A Microwave photonic system for simultaneous frequency mixing and phase shifting

A novel microwave photonic system is proposed to simultaneously perform microwave frequency mixing and phase shifting based on a dual-drive Mach-Zehnder modulator (DDMZM) and an optical filter. In the proposed system, the RF and local oscillator (LO) signals are applied to the two RF ports of the DDMZM, respectively. An optical bandpass filter is followed to suppress one of the LO first-order sidebands. By sending the filtered signals to a photodetector (PD), frequency-converted signals are generated due to the frequency beating between the remained LO first-order sideband and the RF first-order sidebands. By adjusting the DC bias voltage applied to the DDMZM, the phase difference between the LO and RF sidebands will be mapped to the generated frequency-converted signals, thus phase shifting is also realized. An experiment is carried out to demonstrate the proposed system. Results show that the proposed system can simultaneously implement microwave frequency mixing within 10-40 GHz and phase shifting covering 0-360^o, which can find applications in photonic microwave beamforming system.