A Photonics-Enhanced Bistatic High-Resolution Wide-Swath Synthetic Aperture Radar System Concept

Kurzfassung

This paper presents a novel concept for implementing a high-resolution wide-swath (HRWS) bistatic synthetic aperture radar (SAR) system using photonics in conjunction with the MirrorSAR concept. MirrorSAR is a bi- or multistatic SAR concept where the platforms are separated in transmit and receive. The simplified receive satellites, acting as space transponders for the echo signal, have highly reduced weight, size and power requirements leading to lower costs. This MirrorSAR setup can be used for gapless HRWS imaging when illuminating the swath by a wide-angle high duty-cycle chirp and a high pulse-repetition frequency while the receiving platform generates multiple beams to collects the echoes. Here, photonics can replace many system functions, including the optical beamforming networks (OBFN) allowing for the generation of multiple wideband beams without a significant impact on the receive platform computation and memory requirements. The OBFN outputs are multiplexed on the same channel using wavelength-division multiplexing, enabling the signal to travel back to the transmit platform via a free-space optical (FSO) link, where the beams are demultiplexed and coherently downconverted and digitised. An example architecture of such a system with the spectrum at selected points is presented assuming a phase shifter Blass matrix based OBFN in conjunction with a phased-array-fed reflector. Aside from additional discussion on optical frequency comb generation, beamforming network options and the FSO link, it is also shown how the concept can be straightforwardly expanded into a multistatic SAR constellation. Finally, an outlook on further simulations and a more in-depth example system with associated performance calculations is provided.