Coupling Between Transmission-Line Networks and Homogeneous Media: A Semianalytical Approach

ABSTRACT: Electromagnetic devices that incorporate volumetric networks of transmission lines with electrically small periodicity and cross-sections are extensively used in various applications. Linear tapers can be employed in these configurations to achieve coupling between a homogeneous background medium and the volumetric transmission-line struc-ture. This is beneficial since various transmission-line structures (homogenizable dense networks of transmission lines) are widely utilized to realize exotic electromagnetic proper-ties commonly related to metamaterials. However, optimizing the dimensions of such multiparametric and electrically large devices could be computationally cumbersome. In this work, a simple semianalytic technique is proposed to reduce substantially the required simulation cost for an optimized design. The tapers are modeled semianalytically as consec-utive coplanar components. On the other hand, the transmission-line network is considered as a chain of identical unit cells, the response of which is numerically determined. The semi-analytical result of the taper is combined with the numerical result of the unit cell by cascading the respective transfer matrices. The agreement of the obtained results with the corresponding full-wave simulation data of the whole structure is very good. The decreased computational time required for the proposed approach is demonstrated through severa