发布时间 : 星期一 文章2PSK数字信号的调制与解调更新完毕开始阅读
参考文献
[1] 董邵平,陈世庚，王洋.数字信号处理基础[TN].哈尔滨:哈尔滨工业大学出版社，2003 [2] John G.Proakis,MasoudSalehi.Communication Systems
Engineering./www.phei.com.cn/,
2002
[3] 樊昌信,曹丽娜. 通信原理（第六版）[TN]. 北京：国防工业出版社, 2006 [4] 韩利华，王华.MATLAB电子仿真与应用[TN].北京：国防工业出版社, 2003
致谢
这次软件课程设计过程中，非常感谢我们的^^^^老师，从一开始的大框架的搭建，以及相关选题的决定过程中的指导。同样也感谢我的室友以及同学，他们在我的这次设计过程中给了我很大的帮助。
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附录(见电子文档)
clc;
clear all; close all;
fs=8e5;%抽样频率 fm=20e3;%基带频率 n=2*(6*fs/fm);
final=(1/fs)*(n-1); fc=2e5; % 载波频率 t=0:1/fs:(final); Fn=fs/2;%耐奎斯特频率
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 用正弦波产生方波
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% twopi_fc_t=2*pi*fm*t; A=1; phi=0;
x = A * cos(twopi_fc_t + phi); % 方波 am=1;
x(x>0)=am; x(x<0)=-1;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 信源信号
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% figure(1) subplot(321); plot(t,x);
axis([0 2e-4 -2 2]); title('信源信号'); grid on
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % PSK调制信号
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% car=sin(2*pi*fc*t);%载波 ask=x.*car;%载波调制 subplot(322); plot(t,ask);
axis([0 200e-6 -2 2]); title('PSK信号'); grid on;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 噪音信号
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% vn=0.1;
noise=vn*(randn(size(t)));%产生噪音 subplot(323); plot(t,noise); grid on;
title('噪音信号'); axis([0 .2e-3 -1 1]);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 调制后加噪
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% askn=(ask+noise);%调制后加噪 subplot(324); plot(t,askn);
axis([0 200e-6 -2 2]); title('加噪后调制信号'); grid on;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 带通滤波器
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% fBW=40e3;
f=[0:3e3:4e5]; w=2*pi*f/fs; z=exp(w*j); BW=2*pi*fBW/fs;
a=.8547;%BW=2(1-a)/sqrt(a) p=(j^2*a^2); gain=.135;
Hz=gain*(z+1).*(z-1)./(z.^2-(p)); subplot(325); hh=abs(Hz); plot(f,hh);
title('带通滤波器'); grid on;
Hz(Hz==0)=10^(8);%avoid log(0) subplot(326); hhb=20*log10(hh); plot(f,hhb); grid on;
title('Receiver -3dB Filter Response'); axis([1e5 3e5 -3 1]);
set (gcf, 'num', 'off', 'name', ['系统信号调制波形'... blanks(10)]);
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 带通滤波后输出
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% a=[1 0 0.7305];%[1 0 p]
b=[0.135 0 -0.135];%gain*[1 0 -1] faskn=filter(b,a,askn); figure(2) subplot(321); plot(t,faskn);
axis([0 100e-6 -2 2]);
title('通过带通滤波后输出'); grid on;
cm=faskn.*car;%解调 subplot(322); plot(t,cm);
axis([0 100e-6 -2 2]); grid on;
title('通过相乘器后输出');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 低通滤波器
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% p=0.72;
gain1=0.14;%gain=(1-p)/2 Hz1=gain1*(z+1)./(z-(p));
subplot(323);
Hz1(Hz1==0)=10^(-8);%avoid log(0) plot(f,20*log10(abs(Hz1))); grid on;
title('LPF -3dB response'); axis([0 5e4 -3 1]);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 滤波器系数
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% a1=[1 -0.72];%(z-(p))
b1=[0.14 0.14];%gain*[1 1] so=filter(b1,a1,cm); so=so*10;-d gain
so=so-mean(so);%removes DC component subplot(324); plot(t,so);
axis([0 8e-4 -3.5 3.5]);
title('通过低通滤波器后输出'); grid on;
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