Optical and modal features of hemielliptic dielectric lenses

TL;DR

This paper explores the optical and modal properties of hemielliptic dielectric lenses, emphasizing how resonant modes like HBT influence antenna performance and discussing methods to mitigate their effects.

Contribution

It provides a detailed analysis of the interplay between optical and modal features in hemielliptic lenses and offers strategies to reduce parasitic resonances affecting antenna efficiency.

Findings

HBT resonances significantly impact radiation characteristics.

Conventional techniques struggle to accurately describe resonant phenomena.

Recommendations are provided to minimize resonance effects.

Abstract

Any dielectric lens has a finite closed boundary and therefore is, in fact, an open dielectric resonator capable of supporting resonant modes whose Q-factor depends of the lens parameters (size, shape, and material). The hemielliptic lens, that is an essential building block of many mm-wave and THz antennas, is not an exception: it supports the so-called halfbowtie (HBT) resonances that can strongly affect performance of such antennas. In this paper we illustrate the interplay between the optical and modal features in the electromagnetic behaviour of hemielliptic lenses and highlight the drastic influence of the HBT resonances on radiation characteristics of lens antennas. We also discuss the difficulties associated with accurate description of the resonant phenomena in compact-size hemielliptic lenses with conventional techniques and provide recommendations on how to minimize the parasitic impact of HBT resonances on the antenna performance.