Characterization of infinite- and finite-extent coplanar waveguide metamaterials with varied left- and right-handed passbands

Coplanar waveguide (CPW) metamaterials with varied left- (LH) and right-handed (RH) passbands are thoroughly studied in terms of per-unit-length transmission parameters and magnitude/phase of transmission coefficient, respectively. The two metamaterials are constructed by simultaneously loading the lumped or distributed CPW series-capacitive and shunt-inductive elements in periodic intervals. Effective characteristic impedance and propagation constant of these infinite-extent metamaterials are first extracted to give a physical insight into the guided-wave propagation characteristics in the LH/RH passbands. It is further exhibited that the stopband between the LH and RH passbands can be wholly eliminated in the distributed CPW case. The two finite-extent CPW metamaterials with 50-Ω feed lines are then modeled via simple cascaded transmission line theorem. Predicted magnitude and phase of transmission coefficient are confirmed by experiment, showing the distinctive backward- and forward-wave performances in the LH and RH passbands, respectively.