The impact of shape and size of air cavity on extended hemispherical lens characterization for wireless applications at 61 GHz

In this article, a design of extended hemispherical lenses at 61 GHz with an air cavity is presented. Using air cavity above the primary feed in an extended hemispherical lens is a simple and low-cost solution to reduce size and minimize weight of lens without affecting the radiation characteristic and the input impedance of a radiating element which is located at the lens focus. We perform analysis of an extended hemispherical lens model with cavity by using a 3D field simulator and compare the effect of size and shape of the air cavity on the radiation characteristic of the lens. The lenses are manufactured using HDPE (High Density Polyethylene) material with a permittivity of ε_r = 2.3 for millimeter-wave radar applications at 61 GHz. The maximum directivity is about 30 dBi and the 3 dB-beam width is 3.5°. Two HDPE lenses with the diameter of 80 mm and 60 mm were fabricated and their measured characteristic was compared with simulation results.