Periodically loaded transmission line media/materials with infinite extent on coplanar waveguide: Guided- wave performances

Abstract

This paper aims to give a unified characterization of various periodically loaded transmission line media/materials with infinite extent on coplanar waveguide (CPW) in terms of two fundamental per-unit-length (PUL) transmission parameters, i.e., frequency-dispersive/complex characteristic impedance and propagation constant. Regardless of varied periodic loading elements, a self-calibrated method of moments (MoM) is in general applied to numerically de-embedding the two-port ABCD matrix of core finite-extent CPW sections, thus deriving these two PUL parameters. Firstly, infinite-extent CPW with series-inductive loaded in periodical intervals is studied as the electromagnetic bandgap (EBG) material. Two PUL parameters are extracted to provide a physical insight into slow-wave and bandstop behaviors of guided-wave. Secondly, two periodic CPW structures with series-capacitive or shunt-inductive loading are modeled to show the normal passbands of guided-wave with paralleled phase/group velocities. Lastly, CPW metamaterials with simultaneous series-capacitive and shunt- inductive loading are investigated to demonstrate the guided-wave performances in the distinctive left- (LH) and right-handed (RH) passbands. It is quantitatively verified that the stopband between the LH and RH passbands can be wholly eliminated by periodically loading distributed CPW elements with enhanced extent. Several finite-extent periodically loaded CPW circuits with 50-Omega feed lines are fabricated and measured to provide an experimental validation.