Question: Synthesis of RF multiport from arbitrary S matrix

Hi friends,

I need some help on this subject regarding the synthesis of multiport networks.

Given a matrix of values (frequency-independent) that fullfills the necessary conditions of the S matrix of a reciprocal and lossless network (i.e. it is symmetric and unitary):
a) does it always exist a passive network described by such a matrix? (i.e. are the above-mentioned conditions sufficient?)
b) if not, under which conditions does it exist?
c) with which method can it be synthesized?

Tips or bibliographical references are very appreciated.
Best regards

Z

Hi again,

Although there was not any reply yet, I present a variation of the question: replace the condition of "lossless" by "passive".
Does somebody have an idea?
Regards

Z