Bandwidth improvements using ground slots for compact UWB microstrip-fed antennas

The paper studies the method of using a ground slot for bandwidth improvement of compact ultra-wide band (UWB) antennas with microstrip line feed. Slots of different shapes such as triangular, rectangular, partially circular and hexagonal, placed on the ground plane under the feed line of the radiator are studied for impedance matching. The effects of the slots on the performances of the antennas, in terms of impedance bandwidth, radiation pattern, gain, and efficiency, are studied. Results of simulation tests show that a ground slot with proper dimensions placed under the feed line can improve the impedance matching and hence increase the bandwidth without affecting much the performance of the antenna. Results of studies also show that, by using a hexagonal slot on the ground plane under the feed line, a patch antenna with a compact size of 35mm × 23mm can achieve a bandwidth of 3.1-16.3 GHz for S 11 < -10 dB. Moreover, it has a stable omnidirectional radiation pattern across the whole bandwidth and achieves an average gain of 2.8 dBi and an average efficiency of about 88% across the UWB.published_or_final_versio

Isolation improvement using CMRC for MIMO antennas

In this paper, a compact microstrip resonant cell (CMRC) is proposed to improve isolation of antenna elements in the design of multiple-input multiple-output (MIMO) antennas. The MIMO antenna used for studies consists of two symmetrical L-shaped planar inverted-F antenna (PIFA) elements placed at a distance of 16.2 mm on a printed-circuit board (PCB). A single-layer CMRC is etched on the PCB between the PIFA elements to improve isolation between them. Computer simulation is used to study and design the MIMO antenna. Results show that the CMRC can increase isolation between the two PIFA elements by 10 dB in the 2.4-GHz WLAN band. The envelope correlation coefficient (ECC) is about 0.0005 to 0.0035 over the frequency band.postprin

A compact ultrawideband MIMO antenna

A multiple-input multiple-output (MIMO) antenna having a very compact size of 40×26 mm2 is proposed for portable ultrawideband (UWB) applications. Two planar monopole antennas with microstrip-fed are used as the elements of the MIMO antenna and are placed perpendicularly to each other to achieve pattern diversity. Two stubs are etched on the ground plane to enhance isolation between the two elements and increase the impedance bandwidth of the MIMO antenna. Results show the MIMO antenna can cover the entire UWB band from 3.1-10.6 GHz with an isolation of larger than 16 dB throughout the frequency band. © 2013 EurAAP.published_or_final_versio

Design of a printed multiband MIMO antenna

A multiband MIMO antenna using planar technology is proposed for next generation mobile communication system. The antenna consists of two symmetrical monopole elements printed in parallel to each other at the upper and lower corners of a printed-circuit board (PCB) with a size 50×110 mm2 which is similar to the side of a mobile phone. The two monopoles have two branch strips to generate two frequency bands. By using a parasitic element in each monopole, a much enhanced bandwidth in the upper band can be obtained. A lumped-impedance network is designed to enhance matching at the input ports for the two antenna elements. Computer simulation is used to study, design and optimize the antenna. Results indicate that the proposed MIMO antenna has a very bandwidth enough to cover the LTE (lower band), DCS1800, PCS1900, UMTS-2100, Wibro Band, 2.4G-WLAN, and Wimax (upper band) systems. To enhance the isolation between the two monopole elements within the desirable frequency bands, a slit is cut in the middle on the PCB ground. The MIMO antenna a very low profile and low cost which makes the design very attractive for mobile phone applications. © 2013 EurAAP.published_or_final_versio

Modeling of cable for measurements of small monopole antennas

Coaxial cable is often used for measurements of antennas inside anechoic chambers. In the measurement of a monopole antenna with a small ground-plane, the finite-sized ground causes the current to flow back from the radiator to the outer surface of the coaxial cable. This results in secondary radiation which introduces errors to the measured radiation pattern. To reduce the unwanted secondary radiation, the coaxial cable can be covered with EMI suppressant tubing materials. However, this introduces errors to the measured efficiency. In this paper, the models of the coaxial cable with and without suppressant tubing are developed and used for computer simulation. The cable effects on the measured results of a small monopole ultrawide band (UWB) antenna are studied by using the antenna measurement equipment Satimo StarLab and the EM simulation tool CST. The results show great agreements between the simulated and measured results. © 2011 IEEE.published_or_final_versio

Voriconazole and fluconazole increase the exposure to oral diazepam

Conclusion Both voriconazole and fluconazole considerably increase the exposure to diazepam. Recurrent administration of diazepam increases the risk of clinically significant interactions during voriconazole or fluconazole treatment, because the elimination of diazepam is impaired significantly

Time and travel costs incurred by women attending antenatal tests: A costing study

OBJECTIVE: to estimate the costs to women, their friends and family for different antenatal tests in the Down's syndrome (DS) screening pathway. DESIGN: questionnaire-based costing study. SETTING: eight maternity clinics across the UK. PARTICIPANTS: pregnant women (n=574) attending an appointment for DS screening, NIPT or invasive testing between December 2013 and September 2014. MEASUREMENTS: using data collected from the questionnaires we calculated the total costs to women by multiplying the time spent at the hospital and travelling to and from it by the opportunity costs of the women and accompanying person and adding travel and childcare costs. Assumptions about the value of opportunity costs were tested in one-way sensitivity analyses. The main outcome measure was the mean cost to the women and friends/family for each test (DS screening, NIPT, and invasive testing). FINDINGS: mean costs to women and their family/friend were £33.96 per visit, of which £22.47 were time costs, £9.15 were travel costs and £2.34 were childcare costs. Costs were lowest for NIPT (£22), £32 for DS screening (£44 if combined with NIPT), and highest for invasive testing (£60). Sensitivity analysis revealed that variations around the value of leisure time opportunity costs had the largest influence on the results. KEY CONCLUSIONS: there are considerable costs to women, their friends and family when attending different tests in the DS screening pathway. IMPLICATIONS FOR PRACTICE: when assessing the cost-effectiveness of changes to this pathway, costs to women should be considered

Electrophysiological correlates of the BOLD signal for EEG-informed fMRI

EEG and fMRI are important tools in cognitive and clinical neuroscience. Combined EEGfMRI has been shown to help to characterise brain networks involved in epileptic activity, as well as in different sensory, motor and cognitive functions. A good understanding of the electrophysiological correlates of the blood oxygen level dependent (BOLD) signal is necessary to interpret fMRI maps, particularly when obtained in combination with EEG. We review the current understanding of electrophysiological-haemodynamic correlates, during different types of brain activity. We start by describing the basic mechanisms underlying EEG and BOLD signals, and proceed by reviewing EEG-informed fMRI studies using fMRI to map specific EEG phenomena over the entire brain (“EEG-fMRI mapping”), or exploring a range of EEGderived quantities to determine which best explain co-localised BOLD fluctuations (“local EEG-fMRI coupling”). While reviewing studies of different forms of brain activity (epileptic and non-epileptic spontaneous activity; cognitive, sensory and motor functions), a significant attention is given to epilepsy because the investigation of its haemodynamic correlates is the most common application of EEG-informed fMRI. Our review is focused on EEG-informed fMRI, an asymmetric approach of data integration. We give special attention to the invasiveness of electrophysiological measurements and the simultaneity of multimodal acquisitions because these methodological aspects determine the nature of the conclusions that can be drawn from EEG-informed fMRI studies. We emphasise the advantages of, and need for, simultaneous intracranial EEG-fMRI studies in humans, which recently became available and hold great potential to improve our understanding of the electrophysiological correlates of BOLD fluctuations