Enabling Block-Sparse Recovery in Photonics-Based Radars With Multi-Waveform Transmission

This paper proposes a novel signal composed of multiple quasi-orthogonal waveforms, enabling the use of block-sparse recovery (BSR) in a photonics-based radar system. The radar system is built based on millimeter wave and radio-over-fiber technologies, with a central unit connected to a remote unit via optical fibers. The proposed radar signal is transmitted by the system, and a BSR technique is employed to reconstruct the target scene from the reflected signal. An ambiguity-function shaping algorithm is considered for the design of the new radar signal with good correlation properties. Additionally, an innovative method is proposed for constructing the measurement vector and building the dictionary from the designed quasi-orthogonal waveforms. This construction method reduces dictionary coherence and eliminates the need for a high-speed large-memory analog-to-digital converter at the receiver. Experimental and simulation investigations are conducted to evaluate the performance of the radar system employing BSR under different block sizes and fiber lengths. The root- mean-square error (RMSE) and probability of false alarm (PFA) are used as performance metrics. The results demonstrate that the BSR with the new proposed signal significantly enhances the radar system's resolution compared to the conventional matched filtering method. Furthermore, employing BSR with a block size of 3 reduces the RMSE and PFA by approximately 55% and 83%, respectively, compared to the traditional non-BSR method. The study also shows that optical fibers with lengths up to 80 km can be safely used to carry 28 GHz radar signal without introducing noticeable effects on the system's performance.