数字信号处理：用matlab编程实现AM调制音乐信号的同步解调.doc

clear all; close all;clcx,fs,bit=wavread(F:费玉清-一剪梅 00_01_23-00_01_28.wav);x=x(:,1);% sound(x,fs);N=length(x);figuresubplot(2,1,1);plot(x)F1=fft(x,N);grid ontitle(原始音乐信号时域波型)xlabel(Time)ylabel(Magnitude)w1=2/N*0:N-1;subplot(2,1,2);plot(w1,abs(F1)grid ontitle(原始音乐信号频域波型)xlabel(Frequency/Hz)ylabel(Magnitude)n=0:N-1;x1=cos(n*0.95);figuresubplot(2,2,1);plot(x1)title(余弦信号时域波型)xlabel(Time)ylabel(Magnitude)F2=fft(x1,N);subplot(2,2,2);plot(w1,abs(F2)grid ontitle(余弦信号频域波型)xlabel(Frequency/Hz)ylabel(Magnitude)X=x.*x1;subplot(2,2,3);plot(X)F3=fft(X,N);grid ontitle(高频调制后音乐信号时域波型)xlabel(Time)ylabel(Magnitude)subplot(2,2,4);plot(w1,abs(F3)grid ontitle(高频调制后音乐信号频域波型)xlabel(Frequency/Hz)ylabel(Magnitude)X1=X.*x1;F4=fft(X1,N);figuresubplot(2,1,1);plot(X1);grid ontitle(解制后音乐信号时域波型)xlabel(Time)ylabel(Magnitude)subplot(2,1,2);plot(w1,abs(F4);grid ontitle(解制后音乐信号频域波型)xlabel(Frequency/Hz)ylabel(Magnitude)Rp=1;Rs=15;N1,Wc=buttord(0.2,0.3,Rp,Rs);B,A=butter(N1,Wc);H,W=freqz(B,A);figuresubplot(1,1,1);plot(W/pi,abs(H);grid ontitle(数字巴特沃斯滤波器)xlabel(Digital Frequency/pi)ylabel(Magnitude)y=filter(B,A,X1);% sound(y,fs);figuresubplot(2,1,1)plot(y);grid ontitle(巴特沃斯滤波后音乐信号时域波型)xlabel(Time)ylabel(Magnitude)y=fft(y,N);subplot(2,1,2)plot(w1,abs(y);grid ontitle(滤波后音乐信号频域波型)xlabel(Frequency/Hz)ylabel(Magnitude)N2=33;wc=0.3*pi;hd=ideal(N2,wc);w2=boxcar(N2);w3=blackman(N2);h1=hd.*w2;h2=hd.*w3;M=512;fh1=fft(h1,M);w2=2/M*0:M-1;fh2=fft(h2,M);figureplot(w2,abs(fh1)grid ontitle(矩形窗滤波器)xlabel(Frequency)ylabel(Magtitude)y1=conv(X1,h1);sound(y1,fs)figuresubplot(2,1,1);plot(y1);grid ontitle(矩形窗滤波后的音乐信号时域波形)xlabel(Time)ylabel(Magtitude)y1=fft(y1,M);subplot(2,1,2);plot(w2,abs(y1);grid ontitle(矩形窗滤波后的音乐信号频域波形)xlabel(Frequency)ylabel(Magtitude)figureplot(w2,abs(fh2)grid ontitle(布莱克曼窗滤波器)xlabel(Frequency)ylabel(Magtitude)y2=conv(X1,h2);% sound(y2,fs)figuresubplot(2,1,1);plot(y2);grid ontitle(布莱克曼窗滤波后的音乐信号时域波形)xlabel(Time)ylabel(Magtitude)y2=fft(y