Enhanced antenna performances using planar circularly symmetric EBGs

Planar circularly symmetric (PCS) electromagnetic band-gap (EBG) substrates have recently been proposed to suppress surface waves (Llombart, N. et al., 2004). The application of PCS-EBG to reduce the surface waves excited by an antenna printed on a dielectric slab is discussed. The study starts from a reference microstrip-excited, slot-coupled dipole that presents a relatively large bandwidth (about 12%) and relatively low efficiency (about 40%-60%) due to surface wave losses. Some design considerations on how to enhance the performance of this antenna by surrounding it with a PCS-EBG are then presented. Finally the measured results are presented. These explicitly show the advantages of the proposed EBG substrate in terms of bandwidth and radiation pattern. A bandwidth of 20% is achieved without significant surface wave losses. The results also show radical improvements in the isolation between antennas printed on the same substrate.