A known electrodynamic approach is generalized to guided-wave structures
using a hypothetical space-dispersive medium with drifting charge carriers
and simultaneously possessing elastic, piezoelectric, and magnetic
properties. On the basis of Maxwell's equations along with the appropriate
equations of medium motion, the power-energy theorem is derived in the
general form involving additional contributions from specific properties
of the medium. The general power-energy relation yields particular
expressions obtained previously for specific cases of the elastic
piezo-dielectrics, magnetized ferrites, and drifting charge carriers in
nondegenerate plasmas. Substantial features of our electrodynamic study
are the allowance for medium losses and the separation of potential fields
peculiar to the slow quasi-static waves which propagate in such active
media independently of the fast electromagnetic waves of curl nature.
Separating the potential fields gives a certain modification of
electromagnetic terms in the power-energy theorem.