Abstract: In order to overcome the limitations of traditional radio frequency self-interference cancellation (SIC) technology due to electronic bottlenecks such as frequency, bandwidth, and resistance to electromagnetic interference, and to meet the development needs of future wireless communication and radar systems, a microwave photonic self-interference cancellation scheme based on polarization multiplexed Mach-Zehnder modulator (PDM-MZM) is proposed. This scheme introduces a reference signal that is of the same frequency, amplitude, and phase as the self-interference signal and directly cancels it in the optical domain. Besides self-interference cancellation and down conversion functions, this scheme can also be used for IQ demodulation of vector signals. During IQ demodulation, the polarization controller in both channels can be flexibly adjusted to make the amplitude of the IQ signals strictly equal and the phase strictly orthogonal, thereby eliminating the impact of IQ amplitude imbalance on the receiving end of the full duplex system. Theoretical analysis and simulation testing were conducted in the article, and the results showed that the elimination depth of self interference signals can reach over 72 dB, and the SFDR of the system can reach 95.2 dB·Hz ^2/3, with a gain of －16.2 dB. This scheme has advantages such as large bandwidth, tunability, strong resistance to electromagnetic interference, small size, and low loss, and has great potential for application in wireless communication and radar systems.

Key words: microwave photonics, self-interference cancellation, elect-optical modulation, cancellation depth, I/Q demodulation