Systematic design of antennas using the theory of characteristic modes

El principal objetivo de esta tesis es demostrar que la Teoría de los Modos Característicos puede ser empleada de forma sistemática para diseñar antenas de hilo y antena planas. La gran ventaja de los modos característicos, frente a otros métodos de diseño, es la clara visión física que proporcionan de los fenómenos que contribuyen a la radiación de la antena. A través de numerosos ejemplos se demostrará como los modos característicos permiten comprender mejor el funcionamiento de una antena, de forma que el diseño de la misma se puede realizar de forma justificada y coherente. También se mostrará como la información proporcionada por los modos característicos puede ser aprovechada para seleccionar la forma más apropiada para el elemento radiante, al igual que para elegir una configuración de alimentación óptima que maximice el ancho de banda de impedancia. La Teoría de los Modos Característicos fue inicialmente formulada por Garbacz en 1968, y posteriormente refinada por Harrington y Mautz en 1971. Tradicionalmente, los modos característicos han sido empleados para sintetizar formas de antena, y para controlar la difracción de objetos mediante carga reactiva. Sin embargo, en la actualidad, la Teoría de los Modos Característicos ha caído prácticamente en el olvido, a pesar de que permite obtener una solución modal para la corriente, que es de gran utilidad a la hora de analizar problemas de análisis, síntesis y optimización de antenas y difractores. La Teoría de los Modos Característicos parte de la definición de un problema de autovalores que involucra la matriz de impedancia generalizada de la estructura, y que tras ser resuelto proporciona un conjunto de modos de corriente reales, que son los denominados modos característicos. Estos modos se corresponden con las resonancias naturales de la estructura y pueden ser obtenidos numéricamente para cuerpos conductores de forma arbitraria. Por otra parte, los modos característicos forman un conjunto de funciones cerCabedo Fabrés, M. (2007). Systematic design of antennas using the theory of characteristic modes [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1883Palanci

Evaluación de competencias transversales en la asignatura Proyecto

[ES] La asignatura Proyecto, ubicada en el 10º cuatrimestre de los estudios de Ingeniería de Telecomunicación de la Universidad Politècnica de València (UPV), nació en el curso 2012- 2013 a raíz de los requerimientos impuestos por la entidad de acreditación ABET (Accreditation Board for Engineering and Technology) [1]. Con esta asignatura se busca trabajar una serie de competencias transversales definidas por ABET que todo Ingeniero de Telecomunicación debe poseer al término de sus estudios.Cabedo Fabres, M.; Carceller Candau, C.; Reig, J. (2014). Evaluación de competencias transversales en la asignatura Proyecto. En JIDTEL 2014 - Jornadas de Innovación Docente 2014 - En homenaje a Elvira Bonet. Editorial Universitat Politècnica de Valencia. 1-12. http://hdl.handle.net/10251/5488911

Análisis de los resultados del Curso Transversal de Doctorado “Carrera Investigadora”, en formato online

[EN] The Communication objectives are to present the results of the implementation of the Massive Online Course of the Doctoral School of UPV called " Research Career” considerig the planning, development and results. It is a 2 ECT course, taught from year 2014 (3 editions). The course has been designed using the tools provided by the UPV, especially PoliformaT and Polimedia. It has involved an important task of planning and preparation of contents. The course is structured in 7 teaching units, each unit has 5 Polimedia, supplementary material and a multiple-choice test. The delivery rate has been of one unit per week. There have been self-assessments of each unit, a discussion forum, work and a final exam. The results of the evaluation and follow-up surveys give good indicators. This is a new experience for an official doctoral level course with online methodologies. Three year of experience with 91, 110 and 201 students could serve as a real case and implement a model for other courses and Masters degree with similar methodologies.[ES] Los Objetivos de la comunicación son presentar los resultados obtenidos enla puesta en marcha del Curso Online de la Escuela de Doctorado de la UPVdenominado "Carrera Investigadora", desde el punto de vista deplanificación, desarrollo y resultados.Se trata de un curso de 2 créditos ECTS, impartido desde el año 2014 (3 ediciones). El curso se ha realizado utilizando las herramientas facilitadaspor la UPV, especialmente PoliformaT y Polimedia. Ha supuesto una tareaimportante de planificación y preparación del material.El curso está estructurado en 7 unidades didácticas, cada unidad cuenta con5 videos en formato polimedia, material complementario de consulta y unexamen. El ritmo de impartición ha sido de una unidad por semana.Se han realizado autoevaluaciones de cada unidad, un foro de debate,trabajo y examen final. Los resultados de la evaluación y las encuestasindican un alto seguimiento del curso.Se trata de un experiencia innovadora para un curso oficial de nivel dedoctorado con metodologías online. Tres años de experiencia con 90 , 110 y201 estudiantes permiten establecer criterios para diseñar otros cursos denivel de Máster con metodologías similares.Ferrando Bataller, M.; Cabedo Fabrés, M.; Antonino Daviu, E. (2016). Análisis de los resultados del Curso Transversal de Doctorado “Carrera Investigadora”, en formato online. En In-Red 2016. II Congreso nacional de innovación educativa y docencia en red. Editorial Universitat Politècnica de València. https://doi.org/10.4995/INRED2016.2016.4360OC

Periodic Leaky-Wave Antenna on Planar Goubau Line at Millimeter-Wave Frequencies

A periodic leaky-wave antenna on a planar Goubau line is presented. This transmission line is formed by a planar single-wire waveguide on a thin dielectric substrate. Leakage is produced by adding dipoles along the line on the bottom face of the substrate. A coplanar waveguide is used to feed the antenna, which acts as a smooth transition between the input coaxial cable and the planar Goubau line. The advantage of using this line lies on its losses, lower than those of typical microstrip lines due to the absence of a ground plane. As a result, a higher radiation efficiency than in microstrip-fed antennas can be obtained while keeping similar advantages, e.g., low profile or low production cost. A prototype of the antenna at 40 GHz has been fabricated. Measurements of this prototype are presented in this letter.This work was supported by the Spanish Ministry of Education and Science (Ministerio de Educacion y Ciencia) under Projects TEC2010-20841-C04-01 and CSD2008-00068.Sánchez Escuderos, D.; Ferrando Bataller, M.; Herranz Herruzo, JI.; Cabedo Fabrés, M. (2013). Periodic Leaky-Wave Antenna on Planar Goubau Line at Millimeter-Wave Frequencies. IEEE Antennas and Wireless Propagation Letters. 12:1006-1009. https://doi.org/10.1109/LAWP.2013.2278035S100610091

Modal pattern stability factor as a figure of merit for characteristic modes

This paper is a postprint of a paper submitted to and accepted for publication in Electronics Letters and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.This Letter proposes the use of a modal pattern stability factor (MPSF) parameter to quantify the pattern stability associated to characteristic modes (CM). The proposed parameter can be used as a figure of merit for CM associated to arbitrary-shaped structures, aiding the antenna design process. This parameter can be used (together with other modal parameters) to optimise the geometry of a radiating element in order to improve the radiation pattern stability in a desired range of frequencies. Two examples are presented for analysis. First, MPSF for the CM of three ring antennas with different width are analysed, showing how pattern stability of CM depend on this geometrical parameter. Secondly, three metallic plates with different shapes are analysed in terms of MPSF, in order to assess the stability of the CM for each geometry.This work was supported by the Spanish Ministry of Economics and Competitiveness under project TEC2013-47360-C3-3-P, and by Generalitat Valenciana under project GV/2015/065.Antonino Daviu, E.; Mohamed Mohamed-Hicho, N.; Cabedo Fabrés, M.; Ferrando Bataller, M. (2016). Modal pattern stability factor as a figure of merit for characteristic modes. Electronics Letters. 52(20):1658-1659. https://doi.org/10.1049/el.2016.1926S16581659522

Segmented video notes as reference and study material in Telecommunications Engineering courses

[EN] The pandemic has accelerated the adoption by many Higher Education institutions of online teaching and class recording. Despite the controversy about the appropriateness of recording classes, recent research has shown that students are willing to receive training through recorded classes, since they meet their learning expectations. In addition, the recordings can serve as an equivalent replacement for class attendance without the need to travel and the requirement to receive classes at a specific time. Although the recordings are made available as student reference material, their length and lack of labeling make it difficult to find a specific piece of content to review. The Universitat Politècnica de València has an automatic class recording system called Videoapuntes, which allows the teacher to schedule the unattended recording of his or her class in two videos, one with him or her explaining on the blackboard and the other with the output on the screen. from the classroom computer. In this innovation we propose the segmentation of video notes and their consolidation as an integrated tool in the PoliformaT online education platform to promote the autonomous study of students. The results, more than 40,000 views during a course for FSD and between 3,500 and 6,000 views for other subjects, which represent increases of at least an order of magnitude compared to the accesses of the uncut video notes of previous years, reflect a significant use of these resources by students in the subjects in which it has been implemented.[ES] La pandemia ha acelerado el proceso de adopción de enseñanza en línea y grabación de clases en muchas instituciones de educación superior. A pesar de la controversia sobre la idoneidad de grabar las clases, la investigación reciente ha demostrado que los estudiantes están dispuestos a recibir formación mediante clases grabadas, ya que cumplen con sus expectativas de aprendizaje. Además, las grabaciones pueden servir como un reemplazo equivalente para la asistencia a clase sin la necesidad de desplazamiento y requisito de recibir las clases en un horario concreto. Aunque las grabaciones quedan disponibles como material de consulta para los alumnos, su duración y falta de etiquetado hace que sea difícil encontrar una parte específica del contenido que los estudiantes desean consultar, lo que provoca una infrautilización de este recurso para repasar. La Universitat Politècnica de València cuenta con un sistema automático de grabación de clases denominado Videoapuntes, que permite al profesor programar la grabación de forma desatendida de su clase en dos vídeos, uno con él o ella explicando en la pizarra y otro con la salida de pantalla del ordenador de clase. En esta innovación planteamos la segmentación de los videoapuntes y su consolidación como herramienta integrada en la plataforma de educación online PoliformaT para potenciar el estudio autónomo de los y las estudiantes. Para evaluar el impacto de la intervención, comparamos los accesos a la consulta de videoapuntes sin segmentar y segmentados en tres asignaturas obligatorias del Grado en Ingeniería de Tecnologías y Sistemas de Telecomunicación durante dos cursos. Se observan incrementos de, al menos, un orden de magnitud frente a los accesos de los videoapuntes sin cortar de años anteriores (de 3.600 a 40.000, de 600 a 4.000 y de 33 a 3.500), reflejando un uso significativo de estos recursos por parte de los estudiantes en las asignaturas en las que ha sido implementado.Despujol Zabala, I.; Martínez Millana, A.; Cabedo Fabrés, M. (2023). Vídeoapuntes segmentados como material de consulta y estudio en asignaturas de Ingeniería de Telecomunicación. Editorial Universitat Politècnica de València. 1480-1489. https://doi.org/10.4995/INRED2023.2023.168551480148

A novel low-profile high-gain UHF antenna using high-impedance surfaces

A novel wideband low-profile planar antenna design based on the use of a high-impedance surface (HIS) is presented for digital television (DTV) reception in the UHF band. The proposed design is based on a wideband monopole antenna in close proximity to an artificial ground plane, composed of an array of square metal loops at the top, an air gap and a ground plane at the bottom, without grounded vias. Low-cost substrates are employed in the design: rigid PVC for the antenna and foamed PVC for the artificial ground plane. The advantages of the proposed design for DTV applications are high gain, low profile, light weight, low cost and large bandwidth. Details of the proposed antenna design are described, and measurements together with a comparison to a conventional antenna with PEC ground plane are presented.This work was supported by the Spanish Ministry of Science and Innovation under Projects TEC2010-20841-C04-01, TEC2013-47360-C3-3-P, and CSD2008-00068.Mohamed Mohamed-Hicho, N.; Antonino Daviu, E.; Cabedo Fabres, M.; Ferrando Bataller, M. (2015). A novel low-profile high-gain UHF antenna using high-impedance surfaces. IEEE Antennas and Wireless Propagation Letters. 14:1014-1017. doi:10.1109/LAWP.2015.2389274S101410171

Design Guidelines for the Excitation of Characteristic Modes in Slotted Planar Structures

This paper provides some design guidelines for the excitation of broadband slotted planar antennas, addressing key issues such as coupling, symmetries and multiple feeding. The theory of characteristic modes (CMs) is used to identify the collection of current modes that exists on these structures, dealing to a valuable understanding of the radiating mechanisms and allowing a more controlled design process. Modal analysis of a circular aperture cut on a finite square ground plane is presented in order to demonstrate that an optimum choice of the feeding mechanism can be made according to the current distribution of the desired modes. Based on the information yielded by this modal analysis, a capacitive-coupled dual-feed circular aperture antenna is presented. This antenna takes advantage of the symmetries of the characteristic currents by making use of multiple feeding, in order to excite only some particular modes. Usage of commonly-fed and differentially-fed configurations enables an increased control of the excitation of modes in the structure. CM analysis of the antenna including the feeding structures is presented, showing the influence of the feeding lines in the performance of this type of antennas. A prototype of the antenna has been fabricated and measured. Simulated and measured results are presented, being in good agreement.This work was supported by the Spanish Ministry of Economy and Competitiveness under Project TEC2016-78028-C3-3-P and Project GV/2015/065.Antonino Daviu, E.; Cabedo Fabres, M.; Sonkki, M.; Mohamed Mohamed-Hicho, N.; Ferrando Bataller, M. (2016). Design Guidelines for the Excitation of Characteristic Modes in Slotted Planar Structures. IEEE Transactions on Antennas and Propagation. 64(12):5020-5029. doi:10.1109/TAP.2016.2618478S50205029641

Microwave Planar Lens Antenna Designed with a Three-Layer Frequency Selective Surface

[EN] A multilevel Frequency Selective Surface (FSS) formed by a non-uniform distribution of circular holes on a metallic sheet is presented. The FSS is aimed at working as a planar lens to increase the gain of the feeding aperture. The unit cell of the FSS acts as a high-pass filter that provides the necessary phase shift to focus the beam on the far-field region. The phase shift is synthesized by suitably configuring the size and position of each unit cell in the FSS. The planar lens is placed next to the feeding aperture to confer the structure a low-profile shape. A prototype has been designed, fabricated and measured. Results show an increment of 7.32 dB in the gain compared to the feeding aperture within a 7.33% bandwidth around 20.45 GHz, and a side-lobe level below 􀀀12 dB, with an aperture efficiency of 65% and a radiation efficiency above 90%.This work was supported in part by the Spanish Ministry of Economics and competitiveness under Project TEC2013-47360-C3-3-P and in part by Generalitat Valenciana under Project GV/2015/065.Sánchez-Escuderos, D.; Moy-Li, HC.; Antonino Daviu, E.; Cabedo Fabrés, M.; Ferrando Bataller, M. (2017). Microwave Planar Lens Antenna Designed with a Three-Layer Frequency Selective Surface. IEEE Antennas and Wireless Propagation Letters. 16:904-907. https://doi.org/10.1109/LAWP.2016.2614342S9049071

Wideband double monopole for mobile, WLAN and C2C services in vehicular applications

[EN] In this letter, a three-dimensional antenna solution for automotive applications is presented. The proposed solution is formed by two independent antennas, perpendicularly placed inside a plastic cover with a shark-fin shape. The antennas, designed with low-cost materials, exhibit omnidirectional radiation patterns in the azimuthal plane. The first antenna is a doubleshorted monopole that provides service from 698 to 960 MHz (in the LTE700, GSM850, and GSM900 bands), whereas the second antenna is a drop-shaped monopole that operates from 1.7 to 2.7 GHz (in the DCS1800, PCS1900, WCDMA2100, WLAN2400, LTE2600, WiMAX2350, and Wi-Fi at 2.4-GHz bands), and from 5.1 to 6 GHz (in theWi-Fi at 5 GHz and C2C bands). Results show a good matching and radiation efficiency at all bands.This work was supported by Project SEESAW P.O.R. 2007-2013-bando 2009-Azione 1.1.2, the Spanish Ministry of Economics and competitiveness under Projects TEC2013-47360-C3-3-P and CSD2008-00068, and the Government of Ecuador under the SENESCYT.Navarro-Méndez, DV.; Carrera-Suárez, LF.; Sánchez-Escuderos, D.; Cabedo Fabrés, M.; Baquero Escudero, M.; Gallo, M.; Zarnberlan, D. (2017). Wideband double monopole for mobile, WLAN and C2C services in vehicular applications. IEEE Antennas and Wireless Propagation Letters. 16:16-19. https://doi.org/10.1109/LAWP.2016.2552398S16191