Research On Key Technology Of High-Order QAM Modulation And Demodulation Systems

With the rapid development of communication technology,the traditional communication system cannot meet the demand of life,many new modulation and demodulation technologies are born on demand.Due to the limited spectrum resources,high-order quadrature amplitude modulation with high spectrum utilization has been widely used.However,as the modulation order increases,except for the additive white noise,phase noise will significantly affect the performance of QAM modulation and demodulation system as well.Phase noise is multiplicative noise with signal,which causes random rotation of constellation points,then system performance deteriorates.This thesis focuses on the phase noise suppression problem in 1024QAM modulation and demodulation system,and implements a circular symmetric 1024QAM modulation and demodulation system based on field programmable gate array.Firstly,this thesis introduces the source,representation and common models of phase noise.By simulating the Wiener phase noise with Matlab,this thesis analyzes the influence of phase noise on high-order QAM constellation.Secondly,the phase noise estimation and compensation algorithms for carrier recovery module are investigated,including non-data-assisted power law algorithm and data-assisted adaptive least mean square algorithm.This thesis focuses on improving the PL algorithm and proposing a PL optimization algorithm based on decision iteration.This algorithm estimates and compensates the decision-directed residual phase error on the data.The simulation results show that the algorithm delivers a gain of about 3d B at a system bit error ratio of10^-2.Finally,the high-order QAM constellation structure is studied centers on phase noise suppression,including the circular symmetric 1024QAM constellation structure and the spiral 1024QAM constellation structure.Based on the existing circular symmetric 1024QAM constellation structure.The simulation results show that the amplitude optimization scheme is optimized to improve constellation tolerance to phase noise.Based on the KCU1500 development board of Xilinx Kintex Ultra Scale series,this thesis design and realized a circular symmetrical 1024QAM modulation and demodulation system.Firstly,the overall implementation scheme of the circular symmetric 1024QAM modulation and demodulation system is designed,and then the implementation methods and interface descriptions are provided for each sub-module of the system.Secondly,the circular symmetric 1024QAM modulation and demodulation test system is built,and the simulation results of each sub-module as well as the whole system are analyzed.Finally,the system performance analysis of circular symmetric 1024QAM modulation and demodulation system is carried out.