A Three-Stage Inter-Channel Calibration Approach for Passive Radar on Moving Platforms Exploiting the Minimum Variance Power Spectrum

Abstract

Research in passive radar has moved its focus towards passive radar on moving platforms in recent years with the purpose of moving target indication and ground imaging via synthetic aperture radar. This is also fostered by the progress in hardware miniaturization, which alleviates the installation of the required hardware on moving platforms. Terrestrial transmitters, commonly known as illuminators of opportunity in the passive radar community, usually emit the signals in the Very High Frequency (VHF) or Ultra High Frequency (UHF) band. Due to the long wavelengths of the VHF/UHF band, there are constraints on the size of the used antenna elements, and therefore, the number of antenna elements to be employed is limited, especially as the platform carrying the passive radar system is intended to be small, potentially even an unmanned aerial vehicle. In order to detect moving targets hidden by Doppler shifted clutter returns, one common approach is to suppress the clutter returns by applying clutter suppression techniques that rely on spatial and temporal degrees of freedom, such as Displaced Phase Center Antenna (DPCA) or Space-Time Adaptive Processing. It has been shown that the DPCA approach is a meaningful technique to suppress the clutter if two antenna elements are employed. However, if the employed receiving channels are not carefully calibrated, the clutter suppression is shown to be not effective. Here, we suggest a three-stage calibration technique in order to perform the calibration of two receiving channels, which involves the exploitation of the direct signal, a data-adaptive amplitude calibration, and finally, a data-adaptive calibration of phase mismatches between both receiving channels by the estimation of the Minimum Variance Power Spectrum of the clutter. The validity of the proposed approach is shown with simulated data and demonstrated on real data from a fast ground moving platform, showing improved clutter cancellation capabilities.

Parasitic Surveillance Potentialities Based on a GEO-SAR Illuminator

“…Even if passive radar research has been primarily focused on the detection and tracking of airborne and maritime targets exploiting stationary ground-based receivers, in the last few years a great interest has been devoted to airborne passive radar systems as a way to enhance the current potentialities of ground monitoring, surveillance and situational awareness, in both defence and civil scenarios. First, theoretical and experimental results have been presented on passive bistatic radars on board a moving platform, aimed at SAR [40,41] and GMTI applications [42][43][44][45][46]. Digital communication signals from groundbased transmitters have been primarily considered.…”

Dual Cancelled Channel STAP for Target Detection and DOA Estimation in Passive Radar

“…Recent advances in passive radar research have opened interesting new perspectives and application areas [ 1 , 2 , 3 ]. Among them, in the last few years, the potentialities of passive radar mounted onboard moving platforms have been investigated, aiming towards synthetic aperture radar (SAR) imaging [ 4 , 5 , 6 , 7 ] and ground moving target indication (GMTI) [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] applications.…”

“…In [ 8 , 9 , 10 , 11 , 12 , 13 ], an approach based on displaced phase centre antenna (DPCA) was shown to be a particularly attractive and undemanding solution for passive radar applications in the case of dual-channel systems. However, the need to mitigate the potential angle-dependent channel imbalances requires the implementation of adaptive digital calibration strategies, operating across multiple processing stages, for a convenient suppression of direct signal interference and clutter [ 11 , 12 , 13 ]. Moreover, with two channels on receive, only the detection of target echoes can be sought, whereas the problem of its angular localisation within the broad antenna beam remains unsolved.…”