连续信号的傅里叶变换及matlab显示

(1)f(t)=u(t+6)-u(t-6)(2)f1(t)=f(-2t)(3)f2(t)=f(t-2)(4)f3(t)=f(t)·e以上四个式子的Matlab编程求其傅里叶变换与幅频特性，相频特性图dt=0.001t=-15:dt:15;f=(t=-6)-(t=6);k=-600:600;w1=2*pi*k/600;F=f*exp(-j*t'*w1)*dt;subplot(4,3,1);plot(t,f);axis([-15,15,-0.1,1.1]);grid;subplot(4,3,2);plot(w1,abs(F));axis([-7,7,-1,13]);grid;subplot(4,3,3);plot(w1,angle(F));axis([-10,10,-5,5]);grid;dt=0.001t=-15:dt:15;f=(t=6)-(t=-3);k=-600:600;w1=2*pi*k/600;F=f*exp(-j*t'*w1)*dt;subplot(4,3,4);plot(t,f);axis([-15,15,-0.1,1.1]);grid;subplot(4,3,5);plot(w1,abs(F));axis([-7,7,-1,10]);grid;-j6tsubplot(4,3,6);plot(w1,angle(F));axis([-10,10,-5,5]);grid;dt=0.001t=-15:dt:15;f=(t=-4)-(t=8);k=-600:600;w1=2*pi*k/600;F=f*exp(-j*t'*w1)*dt;subplot(4,3,7);plot(t,f);axis([-15,15,-0.1,1.1]);grid;subplot(4,3,8);plot(w1,abs(F));axis([-7,7,-1,13]);grid;subplot(4,3,9);plot(w1,angle(F));axis([-8,8,-5,5]);grid;dt=0.001;t=-15:dt:15;f=((t=-6)-(t=6)).*exp(-j*5*t);k=-600:600;w1=2*pi*k/600;F=f*exp(-j*t'*w1)*dt;subplot(4,3,10);plot(t,f);axis([-10,10,-1.2,1.2]);grid;subplot(4,3,11);plot(w1,abs(F));axis([-7,7,-1,13]);grid;subplot(4,3,12);plot(w1,angle(F));axis([-8,8,-5,5]);grid;