Photonic Generation of Binary and Quaternary Phase-Coded Microwave Waveforms with Frequency Quadrupling

A photonic approach to generate a phase-coded microwave waveform with frequency quadrupling is proposed and experimentally demonstrated in this paper. The system consists of a dual-parallel Mach-Zehnder modulator (DPMZM), a phase modulator (PM), a fiber Bragg grating (FBG), an optical coupler, and a photodetector. An optical carrier is modulated by a local oscillator (LO) in the DPMZM, and pure ±second-order sidebands are generated. Then, the two sidebands are separated by the FBG, and one of them is modulated by the coding signal through the PM. Both binary and quaternary phase-coded microwave signals with frequency quadrupling of the LO signal can be generated after detecting the recombined two sidebands. The proposed scheme is verified by experiments; phase-coded microwave waveforms at 24 and 12 GHz are generated by applying 6-and 3-GHz LO signals to the DPMZM, respectively. The pulse compression ratios of the generated waveforms are in good agreement with theoretical value.