Waveguide Model for Thick Complementary Split Ring Resonators

This paper presents a very simple analytical model for the design of Frequency Selective Surfaces based on Complementary Split Ring Resonators (CSRR) within the microwave range. Simple expressions are provided for the most important geometrical parameters of the model, yielding an accurate description of the CSRR resonance frequency and avoiding full-wave numerical simulations. Besides, a qualitative description of the band-pass filter behavior of these structures is described, considering its high quality factor Q.Comment: Paper accepted at the 2014 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting. paper submission #286

Frequency selective surfaces to camouage directive antennas

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.Maestrí

Analysis of a Waveguide-Fed Metasurface Antenna

The metasurface concept has emerged as an advantageous reconfigurable antenna architecture for beam forming and wavefront shaping, with applications that include satellite and terrestrial communications, radar, imaging, and wireless power transfer. The metasurface antenna consists of an array of metamaterial elements distributed over an electrically large structure, each subwavelength in dimension and with subwavelength separation between elements. In the antenna configuration we consider here, the metasurface is excited by the fields from an attached waveguide. Each metamaterial element can be modeled as a polarizable dipole that couples the waveguide mode to radiation modes. Distinct from the phased array and electronically scanned antenna (ESA) architectures, a dynamic metasurface antenna does not require active phase shifters and amplifiers, but rather achieves reconfigurability by shifting the resonance frequency of each individual metamaterial element. Here we derive the basic properties of a one-dimensional waveguide-fed metasurface antenna in the approximation that the metamaterial elements do not perturb the waveguide mode and are non-interacting. We derive analytical approximations for the array factors of the 1D antenna, including the effective polarizabilities needed for amplitude-only, phase-only, and binary constraints. Using full-wave numerical simulations, we confirm the analysis, modeling waveguides with slots or complementary metamaterial elements patterned into one of the surfaces.Comment: Original manuscript as submitted to Physical Review Applied (2017). 14 pages, 14 figure

Experimental Synthetic Aperture Radar with Dynamic Metasurfaces

We investigate the use of a dynamic metasurface as the transmitting antenna for a synthetic aperture radar (SAR) imaging system. The dynamic metasurface consists of a one-dimensional microstrip waveguide with complementary electric resonator (cELC) elements patterned into the upper conductor. Integrated into each of the cELCs are two diodes that can be used to shift each cELC resonance out of band with an applied voltage. The aperture is designed to operate at K band frequencies (17.5 to 20.3 GHz), with a bandwidth of 2.8 GHz. We experimentally demonstrate imaging with a fabricated metasurface aperture using existing SAR modalities, showing image quality comparable to traditional antennas. The agility of this aperture allows it to operate in spotlight and stripmap SAR modes, as well as in a third modality inspired by computational imaging strategies. We describe its operation in detail, demonstrate high-quality imaging in both 2D and 3D, and examine various trade-offs governing the integration of dynamic metasurfaces in future SAR imaging platforms

MEASUREMENTS OF PERMITTIVITY BASED IN MICROSTRIP TECHNOLOGY *

The Complementary Split Ring Resonator (CSRR) geometry is used in conjunction with a microstrip line to create a device able to measure the electric permittivity of liquids. Simulations and measurements of the S-parameters are performed to correlate the resonance frequency and the permittivity of _ve common samples in order to calibrate the device. Once calibrated, we also provide an estimate of the permittivity of a solution of silver nanoparticles. These measurements are attractive given the limited the noninvasive techniques available for nanomaterial characterization and the lack of results at the microwave range. The results estimate the relative permittivity of the silver nanoparticles  Er(Ag-NPS)=101.16 +/- 19.53

Medidas de permitividad basadas en tecnología de microcinta *

El anillo resonador cortado complementario (CSRR) se utilizó en conjunto con una l__nea de microcinta para crear un dispositivo capaz de medir la permitividad de líquidos. La simulación y medida de los parámetros de dispersión fueron obtenidos para correlacionar la frecuencia de resonancia calibrar el dispositivo. Una vez calibrado, fue possible obtener un valor estimado de la permitividad de una solución con nanopartículas de plata. Estas medidas son interesantes dadas las limitadas técnicas no invasivas disponibles para la caracterización de nanomateriales y la falta de medidas en el rango de microondas. Los resultados estiman la permitividad de la solución de nanopartículas Er(Ag-NPS)=101.46 +/- 19.53 .The Complementary Split Ring Resonator (CSRR) geometry is used in conjunction with a microstrip line to create a device able to measure the electric permittivity of liquids. Simulations and measurements of the S-parameters are performed to correlate the resonance frequency and the permittivity of _ve common samples in order to calibrate the device. Once calibrated, we also provide an estimate of the permittivity of a solution of silver nanoparticles. These measurements are attractive given the limited the noninvasive techniques available for nanomaterial characterization and the lack of results at the microwave range. The results estimate the relative permittivity of the silver nanoparticles  Er(Ag-NPS)=101.16 +/- 19.53

Application of range migration algorithms to imaging with a dynamic metasurface antenna

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