Resumo em Inglês:
This paper presents the design of notched-band antenna with CPW - feed. The notched - band has been achieved by using the W-shape slot in ground plane. The antenna has been simulated using a 3D - Electromagnetic simulator. The experimental results of proposed antenna exhibit ultra wideband characteristics from 2.0 - 15.0 GHz except the notched-band frequency from 5.0 - 6.0 GHz. The slot is optimized with respect to width, length and position for a detailed study of notched-band characteristics. It is observed that the centre frequency and bandwidth of notched-band depend on the length and width of slot respectively. The experimental radiation patterns of this antenna are omni-directional in H-plane and bidirectional in E-plane. This antenna can be useful for UWB system, medical imaging and vehicular radar.Resumo em Inglês:
Design and analysis of a 35 GHz metal photonic band gap (PBG) resonant cavity operating in the TE041-like mode has been presented. The dispersion characteristics of a 2D metal PBG structure comprising of triangular array of rods has been obtained using FDTD method. Global band gap regions have been obtained to be used for the PBG cavity design. A mode map has been also generated to examine the occurrence of the possible modes in the PBG cavity. Electromagnetic simulation of the designed PBG cavity has been performed to study the operating modes and quality factors. Role of the number of metal rods layers around the defect in PBG structure has also been illustrated for confining the desired mode and deciding the diffractive quality factor. PBG cavity results have been compared with the analogous cylindrical cavity for the designed mode along with the possible nearby modes to examine the mode competition. It has been found that the mode competition has been successfully reduced in designed PBG cavity and nearly a single mode operation is achieved. It is hoped that present study would be useful for the application of the metal PBG structures in the Gyrotron devices to alleviate the mode competition problem while operating in the higher order modes.Resumo em Inglês:
In this paper, we propose a spectral correlation-based technique for tracking the wavelength shift of a fiber Bragg grating. We compared this approach, by means of a Monte Carlo numerical simulation, to the typical peak tracking techniques applied in classic interrogation systems. As result, we obtained a considerable gain in terms of noise tolerance (about 20 dB), which can be further incremented by selecting large-bandwidth gratings. This permits to increase the power budget of a fiber Bragg grating interrogator without changing the optical layout, overcoming classical limitations of commercial and custom systems. Penalties due to the non-idealities have been evaluated through the same Monte Carlo approach. Finally, we discuss a practical application of the peak tracking techniques to a fiber Bragg grating-based weight sensor, in which we applied the spectral correlation to track both the Bragg wavelength position, spectral deformations due to high strain, and spectral non-linearity.Resumo em Inglês:
We present a microwave switchable frequency selective surface with high quality factor transmission resonance. The high quality resonance is achieved by excitation of the trapped-mode in array with two concentric metal rings in a cell on a silicon substrate. Optical activation of the silicon substrate permits to switch off the transmission band.Resumo em Inglês:
The femtocell concept aims to combine fixed-line broadband access with mobile telephony using the deployment of low-cost, low-power third and fourth generation base stations in the subscribers' homes. While the self-configuration of femtocells is a plus, it can limit the quality of service (QoS) for the users and reduce the efficiency of the network, based on outdated allocation parameters such as signal power level. To this end, this paper presents a proposal for optimized allocation of users on a co-channel macro-femto network, that enable self-configuration and public access, aiming to maximize the quality of service of applications and using more efficiently the available energy, seeking the concept of Green networking. Thus, when the user needs to connect to make a voice or a data call, the mobile phone has to decide which network to connect, using the information of number of connections, the QoS parameters (packet loss and throughput) and the signal power level of each network. For this purpose, the system is modeled as a Markov Decision Process, which is formulated to obtain an optimal policy that can be applied on the mobile phone. The policy created is flexible, allowing different analyzes, and adaptive to the specific characteristics defined by the telephone company. The results show that compared to traditional QoS approaches, the policy proposed here can improve energy efficiency by up to 10%.Resumo em Inglês:
An improved microwave method to extract the complex permittivity of solid and liquid materials filled in a short-circuited waveguide is developed. The method determines accurately the dielectric constant of thin and moderate thick samples. It eliminates the problems arising from any position offset of the dielectric slab in transmission / reflection methods. The proposed method is iterative and the initial value is calculated by using the 7th approximation order of trigonometric terms in the exact reflection coefficient equation. This approach is applied to the simulated data of low loss and dissipative materials in limited frequency band.Resumo em Inglês:
This paper presents a statistical modeling of rain attenuation in terrestrial links located in a tropical region using different types of distribution. Each distribution is tested against long-term statistics of data collected during up to two years of experimental measurements in links operating at 15 GHz. Statistics obtained from each distribution are tested against the corresponding ones derived from the experimental data using a test variable described in the ITU recommendation P.311-13 and an alternative test variable.Resumo em Inglês:
This paper presents an experimental comparative study of iron losses obtained by means of the Epstein frame, Ring Core and dynamometer tests with non-oriented electrical steel samples. The comparisons are qualitative and they are intended to show the importance of carrying out other tests to evaluate electrical steels in addition to the standard Epstein frame method. In industry, complex or costly tests are avoided, whenever it is possible. This study shows that the ring core test can be a low cost solution since it is effective. For the manufacturer point of view, comparing different commercial steels at purchase time with a simple process is an advantage.