A method for fast evaluation of direction finding results in strong signal background

Abstract

The present application belongs to the field of radio direction finding, and particularly relates to a method for quickly evaluating direction finding results in a strong signal background. The present application determines the array receiving fast snap signal of the direction finding device, the spatial spectrum of the conventional beam forming, the highest spectrum peak of the spatial spectrum, i.e. the main peak height and direction; then determines the number of spectrum valleys of the spatial spectrum appearing in pairs on the left and right of the main peak direction of the spatial spectrum and the height of each spectrum valley of the spatial spectrum; then determines the highest spectrum valley direction of the spatial spectrum and the highest spectrum valley height of the spatial spectrum; finally, the spectrum valley difference characteristics of the spatial spectrum are determined from the highest spectrum valley height of the spatial spectrum and the height of the spectrum valley of the spatial spectrum which is symmetrical to the highest spectrum valley of the spatial spectrum with respect to the main peak direction of the spatial spectrum, the spectrum valley difference characteristics of the spatial spectrum are compared with the confidence threshold, the direction finding result is quickly evaluated, and whether the weak signal exists is determined.

Description

Technical Field

[0001] This invention belongs to the field of radio direction finding, specifically relating to a method for rapid evaluation of direction finding results under strong signal background, and more specifically, a method for rapidly determining the existence of weak signals by using the spectral valley characteristics of the spatial spectrum as confidence features. Background Technology

[0002] In passive radio direction finding scenarios where long-range weak signals and short-range strong signals are mixed in time and frequency, or where strong direct wave signals from external radiation sources and weak echo signals reflected from targets are mixed, the problem of weak signals being difficult to detect and locate often arises. Detecting weak signals against a strong signal background is a crucial prerequisite for most current radio direction finding technologies. Although the detection and direction finding capabilities of direction finding equipment can be improved by increasing the number of antennas in the antenna array, antenna gain, and the number of snapshots of the received signal, the effectiveness is limited by factors such as the hardware cost, size, weight, and power consumption of the direction finding equipment.

[0003] Currently, many methods utilize the eigenvalues ​​or singular values ​​of the covariance matrix of the received signal from an antenna array to detect the number of signals. However, these methods are computationally intensive and struggle to reliably detect weak signals. A simpler approach is to evaluate radio direction finding results using the spectral peak characteristics of the spatial spectrum. For example, the height of the highest spectral peak, and the ratio of the first to second highest spectral peak heights, can be used as confidence features to evaluate the direction finding results of conventional beamforming. The conventional beamforming direction finding result is accepted only when these ratios exceed a corresponding threshold; otherwise, it is rejected, and a multi-signal direction finding process with higher detection and direction finding performance but greater computational requirements is initiated. In strong signal environments, using the spectral peak characteristics of the spatial spectrum as confidence features for evaluating radio direction finding results generally guarantees acceptance for strong signals, but it struggles to detect weak signals.

[0004] To evaluate direction finding results for strong signals while simultaneously detecting weak signals, a more complete spatial spectrum feature is needed as a confidence indicator for evaluating radio direction finding results. Taking the spatial spectrum of conventional beamforming as an example, first, the position of the main peak of the spatial spectrum is determined. Then, the number and height of the symmetrical side peaks on both sides of the main peak are determined. Next, the highest side peak and its height are determined. Finally, the peak difference feature of the spatial spectrum is determined by the height of the highest side peak and the height of another side peak symmetrical to the highest side peak relative to the main peak. The peak difference feature of the spatial spectrum is then compared with a confidence threshold to quickly evaluate the direction finding results and determine whether a weak signal exists. However, under low signal-to-noise ratio conditions, it is difficult to simultaneously achieve the requirements of high weak signal detection probability and low false alarm probability when using the peak difference feature of the spatial spectrum to evaluate radio direction finding results. Summary of the Invention

[0005] This invention addresses the problem of how to quickly determine the presence of weak signals in a strong signal background. It utilizes the spectral valley characteristics of the spatial spectrum of conventional beamforming as a confidence feature to rapidly evaluate the spatial spectrum direction finding results of conventional beamforming. This achieves the goal of increasing the detection probability when weak signals are present and reducing the false alarm probability when weak signals are absent in a strong signal background.

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

[0007] A rapid evaluation method for direction finding results under strong signal backgrounds is proposed. First, the number of antennas, the number of search directions, the set of search directions, the set of direction vectors corresponding to the search direction set, the number of snapshots of the direction finding array received by the direction finding equipment, and a confidence threshold are set. Second, the spatial spectrum of the array received snapshots, the spatial spectrum formed by conventional beamforming, and the height and direction of the highest spectral peak (main peak) of the spatial spectrum are determined. Then, the number of spectral valleys and the height of each spectral valley are determined, symmetrically paired on both sides of the main peak direction. Next, the direction and height of the highest spectral valley are determined. Finally, the spectral valley difference characteristics of the spatial spectrum are determined by the height of the highest spectral valley and the height of the spectral valley symmetrical to the main peak direction. These spectral valley difference characteristics are compared with the confidence threshold to rapidly evaluate the direction finding results and determine the presence of weak signals.

[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 number of snapshots of the direction finding equipment's array received signal is L;

[0010] S2. Determine that the array receiving snapshot signal of the direction-finding equipment is an M×L matrix X, and the spatial spectrum formed by the conventional beam in the nth direction is...

[0011] g(θ n )=||a H (θ n )X|| 2

[0012] Where |||| is the norm of the vector,H For the conjugate transpose of a vector, n = 1, 2, ..., N; in the spatial spectrum set {g(θ) n In the sequence {n = 1, 2, ..., N}, the spatial spectrum with the maximum value in the p-th direction is determined, which is also the height of the highest spectral peak, i.e., the main peak, denoted as g(θ). p ), where θ p The direction corresponding to the highest spectral peak in the spatial spectrum, i.e., the main peak;

[0013] S3. If the spatial spectrum of a direction is smaller than the spatial spectra of the two adjacent directions before and after it, then the spatial spectrum of that direction is determined to be a spectral valley, and the direction of the main peak of the spatial spectrum θ is determined. p The number of spectral valleys appearing symmetrically on both sides is Q, and the height of the q-th spectral valley next to the main peak of the spatial spectrum is g(θ). p+q ), q=±1,±2,...,±Q, where, θ p+q The direction of the q-th spectral valley;

[0014] S4, in the set {g(θ) p + q ); q =±1,±2,...,±Q}, the highest spectral valley in the spatial spectrum is determined to be the v-th spectral valley next to the main peak of the spatial spectrum, with a height of g(θ). p+v ), where θ p+v The direction of the highest spectral valley in the spatial spectrum;

[0015] S5. Determine the spectral valley difference characteristics of the spatial spectrum by the height of the highest spectral valley in the spatial spectrum and the height of the spectral valley in the spatial spectrum that is symmetrical to the direction of the main peak of the spatial spectrum. This difference is represented by g(θ). p+v )-g(θ p-v The method compares the spectral valley difference characteristics of the spatial spectrum with the confidence threshold to quickly evaluate the direction finding results: when the spectral valley difference characteristics of the spatial spectrum are less than the confidence threshold, it is determined that there is no weak signal; when the spectral valley difference characteristics of the spatial spectrum are greater than the confidence threshold, it is determined that there is a weak signal.

[0016] The beneficial effects of this invention are: by using the spectral valley characteristics of the spatial spectrum of conventional beamforming as confidence features, the spatial spectrum direction finding results of conventional beamforming can be rapidly evaluated. This can improve the detection probability when weak signals are present and reduce the false alarm probability when weak signals are absent in the background of strong signals. It is suitable for passive radio direction finding situations such as when long-range weak signals and short-range strong signals are mixed in time and frequency, and when strong direct wave signals from external radiation sources and weak echo signals reflected from targets are mixed. Detailed Implementation

[0017] The practicality of the present invention will be analyzed below with reference to the embodiments.

[0018] Example: In this example, the direction finding device has M = 8 antennas, N = 181 search directions, and a set of search directions {-90, -89, ..., 89, 90} degrees. The set of direction vectors corresponding to each search direction is {a(-90), a(-89), ..., a(89), a(90)}. The array snapshot number L = 128 is collected by all antennas of the direction finding device during each direction finding operation. The direction of arrival for strong signals is -4.60 degrees with a signal-to-noise ratio of 40dB, and the direction of arrival for weak signals is 35.16 degrees with a signal-to-noise ratio of 0dB.

[0019] Utilizing spectral peak differences, when the confidence threshold is set to 0.29e-5, the false alarm probability for weak signals is 5.00%, and the detection probability is 8.02%. When the confidence threshold is set to 0.61e-5, the false alarm probability is 94.75%, corresponding to a weak signal detection probability of 95.00%. However, using a rapid direction-finding result evaluation method under strong signal backgrounds, utilizing spectral valley differences, when the confidence threshold is set to 0.32e-5, the false alarm probability for weak signals is 5.00%, and the detection probability is 93.13%. When the confidence threshold is set to 0.19e-3, the weak signal detection probability is 95.00%, and the false alarm probability is 7.76%. This achieves the goal of rapid evaluation of direction-finding results and weak signal detection under strong signal backgrounds.

Claims

1. A method for rapid evaluation of direction-finding results under strong signal background, characterized in that, Includes the following steps: S1. Set the number of antennas in the direction finding device to M, the number of search directions to n, and the set of search directions to {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 number of snapshots of the direction finding equipment's array received signal is L; S2. Determine that the array receiving snapshot signal of the direction finding equipment is an M×L matrix X, and the spatial spectrum formed by the conventional beam in the nth direction is: g(θ n )=||a H (i n )X|| 2 Where ||| is the norm of the vector, H is the conjugate transpose of the vector, and n = 1, 2, ..., N; in the spatial spectrum set {g(θ) n In the sequence {n = 1, 2, ..., N}, the spatial spectrum with the maximum value in the p-th direction is determined, which is also the height of the highest spectral peak, i.e., the main peak, denoted as g(θ). p ), where θ p The direction corresponding to the highest spectral peak in the spatial spectrum, i.e., the main peak; S3. If the spatial spectrum of a direction is smaller than the spatial spectra of the two adjacent directions before and after it, then the spatial spectrum of that direction is determined to be a spectral valley, and the direction of the main peak of the spatial spectrum θ is determined. p The number of spectral valleys appearing symmetrically on both sides is Q, and the height of the q-th spectral valley next to the main peak of the spatial spectrum is g(θ). p+q ), q=±1,±2,…,±Q, where, θ p+q The direction of the q-th spectral valley; S4, in the set {g(θ) p+q In the range q = ±1, ±2, ..., ±Q}, the highest spectral valley is determined to be the v-th spectral valley next to the main peak of the spatial spectrum, with a height of g(θ). p+v ), where θ p+v The direction of the highest spectral valley in the spatial spectrum; S5, the height of the highest spectral valley in the spatial spectrum, g(θ) p+v The height g(θ) of the spectral valley in the spatial spectrum that is symmetrical about the direction of the main peak of the spatial spectrum with respect to the highest spectral valley. p-v ), determine the spectral valley difference characteristics of the spatial spectrum, as g(θ) p+v )-g(θ p-v The method compares the spectral valley difference characteristics of the spatial spectrum with a preset confidence threshold to quickly evaluate the direction finding results: when the spectral valley difference characteristics of the spatial spectrum are less than the confidence threshold, it is determined that there is no weak signal; when the spectral valley difference characteristics of the spatial spectrum are greater than the confidence threshold, it is determined that there is a weak signal.