Broadband multi-frequency microwave photonic up-conversion with tunable phase shift

Abstract

A broadband multi-frequency microwave photonic up-conversion scheme with a tunable phase shift is proposed and demonstrated based on a cavity-less ultrashort optical pulse source and a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM). In this scheme, the intermediate-frequency (IF) signal is loaded onto the optical frequency comb from a cavity-less ultrashort pulse source via carrier-suppressed double-sideband (CS-DSB) modulation by using a DP-DPMZM and a 90° electric hybrid coupler (HC). Through mutual beating between multi-groups of optical modulation sidebands and multi-tone optical carrier at the photodetector (PD), multi-frequency up-converted microwave signals are obtained after coherent superposition. Meanwhile, the phase of the generated signals can be continuously tuned through varying the bias voltages of the DP-DPMZM. Simulation results show that the multi-frequency up-conversion is with a 3-dB operation bandwidth of 36 GHz and a phase shift tuning range over 360°. Hence, this scheme is a potential candidate to simultaneously realize broadband multi-frequency operation and generate the large-scale tunable phase shift in modern radar systems.