demo5.m

这是一个 York大学开发的FDTD代码。很好用的工具

% uses up from demo0
disp('Constant cosine-waves with window')


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)')
x=cos(2*pi*f0'*t);
x=1+ones(1,size(f0,2))*x;
title('Cosine waves')
xlabel('Time')
plot(t,x)
input('Any key to continue')

disp(' Window x');
%Half Gaussian
%w=exp(-(t./(0.5*Tp)).^2);
%Full Gaussian
w=exp(-((t-Tp/2)./(0.2*Tp)).^2);
x=x.*w.*N/sum(w);
title('Windowed data and Window')
plot(t,w,t,x);
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);

title('Discrete Fourier Transform Spectra of Windowed data')
xlabel('Frequency/fs')
ylabel ('abs(X)')
plot(f/fs,abs(XD),'-',f0/fs,ones(1,size(f0,2)),'+')