Research On Key Technology Of Receiver In Terahertz Ultra-High Speed Communication

It has been the era of the Internet of everything with the commercialization of 5th Generation Mobile Systems(5G),the gradual emergence of cloud services,3D holographic video,8K live streaming and other high-speed services.However,with the increase sharply of the number of network users,the transmission rate of 5G gradually fails to meet the communication needs of new services.Terahertz(THz)frequency band has rich spectrum resources and can support the throughput of Gbps or even Tbps,so it has become the focus of research in various countries.However,with the increase of frequency band,the RF non-ideality introduced into the RF front end of the system will seriously damage the communication quality.Considering the difficulty and cost of designing high frequency RF devices,it is difficult to directly optimize RF devices to reduce the non-ideal characteristics.A more feasible method is to design a compensation algorithm in receiver.Therefore,this thesis focuses on the receiver compensation algorithm of IQ Quadrature Imbalance(IQI)and Phase Noise(PN)In RF non-ideality.In this thesis,the Orthogonal Frequency Division Multiplexing(OFDM)system used in simulation links is introduced firstly,and the Orthogonal Frequency Division multiplexing(OFDM)system is proposed in terahertz wireless channel model.Then,a frequency-independent IQI baseband simulation model is introduced to analyze the source of phase noise in electron-based terahertz system from 60 GHz millimeter wave and build a time-domain simulation model of terahertz phase noise.The analysis shows that terahertz phase noise has Gaussian color noise characteristics.Aiming at IQ imbalance in RF non-ideal,this thesis analyzes the influence of IQI on OFDM system,and theoretically deduces that IQI will cause OFDM symbols to produce mirror interference.To resist the influence of IQI on symbols,a blind compensation algorithm of IQI based on minimum kurtosis is studied in this thesis,and an improved scheme of low complexity is proposed to solve the problem of high gradient computing complexity in this algorithm.Compared with the traditional algorithm,the computational complexity of the proposed algorithm is on the same order of magnitude.Compared with the traditional IQI parameter estimation algorithm based on minimizing channel change energy,the simulation results show that the proposed algorithm has better BER performance.The baseband equivalent model of phase noise in radio-frequency nonideality is presented.It is concluded that Phase noise will cause Common Phase Error(CPE)and Inter-Carrier Interference(ICI)when OFDM symbols are received.The effects of phase noise of different intensity on the performance of OFDM systems are simulated and analyzed.In this thesis,an iterative phase noise estimation algorithm based on orthogonal basis reconstruction and Kalman filter is studied,and an improved scheme is proposed to solve the problem that different system noises affect the convergence rate of Kalman filter and thus the estimation accuracy.Compared with the traditional algorithm,the computational complexity of the proposed algorithm is on the same order of magnitude.Compared with the traditional CPE compensation algorithm,the simulation results show that the proposed algorithm has better BER performance,and the improved scheme has better effect under high signal-to-noise ratio.