Cone-shape Fresnel zone lens of flat dielectric rings

Cone-shape Fresnel zone (FZ) lens of flat metal or dielectric rings is introduced. It is found that such a 229-GHz lens of three dielectric rings, focal length of 30mm, aperture diameter of 25mm and cone half-opening angle of 450 surpasses in focusing gain and space resolution the same in diameter and focal length plane-hyperbolic refraction lens. The new cone lens is by 2.2dB superior in gain and 45% in efficiency to the corresponding plane phase-reversal FZ lens. The lens can be easy manufactured at microwave and terahertz frequencies as a multilayer assembly of dielectric rings embedded in air or low-permittivity solid dielectric. It can be applied in microwave and terahertz focusing and imaging systems, and for a construction of light and effective FZ lens antennas.