Directive EBG Antennas: A Comparison Between Two Different Radiating Mechanisms

This communication compares two different methods for the directivity enhancement of antennas by means of electromagnetic band-gap (EBG) structures. The first approach employs an EBG material working inside the band-gap to create a resonator, where a radiator is placed in between a groundplane and the EBG cover. The second mechanism adopts an EBG structure, working at the edge of the band-gap and embedding a radiating source to excite a proper Bloch wave. The methods are benchmarked in terms of directivity with reference to several optimized two-dimensional configurations, based on either square or triangular lattices of dielectric rods. For a set of selected configurations, the comparison is carried out in terms of electrical and geometrical parameters, as well as with respect to their frequency behaviour and efficiency. The resonator antenna achieves the highest directivity, but it turns out to be less efficient and is outranked by the other method when few rods per layer are employed. Strengths and weaknesses of the two approaches are fully discussed together with their generalization beyond the particular cases.