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Antenna System (antenna + system)

Distribution by Scientific Domains

Engineering	70%
Chemistry	11%

Selected Abstracts

Pyrene-Excimers-Based Antenna Systems

CHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2009
Stefano Cicchi Dr.
Abstract A series of dendrimeric compounds bearing pyrene units were synthesized to afford light-harvesting antennae based on the formation of intramolecular excimers. The synthetic plan profited from the efficiency of the Huisgen reaction, the 1,3-dipolar cycloaddition of azides and terminal alkynes, which allowed ready assembly of the different building blocks. The three molecular antennae obtained, of increasing generation, revealed efficient energy transfer both in solution and in the solid state. [source]

The onset of downstream movement of juvenile Atlantic salmon, Salmo salar L., in a chalk stream

FISHERIES MANAGEMENT & ECOLOGY, Issue 2 2002
W. D. RILEY
The downstream movements of wild Atlantic salmon, Salmo salar L., from their established feeding territories in the River Itchen, Hampshire, UK, were logged continuously over an 11-month period using a passive integrated transponder (PIT) antenna system. The time of these movements was then related to a number of monitored and calculated environmental parameters. Initial downstream movement of smolts in April was correlated with the onset of darkness, at which time salmon moved from their established feeding territories alone. No relationship was found between the number of smolts migrating and river flow or maximum daily water temperature. The timing of downstream movement of parr between October and March was random with regard to sunset and time of maximum daily water temperature, suggesting the environmental cue that initiates movement may be different outside the spring smolt period. [source]

The performance evaluation of spatial,temporal algorithms in W-CDMA systems

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2005
Shiann-Shiun Jeng
Abstract Differing from FDMA, TDMA, and CDMA, space division multiple access (SDMA) uses space resources to improve communication system performance. Utilizing the smart antenna system is an approach to realize the SDMA technique. Smart antenna systems using the beamforming technique can reduce the co-channel interference and multipath fading to increase the channel capacity and communication quality. In this study the smart antenna system and rake receiver are integrated. The performance of spatial,temporal structure applied to the W-CDMA system is evaluated. From the cumulative distribution function simulation results, W-CDMA system with spatial,temporal algorithm can exactly provide SINR gain to improve the system performance and capacity. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A high-gain dual-band directional/omnidirectional reconfigurable antenna for WLAN systems

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2008
Min Ding
Abstract A high-gain dual-band antenna for the wireless local area network system is presented in this article. Two symmetrical linear arrays can be dynamically reconfigured that could switch radiation pattern with a switchable feed circuit between direction and omnidirection. The antenna can also be used for a pattern diversity antenna for the multiple-input,multiple-output communication systems. The design process for the antenna system is given, and the parameters and characteristics of the antennas are achieved by the method. Measured return losses, isolation, and radiation patterns are in good agreement with the simulated ones, which illustrates that the method is valid and the antenna system can be integrated with pattern reconfigurable and pattern diversity applications. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [source]

High-gain, short-circuited six-monopole-antenna system for concurrent, dual-band WLAN access points

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2010
Saou-Wen Su
Abstract A high-gain, short-circuited multimonopole antenna system for wireless access points in the concurrent 2.4 and 5 GHz WLAN bands is presented. The antenna system mainly comprises a circular antenna ground and six short-circuited, single-band monopole antennas, among which the three antennas are designated for 2.4 and 5 GHz operation respectively. The monopole antennas are set in a sequential, rotating arrangement on the antenna ground, and the 2.4 and 5 GHz antennas are facing each other one by one. Experimental results show that well port isolation can be obtained between the antenna ports with high-gain properties over the 2.4 and 5 GHz bands. A design prototype is elaborated and discussed in the article. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2728,2732, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25588 [source]

A discussion on the performance of impedance matched antenna system and considerations for a better performance

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008
Adnan Kaya
Abstract Impedance matching networks are used extensively in radio communications. In this study, ,-matching circuit has been used as a matching network. The return loss level of several impedance matched microstrip antennas are compared as a function of matching techniques. The ,-matching device is used to construct the antenna tuning units, which is only used to match the front module and the antenna. This circuit impedance region has been investigated analytically under the variable load condition. When the mismatch is occurred, the result is an increase in the energy consumption or transmission quality deterioration. In addition, the input module in antenna system could be damaged if reflection of the signal levels is excessively high. This is interesting application because antennas cannot be considered alone as component with changing electromagnetic properties. The rectangular microstrip antenna was designed at 2.5 GHz frequency by using microstrip feed line. Better return loss level which is ,16.86 dB has been obtained for this antenna using ,-matching circuit. It is shown that theoretical, simulation, and laboratory results are good agreement. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 410,415, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23101 [source]

Three-antenna MIMO system for WLAN operation in a PDA phone

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2006
Kin-Lu Wong
Abstract A multiple input multiple output (MIMO) system using three EMC (electromagnetic compatible) chip antennas in a personal digital assistant (PDA) phone is demonstrated. The three EMC chip antennas are mounted at three corners of the system ground plane of the PDA phone and all generate a wide bandwidth covering the wireless local area network (WLAN) operation in the 2.4-GHz band (2400,2484 MHz). By adding a T-shaped shorted strip in the proposed MIMO antenna system, large improvements in the isolation (S12, S13, and S23 all less than ,20 dB) between any two antennas of the MIMO system are achieved. Detailed effects of the T-shaped shorted strip on the isolation improvement in the proposed MIMO antenna system are analyzed. Radiation characteristics of the three antennas are also studied. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1238,1242, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21665 [source]

Explicit formulas for obtaining the radiation characteristics of an antenna based on a three-dimensional metallic photonic bandgap structure

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2001
Sailing He
Abstract An antenna based on a three-dimensional metallic photonic bandgap (MPBG) structure consisting of many parallel metallic short wires is considered. An explicit method is introduced to calculate the radiation pattern for such an antenna system. The explicit method is verified numerically by comparing the results obtained by the finite-difference time-domain method. The present method improves the computation speed significantly. A genetic algorithm is used to make an optimal design for such a 3-D MPBG structure-based antenna. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 376,381, 2001. [source]

Energy Collection, Transport, and Trapping by a Supramolecular Organization of Dyes in Hexagonal Zeolite Nanocrystals,

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2006
C. Minkowski
Abstract The incorporation of guest molecules into the cavities of molecular sieves leads to a large variety of highly interesting materials. Zeolite,L,an aluminosilicate with one-dimensional channels of open diameter 7.1,Å,is a very versatile material for building highly organized host,guest systems. We present materials where organic dye molecules have been incorporated into the channels of zeolite,L by means of diffusion, to build artificial photonic antenna systems. The channel entrance can be plugged by adding closure molecules that then connect the guest molecules inside with materials or molecules outside of the zeolite channels, since they can act as extensions of the interior of the zeolite crystal. The photophysical processes taking place in such dye-loaded zeolite,L antennae can be studied either on single-micrometer- or submicrometer-sized crystals or on crystals dispersed in a solvent or coated as thin layers on a support. The energy-transfer process occurring is of the Förster-type, and its transfer rate can be tuned by separating the donor dyes and the acceptor dyes locally by varying amounts of spacer molecules. The distribution of the dye molecules and empty sites within a zeolite crystal has been modeled by means of a Monte Carlo simulation. The Förster energy migration and transfer steps are described as a random walk. [source]

The performance evaluation of spatial,temporal algorithms in W-CDMA systems

Experimental studies of direction of arrivals using a smart antenna testbed in wireless communication systems

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2003
Shiann-Shiun Jeng
Abstract This paper presents some preliminary results from experimental studies on space-division-multiple-access (SDMA) for wireless communications. A smart antenna system utilizing direction-of-arrival (DOA)-based beamforming techniques can enhance signal quality by reducing co-channel interference from mobiles located at angles spatially distinct from the base station. Adopting both smart uplink and downlink beamforming, a communication system with an antenna array can increase the cell coverage of a base station and significantly boost capacity compared with conventional antenna systems. However, successful implementation of DOA-based beamforming techniques depends on the DOA characteristics. This paper presented the feasibility of direction finding and DOA variation with respect to frequency. Furthermore, the angle spread was studied for selected environments. The results demonstrate the feasibility of applying proposed smart antenna system utilizing DOA-based beamforming algorithm for increasing channel capacity and improving system performance in frequency-division-duplex (FDD) wireless communication systems. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Investigating the performance of MIMO systems from an electromagnetic perspective

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2006
Marek E. Bialkowski
Abstract Multiple input multiple output (MIMO) wireless systems use multiple element antennas (MEAs) at the transmitter (TX) and the receiver (RX) in order to offer improved information rates (capacity) over conventional single antenna systems in rich scattering environments. In this paper, an example of a simple MIMO system is considered in which both antennas and scattering objects are formed by wire dipoles. Such a system can be analyzed in the strict electromagnetic (EM) sense and its capacity can be determined for varying array size, interelement spacing, and distributions of scatterers. The EM model of this MIMO system can be used to assess the validity of single- or double-bounce scattering models for mixed line of sight (LOS) and non-line of sight (NLOS) signal-propagation conditions. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1233,1238, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21664 [source]

Fast Gaussian beam technique for the analysis of composite horn-reflector antenna systems

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2004
L. Lucci
Abstract A fast and accurate procedure for the analysis of composite horn-reflector antenna systems with electrically large dimensions is here presented. The horn analysis is carried out exploiting the mode matching (MM) and the combined field-integral equation (CFIE) techniques. For the reflector characterization a PO-based Gaussian beam asymptotic technique is used. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 95,100, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20219 [source]

Antenna performance analysis for decameter solar radio observations

ASTRONOMISCHE NACHRICHTEN, Issue 7 2009
A.A. Stanislavsky
Abstract Decameter wavelength radio emission is finely structured in solar bursts. For their research it is very important to use a sufficient sensitivity of antenna systems. In this paper we study an influence of the radiotelescope-antenna effective area on the results of decameter solar radio observations. For this purpose we compared the solar bursts received by the array of 720 ground-based dipoles and the single dipole of the radiotelescope UTR-2. It is shown that a larger effective area of the ground-based antenna allows us to measure a weaker solar emission and to distinguish a fine structure of strong solar events. This feature has been also verified by simultaneous ground- and space-based observations in the overlapping frequency range (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Multi-Colour Electroluminescence of Dendronic Antennae Containing Pyrenes as Light Harvesters

CHEMPHYSCHEM, Issue 3 2010
Umberto Giovanella Dr.
Abstract Dendronic antennae systems containing pyrene units as energy donors and a styrylpyridinium derivative as energy acceptor show efficient energy transfer from the green-emitting pyrene excimer to the red-emitting acceptor. For the third dendron generation the effective screening of the pyrene units on the acceptor provides thin films showing bright red emission. Single-layer light-emitting diodes prepared by properly balancing the dendrons and donor units concentration in polyvinylcarbazole show electroluminescence from the blue, green and red components of the monomeric donor, the donor excimer and the acceptor when excitons are generated in the polymer and subsequently transferred to the molecules by resonant energy transfer. [source]