Laércio M. Mendonça

Effect of square slot in microstrip patch antennas using artificial neural networks

This paper presents an investigation of the properties of square slot microstrip patch antennas. These antenna geometries are obtained by printing square slots in the conducting patches of rectangular microstrip antennas. Measured results of the return loss versus frequency are used in the ANN training. A particular set of measured results is used in the validation of the ANN. The effect of the feed position and square slot size on resonant frequencies is investigated using the developed ANN.

Study of the geometric complexity reduction of a quasi-fractal FSS using WCIP

This work presents a design procedure for a simplified geometric quasi-fractal FSS, that starts with the analysis of the effect of several geometry details (small gaps) on the frequency behavior. Firstly FSS structures are numerically analyzed, using the Wave Concept Iterative Procedure (WCIP). Secondly they are experimentally characterized. Thereafter a comparison between simulated and measured results is performed, as well as an investigation of the effect of the FSS geometry on the resonant frequency using the electric and magnetic field distributions, the latter through the electrical current density vector.

Simulated and measured results for a S-shaped monopole patch antenna on a BiNbO 4 layer

This work presents a numerical and experimental investigation of the resonant properties of a microstrip-fed S-shaped monopole patch antenna on a high permittivity BiNbO4 ceramic substrate. The high electrical permittivity of the ceramic substrate provided a reduction in the resonator dimensions. A good agreement was observed between simulated and measured resonant frequency of the considered antenna.

Optimizing empirical propagation models for LTE and LTE-A using genetic algorithms at 879 MHz

This paper presents the results of the application of a Genetic Algorithm (GA) to predict path loss for urban areas for Long Term Evolution (LTE) and Long Term Evolution Advanced (LTE — A) networks at 879 MHz using empirical propagation models. We conducted a comparative test, where simulated Free Space and Ericsson 9999 models along with their optimized versions were compared with experimental data obtained from a measurement campaign performed in [1]. The results showed a closer approximation of the models modified with GA with measurements. We hope this will enable an estimation of the signal closer to reality, avoiding major errors in planning and implementations of LTE and LTE-A networks for this type of area and frequency.

Analysis of asymmetric coupled cylindrical microstrip lines

Cylindrical microstrip lines, or non-planar microstrip lines, are used in the development of several microwave integrated circuits to be mounted on curved or cylindrical conducting surfaces [1]-[3].Cylindrical microstrip lines, or non -planar microstrip lines, are used in the development of several microwave integrated circuits to be mounted on curved or cylindrical conducting surfaces [1] -[3]. The analysis of cylindrical microstrip lines has been performed by variational methods [2], and mapping methods [3], for quasi -TEM propagation. In this work, a combination of the Greens function technique and the moment method is used to analyze asymmetric coupled cylindrical microstrip li -. nes, such as microstrips on double layers and with overlay. A cross -sectional view of a pair of coupled cylindrical microstrip lines with overlay is shown in Fig.1. Coupled cylindrical microstrip lines on double layers are obtained by placing the conducting strips at the interface between dielectric regions 2 and 3 (Fig.1). In the analysis, the dielectric regions are considered to be isotropic ones, The thicknesses of the conducting strips are neglected. The Greens functions for the structures considered in this work are obtained by solving Laplaces Equation in each dielectric region and by imposing the proper boundary conditions. The expression of the Greens function obtained from an elementary strip, at r = r2 (Fig.1), is

Artificial neural networks for multi-slot microstrip patch antennas

This work presents a study of implementation procedures for multi-slot microstrip patch antennas characterization for wireless communication systems. An artificial neural network multilayer perceptron is used to locate the bands of operational frequencies of the antenna for different geometrics configurations. The antenna is designed, simulated and measured in laboratory. The obtained results are compared and a good agreement is observed. The developed neurocomputational procedures can be extended to analyze other antenna geometries for wireless applications.

Numerical characterization of RFID tags using WCIP

This paper presents the numerical characterization of two RFID tags. The analysis of these structures is made using the WCIP. Are compared the initial results found in literature with those obtained through simulations on WCIP with objective to show that this method is able to analyze such structures. Is shown still, the behavior of electric and magnetic fields, the latter through the electrical current density vector. Are presented suggestions for the continuation of this work.

Analysis of suppression capacity of dipoles in adaptive arrays for CDMA systems

We consider the use of dipoles as sensor elements in adaptive array antennas with configurations linear, circular and planar for DS-CDMA cellular communication systems.