A high-resolution goniometry method based on target decoupling

Abstract

The application discloses a high-resolution angle measurement method based on target decoupling, and belongs to the field of radar signal processing. Firstly, the direction of arrival of a target is measured preliminarily, and then it is judged whether the main lobe formed by the target is composed of one target or two targets with similar angles, if the main lobe is composed of one target, the angle measurement result is directly output; if the main lobe is composed of two targets, the two targets are searched again by using a decoupling algorithm, so that the two targets with similar angles are identified. The application uses the reconstructed received signal vector to judge the coupling of the target searched preliminarily, and defines a two-dimensional angle spectrum to decouple the target, so that the angle resolution is improved, the calculation complexity is low, and compared with the MUSIC algorithm, the two similar target azimuth angles that cannot be distinguished by the MUSIC algorithm can be distinguished.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing, and more specifically, relates to a high-resolution angle measurement method based on target decoupling. Background Technology

[0002] Direction of Arrival (DOA) estimation is a crucial aspect of array signal processing, and it has become a critical task in many fields, including radar and sonar. Existing DOA algorithms primarily rely on Digital Beamforming (DBF), Deterministic Maximum Likelihood (DML), and Multi-Signal Classification (MUSIC). DBF offers good noise immunity and low computational complexity, but its angular resolution is relatively low. DML provides high angular resolution but requires prior knowledge of the number of targets. While MUSIC offers relatively high angular resolution, there is still room for improvement, and it requires computationally complex eigenvalue decomposition. Summary of the Invention

[0003] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a high-resolution angle measurement method based on target decoupling, the purpose of which is to improve the angle resolution.

[0004] To achieve the above objectives, the present invention provides a high-resolution angle measurement method based on target decoupling, comprising:

[0005] S1. The DBF algorithm is used to conduct a preliminary search of the direction of incoming waves to preliminarily determine the candidate targets;

[0006] S2. For each candidate target, the target amplitude is calculated using the steering vector determined by the target angle obtained in the initial search and the received signal vector. Then, the received signal vector formed by the target is reconstructed using the target amplitude. The local angle spectrum in the neighborhood of the target's corresponding angle is calculated. Based on the error between the local angle spectrum and the global angle spectrum, it is determined whether there is angle coupling for each candidate target.

[0007] For candidate targets without angular coupling, the angle measurement results are output directly; for candidate targets with angular coupling, step S3 is executed.

[0008] S3. Construct a two-dimensional angle spectrum function using the one-dimensional angle spectrum function and its correlation, and search for the maximum value of the two-dimensional angle spectrum function in the neighborhood of the angle to be decoupled to obtain the decoupling azimuth of the target.

[0009] Furthermore, angle θ k The local angle spectrum within the neighborhood is as follows:

[0010]

[0011] θ∈[θ k-δ,θ k +δ], where δ represents the angular neighborhood range, θ k This represents the k-th target angle initially searched in step S1, where N is the number of elements in the antenna array, and a H (θ) represents the transpose conjugate matrix of the antenna array with respect to the N×1 order steering vector a(θ) of the signal; The received signal vector formed to reconstruct target k.

[0012] Furthermore, the received signal vector formed by reconstructing target k is:

[0013]

[0014] Let be the magnitude of the k-th target.

[0015] Furthermore, the magnitude of the k-th objective:

[0016]

[0017] X is an N×1 order received signal vector.

[0018] Furthermore, the two-dimensional angular spectrum function is:

[0019]

[0020] ρ represents the direction angle θ and Relevance; Here, r(θ) is the global angular spectrum function, and r(θ) represents the correlation between the steering vector and the received signal.

[0021] Furthermore, the direction angle θ and Relevance:

[0022]

[0023] Obviously for There is 0 < |r| < 1.

[0024] Furthermore, the correlation between the steering vector and the received signal:

[0025] r(θ) = a H (θ)X

[0026] Furthermore, the global angular spectrum function:

[0027]

[0028] Furthermore, step S1 specifically includes:

[0029] Perform a locality search on f(θ), and denote the found locality as f(θ).k If the following conditions are met:

[0030] f(θ k )>G

[0031] G is the target threshold that is set.

[0032] Overall, the above-described technical solutions conceived by this invention can achieve the following beneficial effects compared with the prior art.

[0033] This invention provides a concise and effective high-resolution angle measurement algorithm based on target decoupling. It uses the reconstructed received signal vector to perform coupling judgment on the initially searched target and defines a two-dimensional angle spectrum to decouple the target, thereby improving the angle resolution and reducing the computational complexity. Compared with the MUSIC algorithm, it can distinguish the azimuth angles of two similar targets that the MUSIC algorithm cannot distinguish. Attached Figure Description

[0034] Figure 1 This is a structural diagram of a high-resolution angle measurement algorithm based on target decoupling;

[0035] Figure 2 It is an antenna layout diagram;

[0036] Figure 3 It is the horizontal radiation pattern of the antenna;

[0037] Figure 4 This is a preliminary search angle spectrum of the direction of incoming wave from the target;

[0038] Figure 5 It is an angle spectrum obtained by processing with the MUSIC algorithm. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0040] The structure diagram of the high-resolution angle measurement algorithm based on target decoupling is as follows: Figure 1 As shown, the direction of the incoming wave from the target is first measured, and then it is determined whether the main lobe formed by the target is composed of a single target or two targets with similar angles coupled together. If it is composed of a single target, the angle measurement result is directly output; if it is composed of two targets coupled together, the decoupling algorithm is used to search for the two targets again, thereby identifying the two targets with similar angles.

[0041] The high-resolution angle measurement algorithm based on target decoupling provided by this invention includes three parts: preliminary search of the direction of incoming wave from the target, target coupling judgment, and target decoupling calculation. These are described below.

[0042] The initial search for the direction of incoming waves from the target includes the following steps:

[0043] Step 1.1: Assuming there are N elements in the antenna array, first define the global angular spectrum function:

[0044]

[0045] Where r(θ) represents the correlation between the steering vector and the received signal:

[0046] r(θ) = a H (θ)X (2)

[0047] a H (θ) represents the transpose and conjugate matrix of the antenna array with respect to the N×1 order steering vector a(θ) of the signal, where X is the N×1 order received signal vector, and θ represents the direction of arrival. Assume the direction of arrival for the m-th target is θ. m You can define a guide vector:

[0048]

[0049] Where, d n Here are the normalized coordinates of the antennas in the linear antenna array, where n represents the antenna number, n = 1, 2, ..., N;

[0050] Step 1.2: Perform a local maximum search on f(θ), and denote the found local maximum as f(θ). k If satisfied

[0051] f(θ k )>G (4)

[0052] The azimuth angle is then used as the candidate target. Here, G is the set target threshold. If the azimuth angles of two targets are very close, they will couple into a local maximum point on the angle spectrum. The following target coupling judgment method is needed to sequentially determine whether each candidate target is coupled.

[0053] Suppose there are K candidate targets. The process involves iterating through these K targets sequentially and determining their coupling characteristics, including the following steps:

[0054] Step 2.1: Calculate the magnitude of the k-th target:

[0055]

[0056] Step 2.2: Reconstruct the received signal vector formed by target k:

[0057]

[0058] Step 2.3: Calculate angle θ k The local angle spectrum within the neighborhood is as follows:

[0059]

[0060] where θ∈[θ k -δ,θ k +δ], where δ represents the angular neighborhood range;

[0061] Step 2.4: Calculate the local angle spectrum The error with the global angle spectrum f(θ) is as follows:

[0062]

[0063] If satisfied

[0064] E(θ k )>D

[0065] Where D is the defined error threshold, if target coupling exists, the following decoupling algorithm needs to be used for decoupling; otherwise θ k There is only one target at the azimuth angle.

[0066] The target decoupling algorithm includes the following steps:

[0067] Step 3.1, Define the two-dimensional angular spectrum:

[0068]

[0069] in, ρ represents the direction angle θ and Relevance:

[0070]

[0071] Obviously for There is 0 < |ρ| < 1;

[0072] Step 3.2, Search The maximum value within the domain can be obtained as follows:

[0073]

[0074] Therefore, the original target azimuth angle θ k Decoupling into two target azimuth angles and This improves angular resolution. Specific implementation examples:

[0076] This embodiment uses a linear array with equidistant elements of N=12 for simulation, with the element spacing being half a wavelength. The antenna layout is as follows. Figure 2 As shown, the horizontal coordinates of the array elements in the figure are normalized coordinates relative to the wavelength λ = 3.9 mm. The antenna horizontal radiation pattern is as follows. Figure 3 As shown, the 3dB main lobe width is 9.270°.

[0077] In this embodiment, it is assumed that there are three targets with target azimuth angles θ of 0°, 5°, and 20°, and signal amplitudes s of 1, 0.9, and 0.8, respectively. Then, the three 12×1 order steering vectors can form a 12×3 order steering matrix:

[0078] A(Θ)=[a(θ1) a(θ2) a(θ3)]

[0079] The target amplitude vector can be defined:

[0080] S = [s1 s2 s3] T

[0081] Assume the signal received on each antenna is x. n Therefore, the received signal vector is:

[0082] X = [x1 x2 … x 12 ] T

[0083] In the absence of noise, the following conditions are met:

[0084] X=A(Θ)S

[0085] In this embodiment, noise with a signal-to-noise ratio (SNR) of 15 dB is added to X. Using the aforementioned high-resolution angle measurement algorithm based on target decoupling, θ is calculated when X is known, but the target azimuth angle θ and amplitude s are unknown. m .

[0086] Based on the preliminary search method for the direction of incoming wave from the target described above, the angle spectrum of this embodiment can be obtained as follows: Figure 4 As shown in the figure, the target threshold G set in this embodiment is one-third of the maximum peak value in the angle spectrum, i.e., G = 15.02 / 3 = 5.01. It can be seen from the figure that the initial search can only distinguish two candidate targets, 0.1° and 20.7° respectively.

[0087] Based on the above method for judging target coupling, the two candidate targets in this embodiment are traversed to judge the target coupling characteristics. In this embodiment, the error threshold D is set to 0.8, and the angular neighborhood range is 3dB main lobe width, i.e., δ is set to 4.635°. It can be determined that there is a situation where two targets are coupled at the 0.1° position.

[0088] Using the above decoupling algorithm to decouple a 0.1° target, the 0.1° target can be distinguished as two targets at 0° and 4.5°. It can be seen that this algorithm can decouple targets and improve angular resolution.

[0089] This algorithm is also compared with the MUSIC angle measurement algorithm, such as... Figure 5 The figure shows the spatial spectrum obtained by the MUSIC algorithm in this embodiment. As can be seen from the figure, the MUSIC algorithm can only distinguish the two targets at 2.8° and 19.8°, and cannot distinguish the two coupled targets in this embodiment, thus proving the superiority of the present invention.

[0090] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-resolution goniometric method based on target decoupling, characterized in that, include: S1. The DBF algorithm is used to conduct a preliminary search of the direction of incoming waves to preliminarily determine the candidate targets; S2. For each candidate target, the target amplitude is calculated using the steering vector determined by the target angle found in the initial search and the received signal vector. Then, the received signal vector formed by the target is reconstructed using the target amplitude. The local angle spectrum in the neighborhood of the target's corresponding angle is calculated. Based on the error between the local angle spectrum and the global angle spectrum, it is determined whether there is angle coupling for each candidate target. For candidate targets without angular coupling, the angle measurement results are output directly; for candidate targets with angular coupling, step S3 is executed. S3. Construct a two-dimensional angle spectrum function using the one-dimensional angle spectrum function and its correlation, and search for the maximum value of the two-dimensional angle spectrum function in the neighborhood of the angle to be decoupled to obtain the decoupling azimuth of the target. where the angle The local angular spectrum within the neighborhood is as follows: , Indicates the angular neighborhood range. This represents the k-th target angle initially found in step S1, where N is the number of elements in the antenna array. This represents the N×1 order steering vector of the antenna array for the signal. The transpose conjugate matrix; The received signal vector formed to reconstruct target k; The two-dimensional angular spectrum function is: , Indicates direction angle and Relevance ; For global angular spectrum function, This indicates the correlation between the steering vector and the received signal.

2. A high-resolution goniometry method based on target decoupling according to claim 1, characterized in that, The received signal vector formed by reconstructing target k: Magnitude for the kth target.

3. The high-resolution angle measurement method based on target decoupling according to claim 2, characterized in that, The magnitude of the k-th target: X is an N×1 order received signal vector.

4. The high-resolution goniometry method based on target decoupling according to claim 2, characterized in that, Step S1 is as follows: The global angular spectrum function is: The maximum point is searched, and the searched maximum value is denoted as , if the following condition is satisfied: G is the target threshold that is set.

5. A computer-readable medium storing a computer program thereon, the computer program, when executed by a processor, implementing the steps of the method as described in any one of claims 1 to 4.

Images