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Ultrawideband MIMO/Diversity Antennas With a Tree-Like Structure to Enhance Wideband Isolation
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0002-3401-1125
2009 (English)In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 8, 1279-1282 p.Article in journal (Refereed) Published
Abstract [en]

A compact printed ultrawideband (UWB) multiple-input-multiple- output (MIMO)/diversity antenna system (of two elements) with a size of 35 40 mm operating at a frequency range of 3.1-10.6 GHz is proposed. The wideband isolation can be achieved through a tree-like structure on the ground plane. The effectiveness of the tree-like structure is analyzed. Measured S-parameters show that the isolation is better than 16 dB (20 dB in most of the band) across the UWB of 3.1-10.6 GHz. The radiation patterns, gain, and envelope correlation coefficient are also measured. The proposed antenna is suitable for some portable MIMO/diversity applications.

Place, publisher, year, edition, pages
2009. Vol. 8, 1279-1282 p.
Keyword [en]
Diversity, isolation, multiple-input-multiple-output (MIMO), ultrawideband (UWB) antennas, diversity antenna
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-19036DOI: 10.1109/lawp.2009.2037027ISI: 000272608300008ScopusID: 2-s2.0-77949530616OAI: diva2:337083

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2013-11-19Bibliographically approved
In thesis
1. Investigating and Enhancing Performance of Multiple Antenna Systems in Compact MIMO/Diversity Terminals
Open this publication in new window or tab >>Investigating and Enhancing Performance of Multiple Antenna Systems in Compact MIMO/Diversity Terminals
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today, owners of small communicating device are interested in transmitting or receiving various multimedia data. By increasing the number of antennas at the transmitter and/or the receiver side of the wireless link, the diversity/Multiple-Input Multiple-Output (MIMO) techniques can increase wireless channel capacity without the need for additional power or spectrum in rich scattering environments. However, due to the limited space of small mobile devices, the correlation coefficients between MIMO antenna elements are very high and the total efficiencies of MIMO elements degrade severely. Furthermore, the human body causes high losses on electromagnetic wave. During the applications, the presence of users may result in the significant reduction of the antenna total efficiencies and highly affects the correlations of MIMO antenna systems. The aims of this thesis are to investigate and enhance the MIMO/diversity performance of multiple antenna systems in the free space and the presence of users.

The background and theory of multiple antenna systems are introduced briefly first. Several figures of merits are provided and discussed to evaluate the multiple antenna systems. The decoupling techniques are investigated in the multiple antenna systems operating at the higher frequencies (above 1.7 GHz) and with high radiation efficiency. The single, dual and wide band isolation enhancements are realized through the half-wavelength decoupling slot, quarter-wavelength decoupling slot with T-shaped impedance transformer, tree-like parasitic element with multiple resonances, as well as the different polarizations and radiation patterns of multiple antennas.

In the lower bands (lower than 960 MHz), due to the low radiation efficiency and strong chassis mode, the work mainly focused on how to directly reduce the correlations and enlarge the total efficiency. A new mode of mutual scattering mode is introduced. By increasing the Q factors, the radiation patterns of multiple antennas are separated automatically to reduce the correlations. With the inter-element distance larger than a certain distance, a higher Q factor also improved the total efficiency apart from the low correlation. A wideband LTE MIMO antenna with multiple resonances is proposed in mobile terminals. The high Q factors required for the low correlation and high efficiencies in mutual scattering mode is reduced with another mode of diagonal antenna-chassis mode. Hence, the bandwidth of wideband LTE MIMO antenna with multiple resonances mentioned above can be further enlarged while maintaining the good MIMO/diversity performance.

The user effects are studied in different MIMO antenna types, chassis lengths, frequencies, port phases and operating modes. Utilizing these usefully information, an adaptive quad-element MAS has been proposed to reduce the user effects and the some geranial rules not limited to the designed MAS have also been given.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 58 p.
Trita-EE, ISSN 1653-5146
Multiple antennas, planar inverted-F antenna, mutual coupling, slot antenna, compact antenna, mobile antenna, Q factors, antenna array, ultra-wideband (UWB) antenna, pattern diversity, polarization diversity, user effects, adaptive arrays, chassis mode
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-116402 (URN)978-91-7501-600-9 (ISBN)
Public defence
2013-01-28, F3, Kungliga Tekniska Högskolan, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
EU Erasmus Mundus External Cooperation Window TANDEM
EU, European Research Council

QC 20130121

Available from: 2013-01-21 Created: 2013-01-18 Last updated: 2013-11-19Bibliographically approved

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