Publication: Diseño de antenas de ranura de doble banda en tecnología inverted microstrip gap waveguide de bajo coste
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2015
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2015-07-07
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Abstract
En este TFG presentaremos un ejemplo sobre el uso de la tecnología gap waveguide, cuya principal ventaja es que presenta bajas pérdidas. Concretamente, presentaremos el diseño, simulación y construcción de una antena de ranura de doble banda realizada en esta tecnología, la cual no necesita el contacto entre los componentes, proporciona encapsulado de los circuitos y evita acoplos mutuos y radiaciones indeseadas.
La antena que se presenta a lo largo de este proyecto es de tipo ranura y estaría alimentada por una línea microstrip. En general este tipo de antenas producen radiación trasera, por lo que será necesario combinar la antena de doble banda con una estructura que simule el comportamiento de un Perfect Magnetic Conductor (PMC) con ello conseguiremos eliminar casi en su totalidad esta radiación indeseada.
Para llegar al resultado final de nuestra antena de doble banda se deberían realizar una serie de pasos previos.
El primer paso será el diseño de la estructura periódica que proporciona la condición PMC, dicha estructura será de tipo bed of nails. Para realizar este diseño se hará un estudio paramétrico previo en el que analizaremos cómo afectan al diagrama de dispersión, la variación de los distintos parámetros, ya que es en este diagrama donde veremos el margen de frecuencias que tenemos para el funcionamiento de nuestra antena, es decir, la zona donde no se propagarán modos entre las placas paralelas. Este diseño además se realizará en dos versiones, como a lo largo del resto del proyecto. En estas versiones lo que cambiará será la posición del gap, que forma parte principal de esta tecnología, siendo dichas posiciones:
- Entre el dieléctrico y la estructura AMC -- Tecnología microstrip convencional.
- Entre la antena (metal + ranura) y el dieléctrico -- Tecnología inverted microstrip gap.
Una vez diseñada la estructura de pines el siguiente paso será el diseño y estudio de la antena simple, variando la posición del gap en las dos versiones que se han comentado anteriormente.
Para poder hacer que la antena funcione de manera satisfactoria es necesario que respetemos las "normas" que nos impone el que sea una antena de ranura, esto es:
- La anchura del sustrato y el espesor de la línea de alimentación deber ser menor que λ.
- El largo de la ranura debe ser aproximadamente λ=2.
- El ancho de la ranura debe ser mucho menor que su longitud.
- La permitividad y el espesor del sustrato deben aportarnos pocas pérdidas para, de esta forma, conseguir un dieléctrico que nos aporte una eficiencia máxima. El tercer paso consistirá en la combinación de los dos diseños de antena con su respectiva
estructura AMC, analizando los resultados de las simulaciones y comparando los resultados
obtenidos en cuanto a la radiación y el parámetro S11 que nos ayudará a medir la adaptación
de nuestra antena.
Una vez que hayamos desempeñando todos estos pasos podremos pasar a la construcción que
finalmente se mandará al laboratorio para ayudarnos a completar la investigación realizada
durante este proyecto.
Previamente a este último paso diseñaremos una antena de doble banda basándonos en las
conclusiones extraídas de los pasos anteriores y la información con la que contábamos para
realizar el TFG. Esta antena constará de dos ranuras en forma de U, que producirán una
adaptación de la antena en dos frecuencias. Realizaremos, a su vez, un estudio previo para
determinar cuáles son las dimensiones de estas nuevas ranuras y con ello analizaremos cuáles
son los parámetros más restrictivos siguiendo en la línea de investigación que persigue este
trabajo.
Todo este desarrollo se hará sobre el programa de simulación CST Microwave Studio el cual nos
ayudará en la obtención de los resultados así como en el cálculo de parámetros importantes tales
como las dimensiones de la línea microstrip.
This document will present an example of gap waveguide technology use. The main advantage of this technology is that it has low losses. Specifically, we will present the design, simulation and construction of a dual band slot antenna made in this technology. It does not need contact between components, provides packaging of the circuits and prevents unwanted couplings and radiation. The antenna presented throughout this project is slot type and will be fed by a microstrip line. In general, these type of antennas produce back radiation, so it will be necessary to combine dual-band antenna with a structure that simulates the behavior of Perfect Magnetic Conductor (PMC). Therefore we will be able to eliminate almost all of this unwanted radiation. To achieve the dual-band slot antenna final result we have to perform some previous steps. The first step will be the design of the periodic structure that provides the PMC condition. This structure will be a bed of nails. In order to make this design, we have to perform a previous parametric study that will analyze how the di_erent parameters of the strucuture are going to affect the stopband. We will use the scatter plots to see how this changes the bandwith. This stopband is a bandwidth which forbids wave propagation in unwanted directions. This design will be made also two versions, as throughout the rest of the project. In these two versions the difference will be the gap position will affect the gap position as follow: - Between dielectric and pins surface AMC -- Conventional microstrip technology. - Between antenna (metal + slot) and the dielectric -- Inverted microstrip gap technology. Once the pin structure is designed the next step will be the design and study of the simple antenna by, changing the gap position in the two di_erent ways as we said before. To make a good antenna matching it is necessary to respect the \rules" imposed by the slot antenna. They are: - The substrate's width and power line's thickness must be less than λ. - The slot's length will be approximately λ=2 . - The slot's width must to be less than its length. - Permittivity of the substrate should give low losses to obtain a dielectric which achieves the maximum efficiency. The third step is the combination of the two antenna designs with their respective AMC structures, analyzing the results of the simulations and comparing the results obtained in terms of radiation. The parameter S11 will help us measure our antenna matching. Once we had performed all of these steps we can construct the final antenna which nally is going to be sent to the lab in order to complete the research for this project. Previously to this step we are going to design a dual band antenna based on the conclusions drawn from the previous steps and the information that we had previously to make the project. This antenna consists of two U-shaped slots which produce an antenna matching at two frequencies. Furthermore, we will do a study in order to de ne the dimensions of these new slots and we will analyze which are the most important parameters to define the dual-band. All of this development is going to be done in CST Microwave Studio program. This will help us to obtain the results as well as the calculation of important parameters such as the dimensions of the microstrip line.
This document will present an example of gap waveguide technology use. The main advantage of this technology is that it has low losses. Specifically, we will present the design, simulation and construction of a dual band slot antenna made in this technology. It does not need contact between components, provides packaging of the circuits and prevents unwanted couplings and radiation. The antenna presented throughout this project is slot type and will be fed by a microstrip line. In general, these type of antennas produce back radiation, so it will be necessary to combine dual-band antenna with a structure that simulates the behavior of Perfect Magnetic Conductor (PMC). Therefore we will be able to eliminate almost all of this unwanted radiation. To achieve the dual-band slot antenna final result we have to perform some previous steps. The first step will be the design of the periodic structure that provides the PMC condition. This structure will be a bed of nails. In order to make this design, we have to perform a previous parametric study that will analyze how the di_erent parameters of the strucuture are going to affect the stopband. We will use the scatter plots to see how this changes the bandwith. This stopband is a bandwidth which forbids wave propagation in unwanted directions. This design will be made also two versions, as throughout the rest of the project. In these two versions the difference will be the gap position will affect the gap position as follow: - Between dielectric and pins surface AMC -- Conventional microstrip technology. - Between antenna (metal + slot) and the dielectric -- Inverted microstrip gap technology. Once the pin structure is designed the next step will be the design and study of the simple antenna by, changing the gap position in the two di_erent ways as we said before. To make a good antenna matching it is necessary to respect the \rules" imposed by the slot antenna. They are: - The substrate's width and power line's thickness must be less than λ. - The slot's length will be approximately λ=2 . - The slot's width must to be less than its length. - Permittivity of the substrate should give low losses to obtain a dielectric which achieves the maximum efficiency. The third step is the combination of the two antenna designs with their respective AMC structures, analyzing the results of the simulations and comparing the results obtained in terms of radiation. The parameter S11 will help us measure our antenna matching. Once we had performed all of these steps we can construct the final antenna which nally is going to be sent to the lab in order to complete the research for this project. Previously to this step we are going to design a dual band antenna based on the conclusions drawn from the previous steps and the information that we had previously to make the project. This antenna consists of two U-shaped slots which produce an antenna matching at two frequencies. Furthermore, we will do a study in order to de ne the dimensions of these new slots and we will analyze which are the most important parameters to define the dual-band. All of this development is going to be done in CST Microwave Studio program. This will help us to obtain the results as well as the calculation of important parameters such as the dimensions of the microstrip line.
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Keywords
Antenas, Tecnología Gap Waveguide, Antenas de ranura doble banda, Antenas, Microstrip Gap Waveguide, Perfect Magnetic Conductor (PMC), Simulación, Radiocomunicación