Design of low-power RF energy harvester for IoT sensors

Rapid technological advancement in CMOS technologies has resulted in increased deployment of low-power Internet-of-Things (IoT) devices. As batteries, used to power-up these devices, suffer from limited lifespan, powering up numerous devices have become a major concern. Radio frequency (RF) is ubiquitous in the surroundings from which energy can be harvested and utilized to increase battery lifetime. Even for low-power sensors, RF energy harvesters can be utilized as primary power sources. However, power density of RF signals is very low and therefore building blocks of RF energy harvester need to be designed carefully to maximize efficiency to gain suitable output power. This research is focused on the design of an RF energy harvesting system in standard CMOS technology. The main goal of this research is to design an RF energy harvesting system with high power conversion efficiency (PCE) and adequate output voltage for low input power. The proposed dynamic voltage compensated cross-coupled fully differential rectifier is capable of providing very high PCE. The synchronous DC-DC boost converter provides stable DC output voltage. Rectifier and DC-DC converter of the system have been designed by using low-power transistors to ensure operation at very low input power. In order to maximize the power transfer through the system, matching network and maximum power point tracking (MPPT) controller has been implemented. In order to cope with rapid input power variation, a machine learning (ML) based MPPT controller has been designed and implemented into FPGA. The proposed ML based MPPT controller has demonstrated fast response time. To further enhance the performance of the RF energy harvesting system, a self-compensated rectifier integrated energy harvesting system is also presented. The energy extracted by using the proposed RF energy harvesting systems can easily be stored and utilized to fully power up low-power sensors used for IoT devices. Integration of RF energy harvester with these devices will significantly reduce the maintenance cost and result in energy-effluent IoT technologies.Includes bibliographical references

Effect of 3 Days of Oral Azithromycin on Young Children With Acute Diarrhea in Low-Resource Settings A Randomized Clinical Trial

Importance: World Health Organization (WHO) guidelines do not recommend routine antibiotic use for children with acute watery diarrhea. However, recent studies suggest that a significant proportion of such episodes have a bacterial cause and are associated with mortality and growth impairment, especially among children at high risk of diarrhea-associated mortality. Expanding antibiotic use among dehydrated or undernourished children may reduce diarrhea-associated mortality and improve growth. Objective: To determine whether the addition of azithromycin to standard case management of acute nonbloody watery diarrhea for children aged 2 to 23 months who are dehydrated or undernourished could reduce mortality and improve linear growth. Design, Setting, and Participants: The Antibiotics for Children with Diarrhea (ABCD) trial was a multicountry, randomized, double-blind, clinical trial among 8266 high-risk children aged 2 to 23 months presenting with acute nonbloody diarrhea. Participants were recruited between July 1, 2017, and July 10, 2019, from 36 outpatient hospital departments or community health centers in a mixture of urban and rural settings in Bangladesh, India, Kenya, Malawi, Mali, Pakistan, and Tanzania. Each participant was followed up for 180 days. Primary analysis included all randomized participants by intention to treat. Interventions: Enrolled children were randomly assigned to receive either oral azithromycin, 10 mg/kg, or placebo once daily for 3 days in addition to standard WHO case management protocols for the management of acute watery diarrhea. Main Outcomes and Measures: Primary outcomes included all-cause mortality up to 180 days after enrollment and linear growth faltering 90 days after enrollment. Results: A total of 8266 children (4463 boys [54.0%]; mean [SD] age, 11.6 [5.3] months) were randomized. A total of 20 of 4133 children in the azithromycin group (0.5%) and 28 of 4135 children in the placebo group (0.7%) died (relative risk, 0.72; 95% CI, 0.40-1.27). The mean (SD) change in length-for-age z scores 90 days after enrollment was -0.16 (0.59) in the azithromycin group and -0.19 (0.60) in the placebo group (risk difference, 0.03; 95% CI, 0.01-0.06). Overall mortality was much lower than anticipated, and the trial was stopped for futility at the prespecified interim analysis. Conclusions and Relevance: The study did not detect a survival benefit for children from the addition of azithromycin to standard WHO case management of acute watery diarrhea in low-resource settings. There was a small reduction in linear growth faltering in the azithromycin group, although the magnitude of this effect was not likely to be clinically significant. In low-resource settings, expansion of antibiotic use is not warranted. Adherence to current WHO case management protocols for watery diarrhea remains appropriate and should be encouraged. Trial Registration: ClinicalTrials.gov Identifier: NCT03130114.publishedVersionPeer reviewe