## Copyright (C) 1998 Kai P. Mueller
##
## This file is part of Octave. 
##
## Octave 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 2, or (at your option) any 
## later version. 
## 
## Octave 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 Octave; see the file COPYING.  If not, write to the Free 
## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA. 

## -*- texinfo -*-
## @deftypefn {Function File } { @var{wsys} =} wgt1o (@var{vl}, @var{vh}, @var{fc})
## State space description of a first order weighting function.
## 
##  Weighting function are needed by the H2/H_infinity design procedure.
##  These function are part of thye augmented plant P (see hinfdemo
##  for an applicattion example).
## 
##  vl = Gain @@ low frequencies
## 
##  vh = Gain @@ high frequencies
## 
##  fc = Corner frequency (in Hz, *not* in rad/sec)
## @end deftypefn
 
function wsys = wgt1o(vl, vh, fc)
## Written by Kai P. Mueller September 30, 1997

  if (nargin != 3)
    usage("wsys = wgt1o(vl, vh, fc)");
  endif

  if(nargout > 1)
    usage("wsys = wgt1o(vl, vh, fc)");
  endif

  if (vl == vh)
      a = [];
      b = [];
      c = [];
  else
      a = [-2*pi*fc];
      b = [-2*pi*fc];
      c = [vh-vl];
  endif
  d=[vh];

  wsys = ss2sys(a,b,c,d);
endfunction