Low-profile planar lens with multilevel FSS for directivity enhancement

An array of apertures or horn antennas are commonly used to obtain high directivity and gain, at the expense of increasing the fabrication complexity. In this paper a new approach is presented based on the use of frequency selective surfaces (FSS). These structures are commonly used to improve the performance of planar antennas within a certain frequency band. This paper shows how a FSS can be also used as a planar lens to increase the directivity of a single open waveguide keeping the low-profile and the ease of manufacturing of this kind of apertures. The proposed FSS is a multilevel metallic hole array (MHA) working at 8 GHz. Results show an increment of the maximum gain of 8 dBi with regard to a single open waveguide, with a small increment of the antenna's height.