Design and performance analysis of a purely textile spiral antenna for on-body NFC applications

Novel combinations of materials and construction techniques are key for the development of new textile antenna configurations for on-body applications. Stretchable, flexible and conformable features of textile antennas are one of the hot research topics nowadays. This work gives a step forward with new designs of purely textile spiral antennas with flexible and robust features for Near Field Communications (NFC) on-body applications. Their performance is successfully validated with a real NFC chipset, and some design and construction considerations are offered for novel textile materials

A combination of transmission line models as design instruments for electromagnetically coupled microstrip patch antennas in the 2.45 GHz ISM band

This communication presents an analytical framework that combines transmission line models for the design of electromagnetically coupled microstrip patch antennas for the 2.45 GHz industrial, scientific, and medical band. It provides initial values for all dimensions of the antenna, with measured resonance frequency errors below 6%. The initial design is optimized in two subsequent phases to center the resonance frequency and to increase the impedance bandwidth (BW), obtaining measured resonance frequency errors below 0.6% and BW enhancements of more than 1.2 times the original ones, respectively. The model has been validated with antenna prototypes based on rigid and textile materials, exhibiting excellent free-space measured BW of 4% and 5.12%, maximal measured gains of 4.28 and 7.33 dBi, and radiation efficiencies of 63.4% and 71.8%, respectively. Moreover, very stable on-body performance is obtained, with minimal frequency detuning when deploying the textile antenna on the human body. The measured maximum on-body gain for the textile antenna equals 5.5 dBi, with a simulated specific absorption rate of 0.323 W/kg at 2.45 GHz

Reliable lab-scale construction process for electromagnetically coupled textile microstrip patch antennas for the 2.45 & x00A0;GHz ISM Band

A precise layer alignment is crucial to ensure performance repeatability of multilayer microstrip antennas. We introduce a novel lab-scale construction process for multilayer microstrip textile patch antennas that consists in combining an alignment method, based on laser-cut wood frames to perform accurate layer alignment, with a fast intralayer attachment method, based on thermally activated adhesive sheets. This lab-scale construction process is validated with an electromagnetically coupled microstrip rectangular patch textile antenna operating in the 2.45 & x00A0;GHz ISM band. It has been reproduced eight times to validate the proposed construction process. The differences between desired simulated versus measured average values of the resonant frequencies, impedance bandwidths, gains, and total efficiencies equal 6.25 & x00A0;MHz, 21.5 & x00A0;MHz, 0.6 & x00A0;dBi, and 4.45 & x0025;, respectively. Moreover, the standard deviations of measured resonant frequencies, impedance bandwidths, gains, and total efficiencies equal 24.54 & x00A0;MHz, 14.02 & x00A0;MHz, 0.15 & x00A0;dBi, and 3.57 & x0025;, respectively. These results confirm that the novel lab-scale construction process provides good performance repeatability of multilayer microstrip textile patch antennas

2 x 2 textile rectenna array with electromagnetically coupled microstrip patch antennas in the 2.4 GHz WiFi band

The development of e-textiles is fostering research in wireless energy transmission. This paper presents a purely textile 2.4 GHz WiFi band 2 x 2 rectenna array for RF energy harvesting. It utilizes the electromagnetically coupled microstrip patch antenna topology and a simple and precise construction method that provides a good performance repeatability to create multilayer microstrip textile patch antennas. The rectifier is implemented with Schottky diodes and it takes the voltage doubling configuration. An average DC power of 1,1 mW was measured for 14 mu W/cm(2) of RF input power density, while the end-to-end average power conversion efficiency (PCE) measured was 31%. The characterization of the end-to-end PCE was evaluated considering the physical size of the prototype to make the comparison with other designs easier. Measurements in a real WiFi scenario were also performed, demonstrating its feasibility for feeding e-textiles

Experimental Frequency Tuning Methodology of a Cantilever Piezoelectric Harvester Validated in a Multimodal Transportation

Piezoelectric energy harvesting is a promising technology that increases the autonomy of low power IoT devices in scenarios that are subjected to mechanical vibrations. This work shows the potential of this technology to power IoT devices with the energy that is harvested from vibrations occurred during air and road transportation. Adjusting the natural resonance frequency of the piezoelectric generator (PEG) to the mechanical acceleration frequency that has the highest power spectral density is key to increase the harvested energy. Therefore, in this work a commercial PEG is tuned to the best spectrogram frequency of a real vibration signal following a two-phase tuning process. The harvested power generated by the PEG has been validated in real scenarios, providing 2.4 μ Wh during flight (take-off, cruise flight, and landing), 11.3 μ Wh during truck transportation in urban areas, and 4.8 μ Wh during intercity transportation. The PEG has been embedded in an ultra-low power IoT device to validate how much this harvested energy can increase the autonomy in a real scenario that is subjected to similar vibrations. An NFC temperature data logger is developed for perishable products that are transported by air and road transports. The energy harvested by the PEG tuned with the methodology proposed in this work has increased the autonomy of the data logger 16.7% during a real use case of 30 h, which validates the potential of the piezoelectric energy harvesting technology to increase the autonomy of future low power IoT devices used in scenarios with aperiodic vibrations

International prevalence and risk factors evaluation for drug-resistant Streptococcus pneumoniae pneumonia

Objective: Streptococcus pneumoniae is the most frequent bacterial pathogen isolated in subjects with Community-acquired pneumonia (CAP) worldwide. Limited data are available regarding the current global burden and risk factors associated with drug-resistant Streptococcus pneumoniae (DRSP) in CAP subjects. We assessed the multinational prevalence and risk factors for DRSP-CAP in a multinational point-prevalence study. Design: The prevalence of DRSP-CAP was assessed by identification of DRSP in blood or respiratory samples among adults hospitalized with CAP in 54 countries. Prevalence and risk factors were compared among subjects that had microbiological testing and antibiotic susceptibility data. Multivariate logistic regressions were used to identify risk factors independently associated with DRSP-CAP. Results: 3,193 subjects were included in the study. The global prevalence of DRSP-CAP was 1.3% and continental prevalence rates were 7.0% in Africa, 1.2% in Asia, and 1.0% in South America, Europe, and North America, respectively. Macrolide resistance was most frequently identified in subjects with DRSP-CAP (0.6%) followed by penicillin resistance (0.5%). Subjects in Africa were more likely to have DRSP-CAP (OR: 7.6; 95% CI: 3.34-15.35, p < 0.001) when compared to centres representing other continents. Conclusions: This multinational point-prevalence study found a low global prevalence of DRSP-CAP that may impact guideline development and antimicrobial policies. Published by Elsevier Ltd on behalf of The British Infection Association