A compact coplanar waveguide metamaterial-inspired line and its use in tunable narrow bandpass filters

In this paper, novel cells, arrays, and reconfigurable metamaterial-inspired coplanar waveguide lines are studied. The novelty stems from the control of the so-called electric and magnetic plasma frequencies by properly designing the loading elements. In particular, wide shunt wires permit one to control the upper band rejection levels, while exhibiting a left-handed nature within the pass band, by showing a significant enhancement of the loaded-Q quality factors. Moreover, improved out-of-band rejection properties have been obtained by the use of cascaded basic cells and optimization processes. In a last stage, tunable configurations are studied by means of varactor-loaded split rings. Two different arrangements with one or three cells are optimized in terms of the reflection coefficient. The interpretation of the results is based on full-wave electromagnetic analysis and measured responses of different prototypes designed for microwave operation.