Research On Compensation Technology Of IQ Imbalance And Phase Noise In Terahertz Communication

With the development of wireless communication to the 5th Generation Mobile Networks(5G),traditional spectrum resources have been gradually exhausted.In order to meet the rapidly growing demand for wireless communication transmission rate in the future,people are turning to higher frequency bands.Terahertz(THz)communication has attracted the high attention of academia and industry due to its rich spectrum resources and the data transmission rate that can achieve gigabit or even terabit level.However,with the increase of carrier frequency of THz communication system,the design and manufacture of Radio Frequency(RF)front-end become more and more difficult owing to the limitation of cost,complexity,and current technology level.The RF nonlinear distortion introduced by it will seriously damage the performance of the THz communication system.In this context,this thesis focuses on the frequency-independent IQ Imbalance(IQI)and Phase Noise(PN)digital baseband compensation algorithms in the THz communication system based on single carrier frequency domain equalization(SC-FDE).The main content of the thesis is divided into three parts:The first part starts from the model,and the IQ imbalance model,60 GHz phase noise model,and terahertz phase noise model are firstly introduced.Besides,the time-domain phase noise simulation models corresponding to two kinds of phase noise are studied.The analysis shows that THz phase noise has Gaussian color noise characteristics,and there is a correlation between the phase noise points.The second part centers on the terahertz frequency independent IQ imbalance,and the system model under the influence of IQI is firstly deduced,which indicates that the signal is affected by the mirror interference from itself because of IQI.Subsequently,it is analyzed that the traditional method based on the minimization of the Channel Variation Energy(CVE)can increase the divergence of the signal constellation when compensating for the signal affected by IQ imbalance.On the basis of this,an improved compensation algorithm for IQ imbalance based on K-means is proposed,which uses cluster analysis to reduce the distortion of constellation point divergence.Finally,the simulation results indicate that the proposed algorithm can significantly improve the system performance.The third part derives the system model under the influence of PN in light of terahertz phase noise,and it is concluded that PN can degrade the system performance by introducing common phase error(CPE)and Inter-Symbol Interference(ISI).After that,a phase noise compensation algorithm with Discrete Cosine Transform(DCT)orthogonal basis reconstruction is proposed based on the idea of phase noise reconstruction estimation under orthogonal transformation.Although the complexity of the algorithm is slightly higher,the algorithm achieves a better phase noise suppression effect and has the advantage of fast convergence.Finally,aiming at the problem of error propagation in the iterative phase noise compensation algorithm,which limits the compensation effect in the high-intensity phase noise scene,an iterative adaptive phase noise compensation algorithm based on decision feedback is proposed.This algorithm has the same time complexity as the traditional iterative Least Mean Square(LMS)algorithm but has a better phase-noise compensation effect.Especially in the case of high-intensity phase noise,the performance of the proposed algorithm is improved more obviously.