Monostatic Airborne SAR Using License Exempt WiMAX Transceivers

The well-established low-cost broadband OFDM based wireless systems in license-exempt bands, including worldwide interoperability for microwave access (WiMAX) systems, have drawn considerable attention for radar related applications over the past decade. This paper explores an idea of utilizing Commercial Off-The-Shelf (COTS) WiMAX base stations (BSs) in unlicensed band for monostatic airborne synthetic aperture radar (SAR) application. The OFDM PHY of the WiMAX base station has been redesigned to meet the requirements of airborne stripmap SAR applications. The pulse repetition frequency (PRF) offered by standard WiMAX BSs can neither satisfy Doppler bandwidth nor expand SAR slant range. To increase PRF, we propose an RF front modification by employing WiMAX BSs together with a microwave double-pole-double-throw (DPDT) switch and two absorbing loads. Further, a standard WiMAX BS receiver can be directly used to acquire raw data of targets. Simulation results show the proposed scheme can significantly increase the range with limited transmission power.