7-6.m

matlab数字信号与应用源代码7

%例程7－6  自适应噪声对消器
%自适应噪声对消器

clear all
clc               
t=0:1/1000:10-1/1000;
s=sin(2*pi*t);
snr=10;
s_power=var(s);              %var函数: 返回方差值
linear_snr=10^(snr/10);
factor=sqrt(s_power/linear_snr);
noise=randn(1,length(s))*factor;
x=s+noise;                   %由SNR计算随机噪声

x1=noise;                    %噪声源输入
x2=noise;
w1=0;                       %权系数初值
w2=0; 
e=zeros(1,length(x));
y=0;
u=0.05;                  
for i=1:10000                 %LMS算法
    y=w1*x1(i)+w2*x2(i);
    e(i)=x(i)-y; 
    w1=w1+u*e(i)*x1(i); 
    w2=w2+u*e(i)*x2(i);    
end

figure(1)
subplot(3,1,1)
plot(t,x);
title('带噪声正弦信号')
axis([0 10 -1.2 1.2]);
subplot(3,1,2)
plot(t,noise);
title('噪声信号')
axis([0 10 -1.2 1.2]);
subplot(3,1,3)
plot(t,e);
title('自适应噪声对消器')
axis([0 10 -1.2 1.2]);