Modeling and design of lenses combined with array antennas in the millimetre-wave regime
Time: Fri 2025-03-14 13.00
Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm
Video link: https://kth-se.zoom.us/w/68384894801
Language: English
Subject area: Electrical Engineering
Doctoral student: Pilar Castillo Tapia , Elektromagnetism och fusionsfysik
Opponent: Professor Ronan Sauleau, Institut d'Électronique et des Technologies du numéRique, Rennes, France
Supervisor: Professor Oscar Quevedo-Teruel, Elektromagnetism och fusionsfysik; Professor Martin Norgren, Elektromagnetism och fusionsfysik; Astrid Algaba-Brazalez, Universidad Politécnica de Cartagena, Cartagena, Spain
QC 20250212
Abstract
This thesis investigates the combination of array antennas with lenses to simplify the feeding networks of planar arrays in the millimeter-wave regime. Two different strategies are proposed: linear arrays of vertically stacked lenses based on parallel plate waveguide (PPW) and planar array antennas with dielectric lenses placed on top.
Due to their large electrical size, these antennas require efficient tools to design and simulate them. In this thesis, the farfield radiation pattern is calculated using two ray tracing models that use physical optics. Both models follow three steps: calculation of ray trajectories, calculation of amplitude distribution using the ray tube theory and evaluation of farfield radiation pattern. Furthermore, these models can also calculate the radiation efficiency. For PPW-based lenses, the efficiency decreases due to the conductivity and surface roughness of the metallic plates, whereas, for dielectric lenses, the efficiency decreases due to the material absorption and reflections.
Three PPW-based lens array antennas are presented in this thesis. First, the scanning in two planes is tested using a water drop lens array antenna and a feeding network based on a power divider and phase shifters. The antenna is manufactured in different pieces using milling. Then, a monolithic geodesic lens array antenna is designed and manufactured using additive manufacturing, which prevents leakage and misalignment between pieces. The profile of the geodesic lens requires some modifications to adapt to the manufacturing technique. Finally, a multiple-ridge lens antenna is proposed to further reduce the height profile of these antennas. Two different ridges are proposed (rectangular and trapezoidal), which are suitable for milling and additive manufacturing. This type of lens antennas can also be vertically stacked to form a linear array.
The combination of phased array antennas and dielectric lenses is of interest in the terrestrial and satellite communications industry. Dielectric lenses can increase the gain of the array in different scanning angles or redirect grating lobes. This can help to reduce the complexity and power consumption of array feeding networks. The two designed multilayer dielectric lenses show that using other curves to define the dielectric layers provide more degrees of freedom. This together with a customized design of the lens for the specific goal helps to achieve results close to the physical limits of the lens.