阅读说明：本技术 一种对静辐射源目标的微弱信号检测并定位的方法 (Method for detecting and positioning weak signal of static radiation source target ) 是由 李万春 郭昱宁 王敏 邹炜钦 王丽 于 2019-09-29 设计创作，主要内容包括：本发明属于目标探测技术领域,具体涉及一种对静辐射源目标的微弱信号检测并定位的方法。本发明提出了一种能显著提高静止目标信号检测概率的方法。首先在信号源可能存在的区域划分搜索格点,计算格点与各雷达的时延与方位角；可以根据方位角信息使用数字波束形成技术得到每个无源雷达接收到的位于格点上的“信号源”的合成信号,再根据时延信息得到各接收机的“信号源”合成信号的互相关谱峰,最后可以使用恒虚警检测方法判断所有“信号源”是否为真正的信号源并同时得到了真正信号源的地理位置信息。(The invention belongs to the technical field of target detection, and particularly relates to a method for detecting and positioning weak signals of a static radiation source target. The invention provides a method capable of obviously improving the detection probability of a static target signal. Firstly, dividing and searching grid points in a possible area of a signal source, and calculating the time delay and azimuth angle of each grid point and each radar; the synthetic signal of the 'signal source' on the lattice point received by each passive radar can be obtained by using a digital beam forming technology according to the azimuth information, the cross-correlation spectrum peak of the 'signal source' synthetic signal of each receiver can be obtained according to the time delay information, and finally, whether all the 'signal sources' are real signal sources can be judged by using a constant false alarm detection method and the geographical position information of the real signal sources can be obtained at the same time.)

1. A method for detecting and positioning weak signals of a static radiation source target is based on a distributed passive radar and is characterized by comprising the following steps:

s1, assuming that the target and the receiver are all located on the XY plane, setting the position coordinates q of the master station₀＝[q_x0,q_y0]^TPosition coordinates q of the slave station_n＝[q_xn,q_yn]^TN-1, where N is the total number of receivers and the m-th array element of the nth receiving station receives x_nm＝[x_nm[1] x_nm[2] … x_nm[K]]M is 1,2,. M, M is the number of array elements of a single receiver, and K is the number of signal points;

s2, dividing the target area into A × B grid points with u coordinates_ab＝[x_a,y_b]^TA, B, 1,2, a, B, calculating the number of delay points of each grid point reaching each receiving stationAnd the cosine of the arrival azimuth angle to each receiving station

s3, assuming that a radiation source exists on the grid point, in order to amplify the signal work of the radiation sourceRate, obtaining a corresponding beamformed signal for each mesh point of each receiving station

s4, assuming there is a radiation source on the grid point, the difference between the time delay of the radiation source signal received by the main station and the other receiving stations is

s5 false alarm probability P determined according to need_FASum prior knowledge noise variance

S6, each grid point corresponds to a detection quantity of

Technical Field

The invention belongs to the technical field of target detection, and particularly relates to a method for detecting and positioning weak signals of a static radiation source target.

Background

Compared with an active radar, the passive radar can not know the prior information of the signal in advance generally, so that some methods for improving the signal-to-noise ratio gain in an active radar system can not be used, and weak signals are difficult to detect; in addition, due to the lack of prior knowledge, a single passive radar can only obtain information such as azimuth angle and arrival time of signals generally, the single passive radar is difficult to complete positioning, and although a plurality of passive radars can realize instantaneous cross positioning through position distribution in space and obtained azimuth angle information, the passive radars also have to be under the premise of being capable of detecting a radiation source target.

Disclosure of Invention

With the gradual development of signal acquisition, transmission and processing technology with ultrahigh sampling rate, the array element signals processed in the analog circuit can be processed on a computer, and the invention provides a method for improving the signal detection probability by fusing the information of multiple passive radars and based on the principles of cross positioning and digital beam forming.

The invention provides a method capable of obviously improving the detection probability of a static target signal aiming at a distributed passive radar system. Firstly, dividing and searching grid points in a possible area of a signal source, and calculating the time delay and azimuth angle of each grid point and each radar; the synthetic signal of the 'signal source' on the lattice point received by each passive radar can be obtained by using a digital beam forming technology according to the azimuth information, the cross-correlation spectrum peak of the 'signal source' synthetic signal of each receiver can be obtained according to the time delay information, and finally, whether all the 'signal sources' are real signal sources can be judged by using a constant false alarm detection method and the geographical position information of the real signal sources can be obtained at the same time.

The technical scheme adopted by the invention is as follows:

a combines the digital beam forming technology, distributed direct positioning method, what said is how to fuse the signal that a plurality of distributed array antennas receive, detect and position the radiation source in the area;

to one by a plurality of observation stationsFor the scene of detecting and positioning each target as an example, firstly, a model is established for a problem scene, and the invention assumes that N receivers are arranged under a passive radar system and are respectively positioned at q_n＝[q_xn,q_yn]^TN is 1,2,. cndot.n; the receiving antenna of the known receiver is modeled as a linear array antenna with M array elements, the spacing between the antenna array elements is d, and the search lattice points are located in the intersection of the main lobes of the antennas of the receivers. Assuming that there is a radiation source target in a lattice point, it is located at t ═ t_x,t_y]^TThe localization model is shown in fig. 1.

Assuming that the signal emitted by the radiation source is denoted as s (t), and the receiving direction of the receiver only has the radiation source signal, the digital signal received by each array element can be modeled as:

wherein

c is the speed of light propagation in air, F_sIs the sampling frequency of the digital signal; assuming noise w between receivers and array elements_mnAre not correlated and have ergodicity, the obedience mean value is 0, and the variance is

(ii) a gaussian distribution of;

then the position is aligned with the grid point t_pq＝[t_p,t_q]^TAs far as possible radiation sources are concerned, the receiver q_nThe raw signal estimate of the possible radiation source where the grid point is located can be found as:

wherein

It can be known from the beam-forming principle that

The maximum beam gain is obtained for the combined signal of the radiation sources, so that the maximum combined signal expression of the radiation sources possibly present at the grid points for the grid point where receiver n is located can be written, where w is_nObedience mean 0 and variance

Gaussian distribution of (a):

the estimated signal cross-correlation of a certain receiving station with any other receiving station can be written as:

in the absence of a radiation source, H₀Assuming a single master-slave correlation value T_nThe mean and variance of (a) are:

E(T_n)＝0

in the absence of a radiation source, H₀Suppose that the following detection quantity T obeys chi-square distribution:

upon determining the false alarm probability as P_FAThe threshold value γ may be determined as:

briefly describing some principles of digital beam forming and distributed direct positioning, the following detailed description describes the specific method described in this patent, and the algorithm path diagram is shown in fig. 2:

s1, assuming that the target and the receiver are all located on the XY plane, setting the position coordinates q of the master station₀＝[q_x0,q_y0]^TPosition coordinates q of the slave station_n＝[q_xn,q_yn]^TN-1, where N is the total number of receivers and the m-th array element of the nth receiving station receives x_nm＝[x_nm[1] x_nm[2] … x_nm[K]]M is 1,2,. M, M is the number of array elements of a single receiver, and K is the number of signal points;

s2, dividing the target area into A × B grid points with u coordinates_ab＝[x_a,y_b]^TA, B, 1,2, a, B, calculating the number of delay points of each grid point reaching each receiving station

And the cosine of the arrival azimuth angle to each receiving station

c is the speed of light propagation in air, F_sIs the sampling frequency of the digital signal;

s3, assuming there is a radiation source at the grid points, a corresponding beam forming signal is obtained for each grid point of each receiving station in order to amplify the signal power of the radiation source

M is the array element number of the antenna, d is the array element spacing of the antenna, and lambda is the carrier wavelength;

s4, assuming there is a radiation source on the grid point, the difference between the time delay of the radiation source signal received by the main station and the other receiving stations isThe cross-correlation spectrum peak of the primary station and the secondary station for the assumed radiation source is

Indicating that the signal is cyclically shifted to the right

A unit;

s5 false alarm probability P determined according to need_FASum prior knowledge noise variance

Obtaining a threshold valueWherein N represents the total number of receivers, M represents the number of array elements of a single receiver, and K represents the number of accumulated signal points;

s6, each grid point corresponds to a detection quantity of

Wherein

To represent

Circularly move to the right

And unit, judging whether the detection quantity of the point is greater than a threshold value gamma, if so, judging that the radiation source exists in the position, and otherwise, judging that the radiation source does not exist.

Compared with single-station autocorrelation detection, the method has the advantages that noises among stations are not correlated, the signal-to-noise ratio of correlated detection quantity is improved, the detection probability can be improved by improving the signal-to-noise ratio under constant false alarm processing, and a target can be positioned by multiple stations; compared with the conventional single-array multi-station combined detection, firstly, the multi-array increases the azimuth angle information of a target, so that the target is not fuzzy under the condition of multi-array double-station detection and positioning, and secondly, the method provided by the invention is based on two-dimensional plane space lattice point search, and the detection probability of detecting the related spectrum peak on the whole is higher under the same false alarm probability.

Drawings

FIG. 1 is a flow chart of an algorithm for distributed multi-array joint detection;

FIG. 2 is a diagram of a distributed multi-array detection and localization model;

FIG. 3 is a diagram of a single-array dual-station detection correlation spectrum of a target signal;

FIG. 4 is a result of detecting a target signal by a single array of two stations;

FIG. 5 is a spectrum diagram of a multi-array dual-station detection correlation of a target signal;

fig. 6 shows the detection result of the multi-array dual-station on the target signal.

Detailed Description

The present invention is described in detail below with reference to specific examples:

the invention utilizes matlab to verify the detection positioning algorithm scheme; the master station, the slave station and the target are assumed to be in a two-dimensional plane; the self positioning errors of the master station and the slave station are not calculated; all measurement errors are assumed to be gaussian distributed assuming that the target is stationary or the moving speed is extremely low.

Assuming that there are two radiation source scout stations located at q₁＝[0,0]^TAnd q is₂＝[100,0]^TThe target is located at u ═ 150,150]^TThe target area is 200km multiplied by 200km, and the distance between grid points is 1 km; the single target is detected and positioned by using a single array double station (without using a digital beam forming method) and a multi-array double station (assuming that 8 arrays are provided), wherein fig. 3 is a related spectrogram for detecting a target signal by using the single array double station, fig. 4 is a related spectrogram for detecting the target signal by using the multi-array double station, and fig. 5 is a detection and positioning result of a radiation source signal by using the multi-array double station.

First, comparing fig. 3 and fig. 5, it can be seen that the spectrum plane of fig. 3 is very rough, while the spectrum plane of fig. 5 is relatively smooth, which indicates that the signal-to-noise ratio of the detected quantity after multi-array processing is greater than that of the single-array detected quantity, and according to the theory, after multi-array processing, the signal-to-noise ratio is improved by M times due to coherent accumulation among signals; then, comparing fig. 4 and fig. 6, a plurality of symmetrical false targets appear in the target detection result of the single-array dual-receiving station, it can be seen from observing fig. 3 that a spectral peak with a smaller value appears at the position where the false target appears, and a false target appears only near the target in the detection result of the multi-array (which is related to the time correlation of the radiation source signal, and can improve the problem that the signal leaks to an adjacent grid point through an average value constant false alarm algorithm to cause the increase of the radiation source target), and due to the increase of the angle information, the result ambiguity does not occur in the dual-station positioning.