Advances on the Frequency Scan for Time-of-Echo Compression Synthetic Aperture Radar Imaging Mode

The Frequency Scan for Time-of-Echo Compression (f-STEC) imaging mode uses a narrow antenna beam, the steering angle of which is a function of the transmitted frequency. The bandwidth of the system is utilized to scan the beam over the swath from far to near range, resulting in a compression of the echo in the time domain. By distributing the frequency spectrum over the imaged swath f-STEC effectively trades (worsens) range resolution for (improved) swath width and signal-to-noise ratio. This paper de-rives closed mathematical expressions relating the instantaneous frequency to the echo arrival time, which are then used to explore the f-STEC timing and nadir echo constraints. It is shown that this enables imaging under timing constraints that conventional pulsed SAR systems cannot accommodate. Further, based on the echo model, an approach of optimizing the data rate is reported.