Glauco Fontgalland

Miniaturized patch antenna for the Radio Frequency Identification of metallic objects

The growing interest in the Radio Frequency Identification (RFID) technology is giving rise to new applications, in particular for the identification of metallic objects. This interest has initiated the development of new designs for RFID tag antenna. This paper presents a UHF miniaturized patch antenna aimed at this application. The patch antenna is fed by a balanced feed to avoid a cross-layered construction and matched with a stub. Its miniaturization is achieved by inserting a u-shaped slot in the radiating patch.

Analysis of Multilayer Amplifier Structure by an Efficient Iterative Technique

A new compact microwave amplifier structure using an iterative technique based on the wave concept iterative procedure (WCIP) is presented. This new multilayer structure is composed of five planar interfaces of strip lines. The technique used to model this structure provides a mixed resolution in modal and spatial domain. By taking the best advantage of each resolution domain, a lower computing time is obtained. The purpose of this paper is to demonstrate that a near field amplification technique is achievable and the WCIP is suitable to electromagnetic analysis of this kind of structure. The numerical results show 13.4 dB gain at 5.6 GHz.

Design of frequency selective surfaces using a novel MoM-ANN-GA technique

This work describes a new application of genetic algorithm (GA) for frequency selective surfaces (FSSs) design. The works innovation was the introduction of an artificial neural network (ANN) as a fitness function into GA. The ANN model was trained with accurate data provided by FSSs simulations using the method of moments (MoM). The founded advantages in the design of FSS devices using the technique through of genetic algorithms and neural networks are discussed and the results are presented as way to validate the new proposed technique.

A new quasi - isotropic antenna for ultra - wideband application

In this paper, we propose a new compact antenna design for applications where an ultra-wideband (UWB) frequency range is needed. The main features of the proposed antenna is the capability of generate a quasi-isotropic radiation pattern. For this case, the proposed antenna is designed to operate from 2.17 GHz to 2.68 GHz. The construction details of the conceived antenna are presented and discussed. The measurements of reflection coefficient and radiation pattern were made in UFCG/LEMAs laboratory. The experimental results have good agreement with the simulated one. The simulation was made using the CST - Microwave Studio. The antenna is of easy construction and has application in wireless system and network sensors, field measurement or electromagnetic compatibility (EMC).

DC-Amplifier-Input-Offset-Voltage Control in a Constant-Temperature Thermoresistive-Sensor-Measurement Instrument

In this paper, the effect of dc amplifier input offset voltage on the static and dynamic performances of a generic constant-temperature thermoresistive-sensor-feedback circuit (CTC) is reviewed. A negative-feedback automatic control circuit for the input offset voltage is proposed in order to assure a stable operation of the CTC and to obtain optimal response time. Experimental evaluation results of the proposed circuit performance are presented

An Efficient Algorithm for Planar Circuits Design

An efficient algorithm for planar circuits design based on the wave concept (WCIP) is formulated and applied. The algorithm is based in the use of a recursive relationship between incident waves and reflected waves from a discontinuity plane instead of an integral equation method. The advantage here are that no matrix inversion is required, the convergence is insured independently of the kind or numbers of interfaces of the structure and well adapted to multi-layered circuit characterization, antenna coupling over concentric cylinders. The method herein presented solves for the current density and the tangential electrical field on the interface. The robustness of this formulation permits to solve, independently of the frequency or physical size, several problems by applying dual quantities. In order to simplify calculations and accelerate the convergence, a two-dimensional fast modal transformation (FMT) algorithm using periodic walls is used with the 2D-FFT algorithm. As example, the simulation results for two different structures, an open microstrip line and a microstrip patch antenna, are presented.

A New Simple UWB Monocycle Pulse Generator

A new simple ultra-wideband (UWB) monocycle pulse generator based on step recovery diode is presented. This pulse generator uses nonlinear components with a single power supply and microstrip transmission lines. It is made up of three parts : a Gaussian pulse generator, an impulse-shaping network, and a monocycle-pulse forming circuit. The proposed circuit allows to generate ultra-short Gaussian monocycles of 270-ps pulse duration with a bandwidth of 9-GHz and a pulse repetition rate of 100-MHz.

Analysis of quasi-square open ring frequency selective surface using the Wave Concept Iterative Procedure

This work presents the analysis of quasi-square open ring frequency selective surface, FSS, using the Wave Concept Iterative Procedure, WCIP. As this structure presents a strongly dependence of the electric field polarization, different frequency bands can be selected. Furthermore, there is a coupled strips region and its length can be used for frequency adjustment. The behavior of the electric fields and how it can affect the resonant frequency is discussed. Numerical and measured results for the frequency of resonance are compared and a good agreement is observed.

Proposal of a new compact isotropic antenna

In this paper we propose a dipole with new geometry to generate an isotropic radiation pattern in the far field region. Derivate from the classical half-wave dipole, the pattern for the new compact geometry has the same distribution into three orthogonal axis. The axial ratio for the E field component is near to one for the new dipole. The measurements and simulations of the radiation pattern are in agree. Also, the measured and simulated results for the reflection coefficient is very closed. The new compact isotropic antenna allows the development of compact measurement sensors/antennas. Index Terms — Isotropic antenna, uniform radiation pattern, bent dipole, axial ratio, compact antenna.

Normality and Correlation Coefficient in Estimation of Insulators’ Spectral Signature

This work aims to classify the contamination state in insulators using statistical signal processing approaches. When subjected to high voltage, insulators can radiate radio frequency signals (corona effect). The histograms, normality, and correlation coefficient statistical methods are used to estimate the pollution state in glass insulators when subjected to 8 kV. It is shown that in particular situations the histograms can be used to distinguish clean and dirty insulators. The histogram limitation analysis can be improved using the correlation coefficient and the normality or Gaussianity test. Indeed, it is shown that using these parameters into an analysis per sub-bands, it is possible to estimate the pollution state of the insulators. That is, the analysis using these tools checks if the insulators spectra under test are noticeably different from the clean one, used as reference. It is achieved eliminating the fast variation of the correlation coefficient based on the amplitude and width of the peaks. The tests were done up to the frequency of 1 GHz using measured data.