A Waveform-Encoded SAR Concept Based on a Limited Number of Cyclically-Shifted Chirps

Abstract

Synthetic aperture radar (SAR) is a remote sensing technique capable of acquiring high-resolution images of Earth s surface independent of sunlight illumination and weather conditions. In conventional spaceborne SAR, nadir echo may significantly affect the SAR image quality, if the pulse repetition frequency (PRF) is not properly selected. Waveform-encoded SAR has been introduced to alleviate the constraint in PRF selection by varying the transmitted waveform from pulse to pulse and suppressing the nadir echo within the processing. In particular, cyclically-shifted chirps can be used. This work tackles the issue of reducing the number of required distinct waveforms to reduce system complexity and make the concept viable for implementation. A technique to generate a waveform sequence characterized by a reduced number of distinct waveforms is proposed based on the Eulerian circuit. The nadir echo suppression performance is assessed through simulations using real TerraSAR-X data and a realistic nadir echo model.