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A Class of Lightweight Spherical-Axicon Dielectric Lenses for High Gain Wideband Antennas

A class of lightweight spherical-axicon-like dielectric lenses suitable for enhancing broadband antennas performances is presented. The proposed lenses, sized according to a reference massive lens, are formed by thin dielectric sheets spaced equiangularly on the azimuth plane (petal-shaped lens), or regularly orthogonally arranged along the lens axis (disks-shaped lens), thus yielding construction simplicity and significant weight reduction. While petal-shaped dielectric lenses are shown to yield mild gain increase, lenses made by thin dielectric disks, orthogonally periodically arranged along the lens optical axis, offer performances much closer to those achieved by comparable massive refractive spherical-axicon dielectric lenses. The time-domain and the focusing characteristics of the proposed lenses are investigated. Then, a Floquet’s mode-based model is proposed to describe the stop-band characteristics of stacked-disk lenses, illustrating the mechanism underpinning their sudden performance degradation observed at the stop-band onset frequency. Full-wave analyses, based on a locally conformal finite integration technique (FIT), implemented in CST Studio Suite™ and validated by measurements or highly accurate FEM simulations, illustrate the excellent characteristics of the proposed lenses to operate with narrowband as well as ultra-wideband (UWB) waveforms.