Abstract
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.
Highlights
The last decade has seen a surge of research dedicated to investigation of passive coherent location systems (PCL) for detection and tracking of ground, maritime, and airborne targets, mostly using terrestrial broadcasting signals [1]–[5]
For Inmarsat I-4A F4 satellite (Alphasat), which has been used as an IoO in experiments discussed in Section VII, all quantitative parameters might be further corrected taking into account higher total effective isotropic radiated power (EIRP) of 70 dBW, extended downlink bandwidth 1518–1559 MHz, and fourcolor frequency reuse scheme, which will result in a slightly better PFD of –85 dBm/m2 per channel
The side lobes levels of the real and simulated signals differ by 4 dB, in this case, in contrast to the results shown in Fig. 11, the experimental results show lower side lobes than the simulation
Summary
The last decade has seen a surge of research dedicated to investigation of passive coherent location systems (PCL) for detection and tracking of ground, maritime, and airborne targets, mostly using terrestrial broadcasting signals [1]–[5]. The goal of this work is to investigate, experimentally and analytically, the performance of a bistatic passive system for detection and kinematic parameter estimation of maritime targets, based on the use of communication satellites as IoOs. Initial analysis of the ambiguity function (AF) of Iridium and Inmarsat downlink signals with respect to IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS VOL. This paper follows on from that work by describing the actual implementation of such a system, with a discussion of the range-Doppler processing, as well as theoretical and experimental analysis of the IoOs’ AF—alongside this, methods to improve range resolution and reduce side lobes are discussed To validate this implementation experimentally, a comprehensive measurement campaign was conducted for a variety of target types; results of which are presented . Experimental scenarios, measurements, and results are presented and, conclusions are formulated and plans for further work are outlined
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