s Design of Planar/Coplanar Compact Band-Stop Filter Using SGS Resonators and Multi-Interdigital Capacitors

This letter presents, a novel compact planar/coplanar Band-Stop Filter (BSF) using octagonal slotted ground structure (SGS) in combination with a multi interdigital (MIDC) and compensated capacitors (MIDC), while the coupling matrix method is used in order to improve the filter characteristics. The filters will be realized through direct electromagnetic coupling and slow wave effect methods. The proposed filters have lower and higher cut-off frequencies of 3.4 GHz and 7.3 GHz respectively. Better compactness of the structure and symmetry of the frequency response have been achieved as well as two reflection zeros close to the stop band have been obtained. A comparison between simulation and experimental results confirms the validity of the proposed design approach. The compact planar filter occupies an area of (0.52λg x 0.34λg) at a guide wavelength λg = 29 mm and an area of (0.51λg x 0.49λg) with λg = 27 mm. Both band stop filters have been fabricated and measured. Measurements are in good agreement with simulation results. This paper reviews some promising patents on design of planar/coplanar compact band-stop filter using SGS resonators and multiinterdigital capacitors.