Frequency selective surfaces to camouage directive antennas

Abstract

Abstract. This master's thesis is focused on the improvement in the design of Frequency Selective Surfaces (FSSs) and metasurfaces in order to develop diffrent applications: short waveguide filters, antenna camou aging and sensors. Thus, we start with the general study of FSSs and some basic definitions as the radar cross section and the quality factor. Besides, a brief description of the computational analysis of FSS is presented. Then, we focus on the mathematical description of the scattering parameters, obtained when an electromagnetic wave impinges upon a two-dimensional periodic array, the FSS, made of electrically small resonators ,metasurfaces; useful for any angle of incidence. This approach yields some useful constraints between the scattering parameters as well as their paths in the complex plane, which form a mathematical treatment that has not been previously described in the literature. In the second part, we study the properties of the small resonators used for the metasurface design, and the models used to predict the resonance of thin metasurfaces. Subsequently, we analyse the geometric parameters that increase the quality factor of a metasurface by means of two new proposed models to predict the resonant frequency. The novelty is that these models do not require full-wave numerical simulations, so its design is considerably facilitated. In fact, these results are summarized in a convenient computer program that computes the resonance frequency of SRR based resonators and their complementaries in terms of the geometrical parameters only. Furthermore, we explore three different applications verified at an experimental level: A short waveguide filter of high quality factor fabricated and used to verify the proposed models as well as to analyse the resonators of better performance. Besides, a device to measure the permittivity of liquids, based on a microstrip line technology. It was characterized using liquids whose permittivity was known. Then, it was used to estimate the permittivity of a solution of silver nanoparticles. Finally, a small metasurface that behaves as a spatial filter served to improve the manufacturing processes to be made in the future, and to propose the design of a filtenna: Filter + Antenna. The results obtained from this last proposal are helpful for antenna camouflaging.

La tesis de este máster se centra en la mejora en el diseño de Frecuencia Selectiva ? Superficies (FSS) y metasurfaces el fin de desarrollar aplicaciones di erent: corto ltros de guía de onda, antena camou envejecimiento y sensores. Por lo tanto, partimos de la general, estudio de FSS y algunos niciones De básicos como la sección transversal de radar y el factor de calidad. Además, se presenta una breve descripción del análisis computacional de SFS. Luego, se centran en la descripción matemática de los parámetros de dispersión, obtenida cuando un onda electromagnética incide sobre una matriz periódica de dos dimensiones, el SFS, hecho de eléctricamente pequeños resonadores, metasurfaces; útil para cualquier ángulo de incidencia. Este enfoque produce algunas limitaciones útiles entre los parámetros de dispersión, así como su trayectorias en el plano complejo, que forman un tratamiento matemático que no ha sido descrito previamente en la literatura. En la segunda parte, se estudian las propiedades de la pequeños resonadores utilizados para el diseño Metasurface y los modelos utilizados para predecir el resonancia de metasurfaces delgadas. Posteriormente, se analizan los parámetros geométricos que aumentar el factor de calidad de un Metasurface por medio de dos nuevos modelos propuestos para predecir la frecuencia de resonancia.