GPS-Based Time & Phase Synchronization Processing for Distributed SAR

Distributed synthetic aperture radar (DiSAR), including bi- and multistatic SAR, operates with distinct transmitting and receiving antennas that are mounted on separate platforms. Spatial separation has several operational advantages, such as reduced vulnerability in military applications and increased radar cross section (RCS); which may increase the capability, reliability, and flexibility of future aerospace remote sensing missions. However, in this configuration, there is no cancellation of reference oscillator phase noise as in monostatic cases. There are additional technical problems associated with temporal synchronization of the transmit and receive systems. Therefore, highly accurate time and phase synchronization must be provided. Little work on these challenges has been reported. This paper presents a Global Positioning System (GPS)-based technique for achieving successful time and phase synchronization for DiSAR. This technique offers high-frequency stability. More importantly, residual time synchronization errors may be compensated for with a high-precision range alignment method, and residual phase synchronization errors may be compensated for with a subaperture autofocus algorithm.