Tunable bandstop defected ground structure resonator using reconfigurable dumbbell-shaped coplanar waveguide

A modification of the conventional dumbbell-shaped coplanar waveguide defected ground structure (DGS) is proposed. This modification permits the continuous tuning of the rejected frequencies by using reconfiguration technique and it allows the control of the DGS equivalent-circuit model. The modified DGS possesses two-dimensional symmetry, hence, it has been studied under different symmetry conditions and the corresponding equivalent-circuit model in each case has been developed. Based upon this study, a tunable bandstop DGS resonator is proposed. 19% tuning range centered at 3.7 and 7.4 GHz, respectively, is achieved. The equivalent-circuit model of the resonator is also developed. All proposed structures have been fabricated. Measurements as well as three-dimensional simulations are found to be in a very good agreement with theoretical predictions. Index Terms--Coplanar waveguide (CPW), defected ground structure (DGS), tunable bandstop resonator.