Research On The Key Technologies Of Radio Frequency Self-interference Cancellation System Based On Microwave Photonics

With the arrival of 5G,there exists a conflict between the explosive data traffic,resulting from new applications and devices,and the limited spectrum resource.To get out of this predicament,Co-time Co-frequency Full-Duplex(CCFD)is a key technology.However,CCFD suffers from serious self-interference between transmitting and receiving antennas which restrict its development and implementation.Generally,the self-interference is canceled simultaneously in three stages:passive self-interference cancellation(SIC),analog SIC,digital SIC.In this thesis,attention is focused on analog SIC.Among various methods to realize analog SIC,microwave photonics is an effective solution due to its inherent superiority.This thesis conducts systematic research as follows concerning microwave photonic radio frequency(RF)SIC technology:(1)The key performance in a microwave photonic SIC system is studied,including nonlinearity and cancellation ratio.The principle of two common ways of modulation,direct modulation and MZ-type modulation is analyzed.Base on the knowledge about modulation,the performance of the dual-modulator system and single-modulator system is compared.(2)A typical SIC system based on a dual-parallel Mach-Zehnder modulator(DP-MZM)is studied.Considering the defects in the conventional scheme,a novel scheme is proposed where the bias points of the DP-MZM is optimized to increase the power of the signal of interest(SOI)and the stability.In the proof-of-concept experiment,above 35d B of cancellation over 200MHz within the frequency range of 2.5?6GHz is demonstrated.Besides,over 96d B·Hz^2/3SFDR is achieved in both two arms where the received signal and the reference signal are input respectively.Meanwhile,an auto-control scheme for the DP-MZM-based SIC system is proposed and a corresponding auto-control module is designed and fabricated.(3)Based on a DP-MZM,a multifunctional RF front end that integrates SIC,optoelectronic oscillator(OEO),and down-conversion is proposed and implemented.As a proof-of-concept,the SOI is down-converted to 2.6GHz with the help of the generated local oscillator(LO)signal with a central frequency of 10 GHz and phase noise of-108.66d Bc/Hz@10k Hz.At the same time,the system achieves above 27d B of cancellation across150MHz/300MHz bandwidth.