Journal of Microwaves, Optoelectronics and Electromagnetic Applications, Volume: 14, Issue: 2, Published: 2015
  • Phase Noise Effects on Wideband Mobile Radio Channel Sounding Articles

    Ferreira, Carlos Eduardo Salles; Siqueira, Gláucio Lima; Sampaio, Raimundo

    Abstract in English:

    Abstract In this work three wideband mobile radio channel sounding methods are simulated and compared using computational tools. The considered sounders include the traditional STDCC and two other proposed sounding methods that are based on OFDM digital transmission and detection procedures and on matched filtering. The impact of the phase noise introduced by the receiver local oscillator in the precision of the examined sounders is analyzed by comparing the estimated channel results with the simulated reference channel. Other impairments factors like thermal noise or nonlinear distortion affecting the system are not considered.
  • Design of K-Band Substrate Integrated Waveguide Band-Pass Filter with High Rejection Articles

    Rhbanou, Ahmed; Sabbane, Mohamed; Bri, Seddik

    Abstract in English:

    Abstract This article presents the design of K-band Substrate Integrated Waveguide (SIW) Band-pass filter with high rejection, by using the topology with iris and the SIW resonators. The simulated results of this filter have shown that the passband is from 17.3 GHz to 19.3 GHz, while the insertion loss is 1.35 dB within 10.9 % bandwidth around 18.3 GHz and input return loss in the passband is better than 15 dB, with high rejection of -57.88 dB at the frequency 24.07 GH. All the structures are designed on a single substrate of Rogers R04003 permittivity 3.55. The compatibility with planar circuits is provided via a specific microstrip transition (microstrip tapered transitions).
  • Chromatic Dispersion of an Optical Fiber Based on Photonic Quasicrystals with Twelve-Fold Symmetry and its Application as Directional Coupling Articles

    Guimarães, Ádller de O.; Silva, José P. da; Dantas, Emmanuel R. M.

    Abstract in English:

    Abstract Optical fibers composed by photonic quasicrystals it is based on aperiodic structures characterized by at least two different symmetrical patterns from the base matrix. In this work, an optical fiber composed by quasi-periodic and symmetric matrix was analyzed using the finite element method in conjunction with cylindrical perfectly matched layers. The structure is composed by pure silica and/or silica doped with germanium, and originated from twelve distributions of air holes symmetrically with a defect caused by the absence of the fiber central hole. The obtained results shown that the structure in analysis exhibits an ultra-flat chromatic dispersion for a range of wavelengths varying from 1.4 to 1.6 µm covering the bands E,S, C and L, with chromatic dispersion, for the silica doped with germanium, varying between 22.1 and 23.01 [ps.km-1.nm-1]. This photonic quasicrystal fiber (PQCF) was used to form a coupler with three identical horizontal cores surrounded by air holes. The signal power launched in the central core is equally divided between the two neighboring cores with 50% of the coupling ratio.
  • Design of a Triple Band-notched UWB Planar Monopole Antenna Articles

    Tomar, Sanjiv; Kumar, Ajay

    Abstract in English:

    Abstract In this paper, a novel design of a compact planar ultra wide band (UWB) monopole antenna with triple band notched characteristics has been presented. The antenna has a unique shape and has been fed through a 50 Ω microstrip feedline. The strength of the antenna lies in three band notched properties for WiMax system at 3.3 - 3.7 GHz, WLAN IEEE 802.11a at 5.15 - 5.85 GHz and X band satellite communication at 7.25 - 8.395 GHz. The notched bands have been achieved by incorporating an inverted U-slot etched on the radiator patch, an inverted C-slot also on the radiator patch and a U-slot on the microstrip feed line. In order to achieve FCC defined impedance bandwidth of 7.5 GHz, a rectangular cut in the ground plane has been introduced along with staircase structure in the bottom edge of the radiator. The proposed antenna is having a compact size of 30 X 30 X 1.6 mm3 and exhibits a large bandwidth from 2.8 GHz to 10.7 GHz. The antenna has been successfully simulated and fabricated. The radiation pattern is omni-directional in H-plane and the E-plane exhibits dipole like radiation pattern. The gain of the antenna is stable across the whole operating frequency band except at three notched bands.
  • Analysis and Comparison of Sensors for Measurements of Partial Discharges in Hydrogenerator Stator Windings Articles

    Dmitriev, Victor; Oliveira, Rodrigo M. S. de; Brasil, Fernando S.; Vilhena, Paulo R. M. de; Modesto, Jonathas F. M.; Zampolo, Ronaldo F.

    Abstract in English:

    Abstract In order to measure electrical signals produced by partial discharges in hydrogenerators stator windings, capacitive couplers are regularly used. They are electrically connected to the windings and therefore, require undesired insulation intrusion. For avoiding such an intrusion, a microstrip directional coupler is used, which is experimentally and numerically investigated in this work. This electromagnetic field sensor is analyzed initially via computer simulation using the finite-difference time-domain method. This numerical analysis is fulfilled considering the coupler placed over a stator bar. Experimental high-voltage tests with generator windings were also performed. We compare the results of the measurements obtained by using various sensors and show that the microstrip directional coupler has some important advantages over traditional capacitive sensors such as complete conductive insulation from the windings and the capacity of detecting shorter PD pulses due to their wider bandwidth.
  • Design of Frequency Selective Band Stop Shield Using Analytical Method Articles

    Fallah, Mahmoud; Ghayekhloo, Alireza; Abdolali, Ali

    Abstract in English:

    Abstract In this article, a high-order frequency selective band-stop EMC (electromagnetic compatibility) shield is designed using multilayer square loop while each loop resonates at the specific desired frequency. The glass material is picked out as the preferred substrate for the designing process. In contrast to the computationally intensive numerical approaches (software), the equivalent circuit model offers a simple alternative method in FSS (frequency selective surface) analyses which is useful for quickly predicting the performance of FSS. The proposed FSS can be synthesized based on microwave filter theory and the synthesized FSS can control transmission-zero frequencies. A three zero-transmission transparent window is designed using the proposed method, in which 30dB insertion loss is achieved for 6 to 10 GHz bandwidth and optical opacity of the structure is 85%. The response of the analytical model is compared with the results of full-wave simulation. As a result, it predicts quite well the resonant frequencies of the designed FSS.
  • Artificial Immune Network Design of Optical Multiplexers/Demultiplexers Articles

    Silva-Santos, Carlos H.; Rodríguez-Esquerre, Vitaly F.; Hernández-Figueroa, Hugo E.

    Abstract in English:

    Abstract An efficient design approach of directional couplers based multiplexers/demultiplexers for optical communication applications, by using an adapted artificial immune network algorithm for optimization (opt-AiNet), is presented and validated by using the beam propagation method. Two key multiplexers/demultiplexers based on planar waveguides and optical fiber, directional couplers, have been optimized in order to validate the efficiency and usefulness of the opt-AiNet.
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