An integrated reference signal extraction and coherent direction finding method

Abstract

The present application belongs to the field of radio direction finding, and particularly relates to a kind of integrated reference signal extraction and phase tracking direction finding method.The present application determines the autocorrelation matrix of array snapshot signal, the data matrix of bidirectional parallel beam forming according to the relevant parameters of direction finding equipment and frequency equipment;Then the linear constraint vector of bidirectional parallel beam forming, the linear constraint matrix of bidirectional parallel beam forming are determined;Then the linear constraint vector of bidirectional parallel beam forming, the phase tracking direction finding space spectrum of search direction are determined;Finally, the direction corresponding to the maximum value in the phase tracking direction finding space spectrum set of search direction is determined to determine the direction finding result of integrated reference signal extraction and phase tracking direction finding, and the reference signal extraction result is determined simultaneously.The present application can improve the coherent signal detection probability and direction finding accuracy in the case that the spatial spectrum direction finding method based on space processing fails to direction find coherent interference source signal.

Description

Technical Field

[0001] This invention belongs to the field of radio direction finding, specifically relating to an integrated method for reference signal extraction and coherent direction finding, or more specifically, a method for integrated reference signal extraction and coherent direction finding through bidirectional parallel beamforming when the reference signal is unknown. Background Technology

[0002] In the field of radio direction finding, there are many spatial spectrum direction finding methods. Classified from the perspectives of spatial, time, and frequency domains, they can be categorized into spatial spectrum direction finding methods based on spatial domain filtering, spatial spectrum direction finding methods based on joint spatial-temporal filtering, spatial spectrum direction finding methods based on joint spatial-frequency filtering, and spatial spectrum direction finding methods based on joint spatial-temporal-frequency filtering. Taking the spatial spectrum direction finding method based on joint spatial-temporal filtering as an example, while using the direction vector for spatial matched filtering to obtain the signal-to-noise ratio (SNR) gain, it also uses the signal's time-domain waveform information for time-domain matched filtering to obtain the SNR gain. This is an important technique for improving the performance of spatial spectrum direction finding methods based on spatial domain filtering. It is commonly used for direction finding of coherent weak signals under strong interference signal suppression and for direction finding of coherent non-direct wave weak signals under direct wave signal suppression.

[0003] In space-time joint filtering spatial spectrum direction finding methods, when using time-domain matched filtering based on signal time-domain waveform information, the matched filter has two inputs: one is the snapshot signal received by the antenna array from the direction finding equipment, and the other is a reference signal. However, unlike active detection where the target echo signal is a known delayed and frequency-shifted copy of the transmitted signal, in non-cooperative signal processing fields such as radio signal detection and interference source monitoring, the reference signal is unknown. To obtain the reference signal, a common method is to set up an independent directional receiving channel to receive the signal transmitted by a specific frequency-using device. However, the reference signal obtained by this method is susceptible to interference from signals from other directions in both the time and frequency domains, requiring further purification processing. Furthermore, it is difficult to apply to applications where the position and orientation of the frequency-using device serving as the reference signal source dynamically change.

[0004] In practice, when a direction-finding device monitors interference source signals near a frequency-using device and operates at the same time and frequency band, the antenna array snapshot signal received by the direction-finding device includes not only the signal transmitted by the frequency-using device but also the interference source signal operating at the same time and frequency band. When the interference source signal is coherent with the signal transmitted by the frequency-using device, the interference is severe. Therefore, direction finding of coherent interference sources is crucial. In this case, if a reference signal can be extracted from the components of the antenna array snapshot signal received by the direction-finding device, the performance advantages of the space-spectrum direction-finding method using space-time joint filtering can be leveraged, improving the direction-finding accuracy of coherent interference sources. Summary of the Invention

[0005] This invention addresses the problem of coherent signal direction finding by proposing an integrated method for reference signal extraction and coherent direction finding. By using bidirectional parallel beamforming of the known direction of arrival and the search direction of the frequency-using equipment, and utilizing the snapshot signal of the antenna array received by the direction-finding equipment, the method simultaneously extracts the reference signal with the known direction of arrival of the frequency-using equipment and performs coherent direction finding of the search direction, thereby improving the accuracy of coherent signal direction finding.

[0006] The technical solution of this invention is as follows:

[0007] An integrated reference signal extraction and coherent direction finding method is proposed. First, the number of antennas, the number of search directions, the set of search directions, and the set of direction vectors corresponding to the search direction set are set for the direction finding device. The number of array signal snapshots received by the direction finding device is also set, along with the known direction of arrival of the frequency-using device, its corresponding direction vector, and the array snapshot signal received by the direction finding device. Next, the autocorrelation matrix of the array snapshot signal and the data matrix of the bidirectional parallel beamforming are determined. Then, the linear constraint vector and linear constraint matrix of the bidirectional parallel beamforming are determined. Next, the bidirectional parallel beamforming vector and the coherent direction finding spatial spectrum of the search directions are determined. Finally, the direction finding result of the integrated reference signal extraction and coherent direction finding is determined by the direction corresponding to the maximum value in the coherent direction finding spatial spectrum set of the search directions, and the reference signal extraction result is also determined.

[0008] The present invention specifically includes the following steps:

[0009] S1. Set the number of antennas of the direction finding device to M, the number of search directions to N, and the search direction to θ. n The set of search directions is {θ1, θ2, ..., θ N}, and the search direction θ n The corresponding direction vector is a(θ) n Let n = 1, 2, ..., N, and the set of all direction vectors be {a(θ1), a(θ2), ..., a(θ...}}. N The direction-finding device receives L snapshots of the array signal, and the known direction of arrival of the frequency-using device is... The corresponding direction vector is The array snapshot signal received by the direction finding equipment is an M×L matrix X;

[0010] S2. Determine the autocorrelation matrix of the array snapshot signal as R = XX H The data generated by bidirectional parallel beamforming is a 2M×2M order matrix.

[0011]

[0012] S3. Determine the linear constraint vector for bidirectional parallel beamforming as follows:

[0013]

[0014] Given the known incoming wave direction and corresponding direction vector of the frequency-using device, the corresponding search direction θ in the set of search directions. n The linear constraint matrix for bidirectional parallel beamforming is determined as follows:

[0015]

[0016] Where n = 1, 2, ..., N;

[0017] S4. Using the data matrix, linear constraint vector, and linear constraint matrix of the bidirectional parallel beamforming, determine the 2M×1 order bidirectional parallel beamforming vector as follows:

[0018] w(θ n )=(A(θ n )Q -1 A H (θ n )) -1 q

[0019] in, H Represents the conjugate transpose of a vector or matrix. -1 Let n denote the inverse of the matrix, where n = 1, 2, ..., N;

[0020] S5, each search direction θ in the corresponding search direction set n The coherent direction-finding spatial spectrum of the search direction is determined as follows:

[0021]

[0022] Among them, w 1:M (θ n ) represents taking a 2M×1 order bidirectional parallel beamforming vector w(θ) n The first M elements of the vector form an M×1 vector, where || represents the absolute value, and n = 1, 2, ..., N;

[0023] S6. Determine the set of coherent direction-finding spatial spectra {g(θ1), g(θ2), ..., g(θ)} for the search direction. N The maximum value in )} is the m-th spatial spectral value g(θ) m ), corresponding to the direction θ m This refers to the direction finding result of integrated reference signal extraction and coherent direction finding, where the reference signal extraction result of the integrated reference signal extraction and coherent direction finding method is a 1×L order vector.

[0024]

[0025] Among them, w M+1:2M (θ m) represents taking a 2M×1 order bidirectional parallel beamforming vector w(θ) m The M elements following ) form an M×1 vector.

[0026] The beneficial effects of this invention are: by using the integrated reference signal extraction and coherent direction finding method proposed in this invention, when the spatial spectrum direction finding method based on spatial domain processing fails to find the direction of coherent interference source signals, the method can simultaneously determine the reference signal with the known direction of arrival and the coherent direction finding spatial spectrum of the search direction by using bidirectional parallel beamforming of the known direction of arrival and the known direction finding direction of the frequency-using equipment through the antenna array snapshot signal received by the direction finding equipment, thereby improving the probability of coherent signal detection and the accuracy of direction finding. Detailed Implementation

[0027] The practicality of the present invention will be analyzed below with reference to the embodiments.

[0028] Example: In this example, the direction finding device has M = 8 antennas, N = 451 search directions, and a search direction set of {-45.0, -44.8, -44.6, ..., 44.6, 44.8, 45} degrees. The set of direction vectors corresponding one-to-one with the search direction set is {a(-45.0), a(-44.8), a(-44.6), ..., a(44.6), a(44.8), a(45)}. The number of snapshots for the acquisition array is L = 200. Relative to the direction finding device, the known direction of arrival for the frequency-using device is -19.16 degrees, with a signal-to-noise ratio of 48.16 dB; the direction of arrival for the signal to be direction-finded is 20.77 degrees, with a signal-to-noise ratio of -12.04 dB, and the waveform is coherent with the signal waveform transmitted by the frequency-using device. It can be seen that in the array received signals of the direction finding equipment, the power of the incoming signal from the frequency-using equipment is 60.20 dB stronger than the power of the signal to be found.

[0029] The Minimum Variance Distortionless Response (MVDR) and Multi-Signal Classification (MUSIC) direction finding methods can only accurately determine the direction of arrival of the signal from the frequency-using equipment. Since the power of the signal to be measured in the direction-finding equipment's array reception signal is 60.20 dB lower than the power of the strong signal, estimating the direction of arrival of the signal based on the peak positions of the MVDR and MUSIC spatial spectra detected near the weak signal's direction of arrival yields direction finding results of 38.00 degrees and 32.00 degrees, respectively, with direction finding errors of 17.23 degrees and 11.23 degrees, respectively. However, using the method of this invention, the direction finding result for the signal to be measured is 19.40 degrees, with a direction finding error of -1.37 degrees. The correlation coefficient between the reference signal extraction result and the signal from the frequency-using equipment in the direction-finding equipment's array reception signal reaches 98.60%. As can be seen, by using the method of the present invention, through bidirectional parallel beamforming of the known direction of arrival and the search direction of the frequency-using device, the coherent direction-finding spatial spectrum of the reference signal with the known direction of arrival and the search direction can be simultaneously determined using the antenna array snapshot signal received by the direction-finding device, thereby improving the direction-finding accuracy of the coherent signal.

Claims

1. An integrated method for reference signal extraction and coherent direction finding, characterized in that, Includes the following steps: S1. Set the number of antennas of the direction finding device to M, the number of search directions to N, and the search direction to θ. n The set of search directions is {θ1, θ2, ..., θ N }, and the search direction θ n The corresponding direction vector is a(θ) n Let n = 1, 2, ..., N, and the set of all direction vectors be {a(θ1), a(θ2), ..., a(θ...}}. N The direction-finding device receives L snapshots of the array signal, and the known direction of arrival of the frequency-using device is... The corresponding direction vector is The array snapshot signal received by the direction finding equipment is an M×L matrix X; S2. Determine the autocorrelation matrix of the array snapshot signal as R = XX H The data generated by bidirectional parallel beamforming is a 2M×2M order matrix: S3. Determine the linear constraint vector for bidirectional parallel beamforming as follows: Given the known incoming wave direction and corresponding direction vector of the frequency-using equipment, and the search direction θn in the corresponding search direction set, the linear constraint matrix for forming the bidirectional parallel beam is determined as follows: Where n = 1, 2, ..., N; S4. Based on the data matrix, linear constraint vector, and linear constraint matrix formed by the bidirectional parallel beamforming, determine the 2M×1 order bidirectional parallel beamforming vector as follows: w(θ n )=(A(θ n )Q -1 A H (i n )) -1 q Where H represents the conjugate transpose of a vector or matrix, -1 represents the inverse of a matrix, and n = 1, 2, ..., N; S5, each search direction θ in the corresponding search direction set n The coherent direction-finding spatial spectrum for each search direction is determined as follows: Among them, w 1:M (θ n ) represents taking a 2M×1 order bidirectional parallel beamforming vector w(θ) n The first M elements of the vector form an M×1 vector, where || represents the absolute value, and n = 1, 2, ..., N; S6. Determine the set of coherent direction-finding spatial spectra {g(θ1), g(θ2), ..., g(θ)} for the search direction. N The maximum value in )} is the m-th spatial spectral value g(θ) m ), corresponding to the direction θ m This refers to the direction finding result of integrated reference signal extraction and coherent direction finding, where the reference signal extraction result of the integrated reference signal extraction and coherent direction finding method is a 1×L order vector: Among them, w M+1:2M (θ m ) represents taking a 2M×1 order bidirectional parallel beamforming vector w(θ) m The M elements following ) form an M×1 vector.

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