A high-power interference suppression method based on polarization domain oblique projection filtering

Abstract

The application discloses a high-power interference suppression method based on polarization domain oblique projection filtering, establishes a radar echo signal model, including a target signal model, an interference signal model and a noise signal model; the radar echo signal is pretreated to obtain a peak value and a bottom noise signal; based on the peak value and the bottom noise signal, maximum likelihood estimation values of target and interference signal polarization coherence matrices are solved respectively, converted into Stokes vectors, polarization parameters of the target and interference signals are solved; then, an oblique projection matrix is constructed to perform polarization oblique projection filtering processing on the radar echo signal. The maximum likelihood estimation values of the target and interference signal polarization coherence matrices are solved, the polarization parameters of the target and interference signals are obtained, the polarization domain oblique projection matrix is constructed to modify a traditional polarization filtering method, the radar echo signal is subjected to polarization oblique projection filtering, so that under the condition that the polarization parameters of the target and interference are not orthogonal, high-power interference can be effectively suppressed and the energy loss of the target signal can be reduced.

Description

Technical Field

[0001] This invention belongs to the technical field of radar anti-jamming and relates to a high-power interference suppression method based on polarization domain oblique projection filtering. Background Technology

[0002] The essence of radar anti-jamming technology is to utilize the characteristic differences between jamming and target signals to suppress jamming signals while preserving or enhancing target signals. In modern electronic warfare, radars face a wide variety of complex jamming types. Among them, high-power suppression jamming involves transmitting noise signals or other specific signals to suppress target signals, making it impossible for radar to accurately detect targets. With the continuous development of high-power suppression jamming technology, the performance of conventional time, frequency, and spatial jamming suppression methods can no longer meet practical requirements.

[0003] Polarimetric domain characteristics are vector features that can quantitatively describe radar electromagnetic waves. Existing polarimetric filtering methods, based on the difference in polarimetric domain characteristics between target and interference signals, can effectively suppress high-power interference by orthogonally receiving the interference signal. However, in practical applications, the polarimetric parameters of the target and interference are usually non-orthogonal. Therefore, existing polarimetric filtering methods face the problem of target signal energy loss while suppressing interference. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a high-power interference suppression method based on polarization domain oblique projection filtering, which effectively solves the problems in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-power interference suppression method based on polarization domain oblique projection filtering includes:

[0007] S1. Establish a radar echo signal model, including a target signal model, an interference signal model, and a noise signal model;

[0008] S2. Preprocess the radar echo signal to obtain the peak signal and the noise floor signal;

[0009] S3. Based on the peak signal, solve for the maximum likelihood estimate of the polarization coherence matrix of the target signal, and after converting it into a Stokes vector, solve for the polarization parameters of the target signal.

[0010] S4. Based on the noise floor signal, solve for the maximum likelihood estimate of the polarization coherence matrix of the interference signal, and convert it into a Stokes vector to solve for the polarization parameters of the interference signal.

[0011] S5. Based on the polarization parameters of the target signal and the interference signal in S4, construct the oblique projection matrix and perform polarization oblique projection filtering on the radar echo signal.

[0012] Optionally, the step of establishing the echo signal model in S1 includes:

[0013] Using a linear frequency modulated continuous wave signal as the radar transmission signal, the expression is:

[0014]

[0015] In the formula, k c =B / T is the frequency modulation slope, representing the rate at which the frequency changes with time; B is the bandwidth; T is the pulse width; f c It is the initial frequency of the radar's transmitted signal;

[0016] The target's echo signal s r (t) represents the delay of the radar transmitted signal s0(t), expressed as:

[0017]

[0018] In the formula, Δt=2R / v c v is the time delay of the target at a distance R. c The speed of light;

[0019] The polarization expression for the target echo is:

[0020] h s =Sh t

[0021] In the formula, For radar transmit polarization, where θ t and These are the radar's polarization angle and phase difference, respectively. Let be the target scattering matrix.

[0022] Optionally, the preprocessing step in S2 includes:

[0023] The radar echo signal undergoes down-conversion and pulse compression processing, resulting in the following signal expression:

[0024]

[0025] Extract the peak points of each pulse signal and splice them together to form a peak signal;

[0026] The peak points of the pulse signal and the sampling points within its main lobe are removed, and the resulting signals are spliced ​​together to form the noise floor signal.

[0027] Optionally, the step of S3 to solve for the polarization parameters of the target signal includes:

[0028] Based on the peak points after coherent accumulation of the peak signals, the maximum likelihood estimate of the polarization coherence matrix of the target signal is calculated, and the estimate is expressed as:

[0029]

[0030] In the formula, P = [P H ,P V ] r P H P represents the horizontal polarization component at the peak point. V The vertical polarization component at the peak point;

[0031] Based on the polarization coherence matrix of the target signal, it is converted into a Stokes vector, and the estimated value of the target signal's Stokes vector is obtained, expressed as:

[0032] J s =[g0,g1,g2,g3] T =R[C sHH C sHV C sVH C sWV ] T

[0033]

[0034] Using the Stokes vector estimate of the target signal, the polarization parameters of the target signal, including the polarization angle θ, are calculated. S Phase difference

[0035]

[0036] Optionally, the step of S4, which solves for the polarization parameters of the interference signal, includes:

[0037] Based on the accumulated results of the noise floor signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is calculated, and the estimate is expressed as:

[0038]

[0039] In the formula, N is the number of sampling points for the noise floor signal, and J n =[J Hn J Vn ] T Let J be the nth sampling point of the noise floor signal. Hn For J n Horizontal polarization component, J Vn For J n The vertical polarization component.

[0040] Based on the polarization coherence matrix of the interference signal, it is converted into a Stokes vector, and the estimated value of the Stokes vector of the interference signal is obtained, expressed as:

[0041] J J =[g0,g1,g2,g3] T =R[C JHH C JHV C JH C JWV ] T

[0042]

[0043] Using the Stokes vector estimate of the interference signal, the polarization parameters of the interference signal, including the polarization angle θ, are calculated. S Phase difference

[0044]

[0045] Optionally, the oblique projection matrix in S5 is:

[0046]

[0047] In the formula, The polarization parameters of the target echo. These are the polarization parameters of the interference signal.

[0048] Optionally, the step of performing polarization oblique projection polarization filtering on the radar echo signal in S5 is as follows:

[0049] The radar echo signal, after being processed by down-conversion and pulse compression, is multiplied by the oblique projection matrix, and the expression is:

[0050] E AB (As r +Bs J +C)=As r +E AB C

[0051] In the formula, C = [n m n c ] r The noise signal is in polarized form.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. By adaptively solving for the maximum likelihood estimate of the polarization coherence matrix of the target and the interference signal, high-precision estimation results of the polarization parameters of the target and the interference signal can be obtained, thereby improving the high-power interference suppression performance;

[0054] 2. By using the estimation results of the polarization parameters of the target and the interference signal, an oblique projection transformation matrix is ​​constructed, which can effectively suppress high-power interference and reduce the energy loss of the target signal under the condition that the polarization parameters of the target and the interference signal are not orthogonal. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of a method according to an embodiment of the present invention;

[0056] Figure 2 This is a simulation result diagram of the target signal polarization parameter estimation error in an embodiment of the present invention;

[0057] Figure 3 This is a simulation result diagram of the interference signal polarization parameter estimation error in an embodiment of the present invention;

[0058] Figure 4 This is a range-Doppler image of the radar echo signal according to an embodiment of the present invention;

[0059] Figure 5 A comparison chart showing the interference suppression performance of traditional polarization filtering methods;

[0060] Figure 6 This is a comparison chart of the interference suppression effects of embodiments of the present invention. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] Please see Figure 1 The present invention discloses a high-power interference suppression method based on polarization domain oblique projection filtering, comprising:

[0063] S1. Establish a radar echo signal model, including a target signal model, an interference signal model, and a noise signal model;

[0064] S2. Preprocess the radar echo signal to obtain the peak signal and the noise floor signal;

[0065] S3. Based on the peak signal, solve for the maximum likelihood estimate of the polarization coherence matrix of the target signal, and after converting it into a Stokes vector, solve for the polarization parameters of the target signal.

[0066] S4. Based on the noise floor signal, solve for the maximum likelihood estimate of the polarization coherence matrix of the interference signal, and convert it into a Stokes vector to solve for the polarization parameters of the interference signal.

[0067] S5. Based on the polarization parameters of the target signal and the interference signal in S4, construct the oblique projection matrix and perform polarization oblique projection filtering on the radar echo signal.

[0068] In this way, by solving the maximum likelihood estimate of the polarization coherence matrix of the target and the interference signal, the polarization parameters of the target and the interference signal are obtained. Based on this, a polarization domain oblique projection matrix is ​​constructed to correct the traditional polarization filtering method, and polarization oblique projection filtering is performed on the radar echo signal. Thus, under the condition that the polarization parameters of the target and the interference are not orthogonal, high-power interference is effectively suppressed and the energy loss of the target signal is reduced.

[0069] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided in the application, for dual-receiver polarized radar, the steps for establishing the echo signal model in S1 include:

[0070] Using a linear frequency modulated continuous wave signal as the radar transmission signal, the expression is:

[0071]

[0072] In the formula, k c =B / T is the frequency modulation slope, representing the rate at which the frequency changes with time; B is the bandwidth; T is the pulse width; f c It is the initial frequency of the radar's transmitted signal;

[0073] The target's echo signal s r (t) represents the delay of the radar transmitted signal s0(t), and its expression is:

[0074]

[0075] In the formula, Δt=2R / v c v is the time delay of the target at a distance R. c The speed of light;

[0076] The polarization expression for the target echo is:

[0077] h s =Sh t

[0078] In the formula, For radar transmit polarization, where θ t and These are the radar's polarization angle and phase difference, respectively. Let be the target scattering matrix.

[0079] As a specific implementation of the high-power interference suppression method based on polarization domain oblique projection filtering provided in the application, the steps in S1 for establishing the interference signal model and the noise signal model include:

[0080] Using radio frequency noise interference as a high-power interference signal, the expression is:

[0081] s J (t)=A J exp(j2πf J t)

[0082] In the formula, A is within the radar's operating frequency range. J For the interference amplitude, f J The carrier frequency of the interference;

[0083] The interference polarization mode is:

[0084]

[0085] Where, θ J and These are the polarization angle and phase difference of the interference signal, respectively.

[0086] Using Gaussian white noise as the noise signal, the expression is:

[0087] n = [n m n c ] T

[0088] In the formula, n m and n c The noise from the main receiving channel and the auxiliary receiving channel are respectively, and both follow a normal distribution.

[0089] The expression for the received signal at the radar is:

[0090] s = h s s r +h J s J +[n m n c ] T .

[0091] As a specific implementation of the high-power interference suppression method based on polarization domain oblique projection filtering provided in the application, the preprocessing step in S2 includes:

[0092] The radar echo signal undergoes down-conversion and pulse compression processing, resulting in the following signal expression:

[0093]

[0094] Extract the peak points of each pulse signal and splice them together to form a peak signal;

[0095] The peak points of the pulse signal and the sampling points within its main lobe are removed, and the resulting signals are spliced ​​together to form the noise floor signal.

[0096] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided in the application, the steps of S3 in solving the polarization parameters of the target signal include:

[0097] Based on the peak points after coherent accumulation of the peak signals, the maximum likelihood estimate of the polarization coherence matrix of the target signal is calculated, and the estimate is expressed as:

[0098]

[0099] In the formula, P = [P H ,P V ] r P H P represents the horizontal polarization component at the peak point. V The vertical polarization component at the peak point;

[0100] Based on the polarization coherence matrix of the target signal, it is converted into a Stokes vector, and the estimated value of the target signal's Stokes vector is obtained, expressed as:

[0101] J s =[g0,g1,g2,g3] T =R[C sHH C sHV C sVH C sWV ] T

[0102]

[0103] In the Stokes vector, g0 describes the power density of the electromagnetic wave, g1 is the power difference between the two orthogonal components under the horizontal and vertical polarization bases, g2 is the power difference between the two orthogonal components of the electromagnetic wave under the 45° and 135° orthogonal polarization bases, and g3 is the power difference between the two orthogonal components of the electromagnetic wave under the left and right circular polarization bases.

[0104] Using the Stokes vector estimate of the target signal, the polarization parameters of the target signal, including the polarization angle θ, are calculated. S Phase difference

[0105]

[0106] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided in the application, the step S4 of solving the polarization parameters of the interference signal includes:

[0107] Based on the accumulated results of the noise floor signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is calculated, and the estimate is expressed as:

[0108]

[0109] In the formula, N is the number of sampling points for the noise floor signal, and J n =[J Hn J Vn ] T Let J be the nth sampling point of the noise floor signal. Hn For J n Horizontal polarization component, J Vn For J n The vertical polarization component.

[0110] Based on the polarization coherence matrix of the interference signal, it is converted into a Stokes vector, and the estimated value of the Stokes vector of the interference signal is obtained, expressed as:

[0111] J J =[g0,g1,g2,g3] T =R[C JHH C JHV C JH C JWV ] T

[0112]

[0113] Using the Stokes vector estimate of the interference signal, the polarization parameters of the interference signal, including the polarization angle θ, are calculated. S Phase difference

[0114]

[0115] As a specific implementation of the high-power interference suppression method based on polarization domain oblique projection filtering provided in the application, according to the polarization parameters of the target signal and the interference signal, the oblique projection matrix in S5 is:

[0116]

[0117] In the formula, The polarization parameters of the target echo. These are the polarization parameters of the interference signal.

[0118] As a specific implementation of the high-power interference suppression method based on polarization domain oblique projection filtering provided in the application, the step of performing polarization oblique projection polarization filtering on the radar echo signal in S5 is as follows:

[0119] The radar echo signal, after being processed by down-conversion and pulse compression, is multiplied by the oblique projection matrix, and the expression is:

[0120] E AB (As r +Bs J +C)=As r +E AB C

[0121] In the formula, C = [n m n c ] r The noise signal is in polarized form.

[0122] As can be seen from the above equation, after oblique projection filtering, the interference signal Bs in the radar echo... J The interference signal has been effectively eliminated, meaning that the method described above can effectively suppress interference signals. Simultaneously, after the above transformation, the target signal As in the radar echo... r It can be accurately preserved, meaning that this method will not cause any loss of target signal energy.

[0123] In the experiment, the performance of the proposed method for estimating the polarization parameters of the target and the interference was first verified through simulation. The radar transmitted signal was a linear frequency modulated continuous wave, and the high-power interference type was radio frequency noise interference.

[0124] The simulation settings are as follows: carrier frequency 1.2 GHz, signal pulse width 24 μs; target amplitude 1, target signal-to-noise ratio (SNR) varying from -10 dB to 20 dB, target signal polarization angle and phase difference randomly generated; interference signal frequency 1.22 GHz, interference-to-noise ratio (JNR) varying from 0 dB to 30 dB, interference signal polarization angle and phase difference randomly generated.

[0125] To conduct 500 Monte Carlo experiments, please refer to [link / reference]. Figure 2 The curve showing the estimation error of the target signal polarization parameters as a function of SNR is shown below. Figure 3 The curve shows the estimation error of the interference signal polarization parameters as a function of JNR. This demonstrates that, under the current simulation conditions, this method can accurately estimate the polarization parameters of both the target and the interference signals.

[0126] Specifically, the estimation error of the polarization angle of the target signal is within 2.5°, and the estimation error of the phase difference of the target signal is within 6°; the estimation error of the polarization angle of the interference signal is within 0.3°, and the estimation error of the phase difference of the interference signal is within 0.5°.

[0127] Then, the suppression effect of this method on high-power interference was verified by simulation. The simulation settings were: target signal polarization angle of 30° and phase difference of 60°; interference signal polarization angle of 5° and phase difference of -30°; amplitude ratio of interference to signal of 20; JNR of 0dB; and other parameters remained unchanged.

[0128] Please see Figure 4 This represents the two-dimensional range Doppler spectrum of the radar echo signal after down-conversion and pulse compression, with the target amplitude being approximately 104.03 dB. Please refer to [link / reference]. Figure 5 and Figure 6 Traditional polarization filtering methods have a certain suppression effect on high-power interference, but they will cause a target amplitude loss of about 8.55dB. In contrast, this method can reduce the target amplitude loss while effectively suppressing interference, causing a target amplitude loss of about 0.01dB when the target amplitude is about 104.03dB.

[0129] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-power interference suppression method based on polarization domain oblique projection filtering, characterized in that, include: S1. Establish a radar echo signal model, including a target signal model, an interference signal model, and a noise signal model; S2. Preprocess the radar echo signal to obtain the peak signal and the noise floor signal; S3. Based on the peak signal, solve for the maximum likelihood estimate of the polarization coherence matrix of the target signal, and after converting it into a Stokes vector, solve for the polarization parameters of the target signal. S4. Based on the noise floor signal, solve for the maximum likelihood estimate of the polarization coherence matrix of the interference signal, and convert it into a Stokes vector to solve for the polarization parameters of the interference signal. S5. Based on the polarization parameters of the target signal and the interference signal in S4, construct the oblique projection matrix and perform polarization oblique projection filtering on the radar echo signal. The steps in S3 for solving the polarization parameters of the target signal include: Based on the peak points after coherent accumulation of the peak signals, the maximum likelihood estimate of the polarization coherence matrix of the target signal is calculated, and the estimate is expressed as: In the formula, P = [P H ,P V ] r P H P represents the horizontal polarization component at the peak point. V The vertical polarization component at the peak point; Based on the polarization coherence matrix of the target signal, it is converted into a Stokes vector, and the estimated value of the target signal's Stokes vector is obtained, expressed as: J s =[g0,g1,g2,g3]T=R[C sHH ,C sHV ,C sVH ,C sWV ] T In the Stokes vector, g0 describes the power density of the electromagnetic wave, g1 is the power difference between the two orthogonal components under the horizontal and vertical polarization bases, g2 is the power difference between the two orthogonal components of the electromagnetic wave under the 45° and 135° orthogonal polarization bases, and g3 is the power difference between the two orthogonal components of the electromagnetic wave under the left and right circular polarization bases. Using the Stokes vector estimate of the target signal, the polarization parameters of the target signal, including the polarization angle θ, are calculated. s Phase difference The steps in S4 for solving the polarization parameters of the interference signal include: Based on the accumulated results of the noise floor signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is calculated, and the estimate is expressed as: In the formula, N is the number of sampling points for the noise floor signal, and J n =[J Hn J Vn ] T Let J be the nth sampling point of the noise floor signal. Hn For J n Horizontal polarization component, J Vn For J n The vertical polarization component; Based on the polarization coherence matrix of the interference signal, it is converted into a Stokes vector, and the estimated value of the Stokes vector of the interference signal is obtained, expressed as: J J =[g0,g1,g2,g3] T =R[C JHH ,C JHV ,C JH ,C JWV ] T Using the Stokes vector estimate of the interference signal, the polarization parameters of the interference signal, including the polarization angle θ, are calculated. S Phase difference 2. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 1, characterized in that: The steps for establishing the echo signal model in S1 include: Using a linear frequency modulated continuous wave signal as the radar transmission signal, the expression is: In the formula, k c =B / T is the frequency modulation slope, representing the rate at which the frequency changes with time; B is the bandwidth; T is the pulse width; f c It is the initial frequency of the radar's transmitted signal; The target's echo signal s r (t) represents the delay of the radar transmitted signal s0(t), and its expression is: In the formula, Δt=2R / v c v is the time delay of the target at a distance R. c The speed of light; The polarization expression for the target echo is: h s =Sh t In the formula, For radar transmit polarization, where θ t and These are the radar's polarization angle and phase difference, respectively. Let be the target scattering matrix.

3. The high-power interference suppression method based on polarization exp domain oblique projection filtering according to claim 2, characterized in that: The steps in S1 to establish the interference signal model and the noise signal model include: Using radio frequency noise interference as a high-power interference signal, the expression is: s J (t)=A J exp(j2πf J t) In the formula, A is within the radar's operating frequency range. J For the interference amplitude, f J The carrier frequency of the interference; The interference polarization mode is: Where, θ J and These are the polarization angle and phase difference of the interference signal, respectively. Using Gaussian white noise as the noise signal, the expression is: n=[n m n c ] T In the formula, n m and n c The noise from the main receiving channel and the auxiliary receiving channel are respectively, and both follow a normal distribution. The expression for the received signal at the radar is: s=h s s r +h J s J +[n m n c ] T 。 4. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 3, characterized in that: The preprocessing steps in S2 include: The radar echo signal undergoes down-conversion and pulse compression processing, resulting in the following signal expression: Extract the peak points of each pulse signal and splice them together to form a peak signal; The peak points of the pulse signal and the sampling points within its main lobe are removed, and the resulting signals are spliced ​​together to form the noise floor signal.

5. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 4, characterized in that: The oblique projection matrix in S5 is: In the formula, The polarization parameters of the target echo. These are the polarization parameters of the interference signal.

6. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 5, characterized in that: The step in S5 to perform polarization oblique projection polarization filtering on the radar echo signal is as follows: The radar echo signal, after being processed by down-conversion and pulse compression, is multiplied by the oblique projection matrix, and the expression is: ITS AB (As r +Bs J +C)=As r +E AB C In the formula, C = [n m n c ] r The noise signal is in polarized form.

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