fft_contin.m

经典《信号与系统》教程的matlab例程,对深入理解信号与系统相关概念有很大帮助

% Name:FFT_contin
clear,close all;
fs=input('Type in the sampling frequence fs=');
F=input('Type in F=');
N=fs/F;
M=ceil(log2(N));
N=2^M;
F=fs/N;
Tp=1/F;
T=Tp/N;
t=0:T:Tp;
x=input('Type in the sequence x(t)=');
%==========================================
% Computation of DFT using FFT
%==========================================
Xk=fft(x,N);
Xk=Xk*T*F;
%==========================================
% Plot the spectra curve
%==========================================
k=0:N-1;
subplot(211)
stem(t,x,'.'),title('The original sequence x(nT)')
xlabel('Time t');axis([0,Tp,1.1*min(x),1.1*max(x)])
subplot(212)
stem(k*F,abs(Xk),'r.'),title('The amplitude spectra of x(t)')
xlabel('Frequence in Hz'),axis([0,fs/2,0,1.1*max(abs(Xk))])