An Ultra-Wideband Microwave Photonic Phase Shifter With a Full 360 $^{\circ}$ Phase Tunable Range

A novel photonic approach to the implementation of an ultra-wideband microwave phase shifter is proposed and experimentally demonstrated. In the proposed system, a single-sideband (SSB) signal is sent to a polarization-maintaining fiber Bragg grating (PM-FBG), which has two spectrally separated transmission notches along the fast and the slow axes. By locating the optical carrier along the fast axis at the transmission notch, the optical carrier in the SSB signal is removed. At the output of the PM-FBG, two orthogonally polarized optical signals, one with the optical carrier and the sideband, the other with only the sideband, are obtained. The two orthogonal signals are then sent through a variable retardation plate (VRP) to a polarizer and then detected by a photodetector. By controlling the VRP to introduce a tunable phase difference between the two orthogonally polarized SSB signals, a microwave signal with a tunable phase shift is generated. A theoretical analysis is developed, which is validated by an experiment. A microwave phase shifter with a full 360° phase shift over a frequency range from 10 to 40 GHz is demonstrated.