Efficient Methods for Determining the Coupling to Wires in Circular Cavities

The electromagnetic field coupling to a loaded thin wire in a cylindrical/coaxial cavity is investigated. Computationally efficient methods are presented for determining the coupling to a thin wire located near a cavity wall in a system of cascaded and/or overlapping coaxial and circular cylindrical cavity sections, and the accuracy and limitations of these methods are established. The sections are coupled through apertures and conducting elements common to more than one section, which may have different axial and radial dimensions and which may be filled with material having different magnetic and electric properties. The loaded thin wire is close to the outer wall of a cavity section and may represent a cable or, perhaps, a conducting tube. The coupling of the cavity field to the wire is determined from an analysis of a distributed voltage and current source model based on transmission line theory as well as via coupled integral equations techniques. The accuracy of the results obtained from these analyses is supported by experimental data measured on a laboratory model of the cavity-wire structure.