High-sensitivity array direction finding method and device based on digital beam forming

Abstract

The invention belongs to the technical field of signal processing, and particularly relates to a high-sensitivity array direction finding method based on digital beam forming. The method specifically comprises the following steps: step 1, in a direction finding process, after an array receives an information source radiation signal, performing digital beam forming, traversing and searching an interested airspace, so that the radiation signal is incident from a beam main lobe width corresponding to a wave incoming direction, and signals in other wave incoming directions can only be incident in a side lobe of the beam; step 2, digital beam forming: storing the power of a signal after beam forming under each incident angle to obtain a two-dimensional airspace search matrix; and step 3, selecting a maximum value point of the two-dimensional airspace search matrix, storing corresponding coordinates, performing two-dimensional centroid method estimation and iterative calculation in a square region taking the maximum value point as a center, and performing outlier elimination on multiple angle estimation results to obtain a final angle estimation result.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of signal processing, and particularly relates to a high-sensitivity array direction-finding method and device based on digital beam synthesis. BACKGROUND

[0002] Digital beam forming technology is a technology developed on the basis of array antenna and signal processing, and has been widely applied to the field of antenna technology. The basic idea of the technology is to control the directivity function of an antenna array by weighting the data received by the antenna array elements, so that a high-gain narrow beam is generated in the main lobe direction of the directivity function of the antenna array, and a deep null is generated in the side lobe direction. Therefore, only the radiation signal in the direction corresponding to the incoming wave direction will enter from the main lobe direction of the beam, and the noise and interference in other directions are suppressed.

[0003] The common direction-finding method based on digital beam forming at present is the multi-beam amplitude comparison method, which first generates a high-gain beam in the desired direction by using digital beam forming, and then compares the powers of the signals received by different beams to select the beam direction corresponding to the signal with the maximum power as the estimation of the incoming wave direction.

[0004] A prior art multi-same-frequency source phase interferometer direction-finding method based on digital beam forming first detects the signal source by using digital beam forming technology, and then completes direction finding by using the interferometer angle measurement algorithm on the signal formed by digital beam forming. This algorithm can achieve high angle measurement accuracy under the condition of existing spatial interference, but it is a combination of two direction-finding methods, and has high system complexity and large engineering implementation difficulty.

[0005] In order to improve the angle search speed of digital beam forming, a prior art angle search method based on the bisection search idea uses digital beams of different widths to perform bisection search on the angle of the space target, thereby reducing the calculation amount. However, this technology only uses a part of the antenna elements for direction finding each time, and cannot take full advantage of the array gain, so it is difficult to achieve high-precision direction finding in a low signal-to-noise ratio environment.

[0006] In reality, the existence of noise will affect the amplitude of the signal, resulting in errors in the amplitude gain; due to the limitation of the baseline length, the bandwidth of the synthesized beam cannot be infinitely small, and the angle resolution is restricted, resulting in a deviation between the beam direction corresponding to the signal with the maximum power and the true beam direction, and further affecting the angle measurement accuracy of the amplitude comparison method. How to effectively use the information provided by the array to estimate the incident angle under certain external conditions is a direction worthy of research. SUMMARY

[0007] Therefore, the present application provides a high-sensitivity array direction-finding method and device based on digital beam synthesis, which can realize high-sensitivity direction finding.

[0008] The technical scheme adopted by the present application is:

[0009] In the first aspect, the present application is a high-sensitivity array direction finding method based on digital beam synthesis, and the specific process is:

[0010] Step one, in the direction finding process, after the array receives the signal radiated by the signal source, digital beam forming is performed, the space domain of interest is searched, so that the radiated signal is incident within the main lobe width corresponding to the direction of arrival, and the signals of other directions of arrival can only be incident in the side lobe of the beam;

[0011] Step two, digital beam forming, storing the power of the signal after beam forming at each incident angle, obtaining a two-dimensional space domain search matrix;

[0012] Step three, selecting the maximum value point of the two-dimensional space domain search matrix, saving the corresponding coordinates, performing two-dimensional center of gravity estimation in a square region centered on the maximum value point and performing iterative calculation, and obtaining the final angle estimation result by outlier elimination on multiple angle estimation results.

[0013] Optionally, the present application sets the maximum value point as (H max , V max ), and the size of the square region is: H max -5≤m≤H max +5, V max -5≤n≤V max +5, m represents the horizontal coordinate of the square region, and n represents the vertical coordinate of the square region.

[0014] Optionally, the two-dimensional center of gravity estimation and iterative calculation of the present application obtain the horizontal dimension angle estimation value, and the specific process is:

[0015] In the square region, a vertical dimension angle corresponding to a center of gravity is calculated for the mth row, and the distance from the center to the nearest calculation boundary is taken as the calculation range on the left and right sides of the center, and the above process is repeated again. Iteration until the difference between the adjacent two calculation results is less than the threshold, and then the center of gravity obtained by the last calculation is taken as the center of gravity of the row;

[0016] The vertical dimension coordinates of each point are calculated by the center of gravity method, and a column of vertical dimension coordinates with the same data is obtained; and the horizontal dimension coordinates of the column of data are estimated by the center of gravity method to obtain the horizontal dimension center of gravity, i.e. the horizontal dimension angle estimation value.

[0017] Optionally, the vertical dimension angle corresponding to the center of gravity of the present application is:

[0018]

[0019] wherein, θVn represents the vertical dimension angle, P mn represents the element in the mth row and nth column of the two-dimensional spatial search matrix; represents the vertical dimension angle value corresponding to the gravity center of the mth row.

[0020] Optionally, the application obtains a column of data with the same vertical dimension coordinate by:

[0021]

[0022] The horizontal dimension gravity center can be obtained by performing the gravity center method estimation on the horizontal dimension coordinate of the column of data, and the horizontal dimension angle estimation value is:

[0023]

[0024] wherein, i represents the current time, and the G H is denoted as

[0025] Optionally, the application performs the two-dimensional gravity center method estimation and iterative calculation to obtain the vertical dimension angle estimation value, and the specific process is:

[0026] In the square region, the horizontal dimension angle corresponding to a gravity center of the nth column is obtained, and the center is taken as the center, and the distance from the center to the nearest calculation boundary is taken as the calculation range on the left and right sides of the center, and the above process is repeatedly iterated until the difference between the calculation results of adjacent two times is less than a threshold, and the gravity center obtained by the last calculation is taken as the gravity center of the column;

[0027] The horizontal dimension coordinate of each point is calculated by the gravity center method, and a row of data with the same horizontal dimension coordinate is obtained; and the vertical dimension coordinate of the row of data is estimated by the gravity center method, and the vertical dimension gravity center, i.e., the vertical dimension angle estimation value, is obtained.

[0028] Optionally, the gravity center corresponds to the horizontal dimension angle, and the horizontal dimension angle is:

[0029]

[0030] wherein, θ Hm represents the horizontal dimension angle, P mn represents the element in the mth row and nth column of the two-dimensional spatial search matrix; represents the horizontal dimension angle corresponding to the gravity center of the nth column.

[0031] Optionally, the application obtains a row of gravity centers with the same horizontal dimension coordinate, and the horizontal dimension coordinate H G of the row is:

[0032]

[0033] The vertical dimension coordinate of the row of data is estimated by the barycentric method to obtain the vertical dimension barycenter, i.e., the vertical dimension angle estimation value is:

[0034]

[0035] Optionally, the application obtains the final angle estimation result by removing outliers from the multiple angle estimation results; the specific process is: initializing the angle correction value cache array and the data judgment array, wherein the correction value cache array is Assigning true to the corresponding N values in the data judgment array;

[0036] From the N+1th moment, taking the average of the elements in the angle correction value cache array as the correction value at this moment, and putting the original angle estimation value from the N+1th moment into the end of the angle correction value cache array; each time the cache is deleted by moving left to remove one element at the moment, realizing the sliding storage of N moments of data; comparing the angle estimation value obtained at the current moment with the correction value; assigning values to the corresponding angle estimation value in the data judgment array according to the comparison result; and determining the final angle estimation value according to the values in the data judgment array;

[0037] The specific process of assigning values to the corresponding angle estimation value in the data judgment array according to the comparison result and determining the final angle estimation value according to the values in the data judgment array is as follows:

[0038] Case A: if the absolute value of the comparison difference is less than or equal to the set threshold η, then assign true to the element value of the data correct array corresponding to this moment;

[0039] Case B: if the absolute value of the comparison difference is greater than the set threshold η, then assign false to the element value of the data correct array corresponding to this moment;

[0040] Error correction measure: if the correct elements in the data correct array are less than 50%, then invert all elements;

[0041] Result output: taking the average of the elements considered correct in the angle correction value cache array as the final angle estimation result output.

[0042] In a second aspect, the application discloses a high-sensitivity array direction finding device based on digital beam synthesis, which comprises a control module, a signal processing module, and a direction finding module.

[0043] The control module is used to perform digital beam forming after the array receives the radiation signal of the signal source in the direction finding process, search the interested space domain, control the array to rotate so that the radiation signal is incident within the main lobe width corresponding to the direction of arrival, and the signals of other directions of arrival can only be incident in the side lobe.

[0044] Signal processing module, for digital beam forming, storing the power of the signal after beam forming under each incident angle, obtaining a two-dimensional space search matrix;

[0045] Direction finding module, for selecting the maximum point of the two-dimensional space search matrix, saving the corresponding coordinates, performing two-dimensional center of gravity method estimation in the square region centered on the maximum point and performing iterative calculation, obtaining the final angle estimation result by outlier rejection on the multiple angle estimation results.

[0046] Advantages

[0047] Firstly, the application adopts two-dimensional center of gravity method iterative estimation angle based on beam forming, converts two-dimensional estimation into multiple one-dimensional center of gravity calculation, performs center of gravity method angle estimation in the selected range, updates the calculation range according to the iterative result, and performs iterative calculation again until the iterative result meets the requirement, and outputs the estimated angle, which can ensure that the estimated angle is more accurate.

[0048] Secondly, the application adopts outlier rejection algorithm to smooth the estimation result, detects whether each estimation result is correct according to the average value of multiple estimation results, if the difference between the estimation result and the average value is less than the threshold, it is judged that the estimation is correct, and the outlier is corrected to the average value of the estimation result judged to be correct, which can effectively reduce the estimation error. DETAILED DESCRIPTION

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0050] Figure 1 It is a schematic diagram of beam forming algorithm structure;

[0051] Figure 2 It is a horizontal dimension center of gravity method angle estimation flow;

[0052] Figure 3 It is an outlier rejection flowchart;

[0053] Figure 4 It is an array antenna configuration diagram;

[0054] Figure 5 It is the curve of RMSE with the change of signal-to-noise ratio. DETAILED DESCRIPTION

[0055] The embodiments of the application will be described in detail below with reference to the drawings.

[0056] It should be noted that the following embodiments and features of the embodiments can be combined with each other in the case of no conflict; and all other embodiments obtained by those skilled in the art based on the embodiments in the present disclosure without creative labor shall fall within the scope of protection of the present disclosure.

[0057] It should be noted that various aspects of the embodiments described below are within the scope of the appended claims. As will be apparent, the aspects described herein can be embodied in a variety of ways, and that the specification should be considered exemplary only. It should be understood that any feature described herein as being part of one aspect can be implemented by any other aspect. That is, a person skilled in the art should understand that one aspect described herein can be implemented independently of any other aspects and that two or more of the aspects can be combined in various ways. For example, an apparatus can be implemented or a method can be practiced using any number of the aspects set forth herein. In addition, such an apparatus can be implemented or such a method can be practiced using other structure and / or functionality in addition to or other than one or more of the aspects set forth herein.

[0058] First, the process of receiving a uniform linear antenna array of a same frequency narrowband far field signal is mathematically described:

[0059] Taking a one-dimensional M-element equidistant linear array as an example, as shown in Figure 1 , it is assumed that the space signal is a narrowband signal, and each channel is adjusted by a complex weighting coefficient to adjust the amplitude and phase of the channel.

[0060] At this time, the output of the array can be represented as

[0061]

[0062] where w i (θ) is the weighting coefficient of the i-th antenna, "*" represents taking the conjugate, θ is the incident angle, x i (t) is the received signal of the i-th antenna, and M is the number of antennas. If a vector is used to represent the output of each array element and the weighting coefficient, then

[0063] x(t) = [x1(t) x2(t) ··· x M (t)] T ,w(θ) = [w1(θ) w2(θ) ··· w M (θ)] T

[0064] Then, the output of the array can also be represented by a vector

[0065] y(t) = w H (θ)x(t)

[0066] In order to compensate the time delay between each array element in a direction θ to form a main lobe, the weighting vector of the conventional beamformer in the desired direction can be constructed as

[0067] w(θ)=[1e -jωτ ···e -j(M-1)ωτ ] T

[0068] wherein, is the time difference of receiving the same far field signal by two adjacent array elements, d represents the distance between array elements, and c represents the speed of light. Observing the weighting vector, if there is only one signal from the direction θ in the space, the direction vector α(θ) has the same form as the weighting vector, and then

[0069] y(t)=w H (θ)x(t)=α H (θ)x(t)

[0070] The output power of the conventional beamformer can be represented as

[0071] P(θ)=E[y(t) 2 ]=w H (θ)Rw(θ)=α H (θ)Rα(θ)

[0072] wherein, the matrix R is the covariance matrix of the array output x(t), that is, R=E[x(t)x H (t)].

[0073] The design idea of the present application is that after the linear antenna array receives a signal, first, digital beamforming is performed to realize filtering processing on the space domain, and a two-dimensional space domain search grid is obtained, and then angle estimation based on the two-dimensional barycenter method is performed. The one-dimensional barycenter method can be calculated according to the following formula, wherein the coordinates are x i , each point corresponds to a weight ω i , and the barycenter is:

[0074]

[0075] The barycenter method is used for angle estimation, x i is the angle value θ i , ω i is the corresponding power value P i , and the barycenter is:

[0076]

[0077] The two-dimensional barycenter method needs to calculate the barycenters of the horizontal dimension and the vertical dimension respectively, and the intersection point of the barycenters is the barycenter of the two-dimensional space domain search grid, and the estimated angles of the horizontal dimension and the vertical dimension are obtained, such as Figure 2The horizontal dimension gravity angle estimation flow chart is shown. Then, the outlier rejection is performed to reject the values with large estimation error, and the outlier rejection is performed on each estimation result to reduce the estimation error, such as Figure 3 The outlier rejection flow chart is shown, the value of η is set as the judgment threshold, and N is the length of the correction value buffer array and the data judgment array.

[0078] Based on the above design idea, the application embodiment of a high-sensitivity array direction finding method based on digital beam synthesis is as follows:

[0079] Step 1: In the direction finding process, after the array receives the signal source radiation signal, digital beam forming is performed, and the interested space is searched to make the radiation signal incident within the beam main lobe width corresponding to the signal source radiation direction, and the signals of other directions can only be incident in the beam side lobe.

[0080] Step 2: Digital beam forming, store the power of the signal after beam forming under each incident angle, obtain a one-dimensional incident angle search vector after completing a round of search, and finally obtain a two-dimensional space search matrix.

[0081] Step 3: Select the maximum value point of the two-dimensional space search matrix, save the corresponding coordinates, perform two-dimensional gravity method estimation in the square region centered on the maximum value point, and perform iterative calculation, which can reduce the estimation error to obtain an estimation result. The final angle estimation result is obtained by performing outlier rejection on multiple angle estimation results.

[0082] The angle tested by the high-sensitivity array direction finding is a two-dimensional incident angle, and the horizontal incident angle and the vertical incident angle are measured by two groups of mutually perpendicular and baseline equal-length uniform linear arrays. The specific steps of the above process are as follows:

[0083] Premise: In the direction finding process, after the array receives the signal source radiation signal, digital beam forming is performed, and the interested space is searched to make the radiation signal incident within the beam main lobe width corresponding to the signal source radiation direction, and the signals of other directions can only be incident in the beam side lobe.

[0084] Step 1: According to the current searched horizontal incident angle θ Hm and the vertical incident angle θ Vn , the direction vectors α(θ Hm ) and α(θ Vn ) are generated, m=1,...,M, n=1,...,N, M=N=K, K 2 directional beams are generated in each dimension, and there are K

[0085] Step 2: Use the formula y(t)=α H(θ)x(t) weights the data received by each array element to obtain the output of the horizontal dimension and vertical dimension conventional beamforming

[0086] y Hm (t) = α H (θ Hm )x(t)

[0087] y Vn (t) = α H (θ Vn )x(t)

[0088] adding the two to obtain the output of two-dimensional beamforming y mn (t)

[0089] y mn (t) = y Hm (t) + y Vn (t)

[0090] The output Y(t) of all beams after conventional beamforming is calculated, and Y(t) is written in matrix form as:

[0091]

[0092] Step 3: Use Y(t) to perform power detection on the output data of each beam to obtain the received power value P of each beam, i.e. a two-dimensional spatial domain search matrix.

[0093]

[0094] Step 4: The coordinates of each row correspond to the horizontal dimension angle, and the coordinates of each column correspond to the vertical dimension angle. The maximum point (H max , V max ) of the two-dimensional spatial domain search matrix is selected, and the center of gravity angle estimation is performed in the square region centered on the maximum point, i.e. H max -5≤m≤H max +5, V max -5≤n≤V max +5.

[0095] Step 5: In the calculation region, H max -5≤m≤H max +5, for each row (horizontal dimension), a center of gravity (vertical dimension) is iteratively calculated. The iteration process first calculates a center of gravity for the mth row, and the center of gravity corresponds to the vertical dimension angle:

[0096]

[0097] where θ Vn represents the vertical dimension angle, and P mnrepresents the element in the mth row and nth column of the two-dimensional spatial search matrix; represents the vertical dimension angle value corresponding to the mth row barycenter.

[0098] with angle G Hm The corresponding coordinates are taken as the center, and the distance from the point to the nearest calculation boundary is taken as the calculation range on the left and right sides of the point. The barycenter is calculated again, and the above process is repeated until the difference between the two calculation results is less than the threshold. The barycenter obtained by the last calculation is taken as the barycenter of the row.

[0099] Step 6: The vertical dimension coordinates of the barycenters calculated for each row are not the same, so the barycenter method is used to calculate the vertical dimension coordinates of each point, and a column of data with the same vertical dimension coordinates is obtained. The vertical dimension coordinates of the column are V G .

[0100]

[0101] Step 7: The horizontal dimension barycenter, i.e., the horizontal dimension angle estimation value, is obtained by using the barycenter method to estimate the horizontal dimension coordinates of the column data.

[0102]

[0103] where i represents the current time, and the G H is recorded as

[0104] Step 8: The vertical dimension angle estimation method is the same as the horizontal dimension. In the calculation region, V max -5≤n≤V max +5, a barycenter (horizontal dimension) is obtained by iterating for each column (vertical dimension). The iteration process first obtains a barycenter for the nth column, and the barycenter corresponds to a horizontal dimension angle:

[0105]

[0106] where θ Hm represents the horizontal dimension angle, represents the horizontal dimension angle corresponding to the barycenter of the nth column.

[0107] with angle G Vn The corresponding coordinates are taken as the center, and the distance from the point to the nearest calculation boundary is taken as the calculation range on the left and right sides of the point. The barycenter is calculated again, and the above process is repeated until the difference between the two calculation results is less than the threshold. The barycenter obtained by the last calculation is taken as the barycenter of the row.

[0108] Step 9: The horizontal dimension coordinates of the barycenters calculated for each column are not the same, so the barycenter method is used to calculate the horizontal dimension coordinates of each point, and a row of data with the same horizontal dimension coordinates is obtained. The horizontal dimension coordinates of the row are

[0109]

[0110] Step 10: the vertical dimension coordinate of the row data is estimated by the barycentric method to obtain the vertical barycenter, i.e. the vertical angle estimation value

[0111]

[0112] Wherein, i represents the current time, and the current time estimated G V Denoted as

[0113] Step 11: the intersection of the horizontal and vertical dimensions is the two-dimensional barycenter, i.e. the horizontal angle and vertical angle estimation value of the target.

[0114] Step 12: initialize the angle correction value cache array and the data judgment array: repeat steps 1-10 to obtain the Record the original angle estimation value That is, the two-dimensional barycenter method angle iterative estimation is the preliminary result without smoothing processing. For time i≤N, the value of each angle corresponding to the data correct array is set to 1 (1 represents correct, -1 represents error), and it is considered that these estimation results are correct.

[0115] Step 13: detection and correction. From the N+1 time, the average value of the elements in the angle correction value cache array is taken as the correction value at this time, and the original angle estimation value from the N+1 time is put into the end of the angle correction value cache array. Each time the cache is moved to the left and deleted 1 time element, realizing the sliding storage of N time data. The obtained angle estimation value is compared with the correction value at the current time:

[0116] (Case A): if the absolute value of the difference is less than the threshold η: the element value of the data correct array corresponding to this time is assigned to 1.

[0117] (Case B): if the absolute value of the difference is greater than the threshold η: the element value of the data correct array corresponding to this time is assigned to -1.

[0118] Step 14: error correction measure to avoid correction: if the correct elements in the data correct array are less than 50%, then all elements are inverted.

[0119] Step 15: output result: the average value of the elements considered correct in the angle correction value cache array is taken as the final angle estimation result output.

[0120] The present application verifies the above-mentioned high-sensitivity array direction finding method based on digital beam synthesis by using Matlab software. For the sake of simplification, the algorithm model is assumed as follows:

[0121] 1. The distance between each array element in the linear uniform antenna array is fixed without error;

[0122] 2. The position of the radiation source relative to the antenna array is fixed.

[0123] A cross array composed of 5 antennas is used to measure the direction of a narrowband radiation source, and the array configuration is shown in Figure 4 The received signal is a QPSK modulated signal, the wavelength is 0.1m, the intermediate frequency is 100MHz, the signal bandwidth is 1MHz, the sampling frequency is 400MHz, the range of vertical and horizontal incidence angles is ±10°, the distance between the array elements d is 0.25m, the range of SNR in the simulation is set to 0 to 30dB, and the root mean square error (RMSE) is calculated by 500 times of Monte Carlo simulation as an evaluation index:

[0124]

[0125] Wherein, L is the number of Monte Carlo experiments, the smaller the calculated RMSE, the higher the positioning accuracy, and vice versa. As shown in Figure 5 It can be seen that as the signal-to-noise ratio decreases, the direction finding angle error rises, and even when the signal-to-noise ratio is 0dB, the root mean square error of the direction finding angle is still within 0.3°, proving that the direction finding algorithm has high direction finding accuracy in low signal-to-noise ratio environment.

[0126] In summary, the above is only a preferred embodiment of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A high-sensitivity array direction finding method based on digital beamforming, characterized in that: The specific process is: Step 1: During direction finding, after receiving the source radiation signal, the array performs digital beamforming, searching the airspace of interest so that the radiation signal is incident from the main lobe width of the beam corresponding to its direction of arrival, while signals from other directions can only be incident from the side lobes of the beam. Step 2: Digital beamforming, storing the power of the beamformed signal at each incident angle to obtain a two-dimensional spatial search matrix; Step 3: Select the maximum point of the two-dimensional spatial search matrix, save the corresponding coordinates, perform two-dimensional centroid estimation and iterative calculation in the square area centered on the maximum point, and obtain the final angle estimation result by eliminating outliers from the multiple angle estimation results.

2. The high-sensitivity array direction finding method based on digital beamforming according to claim 1 is characterized in that The maximum point is (H max ,V max ), the size of the square area is: H max -5≤m≤H max +5, V max -5≤n≤V max +5, m represents the horizontal coordinate of the square area, and n represents the vertical coordinate of the square area.

3. The high-sensitivity array direction finding method based on digital beamforming according to claim 2, characterized in that: The two-dimensional centroid method estimates and iteratively calculates the horizontal angle estimate. The specific process is: In the square area, find the vertical angle corresponding to the center of gravity of the mth row, and use the coordinates corresponding to the angle as the center. Take the distance from the center to the nearest calculation boundary as the calculation range on both sides of the center. Repeat the above process again until the difference between the two consecutive calculation results is less than the threshold. Then take the center of gravity obtained by the last calculation as the center of gravity of the row. By calculating the vertical coordinates of each point using the centroid method, a column of data with the same vertical coordinates will be obtained; then the horizontal coordinates of this column of data are estimated using the centroid method to obtain the horizontal centroid, that is, the estimated value of the horizontal angle.

4. The high-sensitivity array direction finding method based on digital beamforming according to claim 2, characterized in that: The vertical angle corresponding to the center of gravity is: Among them, θ Vn Indicates the vertical angle, P mn Represents the element in the mth row and nth column of the two-dimensional spatial search matrix; Indicates the vertical angle value corresponding to the centroid of the mth row.

5. The high-sensitivity array direction finding method based on digital beamforming according to claim 4, characterized in that: The data obtained for a column with the same vertical coordinates is: The horizontal coordinates of the column of data are estimated by the centroid method to obtain the horizontal centroid, that is, the estimated value of the horizontal angle is: Among them, i represents the current time, and the current time is estimated to be G H Recorded as 6. The high-sensitivity array direction finding method based on digital beamforming according to claim 2, characterized in that: The two-dimensional centroid method estimates and iteratively calculates the vertical angle estimate, and the specific process is as follows: In the square area, find the horizontal angle corresponding to the center of gravity of the nth column, and use the coordinates corresponding to the angle as the center. Take the distance from the center to the nearest calculation boundary as the calculation range on both sides of the center. Repeat the above process again until the difference between the two consecutive calculation results is less than the threshold. Then take the center of gravity obtained by the last calculation as the center of gravity of the column. By calculating the horizontal coordinates of each point using the centroid method, a row of data with the same horizontal coordinates will be obtained; then the vertical coordinates of this row of data are estimated using the centroid method to obtain the vertical centroid, that is, the estimated value of the vertical angle.

7. The high-sensitivity array direction finding method based on digital beamforming according to claim 6, characterized in that: The horizontal angle corresponding to the center of gravity is: Among them, θ Hm represents the horizontal angle, P mn Represents the element in the mth row and nth column of the two-dimensional spatial search matrix; Indicates the horizontal angle corresponding to the centroid of the nth column.

8. The high-sensitivity array direction finding method based on digital beamforming according to claim 7, characterized in that: The center of gravity of a row with the same horizontal coordinate is obtained, and the horizontal coordinate of the row is H G for: Then, the vertical coordinate of the row of data is estimated by the centroid method to obtain the vertical centroid, that is, the vertical angle estimate is:

9. The high-sensitivity array direction finding method based on digital beamforming according to claim 5 or 8, characterized in that: The final angle estimation result is obtained by eliminating outliers from multiple angle estimation results. The specific process is as follows: initialize the angle correction value cache array and the data judgment array, where the correction value cache array is Assign true to the corresponding N values ​​in the data judgment array; Starting from the N+1th moment, the mean of the elements in the angle correction value cache array is obtained as the correction value at this moment. At the same time, the original angle estimate starting from the N+1th moment is placed at the end of the angle correction value cache array. Each time the cache is performed, the element of one moment is shifted left and deleted to achieve sliding storage of data at N moments. The corrected value is used to compare the currently obtained angle estimate. According to the comparison result, the angle estimate corresponding to the current moment in the data judgment array is assigned. The final angle estimate is determined according to the median value of the data judgment array. The angle estimation value corresponding to the current moment in the data judgment array is assigned according to the comparison result, and the final angle estimation value is determined according to the median value of the data judgment array, specifically: Case A: If the absolute value of the comparison difference is less than or equal to the set threshold η, the element value of the correct data array corresponding to this moment is assigned true; Case B: If the absolute value of the comparison difference is greater than the set threshold η, the element value of the correct data array corresponding to this moment is assigned false; Measures to avoid error correction: If the correct elements in the correct data array are less than 50%, all elements are inverted; Result output: The average of the elements considered correct in the angle correction value cache array is output as the final angle estimation result.

10. A high-sensitivity array direction-finding device based on digital beamforming, characterized in that: include: Control module, signal processing module and direction finding module; The control module is used to perform digital beamforming after the array receives the source radiation signal during the direction finding process, traverse the search of the airspace of interest, and control the array rotation so that the radiation signal is incident from the main lobe width of the beam corresponding to the direction of the wave, while the signals from other directions can only be incident from the side lobes of the beam; The signal processing module is used for digital beamforming, storing the power of the beamformed signal at each incident angle to obtain a two-dimensional spatial search matrix; The direction finding module is used to select the maximum value point of the two-dimensional spatial search matrix, save the corresponding coordinates, perform two-dimensional centroid estimation and iterative calculation in the square area centered on the maximum value point, and obtain the final angle estimation result by eliminating outliers from the multiple angle estimation results.

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