Diversity Characterization of Optimized Two-Antenna Systems for UMTS Handsets
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Research Article Diversity Characterization of Optimized Two-Antenna Systems for UMTS Handsets ´ 2 and P.-S. Kildal3 A. Diallo,1 P. Le Thuc,1 C. Luxey,1 R. Staraj,1 G. Kossiavas,1 M. Franzen, 1 Laboratoire
d’Electronique, Antennes et T´el´ecommunications (LEAT), Universit´e de Nice Sophia-Antipolis, CNRS UMR 6071, 250 rue Albert Einstein, Bˆat. 4, Les Lucioles 1, 06560 Valbonne, France 2 Bluetest AB, Gotaverksgatan 1, 41755 Gothenburg, Sweden 3 Department of Signals and Systems, Chalmers University of Technology, 41296 Gothenburg, Sweden Received 16 November 2006; Revised 20 June 2007; Accepted 22 November 2007 Recommended by A. Alexiou This paper presents the evaluation of the diversity performance of several two-antenna systems for UMTS terminals. All the measurements are done in a reverberation chamber and in a Wheeler cap setup. First, a two-antenna system having poor isolation between its radiators is measured. Then, the performance of this structure is compared with two optimized structures having high isolation and high total efficiency, thanks to the implementation of a neutralization technique between the radiating elements. The key diversity parameters of all these systems are discussed, that is, the total efficiency of the antenna, the envelope correlation coefficient, the diversity gains, the mean effective gain (MEG), and the MEG ratio. The comparison of all these results is especially showing the benefit brought back by the neutralization technique. Copyright © 2007 A. Diallo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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INTRODUCTION
Nowadays, wireless mobile communications are growing exponentially in several fields of telecommunications. The new generation of mobile phones must be able to transfer large amounts of data and consequently increasing the transfer rate of these data is clearly needed. One solution is to implement a diversity scheme at the terminal side of the communication link. This can be done by multiplying the number of the radiating elements of the handset. In addition, these radiators must be highly isolated to achieve the best diversity performance. Also, the antenna engineers must take into account the radiator’s environment of the handset to design suitable multiantenna systems. In practice, the terminal can be considered to operate in a so-called multipath propagation environment: the electromagnetic field will take many simultaneous paths between the transmitter and the receiver. In such a configuration, total efficiency, diversity gain, mean effective gain (MEG), and MEG ratio are the most important parameters for diversity purposes. Only few papers are actually focusing on the design of a specific technique to address the isolation problem of several planar inverted-F antennas (PIFAs) placed on the same finite-sized ground plane and operating in the same fre-
quency bands. In [1, 2], the authors are eval
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