dm10301.m

the code of the book come form the book of marlix laboratory with the book of singal

% dm10301
% 连续时间信号傅里叶变换的数值表示
dt = 0.005;                                        %采样间隔
t = 0:dt:2;
f = exp(-2*t);                                     %单边指数信号的离散采样点
N = 2000;                                          %设定频率采样点数
k = 0:N;
W = 2*pi*k/(N*dt);                                 %求角频率正半轴的采样点
F = f*exp(-j*t'*W)*dt;                             %求F(jw) 
F = real(F);                                       %求幅度频谱
W = [-fliplr(W),W(2:2001)];                        %形成负半轴及正半轴的2N+1个角频率采样点
F = [fliplr(F),F(2:2001)];                         %形成对应于W的F(jw)的值
subplot(2,1,1);
plot(t,f);
axis([0 2.1 0 1.1])
xlabel('t');ylabel('f(t)');
title('f(t)=exp(-2t)*u(t) ');
subplot(2,1,2);
plot(W,F);
axis([-6 6 0 0.6])
xlabel('\omega');ylabel('F(\omega)');
title('f(t)的傅里叶变换F(\omega)');
%End