Distributed circuit design with transmisssion line elements

A short length of transmission line can be chosen as a basic circuit element. Systems containing such elements can then be synthesized to do an amazing number of things. For example, commensurate lines, all multiples of a given length with differing characteristic impedances but with common propagation constant, can be interconnected to realize microwave filters, broad-band transformers, broad-band delay lines with amplitude selectivity, and distributed RC structures. The fundamental ideas underlying the synthesis of commensurate transmission line circuits are presented in this paper in a tutorial fashion. The presentation is based on the scattering formalism and Richard´s Theorem. The discussion is liberally sprinkled with design illustrations chosen from current practice.