Key Technologies And Verification Of Nonlinear Adjacent Self-Interference Suppression In Millimeter Wave Frequency Division Duplex Systems

At present,massive communication services put forward higher requirements for the performance of wireless communication system.Frequency division duplex is still a typical communication mode of base station,which has the characteristics of wide coverage and large system capacity,but it needs to set the protection frequency band to separate the receiving and sending channels.In order to improve the frequency spectrum utilization rate,it is required that no protection frequency band is set between the transmitter and receiver of the frequency division duplex system.In this case,the nonlinear distortion of RF devices such as power amplifier leads to adjacent frequency interference between the uplink and downlink signals of the frequency division duplex system.Aiming at nonlinear adjacent interference existing in upstream and downstream signals,this thesis studies a nonlinear adjacent self-interference suppression algorithm in millimeter wave frequency division duplex system,including:Firstly,the existing nonlinear neighbor-frequency self-interference suppression algorithms are investigated.This thesis describes the main sources of nonlinear adjacent frequency interference signals,summarizes the common nonlinear interference signal models,and investigates the main methods and research status of nonlinear adjacent frequency self-interference suppression,which provides theoretical reference for the research of nonlinear adjacent frequency self-interference suppression algorithms in frequency division duplex systems.Secondly,a Volterra series based nonlinear neighbor-frequency self-interference suppression algorithm is proposed.The overall structure of the millimeter wave frequency division duplex system is designed.In millimeter wave frequency division duplex system,an algorithm for estimating the response of power amplifier and wireless channel and nonlinear self-interference suppression is studied.An improved self-interference channel estimation method based on LS algorithm is designed,which can theoretically reduce the residual signal power by 3dB after nonlinear self-interference suppression.Two methods of nonlinear model simplification based on channel estimation and power amplifier memory characteristics are proposed,and the feasibility of the two methods is verified by simulation.Thirdly,the implementation and performance test of the nonlinear adjacent selfinterference suppression algorithm are completed.The architecture of millimeter wave frequency division duplex nonlinear adjacent self-interference suppression system is established,the key structure of nonlinear adjacent self-interference suppression algorithm is designed and implemented by FPGA,and the hardware test platform of millimeter wave frequency division duplex communication is built to test the performance of nonlinear adjacent self-interference suppression.The test results show that when the transmitting power of self-interference is 30 dBm and the interference-tonoise ratio in the received signal band is lower than 7dB,the residual interference is less than 2dB after nonlinear self-interference suppression.In this thesis,the nonlinear self-interference suppression of millimeter wave frequency-division duplex system is studied,which provides theoretical basis and engineering reference for the research and application of millimeter wave frequencydivision duplex communication system without protection interval.