EIGENVALUE APPROACH TO THE EFFICIENT DETERMINATION OF THE HYBRID AND COMPLEX SPECTRUM OF INHOMOGENEOUS, CLOSED WAVE-GUIDE

Many hybrid modes are required in computing the fields scattered from discontinuities in structures such as finline, coplanar waveguide, or microstrip. The authors present a new analytical method based on an ei genvalue formulation of the generalized telegrapher's equations discre tized by using the modes at cutoff as an expanding set, This approach produces a compact theoretical model while providing at the same time an effective algorithm for finding the characteristics of many modes, including their below cutoff and complex behavior, The theoretical app roach gives some direct insights about the appearance of complex modes , Due to the explicit formulation of the eigenvalue equation for the c omplex propagation constant, the proposed method overcomes some of the typical drawbacks of the currently used algorithms, such as the limit ed numerical accuracy and efficiency, the numerical degeneracy and app earance of spurious solutions, the inability to trace the characterist ics of degenerate modes, Numerical results for ordinary and complex pr opagation in finline show excellent agreement with existing data.