MATLAB 4傅里葉變換及性質(zhì)

1、使用MATLAB命令求出下列信號(hào)的傅里葉變換，并繪出其幅度譜和相位譜。⑴clearall;delta=0.03;t=-10:delta:10;w=-10:delta:10;ft1=sin(2*pi*(t-1))./(pi*(t-1));Fw=delta*ft1*exp(-j*t'*w);abs=abs(Fw);ang=angle(Fw);subplot(211);plot(w,abs),axis([-10,10,-0.5,1.5]),title('f1(t)頻譜圖'),gridonsubplot(212);plot(w,ang),axis([-10,10,-4,4]),title('f1(t)相位圖'),gridonf1(t)相位圖■4Iiiii■giiiiiiiii'-10-8-6-4-2□246810（2）clearall;delta=0.03;t=-10:delta:10;w=-10:delta:10;ft2=sinc(pi*t).”2;Fw=delta*ft2*exp(-j*t'*w);abs=abs(Fw);ang=angle(Fw);subplot(211);plot(w,abs),axis([-10,10,-0.5,1]),title('f2(t)頻譜圖'),gridonsubplot(212);plot(w,ang),axis([-10,10,-0.000015,0.000015]),title(f2(t)相位圖'),gridon即）頻諧圖2、使用MATLAB命令求下列信號(hào)的傅里葉反變換，并繪出其時(shí)域信號(hào)圖。⑴clearalldelta=0.01;t=-10:delta:10;w=-10:delta:10;Fw1=(10./(3+j*w))+(4./(5+j*w));ft1=delta./(2*pi)*(Fw1*exp(-j*w'*t));plot(t,ft1);title('f1(t)時(shí)域信'),gridonf1[t）時(shí)域信號(hào)(2)clearalldelta=0.01;t=-10:delta:10;w=-10:delta:10;Fw2=(2*w)./(j*(16+w.*w));ft2=delta*(Fw2*exp(-j*w'*t))./(2*pi);plot(t,ft2);title('f2(t)時(shí)域信號(hào)'),gridon3、利用MATLAB數(shù)值法分別繪出下列所示信號(hào)的幅度譜(1)clearall;delta=0.003;t=-2:delta:2;w=-40:delta:40;ft1=stepfun(t,-1)-stepfun(t,1);Fw1=delta*ft1*exp(-j*t'*w);abs=abs(Fw1);subplot(311);plot(t,ft1);axis([-2,2,-0.5,1.5]);title('時(shí)域信號(hào)'),gridonsubplot(312);plot(w,Fw1),axis([-40,40,-0.5,2]);title('頻域'),gridonsubplot(313)plot(w,abs);axis([-40,40,0,2]);title('幅度譜'),gridon.時(shí)域信號(hào)1.5iiiiiii[::::[:LLn:::1:0；；；7；-051111111U-1.5-1-0.5G0.511.52幅度譜(2)clearall;delta=0.003;t=-2:delta:2;w=-20:delta:20;ft2=tripuls(t,2);Fw2=delta*ft2*exp(-j*t'*w);abs=abs(Fw2);subplot(311);plot(t,ft2);axis([-2,2,-0.5,1.5]);title('時(shí)域信號(hào)'),gridonsubplot(312);plot(w,Fw2),axis([-10,10,-0.5,1.5]);title('頻域'),gridonsubplot(313)plot(w,abs);axis([-10,10,0,1.5]);title('幅度譜'),gridon時(shí)域信號(hào)151::::―:::05:::上:-g[二':；二_口5111111111■-10-8-6-4-202468104、設(shè)矩形信號(hào)，()=u"+°.5)-u('—0?5),利用Matlab命令繪出該信號(hào)及其頻譜圖。同時(shí)繪出寸('/2*f(2t)的頻譜圖，并加以比較。clearalldetla=0.007;t=-10:detla:10;w=-20:detla:20;a=0.5;t1=a*tft1=heaviside((t1+0.5))-heaviside((t1-0.5));Fw1=detla*ft1*exp(-j*((t)')*w);abs1=abs(Fw1);ang1=angle(Fw1);b=2;t2=b*tft2=heaviside((t2+0.5))-heaviside((t2-0.5));Fw2=detla*ft2*exp(-j*((t)')*w);abs2=abs(Fw2);ang2=angle(Fw2);subplot(421);plot(t,ft1),title('f(t/2)時(shí)域圖'),gridonsubplot(423);plot(w,Fw1),title('f(t/2)頻域圖'),gridonsubplot(425);plot(w,abs1),title('f(t/2)頻譜圖'),gridonsubplot(427);plot(w,ang1),title('f(t/2)相位圖'),gridonsubplot(422);plot(t,ft2),title('f(2*t)時(shí)域圖'),gridonsubplot(424);plot(w,Fw2),title('f(2*t)頻域圖'),axis([-20,20,-5,5]),grido