This paper presents a new low-profile metallic lens antenna formed by twelve metallic rings distributed in a single layer and arranged along a ring, as illustrated in Figure 1.
To do so, the metallic lens is illuminated by a plane wave using the full-wave electromagnetic tool CST .
An open-ended waveguide with a resonant ring is used as the primary feed for the metallic lens. The resulting structure improves the maximum directivity with respect to the feeder along a large bandwidth (more than 5 dB) and provides a good crosspolar level (better than -35 dB).
Engheta, "e-nearzero graded index structure as a bi-concave metallic lens
using stacked rectangular near cutoff waveguides," 7th European Conference on Antennas and Propagation (EuCAP), 2535-2537, Gothenburg, Sweden, Apr.
Navarro-Cia, "Ultra-compact planoconcave zoned metallic lens based on the fishnet metamaterial," Applied Physics Letters, vol.
Navarro-Cia, "Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens," Optics Express, vol.
In these early stages metallic lens
antennas such as metal-lens antennas and wire-grid lens antennas , reflector lens antennas , spherical antennas , dual lens antennas , as well as dielectric lens antennas , and substrate lens antennas  were successfully investigated.