Photonic Generation of Chirp-Free Phase-Coded Microwave With Accurate $\pi$ Phase Shift and Large Continuous Operating Bandwidth

This paper presents a novel approach to generate a binary phase-coded microwave signal with accurate π phase shift and large continuous operating bandwidth. In the system, the phase-coding modulation with an accurate π phase shift has been realized by the joint use of two cascaded polarization modulators (PolMs). The generation of phase-coded microwave signals at 10 GHz, 18 GHz, and 28 GHz has been experimentally demonstrated, which verifies the proposed technique positively. Since there is no use of any optical filters and fiber Bragg gratings (FBGs), this system is rather simple and free from the optical bandwidth limitation problem with operating in a continuous microwave bandwidth as large as limited only by the PolMs (from dc to 40 GHz).