On-Board Doppler Filtering for Data Volume Reduction in Spaceborne SAR Systems

Abstract

High-resolution wide-swath (HRWS) synthetic aperture radar (SAR) systems based on digital beamforming (DBF) in elevation are very attractive for the observation of dynamic processes on the Earth’s surface. However, HRWS systems are inherently associated with a huge data volume. Moreover, in order to comply with azimuth ambiguity requirements, a pulse repetition frequency (PRF) much higher than the required processed Doppler bandwidth is often desirable. The data volume can be drastically reduced, if on-board Doppler filtering and decimation are performed prior to downlink. A finite impulse response (FIR) filter with a relatively small number of taps suffices to completely suppress the additional ambiguous components and recover the original impulse response, provided that the filter’s transfer function is compensated for in the processing. This strategy is also applicable to staggered-SAR systems, where on-board Doppler filtering and resampling can be jointly implemented.