Microstrip Patch Antenna Miniaturisation Techniques: A Review

The microstrip patch antenna (MPA) has been in use and has been studied extensively during the past three decades. This antenna, which consists of a metallic patch printed on a dielectric substrate over a ground plane, offers several advantages including ease of design and fabrication; low profile and planar structure; and ease of integration with circuit elements. The minimum dimension of a conventional MPA is in the order of half a wavelength. In recent years, with the advent of new standards and compact wireless devices, there has been a need to reduce the size of this type of antenna. This study discusses some of the principal techniques that have been reported in the literature to reduce the size of an MPA. These miniaturisation techniques include material loading, reshaping the antenna, shorting and folding, introducing slots and defects in the ground plane and the use of metamaterials. The major features and drawbacks of each of these approaches are highlighted in this study along with their effects on the antenna performance metrics

A Low Complexity Direction Finding System Based on a Six-Port Integrated MIMO Antenna System

In this paper, a low complexity microwave based direction finding (DF) system is presented. The proposed system consists of single six-port (SP) circuit integrated with a reconfigurable multiple-input-multiple-output (MIMO) antenna system. The SP circuit covers a wide frequency band (1.68∼2.25 GHz). The SP circuit is also characterized for phase error compensation caused by the slight asymmetry of SP and power detectors. The reconfigurable MIMO antenna system used is compact design, covered several well-known wireless standards between frequency bands from 0.7 GHz to 3 GHz. The SP circuit is integrated with reconfigurable MIMO antenna system to form complete beam forming mode for second generation cognitive radio (CR) platforms. The proposed design is a complete integrated solution with DF capabilities for CR platforms. The design is suitable to be used in compact wireless handheld and mobile communication devices. The fabricated integrated system achieves ±16o accuracy in its direction of arrival estimates

Clinical Characteristics of Autoimmune Hepatitis in a Middle Eastern Population: A Tertiary Care Center Experience

Autoimmune hepatitis (AIH) is an immune-mediated inflammatory liver disease of uncertain cause, and its manifestations appear to vary by race and ethnicity. The literature on AIH in the Middle East, including Jordan, is scarce; therefore, this study aimed to determine the clinical characteristics of AIH in an understudied population. This retrospective chart review study was conducted on AIH patients who presented to Jordan University Hospital over a seven-year period (2014–2020). Retrieved data included sociodemographics, liver function tests, autoimmune serologic markers, viral hepatitis serology, findings on liver biopsies, treatment regimens, post-therapy outcomes and treatment-related complications. The total number of AIH patients included in the study was 30, divided as follows: type 1 AIH (n = 17, 56.7%), type 2 AIH (n = 2, 6.7%), seronegative AIH (n = 9, 30.0%), and two patients who had AIH-primary biliary cirrhosis overlap syndrome (6.7%). The mean age at diagnosis was 44 years (standard deviation: 17 years), with a female predominance (n = 25, 83.3%). Acute presentation was seen among 18 patients (60.0%). Mild to moderate fibrosis (F1 and F2 on METAVIR scoring system) without cirrhosis was observed among patients who underwent liver biopsies (10/19, 52.6%). The majority of patients (73.3%) were initially treated with prednisone, with azathioprine combination in 16.7% of the patients. At 6 months post initial treatment, twenty patients (66.7%) achieved biochemical remission, four patients had incomplete response, two patients failed to improve (one died during the induction of remission period due to AIH-related complications), and four patients were lost to follow-up. This study provided an updated overview of AIH in Jordan. The results showed typical female predominance, and interestingly high rates of acute presentation and seronegative disease. Future longitudinal studies are recommended to address the nature and long-term prognosis of AIH in Jordan

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.The aim of this study was to inform vaccination prioritization by modelling the impact of vaccination on elective inpatient surgery. The study found that patients aged at least 70 years needing elective surgery should be prioritized alongside other high-risk groups during early vaccination programmes. Once vaccines are rolled out to younger populations, prioritizing surgical patients is advantageous