ADMF-based target long-time accumulation method and system under FDA radar area array system

Abstract

The invention discloses a target long-time accumulation method based on ADMF (Amplitude Dimethyl Formamide) under an FDA (Frequency Division Amplification) radar area array system, which mainly solves the problem of insufficient target detection capability caused by weak received target echo energy and low signal-to-noise ratio of received signals when the existing FDA system radar realizes wide-coverage wide-area target monitoring. According to the implementation scheme, the method comprises the following steps: establishing an area array echo model combined with an azimuth-dimension FDA and a pitch-dimension phased array; constructing a time-angle two-dimensional matched filter under a plane array system in which the azimuth FDA and the pitching phased array are combined, and performing matched filtering on echo signals; performing first-order KT conversion and Doppler fuzzy compensation on the echo signal after matched filtering to realize range walk correction; and carrying out distance dimension IFFT and slow time dimension FFT on the corrected signal to obtain a signal after phase-coherent accumulation. Through long-time coherent accumulation of the target, the echo energy of the FDA radar target can be improved, the signal-to-noise ratio can be reduced, the target detection probability can be improved, and the method can be used for detecting a weak high-speed moving target.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and further relates to a target long-term accumulation method and system for a time-angle two-dimensional matched filter (ADMF), which can be used for weak target detection in a planar array system combining an azimuth frequency diversity array (FDA) and an elevation phased array. Background Art

[0002] There are many types of pulse radars at present, including traditional phased array radars and frequency diversity array FDA radars. Among them, the traditional phased array radar has the same carrier frequency for each array element, and the main lobe coverage of the transmission pattern is limited. The probability of target detection in the main lobe area of ​​the transmission pattern is high, and the signal-to-noise ratio of the target echo in the side lobe area is greatly lost, which greatly reduces the probability of target detection. Compared with the traditional phased array, the frequency diversity array FDA radar introduces a frequency step on the carrier frequency between the array elements. , forming a time-angle-distance dependent directional pattern, and realizing scanning of different spatial ranges by controlling the frequency step of the array element. When The pulse width of the pulse radar, FDA has the characteristics of full spatial coverage.

[0003] Because the FDA radar has wide spatial coverage, the emission pattern performs uniform and continuous scanning of a large-scale airspace within the pulse duration, which shortens the beam dwell time at a certain azimuth angle position, resulting in low target echo signal energy, making it difficult to meet detection requirements. Therefore, the target echo must be accumulated. However, during the target echo accumulation process, that is, during the observation time, the high-speed movement of the target will cause the target echo signal envelope to be misaligned, resulting in the main lobe widening and the accumulation peak value decreasing, and the echo signal will move across the range gate. To address these problems, researchers have proposed a long-term radar target accumulation method to enhance the target echo energy by extending the observation time, thereby increasing the signal-to-noise ratio of the received signal and improving the probability of target detection.

[0004] Existing radar target long-term integration methods can be mainly divided into two types: non-coherent integration and coherent integration. Non-coherent integration generally does not consider the phase information of the echo and simply adds the echo envelopes in amplitude. This significantly reduces the gain in low signal-to-noise ratio environments. Coherent integration is essentially a matched filter on a uniform pulse train. It simultaneously utilizes the target's amplitude and phase information for accumulation, effectively improving the target signal energy and radar detection performance.

[0005] The patent document with application number 202110522562.2 discloses a "space-based radar space moving target detection and parameter estimation method and system", and its implementation scheme is as follows: the first step is to pre-process the radar echo to obtain a baseband echo signal; the second step is to construct a corresponding phase compensation function to simultaneously eliminate the influence of Doppler blur and Doppler distortion in the baseband echo signal; the third step is to perform a keystone transform on the echo signal that eliminates Doppler blur and Doppler distortion to complete the linear range walk correction; the fourth step is to construct an acceleration matched filter group to eliminate the remaining range curvature and Doppler spread; the fifth step is to complete the final coherent accumulation result after completing the range walk and Doppler spread correction using a two-dimensional Fourier transform. Although this method uses the coherent accumulation method to complete the detection and parameter estimation of space moving targets by space-based radar, this method is more expensive and difficult to implement than ground-based FDA radar due to the use of space-based radar.

[0006] Patent document 202410930490.9 discloses a "Method for Designing Joint Transceiver Multi-Beams Based on a Coherent Frequency Diversity Array." Its implementation scheme includes the following steps: First, establish the LFM baseband signal envelope of a coherent FDA radar linear frequency modulation signal (LFM), obtain the received echo signal of the coherent FDA radar, design an angle-dependent matched filter, and calculate the filtered transmit domain echo data based on the radar's received echo signal; Second, extract the transmit steering vector of the transmit domain echo data and calculate the joint transmit and receive beam steering vector. This invention can be used for transmit-dimensional beamforming and pulse compression. Because this method uses a one-dimensional frequency diversity FDA linear array and scans only in one dimension, the transmit beam scanning range is limited. Furthermore, because the FDA radar trades pulse time resources for wide spatial coverage, the target echo energy is low and the signal-to-noise ratio is low. Summary of the Invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned existing technologies and propose a long-term target accumulation method and system based on ADMF in the FDA radar array system to expand the transmit beam scanning range, enhance the target echo energy, improve the signal-to-noise ratio, and reduce the radar cost.

[0008] The technical approach to achieving the objectives of the present invention is to expand the transmit beam scanning range through a planar array system combining FDA with a phased array, enhance the target echo energy by performing ADMF and long-term coherent accumulation on the target echo, improve the signal-to-noise ratio, and reduce radar costs while achieving large-scale airspace scanning by using a ground-based FDA radar.

[0009] According to the above ideas, the technical solution of the present invention includes:

[0010] 1. A method for long-term target accumulation based on ADMF in an FDA radar array system, characterized by comprising:

[0011] (1) Establishing a surface array echo signal model combining phased array and frequency diversity array (FDA) ;

[0012] (2) Echo signal of FDA radar array system Perform time-angle two-dimensional matched filtering ADMF to obtain the matched filtered signal ;

[0013] (3) For the signal after matched filtering Perform first-order KT transformation to obtain the data after first-order KT transformation ;

[0014] (4) Results after first-order KT transformation The phase term caused by Doppler ambiguity is compensated to obtain the echo signal after Doppler ambiguity compensation ;

[0015] (5) Echo signal after first-order KT transform and Doppler ambiguity compensation , perform distance dimension IFFT and slow time dimension FFT in sequence to obtain the coherently accumulated signal .

[0016] Furthermore, the echo signal model of the area array combining the phased array and the frequency diversity array FDA is established in (1) , which includes:

[0017] (1a) According to the array element arrangement, the array element carrier frequency and array element transmission delay are obtained, and the FDA array transmission pattern is derived. ,in represents the azimuth, represents the pitch angle, Indicates time,

[0018] (1b) Assume that the target's uniform speed is a1 and the initial distance is R0. Calculate the distance between the target and the radar.

[0019] According to the distance between the target and the radar And the FDA array system emission pattern Calculate target echo :

[0020] 2. A long-term target accumulation system based on ADMF in an FDA radar array system, characterized by comprising:

[0021] FDA area array transmitting module 1, used to realize wide coverage area array transmission combining phased array and FDA;

[0022] Moving target echo receiving module 2, used for receiving target echo in the area array system combining phased array and FDA;

[0023] A time-angle two-dimensional matched filter module 3 is used to construct a time-angle two-dimensional matched filter and perform matched filtering on the echo of the moving target echo receiving module;

[0024] The first-order KT transform module 4 is used to perform a first-order KT transform on the result of the time-angle two-dimensional matched filter module to correct the cross-range gate movement caused by the high-speed motion of the target;

[0025] Doppler ambiguity compensation module 5, used to compensate for the phase term caused by Doppler ambiguity;

[0026] The coherent accumulation module 6 is used to focus the energy of the target echo after range movement correction to increase the echo signal-to-noise ratio and improve the target detection probability.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] First, the present invention adopts a planar array system combining a phased array and an FDA, which can expand the scanning range of the transmitting beam and realize large-scale spatial scanning.

[0029] Secondly, the present invention adopts ADMF and long-term coherent integration method under the FDA array system, thereby enhancing the target echo energy and improving the signal-to-noise ratio.

[0030] Third, since the present invention uses a ground-based FDA radar, it can achieve large-scale airspace scanning while reducing radar costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of the target long-term accumulation method based on ADMF in the FDA radar array system of the present invention;

[0032] Figure 2 Schematic diagram of the array element arrangement and carrier frequency in the method of the present invention;

[0033] Figure 3 It is a schematic diagram of azimuth and elevation coordinates in the method of the present invention;

[0034] Figure 4 This is a block diagram of the target long-term accumulation system module based on ADMF in the FDA radar array system of the present invention;

[0035] Figure 5 is the directional pattern emitted by the FDA radar array in the present invention;

[0036] Figure 6 This is a diagram showing the simulation results of the time-angle two-dimensional matcher and matched filtering designed in the present invention;

[0037] Figure 7 This is a time-domain simulation diagram of the echo after matched filtering using the time-angle two-dimensional matcher of the present invention;

[0038] Figure 8 This is a simulation diagram of the range movement correction result after completing the first-order KT transformation and Doppler ambiguity compensation in the present invention;

[0039] Figure 9 This is an energy focusing simulation diagram after the coherent accumulation of echoes in the present invention;

[0040] Figure 10 It is a simulation result diagram of detecting the target after coherent accumulation of the present invention. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0042] It should be noted that the step numbers in the specification and claims of the present invention are only for the purpose of clearly describing the embodiments of the present invention and facilitating understanding, and the order of the step numbers is not limited.

[0043] Example 1: Target long-term accumulation method based on ADMF in FDA radar array system

[0044] Reference Figure 1 The implementation steps of this example include:

[0045] Step 1: Establish a planar array echo signal model combining a phased array and a frequency diversity array.

[0046] 1.1) Simulate the array transmission pattern based on array element arrangement, array element carrier frequency, and array element transmission delay;

[0047] The array form of the present invention is embodied in the form of an azimuth-dimensional frequency diversity array and an elevation-dimensional phased array. The array elements are arranged as follows: Figure 2 As shown, the radar antenna is a side-view array with M=8 row elements and N=8 column elements. The elements are evenly spaced with a spacing of half a wavelength. Each row of N elements forms a one-dimensional FDA linear array. The frequency deviation between the column elements is ; Each column of M array elements is a one-dimensional traditional phased array.

[0048] According to the arrangement of array elements, the carrier frequency of the array element in the mth row and nth column can be known. for:

[0049] ,

[0050] in is the carrier frequency of the first array element, is the frequency offset of the array element;

[0051] like Figure 3 As shown, in the rectangular coordinate system, the azimuth angle of the incident signal is defined as The incident signal is The angle between the projection of the surface and the X axis, the value range is [-90°, 90°], the pitch angle is the incident direction and its The angle of the plane projection ranges from [-90°, 90°], and the distance between the moving target and the array element is .

[0052] According to the array element arrangement, the transmission delay of the array element in the mth row and nth column can be known. for:

[0053] ,

[0054] in represents the array element spacing, c is the speed of light, is the initial distance to the target;

[0055] According to the properties of the one-dimensional linear array FDA transmission pattern and the FDA array transmission pattern related to time-angle-distance and the array element carrier frequency, each array element transmission delay, and array element arrangement, the FDA array transmission pattern is calculated. :

[0056] ,

[0057] in is the FDA array transmission pattern gain, is the frequency offset of the array element, is the carrier frequency of the first array element, t is the time, M is the number of array rows, and N is the number of array elements;

[0058] 1.2) Simplify the theoretical emission pattern;

[0059] Due to the frequency deviation , so it can be ignored and The coupling term between them simplifies the theoretical emission pattern into the following formula:

[0060] ,

[0061] in, for A matrix of dimension, for

[0062] A matrix of dimension, For the matrix , b is the Kronecker product;

[0063] 1.3) Establish a moving target model and simulate the moving target echo;

[0064] 1.3.1) Assume that the target uniform motion speed is , moving close to the radar, the initial distance is , calculate the distance between the target and the radar :

[0065] ,

[0066] in is the slow time variable, prt is the pulse repetition period;

[0067] 1.3.2) Calculate the receiving delay of the array element based on the array element arrangement :

[0068] ;

[0069] 1.3.3) According to the distance between the target and the radar and array element arrangement to obtain target echo :

[0070] ,

[0071] in, Indicates the transmission of pulse signals. is the linear frequency modulation signal echo, is the receiving delay, is the wavelength.

[0072] Step 2: Construct a time-angle two-dimensional matched filter to filter the echo signal. Perform matched filtering.

[0073] The time-angle two-dimensional matched filter is the complex conjugate of the array transmission signal. In the present invention, a linear frequency modulation signal is used as the transmission signal: , let the expected beam pointing angle of the matched filter be , the desired beam pointing elevation angle is , construct the time-angle two-dimensional matched filter as follows:

[0074] ,

[0075] in, is a space-time joint filter with , pitch angle The direction forms the main lobe gain for spatial filtering, which is consistent with the transmitted signal at time t. Time filtering with precise waveform matching; To transmit a signal The complex conjugate of is the carrier frequency of the element in the mth row and nth column;

[0076] Using the time-angle two-dimensional matched filter , the array echo signal is processed by time domain convolution Perform matched filtering to obtain the matched filtering result :

[0077] ,

[0078] In the formula is the matched filter gain, is the bandwidth, is the distance between the moving target and the radar, is the wavelength and t is the time.

[0079] Step 3: Match the results after filtering Perform a first-order KT transform.

[0080] 3.1) Matched filtering results in step 2 Perform FFT along the distance dimension to obtain the data before KT transformation :

[0081]

[0082] Where n=0,1,…N-1 is the array element column number, is the distance compression gain, is the distance frequency, K is the modulation frequency, is the pulse duration, is the carrier frequency of the first array element, is the column frequency deviation, is the distance of the moving target;

[0083] because ,so Can be approximately equal to , so the above formula is simplified to:

[0084] ;

[0085] 3.2) According to the property that the target will move at a distance due to high-speed movement, the data before KT transformation is Perform IFFT along the distance dimension to obtain the distance compression result :

[0086] ,

[0087] in It represents the scattering coefficient of the target signal after range compression, Br is the signal bandwidth, is the target speed, is the initial distance to the target, For slow time;

[0088] From the above formula, we can see that the distance compression result The envelope will follow the curve distribution, where the target speed This will cause the envelope to move linearly, which in turn will cause the target to move in range.

[0089] 3.3) Compress results based on distance The target speed If the target moves away from the target, we first need to transform the data before KT Perform first-order KT transformation to remove the distance frequency With target speed The coupling between them is realized by using the chrip_z method to perform a first-order KT transformation on the data before KT transformation. Substitute the data before KT transformation , we can get the data after first-order KT transformation :

[0090] ,

[0091] in, is the old slow time variable, is the new slow time variable after transformation;

[0092] It can be seen from the above formula that after completing the first-order KT transformation, its speed and distance frequency The coupling relationship between them has been released, thus achieving distance correction.

[0093] Step 4: Doppler ambiguity compensation.

[0094] When the target speed exceeds the maximum unambiguous speed, Doppler ambiguity will occur, generating a phase term in the echo signal. , which causes the target to move in distance, so the phase term caused by Doppler ambiguity must be compensated. The solution is: first, the target speed Doppler fuzzy number Indicates that the Doppler ambiguity compensation function H is constructed and then combined with the first-order KT transformation result To perform multiplication, the implementation steps include the following:

[0095] 4.1) When the target has velocity ambiguity, the actual target velocity is determined by the baseband velocity. and Doppler fuzzy number The target actual speed can be expressed as:

[0096] ,

[0097] Where, is the target maximum unambiguous velocity, prf is the pulse repetition frequency, is the wavelength, c is the speed of light;

[0098] According to the relevant FDA system The properties of ,Will 、 Substitution We can get:

[0099] ,

[0100] in, is the distance frequency, is the carrier frequency of the first array element;

[0101] 4.2) According to the Doppler ambiguity number Constructing Doppler ambiguity compensation function :

[0102] ,

[0103] in is the slow time after the first-order KT transformation;

[0104] 4.3) Set the target actual speed Substitute into the data after first-order KT transformation , we get the following formula:

[0105]

[0106] in, is the Doppler ambiguity compensation gain, K is the linear frequency modulation frequency, is the pulse duration;

[0107] 4.4) Then the Doppler ambiguity compensation function The data after the first-order KT transformation in step 4.3) Multiply to get the result after Doppler ambiguity compensation :

[0108]

[0109] in is the initial distance of the target; it can be seen from this formula that the envelope movement caused by Doppler ambiguity has been eliminated.

[0110] Step 5: Doppler coherent accumulation.

[0111] Although the target range movement has been corrected through the first-order KT transform and Doppler ambiguity compensation, the target echo signal energy of the FDA radar is small and the signal-to-noise ratio is low. Therefore, it is necessary to perform long-term coherent accumulation on the echo after range movement correction to increase the echo energy. The implementation scheme includes the following:

[0112] 5.1) Results after Doppler ambiguity compensation Perform distance dimension IFFT to obtain the result before coherent accumulation :

[0113] ,

[0114] in is the signal gain, is the signal bandwidth, is the initial distance to the target, is the target baseband speed, is the carrier frequency of the first array element, is the slow time after the first-order KT transformation, c is the speed of light, and t is the time;

[0115] 5.2) Results before coherent accumulation Perform slow time FFT to obtain the result after coherent accumulation :

[0116] ,

[0117] in, is the Doppler frequency variable corresponding to the slow time, is the signal gain after coherent integration, is the wavelength.

[0118] From this formula, we can see that the energy of a moving target will form a peak in the range-Doppler domain, and the peak position of energy focus is , that is, distance The speed that can be detected is goal.

[0119] The flowchart representation or method representation of the above embodiments can be understood as representing a module, segment or portion of code including one or a group of executable instructions configured to implement the steps of a specific logical function or process. The present invention is not limited to the disclosed preferred embodiments, and its implementation can be performed in a different order than that shown or discussed, including performing functions in a substantially simultaneous manner according to the functions involved.

[0120] Example 2: A long-term target accumulation system based on ADMF in an FDA radar array system.

[0121] Reference Figure 4 This example includes: an FDA array transmitting module 1, a moving target echo receiving module 2, a time-angle two-dimensional matched filter module 3, a first-order KT transform module 4, a Doppler ambiguity compensation module 5, and a coherent accumulation module 6. The first-order KT transform module 4 includes a first-order KT transform preprocessing submodule 41, a scale transform submodule 42, and a first-order KT transform execution submodule 43; the Doppler ambiguity compensation module 5 includes a compensation function submodule 51 and a Doppler ambiguity compensation execution submodule 52. The operating principle of the entire system is as follows:

[0122] The FDA area array transmitting module 1 is used to realize the wide coverage area array transmission combining the phased array and the FDA;

[0123] The moving target echo receiving module 2 is used to receive the target echo in the area array system combining the phased array and the FDA, and send it to the time-angle two-dimensional matched filter module 3;

[0124] The time-angle two-dimensional matched filter module 3 is used to construct a time-angle two-dimensional matched filter and perform matched filtering on the echo of the moving target echo receiving module, and send the result of the matched filtering to the first-order KT transformation module 4;

[0125] The first-order KT transform module 4 is used to perform a first-order KT transform on the result of the time-angle two-dimensional matched filtering module 3 to correct the cross-range gate movement caused by the high-speed motion of the target. The first-order KT transform preprocessing submodule 41 is used to perform a range FFT on the result after the matched filtering to prepare for the first-order KT transform and send its data to the first-order KT transform execution submodule 43; the scale transformation submodule 42 is used to provide a new slow time variable to decouple the range frequency and slow time, and send its result to the first-order KT transform execution submodule 43; the first-order KT transform execution submodule 43 is used to perform a first-order KT transform on the data of the first-order KT transform preprocessing submodule 41 according to the new slow time variable of the scale transformation submodule 42, and send the data after the first-order KT transform to the Doppler ambiguity compensation module 5;

[0126] The Doppler ambiguity compensation module 5 is used to compensate the phase term caused by Doppler ambiguity in the data of the first-order KT transform module 4. The compensation function submodule 51 is used to construct a Doppler ambiguity compensation function based on the Doppler ambiguity number and send the result to the Doppler ambiguity compensation execution submodule 52. The Doppler ambiguity compensation execution submodule 52 is used to compensate the result of the first-order KT transform module 4 based on the result of the compensation function submodule 51. The compensated data is then sent to the coherent accumulation module 6.

[0127] The coherent accumulation module 6 is used to perform coherent accumulation on the results of the Doppler ambiguity compensation module 5 to increase the echo signal-to-noise ratio and improve the target detection probability.

[0128] It should be noted that the above-mentioned functional modules can be implemented in whole or in part through software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a program instruction product. The program instruction product includes one or a group of program instructions. When the program instructions are loaded and executed on a computer, the process or function described is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The program instructions can be stored in a computer-readable and writable storage medium, or transferred from a computer-readable and writable storage medium to another computer-readable and writable storage medium.

[0129] The direct coupling or communication connection between the modules shown or discussed in this embodiment can be achieved through indirect coupling or communication connection of some interfaces, devices or modules. The various functional modules and submodules in this embodiment can be dynamically located in a processing component, each module can also exist physically separately, or two or more modules can be dynamically located in a processing component. When the above-mentioned dynamic components are implemented in the form of software functional modules and sold or used as independent products, they can also be stored in a computer-readable and writable storage medium.

[0130] The effects of the present invention can be further illustrated by the following simulation results.

[0131] 1. Simulation conditions:

[0132] The software platform for the simulation experiment is MATLAB R2023a;

[0133] The parameters of the simulation experiment are set as follows: the number of radar antenna row elements is M=8, the number of column elements is N=8, the array elements are placed at equal intervals, and the spacing is is half wavelength, and the radar operating wavelength is is 0.1m, the accumulated pulse number Nm is 1000, the target azimuth speed is 0, and the radial speed is =210m / s, the initial distance to the target is =0.6km, pulse repetition frequency prt=100Hz, fast time sampling rate Fr=30MHz, bandwidth Br=50MHz, fast time sampling point value Nr=300. Scanning azimuth The value range is [-90°, 90°], scanning pitch angle The value range is [-90°, 90°], assuming that the main lobe of the antenna points to , where the desired beam points to the azimuth angle =0°, the desired beam pointing elevation angle =30°, the array element weighting matrix is ​​an all-1 matrix.

[0134] 2. Simulation Content

[0135] Simulation 1: Under the above conditions, the present invention is used to simulate the emission pattern of the area array combined with the phased array and the FDA. The results are as follows: Figure 5 shown.

[0136] from Figure 5 It can be seen that the transmitting beam can realize continuous scanning of large-scale airspace in the azimuth dimension, and the azimuth dimension scanning range is -90°~90°, realizing full coverage of the azimuth dimension space. The transmitting beam points to the desired pitch angle in the pitch dimension, so the surface array combining the phased array and FDA has the characteristics of wide spatial coverage. Compared with the one-dimensional linear array, the present invention scans in two dimensions, azimuth and pitch, and can expand the scanning range of the transmitting beam.

[0137] Simulation 2: Under the above conditions, the present invention is used to construct a time-angle two-dimensional matched filter in a planar array system combining a phased array and FDA, and the original echo signal is matched filtered. The results are as follows: Figure 6 As shown, Figure 6 (a) is the constructed time-angle two-dimensional matched filter, Figure 6 (b) is the matched filtering result.

[0138] from Figure 6 (a) It can be seen that the matched filter has the maximum gain at the 150 range gate; Figure 6 (b) It can be seen that the matched filtering result has a peak at the target initial distance of 0.6 km, and the main lobe is about 30 dB higher than the side lobe, so the matched filtering effect is good.

[0139] Simulation 3, under the above conditions, the results after matched filtering are transformed into the azimuth time domain-range time domain two-dimensional plane, and the results are as follows Figure 7 As shown; then the first-order KT transform and Doppler ambiguity compensation are performed on the azimuth time domain-range time domain data after matched filtering to complete the range movement correction. The result is as follows Figure 8 shown.

[0140] from Figure 7It can be seen that the horizontal axis is the range gate and the vertical axis is the azimuth gate. Due to the high-speed movement of the target, the target crosses multiple range gates within one CPI time, and the range movement phenomenon is obvious.

[0141] from Figure 8 It can be seen that the horizontal axis is the range gate and the vertical axis is the azimuth gate. After the first-order KT transform and Doppler ambiguity compensation, the target range movement phenomenon is significantly improved. After correction, the target is located near the 140 range gate.

[0142] Simulation 4, under the above conditions, the present invention is used to perform coherent accumulation on the signal after distance movement correction, and the results are as follows Figure 9 As shown, Figure 9 (a) is the result after coherent accumulation, Figure 9 (b) Yes Figure 9 (a) Enlarged view of the energy focus point; transform the coherent accumulation result to the velocity-distance plane, the result is as follows Figure 10 shown.

[0143] from Figure 9 (a) It can be seen that there is a bright spot in the azimuth frequency domain-range time domain, indicating that the present invention has obvious coherent accumulation and focusing effects;

[0144] from Figure 9 (b) It can be seen that after magnification, the bright spot is a longitudinal strip with uneven color. The yellow area in the middle is the highest energy point, which is around azimuth frequency gate 702 and range gate 133. The yellow area at the highest energy is small, indicating an ideal focusing effect.

[0145] from Figure 10 It can be seen that there is a narrow peak with an amplitude of 8.348e8 at a distance of 0.5km and a speed of 210.035m / s. The peak is the detected target. The detected target speed and distance are consistent with the set target initial speed of 210m / s and the initial distance of 0.6km, and the target peak is large, indicating that the present invention increases the echo energy, realizes energy focusing, improves the distance movement of high-speed moving targets, and has a high detection accuracy.

Claims

1. A long-term target accumulation method based on ADMF in an FDA radar array system, characterized in that: include: (1) Establishing a surface array echo signal model combining phased array and frequency diversity array (FDA) ; (4) Echo signal of FDA radar array system Perform time-angle two-dimensional matched filtering ADMF to obtain the matched filtered signal ; (3) For the signal after matched filtering Perform first-order KT transformation to obtain the data after first-order KT transformation ; (4) Results after first-order KT transformation The phase term caused by Doppler ambiguity is compensated to obtain the echo signal after Doppler ambiguity compensation ; (5) Echo signal after first-order KT transform and Doppler ambiguity compensation , perform distance dimension IFFT and slow time dimension FFT in sequence to obtain the coherently accumulated signal .

2. The method according to claim 1, characterized in that In (1), a surface array echo signal model combining a phased array and a frequency diversity array FDA is established. , which includes: (1a) Based on the array element arrangement, the array element carrier frequency and array element transmission delay are obtained, and the FDA array transmission pattern formula is derived: ； in, is the carrier frequency of the element in the mth row and nth column; is the transmission delay of the m-th row and n-th column array element, represents the azimuth, represents the pitch angle, represents time, d represents the array element spacing, is the frequency offset of the array element, is the carrier frequency of the first array element, c is the speed of light, is the initial distance to the target, M is the number of array rows, and N is the number of arrays; (1b) Establishing a moving target model , simulated echo : Assume that the target uniform motion speed is , the initial distance is , calculate the distance between the target and the radar for: ,in For slow time; According to the distance between the target and the radar Get target echo : ； in, is the receiving delay of the m-th row and n-th column array element; Indicates the transmission of pulse signals. is the linear frequency modulation signal echo, is the wavelength.

3. The method according to claim 1, characterized in that The echo signal of the FDA radar array system in (2) Perform time-angle two-dimensional matched filtering ADMF, which includes: (2a) Constructing a time-angle two-dimensional matched filter based on the FDA array transmission pattern and the transmitted signal : ； in, is the complex conjugate of the transmitted linear frequency modulation signal, M is the number of array rows, N is the number of array arrays, d is the array element spacing, is the carrier frequency of the m-th row and n-th column array element, t is the time, is the beam pointing azimuth, is the beam pointing elevation angle; (2b) The echo signal is filtered using a time-angle two-dimensional matched filter. Perform matched filtering and get the matched filtering result as : ； In the formula is the matched filter gain, is the bandwidth, is the distance between the moving target and the radar, is the wavelength.

4. The method according to claim 1, wherein The signal after matched filtering in (3) Perform a first-order KT transformation, which includes: (3a) For the matched filtered signal Perform FFT along the distance dimension to obtain the data before KT transformation : ； in, is the signal gain, is the distance frequency, is the modulation frequency of the linear frequency modulation signal, is the pulse duration, is the distance between the moving target and the radar, is the carrier frequency of the first array element, c is the speed of light; (3b) Use the chrip_z method to perform a first-order KT transformation on the data before KT transformation according to the following formula: ； in is the old slow time variable, is the new slow time variable after transformation; (3c) Substitute the first-order KT transformation formula in (3b) into the data before KT transformation in (3a) , get the result after first-order KT transformation : ； in is the initial distance to the target, is the carrier frequency of the first array element, is the target speed.

5. The method according to claim 1, wherein The result after the first-order KT transformation in (4) is The phase term caused by Doppler ambiguity is compensated in , which includes: (4a) The actual target velocity is expressed as Doppler fuzzy number, and the target baseband velocity is set to , the Doppler ambiguity number is , the actual speed of the target can be expressed as : ； Where prf is the pulse repetition frequency, is the wavelength, c is the speed of light; (4b) According to the Doppler ambiguity number Constructing Doppler ambiguity compensation function : ； in is the slow time after the first-order KT transformation, is the distance frequency, is the carrier frequency of the first array element; (4c) The Doppler ambiguity compensation function Data after KT transformation Multiply to get the result after Doppler ambiguity compensation : ； in is the gain after Doppler ambiguity compensation, K is the frequency modulation rate of the linear frequency modulation signal, is the pulse duration, is the initial distance to the target.

6. The method according to claim 1, characterized in that The result after the first-order KT transform and Doppler ambiguity compensation in (5) , perform distance dimension IFFT and slow time dimension FFT in sequence, which includes: (5a) Result after Doppler ambiguity compensation Perform distance dimension IFFT to obtain the result before coherent accumulation : ； in is the signal gain, is the signal bandwidth, is the initial distance to the target, is the target baseband speed, is the carrier frequency of the first array element, is the slow time after the first-order KT transformation, c is the speed of light, and t is the time; (5b) Results before coherent accumulation Perform slow time FFT to obtain the result after coherent accumulation : ； in is the Doppler frequency variable corresponding to the slow time, is the signal gain after coherent integration, is the wavelength.

7. A target long-term accumulation system based on ADMF in the FDA radar array system, characterized by: include: FDA area array transmitting module 1, used to realize wide coverage area array transmission combining phased array and FDA; Moving target echo receiving module 2, used for receiving target echo in the area array system combining phased array and FDA; A time-angle two-dimensional matched filter module 3 is used to construct a time-angle two-dimensional matched filter and perform matched filtering on the echo of the moving target echo receiving module; The first-order KT transform module 4 is used to perform a first-order KT transform on the result of the time-angle two-dimensional matched filter module to correct the cross-range gate movement caused by the high-speed motion of the target; Doppler ambiguity compensation module 5, used to compensate for the phase term caused by Doppler ambiguity; The coherent accumulation module 6 is used to focus the energy of the target echo after range movement correction to increase the echo signal-to-noise ratio and improve the target detection probability.

8. The system according to claim 7, characterized in that The first-order KT transformation module 4 includes: The first-order KT transform preprocessing submodule 41 is used to perform distance FFT on the result after matched filtering to prepare for the first-order KT transform; The scale transformation submodule 42 is used to provide a new slow time variable to decouple the range frequency from the slow time; The first-order KT transform execution submodule 43 is used to perform a first-order KT transform on the result of the first-order KT transform preprocessing submodule.

9. The system according to claim 7, wherein: The Doppler ambiguity compensation module 5. includes: The compensation function submodule 51 is used to construct a Doppler ambiguity compensation function according to the Doppler ambiguity number; The Doppler ambiguity compensation execution submodule 52 is used to compensate the result of the first-order KT transformation module according to the result of the compensation function submodule.

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