Efficient wireless power transfer via magnetic resonance coupling using automated impedance matching circuit

In this paper, an automated impedance matching circuit is proposed to match the impedance of the transmit and receive resonators for optimum wireless power transfer (WPT). This is achieved using a 2D open-circuited spiral antenna with magnetic resonance coupling in the low-frequency ISM band at 13.56 MHz. The proposed WPT can be adopted for a wide range of commercial applications, from electric vehicles to consumer electronics, such as tablets and smartphones. The results confirm a power transfer efficiency between the transmit and receive resonant circuits of 92%, with this efficiency being sensitive to the degree of coupling between the coupled pair of resonators

The role of the GP in managing suspected transient ischaemic attack: a qualitative study.

BACKGROUND: National guidelines recommend patients with suspected transient ischaemic attack (TIA) should be seen by a specialist within 24 h. However, people with suspected TIA often present to non-specialised services, particularly primary care. Therefore, general practitioners (GPs) have a crucial role in recognition and urgent referral of people with suspected TIA. This study aims to explore the role of GPs in the initial management of suspected TIA in the United Kingdom (UK). METHODS: One-to-one, semi-structured interviews with GPs, TIA clinic staff and patients with suspected TIA from two sites in the UK: Cambridge and Birmingham. Thematic analysis was undertaken to explore views on the role of the GP in managing suspected TIA. Thirty semi-structured interviews were conducted with stroke patients (n = 12), GPs (n = 9) and TIA clinic hospital staff (n = 9) from two hospitals and nine GP practices in surrounding areas. RESULTS: Three overarching themes were identified: (1) multiple management pathways for suspected TIA; (2) uncertainty regarding suspected TIA as an emergency or routine situation; and (3) influences on the urgency of GP management. CONCLUSIONS: Guidelines on the primary care management of TIA describe only a small proportion of the factors which influence GP management and referral of suspected TIA. Efforts to improve treatment, appropriate referral and patient experience should use a real rather than idealised model of the GP role in managing suspected TIA.This research was funded by the National Institute for Health Research. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. The funders had no role in the design of the study and collection, analysis, and interpretation of data or in writing the manuscript. JM and GT receive funding from the National Institute for Health Research NIHR Senior Investigator Award and Postdoctoral Fellowship Award, respectively. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care

Multi-Way and Poly-Phase Wideband Differential Phase Shifter Based on Metamaterial Technology

This paper presents multi-way and poly-phase differential phase shifter (DPS) based on metamaterial technology to realize delay lines of equal length. The proposed phase shifter provides the required phase shift relative to the reference line over a wide bandwidth. Several DPS phase shifter designs were fabricated and tested to verify their performance. Measured results show that the proposed phase shifter has phase deviation of less than ±4° and return-loss better than 10-dB with an insertion-loss of less than 1 dB across 2.2 to 4.4 GHz

Multiband antenna for portable device applications

This article describes a compact planar microstrip antenna for multiband transceiver application. The proposed antenna consists of a combination of E-shaped and C-shaped radiators that are excited via a common microstrip feed-line. Embedded in the ground-plane are included an open- and short-ended slots whose purpose is to enhance the antenna's impedance match and increase the number of bands in which the antenna can operate. A prototype antenna was fabricated on a standard FR4 substrate with εr of 4.4 and thickness of 1.6 mm, and its reflection-coefficient and radiation patterns were measured to demonstrate its feasibility. Measurements confirm the antenna can simultaneously operate over the frequency bands of: DCS (1.71–1.85 GHz), PCS (1.85–1.99 GHz), UMTS (1.92–2.17 GHz), Wibro (2.3–2.39 GHz), WLAN+ Bluetooth (2.4–2.48 MHz), WIMAX (2.5–2.69 GHz), WIMAX (3.3–3.5 GHz), HIPERLAN2 (5.15–5.35/5.47–5.725 GHz), and WLAN (5.15–5.35/5.725–5.825 GHz). The antenna has dimensions of 30 × 40 × 1.6 mm3, which is compatible with the requirements imposed by portable wireless systems

Overcoming Inherent Narrow Bandwidth and Low Radiation Properties of Electrically Small Antennas by Using an Active Interior-Matching Circuit

A technique is described to extend the working frequency-band and increase the radiation gain and efficiency of an electrically small antenna (ESA). The geometry of the proposed ESA is in the shape of an "H" structure. A small gap is included at the symmetry of the H-shape structure to embed an inductive load that is used to connect the two halves of the H-shaped antenna. With the lumped element inductor, the bandwidth of the H-shaped antenna is restricted by Chu-lower bound. However, it is demonstrated by analytical analysis and through 3D full-wave electromagnetic simulations that when the inductive load is replaced with negative reactance from a negative impedance converter (NIC) the antenna's bandwidth, radiation gain and efficiency performance can be significantly improved by similar to 40%, 3.6 dBi and 55%, respectively. This is because NIC acts as an effective interior matching circuit. The resonant frequency of the antenna structure with the inductive element was used to determine the required inductance variation in the NIC to realize the required bandwidth and radiation characteristics from the H-shaped antenna

Miniature in-phase Wilkinson power divider with pair of parallel transmission-lines for application in wireless microwave systems

A novel miniature Wilkinson power divider (WPD) design is presented. This is achieved by substituting the quarter-wavelength transmission-lines constituting the WPD with an equivalent pair of parallel transmission-lines (PPTLs) that effectively reduce the circuit size of the WPD by 43% compared with a conventional design whose ground-plane is defected. Particle swarm optimization (PSO) technique is used to achieve size reduction. Meandering the transmission-lines further reduce the WPD size by 22%. The proposed WPD has overall dimensions of 9.38 × 11.51 mm2 or 0.11 λg × 0.14 λg, which is compatible with the requirements imposed by portable personal wireless systems. Coupling between the parallel transmission-lines is shown to extend the operational bandwidth of the power divider to 3.2 GHz (0.8–4 GHz) for a return-loss better than 10 dB

Compact and low-profile on-chip antenna using underside electromagnetic coupling mechanism for terahertz front-end transceivers

The results presented in this paper show that by employing a combination of metasurface and substrate integrated waveguide (SIW) technologies, we can realize a compact and low-profile antenna that overcomes the drawbacks of narrow-bandwidth and low-radiation properties encountered by terahertz antennas on-chip (AoC). In addition, an effective RF cross-shaped feed structure is used to excite the antenna from its underside by coupling, electromagnetically, RF energy through the multi-layered antenna structure. The feed mechanism facilitates integration with the integrated circuits. The proposed antenna is constructed from five stacked layers, comprising metal-silicon-metal-silicon-metal. The dimensions of the AoC are 1 x 1 x 0.265 mm(3). The AoC is shown to have an impedance match, radiation gain and efficiency of <= -15 dB, 8.5 dBi and 67.5%, respectively, over a frequency range of 0.20-0.22 THz. The results show that the proposed AoC design is viable for terahertz front-end applications

Realizing uwb antenna array with dual and wide rejection bands using metamaterial and electromagnetic bandgaps techniques

This research article describes a technique for realizing wideband dual notched functionality in an ultra-wideband (UWB) antenna array based on metamaterial and electromagnetic bandgap (EBG) techniques. For comparison purposes, a reference antenna array was initially designed comprising hexagonal patches that are interconnected to each other. The array was fabricated on standard FR-4 substrate with thickness of 0.8 mm. The reference antenna exhibited an average gain of 1.5 dBi across 5.25-10.1 GHz. To improve the array's impedance bandwidth for application in UWB systems metamaterial (MTM) characteristics were applied it. This involved embedding hexagonal slots in patch and shorting the patch to the ground-plane with metallic via. This essentially transformed the antenna to a composite right/left-handed structure that behaved like series left-handed capacitance and shunt left-handed inductance. The proposed MTM antenna array now operated over a much wider frequency range (2-12 GHz) with average gain of 5 dBi. Notched band functionality was incorporated in the proposed array to eliminate unwanted interference signals from other wireless communications systems that coexist inside the UWB spectrum. This was achieved by introducing electromagnetic bandgap in the array by etching circular slots on the ground-plane that are aligned underneath each patch and interconnecting microstrip-line in the array. The proposed techniques had no effect on the dimensions of the antenna array (20 mm x 20 mm x 0.87 mm). The results presented confirm dual-band rejection at the wireless local area network (WLAN) band (5.15-5.825 GHz) and X-band satellite downlink communication band (7.10-7.76 GHz). Compared to other dual notched band designs previously published the footprint of the proposed technique is smaller and its rejection notches completely cover the bandwidth of interfering signals

Herschel-SPIRE-Fourier Transform Spectroscopy of the nearby spiral galaxy IC342

We present observations of the nearby spiral galaxy IC342 with the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer. The spectral range afforded by SPIRE, 196-671 microns, allows us to access a number of 12CO lines from J=4--3 to J=13--12 with the highest J transitions observed for the first time. In addition we present measurements of 13CO, [CI] and [NII]. We use a radiative transfer code coupled with Bayesian likelihood analysis to model and constrain the temperature, density and column density of the gas. We find two 12CO components, one at 35 K and one at 400 K with CO column densities of 6.3x10^{17} cm^{-2} and 0.4x10^{17} cm^{-2} and CO gas masses of 1.26x10^{7} Msolar and 0.15x10^{7} Msolar, for the cold and warm components, respectively. The inclusion of the high-J 12CO line observations, indicate the existence of a much warmer gas component (~400 K) confirming earlier findings from H_{2} rotational line analysis from ISO and Spitzer. The mass of the warm gas is 10% of the cold gas, but it likely dominates the CO luminosity. In addition, we detect strong emission from [NII] 205microns and the {3}P_{1}->{3}P_{0} and {3}P_{2} ->{3}P_{1} [CI] lines at 370 and 608 microns, respectively. The measured 12CO line ratios can be explained by Photon-dominated region (PDR) models although additional heating by e.g. cosmic rays cannot be excluded. The measured [CI] line ratio together with the derived [C] column density of 2.1x10^{17} cm^{-2} and the fact that [CI] is weaker than CO emission in IC342 suggests that [CI] likely arises in a thin layer on the outside of the CO emitting molecular clouds consistent with PDRs playing an important role.Comment: 9 pages, 8 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS

Antenna on chip (Aoc) design using metasurface and siw technologies for thz wireless applications

This paper presents the design of a high-performance 0.45-0.50 THz antenna on chip (AoC) for fabrication on a 100-micron GaAs substrate. The antenna is based on metasurface and substrate-integrated waveguide (SIW) technologies. It is constituted from seven stacked layers consisting of copper patch-silicon oxide-feedline-silicon oxide-aluminium-GaAs-copper ground. The top layer consists of a 2 x 4 array of rectangular metallic patches with a row of subwavelength circular slots to transform the array into a metasurface. This essentially enlarges the effective aperture area of the antenna. The antenna is excited using a coplanar waveguide feedline that is sandwiched between the two silicon oxide layers below the patch layer. The proposed antenna structure reduces substrate loss and surface waves. The AoC has dimensions of 0.8 x 0.8 x 0.13 mm(3). The results show that the proposed structure greatly enhances the antenna's gain and radiation efficiency, and this is achieved without compromising its physical size. The antenna exhibits an average gain and efficiency of 6.5 dBi and 65%, respectively, which makes it a promising candidate for emerging terahertz applications