CN113466801A - Circular array-based secondary radar space-time main lobe interference resisting method - Google Patents

Circular array-based secondary radar space-time main lobe interference resisting method Download PDF

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CN113466801A
CN113466801A CN202110524418.2A CN202110524418A CN113466801A CN 113466801 A CN113466801 A CN 113466801A CN 202110524418 A CN202110524418 A CN 202110524418A CN 113466801 A CN113466801 A CN 113466801A
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main lobe
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CN113466801B (en
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李军
李心珂
尉泽华
陈家喜
亢海龙
廖桂生
朱圣棋
曾操
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Xidian University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract

The invention provides a circular array-based secondary radar space-time main lobe interference resisting method, which is characterized in that a space-time two-dimensional blocking matrix based on a circular array is constructed aiming at a received signal of a secondary radar inquiry end based on a space-time circular array model and the azimuth information of a main lobe interference signal; preprocessing array received data by utilizing a space-time two-dimensional blocking matrix to obtain preprocessed received data; inhibiting the sidelobe interference signal by using a method combining diagonal loading and linear constraint to obtain a signal after array processing; and despreading the signals after array processing by using a spreading code, comparing the signals with the original signals, and calculating to obtain the bit error rate. When high-power compression type interference exists in a main lobe of a secondary radar interrogator end, the main lobe interference can be effectively inhibited, the output signal-to-interference-and-noise ratio is improved, and the method has good stability and effectiveness.

Description

Circular array-based secondary radar space-time main lobe interference resisting method
Technical Field
The invention belongs to the technical field of radar main lobe interference resistance, and particularly relates to a circular array-based secondary radar space-time main lobe interference resistance method.
Background
Secondary radars play an important role in both modern military and civilian fields. The civil air traffic control secondary monitoring radar provides an important information source for airport air traffic control, air route monitoring and environment perception. In military terms, Electronic reconnaissance based on secondary radar has become an important component of the Electronic countermeasure field and has occupied a significant position in modern Electronic Warfare (EW).
With the increasingly complex application environment, various types of electromagnetic interference make the application of the secondary radar face new challenges. Especially, the interference in the main lobe direction has become an important factor influencing the secondary radar signal analysis and restricting the application of the secondary radar in a complex electromagnetic environment.
The existing space domain main lobe anti-interference method cannot solve the problem of interference suppression when an expected signal and interference are in the same direction, but the suppression method of space domain and time domain combined main lobe interference of a secondary radar faces the problem of high signal analysis error rate under strong main lobe interference, so that a suppression method for resisting main lobe interference when the secondary radar is in space is urgently needed.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a circular array-based secondary radar space-time main lobe interference resisting method. The technical problem to be solved by the invention is realized by the following technical scheme:
the invention provides a circular array-based space-time main lobe interference resisting method for a secondary radar, which is applied to a ground inquiry end of the secondary radar and comprises the following steps:
step 1: acquiring array receiving data sent by a secondary radar responder;
wherein the array received data comprises an acknowledgement signal, a main lobe interference signal and a side lobe interference signal;
step 2: carrying out MUSIC angle measurement on the array receiving data to obtain the azimuth information of the main lobe interference signal;
and step 3: constructing a space-time two-dimensional blocking matrix based on a circular array based on the azimuth information of the main lobe interference signal;
and 4, step 4: preprocessing the array receiving data by using the space-time two-dimensional blocking matrix based on the circular array, removing the main lobe interference signal component, and obtaining the preprocessed array receiving data which does not contain the main lobe interference signal;
and 5: calculating a covariance matrix of the preprocessed array receiving data;
step 6: correcting the covariance matrix and inhibiting side lobe interference signals by using a diagonal loading and linear constraint directional diagram shape preserving method to obtain array processed signals;
and 7: performing despreading operation on the signals after the array processing to obtain information codes;
and 8: comparing the information code with the original information code, and calculating to obtain an error rate;
the response signal is a signal obtained by spreading an original information code.
Optionally, the response signal is a response signal generated by using a spread spectrum technique, and the response signal is:
s(t)＝a(t)c(t)cos(2πf0t)；
wherein a (t) is original information code, c (t) is spreading code, f0Is the signal carrier frequency, s (t) is the modulated signal, t is time.
Optionally, step 2 includes:
step 21: calculating a covariance matrix of the array received data;
step 22: performing characteristic decomposition on the covariance matrix to obtain MN characteristic values;
step 23: estimating the number of the information sources according to an MDL criterion by using the characteristic value;
step 24: and under the condition that the number of the information sources is known, estimating azimuth information of the main lobe interference signal by using a MUSIC algorithm.
Optionally, step 3 includes:
step 31: setting an unsolved (MN-1) multiplied by MN dimension blocking matrix B;
step 32: construction Condition BA based on blocking matrixJ_main_stSolving the blocking matrix B to obtain a determination value of an unknown number in the blocking matrix B, wherein the determination value is 0;
wherein A isJ_main_stIs a space-time steering vector of the main lobe interference signal;
step 33: and substituting the determined value of the unknown number into the blocking matrix B to obtain a space-time two-dimensional blocking matrix.
Wherein the blocking matrix B is:
Figure BDA0003065230660000031
AJ_main_stexpressed as:
Figure BDA0003065230660000032
Figure BDA0003065230660000033
Figure BDA0003065230660000041
Figure BDA0003065230660000042
in the formula, k1＝cos(θ1-2πm/M)，k2＝cos(θ1And-2 pi (M-1)/M) is substituted into the blocking matrix B to obtain a space-time two-dimensional blocking matrix based on the circular matrix.
Optionally, the step 4 includes:
and multiplying the space-time two-dimensional blocking matrix based on the circular array by the array receiving data, removing the main lobe interference signal component, and obtaining the array receiving data which does not contain the main lobe interference signal and is preprocessed.
Optionally, the step 6 includes:
step 61: correcting the covariance matrix by utilizing a diagonal loading and linear constraint directional diagram shape preserving method to obtain a corrected covariance matrix;
step 62: adding zero point constraint to the position of the side lobe interference signal by using the corrected covariance matrix, and solving an optimal weight vector;
and step 63: and processing the preprocessed array received data by using the optimal weight vector to obtain a signal processed by the array.
Optionally, step 7 includes:
step 71: despreading the signal Z after array processing by using a spreading code c (t) to obtain an information code
Figure BDA0003065230660000043
Figure BDA0003065230660000044
Step 72: coding information
Figure BDA0003065230660000045
And comparing with the original information code a (t) to obtain the error rate.
The invention provides a circular array-based secondary radar space-time main lobe interference resisting method, which is characterized in that a space-time two-dimensional blocking matrix based on a circular array is constructed aiming at a received signal of a secondary radar inquiry end based on a space-time circular array model and the azimuth information of a main lobe interference signal; preprocessing array received data by utilizing a space-time two-dimensional blocking matrix to obtain preprocessed received data; inhibiting the sidelobe interference signal by using a method combining diagonal loading and linear constraint to obtain a signal after array processing; and despreading the signals after array processing by using a spreading code, comparing the signals with the original signals, and calculating to obtain the bit error rate. When high-power compression type interference exists in a main lobe of a secondary radar interrogator end, the main lobe interference can be effectively inhibited, the output signal-to-interference-and-noise ratio is improved, and the method has good stability and effectiveness.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
Fig. 1 is a schematic flow chart of a circular array-based secondary radar space-time main lobe interference resisting method provided by the invention;
FIG. 2 is a schematic structural diagram of a secondary radar system provided in the present invention;
fig. 3 is a schematic diagram of a space-time processing structure of a receiving end of an interrogator in a secondary radar system provided by the present invention;
FIG. 4a is a diagram of the signal coefficient l after preprocessing provided by the present inventioniA simulation result schematic diagram of the relationship with the signal frequency offset variation;
FIG. 4b is a diagram of the signal coefficient l after preprocessing provided by the present inventioniA simulation result schematic diagram of the relationship with the signal angle change;
fig. 5a is a schematic diagram of a simulation result of a relationship between an output signal-to-interference-and-noise ratio and an input signal-to-noise ratio variation under a circular array-based secondary radar space-time anti-mainlobe interference method provided by the present invention;
fig. 5b is a schematic diagram of a simulation result of a relationship between a bit error rate and an input signal-to-noise ratio variation in the circular array-based secondary radar space-time anti-mainlobe interference method provided by the invention;
fig. 6a is a schematic diagram of a simulation result of a relationship between an output signal-to-interference-and-noise ratio and a frequency deviation and an angle change of a main lobe interference in a circular array-based secondary radar space-time anti-main lobe interference method provided by the invention;
fig. 6b is a schematic diagram of a simulation result of a relationship between a bit error rate and a frequency offset and an angle change of main lobe interference in a circular array-based secondary radar space-time anti-main lobe interference method provided by an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Example one
As shown in fig. 1, the method for space-time main lobe interference resistance of a secondary radar based on a circular array provided by the present invention includes:
referring to fig. 2, fig. 2 is a schematic structural diagram of a secondary radar system provided by the present invention, which includes 1 interrogation terminal and 1 transponder, and includes 1 desired signal and K suppressed interferers, where there are a main lobe interferer and K-1 side lobe interferers. The circular array-based space-time main lobe interference resisting method for the secondary radar is applied to a ground inquiry end of the secondary radar.
Step 1: acquiring array receiving data sent by a secondary radar responder;
referring to fig. 3, in the space-time processing structure of the secondary radar interrogation terminal shown in fig. 3, there are M array elements and N time-domain taps.
The array receiving data comprises a response signal, a main lobe interference signal and a side lobe interference signal; the response signal is generated by adopting a spread spectrum technology, and the response signal is as follows: s (t) a (t) c (t) cos (2 pi f)0t); a (t) is the original information code, c (t) is the spreading code, f0Is the signal carrier frequency, s (t) is the modulated signal, t is time.
The array receive data can be expressed as:
X(t)＝AS_stS(t)+AJ_stJ(t)+N(t)
wherein A isS_stSpace-time steering vector of desired signal, AJ_stThe space-time steering vector, which is an interference signal, can be expressed in the form:
Figure BDA0003065230660000071
Figure BDA0003065230660000072
wherein the content of the first and second substances,
Figure BDA0003065230660000073
Figure BDA0003065230660000074
AS_spaceis the space-domain steering vector of the desired signal, AS_timeFor time-domain steering vectors of the desired signal, space-time steering vectors A of the desired signalS_stThe kronecker product of the space domain guide vector and the time domain guide vector is obtained; m is the number of array elements, M is 1,2, …, M, N is the number of time-domain taps, N is 1,2, …, N.
Step 2: carrying out MUSIC angle measurement on the array receiving data to obtain the azimuth information of the main lobe interference signal;
and step 3: constructing a space-time two-dimensional blocking matrix based on a circular array based on the azimuth information of the main lobe interference signal;
the space-time two-dimensional blocking matrix based on the circular array is a blocking matrix established by a main lobe interference signal under the array type, wherein a first diagonal is 1, a second diagonal comprises a plurality of unknowns, and the unknowns can be derived from space-time guide vectors of the main lobe interference.
And 4, step 4: preprocessing array receiving data by using a space-time two-dimensional blocking matrix based on a circular array, removing main lobe interference signal components, and obtaining preprocessed array receiving data which do not contain main lobe interference signals;
and 5: calculating a covariance matrix of the preprocessed array receiving data;
the covariance matrix of the preprocessed array receiving data Y is: rY＝E[YYH]。
Step 6: correcting the covariance matrix and inhibiting side lobe interference signals by using a diagonal loading and linear constraint directional diagram shape preserving method to obtain array processed signals;
and 7: carrying out de-spreading operation on the signals after the array processing to obtain information codes;
and 8: comparing the information code with the original information code, and calculating to obtain an error rate;
wherein, the response signal is a signal obtained by spreading the original information code.
The invention provides a circular array-based secondary radar space-time main lobe interference resisting method, which is characterized in that a space-time two-dimensional blocking matrix based on a circular array is constructed aiming at a received signal of a secondary radar inquiry end based on a space-time circular array model and the azimuth information of a main lobe interference signal; preprocessing array received data by utilizing a space-time two-dimensional blocking matrix to obtain preprocessed received data; inhibiting the sidelobe interference signal by using a method combining diagonal loading and linear constraint to obtain a signal after array processing; and despreading the signals after array processing by using a spreading code, comparing the signals with the original signals, and calculating to obtain the bit error rate. When high-power compression type interference exists in a main lobe of a secondary radar interrogator end, the main lobe interference can be effectively inhibited, the output signal-to-interference-and-noise ratio is improved, and the method has good stability and effectiveness.
As an optional embodiment of the present invention, step 2 includes:
step 21: calculating a covariance matrix of array received data;
step 22: performing characteristic decomposition on the covariance matrix to obtain MN characteristic values;
step 23: estimating the number of the information sources according to an MDL criterion by using the characteristic value;
step 24: under the condition that the number of the information sources is known, the orientation information of the main lobe interference signal is estimated by using the MUSIC algorithm.
Wherein, the covariance matrix of the array received data is:
Figure BDA0003065230660000081
wherein λ isi(i ═ 1,2, …, MN) is the i-th characteristic value of R, and λ1≥λ2≥…≥λK≥λK+1≥…≥λMN，λ1,…,λKIs a large eigenvalue of K disturbances, λK+1,…,λMNIs a characteristic value of noise, uiAs a characteristic value λiA corresponding feature vector. U shapeJ＝[u1,u2,…,uK]For the interference subspace, its eigenvalue matrix consists of the first K large eigenvalues, which can be expressed as ΛJ＝diag[λ1,λ2,…,λK]。UN＝[uK+1,uK+2,…,uMN]Being a noise subspace, ΛN＝diag[λK+1,λK+2,…,λMN]And the eigenvalue matrix is formed by (MN-K) small eigenvalues. To obtain lambda1,λ2,…λi,…,λMNMN characteristic values are total, and according to the MDL criterion, the number of the information sources is as follows:
Figure BDA0003065230660000091
obtaining the number of large eigenvalues, wherein L is fast beat number and lambdaiIs the ith large eigenvalue.
Under the condition that the number K of the information sources is known, MUSIC estimation is further carried out, and since all signals in the array model are not related to each other and the signal guide vector is orthogonal to the noise characteristic vector, a spatial spectrum function can be obtained:
Figure BDA0003065230660000092
wherein, theta is the azimuth angle,
Figure BDA0003065230660000093
in order to be the pitch angle,
Figure BDA0003065230660000094
is the guide vector, U, under the angle informationNIs a noise subspace obtained by feature decomposition covariance matrix. Varying azimuth theta and pitch
Figure BDA0003065230660000095
By finding waves of spatial spectral functionPeak to estimate the angle of arrival theta of the main lobe interference signal1And
Figure BDA0003065230660000096
as an optional embodiment of the present invention, step 3 includes:
step 31: setting an unsolved (MN-1) multiplied by MN dimension blocking matrix B;
step 32: construction Condition BA based on blocking matrixJ_main_stSolving the blocking matrix B to obtain a determination value of an unknown number in the blocking matrix B, wherein the determination value is 0;
wherein A isJ_main_stIs a space-time steering vector of the main lobe interference signal;
step 33: and substituting the determined value of the unknown number into the blocking matrix B to obtain a space-time two-dimensional blocking matrix.
The blocking matrix B is:
Figure BDA0003065230660000101
AJ_main_stexpressed as:
Figure BDA0003065230660000102
Figure BDA0003065230660000103
Figure BDA0003065230660000104
Figure BDA0003065230660000105
in the formula, k1＝cos(θ1-2πm/M)，k2＝cos(θ1-2 pi (M-1)/M), into the blocking matrix BAnd obtaining a space-time two-dimensional blocking matrix based on the circular array.
Order:
AJ_main_space＝[as1,…,asm,…,asM]T
AJ_main_time＝[at1,…,atn,…,atN]T
wherein, asmThe M is a steering vector of the M-th array element, and M is 1,2, … and M; a istnThe N is the steering vector of the nth tap, N is 1,2, …, N. The space-time steering vector for the main lobe interference can be written as:
AJ_main_st＝[as1at1,as1at2,…,as1atN,as2at1,as2at2,…,as2atN,…,asMat1,asMat2,…,asMatN]T
space-time steering vector A of main lobe interference signalJ_main_stSubstituting the solved space-time two-dimensional blocking matrix B into BAJ_main_stIn 0, the following formula is obtained:
Figure BDA0003065230660000111
the unfolding can result in:
Figure BDA0003065230660000112
a is tosmAnd atnSubstitution gives the following system of equations:
Figure BDA0003065230660000113
solving the equation set to obtain the variable u to be solved in the blocking matrixm,n：
Figure BDA0003065230660000121
Wherein k is1＝cos(θ1-2πm/M)，k2＝cos(θ1-2 π (M-1)/M). And substituting the obtained result into B to obtain a space-time two-dimensional blocking matrix based on the circular array.
As an optional embodiment of the present invention, step 4 includes:
and multiplying the space-time two-dimensional blocking matrix based on the circular array by the array receiving data, removing the main lobe interference signal component, and obtaining the preprocessed array receiving data which does not contain the main lobe interference signal.
The preprocessing of the array received data by the blocking matrix is as follows:
Y＝BX
wherein X (t) ═ AS_stS(t)+AJ_stJ (t) + N (t) is array received data, S (t) is expected response signal, AS_stSpace-time steering vector of expected response signal, J (t) interference signal, AJ_stThe space-time steering vector for the interference signal comprises a main lobe interference and two side lobe interferences, and N (t) is Gaussian white noise.
As an alternative embodiment of the present invention, step 6 includes:
step 61: correcting the covariance matrix by using a diagonal loading and linear constraint directional diagram shape preserving method to obtain a corrected covariance matrix;
step 62: adding zero point constraint to the position of the side lobe interference signal by using the corrected covariance matrix, and solving an optimal weight vector;
and step 63: and processing the preprocessed array received data by using the optimal weight vector to obtain a signal processed by the array.
The principle of diagonal loading is to correct the beam direction by eliminating the influence of eigenvectors corresponding to small eigenvalues in the covariance matrix, i.e. to correct the covariance matrix as follows
Figure BDA0003065230660000122
Wherein the content of the first and second substances,
Figure BDA0003065230660000131
to adjust the loading level of the loading amount, which directly affects the final effect of beamforming, it is generally required to have higher power than noise, but lower than the average power of the signal and interference. Although the diagonal loading technology can correct the beam offset of the two preprocessing algorithms, the suppression effect of the sidelobe interference can be influenced, and the sidelobe interference can be zeroed by utilizing linear constraint.
The optimization problem can be written:
Figure BDA0003065230660000132
wherein C ═ AS_st,AJ2_st,AJ3_st,…,AJK_st]Is a constraint matrix, where AJi_stIs the space-time steering vector of the ith sidelobe interference, i is 2,3, …, K, AJ1_stIs the space-time pilot vector of the main lobe interference, and the corresponding response vector g is [1,0,0, …, 0-]. Solving to obtain an optimal weight vector after diagonal loading and linear constraint:
Figure BDA0003065230660000133
using the found optimal weight vector WoptObtaining array processed signals:
Figure BDA0003065230660000134
as an alternative embodiment of the present invention, step 7 includes:
step 71: despreading the signal Z after array processing by using a spreading code c (t) to obtain an information code
Figure BDA0003065230660000135
Figure BDA0003065230660000136
Step 72: coding information
Figure BDA0003065230660000137
And comparing with the original information code a (t) to obtain the error rate.
Wherein, the output signal Z is de-spread by using the spreading code c (t) to obtain the information code
Figure BDA0003065230660000138
Figure BDA0003065230660000139
Coding information
Figure BDA00030652306600001310
And comparing with the original information code a (t) to obtain the error rate.
Theoretical performance verification is performed on the space-time two-dimensional blocking matrix of the circular array deduced in the step 3 of the invention.
In the array received data X, the received signal of the nth tap of the mth array element can be represented as:
Figure BDA0003065230660000141
the data after the blocking matrix preprocessing is Y ═ BX, and the order is:
Y＝[y11,y12,…,y1N,y21,y22,…,y2N,…,yM1,yM2,…,yM(N-1)]T
wherein:
Figure BDA0003065230660000142
the above formula is developed:
Figure BDA0003065230660000143
wherein s is1For the main lobe interference signal, let:
Figure BDA0003065230660000144
wherein liIs the i-th signal s after preprocessingiBy a factor of ymnThe expression is obtained:
Figure BDA0003065230660000145
will k1＝cos(θ1-2πm/M)，k2＝cos(θ1Substitution of-2 π (M-1)/M) into the above formula, it can be seen that: when i is 1, siFor main lobe interference, coefficient l i0, i.e. y after pretreatmentmnAnd the middle main lobe interference component is suppressed, so that the effectiveness of the pushed space-time two-dimensional blocking matrix in suppressing the main lobe interference signal is verified.
The imaging effect of the main lobe interference resisting method provided by the invention is explained by simulation and the result thereof as follows:
simulation experiment I:
1. simulation conditions
Assuming that the frequency offset of the target signal is 0Hz, the azimuth angle is 45 degrees, the frequency offset of the main lobe interference signal is 0.02MHz, and the azimuth angle is 45.5 degrees.
2. Content of the experiment
And carrying out simulation analysis on the theoretical verification of the space-time two-dimensional blocking matrix. Observing the theoretical verification part of the two-dimensional blocking matrix in the hollow time in the embodiment by changing the angle and the frequency offset, preprocessing the signal siCoefficient of (a)iThe results of the change are shown in fig. 4a and 4 b.
FIG. 4a and FIG. 4b depict the pre-processed signal coefficients liWith respect to signal frequency offset and angle. The relationship graph shows that: at frequencyCoefficient l of the signal after preprocessing when the rate offset and the angle are the same as the main lobe interferenceiAnd 0, verifying that the preprocessed array received data does not contain the main lobe interference signal. Therefore, the effectiveness of the two-dimensional blocking matrix in suppressing the main lobe interference during the air space is verified.
And (2) simulation experiment II:
1. simulation conditions
The airspace of the space-time array model adopts a uniform circular array with 16 array elements and the radius of 2m, and the pitch angles of the array receiving target and the interference signal are assumed to be 85 degrees; the time domain of the space-time model adopts 10 taps; the target signal is response signal of secondary radar, and is spread spectrum signal of WALSH code with information code length of 16 and spread spectrum sequence length of 8, and center frequency f0At 1090MHz, the angle of incidence is at 45 ° azimuth. The array received data comprises a target response signal and three interference signals, the offsets of the central frequency and the target signal are (-0.01MHz,0MHz and 0.2MHz), and the incident angles are (45 degrees, 20 degrees and 70 degrees); INRs are all 40 dB; the SNR range of the array input is taken as (-20dB,20 dB); the number of monte carlo experiments was 200.
2. Content of the experiment
The method provided by the patent carries out simulation analysis on the variation of the output signal-to-interference-and-noise ratio and the bit error rate along with the signal-to-noise ratio. By varying the input signal-to-noise ratio under a fixed dry-to-noise ratio, the variation curves shown in fig. 5a and 5b can be obtained.
Fig. 5a and 5b depict the variation of the output signal-to-interference-and-noise ratio and the variation of the bit error rate with the signal-to-noise ratio, respectively. Simulation shows that: the output signal-to-interference-and-noise ratio of the interference method of the invention is increased along with the increase of the signal-to-noise ratio, and the error rate is reduced along with the increase of the signal-to-noise ratio.
And (3) simulation experiment III:
1. simulation conditions
The airspace of the space-time array model adopts a uniform circular array with 16 array elements and the radius of 2m, and the pitch angles of the array receiving target and the interference signal are assumed to be 85 degrees; the time domain of the space-time model adopts 10 taps; the target signal is a response signal of a secondary radar, and the WALSH code with the information code length of 16 and the spreading sequence length of 8 is adoptedSpread spectrum signal, center frequency f0At 1090MHz, the angle of incidence is at 45 ° azimuth. The array received data comprises a target response signal and a main lobe interference signal, the input INR is 40dB, the input SNR is 0dB, the frequency offset range of the interference signal and the target signal is (-0.044MHz,0.044MHz), the angle range of the interference signal is (42.4 degrees, 47.6 degrees), and the frequency offset range and the angle range are both in the main lobe range.
2. Content of the experiment
The method provided by the patent carries out simulation analysis on the variation of the output signal-to-interference-and-noise ratio and the bit error rate along with the frequency offset and the angle of the interference signal. By simultaneously changing the frequency offset and angle of the interference signal within the above range, the variation of the output signal to interference plus noise ratio and the error rate are observed, as shown in fig. 6a and 6 b.
Fig. 6a and 6b depict the trend of the output signal-to-interference-and-noise ratio and the error rate along with the simultaneous change of the interference frequency offset and the angle, respectively. Simulation shows that: when the interference signal approaches to the expected response signal from the angle and the frequency at the same time, the output signal-to-interference-and-noise ratio of the algorithm is reduced, and the error rate is increased.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (8)

1. A space-time main lobe interference resisting method for a secondary radar based on a circular array is applied to a ground inquiry end of the secondary radar, and is characterized by comprising the following steps:
step 1: acquiring array receiving data sent by a secondary radar responder;
wherein the array received data comprises an acknowledgement signal, a main lobe interference signal and a side lobe interference signal;
step 2: carrying out MUSIC angle measurement on the array receiving data to obtain the azimuth information of the main lobe interference signal;
and step 3: constructing a space-time two-dimensional blocking matrix based on a circular array based on the azimuth information of the main lobe interference signal;
and 4, step 4: preprocessing the array receiving data by using the space-time two-dimensional blocking matrix based on the circular array, removing the main lobe interference signal component, and obtaining the preprocessed array receiving data which does not contain the main lobe interference signal;
and 5: calculating a covariance matrix of the preprocessed array receiving data;
step 6: correcting the covariance matrix and inhibiting side lobe interference signals by using a diagonal loading and linear constraint directional diagram shape preserving method to obtain array processed signals;
and 7: performing despreading operation on the signals after the array processing to obtain information codes;
and 8: comparing the information code with the original information code, and calculating to obtain an error rate;
the response signal is a signal obtained by spreading an original information code.
2. A secondary radar space-time mainlobe interference method according to claim 1, wherein the response signal is a response signal generated by using a spread spectrum technique, and the response signal is:
s(t)＝a(t)c(t)cos(2πf0t)；
wherein a (t) is original information code, c (t) is spreading code, f0Is the signal carrier frequency, s (t) is the modulated signal, t is time.
3. The quadric radar space-time mainlobe interference method according to claim 2, wherein the step 2 comprises:
step 21: calculating a covariance matrix of the array received data;
step 22: performing characteristic decomposition on the covariance matrix to obtain MN characteristic values;
step 23: estimating the number of the information sources according to an MDL criterion by using the characteristic value;
step 24: and under the condition that the number of the information sources is known, estimating azimuth information of the main lobe interference signal by using a MUSIC algorithm.
4. The circular array-based quadratic radar space-time main lobe interference resisting method according to claim 2, wherein the step 3 comprises:
step 31: setting an unsolved (MN-1) multiplied by MN dimension blocking matrix B;
step 32: construction Condition BA based on blocking matrixJ_main_stSolving the blocking matrix B to obtain a determination value of an unknown number in the blocking matrix B, wherein the determination value is 0;
wherein A isJ_main_stIs a space-time steering vector of the main lobe interference signal;
step 33: and substituting the determined value of the unknown number into the blocking matrix B to obtain a space-time two-dimensional blocking matrix.
5. The circular array-based quadratic radar space-time main lobe interference resisting method according to claim 4,
the blocking matrix B is:
Figure FDA0003065230650000031
AJ_main_stexpressed as:
Figure FDA0003065230650000032
Figure FDA0003065230650000033
Figure FDA0003065230650000034
Figure FDA0003065230650000035
in the formula, k1＝cos(θ1-2πm/M)，k2＝cos(θ1And-2 pi (M-1)/M) is substituted into the blocking matrix B to obtain a space-time two-dimensional blocking matrix based on the circular matrix.
6. The circular array-based quadratic radar space-time main lobe interference resisting method according to claim 1, wherein the step 4 comprises:
and multiplying the space-time two-dimensional blocking matrix based on the circular array by the array receiving data, removing the main lobe interference signal component, and obtaining the array receiving data which does not contain the main lobe interference signal and is preprocessed.
7. The circular array-based quadratic radar space-time main lobe interference resisting method according to claim 1, wherein the step 6 comprises:
step 61: correcting the covariance matrix by utilizing a diagonal loading and linear constraint directional diagram shape preserving method to obtain a corrected covariance matrix;
step 62: adding zero point constraint to the position of the side lobe interference signal by using the corrected covariance matrix, and solving an optimal weight vector;
and step 63: and processing the preprocessed array received data by using the optimal weight vector to obtain a signal processed by the array.
8. The circular array-based quadratic radar space-time main lobe interference resisting method according to claim 1, wherein the step 7 comprises:
step 71: despreading the signal Z after array processing by using a spreading code c (t) to obtain an information code
Figure FDA0003065230650000041
Figure FDA0003065230650000042
Step 72: coding information
Figure FDA0003065230650000043
And comparing with the original information code a (t) to obtain the error rate.
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