%MATLAB function y2s.m converts a network's admittance
%matrix, Y, into the appertaining generalized S matrix.
%The function is called up by S = y2s(Z0, Y). It needs
%as its input arguments not only the elements of a
%Y matrix, but also those of a normalizing reference
%impedance matrix, Z0.
%Z0 is a diagonal matrix whose elements are either
%real-valued (e.g., all diagonal elements
%are Z0 = 50 ohms) or complex-valued, i.e., with 
%a capacitive or inductive reactance term.

function[S] = y2s(Z0, Y)

D0 = inv(sqrtm(Z0));
U = diag(ones(length(Z0), 1));
S = D0 * (U-(conj(Z0)*Y))*inv(U + (Z0*Y))*sqrtm(Z0);