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/dsisoftv3/dsisoftv3/main/butw.m
function [dataout]=butw(datain,low1,low2,high1,high2,Rp,Rs) %[dataout]=butw(datain,low1,low2,high1,high2,Rp,Rs) % %Zero phase Butterworth bandpass filter. % %low1,low2,high1,high2 - frequencies describing the filter %Filter is designed so that region between 'low2' and 'high1' is attenuated %by less than 3 dB and region before 'low1' and after 'high2' is attenuated %by at least 20 dB. %Rp - attenuation max within pass band (dB) (around 3 dB is good) %Rs - attenuation at outside frequencies (dB) (try 20 or 40) % %All frequencies are in Hertz (Hz) % %Note - uses functions from signal processing toolbox % %DSI customized VSP processing software %written by Kristen Beaty January, 1998 %$Id: butw.m,v 3.0 2000/06/13 19:19:55 gilles Exp $ %$Log: butw.m,v $ %Revision 3.0 2000/06/13 19:19:55 gilles %Release 3 % %Revision 2.0 1999/05/21 18:45:18 mah %Release 2 % %Revision 1.2 1999/05/17 14:58:15 mah %fixed up help message % %Revision 1.1 1999/01/06 19:09:02 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]=butw(datain,low1,low2,high1,high2,Rp,Rs)'); int=datain.fh{8}; %sampling interval (s) Ny=1/(int*2); %Nyquist frequency Wp=[low2 high1]./Ny; %pass frequencies (normalized) Ws=[low1 high2]./Ny; %outside frequencies (normalized) %build Butterworth filter function [n,Wn]=buttord(Wp,Ws,Rp,Rs); [b,a]=butter(n,Wn); dataout=datain; nrec=datain.fh{12}; for COUNT=1:nrec %loop over records ntr=datain.th{COUNT}(12,1); for tr=1:ntr in=datain.dat{COUNT}(:,tr)'; out=filtfilt(b,a,in); %apply filter dataout.dat{COUNT}(:,tr)=out'; end %loop over traces end %loop over records