multiband microstrip slot antenna with multiple

138 Pages·2013·11.92 MB·English

MULTIBAND MICROSTRIP SLOT ANTENNA WITH MULTIPLE-
INPUT AND MULTIPLE-OUTPUT (MIMO) IMPLEMENTATION FOR
HANDHELD DEVICES
_______________
A Thesis
Presented to the
Faculty of
San Diego State University
_______________
In Partial Fulfillment
of the Requirements for the Degree
Master of Science
in
Electrical Engineering
_______________
by
Henk Visser II
Spring 2013

iii
Copyright © 2013
by
Henk Visser II
All Rights Reserved
iv
DEDICATION
The Lord, My Virtuous Wife Marilena Visser, My Mother Sharon Visser, and My
Precious Baby Girl to be born May 2013.
v
ABSTRACT OF THE THESIS
Multiband Microstrip Slot Antenna with Multiple-Input and
Multiple-Output (MIMO) Implementation for Handheld Devices
by
Henk Visser II
Master of Science in Electrical Engineering
San Diego State University, 2013

The research included in this thesis develops an antenna with a multiband response
which has acceptable antenna efficiency and near omni-directional patterns. To achieve
higher data transfer rates, a MIMO implementation is also performed. Some of the goals for
the MIMO approach are to achieve the acceptable performance in terms of the envelope
correlation coefficient (ECC), radiations pattern quality and efficiency. All of these items are
important for wireless communications especially handheld mobile applications.
First of all, a multiband microstrip slot antenna is proposed on a printed circuit board
(PCB) of size equivalent to a hand held device, such as a cell phone. Next, a study was
performed to implement this antenna in 2x1 and 2x2 MIMO arrangements on the same
circuit space. The envelope correlation coefficient is examined using the S-parameter
method. Full wave analysis based on the Maxwell Solver simulation tool Ansys/Ansoft High
Frequency Structure Simulator (HFSS) was performed. Impedance matching, 2D and 3D
radiation patterns, gain, and antenna efficiency plots are included for all the antenna
geometries. Antenna with the 2x2 MIMO implementation was also fabricated and
experimentally verified. Experimental results confirm that the measured ECC, impedance
matching and near omni-directional 2D radiation patterns results follow the simulated results
with some discrepancy. Any discrepancy is attributed to the fact that substrate material is
low cost and hence, it does not has so well defined material properties than assumed for the
simulation modeling.
vi
TABLE OF CONTENTS
PAGE
ABSTRACT ...............................................................................................................................v
LIST OF FIGURES ............................................................................................................... viii
ACKNOWLEDGEMENTS ................................................................................................... xiii
CHAPTER
1 INTRODUCTION .........................................................................................................1 
1.1 Background ........................................................................................................1 
1.2 Research Motivation ..........................................................................................3 
1.3 Microstrip Antenna ............................................................................................4 
1.3.1 Advantages and Limitations of Microstrip Antennas ...............................5 
1.3.2 Microstrip Patch Antennas Theory ...........................................................6 
1.3.3 Radiation Mechanism of a Microstrip Antenna ........................................7 
1.3.4 Microstrip Slot Antennas ..........................................................................9 
1.4 Literature Review...............................................................................................9 
1.5 MIMO Antenna System ...................................................................................13 
1.5.1 System Model .........................................................................................15 
1.5.2 MIMO Channel Models ..........................................................................16 
1.5.3 MIMO Performance ................................................................................18 
1.6 Organization of Thesis .....................................................................................19 
2 SINGLE SLOT DESIGN .............................................................................................21 
2.1 Antenna Geometry ...........................................................................................21 
2.2 Simulated Results.............................................................................................22 
3 1X2 MIMO DESIGN ...................................................................................................38 
3.1 Antenna Geometry ...........................................................................................38 
3.2 Simulated Results.............................................................................................41 
4 2X2 MIMO DESIGN ...................................................................................................64 
4.1 Antenna Geometry ...........................................................................................64 
4.2 Simulated Results.............................................................................................67
vii
5 EXPERIMENTAL VERIFICATION ........................................................................109 
6 CONCLUSION AND FUTURE STUDIES ..............................................................121 
REFERENCES ......................................................................................................................123
viii
LIST OF FIGURES
PAGE
Figure 1.1. Multiradio concept utilizing multiband antennas. ...................................................2 
Figure 1.2. Radio system diagram of multiradio laptop computer platform. ............................2 
Figure 1.3. Frequency bands for wireless services and current number of antennas
required. .........................................................................................................................3 
Figure 1.4 (a) Antenna geometry of multiband microstrip antenna using slots.
Antenna dimensions are 40 mm wide by 85 mm for the length (b) S-parameter
in (dB) for multiband microstrip antennas. ....................................................................4 
Figure 1.5. Microstrip patch antenna configuration.. .................................................................5 
Figure 1.6. Common basic microstrip patch antenna shapes.. ...................................................6 
Figure 1.7. Other shapes for microstrip patch antennas.. ...........................................................7 
Figure 1.8. Additional shapes for microstrip patch antennas.. ...................................................7 
Figure 1.9 Rectangular microstrip patch with magnetic current density distribution.
(a) current distribution on radiating slots (b) current distribution on
nonradiating slots. ..........................................................................................................8 
Figure 1.10. Rectangular microstrip patch with equivalent horizontal radiating slots. .............9 
Figure 1.11. Basic printed slot antenna shapes with feed structures. ......................................10 
Figure 1.12. Comparison of patch and slot antennas.. .............................................................10 
Figure 1.13. MIMO spatial multiplexing method that uses different data with multiple
streams between the transmitting and receiving antennas. ..........................................13 
Figure 1.14. MIMO space time coding implementing the used of the same set of data
that is intelligently organized in time. ..........................................................................14 
Figure 1.15. MIMO system model composing of the channel input, the channel
matrix H, the noise n, and the output y.. ......................................................................15 
Figure 1.16. A MIMO channel matrix representation showing the individual channels
elements of the matrix H. .............................................................................................16 
Figure 1.17 A MIMO channel classification that captures the physical and non-
physical models under the deterministic and stochastic categories respectively. ........17 
Figure 2.1. Top view of single element design. .......................................................................22 
Figure 2.2. Side view of single element design showing the FR4 substrate. ...........................22 
Figure 2.3. Detailed view of slot and meandered feed line of single element design. ............23
ix
Figure 2.4. Variation of S11 vs. frequency with a -6 dB criteria. ............................................23 
Figure 2.5. Variation of peak realized gain vs. frequency with a -6 dB criteria for
single element design. ..................................................................................................25 
Figure 2.6. Variation of radiation efficiency vs. frequency with a -6 dB criteria for
single element design. ..................................................................................................25 
Figure 2.7. Variation of total antenna efficiency vs. frequency with a -6 dB criteria for
a single element design. ...............................................................................................26 
Figure 2.8. Antenna performance considering -6 dB matching criteria for a single
element design. ............................................................................................................26 
Figure 2.9. Variation of reflection coefficient (S11) vs. frequency with a -10 dB
criteria. .........................................................................................................................27 
Figure 2.10. Variation of peak realized gain vs. frequency with a -10 dB criteria for a
single element design. ..................................................................................................28 
Figure 2.11. Variation of radiation efficiency vs. frequency with a -10 dB criteria for
a single element design. ...............................................................................................29 
Figure 2.12. Variation of total antenna efficiency vs. frequency with a -10 dB criteria
for a single element design. .........................................................................................29 
Figure 2.13. Antenna performance considering -10 dB matching criteria for a single
element design. ............................................................................................................30 
Figure 2.14. Co-pol and x-pol realized gain (dBi) radiation patterns for the single
element design: (a) 1.92 GHz XZ/YZ cuts; (b) 2.48 GHz XZ/YZ cuts; (c) 2.90
GHz XZ/YZ cuts; (d) 3.22 GHz XZ/YZ cuts. .............................................................31 
Figure 2.15. Current distribution for single element design: (a) 1.92 GHz (b) 2.48
GHz (c) 2.90 GHz (d) 3.22 GHz. .................................................................................34 
Figure 3.1. Top view of the two element design. .....................................................................39 
Figure 3.2. Side view of two element design. ..........................................................................39 
Figure 3.3. Detail of slots - left and right slot dimensions are symmetrical. Position of
the detail is the upper half of the antenna. ...................................................................40 
Figure 3.4. Detailed view of slot and meandered feed line of two element design. ................40 
Figure 3.5. Variation of reflection coefficient vs. frequency with a -6 dB criteria for a
two element design. .....................................................................................................41 
Figure 3.6. Variation of mutual coupling vs. frequency with a -6 dB criteria for a two
element design. ............................................................................................................42 
Figure 3.7. Variation of peak realized gain vs. frequency with a -6 dB criteria for two
element design. ............................................................................................................43 
Figure 3.8. Variation of radiation efficiency vs. frequency with a -6 dB criteria for
two element design. .....................................................................................................44
x
Figure 3.9. Variation of total antenna efficiency vs. frequency with a -6 dB criteria for
a two element design. ...................................................................................................45 
Figure 3.10. Antenna performance considering -6 dB matching criteria for a two
element design. ............................................................................................................45 
Figure 3.11. Variation of reflection coefficient vs. frequency with a -10 dB criteria. ...........46 
Figure 3.12. Variation of mutual coupling vs. frequency with a -10 dB criteria for a
two element design. .....................................................................................................47 
Figure 3.13. Variation of peak realized gain vs. frequency with a -10 dB criteria for a
two element design. .....................................................................................................47 
Figure 3.14. Variation of radiation efficiency vs. frequency with a -10 dB criteria for
a two element design. ...................................................................................................48 
Figure 3.15. Antenna performance considering -10 dB matching criteria for a two
element design. ............................................................................................................49 
Figure 3.16. Variation of envelope correlation vs. frequency for a two element design. ........50 
Figure 3.17. Co-pol and x-pol realized gain (dBi) radiation patterns for the two
element design with antenna #1 being excited: (a) 1.94 GHz XZ/YZ cuts; (b)
2.38 GHz XZ/YZ cuts; (c) 2.84 GHz XZ/YZ cuts; (d) 3.24 GHz XZ/YZ cuts. ..........51 
Figure 3.18. Co-pol and x-pol realized gain (dBi) radiation patterns for the two
element design with antenna #2 being excited: (a) 1.94 GHz XZ/YZ cuts; (b)
2.38 GHz XZ/YZ cuts; (c) 2.84 GHz XZ/YZ cuts; (d) 3.24 GHz XZ/YZ cuts. ..........54 
Figure 3.19. Current distribution for two element design with excitation of antenna
#1: (a) 1.94 GHz (b) 2.38 GHz (c) 2.84 GHz (d) 3.24 GHz. .......................................58 
Figure 3.20. Current distribution for two element design with excitation of antenna
#2: (a) 1.94 GHz (b) 2.38 GHz (c) 2.84 GHz (d) 3.24 GHz. .......................................61 
Figure 4.1. Top view of 4 element design. ..............................................................................65 
Figure 4.2. Side view of 4 element design. ..............................................................................65 
Figure 4.3. Detail of slots - left and right slot dimensions are symmetrical. Position of
the detail is the upper half of the antenna. Bottom half of antenna is all
symmetrical horizontally. ............................................................................................66 
Figure 4.4. Detailed view of slot and meandered feed line of four element design. ...............66 
Figure 4.5. Variation of reflection coefficient vs. frequency with a -6 dB criteria for a
four element design. .....................................................................................................67 
Figure 4.6. Variation of mutual coupling vs. frequency with a -6 dB criteria for a four
element design. ............................................................................................................68 
Figure 4.7. Variation of peak realized gain vs. frequency with a -6 dB criteria for four
element design. ............................................................................................................69