Experimental Analysis of a Directive Antenna with a 3D-EBG Superstrate

A three-dimensional electromagnetic crystal is employed as a directivity-enhancing superstrate for planar antennas. The crystal is a woodpile made of alumina rods. In a shielded anechoic chamber, the performance of a patch antenna covered with the woodpile is measured. The superstrate is positioned at different distances from the antenna and its orientation is varied in the 8–12 GHz frequency range. The return loss, gain and radiation pattern in the Eand H-planes are measured. The electromagnetic behavior of Fabry-Perot cavities with woodpile mirrors, equivalent to the compound radiator, is also studied. The main effect of the crystal on the antenna performance is an enhancement of about 10 dB in maximum gain. A rather complete series of experiments is presented, highlighting the role of the periodic structure in the directivity enhancement and allowing a deeper understanding of the electromagnetic phenomena involved in EBG resonator antennas. Benefits and disadvantages of this kind of antennas are discussed and ideas for future research are given. Keywords—directivity enhancement, electromagnetic bandgap materials, Fabry-Perot cavities, periodic structures, woodpile.