160] It should be noted that the foregoing explanation of the embodiments of the ocean wave direction spectrum inversion method based on the FMCW millimeter wave MIMO radar also applies to the ocean wave direction spectrum inversion device based on the FMCW millimeter wave MIMO radar of this embodiment, and will not be elaborated here.

[0161] The ocean wave direction spectrum inversion device based on the FMCW millimeter wave MIMO radar proposed according to the embodiments of the present invention has the following beneficial effects:

[0162] (1) Solve the problems faced by traditional ocean wave direction measurement, such as high equipment cost, difficult deployment, and inconvenient maintenance. The equipment is simple to install, not affected by weather and ocean conditions, and can realize all-day and all-weather ocean wave observation;

[0163] (2) Compared with other millimeter wave radar inversion ocean wave reverse spectrum schemes, the present invention can achieve high-precision measurement of ocean wave direction under the condition of only using one radar through the MIMO radar system and beamforming technology;

[0164] (3) The embodiments of the present invention can accurately measure the ocean wave direction distribution of each frequency band and determine the main wave direction in a simpler manner by improving the data processing method and designing the ocean wave observation point array, making the FMCW millimeter wave MIMO radar likely to become a new type of efficient observation device in the field of wave direction observation in the future;

[0165] (4) Compared with traditional wave direction inversion methods, the solution proposed in the embodiments of the present invention has high economic value, higher executability, better equipment maintainability and high measurement accuracy, and has a wide range of application scenarios.

[0166] Figure 10 It is a schematic structural diagram of the electronic device provided by the embodiments of the present invention. The electronic device may include:

[0167] A memory 1001, a processor 1002, and a computer program stored on the memory 1001 and executable on the processor 1002.

[0168] When the processor 1002 executes the program, it implements the method for inverting the ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar provided in the above embodiments.

[0169] Furthermore, the electronic device further includes:

[0170] A communication interface 1003 for communication between the memory 1001 and the processor 1002.

[0171] The memory 1001 is used to store a computer program executable on the processor 1002.

[0172] The memory 1001 may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk memory.

[0173] If the memory 1001, the processor 1002, and the communication interface 1003 are implemented independently, the communication interface 1003, the memory 1001, and the processor 1002 can be interconnected through a bus and communicate with each other. The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 10 only a thick line is shown in the figure, but it does not mean that there is only one bus or one type of bus.

[0174] Optionally, in a specific implementation, if the memory 1001, the processor 1002, and the communication interface 1003 are integrated on a chip, the memory 1001, the processor 1002, and the communication interface 1003 can communicate with each other through an internal interface.

[0175] The processor 1002 may be a Central Processing Unit (CPU), or an Application Specific Integrated Circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0176] The embodiments of the present invention also provide a computer program product. When the computer program / instructions are executed by a processor, the method for inverting the ocean wave directional spectrum based on the FMCW millimeter-wave MIMO radar as described above is implemented.

[0177] The embodiments of the present invention also provide a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the method for inverting the ocean wave directional spectrum based on the FMCW millimeter-wave MIMO radar as described above is implemented.

[0178] In the description of this specification, the descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0179] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0180] Any process or method description shown in the flowchart or described in other ways herein may be understood as representing a module, segment, or part of code including one or N executable instructions for implementing a customized logic function or process. The scope of the preferred embodiments of the present invention includes additional implementations, where the functions may be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the art of the embodiments of the present invention.

[0181] The logic and / or steps represented in the flowchart or otherwise described herein can, for example, be considered as a definable sequence list of executable instructions for implementing logical functions, which can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or in conjunction with these instruction execution systems, apparatuses, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium include the following: an electrical connection portion (electronic device) having one or N wirings, a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, since the program can be obtained electronically by optically scanning the paper or other media, followed by editing, interpretation, or otherwise processing as appropriate, and then stored in a computer memory.

[0182] It should be understood that the various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, the N steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented using hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having suitable combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), and the like.

[0183] Those of ordinary skill in the art of this technology can understand that all or part of the steps carried by the method of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0184] In addition, in each embodiment of the present invention, each functional unit may be integrated into a processing module, may exist separately physically for each unit, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0185] The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disc, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for retrieving the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar, characterized in that It includes the following steps: Determine the required radar ranging resolution and ranging range, and set the waveform parameters of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar according to the radar ranging resolution and the ranging range; Place the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set according to the preset placement requirements on the observed sea surface to obtain radar echo data; Preprocess the radar echo data to obtain the power spectrum of the radar echo data; Use beamforming technology to process the power spectrum of the radar echo data to obtain the wave height time series of the sea surface observation points in the required direction, and calculate the wave cross-spectrum of the observation area according to the wave height time series of the sea surface observation points in the required direction; Calculate the wave direction spectrum according to the wave cross-spectrum of the observation area and the preset spatial arrangement of the observation point array, where the wave direction spectrum includes the direction distribution spectrum of the low-frequency band of the sea waves in the observation area and the main wave direction of the observation area.

2. The method for inverting the ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar according to claim 1, wherein When the ranging range is 1 - 25m and the wave height accuracy is 5cm, set the frequency modulation slope of the frequency-modulated continuous-wave signal of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar to 60MHz / us, the duration of the frequency-modulated continuous-wave signal to 60us, the sampling frequency of the analog-to-digital converter to 10MSPS, one frame of results consists of 16 cycles, 12 transmitting antennas work in sequence in each cycle, and the frame period is 100ms.

3. The method for inverting the ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar according to claim 1, wherein The preset placement requirements are: Install the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set to a wide sea area, and make the RF board of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set parallel to the sea surface so that the electromagnetic wave irradiates the sea surface vertically; The distance between different sea surface observation points is determined according to the placement height and observation angle of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set, and the distance between any two observation points should be less than 1 / 2 of the observation wavelength.

4. The method for inverting the ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar according to claim 1, wherein The preprocessing of the radar echo data to obtain the power spectrum of the radar echo data includes: Multiply the radar echo data by a calibration matrix to obtain the calibrated radar echo data; Perform a fast Fourier transform on the calibrated radar echo data to obtain the power spectrum of the radar echo data.

5. The method for inverting the ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar according to claim 1, wherein The use of beamforming technology to process the power spectrum of the radar echo data to obtain the wave height time series of the sea surface observation points in the required direction, and calculate the wave cross-spectrum of the observation area according to the wave height time series of the sea surface observation points in the required direction includes: Extract the maximum value points and their index values in the power spectrum of the radar echo data, and multiply the index values by the radar ranging resolution to obtain the vertical distance between the radar and the sea surface at each observation moment; Perform a mean calculation on the vertical distance between the radar and the sea surface at each observation moment to obtain the standard distance between the radar and the sea level; Construct a three-dimensional rectangular coordinate system with the standard distance between the radar directly below the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set and the sea level as the origin; Based on the three-dimensional rectangular coordinate system, the standard distance between the radar and the sea level is subtracted from the vertical distance between the radar and the sea surface at each observation moment to obtain the wave height time series of the radar vertical point; The beamforming technique is used to enhance the signal intensity in the power spectrum of the radar echo data to obtain the power spectrum after beamforming, and the power spectrum after beamforming is subtracted from the power spectrum of the radar echo data to obtain the difference power spectrum; The maximum value point and its index value in the difference power spectrum are extracted, and the index value is multiplied by the radar ranging resolution to obtain the slant range between the radar and the sea surface observation point in the required direction at each observation moment; The slant range between the radar and the sea surface observation point in the required direction at each observation moment is projected onto the z-axis in the three-dimensional rectangular coordinate system to obtain the vertical distance between the radar and the sea surface observation point in the required direction at each observation moment; The standard distance between the radar and the sea level is subtracted from the vertical distance between the radar and the sea surface observation point in the required direction at each observation moment to obtain the wave height time series of the sea surface observation point in the required direction; The vertical point wave height time series diagram of the wave height time series of the radar vertical point and the wave height time series diagram in the required direction of the wave height time series of the sea surface observation point in the required direction are respectively plotted, and the outliers in the vertical point wave height time series diagram and the wave height time series diagram in the required direction are median filtered to obtain the filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction; The filtered vertical point wave height time series diagram and the filtered wave height time series diagram in the required direction are subjected to fast Fourier transform to obtain the fast Fourier transform result; In the fast Fourier transform result, the frequency band with the highest sea wave energy distribution at each observation point is found, and the Fourier transform results of every two points are sequentially conjugate multiplied in order to obtain the cross spectrum of the sea waves in the observation area.

6. The method for inverting the ocean wave direction spectrum based on the FMCW millimeter-wave MIMO radar according to claim 1, wherein The calculation of the sea wave direction spectrum according to the cross spectrum of the sea waves in the observation area and the spatial arrangement of the preset observation point array includes: Based on the Bayesian direction spectrum estimation method, the direction distribution spectrum of the low-frequency band of the sea waves in the observation area is calculated according to the cross spectrum of the sea waves in the observation area and the spatial arrangement of the preset observation point array; Analyze the wave direction distribution of each frequency band of the sea waves in the cross spectrum of the sea waves in the observation area to output the sea wave main direction-frequency diagram; Determine the main wave direction of the observation area in the sea wave main direction-frequency diagram according to the direction distribution of the frequency band with the highest sea wave energy distribution at each observation point.

7. A device for retrieving the ocean wave direction spectrum based on an FMCW millimeter-wave MIMO radar, characterized in that, It includes: A parameter setting module for determining the required radar ranging resolution and ranging range, and setting the waveform parameters of the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar according to the radar ranging resolution and the ranging range; An observation module for placing the frequency-modulated continuous-wave millimeter-wave multiple-input multiple-output radar with the waveform parameters set according to the preset placement requirements on the observation sea surface to measure the radar echo data; A preprocessing module for preprocessing the radar echo data to obtain the power spectrum of the radar echo data; A first calculation module, configured to process the power spectrum of the radar echo data by using beamforming technology to obtain a wave height time series of a sea surface observation point in a required direction, and calculate a cross spectrum of sea waves in an observation area according to the wave height time series of the sea surface observation point in the required direction; A second calculation module, configured to calculate a sea wave direction spectrum according to the cross spectrum of sea waves in the observation area and a preset spatial arrangement of an observation point array, wherein the sea wave direction spectrum includes a direction distribution spectrum of a low-frequency band of sea waves in the observation area and a main wave direction of the observation area.

8. An electronic device, characterized in that, Comprising: A memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to implement the method for inverting a sea wave direction spectrum based on an FMCW millimeter-wave MIMO radar according to any one of claims 1-6.

9. A computer program product, characterized in that, When the computer program / instructions are executed by the processor, the method for inverting a sea wave direction spectrum based on an FMCW millimeter-wave MIMO radar according to any one of claims 1-6 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, The program is executed by the processor to be used for implementing the method for inverting a sea wave direction spectrum based on an FMCW millimeter-wave MIMO radar according to any one of claims 1-6.

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