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|Title: ||Study on components for RF MIMO|
|Other Titles: ||She pin duo shu ru duo shu chu xi tong bu jian de yan jiu|
|Authors: ||Zheng, Shaoyong (鄭少勇)|
|Department: ||Department of Electronic Engineering|
|Degree: ||Master of Philosophy|
|Issue Date: ||2008|
|Publisher: ||City University of Hong Kong|
|Subjects: ||MIMO systems.|
|Notes: ||CityU Call Number: TK5103.2 .Z44 2008|
xiii, 111 leaves : ill. 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2008.
Includes bibliographical references.
|Abstract: ||Recent developments in wireless communications have shown that by using
multiple antenna elements at both the transmitter and receiver, it is possible to
substantially increase the capacity of a wireless communication system without
increasing the transmission power and bandwidth. This structure of using multiple
antenna elements is termed a Multiple-Input Multiple-Output (MIMO) system. This
thesis covers different basic microwave components within this Multiple Input Multiple
Output (MIMO) front end, and proposes a novel concept for its implementation.
In the beginning of this thesis, different structures for implementing 3-dB hybrid
couplers are presented. The branch line coupler which is the most common form of
planar quadrature hybrid couplers is reduced in size using a T-shaped slow wave
structure. Another form of hybrid coupler is the patch hybrid coupler which has a
simple structure with the narrow branch lines eliminated. Additionally, the novel dual
band design using stub loading and the broadband design using impedance steps are
proposed to make it versatile for more applications.
In the second part of the thesis a new broadband phase shifter is proposed. The
basic structure comprising of simple open circuit and short circuit stubs provides a
bandwidth of 50% with small variation in phase, while the use of multi section stubs
was found to improve the bandwidth. The wide band phase shifter was designed and
verified to have a bandwidth of about 100% for a maximum phase deviation of ±3.2º,
and maximum insertion loss of 2.1 dB. It was also found that when the structure was
implemented using CBCPW (Conductor Backed Coplanar Waveguide), a broadband
response of 36% was achieved.
Based on the hybrid couplers and phase shifters described previously, several
Butler Matrices were then investigated and presented in the third part of the thesis. A
compact Butler Matrix using size reduced elements together with a novel topology was
proposed, which only occupied 29% of a conventional one without any loss in performance. The novel rectangular patch hybrid couplers and phase shifters were used
to realize a wideband Butler Matrix with flat coupling covering a bandwidth of 24%.
The rectangular patch hybrid coupler optimized using Jumping Gene Evolutionary
Algorithm together with the broadband parallel stubs phase shifters formed a Butler
Matrix that gave even wider bandwidth.
The fourth part of the thesis begins with the novel concept of a broadband
switch-less front end. A new topology which replaces a dummy load of a distributed
power amplifier with a feedback low noise amplifier is presented, and can be used as an
RF front end from 0.8 GHz to 2.6 GHz, negating the need for a switch. RF MIMO front
ends are normally implemented with the beam-forming network such as a Butler Matrix
placed between the amplifiers and antennas. Hence the amplifiers are placed between
the beam-forming network and antennas according to this concept, thus improving the
performance in terms of power loss and noise figure as well as allowing operation for
beam steering or spatial diversity.
Finally, a conclusion is drawn from the research work and a vision for future work
on MIMO front end for use in modern wireless communication systems is given.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b2340595|
|Appears in Collections:||EE - Master of Philosophy |
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