Scielo RSS <![CDATA[Journal of Microwaves, Optoelectronics and Electromagnetic Applications]]> http://www.scielo.br/rss.php?pid=2179-107420160002&lang=pt vol. 15 num. 2 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Design of a Microstrip Diplexer and Triplexer Using Open Loop Resonators]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200065&lng=pt&nrm=iso&tlng=pt Abstract In this paper a novel design of microstrip diplexer and triplexer using open loop resonators is presented. The proposed diplexer if formed by two band-pass filters for the Industrial Scientific Medical (ISM) applications at 5.8 GHz and the WIMAX applications (IEEE 802.16 WiMAX at 3.17 GHz to 4.2 GHz bands). The microstrip triplexer is designed for the Digital Communication System (DCS) at 1.8 GHz, WIMAX at 3.2 GHz and for the C-band at 4.4 GHz. Each device is formed by a set of filters with a matching network by using open loop resonators and a good arrangement of the transmission feed lines. Several parametric studies were achieved to study the influence of some critical parameters on the performances of the proposed circuits. The LC equivalent circuit of the band pass filter is examined and the values of its components are calculated. ADS Agilent and CST-MWS solvers are used to predict the electrical performances of the proposed circuits. The simulated frequency responses of these structures show good results with insertion losses around 2 dB, return losses better than 20 dB for all channels, and an isolation between all bands better than 20 dB. Besides, several transmission zeros are observed near the pass bands which enhance the selectivity and the isolation of the proposed devices. <![CDATA[The Smart Grid Concept in Oil & Gas Industries by a Field Trial of Data Communication in MV Power Lines]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200081&lng=pt&nrm=iso&tlng=pt Abstract Nowadays, communication and networking technologies are essential for Oil &amp; Gas industries in order to guarantee reliability, safety and low costs in the producing process. Information access and commands and set-points transmission from/to automation systems are challenging tasks mainly due to distributed production areas and hostile environments. This paper presents a field trial of broadband power line communication over an overhead medium voltage grid as a data transport employing 200 Mb/s BPL modems. Throughput, frequency response, physical speed and latency are some of the investigated network parameters. Experimental results obtained after propagation through 1.63 km of a multipath MV power grid reveal the viability of the BPL technology as an access network for video and automation data transport in onshore Oil &amp; Gas industries. <![CDATA[Design of high gain and wide band EBG resonator antenna with dual layers of same dielectric superstrate at X-bands]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200093&lng=pt&nrm=iso&tlng=pt Abstract A wide band EBG resonator antenna with two layer of dielectric superstrates of the same material is design which is operating in X band. The EBG superstrates act as Partially Reflective Surfaces (PRS) having positive reflection phase curve which are suspended above a double sided dipole patch antenna fed by a coaxial cable pass through ground plane. Thus a resonator cavity is constructed which increases the bandwidth and gain of the feed antenna. The measured results validate the simulation results obtain from Computer Simulation Technology (CST) microwave studio. These results show that the antenna posses a 3 dB gain bandwidth from 8.5 GHz to 11.2 GHz, with a peak gain of 15.3 dBi. Furthermore, the scattering parameter S11 is well within range from 8.6 GHz to 11 GHz. <![CDATA[Signal Processing Technique for Time Domain Measurement of S-Parameters]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200105&lng=pt&nrm=iso&tlng=pt Abstract In this paper, a simple and accurate technique for the measurement of the S-Parameters of a two-port network from time domain data is presented, based on Fourier theory and techniques. This method is proposed to circumvent the need of a network analyser when studying an unknown device, as no additional measurements other than the time domain data are required. An excellent correspondence between this technique's results and regular network analyser measurements is achieved for the entire operational band of the devices tested. <![CDATA[Measured Dielectric Permittivity of Contaminated Sandy Soil at Microwave Frequency]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200115&lng=pt&nrm=iso&tlng=pt Abstract Measurement of dielectric permittivity of soil has been studied by many researchers. However, few studies have been conducted on contaminated soil. The motivation of the present study is to investigate the behavior of sandy soil contaminated by lubricant oil at microwave frequency. Two different artificially prepared soil samples are measured in the laboratory. The measurement of the complex permittivity of soil samples is reported in the frequency range 500 MHz – 4 GHz using open-ended coaxial probe technique. Measurements are carried out using a dielectric assessment system associated with an automatic network analyzer and a dielectric probe connected to a computer. The experimental set up is described and the system response is obtained. It is observed that the complex permittivity of the soil is associated with the contamination. The measurement results show that the change in the dielectric loss of dry sand before and after lubricant oil contamination is quite significant. Measuring these dielectric contrasts provide a basis for using ground-penetrating radar or other high-frequency electromagnetic sensors in the detection of soil contamination. <![CDATA[Statistical Evaluation of Measured Rain Attenuation in Tropical Climate and Comparison with Prediction Models]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200123&lng=pt&nrm=iso&tlng=pt Abstract Substantial modifications have been made to the expressions for calculating distance factor and extrapolation techniques in the latest ITU-R P.530-14. However, its performance has not been rigorously evaluated in the tropical and equatorial climates. In this article, the new ITU-R method and three prediction models are validated using measurement data from tropical Malaysian climate. The data were collected on six geographically spread terrestrial microwave DIGI MINI-LINKs operating at 15 GHz. When tested against measurements, the Da Silva Mello model yields a significant improvement for the prediction of rain attenuation distributions. The prediction errors observed in the ITU-R model suggest the need for more data campaign in the afore-mentioned climates. <![CDATA[Propagation Characteristics of Optical Long Period Fiber Gratings using Graphical Solution Methods]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200135&lng=pt&nrm=iso&tlng=pt Abstract In this paper, we explicitly show a complete analysis and detailed calculation of propagation characteristics of the effective refractive indices of the core and cladding for a long period grating employing both the Two-Layer and Three-Layer Geometries. The results are achieved employing graphical solution methods and presented in terms of the effective refractive indices of the core and cladding. Then, we compare the results with OptiGrating (Optiwave Systems Inc., Ottawa, Canada). Finally, we point the best model to evaluate the effective refractive indices, avoiding incorrect designs of the long period gratings. <![CDATA[Extracting Metamaterial Properties of Negative-Index and Plasmonic scatterers from the Mie Coefficients]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742016000200146&lng=pt&nrm=iso&tlng=pt Abstract An alternative theoretical approach is presented for improving the understanding of the scattering properties of simple negative-index and plasmonic spheres. The Mie scattering coefficients are broken up into two terms, the first representing the expected fields of a corresponding positive-index sphere, the second emerging from the intrinsic metamaterial nature of the scatterer. Some limiting cases are considered, e.g. dipole approximation), together with their circuital representation in terms of equivalent lumped elements. This formalism may be adopted, for example, in the evaluation of the particular internal and scattered electromagnetic field patterns observed for these particular classes of particles.