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

Abstract

The invention discloses a high-power interference suppression method based on polarization domain oblique projection filtering, and the method comprises the steps: building a radar echo signal model which comprises a target signal model, an interference signal model and a noise signal model; preprocessing the radar echo signal to obtain a peak value and a ground noise signal; based on the peak value and the ground noise signal, respectively solving maximum likelihood estimation values of the polarization coherence matrix of the target and the interference signal, converting the maximum likelihood estimation values into Stokes vectors, and solving polarization parameters of the target and the interference signal; and then an oblique projection matrix is constructed, and polarization oblique projection filtering processing is carried out on the radar echo signals. Polarization parameters of a target and an interference signal are obtained by solving a maximum likelihood estimation value of a polarization coherence matrix of the target and the interference signal, a polarization domain oblique projection matrix is constructed to correct a traditional polarization filtering method, polarization oblique projection filtering is carried out on a radar echo signal, and therefore under the condition that the polarization parameters of the target and the interference are non-orthogonal, the polarization of the target and the interference signal is improved. And high-power interference is effectively suppressed and target signal energy loss is reduced.

Description

Technical Field

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

[0002] The essence of radar anti-interference technology is to use the characteristic difference between interference and target signals to suppress interference signals while retaining or enhancing target signals. In modern electronic warfare, radars face complex and diverse types of interference. Among them, high-power suppression interference suppresses target signals by transmitting noise signals or other specific signals, making it impossible for radar to accurately detect targets. With the continuous development of high-power suppression interference technology, the performance of conventional time, frequency, and space domain interference suppression methods can no longer meet actual needs.

[0003] Polarization domain features are vector features that can quantitatively describe radar electromagnetic waves. Existing polarization filtering methods are based on the difference in polarization domain features between target signals and interference signals. By orthogonal reception of interference signals, high-power interference can be effectively suppressed. However, in practical applications, the polarization parameters of the target and interference are usually non-orthogonal. Therefore, existing polarization filtering methods face the problem of target signal energy loss while suppressing interference. Summary of the invention

[0004] In view of the above problems, the present invention proposes a high-power interference suppression method based on polarization domain oblique projection filtering, which well solves the problems in the prior art.

[0005] In order to achieve the above object, 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, comprising:

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

[0008] S2, preprocessing the radar echo signal to obtain a peak signal and a background noise signal;

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

[0010] S4. Based on the background noise signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is solved, and after converting it into a Stokes vector, the polarization parameters of the interference signal are solved;

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

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

[0013] The linear frequency modulated continuous wave signal is used as the radar transmitting signal, and the expression is:

[0014]

[0015] In the formula, k c =B / T is the frequency modulation slope, which represents the rate at which the frequency changes over time; B is the bandwidth; T is the pulse width; f c is the initial frequency of the radar transmission signal;

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

[0017]

[0018] Where, Δt=2R / v c is the delay time of the target at distance R, v c is the speed of light;

[0019] The target echo polarization expression is:

[0020] h s =Sh t

[0021] In the formula, is the radar transmit polarization, where θ t and are the polarization angle and phase difference of the radar transmission, is the target scattering matrix.

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

[0023] The radar echo signal is down-converted and pulse compressed, and the signal expression after processing is:

[0024]

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

[0026] Eliminate the peak point of the pulse signal and the sampling points in its main lobe, and splice them together to form a background noise signal.

[0027] Optionally, the step of solving the target signal polarization parameter in S3 includes:

[0028] Based on the peak point after the coherent accumulation of the peak signal, the maximum likelihood estimate of the polarization coherence matrix of the target signal is calculated. The estimated value is expressed as:

[0029]

[0030] Where, P = [P H , P V ] r , P H is the horizontal polarization component at the peak point, P V is the vertical polarization component of the peak point;

[0031] According to the polarization coherence matrix of the target signal, it is converted into a Stokes vector to obtain the estimated value of the target signal Stokes vector, which is expressed as:

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

[0033]

[0034] The target signal Stokes vector estimate is used to calculate the target signal polarization parameters, including the target signal polarization angle θ. S Phase Difference

[0035]

[0036]

[0037] Optionally, the step of solving the polarization parameters of the interference signal in S4 includes:

[0038] Based on the accumulation result of the background noise signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is calculated. The estimate is expressed as:

[0039]

[0040] Where N is the number of sampling points of the background noise signal, J n =[J Hn , J Vn ] T is the nth sampling point of the background noise signal, where J Hn For J n The horizontal polarization component, J Vn For Jn The vertical polarization component of .

[0041] According to the polarization coherence matrix of the interference signal, it is converted into a Stokes vector to obtain the estimated value of the Stokes vector of the interference signal, which is expressed as:

[0042] J J =[g0, g1, g2, g3] T =R[C JHH , C JHV , C JH , C JWV ] T

[0043]

[0044] The Stokes vector estimate of the interference signal is used to calculate the polarization parameters of the interference signal, including the polarization angle θ of the interference signal. S Phase Difference

[0045]

[0046]

[0047] Optionally, the oblique projection matrix in S5 is:

[0048]

[0049] In the formula, is the polarization parameter of the target echo, is the polarization parameter of the interference signal.

[0050] Optionally, the step of performing polarization oblique projection polarization filtering processing on the radar echo signal in S5 is:

[0051] Multiply the radar echo signal after down-conversion, pulse compression and other processing by the oblique projection matrix, and the expression is:

[0052] E AB (As γ +Bs J + C) = As γ +E AB C

[0053] In the formula, C = [n m n c ] r is the noise signal in polarized form.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. By adaptively solving the maximum likelihood estimation value of the polarization coherence matrix of the target and interference signals, high-precision estimation results of the polarization parameters of the target and interference signals can be obtained, thereby improving the high-power interference suppression performance;

[0056] 2. Using the estimated results of the polarization parameters of the target and interference signals, the 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 interference signals are non-orthogonal. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic diagram of a method according to an embodiment of the present invention;

[0058] Figure 2 This is a diagram of target signal polarization parameter estimation error simulation results of an embodiment of the present invention;

[0059] Figure 3 This is a simulation result diagram of interference signal polarization parameter estimation error according to an embodiment of the present invention;

[0060] Figure 4 A radar echo signal range-Doppler diagram according to an embodiment of the present invention;

[0061] Figure 5 This is a comparison chart of the interference suppression effect of the traditional polarization filtering method;

[0062] Figure 6 2 is a comparison diagram of interference suppression effects of an embodiment of the present invention. DETAILED DESCRIPTION

[0063] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] See also Figure 1 , a high-power interference suppression method based on polarization domain oblique projection filtering disclosed in an embodiment of the present invention, comprising:

[0065] S1. Establishing a radar echo signal model, including a target signal model, an interference signal model and a noise signal model;

[0066] S2, preprocessing the radar echo signal to obtain a peak signal and a background noise signal;

[0067] S3. Based on the peak signal, the maximum likelihood estimate of the polarization coherence matrix of the target signal is solved, and after converting it into a Stokes vector, the polarization parameters of the target signal are solved;

[0068] S4. Based on the background noise signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is solved, and after converting it into a Stokes s vector, the polarization parameters of the interference signal are solved;

[0069] S5. Based on the polarization parameters of the target signal and the interference signal in S4, an oblique projection matrix is ​​constructed to perform polarization oblique projection filtering on the radar echo signal.

[0070] In this way, the polarization parameters of the target and interference signals are obtained by solving the maximum likelihood estimate of the polarization coherence matrix of the target and interference signals. On this basis, the polarization domain oblique projection matrix is ​​constructed to correct the traditional polarization filtering method, and the radar echo signal is subjected to polarization oblique projection filtering, thereby effectively suppressing high-power interference and reducing the target signal energy loss under the condition that the target and interference polarization parameters are non-orthogonal.

[0071] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided by the application, for a dual-receive polarization radar, the step of establishing an echo signal model in S1 includes:

[0072] The linear frequency modulated continuous wave signal is used as the radar transmitting signal, and the expression is:

[0073]

[0074] In the formula, k c =B / T is the frequency modulation slope, which represents the rate at which the frequency changes over time; B is the bandwidth; T is the pulse width; f c is the initial frequency of the radar transmission signal;

[0075] The target's echo signal s r (t) is the delay of the radar transmission signal s0(t), expressed as:

[0076]

[0077] Where, Δt=2R / v c is the delay time of the target at distance R, v c is the speed of light;

[0078] The target echo polarization expression is:

[0079] h s =Sh t

[0080] In the formula, is the radar transmit polarization, where θ t and are the polarization angle and phase difference of the radar transmission, is the target scattering matrix.

[0081] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided by the application, the step of establishing an interference signal model and a noise signal model in S1 includes:

[0082] Using radio frequency noise interference as the high-power interference signal, the expression is:

[0083] s J (t) = A J exp(j2πf J t)

[0084] In the formula, within the operating frequency range of the radar, A J is the interference amplitude, f J is the carrier frequency of the interference;

[0085] The interference polarization mode is:

[0086]

[0087] Among them, θ J and are the polarization angle and phase difference of the interference signal respectively;

[0088] Gaussian white noise is used as the noise signal, and the expression is:

[0089] n=[n m n c ] T

[0090] Where n m and n c are the noise of the main receiving channel and the auxiliary receiving channel respectively, which obey the normal distribution.

[0091] The received signal expression at the radar is:

[0092] s=h s s r +h J s J +[n m n c ] T .

[0093] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided by the application, the preprocessing step in S2 includes:

[0094] The radar echo signal is down-converted and pulse compressed, and the signal expression after processing is:

[0095]

[0096] Extract the peak point of each pulse signal and splice them to form a peak signal;

[0097] Eliminate the peak point of the pulse signal and the sampling points in its main lobe, and splice them together to form a background noise signal.

[0098] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided by the application, the step of S3 solving the polarization parameters of the target signal includes:

[0099] Based on the peak point after the coherent accumulation of the peak signal, the maximum likelihood estimate of the polarization coherence matrix of the target signal is calculated. The estimated value is expressed as:

[0100]

[0101] Where, P = [P H , P V ] r , P H is the horizontal polarization component at the peak point, P V is the vertical polarization component of the peak point;

[0102] According to the polarization coherence matrix of the target signal, it is converted into a Stokes vector to obtain the estimated value of the target signal Stokes vector, which is expressed as:

[0103] J s =[g0, g1, g2, g3] T =R[C sHH , C sHV , C sVH , C sWV ] T

[0104]

[0105] Among them, g0 in the Stokes vector describes the power density of the electromagnetic wave, g1 is the power difference between the two orthogonal components under the horizontal and vertical polarization basis, g2 is the power difference between the two orthogonal components of the electromagnetic wave under the 45° and 135° orthogonal polarization basis, and g3 is the power difference between the two orthogonal components of the electromagnetic wave under the left-hand and right-hand circular polarization basis.

[0106] The target signal Stokes vector estimate is used to calculate the target signal polarization parameters, including the target signal polarization angle θ. S Phase Difference

[0107]

[0108] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided by the application, the step of solving the polarization parameters of the interference signal in S4 includes:

[0109] Based on the accumulation result of the background noise signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is calculated. The estimate is expressed as:

[0110]

[0111] Where N is the number of sampling points of the background noise signal, J n =[J Hn , J Vn ] T is the nth sampling point of the background noise signal, where J Hn For J n The horizontal polarization component, J Vn For J n The vertical polarization component of .

[0112] According to the polarization coherence matrix of the interference signal, it is converted into a Stokes vector to obtain the estimated value of the Stokes vector of the interference signal, which is expressed as:

[0113] J J =[g0, g1, g2, g3] T =R[C JHH , C JHV , C JH , C JWV ] T

[0114]

[0115] The Stokes vector estimate of the interference signal is used to calculate the polarization parameters of the interference signal, including the polarization angle θ of the interference signal. S Phase Difference

[0116]

[0117]

[0118] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided by the application, according to the polarization parameters of the target signal and the interference signal solved, the oblique projection matrix in S5 is:

[0119]

[0120] In the formula, is the polarization parameter of the target echo, is the polarization parameter of the interference signal.

[0121] As a specific implementation of a high-power interference suppression method based on polarization domain oblique projection filtering provided by the application, the step of performing polarization oblique projection polarization filtering processing on the radar echo signal in S5 is:

[0122] Multiply the radar echo signal after down-conversion, pulse compression and other processing by the oblique projection matrix, and the expression is:

[0123] E AB (As γ +Bs J + C) = As γ +E AB C

[0124] In the formula, C = [n m n c ] r is the noise signal in polarized form.

[0125] From the above formula, we can see that after the oblique projection filtering process, the interference signal Bs in the radar echo is J has been effectively eliminated, that is, the method of this invention can effectively suppress the interference signal. At the same time, after the above transformation, the target signal As in the radar echo γ It can be accurately retained, that is, this method will not cause target signal energy loss.

[0126] In the experiment, the target and interference polarization parameter estimation performance of this method is first verified by simulation. The radar transmission signal is a linear frequency modulated continuous wave, and the high-power interference type is radio frequency noise interference.

[0127] The simulation sets the carrier frequency to 1.2 GHz and the signal pulse width to 24us; the target amplitude is 1, the target signal-to-noise ratio (SNR) varies from -10dB to 20dB, and the target signal polarization angle and phase difference are randomly generated; the interference signal frequency is 1.22 GHz, the interference-to-noise ratio (JNR) varies from 0dB to 30dB, and the interference signal polarization angle and phase difference are randomly generated.

[0128] To perform 500 Monte Carlo experiments, see Figure 2 , is the curve of the estimated error of the target signal polarization parameter as a function of SNR, see Figure 3 , is the curve of the estimated error of the polarization parameter of the interference signal as the JNR changes. It can be seen that under the current simulation conditions, this method can accurately estimate the polarization parameters of the target and interference signals.

[0129] Specifically, the estimated error of the target signal polarization angle is within 2.5°, and the estimated error of the target signal phase difference is within 6°; the estimated error of the interference signal polarization angle is within 0.3°, and the estimated error of the interference signal phase difference is within 0.5°.

[0130] Then, the method is verified by simulation to suppress high-power interference. The simulation sets the target signal polarization angle to 30° and the phase difference to 60°; the interference signal polarization angle to 5° and the phase difference to 30°; the amplitude ratio of interference to signal is 20, the JNR is 0dB, and the other parameters remain unchanged.

[0131] See also Figure 4 , is the signal range Doppler two-dimensional spectrum after the radar echo is processed by down-conversion and pulse compression, in which the target amplitude is about 104.03dB. Figure 5 and Figure 6 The traditional polarization filtering method has a certain suppression effect on high-power interference, but it will cause a target amplitude loss of about 8.55dB; in contrast, this method can effectively suppress the interference while reducing the target amplitude loss. When the target amplitude is about 104.03dB, it causes a target amplitude loss of about 0.01dB.

[0132] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in 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, preprocessing the radar echo signal to obtain a peak signal and a background noise signal; S3. Based on the peak signal, the maximum likelihood estimate of the polarization coherence matrix of the target signal is solved, and after converting it into a Stokes vector, the polarization parameters of the target signal are solved; S4. Based on the background noise signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is solved, and after converting it into a Stokes vector, the polarization parameters of the interference signal are solved; S5. Based on the polarization parameters of the target signal and the interference signal in S4, an oblique projection matrix is ​​constructed to perform polarization oblique projection filtering on the radar echo signal.

2. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 1 is characterized in that: The step of establishing the echo signal model in S1 includes: The linear frequency modulated continuous wave signal is used as the radar transmitting signal, and the expression is: In the formula, k c =B / T is the frequency modulation slope, which represents the rate at which the frequency changes over time; B is the bandwidth; T is the pulse width; f c is the initial frequency of the radar transmission signal; The target's echo signal s r (t) is the delay of the radar transmission signal s0(t), expressed as: Where, Δt = 2R / v c is the delay time of the target at distance R, v c is the speed of light; The target echo polarization expression is: h s =Sh t In the formula, is the radar transmit polarization, where θ t and are the polarization angle and phase difference of the radar transmission, is the target scattering matrix.

3. The high-power interference suppression method based on polarization exp domain oblique projection filtering according to claim 2 is characterized in that: The step of establishing the interference signal model and the noise signal model in S1 includes: Using radio frequency noise interference as the high-power interference signal, the expression is: s J (t)=A J exp(j2πf J t) In the formula, within the operating frequency range of the radar, A J is the interference amplitude, f J is the carrier frequency of the interference; The interference polarization mode is: Among them, θ J and are the polarization angle and phase difference of the interference signal respectively; Gaussian white noise is used as the noise signal, and the expression is: n=[n m n c ] T Where n m and n c are the noise of the main receiving channel and the auxiliary receiving channel respectively, which obey the normal distribution. The received signal expression 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 is characterized in that: The preprocessing step in S2 includes: The radar echo signal is down-converted and pulse compressed, and the signal expression after processing is: Extract the peak point of each pulse signal and splice them to form a peak signal; Eliminate the peak point of the pulse signal and the sampling points in its main lobe, and splice them together to form a background noise signal.

5. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 4 is characterized in that: The step of solving the target signal polarization parameter in S3 includes: Based on the peak point after the coherent accumulation of the peak signal, the maximum likelihood estimate of the polarization coherence matrix of the target signal is calculated. The estimated value is expressed as: Where, P = [P H , P v ] r , P H is the horizontal polarization component at the peak point, P v is the vertical polarization component of the peak point; According to the polarization coherence matrix of the target signal, it is converted into a Stokes vector to obtain the estimated value of the target signal Stokes vector, which is expressed as: J s =[g o ,g1,g2,g3] T R[C sHH ,C sHV ,C sVH ,C swV ] T The target signal Stokes vector estimate is used to calculate the target signal polarization parameters, including the target signal polarization angle θ. S Phase Difference 6. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 5 is characterized in that: The step of solving the polarization parameters of the interference signal in S4 includes: Based on the accumulation result of the background noise signal, the maximum likelihood estimate of the polarization coherence matrix of the interference signal is calculated. The estimate is expressed as: Where N is the number of sampling points of the background noise signal, J n =[J Hn , J Vn ] T is the nth sampling point of the background noise signal, where J Hn For J n The horizontal polarization component, J Vn For J n The vertical polarization component of . According to the polarization coherence matrix of the interference signal, it is converted into a Stokes vector to obtain the estimated value of the Stokes vector of the interference signal, which is expressed as: J J =[g0,g1,g2,g3] T =R[C JHH ,C JHV ,C JH ,C JWV ] T The Stokes vector estimate of the interference signal is used to calculate the polarization parameters of the interference signal, including the polarization angle θ of the interference signal. S Phase Difference 7. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 6 is characterized in that: The oblique projection matrix in S5 is: In the formula, is the polarization parameter of the target echo, is the polarization parameter of the interference signal.

8. The high-power interference suppression method based on polarization domain oblique projection filtering according to claim 7 is characterized in that: The step of performing polarization oblique projection polarization filtering processing on the radar echo signal in S5 is: Multiply the radar echo signal after down-conversion, pulse compression and other processing by the oblique projection matrix, and the expression is: ITS AB (As γ +Bs J +C)=As γ +E AB C In the formula, C = [n m n c ] r is the noise signal in polarized form.

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