CN-121978674-A - Multichannel ATI-SAR moving target detection method based on pseudo signal assistance

CN121978674ACN 121978674 ACN121978674 ACN 121978674ACN-121978674-A

Abstract

The invention provides a multichannel ATI-SAR moving target detection method based on pseudo signal assistance. According to the method, firstly, known reference signals with controlled power are synchronously injected into two residual images after self-adaptive clutter suppression, an interference pattern is built again, complex multi-view interference processing is carried out, amplitude and phase detection quantity is obtained, then amplitude and phase detection thresholds are respectively solved based on a constant false alarm criterion, and pixels exceeding the double thresholds at the same time are judged to be moving targets through a two-step detector. The invention derives the detection threshold under the heterogeneous clutter environment, supports the selection of the working mode according to the requirement, and can realize the optimal detection performance under the constant false alarm probability. The invention makes full use of the space degree of freedom and introduces false signal assistance, thereby remarkably improving the detection capability of low signal-to-noise ratio and slow weak moving targets under the heterogeneous strong clutter background.

Inventors

TIAN MIN
ZHANG PEIYUAN
LIANG YANAN
Zeng Huiran
LIAO GUISHENG
HOU WENTAO

Assignees

西安电子科技大学
西安电子科技大学杭州研究院

Dates

Publication Date: 20260505
Application Date: 20260130

Claims (10)

1. A multichannel ATI-SAR moving target detection method based on pseudo signal assistance is characterized by comprising the following steps: step 1, generating echo data of N SAR images, wherein the value of N is equal to the total number of channels of the GMTI synthetic aperture radar system; step 2, constructing two sub-apertures, and generating two residual images by applying adaptive clutter suppression; step 3, injecting a power-controlled pseudo signal into a pure noise area without a target in the residual image; step 4, constructing an L-Look complex interference diagram, and extracting detection amounts of an amplitude test and a phase test; Step 5, designing a two-step moving target detector, determining a detection threshold according to the false alarm rate value, solving the detection threshold and adjusting a detection mode; Step 6, preprocessing the SAR image to be detected in the same manner as in steps 1 to 4, performing first-step detection on the preprocessed image to be detected, screening out pixel points with larger amplitude, performing second-step detection on the screened pixel points, and judging the pixel points detected by the second step as a moving target.
2. The method for detecting a moving target of a multichannel ATI-SAR based on pseudo signal assistance as set forth in claim 1, wherein the two sub-apertures in the step 2 are composed of a front N-1 channel and a rear N-1 channel of the N channel, respectively, wherein the front N-1 channel is the No. 1 channel to the N-1 channel, and the rear N-1 channel is the No. 2 channel to the N channel.
3. The method for detecting a moving target of a multichannel ATI-SAR based on pseudo signal assistance according to claim 1, wherein said generating two residual images by adaptive clutter suppression in step 2 means that adaptive clutter suppression weights are used The image data processing of the two sub-apertures is divided, wherein, Satisfy the following requirements , Representing the conjugate transpose operation.
4. The method for multipath ATI-SAR moving target detection based on false signal assistance according to claim 1, wherein the expression of the power controlled false signal in step 3 is as follows: ; Wherein, the Representing the first residual image The dummy signal injected in each pixel, Which represents a complex gaussian distribution of the particles, Representing the strength of the artificial injected artifact, Representing noise power in residual image, will Is set within the range of (1, 10) to satisfy , Representing a target residual power, which is typically greater than the noise power 10 Times of (3).
5. The method for multipath ATI-SAR moving target detection based on pseudo signal assistance according to claim 4, wherein the L-Look complex interferogram in step 4 is obtained by: ; Wherein, the Representing the first after injection of the power-controlled artifact L-number of views of a pixel, L representing the number of views of the complex interference pattern, Representing the kth pixel in the first residual image The view of the sample is taken of, Representing a kth pixel corresponding to a kth pixel in a second residual image The view of the sample is taken of, Representing a conjugate operation, E [. Cndot ] represents a function for finding the desired value.
6. The method for detecting a moving target of a multichannel ATI-SAR based on the assistance of a false signal according to claim 5, wherein the detection amounts of the extraction amplitude test and the phase test in step 4 are obtained by the following formula: ; Wherein, the And Respectively represent the first The detected amounts of the amplitude test and the phase test of the individual pixels, And Respectively represent the first Normalized interference magnitude and phase values of the L-view complex interferograms of the individual pixels, The modulus of the complex number is represented, Representing taking the phase angle of the complex number.
7. The method for detecting a moving object of a multichannel ATI-SAR based on the assistance of a false signal according to claim 6, wherein said step of designing a two-step moving object detector in step 5 is as follows: first, the moving object detector is constructed from the detected amounts of the amplitude test and the phase test that have been obtained according to the following formula And When the following formulas are respectively satisfied, the current pixel point is judged to be a moving target: ; Wherein, the And Threshold values respectively representing the detected amounts of the amplitude test and the phase test; Second, a hypothesis is obtained according to the following formula Lower part(s) And Correlation coefficient between : ; Wherein, the Indicating that there is no target in the detection; third, the effective vision number is obtained according to the following formula : ; Wherein, the Representing an operation of taking the real part of the complex number, Expressed in natural constant As a function of the base of the exponentiation, Representing imaginary unit symbols; Fourth, the following estimates are obtained from the echo data samples according to the following equation: ; Wherein, the And The degree of freedom and the shape parameters of the inverse chi-square distribution are respectively represented, And Respectively represent pairs of And Is used for the estimation of the (c), 、 Representing the detected quantities t of the amplitude test and the phase test, respectively The moment of the order of the magnitude, , , Representing a Beta function; Fifth, generating a hypothesis according to the following formula in the clutter background Lower part(s) And Is a joint probability density function of: ; Wherein, the Representing the estimated average interference phase, typically , The circumference ratio is indicated as such, Representing the gamma function of the gamma ray, Representing a gaussian super-geometric function, Representing the detected quantity of the amplitude test A kind of electronic device To the power of the method, Representing a cosine function; sixth, obtaining a detection threshold value of the two-stage moving target detector under the specified false alarm rate according to the following formula: ; Wherein, the Representing false alarm rate, at a specified point Solving two or more groups of detection threshold combinations 。
8. The method for detecting a moving target of a multichannel ATI-SAR based on the assistance of a false signal according to claim 7, wherein the step of solving the detection threshold and adjusting the detection mode in step5 is as follows: First step, based on preset constant false alarm rate Index, using derived interferogram statistical distribution model to establish amplitude threshold And a phase threshold Is a constraint relation equation of (2); step two, solving the constraint relation equation to obtain a plurality of groups of combination pairs of amplitude threshold values and phase threshold values which meet the same constant false alarm rate ; Thirdly, selecting detection modes according to actual task demands, and detecting threshold values of different groups Corresponding to different detection modes, selecting the combined centering amplitude threshold value when the detection task is low signal-to-noise ratio target detection Smaller and phase threshold A larger group is used as the parameter of the amplitude priority mode, and when the detection task is slow target detection, the phase threshold value in the combination pair is selected Smaller and amplitude threshold A larger set, as parameters for the amplitude priority mode.
9. The method for detecting a moving target of a multichannel ATI-SAR based on pseudo signal assistance according to claim 7, wherein the first step of detecting the preprocessed image to be detected in step 6 means that the amplitude value of each pixel point in the preprocessed image to be detected is compared with a threshold value of the amplitude test detection amount Comparing the amplitude value to be smaller than the threshold value The pixel points are all determined as background pixels.
10. The method for detecting moving targets of multi-channel ATI-SAR based on pseudo signal assistance according to claim 8, wherein the second step of detecting the selected pixel in step 6 means that the phase value of the selected pixel and the threshold value of the detected amount of the phase test Comparing to a phase value less than a threshold Is determined as the pixel of the moving object.

Description

Multichannel ATI-SAR moving target detection method based on pseudo signal assistance Technical Field The invention belongs to the technical field of radars, and further relates to a multichannel along-track interference-synthetic aperture radar ATI-SAR (Along-Track Interferometry-SYNTHETIC APERTURE RADAR) moving target detection method based on false signal assistance in the technical field of radar target detection. The method can be used for detecting low signal-to-noise ratio low-speed small targets under the non-uniform strong clutter background in the ATI-SAR system. Background The ATI-SAR system realizes multi-frame SAR image observation of the same scene by configuring two or more SAR imaging channels in the direction of a platform motion track, and is a special form of a multi-channel SAR system. Compared with a single-channel system, the multichannel system increases the spatial freedom degree of signals, and can effectively inhibit clutter, so that the detection performance of a moving target under low signal-to-noise ratio is improved. However, under the non-uniform clutter background, the situation that clutter residual error and noise coexist still can occur after the ATI-SAR system is subjected to adaptive clutter suppression, and serious influence is generated on target detection. In the prior art, the multichannel ATI-SAR system is still insufficient in the aspect of space domain degree of freedom utilization, and particularly, under the non-uniform strong clutter background, the detection of a slow target under a low signal-to-noise ratio is still difficult. C.H. Gierull, I. Sikaneta et al, published paper "Two-step detector for RADARSAT-2' s experimental GMTI mode”(IEEE Transactions on Geoscience and Remote Sensing, vol. 51, no. 1, Pp. 436-454, 2013) to provide a two-step detection method. The method comprises the steps of firstly, performing primary detection on the SAR image by adopting signal amplitude information based on multichannel adaptive clutter suppression in the first stage, then performing second-step detection on the SAR image by utilizing two channels along the track interference ATI phase, and finally performing logical AND on the detection result. However, the method still has the defects that the ATI phase detection statistic in the second step of detection only uses two channel echo data, the space domain degree of freedom is wasted for a multi-channel radar system, and the ATI phase statistic has serious deterioration of estimation performance under the condition of low signal to noise ratio, so that the detection performance is not stable under the strong clutter background. In the patent literature 'a moving target detection method of optimal fusion of multichannel ATI-SAR under a strong clutter background' (application number: 2024119027902, authorized bulletin number: CN 119846626B) applied by the university of Western-style electronic technology, a detection method based on an optimal fusion detector is proposed for an onboard multichannel ATI-SAR system. The method comprises the steps of firstly carrying out local detection by utilizing a group of multi-baseline clutter removal ATI phase test and AMF amplitude test, and then designing global detection optimization and carrying out global detection based on an optimal fusion rule. However, this approach still suffers from the disadvantage that it does not maximize the spatial freedom of using the multi-channel synthetic aperture radar system, so that there may still be a strong clutter residual after adaptive clutter suppression. When the target signal and clutter coexist, the ATI phase estimation becomes unreliable, resulting in an increase in minimum resolvable SCNR, causing a decrease in detection performance. M. Tian, B. Liao, paper published therein, "Interferometric Phase of Clutter-Suppression Residuals Aided A moving object detection method using an additional degree of spatial freedom (DoFs) is proposed in Multichannel SAR-GMTI, "(IEEE Transactions on Geoscience and Remote Sensing, pp. 1-16, 2025). The method uses the residual amplitude of the adaptive clutter suppression output, combines the residual amplitude with the interference phase calculated between the two clutter suppression residuals from the front and rear groups of channels, and enhances the contrast between the target and the background to a certain extent, thereby realizing the improvement of the detection performance. However, this approach still suffers from the disadvantage that since most residuals approximate the noise signal without moving objects, the interference phase of the noise tends to be randomly distributed within [ -pi, pi ]. Thus, during phase-based detection, the presence of these noises competes with the real target, resulting in a degradation of the performance of the method. Disclosure of Invention The invention aims to solve the problems of insufficient utilization of the degree of freedom of a hollow domain and diffic