Radiation efficiency improvement of low profile antenna with metamaterial structure using LCP substrate with low profile copper foil

EBG (Electromagnetic BandGap) structures have lately attracted considerable attention both for the surface wave suppression and low profile antennas. To achieve low profile antennas by using an EBG structure for the antenna substrate, the thinner EBG substrate as well as the smaller gap to the antenna above the EBG substrate is important. Furthermore, a smaller EBG substrate area is required to accommodate the antenna into small wireless equipments. We have proposed a small metamaterial structure by analogy with a mushroom-like EBG structure, which enables a dipole antenna just above the structure to match with 50Ω as well as EBG structures.