Analysis and Design of Lens Antennas for Power-Constrained Applications

Abstract

The ever-increasing demand for faster data rates as well as overcrowding in the sub-6 GHz spectrum has driven the shift to using higher frequency bands. While the use of higher frequencies can facilitate bandwidth requirements needed to meet the required data rates, they struggle with high Free-Space Path Loss (FSPL) which require specialized solutions to overcome. Phased Array Antennas (PAAs) have attracted immense attention in recent years. PAAs are able to make use of a large quantity of antennas to produce a gain high enough to overcome FSPL while also benefiting from compactness and the ability to rapidly steer and shape the beam. While they have been shown to be effective solutions for many applications, most PAAs depend on a large number of active amplifiers, which entails higher upfront costs, high power consumption, and high thermal dissipation. Such challenges must be addressed for power-constrained or heat-sensitive applications.

This thesis presents a detailed analysis of existing solutions in literature and examines their trade-offs. The Lens Antenna Subarray (LAS) architecture is proposed as a solution, which offers low power consumption while keeping the Gain Over Noise Temperature (G/T) figure of merit for performance competitive with active arrays by leveraging both the directive properties of dielectric lenses as well as the flexibility of traditional PAAs. This thesis focuses on the design of a single lens and its feed network, referred to as a subarray.

To produce a practical example, a Satellite Communication (SATCOM) receiver is chosen as the target application, and a subarray is designed. An ultra-wideband lens with a novel permittivity profile is designed which can provide up to ±64° of -3 dB steering, an improvement over similar Printed Circuit Board (PCB) compatible designs which typically do not provide more than ±50° of steering. Additionally, feed antennas are designed to provide wideband operation over the SATCOM receiving frequency range of 17.7 to 21.2 GHz. A total of 19 antennas are arranged in a novel feeding arrangement which enables the use of circular polarization with the lens, which has not yet been shown in literature.

As the concept of LASs are relatively new to literature, there are many potential directions in which the concept can be developed. Further improvements to the lens, the simplification of feeding antennas, and array-level design are all areas which can be investigated in detail.