Nonlinear Radar Matched Filter for Clutter Rejection
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Solution Overview
Problem
Modern radar systems face challenges in detecting smaller targets due to indistinguishable radar signatures from clutter, particularly when clutter objects produce large linear responses, making it difficult to differentiate between targets and natural objects like trees and rocks.
Innovation Solution
The implementation of non-linear radar using a matched filter that generates an exponential function of the transmit waveform to isolate specific harmonics of the target response, allowing for improved detection and ranging capabilities by correlating the received signal with an expected target response signature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear radar systems are used to detect targets, then the radar can detect targets with sufficient signature differentiation, but large returns from stationary clutter objects (trees, rocks) obscure slow-moving targets and make it difficult to distinguish them from clutter
Solution Approach 1:
The patent changes the fundamental parameter of radar signal interaction by transitioning from linear to non-linear radar processing. The system transmits a non-linear waveform and processes the received signal through non-linear operations (such as squaring or cubing the signal) to generate harmonic frequencies. This parameter change allows the radar to exploit the non-linear response characteristics of targets, creating a new frequency domain where target responses are distinguishable from linear clutter responses, thereby resolving the contradiction between target detection accuracy and clutter interference
Solution Approach 2:
The patent segments the radar signal processing into distinct frequency components by utilizing harmonic generation. The non-linear processing separates the target response into multiple harmonic frequencies (2f, 3f, etc.), allowing the system to analyze and process different frequency components independently. This segmentation enables the radar to isolate target signatures from clutter by focusing on specific harmonic frequencies where target responses are enhanced relative to clutter, thus improving target detection accuracy while reducing clutter interference
2Measurement precision
If modern SAR systems are used to achieve high resolution imaging, then detailed imagery of the scene is produced, but smaller targets (a few inches in diameter) produce radar signatures indistinguishable from the clutter background
Solution Approach 1:
The patent applies non-linear signal processing to transform the radar signature characteristics. By transmitting non-linear waveforms and processing received signals through non-linear operations, the system generates harmonic frequencies that enhance the distinguishability of small target signatures from clutter. This parameter change in signal processing methodology recovers information about small targets that would otherwise be lost in the clutter background, even while maintaining high imaging resolution
3Speed
If Doppler phenomena are exploited for moving target detection, then moving targets can be detected, but large returns from stationary clutter objects obscure slow-moving targets and limit the minimum detectable velocity
Solution Approach 1:
The patent transitions from traditional Doppler-based velocity detection (one-dimensional frequency analysis) to non-linear harmonic analysis, adding a new dimension to the detection process. By generating and analyzing multiple harmonic frequencies from non-linear signal processing, the system creates additional frequency domains where slow-moving targets can be detected despite the presence of stationary clutter. This dimensional expansion in signal processing allows the radar to detect targets with velocities below the traditional minimum detectable velocity limit imposed by clutter lobe width
Data Source
AI summary
Embodiments of the present invention concern locating targets using non-linear radar with a matched filter which uses exponential value of the transmit signal. According to embodiments, a method of non-linear radar target location includes: transmitting a signal of a transmit waveform towards a target; receiving a signal from the target; creating a matched filter by generating an exponential function of the transmit waveform corresponding to a particular harmonic of the interest; and applying the matched filter to the received signal to generate and output a signature waveform for the target of the particular harmonic of interest. In other embodiments, the matched filtering may be combined with sidelobe reduction.