X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?p=CreaPhase.git;a=blobdiff_plain;f=octave_packages%2Fsignal-1.1.3%2Fbesself.m;fp=octave_packages%2Fsignal-1.1.3%2Fbesself.m;h=44405ab88b0710367383e4b2fe6c8d57c91737bf;hp=0000000000000000000000000000000000000000;hb=f5f7a74bd8a4900f0b797da6783be80e11a68d86;hpb=1705066eceaaea976f010f669ce8e972f3734b05

diff --git a/octave_packages/signal-1.1.3/besself.m b/octave_packages/signal-1.1.3/besself.m
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+## Copyright (C) 1999 Paul Kienzle <pkienzle@users.sf.net>
+## Copyright (C) 2003 Doug Stewart <dastew@sympatico.ca>
+## Copyright (C) 2009 Thomas Sailer <t.sailer@alumni.ethz.ch>
+##
+## 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/>.
+
+## Generate a bessel filter.
+## Default is a Laplace space (s) filter.
+## 
+## [b,a] = besself(n, Wc)
+##    low pass filter with cutoff pi*Wc radians
+##
+## [b,a] = besself(n, Wc, 'high')
+##    high pass filter with cutoff pi*Wc radians
+##
+## [b,a] = besself(n, [Wl, Wh])
+##    band pass filter with edges pi*Wl and pi*Wh radians
+##
+## [b,a] = besself(n, [Wl, Wh], 'stop')
+##    band reject filter with edges pi*Wl and pi*Wh radians
+##
+## [z,p,g] = besself(...)
+##    return filter as zero-pole-gain rather than coefficients of the
+##    numerator and denominator polynomials.
+## 
+## [...] = besself(...,'z')
+##     return a discrete space (Z) filter, W must be less than 1.
+## 
+## [a,b,c,d] = besself(...)
+##  return  state-space matrices 
+##
+## References: 
+##
+## Proakis & Manolakis (1992). Digital Signal Processing. New York:
+## Macmillan Publishing Company.
+
+function [a, b, c, d] = besself (n, W, varargin)
+  
+  if (nargin>4 || nargin<2) || (nargout>4 || nargout<2)
+    print_usage;
+  end
+
+  ## interpret the input parameters
+  if (!(length(n)==1 && n == round(n) && n > 0))
+    error ("besself: filter order n must be a positive integer");
+  end
+
+  stop = 0;
+  digital = 0;  
+  for i=1:length(varargin)
+    switch varargin{i}
+    case 's', digital = 0;
+    case 'z', digital = 1;
+    case { 'high', 'stop' }, stop = 1;
+    case { 'low',  'pass' }, stop = 0;
+    otherwise,  error ("besself: expected [high|stop] or [s|z]");
+    endswitch
+  endfor
+
+
+  [r, c]=size(W);
+  if (!(length(W)<=2 && (r==1 || c==1)))
+    error ("besself: frequency must be given as w0 or [w0, w1]");
+  elseif (!(length(W)==1 || length(W) == 2))
+    error ("besself: only one filter band allowed");
+  elseif (length(W)==2 && !(W(1) < W(2)))
+    error ("besself: first band edge must be smaller than second");
+  endif
+
+  if ( digital && !all(W >= 0 & W <= 1))
+    error ("besself: critical frequencies must be in (0 1)");
+  elseif ( !digital && !all(W >= 0 ))
+    error ("besself: critical frequencies must be in (0 inf)");
+  endif
+
+  ## Prewarp to the band edges to s plane
+  if digital
+    T = 2;       # sampling frequency of 2 Hz
+    W = 2/T*tan(pi*W/T);
+  endif
+
+  ## Generate splane poles for the prototype bessel filter
+  [zero, pole, gain] = besselap(n);
+
+  ## splane frequency transform
+  [zero, pole, gain] = sftrans(zero, pole, gain, W, stop);
+
+  ## Use bilinear transform to convert poles to the z plane
+  if digital
+     [zero, pole, gain] = bilinear(zero, pole, gain, T);
+  endif
+
+  ## convert to the correct output form
+  if nargout==2, 
+    a = real(gain*poly(zero));
+    b = real(poly(pole));
+  elseif nargout==3,
+    a = zero;
+    b = pole;
+    c = gain;
+  else
+    ## output ss results 
+    [a, b, c, d] = zp2ss (zero, pole, gain);
+  endif
+
+endfunction