Representation by Equivalent circuit of the Integral methods in Microwave passive elements

The introduction of the concept of "Admittance Operator" allows a systematic procedure for the computation of passive microwave circuits elements by integral method. First, an "equivalent circuit" of the electromagnetic problem has to be established. This circuit includes sources and elements which generally are self-adjoint operators. The following procedure consists in expressing the trial functions as "virtual" sources (voltage or currents) which do not consume energy. The efficiency of this procedure is described in the analysis of some structures which include several discontinuities with metallic elements or surface impedances.