Investigative study on the development of a green UWB antenna

Copyright @ 2010 ISA

Triple band-notched UWB antenna using meandered ground stubs

In this paper, three pairs of meandered ground stubs are used to create a triple band-notched characteristic for a compact planar-monopole antenna used in the ultrawide band (UWB). The three band notches include the IEEE 802.16 (WiMax) band (3.3-3.6 GHz), the lower wireless area network (WLAN) band (5.15-5.35 GHz) and the higher WLAN band (5.725-5.825 GHz). The center frequencies and bandwidths of the notches can be adjusted using the dimensions of the meandered ground stubs. Prototype of the proposed antenna is designed and fabricated. The band-notched characteristics, return loss, radiation patterns, peak gains and efficiencies of the antenna are studied using both computer simulation and measurements. ©2010 IEEE.published_or_final_versionThe 2010 Loughborough Antennas and Propagation Conference (LAPC 2010), Loughborough, U.K., 8-9 November 2010. In Proceedings of LAPC, 2010, p. 341-34

Effects of ground-plane size on planar UWB monopole antenna

Planar monopole antennas have found widespread applications in wireless communication systems. Their advantages of compact size, omnidirectional radiation pattern and wide impedance bandwidth make them good candidates for the designs of ultra-wideband (UWB) antennas. This paper investigates the effects of the dimensions of the rectangular ground-plane on the return loss and efficiency of an elliptical planar monopole antenna for UWB applications. Computer simulation and measurement are carried out on a group of nine antennas with different rectangular ground plane sizes. The simulated and measured results on return loss agree well. However, the simulated and measured efficiencies do not agree well in the lower UWB band. The measured efficiency shows that the efficiency is affected more by the width rather than by the length of the ground plane while the length of the ground plane affects the lower cutoff frequency. © 2010 IEEE.published_or_final_versionThe 2010 IEEE Region 10 International Conference (TENCON 2010), Fukuoka, Japan, 21-24 November 2010. In TENCON (IEEE Region 10 Conference) Proceedings, 2010, p. 422-42

Design of chipless UWB RFID system using A CPW multi-resonator

In this paper, the design of a novel chipless ultra-wideband radio-frequency identification (UWB RFID) system is proposed. The system employs printable uniplanar chipless tags and a pair of high-gain reader antennas. The chipless tag is composed of two UWB monopole antennas, connected by a coplanar waveguide (CPW). The tag's ID is represented by a spectral signature in the UWB frequency range, and is created by a multi-resonator embedded on the coplanar waveguide. The detection of the tag's ID is based on using only the amplitude of the spectral signature, which significantly simplifies the complexity of detection. The reader employs two separate Vivaldi antennas-one for transmitting a vertically polarized signal, and the other for receiving a horizontally polarized signal-to reduce the mutual coupling between the uplink and downlink signals. Further reduction of mutual coupling is achieved by using a copper plate at the reader to separate the uplink and downlink signals. These two proposed methods together reduced the mutual coupling by 20 dB. The chipless RFID tag with eight coplanar waveguide resonators in a group and the reader antennas were designed using computer simulation, and fabricated on Rogers substrates for measurement. The results of studies in an anechoic chamber showed that the proposed UWB RFID system could achieve a reading range of larger than 30 cm, at least three times longer than the maximum distance of a similar system reported by others. This indicated that the proposed system has great potential for short-range item tracking at low cost. © 1990-2011 IEEE.published_or_final_versio

An antenna for UWB and Bluetooth standards with band-notched characteristic

This paper presents the design and results of a small size, integrated Bluetooth and Ultrawideband (UWB) planar monopole antenna with a band-notched characteristic in the WLAN band. The antenna consists of a dual-ring radiator as the primary radiation element for the Bluetooth and UWB bands and a complementary split-ring resonator (CSRR) to produce a notched characteristic at the center frequency of 5.5GHz. The return loss, voltage-standing-wave ratio (VSWR), radiation pattern and peak gain of the antenna are studied by computer simulation and verified by measurements which agree well with the simulation results. © 2009 IEEE.published_or_final_versionThe 2009 IEEE International Conference on Ultra-Wideband (ICUWB 2009), Vancouver, BC., 9-11 September 2009. In Proceedings of ICUWB, 2009, p. 170-17

Band-notched characteristic using meandered ground stubs for compact UWB antennas

In this paper, a pair of meandered ground stubs is used to design a single band-notched characteristic in a compact planar-monopole antenna for ultrawide band (UWB) applications. The single-band notch covers the wireless area network (WLAN) band from 5.15 GHz to 5.825 GHz. The center-notch frequency and notch bandwidth can be adjusted using the dimensions of the meandered ground stubs. Prototype of the proposed antenna is designed, fabricated and studied. The band-notched characteristics, return loss, radiation patterns, peak gains and efficiencies of the antenna are studied using both computer simulation and measurements. © 2010 IEEE.published_or_final_versionThe 2010 IEEE International Conference on Ultra-Wideband (ICUWB), Nanjing, China, 20-23 September 2010. In Proceedings of ICUWB2010, 2010, v. 1, p. 147-15

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

Energy- and flux-budget (EFB) turbulence closure model for the stably stratified flows. Part I: Steady-state, homogeneous regimes

We propose a new turbulence closure model based on the budget equations for the key second moments: turbulent kinetic and potential energies: TKE and TPE (comprising the turbulent total energy: TTE = TKE + TPE) and vertical turbulent fluxes of momentum and buoyancy (proportional to potential temperature). Besides the concept of TTE, we take into account the non-gradient correction to the traditional buoyancy flux formulation. The proposed model grants the existence of turbulence at any gradient Richardson number, Ri. Instead of its critical value separating - as usually assumed - the turbulent and the laminar regimes, it reveals a transition interval, 0.1< Ri <1, which separates two regimes of essentially different nature but both turbulent: strong turbulence at Ri<<1; and weak turbulence, capable of transporting momentum but much less efficient in transporting heat, at Ri>1. Predictions from this model are consistent with available data from atmospheric and lab experiments, direct numerical simulation (DNS) and large-eddy simulation (LES).Comment: 40 pages, 6 figures, Boundary-layer Meteorology, resubmitted, revised versio

ASCOT: a text mining-based web-service for efficient search and assisted creation of clinical trials

Clinical trials are mandatory protocols describing medical research on humans and among the most valuable sources of medical practice evidence. Searching for trials relevant to some query is laborious due to the immense number of existing protocols. Apart from search, writing new trials includes composing detailed eligibility criteria, which might be time-consuming, especially for new researchers. In this paper we present ASCOT, an efficient search application customised for clinical trials. ASCOT uses text mining and data mining methods to enrich clinical trials with metadata, that in turn serve as effective tools to narrow down search. In addition, ASCOT integrates a component for recommending eligibility criteria based on a set of selected protocols