examp_gabmul.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

%EXAMP_GABMUL  Time-frequency localization by a Gabor multiplier
%
%   This script creates several different time-frequency symbols
%   and demonstrate their effect on a random, real input signal.
%
%
%
%     This figure shows the symbol (top plot, only the positive frequencies are displayed),
%     the input random signal (bottom) and the output signal (middle).

% 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/>.

disp('Type "help examp_gabmul" to see a description of how this example works.');

% Setup some suitable parameters for the Gabor system
L=480;
a=20;
M=24;

b=L/M;
N=L/a;

% Plotting initializations
t_axis = (0:(M-1))*a;
f_max = floor(N/2)-1;
f_range = 1:(f_max+1);
f_axis = f_range*b;

xlabel_angle = 7;
ylabel_angle = -11;

% Create a tight window, so it can be used for both analysis and
% synthesis.
g=cantight(a,M,L);

% Create the random signal.
f=randn(L,1);

% ------- sharp cutoff operator ---------
% This cuts out a circle in the TF-plane. 
symbol1=zeros(M,N);

for m=0:M-1
  for n=0:N-1
    if (m-M/2)^2+(n-N/2)^2 <(M/4)^2
      symbol1(m+1,n+1)=1;
    end;
  end;
end;

% The symbol as defined by the above loops is centered such
% that it keeps the high frequencys. To obtain the low ones, we
% move the symbol along the first dimension:
symbol1=fftshift(symbol1,1);


% Do the actual filtering
ff1=gabmul(f,symbol1,g,a);


% plotting
figure(1);

if isoctave
  subplot(3,1,1);
  mesh(t_axis,f_axis,symbol1(f_range,:));
  xlabel('Time');
  ylabel('Frequency');

  subplot(3,1,2);
  plot(real(ff1),';;');
  
  subplot(3,1,3);
  plot(f,';;');
else
  subplot(3,1,1);
  mesh(t_axis,f_axis,symbol1(f_range,:));
  xlabel('Time','rotation',xlabel_angle);
  ylabel('Frequency','rotation',ylabel_angle);
%  axis tight;

  subplot(3,1,2);
  plot(real(ff1));
%  axis tight;
  
  subplot(3,1,3);
  plot(f);
%  axis tight;
end;


% ---- Tensor product symbol, keep low frequencies.
t1=pgauss(M);
t2=pgauss(N);

symbol2=fftshift(t1*t2',2);

% Do the actual filtering
ff2=gabmul(f,symbol2,g,a);


figure(2);

if isoctave
    
  subplot(3,1,1);
  mesh(t_axis,f_axis,symbol2(f_range,:));
  xlabel('Time');
  ylabel('Frequency');

  subplot(3,1,2);
  plot(real(ff2),';;');
  
  subplot(3,1,3);
  plot(f,';;');
  
else
  
  subplot(3,1,1);
  mesh(t_axis,f_axis,symbol2(f_range,:));
%  axis tight;
  xlabel('Time','rotation',xlabel_angle);
  ylabel('Frequency','rotation',ylabel_angle);

  subplot(3,1,2);
  plot(real(ff2));
%  axis tight;

  subplot(3,1,3);
  plot(f);
%  axis tight;
end;


% ----- Tensor product symbol, keeps middle frequencies.
t1=circshift(pgauss(M,.5),round(M/4))+circshift(pgauss(M,.5),round(3*M/4));
t2=pgauss(N);

symbol3=fftshift(t1*t2',2);

% Do the actual filtering
ff3=gabmul(f,symbol3,g,a);


figure(3);

if isoctave

  subplot(3,1,1);
  mesh(t_axis,f_axis,symbol3(f_range,:));
  xlabel('Time');
  ylabel('Frequency');
  
  subplot(3,1,2);
  plot(real(ff3),';;');
  
  subplot(3,1,3);
  plot(f,';;');
  
else
    
  subplot(3,1,1);
  mesh(t_axis,f_axis,symbol3(f_range,:));
  xlabel('Time','rotation',xlabel_angle);
  ylabel('Frequency','rotation',ylabel_angle);

  subplot(3,1,2);
  plot(real(ff1));
%  axis tight;

  subplot(3,1,3);
  plot(f);
%  axis tight;
end;

% % ---- Tensor product symbol, keep low frequencies.
% t1=pgauss(M);
% t2=pgauss(N);
% 
% symbol2=fftshift(t1*t2',2);
% 
% % Do the actual filtering
% ff2=gabmul(f,symbol2,g,a);
% 
% 
% figure(2);
% subplot(3,1,1);
% mesh(symbol2);
% 
% if isoctave
%   subplot(3,1,2);
%   plot(real(ff2),';;');
%   
%   subplot(3,1,3);
%   plot(f,';;');
% else
%   subplot(3,1,2);
%   plot(real(ff2));
%   
%   subplot(3,1,3);
%   plot(f);
% end;
% 
% % ----- Tensor product symbol, keeps middle frequencies.
% t1=circshift(pgauss(M,.5),round(M/4))+circshift(pgauss(M,.5),round(3*M/4));
% t2=pgauss(N);
% 
% symbol3=fftshift(t1*t2',2);
% 
% % Do the actual filtering
% ff3=gabmul(f,symbol3,g,a);
% 
% 
% figure(3);
% subplot(3,1,1);
% mesh(symbol3);
% 
% if isoctave
%   subplot(3,1,2);
%   plot(real(ff3),';;');
%   
%   subplot(3,1,3);
%   plot(f,';;');
% else
%   subplot(3,1,2);
%   plot(real(ff3));
%   
%   subplot(3,1,3);
%   plot(f);
% end;
%