FFT的matlab程序.doc

源程序%*% FFT實(shí)踐及頻譜分析 %*%*%*1.正弦波*%fs=100;%設(shè)定采樣頻率N=128;n=0:N-1;t=n/fs;f0=10;%設(shè)定正弦信號(hào)頻率%生成正弦信號(hào)x=sin(2*pi*f0*t);figure(1);subplot(231);plot(t,x);%作正弦信號(hào)的時(shí)域波形xlabel(t);ylabel(y);title(正弦信號(hào)y=2*pi*10t時(shí)域波形);grid;%進(jìn)行FFT變換并做頻譜圖y=fft(x,N);%進(jìn)行fft變換mag=abs(y);%求幅值f=(0:length(y)-1)*fs/length(y);%進(jìn)行對(duì)應(yīng)的頻率轉(zhuǎn)換figure(1);subplot(232);plot(f,mag);%做頻譜圖axis(0,100,0,80);xlabel(頻率(Hz);ylabel(幅值);title(正弦信號(hào)y=2*pi*10t幅頻譜圖N=128);grid;%求均方根譜sq=abs(y);figure(1);subplot(233);plot(f,sq);xlabel(頻率(Hz);ylabel(均方根譜);title(正弦信號(hào)y=2*pi*10t均方根譜);grid;%求功率譜power=sq.2;figure(1);subplot(234);plot(f,power);xlabel(頻率(Hz);ylabel(功率譜);title(正弦信號(hào)y=2*pi*10t功率譜);grid;%求對(duì)數(shù)譜ln=log(sq);figure(1);subplot(235);plot(f,ln);xlabel(頻率(Hz);ylabel(對(duì)數(shù)譜);title(正弦信號(hào)y=2*pi*10t對(duì)數(shù)譜);grid;%用IFFT恢復(fù)原始信號(hào)xifft=ifft(y);magx=real(xifft);ti=0:length(xifft)-1/fs;figure(1);subplot(236);plot(ti,magx);xlabel(t);ylabel(y);title(通過(guò)IFFT轉(zhuǎn)換的正弦信號(hào)波形);grid;%*2.矩形波*%fs=10;%設(shè)定采樣頻率t=-5:0.1:5;x=rectpuls(t,2);x=x(1:99);figure(2);subplot(231);plot(t(1:99),x);%作矩形波的時(shí)域波形xlabel(t);ylabel(y);title(矩形波時(shí)域波形);grid;%進(jìn)行FFT變換并做頻譜圖y=fft(x);%進(jìn)行fft變換mag=abs(y);%求幅值f=(0:length(y)-1)*fs/length(y);%進(jìn)行對(duì)應(yīng)的頻率轉(zhuǎn)換figure(2);subplot(232);plot(f,mag);%做頻譜圖xlabel(頻率(Hz);ylabel(幅值);title(矩形波幅頻譜圖);grid;%求均方根譜sq=abs(y);figure(2);subplot(233);plot(f,sq);xlabel(頻率(Hz);ylabel(均方根譜);title(矩形波均方根譜);grid;%求功率譜power=sq.2;figure(2);subplot(234);plot(f,power);xlabel(頻率(Hz);ylabel(功率譜);title(矩形波功率譜);grid;%求對(duì)數(shù)譜ln=log(sq);figure(2);subplot(235);plot(f,ln);xlabel(頻率(Hz);ylabel(對(duì)數(shù)譜);title(矩形波對(duì)數(shù)譜);grid;%用IFFT恢復(fù)原始信號(hào)xifft=ifft(y);magx=real(xifft);ti=0:length(xifft)-1/fs;figure(2);subplot(236);plot(ti,magx);xlabel(t);ylabel(y);title(通過(guò)IFFT轉(zhuǎn)換的矩形波波形);grid;%*3.白噪聲*%fs=10;%設(shè)定采樣頻率t=-5:0.1:5;x=zeros(1,100);x(50)=100000;figure(3);subplot(231);plot(t(1:100),x);%作白噪聲的時(shí)域波形xlabel(t);ylabel(y);title(白噪聲時(shí)域波形);grid;%進(jìn)行FFT變換并做頻譜圖y=fft(x);%進(jìn)行fft變換mag=abs(y);%求幅值f=(0:length(y)-1)*fs/length(y);%進(jìn)行對(duì)應(yīng)的頻率轉(zhuǎn)換figure(3);subplot(232);plot(f,mag);%做頻譜圖xlabel(頻率(Hz);ylabel(幅值);title(白噪聲幅頻譜圖);grid;%求均方根譜sq=abs(y);figure(3);subplot(233);plot(f,sq);xlabel(頻率(Hz);ylabel(均方根譜);title(白噪聲均方根譜);grid;%求功率譜power=sq.2;figure(3);subplot(234);plot(f,power);xlabel(頻率(Hz);ylabel(功率譜);title(白噪聲功率譜);grid;%求對(duì)數(shù)譜ln=log(sq);figure(3);subplot(235);plot(f,ln);xlabel(頻率(Hz);ylabel(對(duì)數(shù)譜);title(白噪聲對(duì)數(shù)譜);grid;%用IFFT恢復(fù)原始信號(hào)xifft=ifft(y);magx=