Photonics-Assisted Bandwidth-Doubling Dual-Chirp Microwave Signal Generation With Freely-Tunable Central Frequency

A photonics-assisted dual-chirp microwave signal generation scheme is proposed based on electro-optic modulation and heterodyne detection. The dual-chirp microwave signal is generated by heterodyne beating between a dual-chirp optical waveform and a frequency-shifted optical carrier, where the dual-chirp optical waveform is obtained by applying a baseband symmetric-triangle linear frequency modulated signal to a Mach-Zehnder modulator biased at the minimum transmission point, and the frequency-shifted optical carrier is obtained by carrier-suppressed single-sideband modulation in a dual-parallel Mach-Zehnder modulator (DPMZM) with the assistance of an electronic 90° hybrid. The bandwidth of the generated dual-chirp microwave signal is twice of that of the input baseband signal, and the central frequency can be tuned by varying the frequency of the single-tone microwave signal applied to the DPMZM. Both numerical simulation and experiment are carried out to demonstrate the proposed scheme. In the simulation, a dual-chirp microwave signal with a center frequency of 15 GHz and a bandwidth of 6 GHz is generated. In the proof-of-concept experiment, dual-chirp microwave signals centered at 1.5 GHz and with bandwidth of 100 MHz and 200 MHz are generated, which verifies the feasibility of the proposed scheme.