实训三 数字信号基带传输的仿真设计

实训三数字信号基带传输的仿真设计
一、实验内容
1、基带信号采用不归零矩形脉冲或升余弦滚降波形，基带信号的功率谱密度分析。

2、误码率的计算：Ａ／σ和误码率之间的性能曲线
3、眼图的生成
4、匹配滤波器
二、程序与仿真图
1.
%二进制不归零矩形脉冲
clc;close all;
clear all;
N_sample=100;
N_num=1000;
t=0/N_sample:1/N_sample:N_num-1/N_sample;
st=0;
for i=1:20
d=(randint(1,N_num)*2-1);
st_bb=rectpulse(d,N_sample); %将矩阵连接
window=boxcar(length(st_bb)); %矩形加窗函数
[pxx,f]=periodogram(st_bb,window,2^16,N_sample);
%计算功率谱密度函数，st_bb为待求函数，window是所使用的窗口，长度必须和待求函数一致
% 2*16是采样点数N_sample，采样频率
st=st+pxx;
end
st=st/20;
figure(1);
subplot(2,1,1);
plot(t,st_bb); title('基带信号波形');
axis([0 15 -1.5 1.5]);grid on;
subplot(2,1,2);
plot([-1*flipud(f);f],0.5*[flipud(st);st]); title('基带信号功率谱'); %dlipud实现矩阵上下翻转axis([-8 8 0 2]);grid on; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%二进制滚降系数为1
st_rc=rcosflt(d,1,80,'fir',1,1);
figure(2);
subplot(2,1,1);
plot(0:1/50:35-1/50,st_rc(1:35*50));axis([0 15 -2 2]);grid on;
title('基带信号波形(滚降系数为1)');
st1=0;
for i=1:5
d=(randint(1,N_num)*2-1);
st_re=rcosflt(d,1,40,'fir',1,1);
window=boxcar(length(st_rc));
[px1,f]=periodogram(st_rc,window,2^16,N_sample);
st1=st1+px1;
end
st1=st1/5;
subplot(212);
plot([-1*flipud(f);f],0.5*[flipud(st);st]);
title('基带信号功率谱(滚降系数为1)');
axis([-5 5 0 1.5]);grid on; %%%%%%%%%%%%%%%%%%%%%%%
n=10^6;
snr_db=0:12;
ber=zeros(1,length(snr_db)); %生成0矩阵
for i=1:length(snr_db)
d=(randint(1,n)*2-1);
dwn=awgn(d,snr_db(i)); %加性高斯白噪声
d_r=sign(dwn); %置位-1或1
ber(i)=length(find(d~=d_r))/n;%%%%
end
pe=0.5*erfc(sqrt(10.^(snr_db/10)/2));
figure(3);
semilogy(snr_db,ber,'k*');hold on;grid on;
semilogy(snr_db,pe,'r-');xlabel('A/&');ylabel('ber'); legend('ber','ber_Theory');
2.
clc
clear all;
close all;
figure;
ht=rcosflt(1,1,200,'fir/sqrt',1,3);
subplot(2,2,1)
plot(ht);axis([0 1200 -0.03 0.10 ] );grid on; ht=rcosflt(1,1,200,'fir/sqrt',0.75,3); subplot(2,2,2)
plot(ht);axis([0 1200 -0.03 0.10 ] );grid on; ht=rcosflt(1,1,200,'fir/sqrt',0.5,3); subplot(2,2,3)
plot(ht);axis([0 1200 -0.03 0.10 ] );grid on; ht=rcosflt(1,1,200,'fir/sqrt',0.25,3); subplot(2,2,4)
plot(ht);axis([0 1200 -0.03 0.10 ] );grid on;
3.
clear all;
N=1000;
x=sign(randn(1,N)); Ts = 1;
alpha = 1;y = rcosflt(x,1/Ts,100,'fir',alpha,5); figure(3);
plot(y);
title('多个滚降信号时域波形'); axis([0,3000,-1.5,1.5]);grid on;
4.
clear all;
N=1000;
x=sign(randn(1,N));
Ts = 1;
alpha = 1;
y = rcosflt(x,1/Ts,100,'fir',alpha,2); eyediagram(y,300,4);
title('无噪声时眼图');
grid on; %%%%%%%%%%%%
clear all;
N=1000;
x=sign(randn(1,N));
Ts = 1;
snr = 30;
alpha = 1;
y = rcosflt(x,1/Ts,100,'fir',alpha,2); y1 = awgn(y,snr);
eyediagram(y1,300);
title('SNR=30dB时的眼图');
grid on;
%%%%%%%%%
clear all;
N=1000;
x=sign(randn(1,N));
Ts = 1;
snr = 20;
alpha = 1;
y = rcosflt(x,1/Ts,100,'fir',alpha,2);y1 = awgn(y,snr);
eyediagram(y1,300);
title('SNR=20dB时的眼图');
grid on;
%%%%%%%%%
clear all;
N=1000;
x=sign(randn(1,N));
Ts = 1;
snr = 10;
alpha = 1;
y = rcosflt(x,1/Ts,100,'fir',alpha,2); y1 = awgn(y,snr);
eyediagram(y1,300,4);
title('SNR=10dB时的眼图');
grid on; %%%%%%%%%%%
clear all;
N=1000;
x=sign(randn(1,N));
Ts = 1;
snr = 0;
alpha = 1;
y = rcosflt(x,1/Ts,100,'fir',alpha,2); y1 = awgn(y,snr);
eyediagram(y1,300,4);
title('SNR=0dB时的眼图');
grid on;
5.
clc clear all;
N=64;
h=ones(1,N);
d=sign(randn(1,20)); y=rectpulse(d,N);
ht=conv(h,y);ht=ht./max(ht);
figure;
plot(ht,'r'); ylim([-1.5 1.5]); hold on;
plot(y,'b');
grid on;。