A sea clutter data conversion method from a stationary platform to a moving platform

Abstract

The application discloses a sea clutter data conversion method from a static platform to a moving platform, and relates to the technical field of radar signal processing. F The sea clutter data conversion method from the static platform to the moving platform does not depend on a model to generate the measured data of the moving platform sea clutter, and can avoid errors caused by the model; and can simultaneously generate the amplitude distribution model and the spectrum model and the corresponding sea clutter simulation data of the measured sea clutter data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar signal processing, and particularly relates to a sea clutter data conversion method from a static platform to a moving platform. BACKGROUND

[0002] Radar detection capability evaluation and target detection and identification method research under complex marine environment rely on radar sea clutter detection measured data. At present, most of the radar sea exploration tests carried out are based on shore-based radar, and the development of dynamic platform test is high in cost and difficult, so it is difficult to obtain dynamic platform sea clutter data based on test. However, obtaining sea clutter measured data of various ground angles and various sea conditions under the flight state of the dynamic platform plays an important role in radar performance analysis and detection capability improvement, so the conversion of sea clutter measured data from the static platform to the dynamic platform sea clutter data has important significance. The present scheme provides a sea clutter data conversion method from a static platform to a moving platform. SUMMARY

[0003] The present application provides a sea clutter data conversion method from a static platform to a moving platform to solve the problems in the background art.

[0004] To solve the above technical problems, the technical scheme adopted by the present application is:

[0005] A sea clutter data conversion method from a static platform to a moving platform, comprising the following steps:

[0006] Step 1: radar and environmental information input, wherein the three-dimensional coordinates of the radar are , the speed is , the wavelength is , the three-dimensional coordinates of the target are , and the ground angle is ;

[0007] Step 2: calculate the spectrum center and spectrum spread from the geometric position relationship:

[0008] Spectrum center: ;

[0009] ;

[0010] Spectrum spread: ,

[0011] ;

[0012] , wherein represents the main lobe beam azimuth dimension width of the moving platform radar, represents the height of the moving platform radar, represents the distance between the radar and the target, and the calculation formula is:

[0013] ;

[0014] Step 3: Based on long-term sea clutter data acquired from a static platform, construct a sea clutter harmonic spectrum model and use a nonlinear optimization algorithm to calculate the parameters of the harmonic spectrum model;

[0015] Step 4: Substitute the spectral center and spectral broadening parameters obtained in Step 2 into the harmonic spectrum model to obtain the clutter spectrum shape of the high-speed platform sea clutter data. F ';

[0016] Step 5: Generate the motion platform through calculation or simulation. N Length sea clutter data.

[0017] Preferably, step one includes the following:

[0018] A1: The conversion process targets each distance unit under given ground angle and given sea conditions;

[0019] A2: The geometrical relationship between the platform and the sea surface during the static platform data acquisition experiment;

[0020] A3: Long time obtained from a static platform ( NL Sea clutter data, among which, N This is the number of pulses required for the radar to operate normally. L It is required when estimating the average spectrum of clutter. L Pulse count.

[0021] Preferably, in step two:

[0022] target along Flying in the positive direction of the axis, with a speed of The radar beam was pointed towards the sea surface ahead along the flight path. This refers to range resolution. Considering that radars on moving platforms typically have high range resolution, therefore... Generally, the Doppler difference between the leading and trailing edges of a distance cell and the center of the distance cell can be ignored when the distance is in the meter range, relative to a distance of several kilometers.

[0023] Preferably, since the area of ​​the motion platform is small, the azimuth beam is usually wide, and the Doppler difference along the left and right azimuth edges of the beam cannot be ignored; The pitch dimension width of the radar beam main lobe of the moving platform is represented. Since the pitch dimension beam is relatively wide, different lines connecting the sea surface and the moving platform within the beam correspond to different ground rubbing angles, and thus correspond to different range units. Since the pitch and azimuth dimensions of the moving platform radar main lobe beam are relatively wide, most of the radiated energy is concentrated in the antenna main lobe. Therefore, sea clutter entering from the antenna beam sidelobes is ignored in the simulation.

[0024] Preferably, in the step three:

[0025] The single-component spectrum model represented by the Gaussian model has been deeply analyzed in most literatures, and the advantage of such model lies in simple structure and convenient parameter estimation; however, the main problem lies in that the influence of different types of scattering components on the spectrum is not fully considered, and the modeling accuracy of the measured Doppler spectrum is low; in comparison, the Lee model and the Walker model have higher modeling accuracy due to the more perfect factors considered in the mechanism level; since the Lee model is complex in form, it is difficult for people to understand and accept, and is rarely applied in subsequent research; in fact, the Walker model has high modeling accuracy near the Doppler center frequency, but has large modeling error in the tail of the Doppler spectrum, and the modeling result shows this conclusion; obviously, when the frequency value deviates from the Doppler center frequency in the positive and negative directions, the model deviates from the Doppler spectrum estimation value, and cannot reflect the properties of the sea clutter spectrum and the noise spectrum in the transition region; for the sea clutter spectrum model of the static platform, the harmonic model of the spectrum is introduced, and the parameter estimation of the model adopts the nonlinear optimization algorithm; it can be seen that the harmonic model can obviously improve the modeling accuracy, and is better than the accuracy of the Walker model.

[0026] Preferably, in the step four: the spectrum model estimated by the sea clutter data of the static platform is denoted as F0, and the function relationship between the spectrum model parameters and the spectrum center and the spectrum spread parameters, the spectrum center and the spectrum spread parameters obtained by combining the geometric position relationship and the other parameters of the radar are used to give the clutter spectrum shape F' of the sea clutter data of the moving platform.

[0027] Due to the adoption of the above technical scheme, the present application has the following technical progress compared with the prior art:

[0028] 1. The present application provides a sea clutter data conversion method from a static platform to a moving platform, which does not depend on the model to generate the measured data of the moving platform, and can avoid the error caused by the model.

[0029] 2. The present application provides a sea clutter data conversion method from a static platform to a moving platform, which can simultaneously generate the amplitude distribution model and the spectrum model, and the sea clutter simulation data corresponding to the measured sea clutter data. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The flowchart of the present application;

[0031] Figure 2 The geometric position diagram of the moving platform radar detecting the sea surface of the present application;

[0032] Figure 3Fig. 1 is a schematic diagram of modeling results of a Walker model of the present application; in the figure: (a) is a #1 data (HH polarization) graph; (b) is a #1 data (VV polarization) graph;

[0033] Figure 4 Fig. 2 is a schematic diagram of modeling results of a harmonic model of the present application; in the figure: (a) is a #1 data (HH polarization) graph; (b) is a #1 data (VV polarization) graph. DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific embodiments.

[0035] As shown in Figures 1-4 , a sea clutter data conversion method from a stationary platform to a moving platform, comprising the following steps:

[0036] Step 1: radar and environmental information input, wherein the three-dimensional coordinates of the radar are , the speed is , the wavelength is , the three-dimensional coordinates of the target are , and the grazing angle is ;

[0037] A1: The conversion process is for: each distance unit under the given grazing angle and the given sea condition;

[0038] A2: Geometric position relationship between the platform and the sea surface in the stationary platform data acquisition test;

[0039] A3: Long-time ( NL ) sea clutter data obtained by the stationary platform, wherein N is the number of pulses required for the normal operation of the radar, L is the number of pulses required for the estimation of the average spectrum of the clutter L times

[0040] Step 2: Calculate the spectrum center and the spectrum spread from the geometric position relationship:

[0041] Spectrum center: ;

[0042] ;

[0043] Spectrum spread: ,

[0044] ;

[0045] represents the main lobe beam azimuth dimension width of the moving platform radar, represents the height of the moving platform radar, The distance between the radar and the target is expressed by the following formula:

[0046] ;

[0047] target along Flying in the positive direction of the axis, with a speed of The radar beam was pointed towards the sea surface ahead along the flight path. This refers to range resolution. Considering that radars on moving platforms typically have high range resolution, therefore... Generally, the Doppler difference between the leading and trailing edges of a distance cell and the center of the distance cell can be ignored when the distance is in the meter range, relative to a distance of several kilometers.

[0048] Because the area of ​​the motion platform is small, the azimuth beam is usually wide, and the Doppler difference along the left and right azimuth edges of the beam cannot be ignored. The pitch dimension width of the radar beam main lobe of the moving platform is represented. Since the pitch dimension beam is relatively wide, different lines connecting the sea surface and the moving platform within the beam correspond to different ground rubbing angles, and thus correspond to different range units. Since the pitch and azimuth dimensions of the moving platform radar main lobe beam are relatively wide, most of the radiated energy is concentrated in the antenna main lobe. Therefore, sea clutter entering from the antenna beam sidelobes is ignored in the simulation.

[0049] Step 3: Based on long-term sea clutter data acquired from a static platform, construct a sea clutter harmonic spectrum model and use a nonlinear optimization algorithm to calculate the parameters of the harmonic spectrum model;

[0050] Single-component spectral models, represented by the Gaussian model, have been extensively analyzed in most literatures. These models are advantageous due to their simple structure and convenient parameter estimation; however, their main problem lies in not fully considering the influence of different types of scattering components from the sea surface on the spectrum, and their low modeling accuracy for measured Doppler spectra. In contrast, the Lee and Walker models, due to their more comprehensive consideration of mechanistic factors, achieve higher modeling accuracy. However, the Lee model's complex form makes it difficult to understand and accept, leading to its limited application in subsequent research. In fact, the Walker model exhibits high modeling accuracy near the Doppler center frequency, but its modeling error is larger at the tail of the Doppler spectrum, as demonstrated by the modeling results. Clearly, as the frequency value moves away from the Doppler center frequency in both positive and negative directions, the model gradually deviates from the estimated Doppler spectrum, failing to reflect the properties of the sea clutter spectrum and noise spectrum in the transition region. For the sea clutter data spectral model under a stationary platform, a harmonic model is introduced, and the model's parameters are estimated using a nonlinear optimization algorithm. It can be seen that using the harmonic model significantly improves the modeling accuracy, surpassing that of the Walker model.

[0051] By analyzing the modeling results of the two models under different polarization modes, it is found that the Walker model has high modeling accuracy only near the spectral peak, and poor modeling effect in the tail of the spectrum; the harmonic model of a specific order is obviously superior to the Walker model in modeling accuracy, and can be used to model the Doppler spectrum in the field of sea clutter modeling simulation and signal detection algorithm design.

[0052] Step four: the spectrum center and spectrum broadening parameters calculated in step two are brought into the harmonic spectrum model to obtain the sea clutter spectrum shape of the high-speed platform sea clutter data F ’;

[0053] The spectrum model estimated by the sea clutter data obtained by the stationary platform is denoted as F0, and the function relationship between the spectrum model parameters and the spectrum center and spectrum broadening parameters is obtained. Combined with the spectrum center and spectrum broadening parameters obtained by the geometric position relationship and other parameters of the radar, the sea clutter spectrum shape F' of the moving platform is given.

[0054] Step five: generate the sea clutter data of the moving platform N length by calculation or simulation;

[0055] Then, according to the principle of energy conservation, the area under the sea clutter spectrum of the stationary platform is equal to the area under the newly obtained sea clutter spectrum, and the sea clutter spectrum of the moving platform data is obtained, denoted as F1;

[0056] The subsequent sea clutter data of the moving platform will be generated in two schemes;

[0057] Scheme 1: calculate the sea clutter data of the moving platform

[0058] First, solve the following formula to obtain the mathematical mapping relationship H between F0 and F1:

[0059] ;

[0060] Wherein, represents convolution;

[0061] Then, the inverse Fourier transform of H is obtained, and its time domain form h is obtained.

[0062] Finally, the sea clutter data obtained by the stationary platform is multiplied by h to generate the sea clutter data of the moving platform.

[0063] Scheme 2: simulate the sea clutter data of the moving platform

[0064] First, estimate the amplitude distribution type and its parameters of the measured data by using the long-time (NL) sea clutter data obtained by the stationary platform;

[0065] Then, the independent and identically distributed sea clutter data is generated by simulation using the amplitude distribution characteristics;

[0066] Next, the correlation function is solved by Fourier inverse transform using the sea clutter spectrum model of the moving platform sea clutter data obtained in step three;

[0067] Finally, the correlation function is applied to the independent and identically distributed sea clutter data generated by simulation to generate the sea clutter data corresponding to the moving platform with the same amplitude distribution and clutter spectrum.

[0068] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for sea clutter data translation from a stationary platform to a moving platform, the method comprising: Comprising the following steps: ​ Step one: radar and environmental information input, A1: data conversion process for: given the angle of the ground, given sea conditions for each distance unit; A2: in the static platform data acquisition test, the geometric position relationship between the platform and the sea surface; A3: Long time acquisition with stationary platform NL Sea clutter data, where, N is the number of pulses required for normal radar operation, L is the number of pulses required for estimating the average spectrum of the clutter L is the number of pulses required for estimating the average spectrum of the clutter wherein the three-dimensional coordinates of the radar are , the radar velocity is , the wavelength is , the three-dimensional coordinates of the target are , and the ground angle is : Step two: calculate the spectral center and spectral broadening from the geometric position relationship: ； denotes the mainlobe beam azimuthal width of the moving platform radar, denotes the height of the moving platform radar, denotes the distance of the radar to the target, and the calculation formula is: ； Step three: based on the long time sea clutter data obtained by the static platform, the sea clutter harmonic spectrum model is constructed, and the parameters of the harmonic spectrum model are calculated by using the nonlinear optimization algorithm; Step four: the spectrum center and spectrum spread parameter calculated in step two are brought into the harmonic spectrum model to obtain the spectrum shape of the sea clutter data of the high-speed platform F ’; Step five: generate the length sea clutter data by calculation or simulation N of the motion platform.

2. The method for sea clutter data translation from static platform to moving platform according to claim 1, wherein: In the step four: the spectrum model F0 estimated by the sea clutter data obtained by the static platform, and the function relationship between the spectrum model parameters and the spectrum center and the spectrum broadening parameters, combined with the spectrum center and the spectrum broadening parameters obtained by the geometric position relationship and other parameters of the radar, give the shape of the sea clutter data of the moving platform F'.

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