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A Compact Planar MIMO Antenna System of Four Elements With Similar Radiation Characteristics and Isolation Structure
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, 1107-1110 p.Article in journal (Refereed) Published
Abstract [en]

A compact planar multiple-input-multiple-output (MIMO) antenna system of four elements with similar radiation characteristics is proposed for the whole 2.4-GHz WLAN band. It consists of two proximity-coupled fed microstrip square ring patch antennas and two lambda/4 microstrip slot antennas of the same linear polarization. These two types of antennas are printed on different sides of the substrate to reduce mutual coupling. With a novel isolation structure etched on the ground plane of the FR4 substrate, high port isolation (below -25 dB) and good MIMO performance are achieved. The overall lateral size of the MIMO system is only 0.64 lambda X 0.48 lambda, and good impedance matching (S11 < 10 dB) is achieved across the operating band for all the antenna elements. Full spherical radiation patterns are measured for the MIMO system, showing similar radiation characteristics, and the gains are above 2.3 dB across the operating band.

Place, publisher, year, edition, pages
2009. Vol. 8, 1107-1110 p.
Keyword [en]
Compact antenna, isolation technology, multiple-input-multiple-output, (MIMO) systems, wireless LAN
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-18932DOI: 10.1109/lawp.2009.2034110ISI: 000271440900003OAI: diva2:336979
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2013-11-19Bibliographically approved
In thesis
1. Decoupling and Evaluation of Multiple Antenna Systems in Compact MIMO Terminals
Open this publication in new window or tab >>Decoupling and Evaluation of Multiple Antenna Systems in Compact MIMO Terminals
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Research on multiple antenna systems has been a hot topic in recent years due to the demands for higher transmission rate and more reliable link in rich scattering environment in wireless communications. Using multiple antennas at both the transmitter side and the receiver side increases the channel capacity without additional frequency spectrum and transmitted power. However, due to the limited space at the size-limited terminal devices, the most critical problem in designing multiple antennas is the severe mutual coupling among them. The aim of this thesis is to provide compact, decoupled and efficient multiple antenna designs for terminal devices. At the same time, we propose a simple and cost effective method in multiple antenna measurement. All these efforts contribute to the development of terminal devices for the fourth generation wireless communication.

The background and theory of multiple antenna systems are introduced first, in which three operating schemes of multiple antenna systems are discussed. Critical factors influencing the performance of multiple antenna systems are also analyzed in details. To design efficient multiple antenna systems in compact terminals, several decoupling methods, including defected ground plane, current localization, orthogonal polarization and decoupling networks, are proposed. The working mechanism and design procedure of each method are introduced, and their effectiveness is compared. Those methods can be applied to most of the terminal antennas, reducing the mutual coupling by at least 6dB.

In some special cases, especially for low frequency bands below 1GHz, the chassis of the device itself radiates like an antenna, which complicates the antenna decoupling. Thus, we extend the general decoupling methods to the cases when the chassis is excited. Based on the characteristic mode analysis, three different solutions are provided, i.e., optimizing antenna locations, localizing antenna currents and creating orthogonal modes. These methods are applied to mobile phones, providing a more reliable link and a higher transmission rate, which are evaluated by diversity gain and channel capacity, respectively.

In order to measure the performance of multiple antenna systems, it is necessary to obtain the correlation coefficients. However, the traditional measurement technique, which requires the phase and polarization information of the radiation patterns, is very expensive and time consuming. In this thesis, a more practical and convenient method is proposed. Fairly good accuracy is achieved when it is applied to various kinds of antennas.

To design a compact and efficient multiple antenna system, besides the reduction of mutual coupling, the performance of each single antenna is also important. The techniques for antenna reconfiguration are demonstrated. Frequency and pattern reconfigurable antennas are constructed, providing more flexibility to multiple antenna systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xvi, 89 p.
Trita-EE, ISSN 1653-5146 ; 2012:025
Multiple antennas, mutual coupling, compact antennas, frequency reconfigurable antennas, pattern reconfigurable antennas, meta-material antennas, mobile antennas, fractal antennas, collocated antennas, antenna measurement.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-96239 (URN)
Public defence
2012-06-15, H1, Teknikringen 33, KTH, Stockholm, 10:00 (English)
QC 20120604Available from: 2012-06-04 Created: 2012-05-31 Last updated: 2012-06-04Bibliographically approved

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