Design and Development of Multiband Antennas

120 Pages·2015·4.5 MB·English

by  Kiersten Spies

DESIGN AND DEVELOPMENT OF MULTIBAND ANTENNAS FOR
PORTABLE DEVICES WITH MIMO IMPLEMENTATION
_______________
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
Bhakti Joshi
Spring 2015

iii
Copyright © 2015
by
Bhakti Joshi
All Rights Reserved
iv
DEDICATION

Almigthy and my family
v
ABSTRACT OF THE THESIS
Design and Development of Multiband Antennas for Portable
Devices with MIMO Implementation
by
Bhakti Joshi
Master of Science in Electrical Engineering
San Diego State University, 2015

The goal of this thesis is to design and develop a multiband antenna which can be
used in portable devices such as tablets. The antennas cover majority of practical wireless
communication bands. The antennas were also implemented in MIMO (multiple input
multiple output) configuration to increase the data throughput. The antennas show near
omnidirectional patterns as well as acceptable antenna efficiency which is essential for any
wireless communication system. Full wave analysis of antennas was performed using Ansys
High Frequency Structure Simulator (HFSS) v15 software. First of all, two multiband printed
loop antennas covering lower GSM 850MHz (824-890MHz), GSM 900MHz (880-960MHz)
frequency bands and higher GSM 1800MHz (1710-1880MHz), GSM 1900MHz (1850-
1990MHz), UMTS 2100MHz(1920-2170MHz), LTE 700MHz (698-787MHz), LTE
2300MHz (2305-2400MHz), LTE 2500MHz (2500-2690MHz), Wi-Fi 2.4GHz (2400-
2483.5MHz) communications bands were designed and developed on the FR4 printed circuit
board (PCB). To evaluate the performance, the antenna was conceptualized and simulated on
a small ground plane size. Various simulation results such as impedance matching, 2D/3D
radiation patterns, antenna efficiency, peak gain, etc., are included for the antennas. Once the
satisfactory results were obtained, it was implemented on a tablet size (241mm X 186mm)
ground plane.
Studies were also performed on 2X2 MIMO arrangement on the same circuit space.
The envelope correlation coefficient (ECC) was calculated using S-parameters as well as
radiation pattern measurement based techniques. Other parameters necessary for MIMO
performance such as total active reflection coefficient (TARC), channel capacity, mean
effective gain (MEG), capacity loss were also computed based on the simulated and
measured data for the final antenna selection. The 2X2 MIMO antenna was prototyped, and
experimentally verified to validate the simulation results. Available discrepancy between the
simulated and measured results is due to the fabrication and measurement errors.
vi
TABLE OF CONTENTS
PAGE
ABSTRACT ...............................................................................................................................v
LIST OF TABLES ................................................................................................................. viii
LIST OF FIGURES ................................................................................................................. ix
ACKNOWLEDGEMENTS ................................................................................................... xiv
CHAPTER
1 INTRODUCTION .........................................................................................................1
1.1 Background ........................................................................................................1
1.2 Motivation of Research ......................................................................................2
1.3 Microstrip Antenna ............................................................................................3
1.3.1 Advantages and Limitation of Patch Antenna ..........................................4
1.3.2 Microstrip Patch Antennas Theory ...........................................................5
1.4 Literature Review...............................................................................................7
1.5 Designing and Fabrication Tools Methodology ..............................................15
1.6 Organization of the Thesis ...............................................................................20
2 THEORY OF MONOPOLE AND LOOP ANTENNA...............................................22
2.1 Conventional Wire Monopole Antenna ...........................................................22
2.1.1 Effect of Ground Plane on Monopole Antenna ......................................23
2.1.2 Planar Monopole Antenna ......................................................................24
2.1.3 Design of Single Monopole Antenna in HFSS .......................................25
2.2 Conventional Loop Antenna ............................................................................27
2.2.1 Small Loop Antenna ...............................................................................28
2.2.2 Large Loop Antenna ...............................................................................29
3 INTRODUCTION TO MIMO THEORY ...................................................................31
3.1 Introduction ......................................................................................................31
3.2 MIMO Benefits ................................................................................................32
3.3 Diversity Techniques .......................................................................................32
3.3.1 Different Diversity Techniques...............................................................33
vii
3.3.2 Two Main Formats of MIMO .................................................................33
3.4 MIMO System Modal ......................................................................................33
3.5 MIMO Performance Measures ........................................................................36
3.5.1 Antenna Correlation Coefficient .............................................................36
3.5.1.1 Radiation Pattern Measurement Based ..........................................37
3.5.1.2 S-Parameter Based .........................................................................37
3.5.2 Mean Effective Gain (MEG) ..................................................................38
3.5.3 Total Active Reflection Coefficient (TARC) .........................................38
3.5.4 Channel Capacity ....................................................................................38
3.5.5 Capacity Loss ..........................................................................................38
4 SINGLE ANTENNA ELEMENT ...............................................................................39
4.1 Antenna Design 1 Covering High Frequency Band ........................................40
4.2 Antenna Design 2 Covering High Frequency Bands .......................................46
4.3 Antenna Design Covering Low Frequency 4G Band ......................................60
5 2X2 MIMO ANTENNA DESIGN ON TABLET .......................................................65
6 FABRICATION AND MEASUREMENT..................................................................83
7 CONCLUSION AND FUTURE STUDIES ..............................................................103
REFERENCES ......................................................................................................................105
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LIST OF TABLES
PAGE
Table 1.1. Different Communication Bands Chart ....................................................................2
Table 4.1. Antenna Impedance Bandwidth and Various Applications Covered .....................44
Table 4.2. Design Parameters and Measurement of the Proposed Antenna Element ..............54
Table 4.3. Antenna Impedance Bandwidth and Various Applications Covered .....................58
Table 4.4. Design Dimension for the Monopole Antenna .......................................................62
Table 5.1. Mean effective gain data for XPD = 1 and XPD = 0.5 (a) antenna 1 and
antenna 2 at 1.8GHz and 2.5GHz (b) antenna 3 and antenna 4 at 0.7GHz and
0.8GHz. ........................................................................................................................82
ix
LIST OF FIGURES
PAGE
Figure 1.1. Structure of microstrip patch antenna (HFSS Modal). ............................................4
Figure 1.2. Common shapes of microstip patch antenna. ..........................................................4
Figure 1.3. Basic configuration of microstrip patch antenna. ....................................................6
Figure 1.4. Side view of microstrip patch antenna (field distribution beneath the
patch)..............................................................................................................................7
Figure 1.5. (a) Planar monopole antenna geometry (b) simulated return loss (S11). ................8
Figure 1.6. 2 x 2 MIMO antenna simulated and fabricated modal. ...........................................9
Figure 1.7. Comparison of the measured and simulated reflection coefficient
magnitude of the upper and lower two antenna. ..........................................................10
Figure 1.8. (a) MIMO antenna geometry (b) reflection coefficient measurements of
fabricated 2 X 1 MIMO antenna. .................................................................................11
Figure 1.9. Printed loop antenna geometry and its return loss plot. ........................................12
Figure 1.10. MIMO antenna geometry size (230 x 176 x 0.8 mm3) and its simulated
and measured return loss plot. .....................................................................................13
Figure 1.11. (a) MIMO antenna geometry with the wave trap slot and (b) simulated
and measured S-parameter. ..........................................................................................14
Figure 1.12. (a) Geometry of printed antenna shown on mobile size ground plane and
(b) simulated and measured return loss plot. ...............................................................16
Figure 1.13. (a) Simulated antenna on a 150mm x 150mm size ground plane and (b)
enlarge view of reconfigurable loop antenna. ..............................................................17
Figure 1.14. (a) Fabricated antenna model showing the DTV antenna #1, and
frequency reconfigurable antennas #2 and #3 and (b) comparison of simulated
and measured S11 with -6dB criteria. ..........................................................................18
Figure 1.15. Finite element tetrahedron. ..................................................................................19
Figure 2.1. Quarter wave monopole antenna. ..........................................................................23
Figure 2.2. Configuration of quarter wave monopole antenna above the virtual ground
plane. ............................................................................................................................24
Figure 2.3. (a) HFSS modal of monopole antenna along with ground plane and
excitation (b) enlarge view of monopole antenna. .......................................................25
Figure 2.4. Plot of S magnitude vs frequency (-10dB criteria) for a single monopole
11
antenna. ........................................................................................................................26
x
Figure 2.5. Current distribution plot over the surface of the antenna geometry. .....................26
Figure 2.6. 2D and 3D radiation pattern of a single monopole antenna element at
3.25GHz. ......................................................................................................................27
Figure 2.7. Total antenna efficiency over frequency plot. .......................................................27
Figure 2.8. Very small loop. ....................................................................................................28
Figure 2.9. Radial counterpoise layout. ...................................................................................30
Figure 3.1. Basic system modal. ..............................................................................................34
Figure 3.2. Representation of the channel matrix coefficients. ...............................................34
Figure 4.1. Loop antenna geometry along with the ground plane (HFSS Modal). ..................40
Figure 4.2. Enlarge view of the printed loop antenna with dimensions (HFSS Modal). .........41
Figure 4.3. Variation of reflection coefficient (S11) vs. frequency with a -6 dB
criteria. .........................................................................................................................41
Figure 4.4. Same loop antenna geometry with addition of stub (HFSS Modal). .....................42
Figure 4.5. Variation of reflection coefficient (S11) vs. frequency with a -6 dB criteria
with addition of the stub. .............................................................................................42
Figure 4.6. Effect of variation of stub on reflection coefficient magnitude (dB). ...................43
Figure 4.7. Variation of reflection coefficient (S11) vs. frequency with a -6 dB
criteria. .........................................................................................................................43
Figure 4.8. Scaled geometry of the same loop antenna (HFSS Modal). ..................................44
Figure 4.9. Variation of peak realized gain vs. frequency with a -6 dB criteria for a
single element design. ..................................................................................................45
Figure 4.10. Variation of total antenna efficiency vs. frequency with a -6 dB criteria
for an single element design. .......................................................................................46
Figure 4.11. 2D and 3D radiation pattern plots for single element antenna design: (a)
0.85 GHz, (b) 1.7 GHz, (c) 2.15GHz, (d) 3.54 GHz, (e) 5.64GHz and (f) 2D
and 3D pattern scale and details...................................................................................47
Figure 4.12. Surface current distribution for single element loop antenna design: (a)
0.85 GHz, (b) 1.7GHz, (c) 2.15 GHz, (d) 3.54 GHz and (e) 5.64GHz. .......................50
Figure 4.13. Top view of the simulated simple loop structure. ...............................................53
Figure 4.14. Antenna element design parameters. ...................................................................53
Figure 4.15. Simulated S11 for single loop antenna. ...............................................................54
Figure 4.16. Variation of total antenna efficiency vs. frequency with a -6 dB criteria
for a single element design. .........................................................................................54
Figure 4.17. Variation of peak realized gain vs. frequency with a -6 dB criteria for a
single element design. ..................................................................................................55