Resumo em Inglês:

Abstract This article presents the theoretical analysis of a signal coupling between a proposed Photonic Crystal Fiber (PCF) and a Conventional Fiber with Step Index (CFSI) system. In this analysis, the Finite Element Method (FEM) and Beam Propagation Method (BPM) are applied together with Daubechies wavelets as basis function and described in the mathematical formulation. The simulations were performed casting the PCF signal into CFSI core using the PCF refractive index. For simulation purposes, the cladding material refractive index was set as 1.5% lower than the core index. The application of Daubechies wavelets as basis functions in BPM analysis presented insertion loss around 3.8% during the fiber coupling.

Resumo em Inglês:

Abstract Microwave pulse bursts were obtained through optical domain intensity modulated microwave carriers, sliced by cascaded modulator technique, followed by non-linear semiconductor optical amplifier (SOA) pre-chirp. After 3 to 18 km of buried fiber propagation and photo detection, the microwave signals presented increased extinction ratio, up to 36 GHz, with pulse modulation windows from 166 to 1000 picoseconds, achieving rise times near to 10 ps.

Resumo em Inglês:

Abstract This paper describes the analysis of the effects of a frequency selective surface (FSS) on the characteristics of a microstrip line fed antenna with a bow-tie slot in the ground plane for operation in the frequency range 1 to 10 GHz. The use of the FSS is proposed to miniaturize the antenna structure and increase the number of resonance frequencies and the gain. Air gaps can be inserted between the antenna and the FSS to allow for the adjustment of the resonance frequencies and increase the bandwidth. To prove the concept, antenna prototypes printed on a 30×30 mm2 FR4 low-cost substrate are designed, fabricated and tested. Good agreement is obtained between numerical simulations and experimental results, thus validating the proposed design procedure. The obtained miniaturization and multiband effects can be most convenient for multiservice wireless system applications such as WLAN, WiMAX, 4G, and 5G mobile communication systems.

Resumo em Inglês:

Abstract In this paper, a microstrip patch antenna (MPA) design was developed to verify the performance of a metamaterial cell array (MTM) Capacitive Loaded Loop (CLL) immersed in the substrate. The metamaterial was obtained from metal laminates designed inside a dielectric material, with dimensions carefully calculated to have the effective negative permittivity and permeability, consequently the negative refractive index, in a certain frequency range. In this case, the geometric control of the unit cell parameters allowed its organization in a periodic arrangement to be immersed in the MPA substrate. Simulated and experimental results were obtained and compared for some parameters of the antenna, which showed a good relationship between MTM and MPA performance.

Resumo em Inglês:

Abstract Wideband, dual sense circularly polarized (CP), asymmetric circular slot fed by coplanar waveguide is proposed and designed. Dual polarizations are obtained by using a horizontal stub to the feed line and embedding the L-shaped strip onto the slotted ground plane. The simulated result of impedance bandwidth shows wideband performance is produced by four resonant modes. Some key parameters are studied to analyze the characteristics of the proposed antenna. The overall volume of the proposed antenna is 18 mm × 18 mm × 1.6 mm. The measured value of 10 dB impedance bandwidth is 112%at frequencies from 4.2 GHz to 14.9 GHz with voltage standing wave ratio (VSWR) ≤ 2. The 3-dB axial ratio bandwidths are 39.3% for the lower band which senses right-hand circular polarization (RHCP) and 2.8% for the upper band which senses left-hand circular polarization (LHCP) relative to the center frequency of 6.1GHz and 14.1 GHz, respectively. The proposed structure gives a good radiation pattern with moderate gain.

Resumo em Inglês:

Abstract This paper presents a patch antenna array topology for Simultaneous Wireless Information and Power Transfer (SWIPT) applications. The resulting Double Patch Antenna Array (DPA) is composed of two patch antennas operating at different frequencies and fabricated on a unique substrate. One of the patches operates at the 1.8 GHz mobile communication band and is used for wireless communication, while the other one operates at the 2.4 GHz Industrial, Scientific, and Medical (ISM) band, and is used for Radio Frequency Energy Harvesting (RFEH). The analyzes and measurements carried out have shown that the adopted topology has satisfactory performance for communication, with a gain of 1.5 dBi, and for out-of-band energy harvesting, with a Vout of 160 mV at 2.45 GHz. These results indicate this approach as a promising strategy for low-power wireless applications.

Resumo em Inglês:

Abstract In this work, a compact ultra-wide-band microstrip antenna loaded with C-shaped parasitic elements, for Digital Video Broadcasting - Terrestrial (DVB-T) and LTE 450 / 700 signal reception, is designed and presented. The proposed antenna is named “HI Monopole”, and its geometry has been designed to be simple, lightweight, and compact. Fabrication process is inexpensive and suitable for electronic gadgets. The HI Monopole operates with ultra-wide bandwidth characteristics, encompassing Digital Video Broadcasting - Terrestrial (DVB-T) standard (470-890 MHz), LTE-450 and LTE-700 bands. This feature has been accomplished by inserting an indent in its ground plane, adjusting dimensions of the feeding line, and adding two C-shaped parasite elements onto the region posterior to the antenna's main radiating element. It was verified via electromagnetic measuring that this device is capable of covering the 429-1022 MHz range. Hence, its total bandwidth is 593 MHz. The superior and inferior cutoff frequencies have been defined using the -10 dB return loss reference level. Therefore, the proposed antenna can be employed for receiving DTV and LTE signals broadcasted in any country, independently of its adopted standard.

Resumo em Inglês:

Abstract Continuous inverse class-F (CICF) is a recent mode of harmonically-tuned RF power amplifiers used to extend the operating bandwidth of the conventional narrowband class-F−1 power amplifier by producing variable set of drain current waveforms and load admittances that give the same operating efficiency. In this work, a new approach of analysis is developed by suggesting some modified drain current waveforms and comparing the resulting theoretical performance characteristics such as drain efficiency and output RF power with the conventional type. It has been shown that the drain current with a truncated square wave shape can better model the actual behavior of the power amplifier, delivering a theoretical efficiency higher by about 8% than the conventional shape. Besides, a simple analytic technique for extracting the device harmonic load impedances for the desired band is also presented. Based on the theoretical analysis, a 6 W power amplifier circuit was designed and simulated to operate within the frequency band 800 – 1000 MHz. Simulation results indicated that a drain efficiency of values between 82% and 86% was obtained across the specified band.

Resumo em Inglês:

Abstract In this paper a 2-4 GHz microstrip IFM (Instantaneous Frequency Measurement) subsystem that uses Wilkinson power dividers, frequency discriminators based on band-stop filters and a DC arduino section is reported. The device uses band-stop filters as an alternative to delay lines, commonly used for IFM. The resonators are responsible for frequency adjustment, according to half guided wavelength resonator length, and the distance between the transmission line and the resonator. A fully micro-controlled 125 MHz resolution IFM subsystem is designed and tested. Results of the IFM subsystem composed by filters, 4-way power dividers and an Arduino board are described.

Resumo em Inglês:

Abstract Electromagnetic (EM) waves do not travel in straight lines in the troposphere due to refraction. This leads to errors in many engineering applications. In order to correct these errors, a numerical solution based on the difference method has been proposed, which can reveal the degree of EM wave bending owing to atmospheric refraction, moreover, it can predict the actual path of the EM wave propagating in the troposphere. The error of the numerical method is studied here, which reveals the source of the error. Based on this, two improvement methods are proposed. The computational accuracy of the numerical methods is verified by comparison with the analytical solution. The proposed method ensures the computational efficiency and accuracy of the problem of refraction of EM waves in the troposphere.

Resumo em Inglês:

Abstract A modeling of the resonant behavior of a continuously reconfigurable frequency selective surface, FSS, is described in this paper. The FSS is based on four arms star geometry and its reconfigurability is achieved by the use of varactors. FSS, four arms star geometry and varactor principles are explained. Considering available a set of measured or numerical data, with frequency responses for different varactor capacitance values, the FSS equivalent circuit is stablished. Then, the varactor capacitance effect is included and the resonant behavior can be easily determined. After stablished, the FSS equivalent circuit can be applied even for a different varactor. In order to validate the proposed modeling, the equivalent circuit of a reconfigurable FSS using the varactor SMV1231 (0.466 pF ≤ Cv ≤ 2.35 pF is obtained. The equivalent circuit results are compared to numerical (ANSYS) and measured results, verifying a good agreement. Following, for the same geometry, the equivalent circuit is applied to a reconfigurable FSS using the SMV1234 varactor (1.32 pF ≤ Cv ≤ 9.63 pF) and once more a good agreement between the results is observed, indicating the applicability of the proposed modeling, which is especially attractive for optimization process.