New microwave network identities for CAD modeling

Network identities that allow one to model two, three, or four symmetric and homogeneous coupled lines by using ideal 180 degrees hybrids and separate uncoupled transmission lines representing each characteristic mode are presented. The identities have been found useful in computer modeling of complicated networks. In addition, the flow-graph models help to understand intuitively the network conditions for isolation, etc. The models require prior knowledge of the mode propagation constants and characteristic impedances, but there are numerous techniques and available programs to obtain these quantities.<>