DVB-T Passive Radar Signal Processing

This paper provides a detailed overview of the Digital Video Broadcasting Terrestrial (DVB-T) signal structure and the implications for passive radar systems that use these signals as illuminators of opportunity. In particular, we analyze the ambiguity function and explain its delay and Doppler properties in terms of the underlying structure of the DVB-T signal. Of particular concern for radar range-Doppler processing are ambiguities consistent in range and Doppler with targets of interest. In this paper we adopt a mismatched filtering approach for range-Doppler processing. We also recognize that while the structure of the DVB-T signal introduces ambiguities, the structure can also be exploited to better estimate the transmitted signal and channel, as well as any mismatch between transmitter and receiver (e.g., clock offsets). This study presents a scheme for pre-processing both the reference and surveillance signals obtained by the passive radar to mitigate the effects of the ambiguities and the clutter in range-Doppler processing. The effectiveness of our proposed scheme in enhancing target detection is demonstrated using real-world data from an (Australian) 8k-mode DVB-T system. A 29 dB reduction in residual ambiguity levels over existing techniques is observed, and a 36 dB reduction over standard matched filtering; with only a 1 dB reduction in the zero-delay, zero-Doppler peak.

I. Introduction

Passive radars exploit readily available, non-cooperative sources of radio energy as illuminators of opportunity to measure reflections from the environment and targets of interest. Without the need for the deployment and operation of a dedicated transmitter, passive radar systems are significantly less expensive to implement and operate than their conventional counterparts. A key advantage is that with a suitable illuminator available, covert surveillance of an area of interest is possible. Another advantage is derived from the geometry of the passive radar system because it is bistatic. The bistatic radar cross-section (RCS) of a target is different from its monostatic RCS, and this may aid target detection and classification [1].