Design of Defected Ground Band Pass Filters Using Stepped Impedance Resonators

In this paper, band-pass filters based on the microstrip configuration and utilizing coupled defected ground structures are presented. The 50 Ω microstrip line has a gap discontinuity in the middle and characterized by stepped impedance resonators on either half. The four fractal geometries tested for defected ground are the first and second iterations of the modified Moore curve, the closed staircase curve and a dual concentric closed staircase curve. The filters have a compact size and planar geometry. The modified Moore first iteration has a measured pass band from 2.27 GHz to 11.86 GHz, whereas the second iteration has a measured pass band from 1.85 GHz to 6.71 GHz. The measured pass band of the closed staircase filter is from 2.38 GHz to 7.21 GHz. The dual-concentric closed-staircase DGS filter offers a dual-band response with the measured pass band being from 2.41 GHz to 5.01 GHz and from 5.81 GHz to 8.35 GHz. All the filters can have applications in the UWB region. A parametric study showing the effect of the various controlling parameters is also presented.