The Performance Evaluation Of QPSK Under The Plasma Sheath Environment

When hypersonic vehicle re-entry atmosphere,a layer of plasma sheath will come into being on the surface of hypersonic vehicle because of high temperature,high pressure and friction atmosphere,the existence of plasma sheath will exert severe influence on communication of space aircraft.Quadrature phase shift keying(QPSK)is a widely method used in modulation scheme for low code rate data channel in the measurement and control operations.The communication performance of QPSK modulation in the plasma sheath,is essential to the whole process of reentry.This paper is to study the performance of QPSK in the plasma sheath.Based on the analysis of the plasma sheath of the principle and effect of signal,to study the plasma sheath channel characteristics and common communication channel modeling theory;established the plasma sheath channel model and QPSK modulation and demodulation algorithm is realized in the MATLAB platform,and on this basis,build in plasma sheath under the influence of QPSK simulation system.Through the observation of the modulation and demodulation waveform found system well realize the QPSK modulation.By observing the constellation can be seen the demodulation performance of the system.The final analysis of the signal to noise,multipath rician factor and transmission coefficient and key parameters of the system.The paper shows that the influence of plasma sheath channel,QPSK modulated signal will produce jitter,affects the performance of the system The simulation results show that it can improve system performance to improve the signal-to-noise ratio of the system and transmission coefficient.It provides a reference for the communication of the plasma sheath,which has certain theoretical significance and practical value.