Volumen 71 (2020): Heft 5 (September 2020)

In this article the design and implementation of dual band circularly polarized antenna which is backed with AMC is presented. The proposed antenna consists of a novel heart shaped concentric ringshaped patch attached to meander line. The dimension of the antenna without AMC is 0.24 λ₀ × 0.140 λ₀ × 0.012 λ₀ × and with AMC 0.43 λ₀ × 0.43 λ₀ × 0.32 λ₀ and designed on a commercial FR4 substrate. The antenna gets worked at dual band applications such as 2.4 GHz (wi-fi) operates from 2.3 GHz to 2.5 GHz and 5.2 GHz (WLAN) operates from 4.7 GHz to 5.9 GHz and also gets circular polarization from 2.3 GHz to 2.5 GHz (200 MHz) and 4.95 GHz to 5.40 GHz (450 MHz) is achieved. In this article the proposed model is investigated towards circular polarization, radiation patterns and current distributions by varying parametric analysis is carried to analyze overall performance of antenna with and without AMC.

Three-dimensional body scanning systems are increasingly used in sensitive public areas such as airports. By providing a high resolution image of a person from all sides, it is possible to detect potential metallic, ceramic and explosive threats. For these systems, it is essential to design broadband antennas with a fan beam, highly directional radiation in one plane and wide in the other plane, and characterized by phase center stability as a function of frequency. In this paper, the planar lateral wave antenna (LWA) array is proposed to achieve these radiation requirements. The LWA has two critical shortcomings: the flaring part and the dielectric matching layers (MLs), to operate over very broad frequency bands. In this work, these shortcomings are overcomed by forming a connected array of planar LWAs to improve broadband performance and by applying necessary perforations on the dense dielectric lens antenna to create different effective relative permittivity regions. An eight element connected and perforated LWA array is designed to operate in the 8–24 GHz frequency band. The drilled holes are proved to play a similar critical role of MLs in internal reflection suppression. The results emphasize all crucial demands for body scanning systems.

This paper deals with the integration of polarization multiplexed 16-ary quadrature amplitude modulation format in optical metropolitan networks enhanced with the signal amplification. Before expensive experimental setup or practical testing and demonstration, we prefer creating of appropriate simulation platform for the optical transmission system. A novelty can be found in adjusting, optimizing and construction of the proposed optical system and functional parts for any modulation format used. So, such simulation platform is first introduced along with possibilities for numerical simulations of its optical components - laser and amplifier. By this way, essential noise tolerances for comparison with the data under real conditions are included. Subsequently, there are characterized implementations of terminal devices in detail with a possibility for upgrading to the dual-polarization mode operation. Finally, simulation results from the simulation platform are presented and a discussion about demands for effective exploitation of the polarization multiplexed 16-ary quadrature amplitude modulation in enhanced optical metropolitan networks concludes our contribution.

Signal periodic decomposition and periodic estimation are two crucial problems in the signal processing domain. Due to its significance, the applications have been extended to fields like periodic sequence analysis of biomolecules, stock market predictions, speech signal processing, and musical pitch analysis. The recently proposed Ramanujan sums (RS) based transforms are very useful in analysing the periodicity of signals. This paper proposes a method for periodicity detection of signals with multiple periods based on autocorrelation and Ramanujan subspace projection with low computational complexity. The proposed method is compared with other signal periodicity detection methods and the results show that the proposed method detects the signal period correctly in less time.

Compared with conventional methods for insulation performance evaluation of power cables, the oscillating wave test system used in partial discharge measurement for power cables has advantages of high integrity, easy operation, low power consumption, and compact size in addition, partial discharge, defect localization, and dielectric loss can be measured simultaneously without any damage to cable insulation. Therefore, the oscillating wave test system has been widely applied for insulation performance evaluation of newly installed as well as fault power cables. However, there is no study so far on the verification method of oscillating wave test system. This paper dealt with the application and verification for cable partial discharge measurement devices based on oscillating wave voltage, which is aimed to verify performances of oscillating wave voltage generator, partial discharge measurement, and partial discharge localization. The proposed verification system is expected to be applied in the admittance testing and regular verification of oscillating wave test system, for the purpose of improving the its accuracy and standardization in partial discharge measurement of power cable.

A new approach for studying the performance of single-mode optical fiber surface plasmon resonance sensor for refractive index sensing is presented. Intensity interrogation technique is used to observe and examine the effect of changing the value of the operating wavelength, within the single-mode operation region, on sensor performance. Effect of changing metal thickness, which is a critical parameter of the sensor structure, is also investigated. The results show that the selected operating wavelength within the mentioned region plays a very important role and has a significant impact on the sensor sensitivity. As the operating wavelength increases beyond the cut-off wavelength, above which the first higher-order mode disappears, the sensitivity increases while the refractive index range, for which the sensitivity is above its half maximum value, becomes narrower. In the proposed sensor structure, for a metal thickness of 25 nm, the maximum sensitivity reaches 2554 RIU⁻¹ for analyte refractive index of 1.439 at a wavelength of 1500 nm. This sensitivity corresponds to a resolution of order 10⁶ RIU by assuming 1% minimum reflectivity variation. The operating wavelength should be carefully selected and changed according to the refractive index values intended to be measured to ensure high sensor sensitivity at these values. The analysis provided in this paper enables to select and change the desired range of the sensed refractive index using low cost technique by just changing the operating wavelength in the single-mode operation region.

In the paper, a practical design of a Ku-band Vivaldi antenna array for compact radar system is presented. The realized gain, the beam width, polarization purity and the possible electronic beamforming in the horizontal plane were the most important requirements. Since the array was requested to show an enhanced mechanical stability, a novel geometry of elements was proposed. The Vivaldi slot was created on two substrates connected by metallic vias suppressing surface currents, and the microstrip feeder was placed in-between those substrates. Simulations are based on special approach in CST Microwave using infinite array of antenna elements, which should reduce computing time.

This paper presents the design and optimization of 1 × 2^N Y-branch optical splitters for telecom applications. A waveguide channel profile, used in the splitter design, is based on a standard silica-on-silicon material platform except for the lengths of the used Y-branches, design parameters such as port pitch between the waveguides and simulation parameters for all splitters were considered fixed. For every Y-branch splitter, insertion loss, non-uniformity, and background crosstalk are calculated. According to the minimum insertion loss and minimum non-uniformity, the optimum length for each Y-branch is determined. Finally, the individual Y-branches are cascade joined to design various Y-branch optical splitters, from 1 × 2 to 1 × 64.

Nanofluidic devices with two-dimensional nanochannels have many applications in biology and chemistry, however, it is still a challenge to develop a low-cost and simple method for fabricating nano-masks that can be used to produce two-dimensional nanochannels. In this paper, a novel low-cost and simple method, based on UV lithography and oxygen plasma, was proposed to fabricate nano-mask. The influence of exposure time on the photoresist mesas was investigated in the ultraviolet lithography process. The parameters of RF power and treatment time on the width reduction of photoresist mesas were analyzed by the oxygen plasma. In our work, in order to increase the efficiency controllability of photoresist removal, a RF power of 90 W, a pressure of oxygen plasma 60 Pa, and the time division method were adopted to remove photoresist by oxygen plasma. Finally, nano-patterns of photoresist mesas with bottom width of 330 nm were successfully fabricated. The proposed method provides a low-cost way to produce high-throughput two-dimensional nanochannels.

In IEEE 80211 wireless LANs, hidden nodes can disrupt the backoff algorithm of other nodes that are located outside the physical carrier sensing range of hidden nodes. The fairness problem between the nodes that are vulnerable and not vulnerable to the hidden node problem is dealt with in this paper. We propose an efficient fair MAC protocol to resolve the fairness problem.