Normal mode analysis of waveguide devices. I. Theory

A normal mode formulism is developed for the purpose of treating transition structures in waveguide devices. This development includes: (1) a coupled mode theory representation of local normal modes, (2) a four-port scattering model that connects the normal modes at a general transition, (3) a general expression for power transfer between normal modes at an abrupt transition, and (4) a demonstration of reciprocity.<>