Design of a Dual-Band On-Body Antenna for a Wireless Body Area Network Repeater System

A dual-band on-body antenna for a wireless body area network repeater system is proposed. The designed dual-band antenna has the maximum radiation directed toward the inside of the human body in the medical implantable communication service (MICS) band in order to collect vital information from the human body and directed toward the outside in the industrial, scientific, and medical (ISM) band to transmit that information to a monitoring system. In addition, the return loss property of the antenna is insensitive to human body effects by utilizing the epsilon negative zeroth-order resonance property

New Measurement Technique for Complex Permittivity in Millimeter-Wave Band Using Simple Rectangular Waveguide Adapters

This research presents a novel methodology for measuring the complex permittivity of a material under test (MUT) in a millimeter-wave (mmWave) band by using two rectangular waveguide adapters. Contrary to the conventional Nicolson-Ross-Weir (NRW) method, the proposed complex permittivity measurement method does not require a material fabrication process for exact MUT insertion into a waveguide. In our complex permittivity measurement, simple commercial waveguide adapters are employed instead of large flange structures. The proposed complex permittivity measurement of a non-destructive MUT is achieved by combining the NRW method, the Gaussian weighting moving average filtering technique, a full-wave electromagnetic analysis, and an optimization technique. Furthermore, the proposed methodology is validated by fabricating a Teflon-based MUT and by measuring the complex permittivity of the MUT in the Ka band (26.5–40 GHz). The results indicate that the proposed methodology exhibits good agreement with the data sheet

Spiral Spin Structures and Origin of the Magnetoelectric Coupling in YMn\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e5\u3c/sub\u3e

By combining neutron four-circle diffraction and polarized neutron-diffraction techniques we have determined the complex spin structures of a multiferroic YMn2O5 that exhibits two ferroelectric phases at low temperatures. The obtained magnetic structure has spiral components in both the low-temperature ferroelectric phases that are magnetically commensurate and incommensurate, respectively. Among proposed microscopic theories for the magnetoelectric coupling, our results are consistent with both the spin-current mechanism and the magnetostriction mechanism. Our results also explain why the electric polarization changes at the low-temperature commensurate-to-incommensurate phase transition

Enhancing Water Absorption in Sulfonated Poly(arylene ether sulfone) Polymer Electrolyte Membranes by Reducing Chain Entanglement through Constrained Deswelling

The water uptake of a polymer electrolyte membrane is a critical parameter that determines the dimensional stability and transport behavior in various energy conversion devices. In this study, the water uptake of a sulfonated poly(arylene ether sulfone) (SPAES) membrane was controlled solely by the number of chain entanglements without employing any water absorbents. Through the constrained deswelling process, the SPAES membrane achieved a significant enhancement in water uptake, increasing by up to 210% at room temperature. This notable improvement in water uptake originates from the reduction in elastic friction, represented by the number of chain entanglements, against the volume expansion resulting from the absorption of water by the sulfuric acid groups. Evidently, the controlled deswelling procedure led to biaxial stretching of the SPAES membrane, causing an increase in its surface area and a decrease in thickness. At the microscopic level, this controlled deswelling process might prompt the alignment of hydrophilic channels along the plane directions. These changes brought about by the controlled deswelling process resulted in changes to the membrane’s tensile characteristics and its transport behavior for protons and hydrogen gas

Hybrid Robust Optimization for the Design of a Smartphone Metal Frame Antenna

Hybrid robust optimization that combines a genetical swarm optimization (GSO) scheme with an orthogonal array (OA) is proposed to design an antenna robust to the tolerances arising during the fabrication process of the antenna in this paper. An inverted-F antenna with a metal frame serves as an example to explain the procedure of the proposed method. GSO is adapted to determine the design variables of the antenna, which operates on the GSM850 band (824–894 MHz). The robustness of the antenna is evaluated through a noise test using the OA. The robustness of the optimized antenna is improved by approximately 61.3% relative to that of a conventional antenna. Conventional and optimized antennas are fabricated and measured to validate the experimental results

Power-Efficient Beacon Recognition Method Based on Periodic Wake-Up for Industrial Wireless Devices

Energy harvester-integrated wireless devices are attractive for generating semi-permanent power from wasted energy in industrial environments. The energy-harvesting wireless devices may have difficulty in their communication with access points due to insufficient power supply for beacon recognition during network initialization. In this manuscript, we propose a novel method of beacon recognition based on wake-up control to reduce instantaneous power consumption in the initialization procedure. The proposed method applies a moving window for the periodic wake-up of the wireless devices. For unsynchronized wireless devices, beacons are always located in the same positions within each beacon interval even though the starting offsets are unknown. Using these characteristics, the moving window checks the existence of the beacon associated withspecified resources in a beacon interval, checks again for neighboring resources at the next beacon interval, and so on. This method can reduce instantaneous power and generates a surplus of charging time. Thus, the proposed method alleviates the problems of power insufficiency in the network initialization. The feasibility of the proposed method is evaluated using computer simulations of power shortage in various energy-harvesting conditions

Complex Permittivity Extraction using Substrate Integrated Waveguide Cavity Resonator Without Cross-Sectioning

In this paper, a dielectric properties extraction method for millimeter-wave applications is presented. Substrate integrated waveguide (SIW) cavity resonators with the same structure and varied thicknesses are employed to separate the dissipation factor (DF) of the substrate material for the cavity resonators. The dielectric constant and loss tangent of the dielectric substrate for the SIW is extracted at the resonance frequencies based on the unloaded Q-factors of transmission loss measurement. The DF from the unloaded Q-factors, which is highly dependent on the thickness of the substrate, is extracted using an iterative fitting process for the substrate thickness estimation without cross sectioning. To validate the extraction method, the SIW cavity resonators are fabricated using RO4003C substrate material and the dielectric properties are extracted in the X-band (8.2 to 12.4 GHz). The extracted thicknesses of the SIW resonators are validated by cross-sectioning. Additionally, the extracted dielectric properties are also verified by comparing the dielectric characteristics of the SIW resonators with the different thicknesses. With the presented method, the time expense for the conventional dielectric characterization method with cross-sectioning is reduced

Multi-Layer SnSe Nanoflake Field-Effect Transistors with Low-Resistance Au Ohmic Contacts

Abstract We report p-type tin monoselenide (SnSe) single crystals, grown in double-sealed quartz ampoules using a modified Bridgman technique at 920 °C. X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) measurements clearly confirm that the grown SnSe consists of single-crystal SnSe. Electrical transport of multi-layer SnSe nanoflakes, which were prepared by exfoliation from bulk single crystals, was conducted using back-gated field-effect transistor (FET) structures with Au and Ti contacts on SiO2/Si substrates, revealing that multi-layer SnSe nanoflakes exhibit p-type semiconductor characteristics owing to the Sn vacancies on the surfaces of SnSe nanoflakes. In addition, a strong carrier screening effect was observed in 70−90-nm-thick SnSe nanoflake FETs. Furthermore, the effect of the metal contacts to multi-layer SnSe nanoflake-based FETs is also discussed with two different metals, such as Ti/Au and Au contacts