AN ULTRA WIDEBAND (UWB) MICROSTRIP PATCH ANTENNA
PATHMANATHAN A/L CHINNAN NADESON
A project report submitted in partial fulfillment of the requirements for the award of the degree of Master of Engineering (Electrical - Electronics and
Telecommunications).
Faculty of Electrical Engineering Universiti Teknologi Malaysia
DECEMBER 2006
iii
ACKNOW LEDGM ENT
The author would like to extend his appreciation to Dr. Mohamad Kamal bin
Abdul Rahim for his kind assistance, supervision and guidance in the completion of
this project. The writer would also like to greatly thank En. Thelaha bin Masri for
his kind assistance in the completion of this project.
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ABSTRACT
Rapid changes in the field of wireless communications has to an increasing
demand of higher data transfer rate and even higher bandwidths to supplement
existing operating frequencies. The UWB band is an area of interest due to the fact
that it can accommodate higher data transfer rate on a large bandwidth. One of the
issues faced in the use of this band is the antenna design issue. A cost effective
hexagonal microstrip design with a partial ground plane is presented here. This
design was able to achieve a return loss of < - 8 dB in the 3.1 to 10.6 GHz band and
exhibited an uniform radiation profile at frequencies of 3, 5, 7, and 9 GHz.
v
ABSTRAK
Kemajuan deras dalam bidang komunikasi tanpa wayar telah mewujudkan
permintaan untuk kadar pertukaran data yang tinggi, dan juga jalur frekuensi yang
lebar sebagai tambahan kepada frekuensi yang sedia ada. Jalur UWB mendapat
minat kerana ia dapat memberi kadar pertukaran data yang tinggi di atas jalur yang
lebar. Antara isu tentang penggunaan jalur UWB adalah rekabentuk antenna. Satu
rekabentuk mikrostrip heksagon dengan separa “ground plane” telah dianalisa.
Rekabentuk ini telah memberikan “return loss” yang kurang daripada - 8 dB dalam
julat frekuensi 3.1 GHz dan 10.6 GHz. Rekabentuk ini telah juga menunjukkan
profil radiasi yang seragam pada frekuensi - frekuensi 3, 5, 7 dan 9 GHz.
vi
CONTENTS
CHAPTER TOPIC PAGE
DECLARATION ii
ACKNOW LEDGEM ENT iii
ABSTRACT iv
ABSTRAK v
CONTENTS vi
LIST OF TABLES x
LIST OF DIAGRAMS xi
1 INTRODUCTION 1
1.1 Ultra Wideband Antenna Design 1
1.2 Objective 2
1.3 Scope 3
1.4 Thesis Outline 3
1.5 Summary 4
2 LITERATURE REVIEW 5
2.1 Antenna Basics 5
2.2 The Microstrip Patch Antenna 5
2.2.1 Feeding Mechanisms 6
2.2.2 Bandwidth Enhancement Techniques 7
2.3 Ultra Wideband (UWB) Basics 8
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2.4 Antenna Parameters 9
2.4.1 Return Loss 9
2.4.2 Bandwidth 10
2.4.3 Directivity and Gain 10
2.4.4 Radiation Pattern 10
2.4.5 Polarisation 11
2.5 Previous Work on UWB Antenna 11
2.5.1 Knight’s Helm Shaped Antenna 11
2.5.2 Rectangular Microstrip Patch with 2 steps 13
and a Single Slot
2.5.3 Double - Sided Printed Bow - Tie 14
Antenna for UWB Communications
2.5.4 P ro b e-F ed Stacked Patch Antenna 16
for UWB Sectoral Applications
2.5.5 Microstrip Line and Coplanar 17
Waveguide Fed UWB Slot Antenna
with U - shaped Tuning Stub
2.5.6 Slot Antenna for UWB System 20
2.5.7 Wide Slot Antenna for UWB Applications 22
2.5.8 Ultra-wideband printed elliptical slot 23
Antenna
2.5.9 Bow - Tie Antenna for UWB 24
Communication Frequency
2.6 Summary 25
3 M ETHODOLOGY 26
3.1 Design Difficulties 26
3.2 Dimension Determination 27
3.2.1 Rectangular Patch Model 27
3.3 Choice of Substrate 28
3.4 Computer Simulation 29
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3.4.1 Without a Partial Ground Plane 29
3.4.2 With a Partial Ground Plane 29
3.4.3 Substrate Size as a Variable 30
3.4.4 Addition of a Slot in the Ground Plane 30
3.4.5 Size of Partial Ground Plane as a Variable 31
3.5 Verification 31
3.6 Summary 31
4 RESULTS AND DISCUSSION 33
4.1 Dimension Determination 33
4.2 Simulation Results 34
4.2.1 No Partial Ground Plane 34
4.2.2 With a Partial Ground Plane 38
4.2.3 Substrate Size Enlargement 42
4.2.3.1 120 mm wide substrate 42
4.2.3.2 150 mm wide substrate 46
4.2.3.3 120 x 120 mm2 substrate size 50
4.2.3.4 150 x 150 mm2 substrate size 54
4.2.3.5 200 x 200 mm2 substrate size 58
4.2.4 Slot Addition 62
4.2.4.1 2 x 8 mm2 slot 62
4.2.4.2 4 x 8 mm2 slot 66
4.2.4.3 8 x 8 mm2 slot 70
4.2.4.4 1 6 x 8 mm2 slot 74
4.2.4.5 20 x 8 mm2 slot 78
4.2.5 Effect of Partial Ground Size 82
4.2.5.1 4 mm wide ground plane 82
4.2.5.2 8 mm wide ground plane 86
4.2.5.3 16 mm wide ground plane 90
4.2.5.4 20 mm wide ground plane 94
4.2.5.5 24 mm wide ground plane 98
4.2.5.6 30 mm wide ground plane 102
4.3 Verification 106
4.4 Summary 110
5 CONCLUSION 111
ix
REFERENCES 112
x
LIST OF TABLES
TABLE NUMBER TITLE
4.1 Calculated values of patch dimensions
PAGE
33
xi
LIST OF DIAGRAMS
DIAGRAM NUMBER TITLE PAGE
2.1 Knight’s helm shaped antenna 12
2.2 Rectangular patch antenna with slots and steps 13
2.3 Double sided printed bow - tie antenna 15
2.4 E shaped stacked patch antenna 16
2.5 Patch antenna with microstrip transmission line 18
2.6 Patch antenna with coplanar waveguide 19
2.7 Bow - tie antenna design 21
2.8 Wide slot antenna 22
2.9 Printed elliptical slot antenna 23
2.10 Bow - tie antenna 24
3.1 Rectangular and hexagonal patch antennae 28
4.1 No ground plane simulation return loss parameters 34
4.2 Current flow on patch without any ground plane 35
4.3 3 GHz radiation pattern without a partial ground plane 35
4.4 5 GHz radiation pattern without a partial ground plane 36
4.5 7 GHz radiation pattern without a partial ground plane 36
4.6 9 GHz radiation pattern without a partial ground plane 37
4.7 Patch antenna with partial ground plane 38
4.8 Return loss values with partial ground plane 38
4.9 3 GHz radiation pattern with partial ground plane 39
4.10 5 GHz radiation pattern with partial ground plane 39
4.11 7 GHz radiation pattern with partial ground plane 40
4.12 9 GHz radiation pattern with partial ground plane 40
4.13 Return loss parameters for 120 mm wide substrate 42
4.14 Current flow for 120 mm wide substrate 43
4.15 3 GHz radiation pattern with 120 mm wide substrate 43
4.16 5 GHz radiation pattern with 120 mm wide substrate 44
4.17 7 GHz radiation pattern with 120 mm wide substrate 44
4.18 9 GHz radiation pattern with 120 mm wide substrate 45
4.19 Return loss parameters with 150 mm wide substrate 46
4.20 Current flow with 150 mm wide substrate 47
4.21 3 GHz radiation pattern with 150 mm wide substrate 47
4.22 5 GHz radiation pattern with 150 mm wide substrate 48
4.23 7 GHz radiation pattern with 150 mm wide substrate 48
4.24 9 GHz radiation pattern with 150 mm wide substrate 49
4.25 Return loss parameters with 120 x 120 mm2 substrate 50
4.26 Current flow with 120 x 120 mm2 substrate 51
4.27 3 GHz radiation pattern with 120 x 120 mm2 substrate 51
4.28 5 GHz radiation pattern with 120 x 120 mm2 substrate 52
4.29 7 GHz radiation pattern with 120 x 120 mm substrate 52
4.30 9 GHz radiation pattern with 120 x 120 mm2 substrate 53
4.31 Return loss parameters with 150 x 150 mm2 substrate 54
4.32 Current flow with 150 x 150 mm substrate 55
4.33 3 GHz radiation pattern with 150 x 150 mm2 substrate 55
4.34 5 GHz radiation pattern with 150 x 150 mm2 substrate 56
4.35 7 GHz radiation pattern with 150 x 150 mm2 substrate 56
4.36 9 GHz radiation pattern with 150 x 150 mm2 substrate 57
4.37 Return loss parameters with 200 x 200 mm2 substrate 58
4.38 Current flow with 200 x 200 mm2 substrate 59
4.39 3 GHz radiation pattern with 200 x 200 mm2 substrate 59
4.40 5 GHz radiation pattern with 200 x 200 mm2 substrate 60
4.41 7 GHz radiation pattern with 200 x 200 mm2 substrate 60
4.42 9 GHz radiation pattern with 200 x 200 mm2 substrate 61
4.43 Return loss parameters with 2 x 8 mm2 slot 62
4.44 Current flow with 2 x 8 mm2 slot 63
4.45 3 GHz radiation pattern with 2 x 8 mm2 slot 63
4.46 5 GHz radiation pattern with 2 x 8 mm slot 64
4.47 7 GHz radiation pattern with 2 x 8 mm2 slot 64
4.48 9 GHz radiation pattern with 2 x 8 mm2 slot 65
4.49 Return loss parameters with 4 x 8 mm2 slot 66
4.50 Current flow with 4 x 8 mm2 slot 67
4.51 3 GHz radiation pattern with 4 x 8 mm2 slot 67
4.52 5 GHz radiation pattern with 4 x 8 mm2 slot 68
4.53 7 GHz radiation pattern with 4 x 8 mm2 slot 68
4.54 9 GHz radiation pattern with 4 x 8 mm2 slot 69
4.55 Return loss parameters with 8 x 8 mm2 slot 70
4.56 Current flow with 8 x 8 mm2 slot 71
4.57 3 GHz radiation pattern with 8 x 8 mm slot 71
4.58 5 GHz radiation pattern with 8 x 8 mm2 slot 72
4.59 7 GHz radiation pattern with 8 x 8 mm2 slot 72
4.60 9 GHz radiation pattern with 8 x 8 mm2 slot 73
4.61 Return loss parameters with 16 x 8 mm2 slot 74
4.62 Current flow with 16 x 8 mm slot 75
4.63 3 GHz radiation pattern with 16 x 8 mm2 slot 75
4.64 5 GHz radiation pattern with 16 x 8 mm2 slot 76
4.65 7 GHz radiation pattern with 16 x 8 mm slot 76
4.66 9 GHz radiation pattern with 16 x 8 mm2 slot 77
4.67 Return loss parameters with 20 x 8 mm2 slot 78
4.68 Current flow with 20 x 8 mm2 slot 79
4.69 3 GHz radiation pattern with 20 x 8 mm2 slot 79
4.70 5 GHz radiation pattern with 20 x 8 mm2 slot 80
4.71 7 GHz radiation pattern with 20 x 8 mm2 slot 80
4.72 9 GHz radiation pattern with 20 x 8 mm2 slot 81
4.73 Return loss parameters with 4 mm wide ground plane 82
4.74 Current flow with 4 mm wide ground plane 83
4.75 3 GHz radiation pattern with 4 mm wide ground plane 83
4.76 5 GHz radiation pattern with 4 mm wide ground plane 84
4.77 7 GHz radiation pattern with 4 mm wide ground plane 84
4.78 9 GHz radiation pattern with 4 mm wide ground plane 85
4.79 Return loss parameters with 8 mm wide ground plane 86
4.80 Current flow with 8 mm wide ground plane 87
4.81 3 GHz radiation pattern with 8 mm wide ground plane 87
4.82 5 GHz radiation pattern with 8 mm wide ground plane 88
4.83 7 GHz radiation pattern with 8 mm wide ground plane 88
4.84 9 GHz radiation pattern with 8 mm wide ground plane 89
4.85 Return loss parameters with 16 mm wide ground plane 90
4.86 Current flow with 16 mm wide ground plane 91
4.87 3 GHz radiation pattern with 16 mm wide ground plane 91
4.88 5 GHz radiation pattern with 16 mm wide ground plane 92
4.89 7 GHz radiation pattern with 16 mm wide ground plane 92
4.90 9 GHz radiation pattern with 16 mm wide ground plane 93
4.91 Return loss parameters with 20 mm wide ground plane 94
4.92 Current flow with 20 mm wide ground plane 95
4.93 3 GHz radiation pattern with 20 mm wide ground plane 95
4.94 5 GHz radiation pattern with 20 mm wide ground plane 96
4.95 7 GHz radiation pattern with 20 mm wide ground plane 96
4.96 9 GHz radiation pattern with 20 mm wide ground plane 97
4.97 Return loss parameters with 24 mm wide ground plane 98
4.98 Current flow with 24 mm wide ground plane 99
4.99 3 GHz radiation pattern with 24 mm wide ground plane 99
4.100 5 GHz radiation pattern with 24 mm wide ground plane 100
4.101 7 GHz radiation pattern with 24 mm wide ground plane 100
4.102 9 GHz radiation pattern with 24 mm wide ground plane 101
4.103 Return loss parameters with 30 mm wide ground plane 102
4.104 Current flow with 30 mm wide ground plane 103
4.105 3 GHz radiation pattern with 30 mm wide ground plane 103
4.106 5 GHz radiation pattern with 30 mm wide ground plane 104
4.107 7 GHz radiation pattern with 30 mm wide ground plane 104
4.108 9 GHz radiation pattern with 30 mm wide ground plane 105
4.109 Front view of hexagonal patch antenna 106
4.110 Reverse view of hexagonal patch antenna 106
xv
4.111 Output of spectrum analyzer 107
4.112 Simulated results 107
4.113 Photo of the anechoic chamber 108
4.114 Photo of the patch antenna prior to measurements 108
4.115 Radiation plot of the E - field 109
4.116 Radiation plot of the H - field 109
CHAPTER 1
INTRODUCTION
1.1 ULTRA WIDEBAND ANTENNA DESIGN
The growing use of wireless devices has forced the need of larger
bandwidths. As a result of this, larger bit rates or the use of different standards
using different frequency bands have been proposed (Yazdandoost and Kohno,
2004). The ultra wideband (UWB) has attracted interest because it can realize a bit
rate of several hundred Mbps.
Antennas are a challenging part of UWB technology. Antennas need to be
specifically designed and optimized for the task. Normal wideband antennas will
not transmit fast transients because they have not been corrected for dispersions
since an important consideration for transient antenna is minimising both frequency
and spatial dispersion. Conventional antennae are designed only to radiate over
relatively narrow range of frequencies used in conventional narrow band systems,
which is with a fractional bandwidth of no more than about 25 %. If an impulse is
fed to such an antenna it tends to ring, severely distorting the pulse and spreading it
out in time. A variety of ultra - broadband antennae exist for many years, including
2
the log periodic antenna and spiral antennae, but these antennae are unsuitable for
short pulse applications since both these antennae transmit different frequency
components from different parts of the antenna that distorts and stretches out the
radiated waveform. In addition, for UWB communications applications, there is a
great need for omni - directional, radiation efficient, low - cost, easy to manufacture
antenna, which should have stable UWB response as well.
1.2 OBJECTIVE
The objective of this project is to design, simulate and fabricate a hexagonal
microstrip patch antenna capable of operating in the 3.1 GHz to 10.6 GHz
bandwidth. This bandwidth is synonymous with the Ultra Wideband (UWB)
bandwidth. The basic requirement of this antenna is that it should exhibit a return
loss of less than - 10 dB in the operating frequency range. A return loss of less than
- 10 dB indicates that at least 90 percent of the power (energy) is transmitted and the
remainder is reflected. This value also corresponds to a Voltage to Standing Wave
Ratio (VSWR) of approximately 2 : 1 . The hexagonal design is chosen since a
similar design for an edge feed microstrip hexagonal monopole exhibits return loss
values of less than - 10 dB in the UWB range as reported (Kumar and Ray, 2003).
In addition, since the hexagon is geometrically similar to a circle, the radiation
pattern will also be similar to that of a circular microstrip patch.
3
1.3 SCOPE
As mentioned in the section 1.2 above, the purpose of this project is to
design, simulate, fabricate and verify the simulation results of a hexagonal
microstrip patch antenna for UWB use. The hexagonal patch would be the basic
design for the microstrip patch antenna. In this project, the commercially available
AWR Microwave Office electromagnetic simulation tool was used. This tool is
capable of generating radiation patterns of the electric field (E - field) and magnetic
field (H - field) for selected frequencies as well as plotting return loss values for the
S(1,1) port parameters in the desired operating frequency range. In addition, current
flow patterns would also be simulated. The design that exhibits the optimum return
loss and radiation pattern was fabricated and tested using a Marconi network
analyzer to compare the computer simulated results with the results obtained in a
laboratory environment to conclude on its suitability for UWB use.
1.4 TH ESIS OUTLINE
This thesis is divided into 5 chapters. The first chapter outlines the objective
and scope of the project. The second chapter explains on some basic fundamentals
of UWB technology, including antenna parameters and previous work on UWB
antennae. The third chapter explains the methodology used in this work from
simulation to fabrication and testing. The fourth chapter presents the obtained
results from simulation and testing. The fifth and final chapter provides the
conclusion and suggests some future recommendations.
1.5 SUMMARY
This chapter presented the one of the problems faced in the use of UWB
technology, particularly the design of UWB antennae. This chapter also discussed
the objective and scope of this project outlined what will be presented in this thesis.
4
112
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