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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | % invfdemo demonstrates Inverse Filtering
% $Id: invfdemo.m 5090 2008-06-05 08:12:04Z schloegl $
% Copyright (C) 1997-2002,2008 by Alois Schloegl <a.schloegl@ieee.org>
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
load eeg8s.mat; % load signal
ly=length(eeg8s);
Fs=128;
%a=earpyw(eeg8s',11); % Calculates AR(11) parameters with Yule-Walker method
a=lattice(eeg8s',11); % Calculates AR(11) parameters with Yule-Walker method
% The AR parameters are the weight taps of IIR Filter
isig=filter([1 -a],1,eeg8s); % Inverse filtering
subplot(221);
plot((1:ly)/Fs,eeg8s);
title('Signal');
xlabel('t [sec]')
subplot(223);
plot((1:ly)/Fs,isig);
xlabel('t [sec]')
title('Inverse filtered process');
subplot(222);
H=abs(fft(eeg8s,128)/ly).^2;
plot(1:Fs,H);
%plot([H mean(H)*ones(Fs,1)]);
ylabel('S(f)')
xlabel('f [Hz]')
title('Spectrum of original signal');
subplot(224);
H=abs(fft(isig,128)/ly).^2;
plot(1:Fs,H);
%plot([H mean(H)*ones(Fs,1)]);
ylabel('S(f)')
xlabel('f [Hz]')
title('Spectrum of inverse filtered signal');
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