实训三 数字信号基带传输的仿真设计.docx
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实训三 数字信号基带传输的仿真设计.docx
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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;closeall;
clearall;
N_sample=100;
N_num=1000;
t=0/N_sample:
1/N_sample:
N_num-1/N_sample;
st=0;
fori=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([015-1.51.5]);gridon;
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([-8802]);gridon;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%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([015-22]);gridon;
title('基带信号波形(滚降系数为1)');
st1=0;
fori=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([-5501.5]);gridon;
%%%%%%%%%%%%%%%%%%%%%%%
n=10^6;
snr_db=0:
12;
ber=zeros(1,length(snr_db));%生成0矩阵
fori=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*');holdon;gridon;
semilogy(snr_db,pe,'r-');xlabel('A/&');ylabel('ber');
legend('ber','ber_Theory');
2.
clc
clearall;
closeall;
figure;
ht=rcosflt(1,1,200,'fir/sqrt',1,3);
subplot(2,2,1)
plot(ht);axis([01200-0.030.10]);gridon;
ht=rcosflt(1,1,200,'fir/sqrt',0.75,3);
subplot(2,2,2)
plot(ht);axis([01200-0.030.10]);gridon;
ht=rcosflt(1,1,200,'fir/sqrt',0.5,3);
subplot(2,2,3)
plot(ht);axis([01200-0.030.10]);gridon;
ht=rcosflt(1,1,200,'fir/sqrt',0.25,3);
subplot(2,2,4)
plot(ht);axis([01200-0.030.10]);gridon;
3.
clearall;
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]);gridon;
4.
clearall;
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');
gridon;
%%%%%%%%%%%%
clearall;
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');
gridon;
%%%%%%%%%
clearall;
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');
gridon;
%%%%%%%%%
clearall;
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');
gridon;
%%%%%%%%%%%
clearall;
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');
gridon;
5.
clcclearall;
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([-1.51.5]);
holdon;
plot(y,'b');
gridon;
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