Reduced-Size Lenses for Flat-Top Pattern Antennas

Dielectric lens antennas are quasi-optical devices well suited for shaped-beam applications at millimetre waves. In this paper, we present a powerful computer-aided design (CAD) tool for the analysis and optimization of multi-shell integrated lens antennas (ILAs) of arbitrary 3-D shape. The optimization technique is based on a binary genetic algorithm (GA) coupled to the hybrid geometrical optics - physical optics (GO-PO) method implemented to analyze the performance of each individual of the GA population. This methodology has been applied to design three reduced-size ILAs radiating flat-top beams. Firstly, it is shown that the radiation patterns of lenses in Rexolite exhibit significant and frequency-selective ripples. To circumvent this limitation, a double-shell ILA is designed. This configuration enables one to reduce the undesirable effects of multiple internal reflections while ensuring a moderate size for the lens. The influence of manufacturing uncertainties is also analyzed.