Design of compact coplanar bandstop filter composed on open‐loop‐ring resonator and defected ground structure (DGS)

Abstract

AbstractDesign of a novel compact bandstop filter composed on an open‐loop‐ring resonator and a defected ground structure (DGS) for coplanar waveguide is proposed and investigated. A simple coplanar open‐loop‐ring resonator has been designed and tested for the stop‐band from 3.9 to 4.3 GHz with tree transmission zeroes inside the stop‐band. Two almost symmetrical poles are obtained on both sides of the stop‐band. Then the proposed broad band bandstop filter based on the one open‐loop‐ring resonator has been transformed to the bandstop filter with a narrower stop‐band but with improved pass‐ and stop‐band characteristics. It is realized by adding a conventional rectangular DGS slot inside the open‐loop‐ring. The equivalent circuit model has been proposed to describe the behaviour of the bandstop filters. The improved bandstop filter introduces the stop‐band from 3.75 to 5.3 GHz with two transmission zeroes within and more than −20 dB rejection. The total size of the proposed structure is 13.8 × 13.4 mm2. Both bandstop filters have been fabricated and measured. Measurements are in good agreement with simulation results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 478–483, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24905