Radar Moving Target Positioning via Phase Difference Mapping
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Solution Overview
Problem
Current SAR-GMTI image generation techniques face challenges in accurately positioning moving targets due to biases in azimuth localization and the inability to discriminate between fixed and moving reflectors, leading to defocused targets and increased clutter, which complicates the detection and resolution of moving targets.
Innovation Solution
A method involving simultaneous acquisition of two radar images on different reception channels, providing phase information, to calculate phase differences and correspond these to pixel positions, allowing for accurate positioning of moving targets without the need for separate SAR and GMTI acquisitions or correction for measurement biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional SAR mode is used to image fixed reflectors, then high-resolution azimuth discrimination is achieved, but moving targets appear at incorrect positions and become defocused due to Doppler frequency measurement biases
Solution Approach 1:
The invention separates the processing of fixed reflectors and moving targets by using two different acquisition modes (SAR and GMTI) and subsequently combining their results. The SAR mode processes fixed reflectors to create a reference image, while GMTI mode detects moving targets, and the moving target positions are then overlaid on the SAR image background.
Solution Approach 2:
The invention introduces a correspondence table as an intermediary that links phase differences from GMTI acquisitions to pixel positions in the SAR image. This correspondence table enables accurate positioning of moving targets by mapping measured phase differences to the appropriate locations on the high-resolution SAR image background.
2Difficulty of detecting and measuring
If GMTI mode is used to detect moving targets, then moving target detection capability is improved, but azimuth resolution deteriorates due to insufficient integration time
Solution Approach 1:
The invention merges the advantages of SAR and GMTI modes by combining their respective outputs. The SAR image provides high-resolution azimuth discrimination for fixed reflectors, while GMTI detections provide moving target information. The final image combines both, placing moving target plots on the SAR image background to achieve both high resolution and moving target detection.
Solution Approach 2:
The invention creates a multi-functional imaging system that can simultaneously provide high-resolution static scene imaging (from SAR) and moving target detection (from GMTI). The combined SAR-GMTI image serves both purposes: it displays fixed reflectors with SAR-level resolution and moving targets with GMTI-level detection capability.
3Adaptability or versatility
If separate SAR and GMTI acquisitions are performed, then both fixed reflector imaging and moving target detection are achieved, but system complexity and acquisition time increase
Solution Approach 1:
The invention performs SAR acquisition first to create a high-resolution reference image of the static scene. This preliminary action establishes the background on which moving targets will later be detected and positioned, avoiding the need to process both modes simultaneously and simplifying the overall system architecture.
4Difficulty of detecting and measuring
If moving targets are detected in conventional SAR mode, then detection is possible, but targets become defocused and energy is diluted due to Doppler ambiguity
Solution Approach 1:
The invention uses a correspondence table as an intermediary to accurately map moving target positions from GMTI phase difference measurements to the SAR image coordinate system. This intermediary enables precise positioning of moving targets without suffering from the defocusing and energy dilution problems that occur in conventional SAR mode.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables accurate, bias-free positioning of moving targets on radar images, reducing clutter and improving detection by focusing energy onto specific pixels, thereby enhancing signal-to-noise ratio and resolution.
Implementation Method 1
a radar fixed on an aircraft 101 illuminates an imaged zone 102
Implementation Method 2
a spectral analysis along the transverse axis 106 carried out on the collected signal makes it possible to discriminate in Doppler the different echoes
Implementation Method 3
calculation step, executed on the basis of the first and of the second radar image, of a correspondence table relating, for a given distance, a measurement of a phase difference between the two reception channels with a position on said radar images
Data Source
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AI summary
The invention relates to a method for positioning a moving target on a radar image. It applies to radar systems comprising at least two reception paths and having electronic means for image processing for calculating a target dephasing value. According to the method, previously detected moving targets are then positioned in a radar image by means of a correspondence table that can associate a position in the image according to a phase difference value. The invention enables images to be obtained with moving elements, the position and movement of which have been characterised by means of a single acquisition phase.