Banca de DEFESA: RAFAEL ALEX VIEIRA DO VALE

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : RAFAEL ALEX VIEIRA DO VALE
DATE: 15/04/2026
TIME: 14:00
LOCAL: Remota via Google Meet
TITLE:

Cylindrical Dielectric Resonator Antennas Obtained from Recycled Ceramic Tile and Brick Waste

KEY WORDS:

Dielectric Resonator Antennas, Ceramic Waste, Bricks and Tiles, Frequency Selective Surface, Sub-6GHz

PAGES: 163
BIG AREA: Engenharias
AREA: Engenharia Elétrica
SUBÁREA: Telecomunicações
SPECIALTY: Teoria Eletromagnetica, Microondas, Propagação de Ondas, Antenas
SUMMARY:

This work proposes the fabrication of cylindrical dielectric resonator antennas (DRAs) from ceramic residues of bricks and tiles. The cylindrical samples were produced by grinding the ceramic waste, molding them into the desired shape under a uniaxial load of 100 kN using a universal testing machine, and sintering in a resistive furnace at distinct temperatures of 1000°C, 1050°C, and 1100°C for 3 hours. The obtained specimens were analyzed regarding their microstructural behavior through X-ray diffraction (XRD) measurements, energy-dispersive X-ray spectroscopy (EDS) to identify the Bravais lattices and phase composition constituting the ceramic, and images captured using a scanning electron microscope (SEM) to observe the degree of grain coalescence. Physical characterization was also performed based on porosity measurements of the developed ceramic cylinders. To justify the application in dielectric resonator antennas, the dielectric behavior of the samples was studied by measuring the real relative permittivity and loss tangent as a function of frequency using a vector network analyzer (VNA). The data acquired from these measurements enabled the proposal of DRA models. The DRA designs followed the aperture-coupled feeding method, with variations in the feed slot inclination of the DRA and the implementation of a band-stop frequency selective surface (FSS) at different positions (Z) relative to the CDRA. This was done to analyze potential changes and improvements in the parameters of return loss, bandwidth, realized gain, front-to-back ratio, and the 2D radiation patterns in co-polarization and crosspolarization, using an FR-4 substrate. Simulations showed good impedance matching in all situations, but with narrow bandwidths around 310 MHz for antennas without feed slot inclination, operating with and without the FSS. Realized gains were less than 7 dBi, and the front-to-back ratio exceeded 20 dB with the FSS at Z = 1.5 cm. For this configuration, measurements showed a certain frequency shift compared to simulations, around 5.43 GHz, but with larger bandwidths exceeding 700 MHz with the FSS at Z = 3 cm. The realized gain surpassed 10 dBi (the maximum value among the measured situations) for the CDRA without the FSS; for cases with the FSS, gains were above 6.5 dBi. The FBR was consistently higher in antennas with the FSS, reaching 19.68 dB also at Z = 1.5 cm, a result of redirecting rear radiation to the main antenna direction, which confirmed the simulated radiation patterns. Simulations of the CDRA with a 45° feed slot inclination exhibited large bandwidths exceeding 1700 MHz, gains above 5.7 dBi (notably 7.65 dBi for the antenna with the FSS at Z = 4.5 cm), and among the front-toback ratios, the highest level recorded was 18.95 dB with the FSS at Z = 1.5 cm. Measurements of this CDRA, with a modified ground plane, also indicated a frequency shift to 5.6 GHz, different from the 5.2 GHz in simulations, with bandwidths lower than in simulation but reaching 650 MHz with the FSS at Z = 4.5 cm. Gains of 8.33 dBi without the FSS and 5.45 dBi with the FSS at Z = 6 cm were obtained, lower than the situation without slot inclination. However, the front-to-back ratios were consistently higher than in the situation without the FSS, confirming the behavior of the radiation patterns. The proposed antennas are presented for potential applications in wireless communication systems in the Sub-6GHz band, utilizing ceramic waste as alternative materials and promoting a more sustainable method for constituting this type of device.

COMMITTEE MEMBERS:
Presidente - 2524053 - ANTONIO LUIZ PEREIRA DE SIQUEIRA CAMPOS
Interno - 1412682 - VICENTE ANGELO DE SOUSA JUNIOR
Externo ao Programa - 1840342 - MARCIO EDUARDO DA COSTA RODRIGUES - UFRNExterno à Instituição - ALFREDO GOMES NETO - IFPB
Externo à Instituição - ISAAC BARROS TAVARES DA SILVA
Externo à Instituição - MAURICIO WEBER BENJÓ DA SILVA - UFF