A plate Luneberg lens with the permittivity distribution controlled by hole density

The Luneberg lens enables easy beam scanning and has the possibility of multibeam forming. In order to apply these characteristics to a planar antenna, it is first necessary to discuss a method of fabrication for a thin-plate Luneberg lens. On the other hand, there is a method of controlling permittivity whereby many holes having diameters sufficiently smaller than the wavelength are created in the di-electric material. Permittivity control by the hole density has been used as a method of adjusting the permittivity over a wide range in order to realize a matching layer for the lens, by creating many holes in the direction perpendicular to the incident electric field or close to this direction. In contrast, the authors propose a method for adjusting the permittivity over a wide range by creating multiple holes parallel to the electric field. By means of the hole density method, a Luneberg lens is fabricated. The operating characteristics are determined at 10 and 48 GHz. It is confirmed that the structure works well as a Luneberg lens at both frequencies. Further, as an example of the applications of the plate Luneberg lens, a parallel plate slot array antenna is fabricated and its radiation characteristics are measured. It is found that the Luneberg lens can be applied as the feed section of a high-gain millimeter-wave planar antenna with a beam scanning capability. (C) 2002 Wiley Periodicals, Inc.