matlab仿真.doc

%題目1clear;clear all;fs=1000;%抽樣頻率N=256;n=0:N-1;t=n/fs;x=sin(2*pi*10*t)+0.2*sin(2*pi*20*t);figure(1);subplot(211);plot(t,x);xlabel(t);ylabel(y);title(信號(hào)時(shí)域波形，N=256);grid;y=fft(x,N);%進(jìn)行fft變換m=abs(y);%求幅值f=(0:length(y)-1)*fs/length(y);%頻率轉(zhuǎn)換figure(1);subplot(212);plot(f,m);axis(0,1000,0,500);xlabel(頻率(Hz);ylabel(幅值);title(信號(hào)頻譜圖，N=256);grid;% N=512；clear;clear all;fs=1000;%抽樣頻率N=512;n=0:N-1;t=n/fs;x=sin(2*pi*10*t)+0.2*sin(2*pi*20*t);figure(1);subplot(211);plot(t,x);%作正弦信號(hào)的時(shí)域波形xlabel(t);ylabel(y);title(信號(hào)時(shí)域波形，N=512);grid;%進(jìn)行FFT變換并做頻譜圖y=fft(x,N);%進(jìn)行fft變換m=abs(y);%求幅值f=(0:length(y)-1)*fs/length(y);%頻率轉(zhuǎn)換figure(1);subplot(212);plot(f,m);%頻譜圖axis(0,1000,0,500);xlabel(頻率(Hz);ylabel(幅值);title(信號(hào)頻譜圖，N=512);grid;% N=1024;clear;clear all;fs=1000;%抽樣頻率N=1024;n=0:N-1;t=n/fs;x=sin(2*pi*10*t)+0.2*sin(2*pi*20*t);figure(1);subplot(211);plot(t,x);%作正弦信號(hào)的時(shí)域波形xlabel(t);ylabel(y);title(信號(hào)時(shí)域波形，N=1024);grid;%進(jìn)行FFT變換并做頻譜圖y=fft(x,N);%進(jìn)行fft變換m=abs(y);%求幅值f=(0:length(y)-1)*fs/length(y);%頻率轉(zhuǎn)換figure(1);subplot(212);plot(f,m);%做頻譜圖axis(0,1000,0,500);xlabel(頻率(Hz);ylabel(幅值);title(信號(hào)頻譜圖，N=1024);grid;%題目2：clear;clear all;a=7 10 0 7 1;b=1 2 0 -1;subplot(411);stem(a,fill);title( x(n);grid on;subplot(412);stem(b,fill);title( y(n);grid on;c=conv(a,b)M=length(c)-1;n=0:1:M;subplot(413);stem(n,c,fill);title(線性卷積 x(n)*h(n) );grid on;a2=a zeros(1,4);b2=b zeros(1,5);ak=fft(a2);bk=fft(b2);ck=ak.*bk;c2=i