gusucode.com > DSISoft是由加拿大地质调查局发布的用于垂直地震剖面(VSP)数据处理的免费软件包 > dsisoftv3/main/equa.m
function [dataout]=equa(datain,fmin,fmax,fwind,taper,window) %[dataout]=equa(datain,fmin,fmax,fwind,taper,window) % %Performs spectral balancing using a sliding frequency window linear bandpass %filter with tapers overlapping at the half way point. An agc is applied to %each filtered signal and the frequency ranges are then recombined. Similar %to INSIGHT module EQUA. % %fmax, fmin = maximum and minimum frequencies in the data (Hz) %fwind = width of each bandpass filter to be applied (Hz) %taper = width of linear taper of each bandpass filter (Hz) (around 2-5 Hz) %window = length of agc window to be used (s) % %DSI customized VSP processing software %written by K.S. Beaty January, 1998 %$Id: equa.m,v 3.0 2000/06/13 19:20:12 gilles Exp $ %$Log: equa.m,v $ %Revision 3.0 2000/06/13 19:20:12 gilles %Release 3 % %Revision 2.0 1999/05/21 18:45:33 mah %Release 2 % %Revision 1.1 1999/01/06 19:09:03 kay %Initial revision % % %Copyright (C) 1998 Seismology and Electromagnetic Section/ %Continental Geosciences Division/Geological Survey of Canada % %This library is free software; you can redistribute it and/or %modify it under the terms of the GNU Library General Public %License as published by the Free Software Foundation; either %version 2 of the License, or (at your option) any later version. % %This library 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 %Library General Public License for more details. % %You should have received a copy of the GNU Library General Public %License along with this library; if not, write to the %Free Software Foundation, Inc., 59 Temple Place - Suite 330, %Boston, MA 02111-1307, USA. % %DSI Consortium %Continental Geosciences Division %Geological Survey of Canada %615 Booth St. %Ottawa, Ontario %K1A 0E9 % %email: dsi@cg.nrcan.gc.ca disp('[dataout]=equa(datain,fmin,fmax,fwind,taper,window)'); tstart=datain.fh{9}; %start time in seconds int=datain.fh{8}; %sampling interval in seconds %convert agc 'window' from seconds to indexes w=round(window./int)+1; pt=round(w/2); %index of point in the centre of the window Ny=1./(int.*2); %Nyquist frequency npts=datain.fh{7}; %number of points in each trace N=2^(nextpow2(npts)+1); %number of points to be used in fft f=2*Ny*(0:N/2-1)/N; %frequency vector %create filter function in frequency domain x=[0 0 1 1 0 0]; filt=zeros(N,1); %initialize filter vector if w==npts pt=npts; elseif w>npts %error check for agc error('choose a smaller window') end %if/else nfreq=(taper+fmax-fmin)./(taper+fwind); nfreq=round(nfreq); nrec=datain.fh{12}; %number of records dataout=datain; for COUNT=1:nrec dataout.dat{COUNT}(:,:)=0; %initialize dataout.dat end %loop over records for k=1:nfreq low=fmin+(k-1).*(fwind+taper); high=low+fwind; %======================================= xf=[0 (low-taper) low high (high+taper) f(N/2)]; m=interp1(xf,x,f); filt(1:N/2)=m; m2=fliplr(m); filt(N/2+1)=0; filt(N/2+2:N)=m2(1:length(m2)-1); %'filt' is filter function in frequency domain for COUNT=1:nrec %loop over records ntr=datain.th{COUNT}(12,1); %number of traces in this record filtmat=ndgrid(filt,1:ntr); %create filter matrix in_freq=fft(datain.dat{COUNT},N); %performs N points fft on columns out_freq=zeros(N,ntr); %initialize out_freq=in_freq.*filtmat; %multiply in freq. domain out=ifft(out_freq,N); %N points inverse fft freq=real(out(1:npts,:)); %============apply agc================= fact=sum(abs(freq(1:w,:)))./w; factgr=meshgrid(fact,1:pt); freq_agc(1:pt,:)=freq(1:pt,:)./factgr; for k=1:npts-w; fact=fact-abs(freq(k,:))./w+abs(freq(k+w,:))./w; freq_agc(k+pt,:)=freq(k+pt,:)./fact; end %for i=npts-w+1:npts; factgr=meshgrid(fact,i); freq_agc(i,:)=freq(i,:)./factgr; %====================================== dataout.dat{COUNT}=dataout.dat{COUNT}+freq_agc; %add balanced frequency end %loop over records %error check re=real(out(1:npts,1)); im=imag(out(1:npts,1)); for i=npts:-1:1 rat(i)=im(i)./re(i); end; r=find(rat>10^-6); if ~ isempty(r) error('imaginary part of inverse fft is too large'); end %if end %loop over frequency windows