Unified Approach to the Derivation of Variational Expression for Electromagnetic Fields

A unified procedure to derive the variational expressions for electromagnetic field problems is presented. It is shown that the variational expressions for a variety of electromagnetic parameters such as, for instance, a resonant frequency, a propagation constant, and an impedance matrix, can be formulated systematically all from "the principle of least action" point of view. It is pointed out that the Maxwell\´s equations themselves can also be derived from the least action principle.