Sea clutter data conversion method from static platform to moving platform

Abstract

The invention 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, and the method comprises the following steps: 1, inputting radar and environment information; 2, calculating a spectrum center and spectrum broadening according to the geometric position relation; 3, constructing a sea clutter harmonic spectrum model based on long-time sea clutter data acquired by the static platform, and calculating parameters of the harmonic spectrum model by adopting a nonlinear optimization algorithm; and 4, substituting the spectrum center and the spectrum broadening parameter obtained by calculation in the step 2 into a harmonic spectrum model to obtain a clutter spectrum shape F'of the sea clutter data of the high-speed platform. According to the sea clutter data conversion method from the static platform to the moving platform, sea clutter measured data of the moving platform are generated without depending on a model, and errors caused by the model can be avoided; sea clutter simulation data in which an amplitude distribution model and a spectrum model correspond to actually measured sea clutter data at the same time can be generated at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of radar signal processing, and in particular to a method for converting sea clutter data from a stationary platform to a moving platform. Background Art

[0002] The research on radar detection capability evaluation and target detection and recognition methods in complex marine environments relies on the measured data of radar sea clutter detection. Most of the radar sea detection tests that have been carried out are based on shore-based radars. The dynamic platform test is costly and difficult to carry out, so it is difficult to obtain the sea clutter data of the dynamic platform based on the test. However, obtaining the measured sea clutter data under various ground-grabbing 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. Therefore, the conversion of the measured sea clutter data obtained from the stationary platform to the sea clutter data of the dynamic platform is of great significance. This scheme proposes a method for converting sea clutter data from a stationary platform to a moving platform. Summary of the invention

[0003] The present invention provides a method for converting sea clutter data from a stationary platform to a moving platform to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for converting sea clutter data from a stationary platform to a moving platform comprises the following steps: Step 1: Input radar and environment information, where the three-dimensional coordinates of the radar are , the speed is , the wavelength is , the three-dimensional coordinates of the target are , the rubbing angle is ; Step 2: Calculate the spectrum center and spectrum broadening based on the geometric position relationship: Spectrum Center: ; ; Spectral broadening: , ; represents the azimuth width of the main lobe beam of the moving platform radar, Indicates the radar height of the moving platform, Indicates the distance between the radar and the target, and the calculation formula is: ; Step 3: Based on the long-term sea clutter data obtained by the stationary platform, a sea clutter harmonic spectrum model is constructed, and the parameters of the harmonic spectrum model are calculated using a nonlinear optimization algorithm; Step 4: Substitute the spectrum center and spectrum broadening parameters calculated in step 2 into the harmonic spectrum model to obtain the clutter spectrum shape of the high-speed platform sea clutter data F '; Step 5: Generate the motion platform through calculation or simulation N Length sea clutter data.

[0005] Preferably, the step 1 includes the following: A1: The conversion process is for each distance unit under given ground-grazing angle and given sea conditions; A2: Geometric position relationship between the platform and the sea surface during the stationary platform data acquisition test; A3: The long time obtained by the stationary platform ( NL ) sea clutter data, where N is the number of pulses required for the radar to work properly. L is needed to estimate the average spectrum of clutter L times the number of pulses.

[0006] Preferably, in the step 2: Target along The axis is flying in the positive direction, and the speed is ; The radar beam points to the sea surface ahead along the flight direction; Indicates the distance resolution. Considering that the radar of a moving platform usually has a higher distance resolution, Generally, at the meter level, relative to distances of several kilometers, the Doppler differences between the front and rear edges of the range cell and the center of the range cell can be ignored.

[0007] Preferably, since the area of ​​the moving platform is small, the azimuth beam is usually wide, and the Doppler difference between the left and right edges of the beam azimuth cannot be ignored; It represents the width of the pitch dimension of the main lobe of the radar moving platform. Since the pitch dimension beam is wide, different lines connecting the sea surface and the moving platform in the beam correspond to different ground grazing angles, and thus correspond to different distance units. Since the pitch and azimuth dimensions of the main lobe beam of the moving platform radar are relatively wide, most of the radiation energy is concentrated in the main lobe of the antenna. Therefore, the sea clutter entering the side lobe of the antenna beam is ignored in the simulation.

[0008] Preferably, in step three: Single component spectrum models represented by Gaussian models have been deeply analyzed in most literatures. The advantages of this type of model are simple structure and convenient parameter estimation. However, the main problem is that the influence of different types of scattering components on the sea surface on the spectrum is not fully considered, and the modeling accuracy of the Doppler spectrum of measured data is low. In contrast, the Lee model and Walker model have higher modeling accuracy because the factors considered at the mechanism level are more complete. Due to the complex form of the Lee model, it is difficult for people to understand and accept it, and it is rarely used in subsequent research. In fact, the Walker model has a high modeling accuracy near the Doppler center frequency, while the modeling error at the tail of the Doppler spectrum is large, and the modeling results shown in the figure show this conclusion. Obviously, when the frequency value moves away from the Doppler center frequency in both positive and negative directions, the model gradually 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 data spectrum model under the stationary platform, the harmonic model of the spectrum is introduced, and the parameter estimation of the model adopts a nonlinear optimization algorithm. It can be seen that the use of the harmonic model can significantly improve the modeling accuracy, and it is better than the accuracy of the Walker model.

[0009] Preferably, in the step 4: the spectral model "denoted as F0" estimated by using the sea clutter data obtained from the stationary platform, as well as the functional relationship between the spectral model parameters and the spectral center and spectral broadening parameters, are combined with the spectral center and spectral broadening parameters obtained from the geometric position relationship and other radar parameters to give the clutter spectrum shape F' of the sea clutter data of the moving platform.

[0010] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art: 1. The present invention provides a method for converting sea clutter data from a stationary platform to a moving platform, which does not rely on a model to generate actual sea clutter data of a moving platform, thus avoiding errors caused by the model; 2. The present invention provides a method for converting sea clutter data from a stationary platform to a moving platform, which can simultaneously generate an amplitude distribution model and a spectrum model and sea clutter simulation data corresponding to the measured sea clutter data. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a flow chart of the present invention; Figure 2 It is a schematic diagram of the geometric position of the sea surface detected by the mobile platform radar of the present invention; Figure 3 The figure is a schematic diagram of the modeling result of the Walker model of the present invention; in the figure: (a) is the #1 data (HH polarization) diagram; (b) is the #1 data (VV polarization) diagram; Figure 4Schematic diagram of the harmonic modeling results of the present invention; in the figure: (a) is the #1 data (HH polarization) diagram; (b) is the #1 data (VV polarization) diagram. DETAILED DESCRIPTION

[0012] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0013] like Figure 1-Figure 4 As shown, a method for converting sea clutter data from a stationary platform to a moving platform comprises the following steps: Step 1: Input radar and environment information, where the three-dimensional coordinates of the radar are , the speed is , the wavelength is , the three-dimensional coordinates of the target are , the rubbing angle is ; A1: The conversion process is for each distance unit under given ground-grazing angle and given sea conditions; A2: Geometric position relationship between the platform and the sea surface during the stationary platform data acquisition test; A3: The long time obtained by the stationary platform ( NL ) sea clutter data, where N is the number of pulses required for the radar to work properly. L is needed to estimate the average spectrum of clutter L Multiple pulse number Step 2: Calculate the spectrum center and spectrum broadening based on the geometric position relationship: Spectrum Center: ; ; Spectral broadening: , ; represents the azimuth width of the main lobe beam of the moving platform radar, Indicates the radar height of the moving platform, Indicates the distance between the radar and the target, and the calculation formula is: ; Target along The axis is flying in the positive direction, and the speed is ; The radar beam points to the sea surface ahead along the flight direction; Indicates the distance resolution. Considering that the radar of a moving platform usually has a higher distance resolution, Generally, at the meter level, relative to distances of several kilometers, the Doppler differences between the front and rear edges of the range cell and the center of the range cell can be ignored.

[0014] Since the area of ​​the moving platform is small, the azimuth beam is usually wide, and the Doppler difference between the left and right edges of the beam azimuth cannot be ignored; It represents the width of the pitch dimension of the main lobe of the radar moving platform. Since the pitch dimension beam is wide, different lines connecting the sea surface and the moving platform in the beam correspond to different ground grazing angles, and thus correspond to different distance units. Since the pitch and azimuth dimensions of the main lobe beam of the moving platform radar are relatively wide, most of the radiation energy is concentrated in the main lobe of the antenna. Therefore, the sea clutter entering the side lobe of the antenna beam is ignored in the simulation.

[0015] Step 3: Based on the long-term sea clutter data obtained by the stationary platform, a sea clutter harmonic spectrum model is constructed, and the parameters of the harmonic spectrum model are calculated using a nonlinear optimization algorithm; Single component spectrum models represented by Gaussian models have been deeply analyzed in most literatures. The advantages of this type of model are simple structure and convenient parameter estimation. However, the main problem is that the influence of different types of scattering components on the sea surface on the spectrum is not fully considered, and the modeling accuracy of the Doppler spectrum of measured data is low. In contrast, the Lee model and Walker model have higher modeling accuracy because the factors considered at the mechanism level are more complete. Due to the complex form of the Lee model, it is difficult for people to understand and accept it, and it is rarely used in subsequent studies. In fact, the Walker model has a high modeling accuracy near the Doppler center frequency, but the modeling error is large at the tail of the Doppler spectrum. The modeling results shown in the figure show this conclusion. Obviously, when the frequency value moves away from the Doppler center frequency in both positive and negative directions, the model gradually 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 data spectrum model under the stationary platform, the harmonic model of the spectrum is introduced, and the parameter estimation of the model adopts a nonlinear optimization algorithm. It can be seen that the use of the harmonic model can significantly improve the modeling accuracy, and it is better than the accuracy of the Walker model. Through comprehensive analysis of the modeling results of sea clutter spectra of the two models under different polarization modes, it can be seen that the Walker model has a higher modeling accuracy only near the spectrum peak, and the modeling effect is poor at the tail of the spectrum; the harmonic model of a specific order is significantly better than the Walker model in modeling accuracy. The harmonic model can be used to model the Doppler spectrum in the fields of sea clutter modeling and simulation and the design of signal detection algorithms.

[0016] Step 4: Substitute the spectrum center and spectrum broadening parameters calculated in step 2 into the harmonic spectrum model to obtain the clutter spectrum shape of the high-speed platform sea clutter data F '; The spectral model "denoted as F0" estimated by the sea clutter data obtained from the stationary platform, as well as the functional relationship between the spectral model parameters and the spectral center and spectral broadening parameters, combined with the spectral center and spectral broadening parameters obtained from the geometric position relationship and other radar parameters, give the clutter spectrum shape F' of the sea clutter data of the moving platform.

[0017] Step 5: Generate the motion platform through calculation or simulation N Length sea clutter data; Then, according to the principle of energy conservation, that is, the area under the sea clutter spectrum of the stationary platform is equal to the area under the newly obtained sea clutter spectrum, the clutter spectrum of the sea clutter data of the moving platform is obtained, which is recorded as F1; There will be two schemes to generate sea clutter data under the moving platform in the future; Solution 1: Calculate and generate sea clutter data under a moving platform First, solve the following equation to obtain the mathematical mapping relationship H between F0 and F1: ; in, represents convolution; Then, take the inverse Fourier transform of H to obtain its time domain form h; Finally, the sea clutter data acquired by the stationary platform is multiplied by h to generate the sea clutter data of the moving platform.

[0018] Solution 2: Simulate and generate sea clutter data for a moving platform Firstly, the amplitude distribution type and parameters of the measured data are estimated using the long-time (NL) sea clutter data acquired by a stationary platform; Then, using the amplitude distribution characteristics, independent and identically distributed sea clutter data are simulated and generated; Next, the clutter spectrum model of the sea clutter data of the moving platform obtained in step 3 is used to solve the correlation function through inverse Fourier transform; Finally, the correlation function is applied to the independent and identically distributed sea clutter data generated by simulation to generate sea clutter data corresponding to the moving platform with the same amplitude distribution and clutter spectrum.

[0019] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for converting sea clutter data from a stationary platform to a moving platform, characterized in that: The following steps are involved: Step 1: Input radar and environmental information. A1: The data conversion process is for each distance unit under given ground-grazing angle and given sea conditions; A2: Geometric position relationship between the platform and the sea surface during the stationary platform data acquisition test; A3: Long time acquisition on a stationary platform NL Sea clutter data, where N is the number of pulses required for the radar to work properly. L is needed to estimate the average spectrum of clutter L Multiple pulse number; The three-dimensional coordinates of the radar are , the speed is , the wavelength is , the three-dimensional coordinates of the target are , the rubbing angle is ; Step 2: Calculate the spectrum center and spectrum broadening based on the geometric position relationship: Spectrum Center: ; ； Spectral broadening: , ； represents the azimuth width of the main lobe beam of the moving platform radar, Indicates the radar height of the moving platform, Indicates the distance between the radar and the target, and the calculation formula is: ； Step 3: Based on the long-term sea clutter data obtained by the stationary platform, a sea clutter harmonic spectrum model is constructed, and the parameters of the harmonic spectrum model are calculated using a nonlinear optimization algorithm; Step 4: Substitute the spectrum center and spectrum broadening parameters calculated in step 2 into the harmonic spectrum model to obtain the clutter spectrum shape of the high-speed platform sea clutter data F '; Step 5: Generate the motion platform through calculation or simulation N Length sea clutter data.

2. A method for converting sea clutter data from a stationary platform to a moving platform according to claim 1, characterized in that: In the step 2: Target along The axis is flying in the positive direction, and the speed is ; The radar beam is directed toward the sea surface ahead along the flight direction; Indicates the distance resolution. Considering that the radar of a moving platform usually has a higher distance resolution, Generally, at the meter level, relative to distances of several kilometers, the Doppler differences between the front and rear edges of the range cell and the center of the range cell can be ignored.

3. A method for converting sea clutter data from a stationary platform to a moving platform according to claim 2, characterized in that: Since the area of ​​the moving platform is small, the azimuth beam is usually wide, and the Doppler difference between the left and right edges of the beam azimuth cannot be ignored; It represents the width of the pitch dimension of the main lobe of the radar moving platform. Since the pitch dimension beam is wide, different lines connecting the sea surface and the moving platform in the beam correspond to different ground grazing angles, and thus correspond to different distance units. Since the pitch and azimuth dimensions of the main lobe beam of the moving platform radar are relatively wide, most of the radiation energy is concentrated in the main lobe of the antenna. Therefore, the sea clutter entering the side lobe of the antenna beam is ignored in the simulation.

4. The method for converting sea clutter data from a stationary platform to a moving platform according to claim 1, characterized in that: In the step three: Single-component spectral models, represented by Gaussian models, have been deeply analyzed in most literatures. The advantages of this type of model are simple structure and convenient parameter estimation; However, the main problem is that the influence of different types of scattering components on the sea surface on the spectrum is not fully considered, and the modeling accuracy of the Doppler spectrum of the measured data is low. In contrast, the Lee model and the Walker model have higher modeling accuracy because the factors considered at the mechanism level are more complete. Due to the complex form of the Lee model, it is difficult for people to understand and accept it, and it is rarely used in subsequent research. In fact, the Walker model has a high modeling accuracy near the Doppler center frequency, while the modeling error at the tail of the Doppler spectrum is large, and the modeling results shown in the figure show this conclusion. Obviously, when the frequency value moves away from the Doppler center frequency in both positive and negative directions, the model gradually 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 data spectrum model under the stationary platform, the harmonic model of the spectrum is introduced, and the parameter estimation of the model adopts a nonlinear optimization algorithm. It can be seen that the use of the harmonic model can significantly improve the modeling accuracy, and it is better than the accuracy of the Walker model.

5. The method for converting sea clutter data from a stationary platform to a moving platform according to claim 1, characterized in that: In the step 4, the spectral model "denoted as F0" estimated by using the sea clutter data obtained from the stationary platform, as well as the functional relationship between the spectral model parameters and the spectral center and spectral broadening parameters, are combined with the spectral center and spectral broadening parameters obtained from the geometric position relationship and other radar parameters to give the clutter spectrum shape F' of the sea clutter data of the moving platform.

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