Shadow blockage improvement using a perforated dielectric Fresnel lens

Shadow blockage can lead to a significant reduction in the efficiency of grooved dielectric Fresnel lenses, especially for small values of F/D. This paper presents a multi-dielectric Fresnel lens which does not suffer from the effects of shadow blockage The lens is fabricated from a single dielectric sheet where perforations in the material are used to obtain the required dielectric constants. Measurements carried out at 30.5 GHz show nearly 1 dB gain improvement of the perforated dielectric Fresnel lens over a corresponding grooved lens.