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In this paper, a semi-empirical method for the prediction of rain attenuation in slant paths and terrestrial links is proposed. The method uses the same simplified model of equivalent rain cell that is the basis for the ITU-R rain attenuation prediction methods but, additionally, the concept of an effective rain rate is introduced. This allows the use of the full rainfall rate distribution for the prediction of the rain attenuation distribution and the unification of the slant path and terrestrial links prediction algorithms. The numerical coefficients in the method’s expressions were derived by multiple non-linear regressions using the experimental data currently available in the ITU-R data banks. Test results indicate that the proposed method provides significant improvement over the current ITU-R methods.Resumo em Inglês:
This paper presents a new approach to upgrade and extend the reach of the current passive optical network (PON) by using wavelength division multiplexing (WDM) in the standardized optical grid of gigabit PON (In-band WDM PON overlay). The aim is to increase the number of optical distribution networks (ODNs) fed by a single fiber while preserving the users bandwidth. In this approach four downstream (DS) wavelength signals are transmitted from an optical line terminal (OLT) to four different ODNs using the standard DS PON spectrum ranging from 1480 to 1500 nm. The upstream (US) signals from the four different ODNs are also wavelength multiplexed within the standardized US PON spectrum ranging from 1270 to 1330 nm. Experimental proofs of concept are presented in a 20 km PON serving 32 ONTs and in a 58 km extended PON in order to demonstrate the feasibility of this proposal.Resumo em Inglês:
Two Dimensional (2D) circular Photonic Crystal Ring Resonator (PCRR) based Add Drop Filter (ADF) is designed and the impacts of rod shape with its filling fraction is examined to evaluate the performance of the filter. The ADFs are devised separately using rods of circular, hexagonal and square shape in square lattice PC. For various values of rod’s cross sectional dimension and shape, the resonant wavelength, coupling efficiency, dropping efficiency, Q factor and passband width of the designed filters are investigated through simulation. The calculated filling fraction of a square, circular and hexagonal rods in the lattice structure is 11.9006 × 10-12 sq.m, 13.1134 × 10-12 sq.m and 15.16 × 10-12 sq.m and their respective resonant wavelength is 1494 nm, 1504 nm and 1520 nm. It is observed that there is 1 nm wavelength shift to longer wavelength while increasing the overall filling fraction by 0.1233 × 10-12 sq.m. From the simulated results, it is observed that the circular and hexagonal rods based ADF impart better performance than square rod based ADF.Resumo em Inglês:
In this work, we investigate the utilization of transmission power control as mechanism to increase the energy efficiency in optical code division multiplexing access (OCDMA) networks. We have modeled the energy efficiency considering the optical fiber transmission and network infrastructure as encoders, decoders and star coupler. In the analyzed scenario, this model confirms that the energy consumption of the network infrastructure is larger than the energy consumption of the transmission infrastructure; On the other hand, we have proposed a scheme to define the energy efficiency according to the BER level accomplished with the quality of service (QoS) requirements. The main results showed that it is possible to save 70% of the transmitted energy per bit with the penalty of one order of magnitude of BER.Resumo em Inglês:
This paper presents measured data and electromagnetic FEM field calculations as techniques for detecting and analyzing eccentricity in three-phase induction motors. Also it presents experimental results for detecting broken bars in induction motor rotors. A search-coil is used as magnetic field sensor to measure the stray magnetic flux outside the motor. It is a totally non-invasive method.Resumo em Inglês:
This paper presents a numerical investigation for a double screen frequency selective surface (FSS) with perfectly conducting rectangular patch elements. The analysis uses a full wave technique to obtain the scattering characteristics. The analysis combines the immitance approach and the method of moments to obtain the scattered fields and, consequently, the scattering characteristics of the structure. For validation of the analysis, numerical results are compared with measured and numerical results presented by another authors. A good agreement was obtained with experimental results.Resumo em Inglês:
This paper discusses how symbolic computation combined with a circuit model can be used for analyzing planar multilayer structures, in a manner suitable for educational approach. Working in the Fourier domain, expressions for the transversal spectral Green’s functions are evaluated in compact, closed form using the symbolic computation capability of the Mathematica package. Printed antennas were analyzed through the method of moments. Further validation was achieved with the IE3D and HFSS packages.Resumo em Inglês:
This article describes the CPW-feed ultra wideband tree type monopole fractal antenna and it’s backscattering. The prototype antenna is fabricated with optimized dimension. The experimental result of this antenna exhibits the ultra wideband characteristics from 5.0 GHz to 14.0 GHz. The experimental and simulated results are in good agreement. The effects of various design parameters on impedance bandwidth have also been studied in detail using EM simulator. The nature of H and E - plane radiation patterns are omni-directional and bidirectional respectively. The measured group delay is almost constant throughout band. This indicates the phase linearity. The monostatic RCS of antenna is also simulated iteration-wise for antenna and structural scattering mode. This antenna can be useful for UWB system, Microwave Imaging and vehicular radar and military high data rate wireless communications.Resumo em Inglês:
This paper presents a computational model of electrons dynamics and gain in four-level two-electron atomic systems. These systems, submitted to an electromagnetic wave, are governed by Pauli Exclusion Principle and they are modeled using the Time-Domain Transmission Line Matrix (TLM) method with the symmetrical condensed node (SCN) with novel voltage sources. The development of the proposed model is based on the incorporation, in Maxwell's equations, of the coupled rate equations with Pauli Exclusion Principle, taking into account the dynamic pumping in the TLM formulation. The scattering matrix characterizing the SCN with the new voltage sources is provided and the numerical results are compared with those of the literature or with the theoretical ones.Resumo em Inglês:
This paper presents Artificial Neural Network (ANN) implementation for the Radio Frequency (RF) and Mechanical modeling of lateral RF Micro Electro Mechanical System (MEMS) series micro machined Single pole double through (SPDT) switch. We propose an efficient approach based on ANN for analyzing the losses in ON and OFF state of lateral RF MEMS series switch by calculating the S-parameters. The double beam structure has been analyzed in terms of its return, isolation and insertion losses with the variation of its passive circuit component values. The effect of design parameters has been analyzed and the lateral switch was realized with low insertion loss, high return and isolation losses. ANN model were trained with five different training algorithms namely Levenberg-Marquart (LM), Bayesian Regularization (BR), Quasi - Newton (QN), Scaled Conjugate Gradient (SCG) and Conjugate Gradient of Fletcher - Powell (CGF) to obtain better performance and fast convergence. The results from the neural model trained by Levenberg-Marquardt back propagation algorithm are highly agreed with the theoretical results available in the literature. The neural networks shows the better results with the highest correlation coefficient which measures the strength and direction of linear relation between two variables (actual and predicted values) (0.9998) along with lowest root mean square error (MSE) of (0.0039).Resumo em Inglês:
A single substrate layer double metallic plane frequency selective surface (FSS) is designed with miniaturized electrical elements and two tunable pass-bands enabling Wireless Local Area Network applications. Each FSS periodic cell consists of a metallic square loop on the top metal layer and its complementary etched on the bottom metal layer separated by a thin dielectric layer. This designed FSS provides two tunable transmission bands. For predicting the frequency selective characteristics of the designed FSS an equivalent electric circuit model is also presented. To satisfy the needed requirements for Wireless Local Area Network (WLAN) applications the designed structure is optimized. Due to symmetrical nature of the design, the FSS is insensitive to variations of RF incidence angle for 90º (degree) rotations of the FSS. Simulated theoretical investigations are done by Ansoft Designer® software. Experimental investigation is performed using standard microwave test bench.Resumo em Inglês:
In this paper a truncated corner rectangular microstrip antenna (TCRMA) is analyzed in the presence of carbon fiber composite (CFC) material. Simplified carbon fiber composite models are proposed and the analyses are performed by the electromagnetic simulator Computer Simulation Technologies (CST). Theoretical and experimental results of return loss, axial ratio, input impedance and radiation pattern for the antenna located on the aluminum and CFC plates are presented and compared. The results show that the proposed models can be used as a good approximation of the CFC sample and that the CFC material is a feasible alternative instead of aluminum for antenna applications on complex structures such as ships or airplanes.Resumo em Inglês:
This research aims to study the effect of the modification in the Building Block Shape (BBS) on the frequency response of Sierpinski three dimensional pre-fractal antenna using conventional circuit analysis. Three different shapes of BBS's are used to build the antenna. The surface current is analyzed and compared for every BBS. A simple model was devised using the nodal analysis to provide an iterative method for calculating the distribution of currents and voltages for the antenna at every node. The antennas parameters such as Y-parameter, Input Return Loss (IRL), delivered power and surface current are investigated at the first and third tuning frequencies to enhance the perspective of the BBS effect.Resumo em Inglês:
We present experimental results concerning a new alloptical technique that multiplexes two binary signals into a quaternary one (4-ASK). The technique is based on parametric amplification. Values of the quaternary levels obtained experimentally, as a function of the extinction ratios of the binary input signals, show a rather good agreement with the simulated and the analytical results. The generated 4-ASK signals were propagated through 75 km of standard single-mode fiber and experienced eye penalties of only 0.5 dB. This indicates the robustness of the technique for practical applications in metropolitan area networks.Resumo em Inglês:
An L-strip proximity coupled circular microstrip antenna is proposed. The structure is investigated using circuit theoretic approach and simulated using IE3D simulation software. The patch is designed on a thick substrate of thickness of 11 mm for a design frequency of 3.74 GHz and provides ultra wide band operation. The numerical results for input impedance, VSWR, radiation pattern, efficiency and gain are presented. Bandwidth is found to be dependent on length of horizontal part of L-strip. A bandwidth of 69.52% is achieved (for VSWR<2) for y0=0.112λ0 and h2=0.097λ0. The beam of antenna rotates with operating frequency.Resumo em Inglês:
Optimization of design parameters based on electromagnetic simulation of microwave circuits is a timeconsuming and iterative procedure. To provide a fast and accurate frequency response for a given case study, this paper employs a neural network modelling approach. First, one of the case study's outputs, i.e., scattering parameter (|S21|) in dB, is predicted using a neural network model. Then the particle swarm optimization is employed to optimize the design parameters. The proposed method in designing the filter compares with two others methods for a case study. The simulation results show the capability of the proposed method in designing an optimized filter in a proper time.Resumo em Inglês:
This paper describes a model for the analysis of multilay-ered chiral structures containing planar electric and magnetic scattering elements of arbitrary shape, illuminated by an elliptically polarized plane wave. The particular case of a single chiral layer is analyzed and the scattering matrices for single and dual electric and/or magnetic dipole distributions are derived in an original way. As an application, the polarimetric response of a short electric or magnetic dipole is directly obtained from their scattering matrix.