New materials and technologies applied to the design of antennas and microwave circuits in 5g systems

• Autores: Antonio Alex Amor
• Directores de la Tesis: Jose Manuel Fernandez Gonzalez (dir. tes.), Pablo Padilla de la Torre (codir. tes.)
• Lectura: En la Universidad Politécnica de Madrid ( España ) en 2021
• Idioma: español
• Tribunal Calificador de la Tesis: Jaime Esteban Marzo (presid.), Belén Galocha Iragüen (secret.), Guido Valerio (voc.), Raúl Rodríguez Berral (voc.), María García Vigueras (voc.)
• Programa de doctorado: Programa de Doctorado en Tecnologías y Sistemas de Comunicaciones por la Universidad Politécnica de Madrid
• Materias:
  • Física
    • Electromagnetismo
  • Ciencias tecnológicas
    • Tecnología electrónica
      • Antenas
      • Dispositivos de microondas
    • Tecnología de las telecomunicaciones
• Enlaces
  • Tesis en acceso abierto en: Archivo Digital UPM
• Resumen

  • This Doctoral Thesis is devoted to the study of new materials, technologies and techniques applied to the efficient design of antennas and microwave devices of future 5G wireless communication networks.

    First, we study the application of novel 2-D artificial materials, typically known as metasurfaces, for the manipulation and control of electromagnetic waves. We investigate the benefits of glide symmetry, a particular subset of higher symmetries that consists of a mirroring and translation operation, applied to the design of periodic holey metasurfaces. Glide symmetry is shown to increase the refractive index and reduce the frequency dispersion of a certain structure compared to its conventional counterpart. This is suitable for the design of low-loss, wideband antennas and guiding devices. Furthermore, we investigate the production of wideband anisotropy with elliptical holes arranged in a glide-symmetric configuration. This is desirable for some specific applications such as wave front transformation, cloaking and lens compression. As an example, we show that a wideband Maxwell fish-eye lens can be compressed with the use of glide-symmetric elliptical holes and proper transformation optics techniques.

    Secondly, we investigate the implementation of multilayered frequency selective surfaces (FSS) formed by subwavelength apertures. A FSS is any repetitive surface formed by subwavelength units engineered to conveniently scatter the incident electromagnetic waves. Traditional FSSs use a single metal layer embedded in a layered dielectric medium. However, new possibilities can be opened by stacking and misaligning several layers, such as the creation of negative-index structures, the existence of reflection and transmission bands and the increase of the operating bandwidth. A rigorous formulation based on the equivalent circuit analysis is derived for the efficient computation of 1-D and 2-D multilayered FSS with arbitrary apertures. This general-purpose formulation is more than 50 times faster than commercial simulators and works accurately under oblique incidence conditions. This is of potential interest for the efficient design of high-frequency wideband polarizers, filters, phase shifting elements, lightweight stirrers, and thin matching layers applied to 5G communication systems.

    Furthermore, controlling the radiation properties of antennas and microwave devices is one of the main technological challenges of future-generation 5G wireless networks. Tunable materials such as liquid crystal, graphene and ferroelectrics arise as an interesting option to provide electronic reconfigurability. In particular, liquid crystal is of the most promising tunable materials for low-loss operation in the microwave and millimeter-wave range, as specific commercial models are being developed. However, the analysis of liquid-crystal-based configurations is typically a complex task due to the anisotropic and lossy nature of the material. A series of methods are investigated to facilitate the analysis and design of reconfigurable RF devices based on the use of liquid crystal. These methods overcome the weaknesses of commercial eigenmode solvers when dealing with periodic structures embedded in anisotropic media, opening new possibilities.

    Finally, we show the potential interest of inkjet-printing techniques for the production of efficient, low-cost, RF antennas applied to wireless communication systems. Concretely, we brought the advantages of inkjet printing, such as the flexibility and lightweight of substrates, to the design of RF energy harvesters. Energy harvesting, defined as the process of collecting energy from ambient energy sources, is another technological challenge to increase the spectral efficiency of future 5G communication networks. This comes associated with the exponential increase over the past years in the number of RF transmitting sources, which have allowed RF energy harvesting to become a reliable power source for low-consumption electronic devices. As a proof of concept, we present the design, manufacturing and measurement of different inkjet-printed ultrawideband antennas and a complete RF energy harvesting system.