Design and validation of a passive radar concept for ship detection using communication satellite signals

In this paper, the feasibility of a bistatic passive maritime surveillance system based on the use of communication satellites as illuminators of opportunity is considered and confirmed experimentally. A theoretical comparison of the characteristics of a radar using Inmarsat and Iridium signals as donors has been performed. The procedure of enhancing the range resolution by coherently combining available scarce active communication channels in the frequency domain is presented with the example of the Inmarsat I-4 satellite broadband global area network signals. Parameters affecting the performance of range-Doppler mapping of a target are investigated based on the analysis of the ambiguity function of the combined signals. An experimental set-up with a stationary passive receiver designed for acquisition and processing of Inmarsat signals is presented and the results are shown. The detection and estimation of radial velocities by reflected Inmarsat signals are presented for the first time. The detected maritime targets ranged in size from a large passenger ferry to a small boat. The potential limitations of the concept are outlined, together with ways to overcome them.