Periodic Bandgap Structures

PBG structures are periodic in nature, which may be realized by drilling, cutting and etching on the metal or substrates. They may be formed in the ground plane or over the substrate. 

 

The transmission line can also be modified to form PBG characteristics without having any perturbation in the ground plane [23]-[24], [25]. This new idea can be extended to filter, antenna and other microwave component and devices where the complexity of packaging is minimized. The PBG configuration is categorized as shown in Fig. 2.1. On the basis of dimension, PBG structures may be divided into 1-D, 2-D and 3-D PBGSs. Planar PBG structures and their applications to antennas has been reported in [32]. Following are the descriptions of different PBG structures.

Fig. 2.1: Different PBG structures

·        Bumpy Surface

Several configurations have been reported in the literature. The first structure is made by drilling a periodic pattern of holes in the substrate or etching a periodic pattern of circles in the ground plane.  A bumpy metal sheet [26]-[27] has a narrow surface wave band-gap. Electric field wraps around the bumps at the upper edge of the band gap and the electric field also extends across the bumps at the lower edge of the band-gap, hence a slow wave structure is formed. Bumpy surface is shown in Fig. 2.2.