Ultranarrow-band synthetic aperture radar imaging for arbitrary flight trajectories

Abstract

We present a novel image formation method for synthetic aperture radar (SAR) using ultra-narrowband continuous waveforms. Considering the high Doppler resolution nature of the ultra-narrowband continuous wave (CW) signals, we refer to the SAR system using ultra-narrowband CW signals as Doppler Synthetic Aperture Radar (DSAR). We first correlate the translated version of the received signal with a scaled or frequency-shifted version of the transmitted signal over a finite time window, and then use microlocal analysis to reconstruct the scene by a filtered-backprojection (FBP) of the correlated signals. We show that the resolution of the image is directly related to the length of the support of the windowing function, the carrier-frequency of the transmitted waveform, and the sampling rate of the aperture. Unlike the previous approaches in the literature, our approach backprojects the correlated received signal onto iso-Doppler curves as opposed to iso-range curves, and takes advantage of the velocity, as well as the acceleration of the antennas in a certain direction to form a high resolution SAR image. Furthermore, it can accommodate arbitrary flight trajectories. We present numerical experiments to demonstrate the performance of the new image formation method.