Doppler-DPCA and Doppler-ATI: Novel SAR Modalities for Imaging of Moving Targets Using Ultra-Narrowband Waveforms

This paper introduces two novel imaging modalities: Doppler displaced phase center antenna (Doppler-DPCA) and Doppler along track interferometry (Doppler-ATI). The DPCA and ATI techniques have the distinct advantage of removing the response from stationary targets (clutter). We develop DPCA and ATI techniques in Doppler synthetic aperture radar (Doppler-SAR) paradigm to image moving targets embedded in clutter. Doppler-SAR uses ultra-narrowband continuous waveforms (UNCW) to reconstruct high-resolution SAR images. We consider a two-channel bistatic configuration with a stationary antenna transmitting UNCW and two receiving antennas moving along an arbitrary trajectory in tandem. We introduced the theory for Doppler-DPCA and Doppler-ATI. We derive an interferometric phase model and develop equations of velocity mapping. While conventional wideband SAR DPCA and ATI use range difference, Doppler-DPCA and Doppler-ATI use high-resolution temporal Doppler difference in imaging of moving targets. We present numerical results to demonstrate our theory. These novel modalities can be used for applications requiring high signal-to-noise ratio, long-range, low-power, and low payload such as microsatellites and uninhabited aerial vehicles; passive imaging using sources of opportunity, such as TV and radio stations; and in applications requiring spectrum efficiency.