Band rejection design for Chebyshev modulated dumbbell DGS low pass filters

The novel technique of band rejection design of Chebyshev dumbbell EBG assisted low pass filters (LPFs) is presented in this paper. The ground plane of a standard 50-ohm transmission line is perturbed by dumbbell electromagnetic bandgap structure (EBG) or called defected ground structure (DGS) to generate ultra rejection band that is beneficial to higher order harmonic suppression. The purpose of the paper is to develop a method to calculate band rejection dependent filling factor (FF) of a Chebyshev modulated dumbbell DGS physical dimension through the use of predefined side lobe level (SLL) rejection ratio, Bragg's theory and Chebyshev polynomial. Unlike that of circular and rectangular EBG cells, the filling factor of dumbbell shaped DGS has been re-defined. The rejection trend under re-defined FF is consistent with the pre-defined SLL. A comparison of Chebyshev circular EBG LPF and proposed Chebyshev dumbbell DGS has been evaluated. The proposed dumbbell DGS LPF has better rejection bandwidth than circular EBG LPF.