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1、信号与系统实验10.1利用fourier函数求下列信号的傅里叶变换F(jw),并用ezplot函数绘出其幅度频谱
2、F(jw)
3、和相位频谱d(w)。<1>f1(t)=(sin(2*pi*t)/(2*pi*t))2symstphaseimref=sin(2*pi*t)/(2*pi*t);F=fourier(f);subplot(3,1,1)ezplot(f);title('Ôͼ')axis([-pipi-0.31.1])subplot(3,1,2)ezplot(abs(F))title('·ù¶È
4、ͼ')axis([-3*pi3*pi0.30.6])im=imag(F);re=real(F);phase=atan(im/re);subplot(3,1,3)ezplot(phase)title('Ïàλͼ')axis([-3*pi3*pi-0.50.5])<2>f2(t)=sin(2*pi*(t-2))/(2*pi*(t-2))symstphaseimref=sin(2*pi*(t-2))/(2*pi*(t-2));F=fourier(f);subplot(3,1,1)ezplot(f
5、);title('Ôͼ')axis([-pi2*pi-0.31.1])subplot(3,1,2)ezplot(abs(F))title('·ù¶ÈÆ×')axis([-3*pi3*pi0.30.6])im=imag(F);re=real(F);phase=atan(im/re);subplot(3,1,3)ezplot(phase)title('ÏàλÆ×')axis([-3*pi3*pi-0.50.5])10.2试用ifourier函数求下列傅里叶变换的逆变换,并画出其时域波形。<1>F
6、(iw)=1/2Sa2(w/4);symstwF=8*(sin(w/4))^2/(w^2);f=ifourier(F,t)ezplot(f);axis([-0.80.8-0.21.1]);title('ʱÓò²¨ÐÎ')输出为:f=-(4*fourier(cos(w/2)/w^2,w,-t)+4*pi*t*(2*heaviside(t)-1))/(2*pi)报错:Errorusinginlineeval(line15)Errorininlineexpression==>-(4.*fourier
7、(cos(w./2)./w.^2,w,-t)+4.*pi.*t.*(2.*heaviside(t)-1))./(2.*pi)Undefinedfunction'fourier'forinputargumentsoftype'double'.Errorininline/feval(line34)INLINE_OUT_=inlineeval(INLINE_INPUTS_,INLINE_OBJ_.inputExpr,INLINE_OBJ_.expr);Errorinezplotfeval(line54
8、)z=feval(f,x(1),y(1));Errorinezplot>ezimplicit(line258)u=ezplotfeval(f,X,Y);Errorinezplot(line154)hp=ezimplicit(cax,f{1},vars,labels,args{:});Errorinsym/ezplot(line61)h=ezplot(fhandle(f));ErrorinUntitled(line4)ezplot(f);调试过很多次了,仍然出不来图像。10.3已知信号f(t)的波
9、形如图所示,使用MATLAB傅里叶变换数值算法,解决一以下问题:<1>求f1(t)的傅里叶变换F1(jw),并绘制出其幅度频谱
10、F1(jw)
11、以及相位频谱曲线。<2>求f2(t)=f(t-2)的傅里叶变换F2(jw)
12、,并绘制出其幅度频谱
13、F2(jw)
14、以及相位频谱曲线。观察分析傅里叶变换的时移特性。(1)dt=0.005;t=-2:dt:2;f=(t/2+1/2).*((t>=-1)&(t<=1));N=2000;k=0:N;W=2*pi*k/(N*dt);F=f*exp(-1i*t'*W)*
15、dt;phase=angle(F);F=abs(F);subplot(3,1,1);plot(t,f);xlabel('t');ylabel('f(t)');title('f(t)');subplot(3,1,2);plot(W,F);xlabel('omega');ylabel('omega');title('f(t)µÄ¸µÀïÒ¶±ä»»F(omega)');subplot(3,1,3);plot(W,phase);axis([0,200,-5,5]);xlabel('omega'
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