Coherent Dual-Band Chirped Microwave Signal Generation With Programmable Chirp Shapes in a Single Phase-Modulated Optical Loop

An approach to generating coherent dual-band chirped microwave signals with programmable chirp shapes is proposed and demonstrated based on a single phase-modulated optical loop and a heterodyne structure. The driving signals applied to the electrooptic phase modulator (PM) are composed of a customized low-frequency waveform and a high-frequency single-tone microwave signal. Consequently, a coherent dual-band chirped optical signal is generated from the phase-modulated optical fiber loop. Therefore, the low-frequency waveform defines the chirp shape of the generated dual-band chirped optical signal, and the high-frequency single-tone microwave signal determines the frequency interval between the two bands. Through heterodyne beating the output dual-band chirped optical signal with an external continuous-wave (CW) laser, coherent dual-band chirped microwave signals with customized chirp shapes can be generated, where the frequency intervals between the two bands, the center frequencies, and the bandwidths of the two bands are reconfigurable. In the experiment, coherent dual-band chirped microwave signals with customized chirp shapes, variable frequency intervals between the two bands, tunable center frequencies, and definable bandwidths are generated. This scheme provides a path to generate coherent broadband chirped microwave signals for cutting-edge multiband radar systems.