Target Tracking for Multistatic Radar with Transmitter Uncertainty ∗ Sora Choi, Christian R. Berger, David Crouse, Peter Willett, and Shengli Zhou ECE Department, U-2157, University of Connecticut, Storrs CT 06269 † ABSTRACT We present a target tracking system for a specific sort of passive radar, that using a Digital Audio/Video Broadcast (DAB/DVB) network for illuminators of opportunity. The system can measure bi-static range and range-rate. Angular information is assumed here unavailable. The DAB/DVB network operates in a single frequency mode; this means the same data stream is broadcast from multiple senders in the same frequency band. This supplies multiple measurements of each target using just one receiver, but introduces an additional ambiguity, as the signals from each sender are indistinguishable. This leads to a significant data association problem: as well as the usual target/measurement uncertainty there is additional “list” of illuminators that must be contended with. Our intention is to provide tracks directly in the geographic space, as opposed to a two-step procedure of formation of tracks in (bi-static) range and range-rate space to fuse these onto a map. We offer two solutions: one employing joint probabilistic data association (JPDA) based on an Extended Kalman Filter (EKF), and the other a particle filter. For the former, we explain a “super-target” approach to bring what might otherwise be a three-dimensional assignment list down to the two dimensions the JPDAF needs. The latter approach would seem prohibitive in computation even with these; as such, we discuss the use of a PMHT-like measurement model that greatly reduces the numerical load. 1. INTRODUCTION Passive radar is a bi-static system [5] that uses illuminators of opportunity to detect and track airborne targets. In a bi-static radar, sender and receiver are not co-located; in passive radar radio or television stations take the place of the sender and only the receiver is under control. Our interest is on a target tracking system using passive radar with digital broadcast signals: Digital Audio/Video Broadcast (DAB/DVB) [6,15]. It is important to recognize the difference between passive radar using DAB/DVB versus more traditional systems using, for example, commercial FM stations [12] or television [13]. In the traditional case the receiver observes a “direct blast” of signal followed by replicas representing reflections of the signal off whatever targets (and clutter) may be in the scene. Detection of these replicas is difficult because: • The observations process is continuous in time: there is no “pulse” or “scan” concept as one might find in a traditional surveillance system. • It is tempting to use the “direct” signal as a matched filter, to correlate for potential replicas. However, the signal contains both noise and reflections from the same targets at earlier times: the “known” signal in the matched filter is actually not known. • The reflections are themselves corrupted by the in-band direct-blast signal which is, essentially, noise. That is, the signal to noise ratio (SNR) is necessarily strongly negative. On the other hand, the DAB/DVB signals that we are interested in are orthogonal frequency-division multiplexed (OFDM). OFDM signals are relatively long packets of digital signals (actually, each amongst a large set of several hundred sinusoids modulates its own digital signature) and the target-reflection replicas are generally of a delay that falls well within the packet’s duration. That is, in contrast to the traditional case: * This work was supported by the US Office of Naval Research under contract N00014-09-10613. † Contact: willett@engr.uconn.edu.