Dual-Band Coherent Microwave Photonic Radar Using Linear Frequency Modulated Signals With Arbitrary Chirp Rates

Multi-band radars can obtain more electromagnetic scattering information of targets in complex electromagnetic environments, but they always suffer from complex configurations, small bandwidth, or fixed waveforms. Here, we propose a dual-band coherent microwave photonic radar, which is simple, reconfigurable, and has a wide operational bandwidth. In the proposed system, dual-band linear frequency modulated (LFM) signals with arbitrary chirp rates and adjustable bandwidths are simultaneously generated based on polarization multiplexing, and de-chirp processed using photonic in-phase and quadrature (I/Q) mixing. By fusing the de-chirped signals, ranging and inverse synthetic aperture radar (ISAR) imaging with a resolution that is proportional to the sum of the instantaneous bandwidths of the two bands is realized. In an experiment, the dual-band microwave photonic radar is built to generate and process dual-band LFM signals with different instantaneous bandwidths and chirp rates covering 18.1–23.1 GHz and 22.9–29.9 GHz. De-chirped signals in the two bands are coherently fused, achieving an equivalent bandwidth of 11.8 GHz and a range resolution of 1.31 cm.