--- /dev/null
+## Copyright (C) 2011 Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope 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.
+##
+## LTI Syncope 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 LTI Syncope. If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## 1. Discrete -> continuous
+## _
+## E = alpha*E + A
+## _
+## A = beta (A - alpha*E)
+## _
+## B = sqrt(2*alpha*beta) * B
+## _ -1
+## C = sqrt(2*alpha*beta) * C * (alpha*E + A) * E
+## _ -1
+## D = D - C * (alpha*E + A) * B
+##
+##
+## 2. Continuous -> discrete
+## _
+## E = beta*E - A
+## _
+## A = alpha (beta*E + A)
+## _
+## B = sqrt(2*alpha*beta) * B
+## _ -1
+## C = sqrt(2*alpha*beta) * C * (beta*E - A) * E
+## _ -1
+## D = D + C * (beta*E - A) * B
+
+## Special thanks to Andras Varga for the formulae.
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2011
+## Version: 0.1
+
+function [Ar, Br, Cr, Dr, Er] = __dss_bilin__ (A, B, C, D, E, beta, discrete)
+
+ if (discrete)
+ EpA = E + A;
+ s2b = sqrt (2*beta);
+ if (rcond (EpA) < eps)
+ error ("d2c: E+A singular");
+ endif
+ CiEpA = C / EpA;
+
+ Er = EpA;
+ Ar = beta * (A - E);
+ Br = s2b * B;
+ Cr = s2b * CiEpA * E;
+ Dr = D - CiEpA * B;
+
+ ## Er = E + A;
+ ## Ar = beta * (A - E);
+ ## Br = sqrt (2*beta) * B;
+ ## Cr = sqrt (2*beta) * C / (E + A) * E;
+ ## Dr = D - C / (E + A) * B;
+ else
+ bEmA = beta*E - A;
+ s2b = sqrt (2*beta);
+ if (rcond (bEmA) < eps)
+ error ("c2d: beta*E-A singular");
+ endif
+ CibEmA = C / bEmA;
+
+ Er = bEmA;
+ Ar = beta*E + A;
+ Br = s2b * B;
+ Cr = s2b * CibEmA * E;
+ Dr = D + CibEmA * B;
+
+ ## Er = beta*E - A;
+ ## Ar = beta*E + A;
+ ## Br = sqrt (2*beta) * B;
+ ## Cr = sqrt (2*beta) * C / (beta*E - A) * E;
+ ## Dr = D + C / (beta*E - A) * B;
+ endif
+
+endfunction