Performance characteristics on patch antenna with sar reduction using artificial magnetic conductor (amc) for wban applications

Great advances have been made in the area of wireless body area networks (WBANs) of improving wireless communication technology since the invention. These advances range in refining, size reduction and shape, gain improvement, more efficiency and combination of the requirements for applications which include health monitoring, military and personal navigation entertainment. Several types of antennas have been developed for WBANs and they have achieved narrow bandwidth, decrease gain, low radiation efficiency, a high specific absorption rate (SAR) value, high front-to-back ratio (FBR) and structural complexity. However, it is necessary to achieve better performance antenna for less impact of frequency detuning, by improving FBR, high radiation efficiency and reduce SAR for WBAN application. Conventional patch antennas are adopted since they can be low weight, low profile and easy to integrate with the device. Having these unique characteristics, patch antenna has shown to have clear advantages for WBAN applications. Since an antenna is placed a close to the human body with its curvatures and complexities, the antenna performance must be taking into account the structural, mismatch, and losses caused by the body, while simultaneously sustaining optimum performance. This work proposes to design, analysis and optimization of low-profile antenna integrated with Artificial Magnetic Conductor (AMC) for WBAN applications. Multilayer model of the adult human body at the frequency band of the proposed antenna is used, which helps to study the effects of the human on the antenna performance. The results showed that the presence of human head affects the antenna performance in terms of radiation pattern, efficiency and S11 and SAR values on the body parts. To further improve the performance of the proposed antenna design, several techniques have been developed in reducing SAR value with low complexity using AMC to realize broadside radiation for on /off body communication. AMC structure and miniaturized reflector reduce the back radiation and the impact of frequency detuning due to high losses of human body and the two proposed techniques are mounted on human head phantom. In addition, AMC improved FBR by 15.3 dB with enhanced of gain 7.61 dBi and radiation efficiency more than 88 %. The AMC have achieved 93.7 % reduction of the initial SAR value while metal reflector achieved a reduction of 77.7 %. Then, the antenna is fabricated and measured to validate the concept. Thus, the proposed antenna with AMC structure was designed and fabricated using two different materials for far-field radiation pattern measurements. The measured and simulated results reveals that proposed antenna with AMC array shows good impedance matching and far-field radiation pattern .Therefore, the proposed antenna is a potential candidate for WBAN

Analysis of three different dielectric substrates on square ring microstrip antenna for wireless application

The sizes and weights of various wireless electronic systems (e.g. mobile handsets) have rapidly reduced due to development of modern integrated circuit technology. However, microstrip antenna suffers from low bandwidth. The objective of this project was to improve the bandwidth by proposing square ring technique and investigation for the enhancement strategy of bandwidth performance and analysis of different commercially available dielectric materials. The performance of different dielectric material for design of a square ring microstrip patch antenna is analyzed in terms of bandwidth. A square ring microstrip patch antenna was designed not only to improve the antenna bandwidth but also to reduce the size of the conventional microstrip patch antenna. Analysis of the design of microstrip patch antenna at C-band frequency range (4-8GHz) has been carried out using commercial available computer model of CST. This study will help for authors and researchers to get a fair idea of which substrate should be given preference and why for fabricating microstrip patch antenna. It has been shown that the use of square ring antenna produces an optimum bandwidth performance of approximately 5.9% in roger material for using fabrication. Experimental work has been performed to validate the predicted results obtained from CST analysis by using network analyzer. Both simulated and measured results have shown a good agreement

Inverted Diamond-shaped Notched Substrate and Patch for High-frequency Interference on Ultra-wideband Antenna

Notches loaded on a patch antenna can affect significantly on ‎the antenna impedance matching. Therefore, notching technique is an efficient way to reduce ‎the electromagnetic interference with unwanted bands. In this paper, a ‎novel inverted diamond‏-‏shaped closed-end slot on a substrate and ‎vertex-fed printed hexagonal patch ultra‏-‏wideband antenna is proposed for high-frequency band rejection. This antenna is fed using ‎coplanar waveguide, and it is optimised by veering several patch ‎parameters which further improved the inter bandwidth at both the ‎lower and upper bands. However, the centre-notched band is shifted ‎from 6 GHz to 7.5 GHz by cutting the inverted diamond shape in a ‎special process. The developed ultra-wideband antenna is verified by ‎comparing the simulation results with the measurement results. The ‎measured results with a fractional bandwidth of 133% have a good ‎agreement with the simulation results 146%. Moreover, the measured radiation showed omnidirectional patterns‎

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population