RFI Suppression for Synchronous Impulse Reconstruction UWB Radar Using RELAX

Abstract

This paper focuses on suppression of Radio Frequency Interference (RFI) for ultra-wideband (UWB) radar signals, sampled using the synchronous impulse reconstruction (SIRE) time equivalent sampling scheme. This equivalent sampling scheme is based on the Army Research Lab’s (ARL) efforts to build an ultra-wideband (UWB) radar in forward looking mode that samples returned radar signals using low rate and inexpensive analog-to-digital (A/D) converters. The cost effectiveness off this SIRE UWB radar makes it plausible for actual ground missions for detecting buried explosive devices. However, the equivalent time sampling scheme complicates RFI suppression as the RFI samples are aliased and irregularly sampled in real time. In this paper, the RELAX and multi-snapshot RELAX algorithms are presented as an intermediate step to the previously proposed averaging scheme by the Army Research Laboratory, in order to enhance RFI suppression for this sampling scheme. The proposed suppression technique involves modelling the narrowband RFI signals as a sum of sinusoids and applying the aforementioned algorithms. The RELAX algorithm improves the RFI suppression performance without altering the target signatures compared to AR modelling. The multi-snapshot RELAX algorithm which provides a more accurate sinusoidal model than the RELAX algorithm, improves on the RELAX algorithm in terms of suppression. However, the target signatures are suppressed as the number of sinusoids increases. The analysis of the algorithmsis was performed by using collected sniff (passive) data using the SIRE radar in addition to simulated wide-band echo signals (point target signatures).