DeCCaF Radar Clutter Homogenization for Spectral Notch Variation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Radar systems face nonstationarity effects during coherent processing due to dynamically changing spectral notches, which hinder clutter cancellation and degrade radar detection performance.
Innovation Solution
The Devoid Clutter Capture and Filling (DeCCaF) approach, which involves bandpass filtering a clutter response from a different pulse with a non-identical notch location and adding it to the current pulse's response to homogenize the spectral content, thereby mitigating nonstationarity effects and enhancing clutter cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spectral notches are dynamically adjusted during CPI to track RFI locations, then interference rejection capability is improved, but nonstationarity effects increase causing degraded clutter cancellation performance
Solution Approach 1:
The clutter cancellation process is segmented into two distinct stages: (1) clutter estimation using only full-band pulses that are free from spectral notching effects, and (2) clutter subtraction from all received pulses including those with spectral notches. This segmentation allows the system to maintain accurate clutter cancellation by using a reference clutter estimate that is not contaminated by time-varying notch effects.
Solution Approach 2:
Full-band pulses serve as an intermediary reference signal that mediates between the need for spectral notching (to reject interference) and the need for stationary clutter characteristics (for accurate cancellation). By using full-band pulses as a reference, the system can estimate clutter without the distortion introduced by spectral notches, and then apply this estimate to cancel clutter from all pulses.
2Object-affected harmful factors
If spectral notches are used to avoid in-band interference, then signal-to-interference ratio is improved, but range sidelobe modulation of clutter increases
Solution Approach 1:
The harmful range sidelobe modulation effect is extracted and isolated to only affect pulses with spectral notches, while full-band pulses remain free from this distortion. By separating the processing of full-band pulses (used for reference) from notched pulses (used for detection), the system removes the detrimental RSM effect from the clutter reference while preserving the interference rejection benefit in the detection pulses.
3Adaptability or versatility
If waveforms with varying spectral notches are transmitted during CPI, then cognitive interference avoidance is improved, but delay-Doppler point spread function distortion increases
Solution Approach 1:
The system performs preliminary action by acquiring and storing full-band reference pulses before or during the CPI period when spectral notches are applied to other pulses. This preliminary reference data is used to establish the undistorted delay-Doppler point spread function characteristics, which then serve as a template for processing the notched pulses and correcting for PSF distortion.
Data Source
AI summary
An ad hoc approach denoted as devoid clutter capture and filling (DeCCaF) that addresses the nonstationarity effects that arise when input radar waveform returns exhibiting dynamic spectra variations are processed to combat dynamic RFI is disclosed. Portions of the spectra of each input waveform return of a set of input radar waveform returns processed during the CPI may be filled with clutter information borrowed from other waveform returns of the set of waveform returns. DeCCaF may combined with an appropriate filter (e.g., a matched filter, a mismatched filter) to achieve results that are nearly indistinguishable from input radar waveform returns in which no spectral variation are present.