Layered lens antennas

Reflectors are the most commonly used antennas in high-gain applications. Although very efficient radiators, they require highly accurate curved reflecting surfaces that are often cumbersome to implement. Consequently, alternatives have been investigated. Space-fed arrays are particularly relevant to this work. As in a reflector, these structures transform a spherical wave emanating from a feed into a collimated beam (plane wave), with the advantage that the space-fed array surface can have almost any shape, including a plane. However, since reflection-type space-fed arrays (e.g., reflectarrays) require the same surface accuracy as a reflector, a transmission type space-fed array (e.g., a layered lens antenna) is often a more desirable alternative. A preliminary design procedure, theoretical analysis and an 8.421 GHz layered lens prototype are presented. The theoretical analysis is based on a full-wave treatment of plane wave transmission through a uniform infinite array of elements. The prototype lens was designed for maximum gain and minimum number of layers (three). Although the presented material is preliminary, it clearly indicates that layered lenses are good candidates for high-gain antennas.