Joint synthetic aperture radar and space-time adaptive processing on a single receive channel

Wide-area persistent synthetic aperture radar (SAR) video offers the ability to track ground-moving targets via changes between video frames. A shortcoming is the difficulty in maintaining track when a Doppler shift places moving target returns colocated with strong clutter. We propose to augment a SAR modality with space-time adaptive processing (STAP). The wide-area SAR capability generates a large data rate, stressing on-board processing or a ground station data link; therefore, expansion to multiple radar channels for STAP can present a system bottleneck. Consequently, we adopt a multiple-transmit, single-receive (MISO) architecture that constrains the system data rate for down-link or on-board processing to that of a single antenna SAR system. A frequency division design for quasi-orthogonal transmit waveforms is presented; the approach maintains coherence on clutter, achieves the maximal unaliased band of radial velocities set by the pulse repetition frequency of the system, retains full resolution SAR images, and requires no increase in receiver data rate vis-a-vis the wide-area SAR modality. For N transmit antennas and Ns samples per pulse, the enhanced sensing provides a STAP capability with N times larger range bins than the SAR mode at the cost of O(Ns) increase in computation per pulse.