Photonic-Assisted RF Self-Interference Cancellation Based on Optical Spectrum Processing

Abstract

In band full-duplex (IBFD) wireless systems increase the RF spectrum efficiency and have become one of the key technologies in the future wireless communication systems. But it is only possible if the radio-frequency (RF) self-interference (SI) generated by the transmitter is sufficiently mitigated. SI cancellation becomes more difficult while the bandwidth and frequency increases. Herein, a novel approach to photonic-assisted RF SI cancellation based on optical processing is proposed for IBFD wireless systems. In this scheme, reference signal and the received signal are converted to optical signals by two Mach-Zehnder modulators. The phase and amplitude between reference and received signal are matched by optical spectrum processing, and the delay time is aligned by finely tuning the tunable optical delay line (TODL). The broadband interference signal within the received signal is removed in the optical domain. Experimental results show more than 30 dB cancellation depth in 10 GHz bandwidth. Besides, IBFD transmission performance based on 16-QAM for different symbol rates and different signal-to–interference ratios (SIR) are also demonstrated, as well as 92.6 dB•Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> spurious-free dynamic range (SFDR) is obtained.