Investigation into the design of broadband singly-fed electromagnetically coupled patch (EMCP) antenna elements and arrays for circular polarisation

University of Technology, Sydney. Faculty of Engineering.The rapid development of satellite and wireless communications pose extraordinary demands on broadband circularly polarised (CP) antenna elements and high-performance antenna arrays. The use of high-dielectric-constant materials as the substrate for the driven layer and a low-dielectric-constant material as superstrate for the radiating patch overcomes the conflict between circuit integration and antenna radiation. The aim of the research presented in this thesis is to design and develop high performance singly-fed microstrip patch antennas and arrays for CP applications. Firstly, we introduce a singly-fed cross-aperture coupled patch antenna and a stacked patch antenna using high and low dielectric materials known as Type-F and Type-E elements, respectively. As the physical structure of the Type-E element is close to the conventional linearly-polarised electromagnetically coupled patch (LP-EMCP) antennas, we have also denoted it as CP-EMCP antenna. The development of CP-EMCP antennas addresses the drawbacks of the cross-aperture patch antenna. A systematic optimisation method is developed for the design of CP-EMCP elements, at which the mean frequencies of the bandwidths can be adjusted in order to achieve a wide overlaid bandwidth. Secondly, we investigate the effects of perturbation on the parasitic patch, layer displacements, material tolerances and superstrate thicknesses on the broadband performance as well as the mutual coupling of the CP-EMCP elements. Both our theoretical and experimental results show that the CP-EMCP elements are robust in performance and have a low mutual coupling. When compared to the conventional stacked EMCP antennas and to the reduced surface-wave antenna, the mutual coupling between CP-EMCP elements is lower which allows the use of small element spacings to avoid grating lobes, which therefore make these elements good candidates for high-performance CP arrays. Following a parametric study on the effect of displacements between stacked patches and the loss consideration of the coplanar feed network printed on high dielectric constant substrates, the modified Type-E elements whose parasitic patch have a zero perturbation are developed for the design of high performance CP arrays. The low mutual coupling allows short feed-lines to connect with the spatially offset elements so as to minimise the feed loss. Consequently, it became possible to develop the novel sequentially rotating feed networks which incorporate the modified elements with a small element spacing of 2/3/λₒ for the 4- and 16-element planar antenna arrays. The results indicate that these arrays have high gain, low axial ratio, high antenna efficiency low sidelobe levels, and wide overlaid bandwidth

A circularly polarized stacked electromagnetically coupled patch antenna

In this communication, we present a high-performance circularly polarized (CP) stacked electromagnetically coupled patch antenna and its subarray at X band. In addition to low boresight axial-ratios, the subarray has measured 10-dB impedance and 3-dB axial-ratio bandwidths of 25.6% and 23.5% respectively as compared to the measured 20.2% and 8.0% for a single element. The mutual coupling for this element is shown to be lower than other reported stacked patch antennas and obtained a gain (> 10 dbic) bandwidth of 23.5%. The calculated antenna efficiency is 89% around center frequency for the single element whereas the subarray has an overall efficiency of >71% (-1.5 dB) over 21% bandwidth

F-shaped Shorted Patch Antenna with Dual-frequency Characteristics

This paper presents a compact shorted patch antenna. The antenna is based on an F-shaped printed conductor coaxially fed with an electromagnetically coupled shorted inverted F-shaped antenna interleaved with each other. The overall antenna is then coupled with a rectangular ring. The antenna has dual characteristic features and its resonance frequency is at 1.85 GHz and 2.42 GHz. The measured return loss bandwidth and its far field radiation patterns are presented. The gain of the antenna is 1.6 dBiDepartment of Electronic and Information EngineeringRefereed conference pape

Mechanisms of airway epithelial injury and abnormal repair in asthma and COPD

The airway epithelium comprises of different cell types and acts as a physical barrier preventing pathogens, including inhaled particles and microbes, from entering the lungs. Goblet cells and submucosal glands produce mucus that traps pathogens, which are expelled from the respiratory tract by ciliated cells. Basal cells act as progenitor cells, differentiating into different epithelial cell types, to maintain homeostasis following injury. Adherens and tight junctions between cells maintain the epithelial barrier function and regulate the movement of molecules across it. In this review we discuss how abnormal epithelial structure and function, caused by chronic injury and abnormal repair, drives airway disease and specifically asthma and chronic obstructive pulmonary disease (COPD). In both diseases, inhaled allergens, pollutants and microbes disrupt junctional complexes and promote cell death, impairing the barrier function and leading to increased penetration of pathogens and a constant airway immune response. In asthma, the inflammatory response precipitates the epithelial injury and drives abnormal basal cell differentiation. This leads to reduced ciliated cells, goblet cell hyperplasia and increased epithelial mesenchymal transition, which contribute to impaired mucociliary clearance and airway remodelling. In COPD, chronic oxidative stress and inflammation trigger premature epithelial cell senescence, which contributes to loss of epithelial integrity and airway inflammation and remodelling. Increased numbers of basal cells showing deregulated differentiation, contributes to ciliary dysfunction and mucous hyperproduction in COPD airways. Defective antioxidant, antiviral and damage repair mechanisms, possibly due to genetic or epigenetic factors, may confer susceptibility to airway epithelial dysfunction in these diseases. The current evidence suggests that a constant cycle of injury and abnormal repair of the epithelium drives chronic airway inflammation and remodelling in asthma and COPD. Mechanistic understanding of injury susceptibility and damage response may lead to improved therapies for these diseases

Lowered Immune Cell Function in Liver Recipients Recovered From Posttransplant Lymphoproliferative Disease Who Developed Graft Tolerance

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Effects of Repeated Central Administration of Endothelin Type A Receptor Antagonist on the Development of Neuropathic Pain in Rats

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Polarization-Rotated Waveguide Antennas for Base-Station Applications

© 2017 IEEE. A novel base-station antenna element is proposed. It consists of an artificial surface composed of parallel strips rotating in the polarization direction and a segment of a rectangular waveguide. The surface is designed on a single-sided substrate, which has the same area as the aperture of the waveguide. To achieve the polarization rotation, the parallel strips on the surface are rotated by 45° with respect to the orientation of the waveguide antenna. By adding the surface, the linear polarization direction of the rectangular waveguide antenna rotates by 45° to comply with the requirements of the cellular industry. To verify the simulation results, the proposed antenna was fabricated and measured. Results show that the antenna has an operating bandwidth from 698-960 MHz, where a stable radiation pattern is achieved

Patient Empowerment Programme in primary care reduced all-cause mortality and cardiovascular diseases in patients with type 2 diabetes mellitus: a population-based propensity-matched cohort study

Aims: To assess whether a structured diabetes education programme, Patient Empowerment Programme (PEP), was associated with a lower risk of first cardiovascular disease (CVD) event and all-cause mortality in a population-based cohort of type 2 diabetes mellitus (T2DM) patients in primary care. Materials and Methods: A Chinese cohort of 27,278 T2DM patients without prior occurrence of CVD events on or before baseline study recruitment date was linked to the Hong Kong administrative database from 2008 to 2013. PEP was provided to T2DM patients treated at primary care outpatient clinics through community trained professional educators. Non-PEP participants were matched one-to-one with the PEP participants using propensity score method with respect to their baseline covariates. Cox proportional hazard regressions were performed to estimate the associations of PEP with the occurrence of first CVD event, coronary heart disease, stroke, heart failure and death from any cause, controlling for baseline characteristics. Results: During a median of 21.5 months follow-up, 795 (352 PEP participants and 443 non-PEP participants) patients suffered a first CVD event. After adjusting for confounding variables, PEP participants had a lower incidence of all-cause mortality (hazard ratio: 0.564; 95%CI:0.445-0.715; P < 0.001), first CVD (hazard ratio: 0.807; 95%CI:0.696-0.935; P = 0.004) and stroke (hazard ratio: 0.702; 95%CI:0.569-0.867; P = 0.001) events than those without PEP. Conclusions: Enrolment in PEP was associated with reduced all-cause mortality and first CVD events among T2DM patients. The CVD benefit of PEP might be attributable to improving metabolic control through empowerment of self-care and enhancement of quality of diabetes care in primary care.postprin

Effects of Patient Empowerment Programme (PEP) on Clinical Outcomes and Health Service Utilization in Type 2 Diabetes Mellitus in Primary Care: An Observational Matched Cohort Study

Background: To evaluate the effects of a large population-based patient empowerment programme (PEP) on clinical outcomes and health service utilization rates in type 2 diabetes mellitus (T2DM) patients in the primary care setting. Research Design and Subjects: A stratified random sample of 1,141 patients with T2DM enrolled to PEP between March and September 2010 were selected from general outpatient clinics (GOPC) across Hong Kong and compared with an equal number of T2DM patients who had not participated in the PEP (non-PEP group) matched by age, sex and HbA1C level group. Measures: Clinical outcomes of HbA1c, SBP, DBP and LDL-C levels, and health service utilization rates including numbers of visits to GOPC, specialist outpatient clinics (SOPC), emergency department (ED) and inpatient admissions, were measured at baseline and at 12-month post-recruitment. The effects of PEP on clinical outcomes and health service utilization rates were assessed by the difference-in-difference estimation, using the generalized estimating equation models. Results: Compared with non-PEP group, PEP group achieved additional improvements in clinical outcomes over the 12-month period. A significantly greater percentage of patients in the PEP group attained HbA1C≤7% or LDL-C≤2.6 mmol/L at 12-month follow-up compared with the non-PEP group. PEP group had a mean 0.813 fewer GOPC visits in comparison with the non-PEP group. Conclusions: PEP was effective in improving the clinical outcomes and reduced the general outpatient clinic utilization rate over a 12-month period. Empowering T2DM patients on self-management of their disease can enhance the quality of diabetes care in primary care.published_or_final_versio