Numerical solution for nonreciprocal inhomogeneous waveguide interface

Mode matching is used to analyse the interface between a reciprocal homogeneous waveguide and a nonreciprocal inhomogeneous waveguide. The configuration used for the nonreciprocal structure is that of the twin-slab ferrite-loaded waveguide. The investigation is restricted to symmetrical E-plane loading, and to lossless structures in which only one mode may propagate. Based on the analysis, the interface and the nonreciprocal waveguide are described by relatively simple equivalent transmission circuits. In these circuits, unique equivalent transmission-line characteristic admittances are defined for the nonreciprocal waveguide. Results show that although the phase coefficients in the two directions of propagation can be very different, the equivalent characteristic admittances are nearly the same. Measurements on a practical version of the twin-slab configuration yield similar results. It is also noted that the energy stored, which is associated with the inhomogeneous interface, does not depend solely on the type of modes excited, in contrast to the case of (reciprocal) dielectric loading.