Highly directive dielectric resonator antennas operating at higher order degenerate band edge modes

In recent years, there is a growing interest in compact high-gain antennas with a single feed for civil/tactical wireless communication systems. Electromagnetic band-gap (EBG) structures with embedded antennas/feeds present an attractive solution due to their high directivity and feeding ease. EBGs have been used to obtain highly directive radiation in two forms: (a) as a substrate utilizing defect resonances (Brown et al., 1993) (b) as a host medium near the band edge frequencies (Bulu et al., 2003). The first group requires comparatively large physical sizes for practical applications (e.g. thicknesses of larger than lambda_o/2). For the latter, one must be careful to operate at the Fabry-Perot (F-P) transmission peak closest to the band edge. The degenerate band edge (DBE) resonances (see Fig. 1c) are of this type, but also have the unique property of exhibiting narrower F-P peaks in the vicinity of the band edge leading to better directional selectivity (Figotin and Vitebskiy, 2006). Consequently, DBE crystals can achieve required levels of high directivity using fewer number of unit cells, resulting in low profile structures.