New types of Fresnel zone plate lens with lower backward radiation

Owing to its low cost, light weight, and easy fabrication, the Fresnel zone plate (FZP) antenna is becoming an important candidate for such applications as DBS reception and mobile communication. Compared with the FZP reflector, the FZP lens has no feed blockage, so it is more attractive to study. The printed FZP lens, in which the concentric zones are alternatively transparent and opaque, is discussed in this paper. However, the single-layer FZP has a rather low efficiency, for about half of the incident energy is reflected backward, so the double-layer FZP lens had been proposed to enhance the aperture efficiency. By using an improved full-wave analysis the double-layer FZP lens is studied.