Widely Tunable Photonic-Assisted Microwave Phase Shifter Based on Single Polarization Multiplexing Electro–Optic Modulator

We demonstrate an approach to achieve a widely tunable photonic-assisted microwave phase shifter (MPS) based on single polarization multiplexing electro-optic modulator (PM-EOM). The PM-EOM can generate orthogonally polarized and phase coherent optical signals. A phase shifted microwave signal is generated by combining the orthogonally polarized signals and generating the signal in a photodetector. A polarization controller (PC) continuously tunes phase of the recovered microwave signals and ensure its magnitude is constant. Through joint adjusting of the wavelength plates inside the PC before a polarizer, phase of the recovered microwave signal in a frequency range of 1-18 GHz can be fully tuned over 360°. Phase deviation is less than 1.5°. The corresponding magnitude almost remains unchanged. Magnitude deviation is less than 2 dB. Phase drift is less than 4° within 120 s. The motivation of this work lies in the fact that the previously reported MPSs using EOMs are hard to be realized with single modulator without special devices or an optical bandpass filter. The photonic-assisted MPS can be expanded into a phase shifter array with a help of a 1 × N optical coupler, which can be applied in optically controlled beamforming.