Bandwidth, efficiency and directivity enhancement of printed antenna performance using planar circularly symmetric EBGs

Planar circularly symmetric (PCS) electromagnetic band-gap (EBG) substrates have been recently proposed to suppress the surface waves in printed technology (Llombart et al., 2004 and 2005). The major advantage of the PCS-EBGs with respect to structures based on vertical pins (de Maagt et al., 2003 and Sievenpiper et al., 1999) is the fabrication simplicity since the dielectric slabs do not need to be perforated. With respect to other planar type of EBG (Coccioli et al., 1999), an advantage is that the surface waves launched by a central source are reduced equally in all radial directions. The motivation of this contribution is to design and measure a prototype which demonstrates the suppression of surface waves by a PCS-EBG of a single antenna printed on a dielectric substrate. Thanks to the presence of the PCS-EBG around the antenna, we obtain an enhancement of the bandwidth, efficiency and directivity performances. The study will present some design considerations for the PCS-EBG itself, and then will proceed with the manufactured and measured antennas. The results explicitly show the advantages in terms of bandwidth and radiation pattern of the proposed EBG substrate. A bandwidth of 20% is achieved without significant surface wave losses.