## On the Passivity Criterion for LTI N-PortsS. Boyd and L. O. Chua
Existing proofs of the passivity criterion for linear, time-invariant,
distributed N-ports are either incorrect or too involved, requiring the use of
advanced mathematics such as distribution theory. This paper presents a simple
but completely rigorous proof using only basic real and complex analysis. For
the sake of completeness we have included simple proofs of the Paley-Wiener
theorem and the Poisson formula for the half plane. We show that solvability, a
non-intuitive technical assumption made in rigorous theories of LTI passive
networks, is virtually always satisfied. Finally, we gave a passivity criterion
applicable to N-ports described by general co-ordinates, from which passivity
criteria for any specific representation ( |