High directivity multiple superstrate antennas with improved bandwidth

Gain enhancement methods for antennas have been proposed and investigated using multiple superstrates over a printed antenna (see Jackson, D.R. and Alexopoulos, N.G., 1985; Yang, H.Y. and Alexopoulos, 1987; Alexopoulos and Jackson, 1984; Shen, X.H. et al., 2000). These antennas present a high directivity at the design frequency, but a very small bandwidth. We investigate different arrangements of the superstrates in order to increase the directivity bandwidth. Superstrates consist of layers disposed over a ground plane. The even layers are made of high permeability media and the odd ones of high permittivity media. We consider structures constituted exclusively of dielectric materials, to avoid expensive magnetic materials.