Enhancement of Millimeter-Band Transceivers with Gap Waveguide Technology

Abstract

It is known to all that year after year in modern society there is an urgent demand to consume wirelessly, and even stream ever larger multimedia content. High-frequency technologies have made it possible to go from transmitting analog voice and SMS text messages, to now transmitting live video in 4K quality from a mid-range smartphone. The way to measure these advances is by the bandwidth (Mb/s) reserved for each network user and the cost required to achieve it. To achieve even higher bandwidths, it is essential to improve signal coding techniques or increase the frequency of the signal, for example: to the mmWave bands (25GHz - 100 GHz), where these high-frequency techniques come into play. However, there is a frequency limit where current planar technology materials - such as the printed circuit boards used to build RF devices - are so lossy that they are not suitable at these mmWave frequencies. Current commercial solutions consist of guiding the electromagnetic energy with hollow metallic waveguides, but they suffer from the problem that as the frequency increases the diameter of these waveguides gets smaller and smaller, so manufacturing tolerances increase exorbitantly. Not to mention that they are usually manufactured in two parts, one upper and one lower, whose joints are not always perfect and produce energy losses. With these issues in mind, in 2009 the theory and basic science of a new electromagnetic energy guidance technology called Gap Waveguide was proposed, which is based on the use of metasurfaces constructed with periodic elements similar to a bed of nails. There are several implementations of this technology, but the three main ones are: Ridge, Groove and Inverted Microstrip Gap Waveguide. The latter is the most compatible with conventional planar manufacturing technologies and therefore the most cost-effective, although it also has drawbacks mainly in terms of losses when compared to the other versions. This thesis aims to deepen the study of the Inverted Microstrip guidance technology, its limitations and to develop with it some of the needed components in RF systems such as filters, diplexers, amplifiers, antennas, etc. Regarding the methodology for this thesis, a commercial simulation software for the analysis of antennas and components, CST Microwave Studio [1], has been used. AWR Microwave Office [2], a circuit simulator, has also been used to complement the simulations. On the other hand, there is a laboratory for the manufacture of prototypes in printed technology (with some limitations in terms of resolution) and the corresponding measurement laboratory, which includes network analyzers up to 40 GHz, spectrum analyzers and an anechoic chamber.