final2.m

给定一个音频范围内的模拟强噪声随机信号（强噪声+周期信号）

%巴特沃斯滤波器
clear all;
close all;
fp=1000;%通带截止频率
fs=2000;%阻带截止频率
Rp=2;
Rs=35;
Fs=10000;
Wp=2*fp/Fs;
Ws=2*fs/Fs;
[N,Wn]=buttord(Wp,Ws,Rp,Rs);
[b,a]=butter(N,Wn);
[H,w]=freqz(b,a,Fs);
h=abs(H);
plot(w/pi,h);
axis([0 1 0 1.1]);
xlabel('w/pi');
ylabel('|H(jw)|');
title('巴特沃斯滤波器');
grid on
 
%低频信号发生器采样信号
t=[0:100]/Fs;
x=wavrecord(200,Fs,2,'double');%音频调用函数
%[x Fs Nbits]=wavread('myvoice1');
figure(2);
plot(x(1:20)); 
title('原信号');
aver_x=mean(x)
power_x=mean(x.^2)
d_x=var(x)
xf=fft(x,Fs);
figure(3);
stem(abs(xf),'.')
title('原信号的频谱');
rxx=xcorr(x,'coef');
figure(4)
plot(rxx)
title('原信号的自相关')
rxxf=fft(rxx,Fs);
figure(5);
stem(abs(rxxf),'.');
title('原信号功率谱密度');
 
 
%噪声加入程序
xn=AWGN(x,10,0);  
figure(6);
plot(t,xn(1:length(t)));
title('加噪后信号');
 

%通过低通滤波器
y1=filter(b,a,xn);
figure(7);
plot(t,y1(1:length(t)));
title('滤波器输出信号');
figure(8);
for i=1:200
    y(i)=mean(y1(i:10:200));
end
plot(y(1:100))
title('提取信号')
aver_y=mean(y)
power_y=mean(y.^2)
d_y=var(y)
yf=fft(y,Fs);
figure(9);
stem(abs(yf),'.');
title('输出信号的频谱');
ryy=xcorr(y,'coef');
ryyf=fft(ryy,Fs);
figure(10);
stem(abs(ryyf),'.');
title('输出信号功率谱密度');
rxy=xcorr(x,y,'coef');
figure(11);
stem(rxy,'.');
title('互相关函数');