RF Characterization of Self-Interference Cancellation Using Phase Modulation and Optical SideBand Filtering

Full-Duplex scheme transmitting and receiving signals simultaneously in the same frequency band can significantly improve the throughput and the spectrum efficiency, and is considered as a candidate technology for the fifth generation (5G) wireless communication. However, the high power transmitted signal will interfere with the in-band weak received signal, which is called as RF self-interference. It cannot be simply removed by a notch filter or a narrow bandpass filter because the same frequency band is used for both transmitter and receiver. An optical approach to implement RF self-interference cancellation is proposed. Based on the inherent out-of-phase property between the left and right sidebands of phase-modulated signal and optical sideband filtering, the RF self-interference cancellation is achieved by tuning the delay time and amplitude in the optical domain. The cancellation depth of the system was measured for different frequencies and bandwidths. The cancellation performance affected by the time delay deviation, the amplitude deviation and phase response is analyzed according to experimental results. It gives the direction for the improvement of system performance. Finally, the full-duplex communication by using the optical SIC approach was also investigated. Signal of interest is recovered and the constellation diagram was also shown.