Photonic generation of arbitrarily phase-modulated microwave signals based on a single DDMZM.

We propose and demonstrate a compact and cost-effective photonic approach to generate arbitrarily phase-modulated microwave signals using a conventional dual-drive Mach-Zehnder modulator (DDMZM). One arm (arm1) of the DDMZM is driven by a sinusoidal microwave signal whose power is optimized to suppress the optical carrier, while the other arm (arm2) of the DDMZM is driven by a coding signal. In this way, the phase-modulated optical carrier from the arm2 and the sidebands from the arm1 are combined together at the output of the DDMZM. Binary phase-coded microwave pulses which are free from the baseband frequency components can be generated when the coding signal is a three-level signal. In this case, the precise π phase shift of the microwave signal is independent of the amplitude of the coding signal. Moreover, arbitrarily phase-modulated microwave signals can be generated when an optical bandpass filter is attached after the DDMZM to achieve optical single-sideband modulation. The proposed approach is theoretically analyzed and experimentally verified. The binary phase-coded microwave pulses, quaternary phase-coded microwave signal, and linearly frequency-chirped microwave signal are experimentally generated. The simulated and the experimental results agree very well with each other.