Conformal Antennas and Arrays with Layers Consisting of Copper and Graphene-based Conductors for Redundancy Properties

Graphene is a new promising material with unique electrical, mechanical, optical and thermal characteristics. The use of graphene in the design of an antenna and other electromagnetic passive devices would be beneficial for miniaturization, efficient dynamic tuning, monolithic integration with graphene RF nano-electronics, and even transparency, mechanical flexibility, andreliability. However, there are some challenges to fabricate and design an antenna with pure graphene embedded in the layout. Here, an advanced study on the electrical and mechanical properties of the graphene-based conductive material (not pure graphene), and how this material can be utilized in developing a first-ever graphene-based conformal antenna array for wireless communication systems has been done. More specifically, the important factors for antenna design, such as electrical and mechanical properties, will be studied here to ensure an effective and efficient design. Next, a graphene-based antenna array on a planar surface will be designed to validate the electrical and mechanical properties, and finally, the trade-off of the graphene-based antenna array on a conformal surface is investigated. To mitigate the challenges of designing a graphene-based conformal antenna array, proper care is needed to achieve the optimal performance of the antenna array system. These new mechanisms of the graphene-based conformal antenna arrays will bring new possibilities in conformal antenna usage and wearable antenna applications for the first time

Reconfigurable Reflectarrays and Array Lenses for Dynamic Antenna Beam Control: A Review

Advances in reflectarrays and array lenses with electronic beam-forming capabilities are enabling a host of new possibilities for these high-performance, low-cost antenna architectures. This paper reviews enabling technologies and topologies of reconfigurable reflectarray and array lens designs, and surveys a range of experimental implementations and achievements that have been made in this area in recent years. The paper describes the fundamental design approaches employed in realizing reconfigurable designs, and explores advanced capabilities of these nascent architectures, such as multi-band operation, polarization manipulation, frequency agility, and amplification. Finally, the paper concludes by discussing future challenges and possibilities for these antennas.Comment: 16 pages, 12 figure

Design and Characterization of Modified Comb Patch Antennas

This work deals with the proposal of a novel type of microstrip antenna, called MCPA the modified comb patch antenna. The proposed antennas is composed of n parallel conductors, fed by a common microstrip. A dedicated mathematical framework, based on the multiconductors transmission line formalism, is proposed for antenna analysis and design. The analytical model is numerically validated with full-wave simulations, resulting in a 5% error in the predicted resonant patch length. A numerical study of antenna matching, size, radiation performance is carried out. The matching increases as the number of conductors increases, whilst gain of comb antennas made of n conductors are about half dB higher than the equivalent full patch counterpart. Then, an eighty conductors was realized and measured to assess the frequency response of the antenna, as well as its radiation performances. An error of 1% between the predicted and measured value resonance frequency was observed. A difference of about 0.67 dB was found for the measured maximum antenna gain, with respect to the simulated one. The proposed antenna design is appealing for printed electronics and wearable, on-textile applications

Metamaterial

In-depth analysis of the theory, properties and description of the most potential technological applications of metamaterials for the realization of novel devices such as subwavelength lenses, invisibility cloaks, dipole and reflector antennas, high frequency telecommunications, new designs of bandpass filters, absorbers and concentrators of EM waves etc. In order to create a new devices it is necessary to know the main electrodynamical characteristics of metamaterial structures on the basis of which the device is supposed to be created. The electromagnetic wave scattering surfaces built with metamaterials are primarily based on the ability of metamaterials to control the surrounded electromagnetic fields by varying their permeability and permittivity characteristics. The book covers some solutions for microwave wavelength scales as well as exploitation of nanoscale EM wavelength such as visible specter using recent advances of nanotechnology, for instance in the field of nanowires, nanopolymers, carbon nanotubes and graphene. Metamaterial is suitable for scholars from extremely large scientific domain and therefore given to engineers, scientists, graduates and other interested professionals from photonics to nanoscience and from material science to antenna engineering as a comprehensive reference on this artificial materials of tomorrow

Stretching the limits of dynamic range, shielding effectiveness, and multiband frequency response

In this dissertation, an RF MEMS variable capacitor suitable for applications requiring ultrawide capacitive tuning ranges is reported. The device uses an electrostatically tunable liquid dielectric interface to continuously vary the capacitance without the use of any moving parts. As compared to existing MEMS varactors in literature, this device has an extremely simple design that can be implemented using simple fabrication methods that do not necessitate the use of clean room equipment. In addition, this varactor is particularly suited for incorporating a wide range of liquid dielectric materials for specific tuning ratio requirements. Additionally, the shielding effectiveness performance of graphene-doped ABS thin films is investigated. The use of graphene as a replacement for metal fillers in composite EMI shielding materials is quickly becoming a widely-investigated field in the electromagnetic compatibility community. By replacing conventional metal-based shielding methods with graphene-doped polymers, low-weight, field-use temporary shielding enclosures can be implemented that do not suffer from mechanical unreliability and corrosion/oxidation like a traditional metal enclosure. While the performance of composite EMI shielding materials has not yet surpassed metals, the advantages of polymer-based shielding methods could find usage in a variety of applications. Finally, mutliband pre-fractal antennas fabricated via 3D printing are reported. These devices are the first to incorporate the advantages of 3D printing (rapid prototyping, fabrication of complex geometries otherwise unobtainable) with the advantages of self-similar antennas (increased gain and multiband performance) in a single device. The Sierpinski tetrahedron-based antenna design was both computationally modeled and physically realized to illustrate its potential as a solution to enable true multiband communication platforms

Antenna Designs for 5G/IoT and Space Applications

This book is intended to shed some light on recent advances in antenna design for these new emerging applications and identify further research areas in this exciting field of communications technologies. Considering the specificity of the operational environment, e.g., huge distance, moving support (satellite), huge temperature drift, small dimension with respect to the distance, etc, antennas, are the fundamental device allowing to maintain a constant interoperability between ground station and satellite, or different satellites. High gain, stable (in temperature, and time) performances, long lifecycle are some of the requirements that necessitates special attention with respect to standard designs. The chapters of this book discuss various aspects of the above-mentioned list presenting the view of the authors. Some of the contributors are working strictly in the field (space), so they have a very targeted view on the subjects, while others with a more academic background, proposes futuristic solutions. We hope that interested reader, will find a fertile source of information, that combined with their interest/background will allow efficiently exploiting the combination of these two perspectives

Design of new radiating systems and phase shifters for 5G communications at millimeter-wave frequencies

With the arrival of the new generation of communications, known as 5G, the systems that constitute it must offer better performance in terms of data speed, latency and connection density than the previous generation of communications. For 5G, an allocation of the frequency ranges that will support future wireless communications has been established. This allocation is formed by a range of frequencies corresponding to bands below 6 GHz and the other range of frequencies includes bands above 24 GHz. In the latter frequency range, which includes part of the millimeter-wave frequency band (from 30 GHz to 300 GHz), the development of new radio frequency (RF) components is necessary because their design and manufacture is a technological challenge. As the frequency that supports wireless communications increases, propagation losses also increase. Therefore, these losses must be compensated by the radiating systems in 5G to make these communications possible. The RF devices that make up these new systems must provide high antenna gain, be power efficient and offer spatial reconfigurability of the radiated signal. In this thesis, the main objective is the design of both guided and radiating RF devices to provide design solutions for future 5G systems at millimeter-wave frequencies. In particular, the contributions made have been to the design of phase shifters and antenna arrays. To improve efficiency at millimeter-wave frequencies, these devices have been designed in waveguide technology. Phase shifters are essential RF devices to control the phase shift of the electromagnetic wave that will be radiated to a certain spatial direction by an antenna array. The design of beamforming networks requires the implementation of phase shifters that produce a fixed or variable phase shift value. However, the design and fabrication of these devices at millimeter-wave frequencies is a complex task. In this thesis, four designs of waveguide phase shifters that produce both fixed and variable phase shift are presented. For phase shifters that provide a fixed phase shift, the value of this phase shift along the frequency is tuned in a desired manner by using periodic structures with higher symmetries. These types of configurations provide both flexibility in the design process and improved electromagnetic performance such as greater operating bandwidth. All the phase shifters have been implemented in gap-waveguide technology to demonstrate its effectiveness in these devices for millimeter-wave frequencies. Regarding the radiating systems, two feeding strategies have been considered in the design process. First, the design of a 70 GHz centered antenna array implemented in gap-waveguide technology combined with the use of separate waveguides in E-plane is proposed. In this design, the feed is guided through a waveguide corporate-feed network. Second, the design of a reflectarray whose unit cells are formed using three-dimensional geometries is presented. In this case, the feeding is done in free space by radiation from a source antenna. In the previous designs, the fabrication of the prototypes was done by 3D printing based on stereolithography. Finally, using unit cells with three-dimensional geometries, the design of radiating devices with more complex functionalities such as reflection/transmission with high directivity and reconfiguration of the reflected radiation by means of graphene structures are proposed.Con la llegada de la nueva generación de comunicaciones, denominada 5G, los sistemas que la conforman deben ofrecer unas mejores prestaciones en términos de velocidad de datos, latencia y densidad de conexiones respecto a la generación de comunicaciones anterior. Para 5G se ha establecido una asignación de los rangos de frecuencia que van a soportar las futuras comunicaciones inalámbricas. Esta asignación se compone por un rango de frecuencias correspondiente a las bandas por debajo de los 6 GHz y el otro rango de frecuencias engloba a las bandas por encima de los 24 GHz. En este ´ultimo rango de frecuencias, en el cual están incluidas parte de la banda de las frecuencias milimétricas (desde 30 GHz a 300 GHz), es necesario el desarrollo de nuevos componentes de radiofrecuencia (RF) ya que su diseño y fabricación supone un reto tecnológico. Al aumentar la frecuencia que soporta las comunicaciones inalámbricas, las pérdidas por propagación también aumentan. Es por ello por lo que estas pérdidas deben ser compensadas por los sistemas radiantes en 5G para que las comunicaciones sean posibles. Los dispositivos de RF que componen estos nuevos sistemas deben proporcionar una alta ganancia de antena, ser eficientes en términos de potencia y ofrecer reconfigurabilidad espacial de la señal radiada. En esta tesis, el objetivo principal es el diseño de dispositivos de RF tanto guiados como radiantes para ofrecer soluciones de diseño a los futuros sistemas 5G en frecuencias milimétricas. De manera particular, las contribuciones realizadas han sido al diseño de desfasadores y agrupaciones de antenas. Para mejorar la eficiencia en frecuencias milimétricas, estos dispositivos han sido diseñados en tecnología en guía de ondas. Los desfasadores son dispositivos RF esenciales para controlar el desfase de la onda electromagnética que será radiada hacia una cierta dirección espacial por una agrupación de antenas. Las redes de beamforming tienen la necesidad de implementar en su diseño desfasadores que producen un valor de desfase fijo o variable. Sin embargo, el diseño y fabricación de estos dispositivos en frecuencias milimétricas resulta una tarea de alta dificultad. En esta tesis se presenta cuatro diseños de desfasadores en guía de onda que producen un desfase tanto fijo como variable. Para los desfasadores que proporcionan un desfase fijo, el valor de este desfase a lo largo de la frecuencia es ajustado de manera deseada mediante el uso de estructuras periódicas con simetrías superiores. Este tipo de configuraciones proporcionan tanto flexibilidad en el proceso de diseño como una mejora de las características electromagnéticas como puede ser un mayor ancho de banda de operación. Todos los desfasadores realizados han sido implementados en tecnología gap waveguide para demostrar su efectividad en estos dispositivos para frecuencias milimétricas. Respecto a los sistemas radiantes, se han considerado dos estrategias de alimentación en el proceso diseño. En primer lugar, se propone el diseño de un array centrado a 70 GHz implementado en tecnología gap waveguide combinado con el uso de guías de onda separadas en plano E. En este diseño, la alimentación es guiada a través de una red de alimentación corporativa en guía de onda. En segundo lugar, se presenta el diseño de un reflectarray cuyas celdas unitarias son formadas mediante geometrías tridimensionales. En este caso, la alimentación se hace en el espacio libre mediante la radiación de una antena fuente. En los anteriores diseños, la fabricación de los prototipos se realizó mediante impresión 3D basado en estereolitografía. Finalmente, a través del uso de celdas unitarias con geometrías tridimensionales, se proponen el diseño de dispositivos radiantes con funcionalidades más complejas como la reflexión/transmisión con alta directividad y la reconfiguración de la radiación reflejada mediante estructuras con grafeno.Tesis Univ. Granada