%% WINDOWSINE_DEMO3
%%
%% This Matlab m-file demonstrates what happens in DFT analysis as
%% fix the two sinusoidal frequencies to be 5 and 5.5 Hz, fix the DFT
%% length to 8192, and vary the window length from 100 to 1000 in
%% increments of 25.
%%

%-------------------------------------------------------------------
clf;

%-------------------------------------------------------------------
%%% Parameters

f1=5;
f2=5.5;
fs=100;
Tinterv=10;
phi=[0 0];

[x,t]=sum_sine([f1 f2],Tinterv,fs,phi);

win_type='boxcar';
dft_length=8192;


for win_length=100:25:1000
  ind=1:win_length;
  window=feval(win_type,win_length)';

  v=x(ind).*window;
  [Vk,fk]=fr_resp(v,dft_length,fs);

  subplot(311)
  plot(t(ind),v)
  axis([min(t(ind)) max(t(ind)) min(v) max(v)])
  xlabel('Time (seconds)')
  ylabel('v(t)');
  title('Windowed sinusoid')
  fixfont(14,14,14)

  subplot(212)
  plot(fk,10*log10(abs(Vk)))
  axis([-10 10 -30 30])
  xlabel('Frequency (Hz)');
  ylabel('10log_{10}|V[k]|')
  tstr=sprintf('Frequencies:  %0.1f and %0.1f Hz   Window length: %i',...
      f1,f2,win_length);
  title(tstr);
  fixfont(14,14,14)
  disp('Hit return to continue')
  pause
end