Abstract-In this paper, we examine the feasibility of applying Space-Time Adaptive Processing (STAP) to bistatic passive radars using illuminators of opportunity. The transmitters considered are GSM base stations and are non-cooperative. Although STAP has been extensively applied to signals from pulse-Doppler radars, it was never applied to arbitrary signals arising from illuminators of opportunity. We show that by computing the appropriate mixing product, we essentially convert the signal of opportunity to a pulse-Doppler like signal, hence making the application of STAP to arbitrary signals straightforward. We finally confirm these theoretical results by using real measurements.

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.

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In this paper we investigate the feasibility of using Passive Bistatic Radar, PBR, to provide security for a harbour area. There have been numerous publications on the suitability of passive radar for air surveillance applications. However, this paper focuses predominantly on maritime applications. We investigate the ability of passive radar to detect, track, and eventually manage, marine vessels (boats). The paper includes a case-study of the Livorno Harbour in Italy. Livorno has been chosen as it represents a busy maritime hub. Simulations are provided to determine the theoretical radar performance, which are then compared with experimental results from a DVB-T-based passive radar. It will be shown that passive radars represent a viable solution for harbour protection applications

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