PI4-QPSK信号的调制与解调

大学生本科毕业设计（论文）题目：PI/4-QPSK信号的调制与解调专业电子与通信工程类别计算机模拟日期05年5月I摘要在以前的数字蜂窝系统中，往往采用FSK、ASK、PSK等调制方式。随着数字蜂窝系统的发展，对调制和数字蜂窝系统的技术要求越来越高,许多优秀的调制技术应运而生，其中PI/4-QPSK技术是无线通信中比较突出的一种二进制调制方法。本文首先介绍了数字相位调制的一般原理；然后对PI/4-QPSK的调制原理进行了阐述，并对影响调制性能的滤波器进行了分析与研究；最后重点研究了PI/4-QPSK的三种解调方法并通过用Matlab对这一过程进行编程，得出信号在不同信噪比下模拟传输的时域图、频域图及功率谱密度曲线等，并在相同信道条件下通过眼图和误码率曲线图对PI/4-QPSK的三种解调方法进行了性能比较，得出了基带差分解调性能最差、中频差分解调性能次之、鉴频器解调性能最优的结论。关键词PI/4-QPSK；同相信道；正交信道；调制；差分解调IIAbstractPreviousdigitalhoneycombsystemoftenadoptmodulationwayofFSK,ASK,PSKetc.Alongwithdevelopmentofdigitalhoneycombsystemthetec-hnicalcriterionofmodulationanddemodulationwillbeadjustedtomeethig-herrequirement.Alotofexcellentmodulationtechnologyhasemergedasthetimesrequire,thePI/4-QPSKisoneofthemostoutstandingtechnologyinradiocommunication.Thispaperintroducesthemodemtheoryandprocessofthedigitalphasemodulationfirst.ThenstudiedthedetectionmethodofPI/4-QPSKandanalyzedthefilterwhichcaninfluencethesystem’sperformance.Finally,theprocessofthreedemodulatemethodsofthePI/4-QPSKwasemulated.ItalsoaddressesamethodforprogrammingwithMatlabtoanalyzethePI/4-QPSKsystemanddescrybeeshowtoemulatethesystemseparatelyviaidealsignalchannelandinterferedchannelswithdifferentsignaltonoiseratio.ThearticleanalysesthedynamicandstaticbehaviorsofthePI/4-QPSKsystemaswellastheperformanceagainstnoiseundertheconditionofGaussnoisechanne1.ThecomparisonismadeontheeyepatternandcurveofbiterrorratebetweenPI/4-DQPSK’sthreedemodulatemethodsunderthesamechannel.TheresultofsimulationshowsthattheperformanceofthebasebanddifferentialdetectorislessthantheIF-banddifferentialdetector’s,theperformanceoftheFM-discriminatordetectoristhebest.KeywordsPI/4-QPSK,In-phasechannel,Quadraturechannel,Modulation,Differentialdemodulationi目录摘要.............................................................................................................IAbstract......................................................................................................II第1章绪论..............................................................................................11.1课题背景..........................................................................................11.2PI/4-QPSK研究现状......................................................................11.3PI/4-QPSK信号的产生和定义......................................................21.4PI/4-QPSK的优点..........................................................................31.5本文主要研究内容和具体工作......................................................3第2章数字相位调制概述及性能比较..................................................52.1数字相位调制概述..........................................................................52.1.1四相QPSK的一般原理............................................................52.1.2偏移QPSK的一般原理............................................................62.1.3PI/4-QPSK的一般原理..............................................................82.2PI/4-QPSK与QPSK、OQPSK的性能比较.................................82.3PI/4-QPSK与GMSK的性能比较.................................................92.4本章小结........................................................................................10第3章PI/4-QPSK的调制....................................................................113.1PI/4-QPSK调制原理.....................................................................113.1.1PI/4-QPSK信号的产生.............................................................113.1.2PI/4-QPSK的调制原理.............................................................113.2PI/4-QPSK调制过程中滤波器的选取与研究............................153.2.1PI/4-QPSK调制方式下噪声与干扰的分析............................153.2.2滤波器的设计与选择..............................................................163.3本章小结........................................................................................17第四章PI/4-QPSK的解调...................................................................18ii4.1PI/4-QPSK解调原理....................................................................184.1.1基带差分解调..........................................................................184.1.2中频差分解调..........................................................................204.1.3鉴频器解调..............................................................................214.2非相干解调与相干解调性能比较................................................214.3信道非线性对线性调制的影响....................................................234.4PI/4-QPSK的误码性能分析........................................................244.5本章小结........................................................................................25第五章试验仿真结果与分析................................................................265.1PI/4-QPSK的调制仿真结果与分析............................................265.2PI/4-QPSK的解调仿真结果与分析............................................295.2.1基带差分解调..........................................................................305.2.2中频差分解调..........................................................................315.2.3鉴频器解调..............................................................................335.3不同解调方式下性能分析.....................................................