Design Equation for Multidielectric Fresnel Zone Plate Lens

A structural design equation for multidielectric Fresnel zone plate (ZP) lens is outlined in this letter. Based on this equation, multidielectric ZP lenses/lens antennas are studied numerically in the 30-50 GHz microwave band and contrasted to an ordinary plano-convex lens/lens antenna. Usually, the ZP lens is made half-wavelength thick but we discovered that a similar wavelength thick lens can be built with lower-permittivity dielectrics, and that this lens can focus more efficiently. In a confined frequency band, the thin and light-weight multidielectric ZP lens of four or more dielectric rings per full-wavelength zone is comparable in focusing to the ordinary bulky lens.