Contents I. Introduction
Synthetic Aperture Radar (SAR) is a well established imaging technique which mitigates the aperture dimension limitation on the cross-range resolution for RADAR systems. This enables the possibility of achieving fine resolutions with antennas that are small enough to be mounted onto ground-based vehicles, aircraft, UAV's, and satellites. In more recent times with an increasing amount of technology using up frequency bands for its system operations, congesting the EM spectrum allocation, there has been an increase in interest into researching the practical uses of passive SAR systems. Passive RADARs are systems that do not transmit, but instead use transmitters of opportunity such as, but not limited to, FM radio, GSM, GNSS, and DVB- T transmitters for the source of their signals [1], [2]. Passive SAR systems offer several advantages over active systems, including lower operating costs, covert operations suitable for military use, and no requirement for specific spectrum allocations. Additionally, the inherent bistatic nature of passive SAR systems provides further benefits, such as the ability to analyse targets from multiple geometries and bistatic angles, leading to a more comprehensive understanding of the target. The disadvantage of passive SAR is there is no control over the transmis-sion parameters, which typically are not designed for SAR operations, and therefore are not optimal for SAR imaging. DVB- T transmitters are one of the promising sources for illuminators in passive bistatic SAR imagining, providing good transmission parameters. DVB- T signals transmit in the UHF band (400 - 800 MHz), this frequency range enables DVB- TSAR to potentially achieve non-line-of-sight detection, and foliage penetrating ability (FOPEN SAR). Each DVB- T channel has a 7.61 MHz bandwidth, providing a mono static range resolution of 19.71 m, however this will degrade with increasing bistatic angle. They also provide a large coverage area with a high radiating power (up to 200 kW), which allows a strong signal to noise ratio (SNR) at large distances.
