Characterization of passive systems through their closed-loop LQG characteristic values

A characterization of passivity of linear, time-invariant, strictly proper systems is provided. It is based on the LQG balancing technique of [1]. The main result is that the LQG characteristic values
(\mu_{i}'s)
of passive systems are less than 1. Further, if asymptotic stability is assumed, then
\mu_{i} < 1
.