Passive Radar FM Signal Processing for Clutter Purification
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Solution Overview
Problem
Passive radar systems face challenges in processing FM signals for detection and location due to complexity and cost, particularly in distinguishing useful signals from direct transmissions, reflections, and spurious signals in a non-cooperating transmission environment.
Innovation Solution
A method involving coherent and non-coherent signal processing steps, including cleansed target pathway formation, reference signal regeneration, cross-ambiguity computation, auto-ambiguity estimation, distance-Doppler extraction, and Doppler-distance purification to isolate and characterize target signals amidst clutter and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive radar systems use FM opportunity signals for detection and location, then the complexity and cost of the radar structure is reduced, but the ability to distinguish useful signals from direct transmissions, reflections, and spurious signals deteriorates
Solution Approach 1:
The patent segments the signal processing into distinct phases: coherent processing (including cleansed target pathway formation, reference signal regeneration, and cross-ambiguity computation) and non-coherent processing (including auto-ambiguity estimation, distance-Doppler extraction, and Doppler-distance purification). This segmentation allows systematic separation and processing of different signal components to distinguish useful signals from clutter and spurious signals.
Solution Approach 2:
The patent introduces intermediary processing steps between signal reception and final detection. These include forming cleansed target pathways by eliminating direct paths and multipaths, regenerating reference signals, and computing cross-ambiguities. These intermediary steps act as mediators that transform the complex mixed signal into processed signals that highlight target information while suppressing unwanted components.
2Measurement precision
If multiple reception pathways are used to improve detection accuracy, then the detection accuracy is enhanced, but the processing complexity increases
Solution Approach 1:
The patent merges multiple reception pathways (V1, V2, ..., VN) through coherent processing to form cleansed target pathways. By combining signals from multiple antennas and applying spatial filtering, the system achieves improved detection accuracy through signal diversity while managing complexity through structured processing algorithms that handle multiple pathways systematically.
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 approach enables effective signal processing for passive radar systems, enhancing detection accuracy and reducing complexity and cost by isolating useful signals from clutter and spurious signals, thereby improving radar coverage without the need for active transmitters.
Implementation Method 1
the signal received by each receiver corresponds at one and the same time to the direct reception of the signal transmitted by the opportunity source (FM transmitter), to the reception of the reflections of this opportunity signal off varied fixed obstacles, these signals possibly being regarded as what the person skilled in the art knows by the name clutter, and to the reception of the 'useful' signals originating from the reflections of this same source by the mobile objects that it is sought to detect
Data Source
AI summary
A signal processing method performs operations of coherent processing making it possible notably to purge the useful signal of the spurious signals (in particular the reference signal and its multiple reflections), to regenerate the transmission signal and to perform a coherent integration of the signal received by computing the cross-ambiguity between the signal received and the regenerated transmission signal. It also performs operations of non-coherent processing making it possible in particular to carry out extraction and Doppler distance purification operations making it possible to form blips and to eliminate the spurious blips present among the blips formed. The method applies notably to passive radars operating on non-cooperating opportunity transmissions, such as FM transmissions intended for the public.