Theory of microwave coupled-line networks

The multiwire line forms the basis of many practical microwave filtering and coupling circuits. It also has considerable importance as a circuit element in formal synthesis procedures. This paper is concerned with a tutorial presentation of the various methods of analysis for such multiwire lines leading to a number of different equivalent circuits, and with the use of these for synthesis and design. The treatment is restricted to the case of uniform commensurate lines with homogeneous dielectric. Where possible, a unifying approach based on general equivalent circuits is used and this permits the design of some well-known microwave structures to be seen from a somewhat different viewpoint. Some gaps in the existing design procedures for some components are identified and it may be that the methods of analysis and synthesis presented here could lead to new solutions.