demo4.m

这是一个 York大学开发的FDTD代码。很好用的工具

% uses setup from demo0
disp('FFT of truncated Constant cosine-waves')

disp('Generate time and frequency steps')
Ts=Tp/(N)
fs=1/Ts
f=linspace(0,fs*(N-1)/N,N);
disp('Generate time steps for one period (t)');
t=linspace(0,Tp*(N-1)/N,N);



disp('Generate time sequence (x) and plot it against time (t)')
disp('Frequencies:')
f0
x=cos(2*pi*f0'*t);
x=ones(1,size(f0,2))*x;
plot(t,x)
title('Sum of Sine waves')
xlabel('Time')
input('Any key to continue')

disp('Generate DFT (X) of time series (x) and Compare with Fourier transform of continous data');
XD=2*Ts*fft(x);
XD(1)=0.5*XD(1);
plot(f/fs,abs(XD),'o',f0/fs,ones(1,size(f0,2)),'+')
title('Discrete Fourier Transform Spectra (truncation effects)')
xlabel('Frequency/fs')
ylabel('abs(X)')