Resumen en Inglés:

Abstract Monte Carlo simulations are widely used in analysis of interference between radiocommunication systems. The method performs n random experiments, each called an event, snapshot, or trial, to estimate the statistics of some parameter of the problem (for instance, the interference level). There is no formalization about the number of events necessary to run a simulation. In practice, this is often done based on the intuition of the analyst about the model. In this paper, we propose how to choose a number of events for Monte Carlo simulations. We address this issue by understanding that the protection criteria for radiocommunication systems are usually related to a quantile of the result, and then calculating the number of events for which it is also possible to estimate a confidence interval for it. Results show that, for a confidence level of 99.9%, it is possible to estimate confidence intervals for p-quantiles for p up to 99.89% with 10000 events.

Resumen en Inglés:

Abstract This work presents the development of a refractive index sensing methodology for measuring carbon dioxide concentrations, considering the effect of temperature environment. We propose and demonstrate, using simulations, the use of tapered and coated Long Period Gratings as a way to enhance the refractive index sensitivity. In addition, artificial neural networks were used to improve the estimation of carbon dioxide concentration, considering the crosssensitivity effect with temperature.

Resumen en Inglés:

Abstract Electromagnetic problems with moving structures are considered. For objects moving at a uniform velocity, the most popular technique used in the literature consists of a change of the reference frame and the utilization of Lorentz transformation of Maxwell’s electric and magnetic fields and Voigt-Lorentz transformations of space and time variables. In order to account for non-uniform motions, a numerical approach based on the finitedifference time-domain (FDTD) method is used. In this approach, Maxwell’s equations are applied without modification and the motion of objects is implemented by changing their positions in the FDTD time loop. Three types of movements are considered: vibration, rotation, and acceleration. Full-wave numerical results are reported for different objects in motion: observer, source, and reflecting electromagnetic surface. In all the problems analyzed, interesting results are obtained and these results are discussed in detail.

Resumen en Inglés:

Abstract The effect of mechanical stress on hysteresis losses of electrical steel sheets is investigated in this paper. Experimental data obtained from a dedicated bench are used in a curve fitting procedure to analyze the parameters behavior for a hysteresis losses model over a range of mechanical compressive and tensile stresses. By applying the concept of equivalent stress, a finite element model is simulated, and the hysteresis losses are a posteriori calculated considering an equivalent stress distribution over a single-phase induction motor stator.

Resumen en Inglés:

Abstract The rapid development of the Fifth Generation (5G) networks encourages researchers to improve the Radio over Fiber (RoF) technique to achieve data rates of 10 Gbps and beyond. That led to a significant increase in bandwidth and range while reducing latency and cost. This paper evaluates an Analog Radio over Fiber (ARoF) technique compatible with Next-Generation (NG) long-haul communication systems, aiming for simplicity and lower cost. Transmitting a 28 GHz, 256 Quadrature Amplitude Modulation (QAM) signal through Single-Mode Fiber (SMF) is possible by modulating it through two parallel Mach-Zehnder Modulators (MZM), allowing signal reception over long distances. The Error Vector Magnitude (EVM) appraises performance of the system. The simulation results indicate that the prototype can transfer data at 10 Gbps through the optical link up to 570 km with an EVM of 3.375% and received optical power of 4.015 dBm. The proposed system supports a high bit rate and maintains the EVM within 3GPP limits, making it superior to peer publications and highly appropriate for NG long-haul communication systems.

Resumen en Inglés:

Abstract The technique of electromagnetic characterization of materials in free space allows for the measurement of constitutive properties without making contact with the material being measured. Characterization methods in Free Space are naturally suited for Electromagnetic Radiation Absorbing Materials (RAM) but are also important in applications where the material sample to be measured does not undergo major interventions. They consist of evaluating a received signal resulting from a free-space transmission through two horn antennas with beam collimating lenses and a Vector Network Analyzer (VNA). The characteristics of the transmitted signal are modified by a material positioned between the transmitting and receiving antennas. This work presents methods for electromagnetic characterization in Free Space, in the frequency range of 8.2 to 12.4 GHz (X-Band), in a semi-anechoic chamber, seeking the development of measurement processes that present results with repeatability and reliability. The measurements were made with standard and electromagnetic radiation absorbing materials. The measurement technique presented 95% of efficiency.

Resumen en Inglés:

Abstract This work proposes the integration of a monopole antenna with a frequency selective surface (FSS) with double square loop geometry, which operates in the ISM (2.4 - 2.4835 GHz) and IEEE 802.11 WLAN (5.15-5.725 GHz) bands. The FSS was developed to be integrated into a microstrip monopole antenna, aiming to improve some of its radiative features, such as gain, directivity, and front-to-back ratio (FBR). We show that the double square loop FSS operates in bands from 1.91 to 3 GHz and from 4.64 to 6.56 GHz, fully covering the bands of interest. A prototype of the proposed structure was assembled and both the numerical simulation and the experimental results show that the antenna integrated with FSS presents significant improvements in all parameters, compared to the antenna without FSS. Because of the interest frequency ranges the proposed structure can be applied in non-invasive biomedical applications.

Resumen en Inglés:

Abstract In this paper, a novel, compact, and high-performance dual-band filtering power divider is presented. The proposed circuit is constructed from a dual-band power divider and open-circuited stepped-impedance resonators. The dual-band power divider is realized by using two-section impedance transformers. To achieve the filtering function, three open-circuited stepped-impedance resonators are attached to three ports of the dual-band power divider to create a transmission zero between two operating bands. The proposed dual-band filtering power divider has a compact size, ease of fabrication, and high performance in terms of low insertion loss, high isolation, and good return losses. In order to validate the design concept, a dual-band filtering power divider operating at 1 GHz and 2.3 GHz with the size of 0.26 λg×0.23λg is designed, fabricated, and measured. The experiment results show that the dual-band filtering power divider has better than 37.1 dB isolation, 23.3 dB return loss, and 3.49 dB insertion loss at two central frequencies. The measured fractional bandwidths (|S11| < -14 dB) are 30.7% for the first passband and 13.8% for the second.

Resumen en Inglés:

Abstract In the present work an analytical formulation to synthesize non-uniform phase distributions at cylindrical apertures is described. Assuming three distinct amplitude distributions, the respective phases are established to provide cosecant-squared radiation patterns. Non-uniform amplitude distributions are investigated and adopted to reduce sidelobe levels and unwanted ripples in the synthesized radiation patterns. Analytical results for the established amplitude and phase distributions at cylindrical apertures are presented. The radiation patterns for such distributions are obtained by aperture method analysis, successfully demonstrating the usefulness of the new analytical formulation.

Resumen en Inglés:

Abstract In this article, the authors propose changes to a microwave system for measuring the relative humidity of hollow concrete blocks presented in the literature, aiming to improve the system’s sensitivity. The operating frequency range was changed from 2.5 GHz to 5.8 GHz. This reduced the dimensions of the antenna arrays used in the system. Five block samples were used in this work. The frequency selective surface (FSS) used as a sensor has been modified, from a double circular ring to a square loop, which presents a single-band frequency response. The results obtained in this work showed a high correlation between the frequency variation and the relative humidity level. First, second, and third-order functions were compared to see which would better relate resonance frequency to relative humidity. The second-order function presented the best results, considering the Mean Absolute Percentage Error (MAPE), the Mean Square Error (RMS), and the coefficient of determination. We performed a sensor sensitivity analysis showing that the new proposed system is more sensitive than others presented in the literature.