Isolation performance of a non-uniform capacitively loaded mushroom-type EBG structure

An equivalent transmission line approach is presented to quantify the wider band gap properties of non-uniform capacitively loaded mashroom-type electromagnetic bandgap (EBG) devices. The approach is based on the observation that the band gap properties of the EBG device within a parallel plate waveguide directly correspond to the attenuation factor of an equivalent homogeneous material slab. Moreover, it is demonstrated that a non-uniform capacitively N-loaded mushroom-type EBG can be decomposed into N equivalent attenuation factors. When the non-zero values of these attenuation factors spectrally overlap, then a cumulative broadband attenuation effect takes place that essentially explains the wide bandgap properties of such devices.