Simultaneous anti-suppressing interference foresight imaging method for missile-borne foresight array radar

Abstract

The invention discloses a simultaneous anti-suppressing interference foresight imaging method for a missile-borne foresight array radar, and the method comprises the steps: receiving foresight region echoes through employing an array antenna in a track cutting direction, and carrying out the sampling, and obtaining distance-pulse-array three-dimensional echo data; performing range-direction pulse compression on the three-dimensional echo data, and multiplying a pulse compression reference function and a migration correction factor in a frequency domain to realize range-direction high resolution; receiving data of multiple channels of each distance-pulse unit are selected and arranged in sequence to form an airspace snapshot corresponding to the unit; establishing a covariance matrix of interference and noise, and approximately solving the maximum likelihood estimation values of the target angle and amplitude in the interference environment for the airspace snapshot signal of each distance-pulse unit after the distance pulse compression by using an adaptive monopulse algorithm; and projecting an angle measurement result to a distance-azimuth domain, and performing space coordinate conversion to obtain a two-dimensional foresight imaging picture. According to the invention, the main lobe suppressing interference is effectively suppressed, and the high-resolution imaging of the foresight target is realized.

Description

[0001] Methodology Area

[0002] The invention belongs to the field of radar imaging technology, relates to an airborne radar forward-looking imaging signal processing technology, and specifically relates to a simultaneous anti-suppression interference forward-looking imaging method for a missile-borne forward-looking array radar. Background Art

[0003] Radar imaging technology is an important milestone in the history of radar development. Through advanced signal processing methods, it can obtain high-resolution two-dimensional images of the detection area, greatly expanding the functions of modern radar systems. From a mathematical point of view, radar imaging is essentially a typical inverse problem, that is, the problem of inverting the high-resolution ground scene through limited observation data (echo signal). Through high-resolution imaging processing, the missile-borne radar system can obtain the topography of the strike area, sea surface features, and the size and shape characteristics of the target, thereby improving the strike accuracy and combat efficiency. However, in the terminal guidance stage of existing precision weapons, especially when the distance to the strike target is within 5 kilometers, the radar system cannot use the synthetic aperture radar (SAR) mode to obtain high-resolution images of the target in front, and can only lock the target by single pulse tracking. When the strike target is located in a formation, or when false targets and interference exist, this working mode often cannot meet the requirements of precision guidance. When the missile is in the forward-looking working mode of three-dimensional acceleration in the terminal guidance stage, high-resolution imaging of the forward strike area is one of the essential functions of modern missile-borne radar systems.

[0004] Compared with traditional single-channel radar, array radar super-resolution imaging technology is based on an array receiving system and uses super-resolution algorithms to achieve high-resolution forward-looking imaging of missile-borne radar. This technology can obtain an angular resolution far beyond the real aperture beam width and separate multiple targets within the beam. In recent years, as a new technical means for airborne radar forward-looking imaging, super-resolution technology has gradually been recognized and valued by relevant research institutions. It is one of the simple and efficient means to solve the problem of airborne radar forward-looking imaging in the future.

[0005] However, today's electromagnetic environment is becoming increasingly complex, and main lobe suppression interference will cause the performance of existing forward-looking imaging algorithms to seriously degrade, affecting the strike effect of attack weapons. How to image the forward-looking area of ​​​​the missile-borne radar under this interference scenario is an urgent problem to be solved in the field of forward-looking imaging. Summary of the invention

[0006] Purpose of the invention: The present invention provides a method for simultaneously resisting suppression interference forward-looking imaging for missile-borne forward-looking array radar, so that the radar can achieve high-resolution imaging of forward-looking targets while effectively suppressing main lobe suppression interference.

[0007] Technical solution: The present invention discloses a method for simultaneously resisting suppression interference forward-looking imaging for missile-borne forward-looking array radar, comprising the following steps:

[0008] (1) The missile-borne radar works in scanning mode, using an array antenna in the direction of the track to receive echoes from the forward-looking area and sampling to obtain three-dimensional echo data of range-pulse-array;

[0009] (2) Pulse compression is performed on the three-dimensional echo data of the array radar in the range direction, and the pulse compression reference function and the migration correction factor are multiplied in the frequency domain to achieve high resolution in the range direction;

[0010] (3) selecting the multi-channel received data of each range-pulse unit and arranging them in sequence to form a spatial snapshot corresponding to the unit;

[0011] (4) Establish the covariance matrix of main lobe interference and noise under missile forward-looking conditions, perform azimuth imaging processing on the data after range pulse compression for each range gate, construct the corresponding spatial snapshot signal for each range-pulse unit, establish the maximum likelihood function, and then use the adaptive single pulse algorithm to solve the maximum likelihood target estimation value of the target angle and amplitude under the interference environment;

[0012] (5) Each spatial snapshot of the range-pulse unit in the echo data is projected onto a two-dimensional preset grid in the range-azimuth domain through the target estimation value, and a two-dimensional forward-looking image is obtained through spatial coordinate conversion.

[0013] Furthermore, the implementation process of step (1) is as follows:

[0014] A horizontal array antenna along the track direction is used to synthesize multiple receiving channels through sub-arrays to receive the echo of the forward-looking area of ​​the missile-borne radar; the radar works in scanning mode, and a linear frequency modulation pulse LFM is emitted every pulse repetition interval PRI. After the beam is scanned once, the echo is sampled to obtain the distance-pulse-channel three-dimensional echo data of the forward-looking area of ​​the missile-borne radar.

[0015] Furthermore, the sampling in step (1) to obtain the range-pulse-array three-dimensional echo data is implemented as follows:

[0016] After one round of beam scanning, the specific form of the echo obtained from the entire imaging scanning process about a single point target is:

[0017]

[0018] Among them, h(tt p ) represents the two-way antenna pattern in azimuth, which varies with the slow time variable t and represents the modulation effect in azimuth, t p represents the time when the center of the antenna beam scans to the point target P; τ0(t) is the propagation delay of the transmitted signal after it reaches the target P and is reflected by the target P to the mth channel, d mrepresents the distance between the mth receiving channel and the reference array element, then the delay τ0(t) is:

[0019]

[0020] Where c is the speed of light. After down-conversion, the range-azimuth two-dimensional echo of the mth receiving channel is expressed as:

[0021]

[0022] The echo is sampled to obtain the range-pulse-channel three-dimensional echo data of the missile-borne radar forward-looking area.

[0023] Furthermore, the implementation process of step (2) is as follows:

[0024] After performing range FFT on the echo of each channel after down-conversion, we get:

[0025]

[0026] Where B is the signal bandwidth, f r is the distance frequency domain variable; multiply it by the following pulse compression reference function in the frequency domain:

[0027]

[0028] get:

[0029]

[0030] Perform range migration correction on the echo and multiply it by the following phase factor in the range frequency domain to eliminate the influence of platform motion:

[0031]

[0032] After pulse compression and migration correction in the range direction, high-resolution imaging in the range direction is achieved.

[0033] Furthermore, the implementation process of step (3) is as follows:

[0034] The entire imaging area is divided into L distance units and K azimuth angle units. For a certain distance unit, the K×1-dimensional source signal vector composed of the backscattering coefficients of the scattering points in the distance unit is expressed as x=[σ1,…,σ K ] T , σ k represents the backscattering coefficient of the kth scattering point, k = 1, 2, ..., K; at a specific moment in time, the beam center points to the azimuth angle θ k When the sampling of all channel echoes is performed, that is, a certain spatial snapshot is expressed as s = [s1, s2, ..., sM ]; by θ k The M×1-dimensional spatial guidance vector a is composed of the phase difference of the target reaching the horizontal linear array s (θ k ) is expressed as:

[0035]

[0036] Where M is the number of channels, d is the channel spacing, and λ is the wavelength. is the viewing angle under the radar beam;

[0037] The spatial snapshot is represented in the following matrix form:

[0038] s=Ax+N

[0039] Among them, A is the M×K dimensional spatial guidance vector matrix, N is the M×1 dimensional observation noise vector, which are expressed as:

[0040]

[0041] N=[n1,…,n M ] T .

[0042] Furthermore, the implementation process of step (4) is as follows:

[0043] The covariance matrix R of interference and noise is established by using the statistical characteristics of interference superposition noise, and then the spatial snapshot data of each range-pulse unit is selected for azimuth imaging processing; the maximum likelihood function P(θ)=|w H s| 2 , where w = (a s H R -1 a s ) -1 / 2 R -1 a s is the adaptive beam weight vector, s is the spatial snapshot signal, and the value of θ that maximizes P(θ) is the maximum likelihood estimate.

[0044] Approximately solve the likelihood function, let F(θ) = ln[P(θ)], and the estimated value of the expected target is The solution of the log-likelihood function F(θ) is given by Newton's gradient method:

[0045] θ max =θ0-F θθ -1 (θ max )F θ (θ)

[0046] In the formula, Fθ (θ) is the first-order derivative of F(θ), F θθ (θ) is the second-order derivative of F(θ), and θ0 is the beam center of the current range-pulse unit antenna pattern in azimuth. Calculate the first-order derivative and second-order derivative of F(θ) and substitute them into the above formula to obtain:

[0047]

[0048] in:

[0049]

[0050] The above formula is used to obtain the angle and amplitude information of the real target under the main lobe interference condition. In the presence of external interference, the correction coefficient in the adaptive single pulse algorithm compensates for the error, thereby obtaining the correct arrival direction estimation result.

[0051] Furthermore, the implementation process of step (4) is as follows:

[0052] The target estimation value corresponding to each range-pulse unit is projected onto a preset grid matrix in the range-azimuth domain according to the range gate, current beam center and azimuth angle. The data stored after projection is converted into spatial coordinates and displayed to obtain the imaging result of the forward-looking area.

[0053] Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention takes into account the inevitable noise suppression interference during forward-looking imaging of missile-borne radar, utilizes the statistical characteristics of interference and noise, and establishes a likelihood function and solves it on the basis of establishing an interference and noise covariance matrix to obtain the maximum likelihood estimate of the target amplitude, and combines Newton's formula to complete angle estimation through an adaptive single pulse, thereby avoiding traversal search of all possible azimuths and reducing the amount of calculation; the method is based on missile-borne array radar, and can obtain better angle measurement accuracy while effectively suppressing main lobe suppression interference, thereby achieving high-resolution imaging of forward-looking targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a flow chart of the present invention;

[0055] Figure 2 It is a schematic diagram of the geometric model of the missile-borne array radar forward-looking imaging;

[0056] Figure 3 It is a simplified schematic diagram of two-dimensional data collection;

[0057] Figure 4 It is a schematic diagram of spectrum incoherent accumulation;

[0058] Figure 5 This is a schematic diagram of a point target simulation scenario;

[0059] Figure 6 is the real beam imaging result of point target;

[0060] Figure 7 Simultaneously resist suppression and interference of forward-looking imaging results for point targets;

[0061] Figure 8 Forward-looking imaging profile for point targets while resisting suppression interference;

[0062] Fig. 9 It is a schematic diagram of a ship model composed of a dot matrix;

[0063] Fig.10 The imaging results with a signal-to-interference ratio of -20dB are obtained using the maximum likelihood estimation algorithm; (a) is the real beam imaging result diagram, and (b) is the forward-looking imaging result with simultaneous anti-suppression interference.

[0064] Fig.11 The imaging results of the signal-to-interference ratio of -10dB using the maximum likelihood estimation algorithm; (a) is the real beam imaging result diagram, and (b) is the forward-looking imaging result of simultaneous anti-suppression interference;

[0065] Fig.12 The imaging results with a signal-to-interference ratio of -5dB are obtained using the maximum likelihood estimation algorithm; (a) is the real beam imaging result diagram, and (b) is the forward-looking imaging result with simultaneous anti-suppression interference;

[0066] Fig.13 The imaging result with signal-to-interference ratio of 0dB is obtained by using the maximum likelihood estimation algorithm; (a) is the real beam imaging result, and (b) is the forward-looking imaging result with simultaneous anti-suppression interference.

[0067] Fig.14 The imaging results of the signal-to-interference ratio of 5dB using the maximum likelihood estimation algorithm; (a) is the real beam imaging result diagram, and (b) is the forward-looking imaging result of simultaneous anti-suppression interference;

[0068] Fig.15 The imaging results with a signal-to-interference ratio of 10dB are obtained using the maximum likelihood estimation algorithm; (a) is the real beam imaging result, and (b) is the forward-looking imaging result with simultaneous anti-suppression interference. DETAILED DESCRIPTION

[0069] The present invention is further described in detail below with reference to the accompanying drawings.

[0070] like Figure 1 As shown, the present invention provides a simultaneous anti-suppression interference forward-looking imaging method for missile-borne forward-looking array radar, which specifically includes the following steps:

[0071] Step 1: The missile-borne radar works in scanning mode, using an array antenna in the direction of the track to receive echoes from the forward-looking area, and sampling to obtain three-dimensional echo data of range-pulse-array.

[0072] like Figure 2 As shown in the figure, the missile-borne radar adopts a horizontal array antenna along the tangent track direction, and receives the echo of the forward-looking area of ​​the missile-borne radar through the sub-array synthesis of M receiving channels. The forward-looking area generally considers the ±10° area in front of the missile flight direction; the radar works in the downward scanning mode, and transmits a linear frequency modulation pulse (LFM) every pulse repetition interval (PRI). Its time domain expression is:

[0073]

[0074] Among them, τ is the distance-to-fast time domain variable, f c is the carrier frequency of the radar transmitting signal, K r is the linear modulation frequency in the distance direction, T p is the pulse width of the signal, rect[·] represents the rectangular window function, that is:

[0075]

[0076] Assume that t is a slow time domain variable in azimuth, which is related to radar motion and antenna scanning. For a point target P in the imaging area, assume that its position coordinates at time t = 0 are (R0, θ0), and the scattering coefficient is σ0. is the downward viewing angle of the radar beam, which is a constant. At any time t, the instantaneous slant range R(t) between the reference element of the radar array antenna and the target P is approximately expressed as:

[0077]

[0078] Where v is the velocity of the missile-borne radar. For the mth receiving channel of the multi-channel radar, m = 1, 2, ..., M, the specific form of the echo obtained by the entire imaging scanning process about a single point target after one round of beam scanning is:

[0079]

[0080] Among them, h(tt p ) represents the two-way antenna pattern in azimuth, which varies with the slow time variable t and represents the modulation effect in azimuth, t p represents the time when the center of the antenna beam scans to the point target P; τ0(t) is the propagation delay of the transmitted signal after it reaches the target P and is reflected by the target P to the mth channel, d m represents the distance between the mth receiving channel and the reference array element, then the delay τ0(t) is:

[0081]

[0082] Where c is the speed of light.

[0083] After down-conversion processing, the range-azimuth two-dimensional echo of the mth receiving channel is expressed as:

[0084]

[0085] By sampling the echo, the three-dimensional echo data of range-pulse-channel in the forward-looking area of ​​the missile-borne radar can be obtained.

[0086] Step 2: Perform pulse compression and motion correction on the three-dimensional echo data of the array radar in the range direction to achieve high resolution in the range direction.

[0087] The three-dimensional echo data of the array radar is pulse compressed and corrected in the range direction, and the pulse compression reference function and the migration correction factor are multiplied in the frequency domain to achieve high resolution in the range direction. Then the multi-channel receiving data of each range-pulse unit is selected and arranged in sequence to form the corresponding spatial snapshot of the unit.

[0088] After performing range FFT on the echo of each channel after down-conversion, we get:

[0089]

[0090] Where B is the signal bandwidth, f r is the frequency domain variable in the distance direction. Multiply it by the following pulse compression reference function in the frequency domain:

[0091]

[0092] get:

[0093]

[0094] Due to its high-speed movement, missile-borne radar has range migration with the target, which not only brings Doppler frequency shift, but also causes coupling in the range and azimuth. In order to solve the coupling, the echo needs to be corrected for range migration. Therefore, the following phase factor is multiplied in the range frequency domain to eliminate the influence of platform movement:

[0095]

[0096] After pulse compression and motion correction in the range direction, high-resolution imaging in the range direction has been achieved.

[0097] Step 3: In order to perform high-resolution imaging processing in azimuth, a multi-channel signal echo model is constructed.

[0098] First, the forward-looking area is grid-divided in the azimuth direction. Assume that the entire imaging area is divided into L range units and K azimuth angle units. The slant ranges of the targets on the lth range gate and the kth azimuth angle unit are represented by R l and θ k It means that the scattering coefficient σ(R l ,θ k ) represents. For a certain distance unit, the beam center points to the azimuth angle θ at a specific moment in the azimuth. k When the backscattering coefficients of the scattering points in the distance unit are composed of K×1-dimensional source signal vectors, they can be expressed as x=[σ1,…,σ K ] T The sampling of all channel echoes, that is, a spatial snapshot, is represented by s = [s1, s2, ..., s M ]. By θ k The M×1-dimensional spatial guidance vector a is composed of the phase difference of the target reaching the horizontal linear array s (θ k ) is expressed as:

[0099]

[0100] Where d is the channel spacing and λ is the wavelength.

[0101] Then, this spatial snapshot can be expressed in the following matrix form:

[0102] s=Ax+N

[0103] Among them, A is the M×K dimensional spatial guidance vector matrix, N is the M×1 dimensional observation noise vector, which are expressed as:

[0104]

[0105] N=[n1,…,n M ] T .

[0106] Step 4: Establish the covariance matrix of the main lobe interference and noise under the missile-borne forward-looking condition, perform azimuth imaging processing on the data after range pulse compression for each range gate, construct the corresponding spatial snapshot signal for each range-pulse unit, establish the maximum likelihood function, and then use the adaptive single pulse algorithm to solve the maximum likelihood estimation of the target angle and amplitude under the interference environment.

[0107] The maximum likelihood estimation obtains the estimated value of the arrival angle by establishing the following likelihood function and solving it:

[0108]

[0109] The exponent part is recorded as:

[0110] U(σ,θ)=(s-σa s ) H R -1 (s-σa s )

[0111] Taking the partial derivative of U(σ,θ) with respect to σ and setting it equal to zero, the maximum likelihood estimate of σ is:

[0112]

[0113] Substituting it into U(σ,θ), we can get:

[0114] U(σ,θ)=s H R -1 s+|w H s| 2

[0115] Define the adaptation and beam weight vectors:

[0116] w=(a s H R -1 a s ) -1 / 2 R -1 a s

[0117] Let P(θ)=|w H s| 2 , since the previous term is a constant term independent of θ, the value of θ that maximizes P(θ) is its maximum likelihood estimate because There is no analytical expression, so in actual processing, it is necessary to search all possible directions to find the direction that maximizes P(θ). Next, the likelihood function is solved by the adaptive single pulse algorithm, and F(θ) = ln[P(θ)], then the estimated value of the desired target is The solution of the log-likelihood function F(θ) is given by Newton's gradient method:

[0118] θ max =θ0-F θθ -1 (θ max )F θ (θ)

[0119] In the formula, F θ (θ) is the first-order derivative of F(θ), F θθ (θ) is the second-order derivative of F(θ), and θ0 is the beam center of the current range-pulse unit antenna pattern in azimuth. Calculating the first-order and second-order derivatives of F(θ) and substituting them into the above formula yields:

[0120]

[0121] in:

[0122]

[0123] The above formula can be used to obtain the angle and amplitude information of the real target under the main lobe interference condition. In the presence of external interference, the correction coefficient in the adaptive single pulse algorithm compensates for the error, thereby obtaining the correct arrival direction estimation result.

[0124] Step 5: Project the target estimation value obtained by step 4 for each range-pulse unit spatial snapshot in the echo data onto a two-dimensional preset grid in the range-azimuth domain, and obtain a two-dimensional forward-looking image through spatial coordinate conversion.

[0125] The target estimation value corresponding to each range-pulse unit obtained in step 4 is projected into the preset grid matrix in the range-azimuth domain according to the range gate, the current beam center and the azimuth angle. The spatial coordinate conversion and display of the projected stored data can obtain the forward-looking area imaging result, such as Figure 3 and Figure 4 shown.

[0126] The point target simulation and ship surface target simulation verification are carried out below. Figure 5 This is a schematic diagram of a point target simulation scenario. A point target and a suppressive interference are set within the beam main lobe width. The interference is located directly in front of the missile's flight trajectory, and the target deviates from the interference by 1 degree. Figure 6 and Figure 7 The processing results of the forward-looking simulated echo data of the point target in the main lobe interference scenario are given respectively. The real beam imaging results of the forward-looking scenario are shown in Figure 6 As shown in the figure. In the presence of main lobe interference, the target cannot be imaged, which seriously affects the missile's precision strike performance. Afterwards, the array adaptive maximum likelihood estimation method is used to image the forward-looking area. The results are shown in the figure. Figure 7 When the array is subject to noise suppression interference, this method uses the maximum likelihood method to accurately estimate the target's arrival direction and amplitude, suppressing the noise. For the convenience of comparison, the profile of real beam imaging and adaptive single pulse imaging is shown in Figure 8 It can be seen that the proposed new missile-borne array radar forward-looking imaging algorithm has the ability to resist the suppressive interference in the strike area during terminal guidance, enabling the radar to have the ability to image the forward-looking area under the condition of suppressive interference.

[0127] Next, we will conduct ship surface target simulation verification. Fig. 9 The ship model is composed of dot matrix; Figures 10 to 15The processing results of the forward-looking simulation echo data of the ship model under different signal-to-interference ratio conditions using the maximum likelihood estimation algorithm are given. This method realizes the angle estimation of the target under the interference background. Finally, the forward-looking image after suppressing the noise suppression interference can be obtained through the incoherent accumulation of the target estimation value, and the outline of the ship is clearly visible.

[0128] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A method for simultaneously resisting suppression interference forward-looking imaging for missile-borne forward-looking array radar, characterized in that: The following steps are involved: (1) The missile-borne radar works in scanning mode, using an array antenna in the direction of the track to receive echoes from the forward-looking area and sampling to obtain three-dimensional echo data of range-pulse-array; (2) Pulse compression is performed on the three-dimensional echo data of the array radar in the range direction, and the pulse compression reference function and the migration correction factor are multiplied in the frequency domain to achieve high resolution in the range direction; (3) selecting the multi-channel received data of each range-pulse unit and arranging them in sequence to form a spatial snapshot corresponding to the unit; (4) Establish the covariance matrix of main lobe interference and noise under missile forward-looking conditions, perform azimuth imaging processing on the data after range pulse compression for each range gate, construct the corresponding spatial snapshot signal for each range-pulse unit, establish the maximum likelihood function, and then use the adaptive single pulse algorithm to solve the maximum likelihood target estimation value of the target angle and amplitude under the interference environment; (5) Each spatial snapshot of the range-pulse unit in the echo data is projected onto a two-dimensional preset grid in the range-azimuth domain through the target estimation value, and a two-dimensional forward-looking image is obtained through spatial coordinate conversion.

2. The method for simultaneous anti-suppression interference forward-looking imaging for missile-borne forward-looking array radar according to claim 1, characterized in that: The implementation process of step (1) is as follows: A horizontal array antenna along the track direction is used to synthesize multiple receiving channels through sub-arrays to receive the echo of the forward-looking area of ​​the missile-borne radar; the radar works in scanning mode, and a linear frequency modulation pulse LFM is emitted every pulse repetition interval PRI. After the beam is scanned once, the echo is sampled to obtain the distance-pulse-channel three-dimensional echo data of the forward-looking area of ​​the missile-borne radar.

3. The method for simultaneous anti-suppression interference forward-looking imaging for missile-borne forward-looking array radar according to claim 1, characterized in that: The process of obtaining the range-pulse-array three-dimensional echo data by sampling in step (1) is as follows: After one round of beam scanning, the specific form of the echo obtained from the entire imaging scanning process about a single point target is: Among them, h(tt p ) represents the two-way antenna pattern in azimuth, which varies with the slow time variable t and represents the modulation effect in azimuth, t p represents the time when the center of the antenna beam scans to the point target P; τ0(t) is the propagation delay of the transmitted signal after it reaches the target P and is reflected by the target P to the mth channel, d m represents the distance between the mth receiving channel and the reference array element, then the delay τ0(t) is: Where c is the speed of light. After down-conversion, the range-azimuth two-dimensional echo of the mth receiving channel is expressed as: The echo is sampled to obtain the range-pulse-channel three-dimensional echo data of the missile-borne radar forward-looking area.

4. The method for simultaneous anti-suppression interference forward-looking imaging for missile-borne forward-looking array radar according to claim 1, characterized in that: The implementation process of step (2) is as follows: After performing range FFT on the echo of each channel after down-conversion, we get: Where B is the signal bandwidth, f r is the distance frequency domain variable; multiply it by the following pulse compression reference function in the frequency domain: get: Perform range migration correction on the echo and multiply it by the following phase factor in the range frequency domain to eliminate the influence of platform motion: After pulse compression and migration correction in the range direction, high-resolution imaging in the range direction is achieved.

5. The method for simultaneous anti-suppression interference forward-looking imaging for missile-borne forward-looking array radar according to claim 1, characterized in that: The implementation process of step (3) is as follows: The entire imaging area is divided into L distance units and K azimuth angle units. For a certain distance unit, the K×1-dimensional source signal vector composed of the backscattering coefficients of the scattering points in the distance unit is expressed as x=[σ1,…,σ K ] T , σ k represents the backscattering coefficient of the kth scattering point, k = 1, 2, ..., K; At a specific moment in azimuth, the center of the beam points to the azimuth angle θ k When the sampling of all channel echoes is performed, that is, a certain spatial snapshot is expressed as s = [s1, s2, ..., s M ]; by θ k The M×1-dimensional spatial guidance vector a is composed of the phase difference of the target reaching the horizontal linear array s (θ k ) is expressed as: Where M is the number of channels, d is the channel spacing, and λ is the wavelength. is the viewing angle under the radar beam; The spatial snapshot is represented in the following matrix form: s=Ax+N Among them, A is the M×K dimensional spatial guidance vector matrix, N is the M×1 dimensional observation noise vector, which are expressed as: N=[n1,…,n M ] T 。 6. The method for simultaneous anti-suppression interference forward-looking imaging for missile-borne forward-looking array radar according to claim 1, characterized in that: The implementation process of step (4) is as follows: The covariance matrix R of interference and noise is established by using the statistical characteristics of interference superposition noise, and then the spatial snapshot data of each range-pulse unit is selected for azimuth imaging processing; Construct the maximum likelihood function P(θ) = |w H s| 2 , where w = (a s H R -1 a s ) -1 / 2 R -1 a s is the adaptive beam weight vector, s is the spatial snapshot signal, and the value of θ that maximizes P(θ) is the maximum likelihood estimate. Approximately solve the likelihood function, let F(θ) = ln[P(θ)], and the estimated value of the expected target is The solution of the log-likelihood function F(θ) is given by Newton's gradient method: i max =θ0-F θθ 1 (i max )F θ (i) In the formula, F θ (θ) is the first-order derivative of F(θ), F θθ (θ) is the second-order derivative of F(θ), and θ0 is the beam center of the current range-pulse unit antenna pattern in azimuth. Calculate the first-order derivative and second-order derivative of F(θ) and substitute them into the above formula to obtain: in: The above formula is used to obtain the angle and amplitude information of the real target under the main lobe interference condition. In the presence of external interference, the correction coefficient in the adaptive single pulse algorithm compensates for the error, thereby obtaining the correct arrival direction estimation result.

7. The method for simultaneous anti-suppression interference forward-looking imaging for missile-borne forward-looking array radar according to claim 1, characterized in that: The implementation process of step (4) is as follows: The target estimation value corresponding to each range-pulse unit is projected onto the preset grid matrix in the range-azimuth domain according to the range gate, current beam center and azimuth angle. The data stored after projection is converted into spatial coordinates and displayed to obtain the imaging result of the forward-looking area.

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