Wideband DTV passive ISAR system design

Advanced operational modes for passive radar, including inverse synthetic aperture radar (ISAR), require particular consideration with respect to the receiver hardware. The spatial and spectral diversity of passive illuminators necessitates a wideband system with a large dynamic range beyond the already demanding requirements for single channel system due to direct signal interference. Here, a novel, hybrid high/low side downconversion scheme is shown to maximize the number of illuminators without sacrificing receiver dynamic range. Features of American digital television (DTV) signals are demonstrated along with their impact on passive systems. An extension to the efficient calculation of the range-Doppler surface is presented. This technique preserves integration gain and exceeds the unambiguous range/Doppler tradeoff of conventional pulsed radar systems. Finally, initial experimental ISAR results for a commercial airliner are shown to demonstrate discernible structure using a single 6 MHz DTV illuminator.