LOCEM Laboratory of Telecommunications and Materials Science and Engineering

Fortaleza, Brazil

LOCEM Laboratory of Telecommunications and Materials Science and Engineering

Fortaleza, Brazil
SEARCH FILTERS
Time filter
Source Type

Silva M.A.S.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering | Silva M.A.S.,Federal University of Ceará | Fernandes T.S.M.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering | Sombra A.S.B.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering
Journal of Applied Physics | Year: 2012

In this paper an alternative method for the measurement of the temperature coefficient of resonant frequency (τ f), is presented. The traditional method (based on the Courtney method) present some limitations of measuring the values of τ f, for samples with high dielectric loss due to their inability to observe clearly the TE 011 mode. The alternative experimental setup, to measure the τ f value, is based on the variation of the temperature of the dominant mode of a dielectric resonator antenna. The method is quite compatible with the measurement of τ f, based on the Courtney method. It presents the advantage that it is less sensitive to the sample loss. In the studied samples, with loss higher than 10 -2, the τ f were obtained. Samples of known τ f were measured in both methods, using the configuration proposed by Courtney and the present study. The alumina (Al 2O 3) and calcium titanate (CaTiO 3) were selected because they have well known values of τ f and have low dielectric losses, the bismuth niobate and titanium (Bi 3NbTiO 9) was chosen because it is not possible to measure its τ f by the traditional method due to its high dielectric loss. The obtained results, by measuring, the τ f value of CaTiO 3 and Al 2O 3, in this proposed method, present excellent agreement when compared to the traditional Courtney, transmission method. It was also very efficient for measurements of the τ f value, of high dielectric loss materials (>10 -2), as for the bismuth and titanium niobate (Bi 3NbTiO 9). The analysis of the temperature coefficient of resonant frequency (τ f) in dielectric resonators is an important property for the development of electronic devices. This is because the τ f is a fundamental parameter, for the production of new components like filters, oscillators and antennas, with high thermal stability. © 2012 American Institute of Physics.


Silva P.M.O.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering | Fernandes T.S.M.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering | Oliveira R.M.G.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering | Silva M.A.S.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering | Sombra A.S.B.,LOCEM Laboratory of Telecommunications and Materials Science and Engineering
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2014

In this work, BBT has been synthesized by solid-state reaction. X-ray diffraction and Raman spectroscopy were used to structurally characterize the samples. The dielectric properties were analyzed by impedance spectroscopy for radiofrequency range. For microwave range, the dielectric properties were analyzed by the Hakki-Coleman method. The properties of a DRA made from BBT were obtained by numerical simulations and compared with experimental results. The results show that the synthesis of BBT was effective from 800 C, showing nanosize particles (35-45 nm) with tetragonal symmetry. Raman spectra exhibited all active modes characteristic of BBT. The dielectric properties of BBT presented high values of dielectric permittivity (É′ = 52.40 for microwave range and É′ > 100 for radiofrequency range). BBT ceramic based showed negative values of (-422.11 ppm C-1) temperature coefficient of resonant frequency. The DRA BBT-based demonstrated the use as an antenna, exhibiting small gain of 1.1 dBi and efficiency of 32.5%. © 2013 Elsevier B.V.

Loading LOCEM Laboratory of Telecommunications and Materials Science and Engineering collaborators
Loading LOCEM Laboratory of Telecommunications and Materials Science and Engineering collaborators