High-Resolution Microwave Photonic Sparse Imaging Radar

The escalating demand for high-resolution micro- wave imaging in modern applications has driven radar toward wider bandwidths and higher frequencies. Micro- wave photonics emerges as an innovative solution for radar development by surmounting the frequency and bandwidth limitations of conventional electronics. However, using a continuous wideband spectrum for a high-resolution microwave radar is hindered by the increasingly congested spectra. Herein, we propose a novel high-resolution microwave photonic sparse imaging radar that employs sparse spectra and sparse apertures to reconcile the conflict between high resolution and continuous wide bandwidth. A wideband random sparse stepped-frequency chirp signal is generated based on recirculating microwave photonic frequency conversion (MWP-FC) and rapidly preprocessed by photonic dechirping. In addition, a sparse signal recovery method, the convolutionally enhanced smoothed $\ell _{0}$ algorithm, is proposed to process the undersampled dechirped signals resulting from sparse spectra and sparse apertures. This method enhances the local structural features of radar images and achieves robust high-resolution sparse imaging. A practical implementation of radar with a frequency range exceeding 16 GHz while effectively occupying only a 4-GHz spectrum is demonstrated, realizing a range resolution of 8.3 mm. We also demonstrate the feasibility and superiority of high-resolution sparse range imaging and sparse inverse synthetic aperture radar (SAR) imaging, thereby making a substantial contribution to the advancement of microwave imaging and offering promising prospects for applications such as intelligent transport, safety monitoring, and topographic mapping.