Abstract This research provides detailed examination of the peak spatial Specific Absorption Rate (psSAR) in different age students in a classroom with wireless computers. This is motivated by the escalating inclusion of electronic devices in educational settings and the necessity to estimate the implications of this on the overall radio-frequency exposure. Two classrooms with posable realistic human models are simulated. One filled with several 7 years old children and another with several 43 years old adult, each using a laptop. The 1 g and 10 g psSAR are calculated for the head, back and hands. The distances between students are varied and the results compared to one student alone. A small free distance between rows (10 cm) produces significant reduction in psSAR (around 13 dB). Results are less sensitives to changes in lateral distance. While the maximum simulated psSAR values are below the recommended limits, it is observed that, in some classroom arrangements, the psSAR can be substantially increased (e.g., up to 26 dB in the back) comparing to just one student with his laptop. One objective of this study is to provide guidelines for the design of safer classrooms in the context of widespread laptop usage.

Abstract Space-fed array comprising of E-shape or U-slot cut rectangular microstrip antennas using the modified feed designs are proposed for higher gain and wider bandwidth. Modified feed optimally illuminates the edge space-fed elements to achieve a maximum gain. Amongst the two space-fed array variations, 7 x 7 E-shape space-fed array, excited using the feed comprising of gap-coupled and stacked E-shape patches provides bandwidth and gain of 2.085 GHz (48.97%) and 18.5 dBi, respectively. The antenna exhibits broadside radiation pattern across the complete bandwidth. An experimental validation has been carried out for the simulated results that show a close agreement.

Abstract In this study, we propose a novel biosensor based on a hexagonal-shaped microcavity with two slot waveguides within a two-dimensional photonic crystal. The biosensor aims to detect various blood components by utilizing a refractive index measurement. The device operates in the TM-polarized light wavelength range of 1150-1880 nm. It consists of two slot waveguides coupled with a hexagonal-shaped microcavity, formed by removing seven lattice holes. The microcavity is separated from the waveguides by two holes. When the analyte infiltrates the cavity, it induces a change in refractive index, leading to a wavelength shift at the output terminal. The proposed design achieves a high sensitivity of over 687.496 nm/RIU. The simulation of the proposed design is performed using both the Plane Wave Expansion (PWE) method and the Finite-Difference Time-Domain (FDTD) algorithm. The results demonstrate that the slot waveguide configuration provides excellent transmission.

Abstract Wider bandwidth microstrip antenna employing resonant slot require substrate thickness in excess of 0.07λg, which increases the antenna volume. In this paper, a novel technique to increase the bandwidth in E-shape microstrip antenna fabricated on a thinner microwave substrate, while employing printed resonator elements is proposed. The printed resonator positioned below the patch, introduces TM20 mode nearer to the TM10 mode in E-shape antenna that increases the bandwidth. On substrate thickness of 0.037λg, optimum design achieves bandwidth of 130 MHz (13.89%), with a broadside radiation pattern and peak gain of 7.8 dBi. With the obtained antenna characteristics, proposed thinner substrate designs will find applications in GSM band.

Abstract In our study, we conducted a thorough analysis of the spectral characteristics of a D-shaped surface plasmon resonance (SPR) photonic crystal fiber (PCF) refractive index sensor, incorporating a full width at half maximum (FWHM) analysis. We explored four distinct plasmonic materials-silver (Ag), gold (Au), Ga-doped zinc oxide (GZO), and an Ag-nanowire metamaterial-to understand their impact on sensor performance. Our investigation encompassed a comprehensive theoretical modeling and analysis, aiming to unravel the intricate relationship between material composition, sensor geometry, and spectral response. By scrutinizing the sensing properties offered by each material, we laid the groundwork for designing multiplasmonic resonance sensors. Our findings provide valuable insights into how different materials can be harnessed to tailor SPR sensing platforms for diverse applications and environmental conditions, fostering the development of advanced and adaptable detection systems. This research not only advances our understanding of the fundamental principles governing SPR sensor performance but also underscores the potential for leveraging varied plasmonic materials to engineer bespoke sensing solutions optimized for specific requirements and performance metrics.

Abstract This paper presents a reflectarray antenna with an innovative dielectric mirror in the form of a discretized concave reflector. The mirror, manufactured via 3D printing, combines dielectric and air layers, forming an Electromagnetic Band Gap (EBG) that reflects signals to the reflectarray feed antenna within its operating frequency band. A transmission line model was used for EBG parametric analysis, resulting in a simple, fast, and efficient design tool implemented in Octave. A design technique was developed to optimize the position and tilt of each mirror element, aligning reflected signal phases for constructive addition in the antenna's main beam direction. An Octave code implemented this design technique. Additionally, a Python program automated the generation of the dielectric reflector simulation model for Ansys HFSS. A reflectarray antenna is designed to operate in the 10.7 GHz to 12.7 GHz band, using a Yagi-Uda feed and a dielectric reflector made of PLA and air layers. The reflectarray antenna was manufactured and characterized, demonstrating a gain of 19.56 dBi and a half-power beam width of 8.04 degrees at 11.7 GHz at 〖θ〗_0=23° and 〖φ〗_0=0°. Good agreement was obtained between simulated and measured results, validating the design procedure.

Abstract In this paper, we present a novel numerical model for simulating partial discharges (PDs) transient currents excited by high-voltage DC (HVDC) systems. The model is based on the telegraph equations, which are solved in the time domain via the finite-difference method (FDM). With the proposed model, one can simulate air ionization through its distinct phases based on the electric field’s magnitude. This study specifically provides effective electrical conductivity of ionized air over time and space, calculated in the discharge channel also as a function of voltage and gap distance in a needle-plate setup. Validation is performed against experimental results from our laboratory experiments, demonstrating agreement despite the model’s one-dimensional nature. The simplicity of the model leads to much smaller simulation times (up to two minutes) compared to more complex three-dimensional models (typically requiring hours to complete), highlighting its potential for efficient PD analysis and future developments of general PD models based on effective plasma conductivity.

Abstract This article describes a two-element antenna designed in a Digital Terrestrial Television Broadcasting (DTTB) Multiple Input Multiple Output (MIMO) 2×2 front antenna in the 470 to 700 MHz band. It is based on a planar, canonical, fat-dipole element with low-cost and robust characteristics. Both antenna elements are fed directly by a coaxial connector, without a balun, and have been optimized to provide low coupling, improving their combined diversity gain. The array occupies an area of 0.76λ2o x 0.51λ2o (907 cm2) at the center frequency wavelength. Measurements of the antennas in outdoor urban environments are presented with a technology proponent for the project, the Advanced Integrated Services Digital Broadcasting - Terrestrial (ISDB-T), in 8 urban sites in Rio de Janeiro, Brazil. The results showed that the proposed MIMO 2×2 antenna operates effectively in outdoor applications, is robust, has a low development cost, and has a low degree of mutual coupling.

Abstract Elastic optical networks (EONs) have characteristics that meet the growing demand for current and future bandwidth, such as 5G and Internet of Things. In EONs, connections must have a route and a spectrum slice available between the nodes to establish communication. The process associated with this task is named routing and spectrum allocation (RSA) problem. The RSA problem is NP-hard and several approaches have been proposed in the literature using computational intelligence (CI). This paper provides a systematic literature review (SLR) regarding applying CI to solve the RSA problem in EONs. We offer a research roadmap encouraging the community to address identified limitations and open questions requiring further investigation. This study selects 40 primary studies for analysis and data extraction out of the 659 initially obtained papers. The main conclusions indicate that the community still needs to explore the RSA problem with the freedom to solve it without considering a fixed order of the two subproblems: routing and spectrum allocation. The studies reveal that efficient solutions are achieved with the techniques used in the RSA problem, which made them excellent tools. Furthermore, this SLR presents a set of open questions, suggesting valuable topics for future research through a research guide.

Abstract This article explores the performance of a Yagi-Uda patch antenna with Koch fractal geometry of different orders on an FR-4 substrate. It exhibits multiband operation, enabling the use across multiple frequency bands. The proposed reflector features equally spaced slots. The radiating dipole element has a Koch fractal geometry of order 2, while the third directive element of the antenna is shaped as a Koch fractal of order 1. The antenna was designed and simulated using CST Studio® from 1 GHz to 10 GHz. After fabrication, measurements with a vector network analyzer (VNA) verified the presence of 11 operational bands with resonance frequencies centered at 1.265 GHz, 1.545 GHz 2.59 GHz, 2.7 GHz, 3.05 GHz, 3.9 GHz, 5 GHz, 5.18 GHz, 5.71 GHz, 6.20 GHz, and 8.72 GHz. It results in an aggregate bandwidth of 652 MHz (Ultra-Wideband, UWB) with applications in a range of protocols and technologies. The antenna dimensions are only 100 mm x 120 mm, resulting in a compact size.