Computer-aided design of three-dimensional waveguide loaded cavities

The authors developed two simple methods of calculating the power transport through an external waveguide of a loaded cavity utilizing the RF parameters obtained from frequency-domain codes. In the first method the external power loss through an open waveguide is expressed in terms of equivalent circuit coupling parameters between a closed waveguide and a cavity to which it is connected. This equivalent circuit approach is limited in its applicability to structures with high loaded Q values, e.g. Q_L>200. In the second method, the power flow through an external waveguide is calculated from an analysis of the electromagnetic field components of the standing waves in the closed waveguide-cavity structure. The models make use of the MAFIA code to obtain values of structural parameters and fields when an external waveguide is abruptly terminated with a metal surface. Reasonable and encouraging results have been obtained for several loaded cavities whose values of Q_L have been experimentally measured. Of particular interest is the application to low-Q structures such as the relativistic klystron output cavities