Rigorous modal analysis of structures containing inhomogeneous dielectric cylinders

The orthogonal expansion method and modified iterative scattering procedure is proposed to analyze structures containing asymmetrically located, partial-height, or multilayered inhomogeneous dielectric posts. The analysis is based on a novel concept called the hybrid impedance matrix (HIM), which describes the relation between the total scattered electric and magnetic fields obtained from all posts. As a result, the HIM can be easily applied to match it with other known incident fields and finds applications in closed (waveguide junctions, resonators) and open structures (posts in free space for plane-wave excitation). Additionally, a procedure for constructing eigenmode functions describing field components in the inhomogeneous dielectric cylinders is presented. The proposed method has been extensively verified for a rectangular waveguide junction by a finite-difference time-domain software package, as well as our own measurements and, in both cases, very good agreement can be observed.