Optimum Target Detection using Illuminators of Opportunity

Abstract

Unlike classical bistatic radars, passive radars make use of illuminators of opportunity to detect targets and to estimate target parameters. One existing radio transmission suitable for passive radar operation is the Global System for Mobile Communication (GSM).For non-cooperative bistatic configurations, one of the major difficulties is the estimation of the reference signal which is required to perform detection. This reference signal, a priori unknown, can be extracted from the signal received at the antenna array provided the direction of arrival of the direct path signal is known.Conventional matched-filter based Doppler filtering offers the possibility of placing the target and interferences in a domain where they can be separated based on Doppler shift. However, slow moving targets residing near mainbeam clutter in the rangeDoppler diagram, remain difficult to detect. Internal Clutter Motion (ICM) exacerbates this issue by spreading the clutter signal power in Doppler frequency.In this paper, we first present a method to estimate autonomously the direction of the illuminating GSM base station from measurements obtained with a two-element antenna array. We passively detect the azimuth of the transmitter without a priori knowledge of the environment. Spatial processing is then employed to attenuate the direct path signal and mitigate its influence on the target detection process. We then propose two methods able to cope with clutter echoes with non zero-Doppler components. We first propose an extension of a CLEAN-like algorithm. We also propose to extend adaptive matched filters to noise-like signals. The adapted matched filter can be used to suppress strictly static clutter but also clutter affected by ICM. These methods are validated by using actual clutter measurements obtained from a passive radar using a GSM base station as illuminator of opportunity.

Motion parameter estimation of multiple ground moving targets in multi-static passive radar systems

“…Several advanced signal processing techniques, including time-frequency analysis, motion compensation, and range migration compensation (e.g., [8][9][10]), have been developed for the detection and parameter estimation of moving targets based on their Doppler signatures. However, limited work has been done in estimating target motion parameters in MPR systems (e.g., [11,12]). In this paper, we investigate the problem of motion parameter estimation of ground moving targets in a multi-static passive airborne radar.…”

Space-Time Adaptive Cancellation in Passive Radar Systems

“…The beampattern is evolved by these kinds of algorithms in a way that it places nulls in the direction of high power interferences that are uncorrelated with the desired signal. The operation of these algorithms is widely inspected in passive radar scenarios [2][3][4][5][6][7][8][9].…”

Fpga Implementation of Space-Time Adaptive Processing (Stap) Algorithm for Target Detection in Passive Radars

“…A second antenna captures the reflected signal from target. These two signals are processed together for target detection using match-filtering like cross-ambiguity processing [8,9,16,23].…”

“…This type of advance system gives additional capabilities like digital beamforming and advance adaptive filtering for target detection and clutter rejection [9,19,20]. One of the candidate adaptive algorithm for this kind of radar processing is joint space-time adaptive processing (STAP).…”

“…A limited research exists on using STAP for a passive radar system. One such system and algorithm is presented in [8,9], which uses a receiver setup of two antenna system to capture the signal of interests. Further research was conducted in an attempt to develop a more advanced receiver setup like ULA [1,2] and UCA [6,19,20].…”