Experimental Investigation of Transmission-line Representations of Microwave Periodic Circuits

Research is presented on transmission line models of a type of periodically-loaded waveguide which is important to the design of high power traveling wave tubes and linear accelerators. A simple and well-known model, referred to as the single-line model, is descr bed in terms of a single transmission line periodically loaded ith shunt susceptances; the model has the limitation that direct coupling between neighboring irises is not accounted for when the simple one-port element is used to represent the network properties of a thin transverse iris. The model is then improved in such a way that this limitation is removed to a first order of approximation; the iris is assumed to behave as a shunt two-port network coupling smooth transmission lines having the properties of appropriate normal waveguide modes. This latter formulation of the two-port representation of a waveguide iris is new. It is found experimentally that the new model of the structure, referred to as the two-line model, covers a class of circuits used in practical applications. (Author).