Electrical and Computer Engineering Department-College of Engineering-Sultan Qaboos University
MIMO Antenna for UWB Communications
Ali Hamed AL-Shamsi
Abstract
Ultra Wideband or UWB is a radio technology that can generally be utilized for transmitting and
receiving a large amount of data over an ultra-wide frequency band with very low power and for
short distances. It has some advantages like high data rates, low equipment cost, multipath
immunity and finally ranging and communication at the same time is possible. In all wireless
communication systems, the antenna has an essential role since it is the means by which the
signals are converted from electrical form to electromagnetic wave form. Thus this project is
concerning design of a Multiple-Input Multiple-Output (MIMO) antenna for UWB
communication.
The motivation for this project is that designing of antennas for UWB system is an interesting
field that brings new challenges to antenna designers like achieving a wide impedance bandwidth
and keeping high radiation efficiency. Also meeting the equipment physical constraints like size
and portability is another challenge. Researches proved that some of these challenges can be
resolved by adopting MIMO antenna because using a multiple antenna system serves
accomplishing a diversity gain, a multiplexing gain or array gain and enhances the overall antenna
performance. However there are some challenges in designing a MIMO antenna for a technology
like UWB including reduction of the mutual coupling and the correlations between the elements,
which are considered other motivations in this field.
The developed antennas are intended to be used in applications related to small devices, personal
devices or consumer electronics like mobile handsets, tablet PC’s, laptops, DVD players or
wireless printers or in general indoor WPAN applications. A UWB MIMO antenna was selected
from the literature and developed in two approaches producing two antennas. The Two antennas
were developed and each consists of 2 elements with an overall size of (66×23.5) mm for the first
design and (59×27) mm for the second. The designs are based on parametric analysis for the
geometry of a printed circular disc compact planar antenna, which is a single element selected
from the literature due to its performance and compact size. A time domain solver package was
utilized to carry out the design and simulation of the antenna in the different phases of the project.
The antenna performance including bandwidth, radiation pattern, efficiency, gain, mutual
coupling between the MIMO antenna elements, the envelope correlation and diversity gain are
examined using the same software. In addition MATLAB 7.0 was utilized to examine the Total
Active Reflection Coefficient (TARC) between the antenna elements. The simulations results
showed that the antenna meets almost all the requirements in UWB MIMO antenna for personal
Electrical and Computer Engineering Department-College of Engineering-Sultan Qaboos University
and consumer electronic devices. The first developed antenna operates well though the band 3.4
GHz up to 10.6 GHz and the radiation pattern is almost omnidirectional in E and H fields. The
radiation efficiency reaches 76%. The second developed design supports full UWB bandwidth
from 3.1 to 10.6 and more, with radiation efficiency up to 82%. The envelope correlation for the
first antenna is less than –40 dB throughout the UWB band and the second antenna has
correlation less than –60 dB. For both designs the diversity gain approaches 10 through the entire
UWB bandwidth and TARC is less than –9.5 dB for the first antenna and less then –11 dB for the
second. The proposed antennas are good candidates for the purpose they were designed for and
eligible for many UWB applications in WPAN.