3D PRINTED ANTENNAS: METALIZED PLASTIC
By
Mohd Ifwat Mohd Ghazali

A THESIS
Submitted to
Michigan State University
in partial fulfilment of requirements
for the degree of
Electrical Engineering – Master of Science
2014

ABSTRACT
3D PRINTED ANTENNAS: METALIZED PLASTIC
By
Mohd Ifwat Mohd Ghazali
This thesis introduces the use of 3D printed plastic structures for the fabrication of
antenna structures. Use of 3D printing technology allows for a simple fabrication
technique that is faster and low cost compared with traditional microfabrication
approaches. Two Vivaldi antenna designs are studied first: i) a simple notch antenna
with a radiating slot line cavity and ii) a corrugated Vivaldi with a partially covered cavity.
The corrugations help increase the bandwidth and gain of the Vivaldi antenna. The
antennas show an extremely wide bandwidth of approximately 13 GHz and have a gain
maximum of approximately 12dB. Further modifications were made by adding bilateral
pieces and dielectric focal lens at the radiating end. A larger bandwidth and higher gain
was attained. The dielectric guiding structure in the aperture helps to further improve the
gain both at the lower frequency and higher frequency regions. The integration of
dielectrics in the antenna design is readily achieved using 3D printing. Apart from the
above Vivaldi antenna designs, three other antenna designs were also studied. This
includes a dielectric loaded monopole antenna, a patch antenna and a reconfigurable
Lego-like antenna. Complex 3D antenna structures and novel antenna designs that use
a combination of dielectric and metal regions are studied and these structures can
readily be fabricated using 3D printing.

ACKNOWLEDGEMENTS
First and foremost, I praise God, the almighty for providing me the strength and
His blessing in completing this thesis. I was able to complete this thesis work with
assistance and guidance from several individuals. I would like to take this opportunity by
thanking all who contributed in the completion of this thesis.
I would like to express my deepest gratitude to my advisor, Dr. Premjeet Chahal,
for his excellent motivation, wisdom, commitment and patience. His invaluable help of
constructive comments and suggestions throughout the experimental and thesis works
have contributed to the success of this research.
Secondly, I would like to thank the committee members, Dr. Edward Rothwell
and Dr. Nelson Sepúlveda for their advice and detailed review of my thesis and
providing me great feedback on my research work.
I sincerely thank all my colleagues in the TESLA group, in particular Kyoung Youl
Park, Joshua Myers, Xianbo Yang, Amanpreet Kaur, Nophadon Wiwatcharagoses,
Jennifer Byford and Eleazar Gutierrez for their kindness, help, encouragement and for
their valuable feedback. Also, I would like to acknowledge all of my colleagues from
Electromagnetic Research Group for their help during this research work. I also like to
thank Brian Wright for helping me fabricates all the 3D printed structures without his
help I would not have been able to complete this work.
I am grateful to the Malaysian Government and Islamic Science University of
Malaysia for making it possible for me to study here through a generous fellowship.
Last but not least, my deepest gratitude to my parents, Mohd Ghazali Omar and
Noraini Ismail, my parents-in law, Sheikh Mohd Nasir Sheikh Hassan and Hanizah Abu
iii

Hassan and also my brothers and sisters especially Mohd Amin Ghazali for their
endless love, prayers and encouragement. Also not forgetting my beautiful wife, Raihan
Farhanah Mohamad Hassan who is always there to encourage me and stand by me
through good and bad times. I would like to use this opportunity to thank every person
who in some way has helped me in making this thesis a reality.

iv

TABLE OF CONTENTS

LIST OF FIGURES......................................................................................................... vii
CHAPTER 1 .................................................................................................................... 1
Literature Review ......................................................................................................... 1
1.1 Introduction and Background .......................................................................... 1
1.2 Introduction to 3D Printing Technology ........................................................... 3
1.3 History of 3D Printing Technology................................................................... 9
1.4 Applications of 3D Printing Technology ........................................................ 13
1.5 Electronic Applications .................................................................................. 19
1.6 Motivation and Objectives ............................................................................. 26
1.7 Thesis Layout ............................................................................................... 28
CHAPTER 2 .................................................................................................................. 29
3D Printed Vivaldi Antenna ........................................................................................ 29
2.1 Introduction ................................................................................................... 29
2.2 Antenna Design and Simulation .................................................................... 32
2.3 Fabrication and Measurement ...................................................................... 44
2.4 Conclusion .................................................................................................... 51
CHAPTER 3 .................................................................................................................. 52
Dielectric Loaded Antenna Designs ........................................................................... 52
3.1 Introduction ................................................................................................... 52
3.2 Dielectric Loaded Antenna ............................................................................ 53
3.3 Bilateral 3D Printed Vivaldi Antenna ............................................................. 55
3.4 Bilateral 3D Printed Vivaldi Antenna with 3D dielectric component............... 63
3.5 Fabrication of Bilateral 3D Printed Vivaldi with and without Dielectric Loading
…………………………………………………………………………………….. 78
3.6 Measurement of Antenna Reflection Coefficient ........................................... 83
3.7 Measurement of Antenna Radiation Characteristics ..................................... 86
3.8 Different of Dielectric Structure for Antenna .................................................. 91
3.9 Dielectric Loaded Monopole Antennas ......................................................... 93
3.10 Simulated Design of Granule Antenna aka Lego Antenna ............................ 98
3.11 Simulation and Measurement of 3D Printed Patch Antenna ....................... 105
3.12 Conclusion .................................................................................................. 109
CHAPTER 4 ................................................................................................................ 111
Conclusions ............................................................................................................. 111
Future work .............................................................................................................. 113
BIBLIOGRAPHY ......................................................................................................... 155

v

LIST OF FIGURES
Figure 1.1

Hammerstone used in prehistoric time where the bottom three was made
by modern archeology while the top three stone was found in Lizard Man
Village, Arizona [1]. .................................................................................... 6

Figure 1.2

Illustration of a material that involve in subtraction process. ...................... 7

Figure 1.3

Simple illustration of 3D object design by using injection molding method 8

Figure 1.4

Schematic sketches of three types of apparatus constructed in the present
work [13]. ................................................................................................. 11

Figure 1.5

Stereolithography apparatus. ................................................................... 12

Figure 1.6

Example of 3D printing technology capabilities in medical field [24]-[26]..16

Figure 1.7

3D printed (a) structure of aortic valve and (b) combination of 3D printed
aortic valve with hydrogels binding [27].. ................................................. 16

Figure 1.8

World’s First 3-D printed car [31]. ............................................................ 17

Figure 1.9

3D printed custom made chocolate [32]................................................... 17

Figure 1.10 3D printed gun component made from ABS plastic [38]. ......................... 18
Figure 1.11 Necklace and shoes are some of the custom fashion elements that can be
made using 3D printed technology [39].................................................... 18
Figure 1.12 Microfabrication process flow. .................................................................. 24
Figure 1.13 3D printed signal conditioning circuit and Electronic circuit mechanically
designed into substrate [61] ..................................................................... 25
Figure 1.14 3D printed horn and spherical wire antenna [67]-[68]. ............................. 25
Figure 2.1

Design Parameters of the Simple Notch Vivaldi. ..................................... 35
vi

Figure 2.2

Simulated S11 and VSWR for Simple Notch Vivaldi. ............................... 36

Figure 2.3

Simulated Gains versus Frequency of Simple Notch Vivaldi. .................. 37

Figure 2.4

Design Parameters of the Corrugated Vivaldi. ......................................... 38

Figure 2.5

Simulated S11 and VSWR for Corrugated Vivaldi. .................................. 39

Figure 2.6

Simulated Gains versus Frequency of Corrugated Vivaldi. ...................... 40

Figure 2.7

Comparison of reflection coefficient for the Simple Notch Vivaldi and
Corrugated Vivaldi. .................................................................................. 41

Figure 2.8

Comparison of gain versus frequency for the Simple Notch Vivaldi and
Corrugated Vivaldi ................................................................................... 42

Figure 2.9

Comparison of simulated maximum gain with antenna made entirely with
copper and with dielectric covered with a thin copper layer. .................... 43

Figure 2.10 3D printed Corrugated Vivaldi before (half piece) and after copper
sputtering (completely assembled structure). .......................................... 46
Figure 2.11 Comparison of reflection coefficient between simulated and measured
simple notch Vivaldi antenna ................................................................... 47
Figure 2.12 Comparison of reflection coefficient between simulated and measured
results for Corrugated Vivaldi antenna ..................................................... 48
Figure 2.13 Comparison of measured results of simple notch and corrugated Vivaldi 49
Figure 2.14 Measured radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz. .............. 50
Figure 3.1

Design parameters of the bilateral antenna. ............................................ 58
vii

Figure 3.2

Gain versus frequency based on the variation of length of the bilateral
Vivaldi. ..................................................................................................... 59

Figure 3.3

Simulated reflection coefficients of Simple Notch Vivaldi and Bilateral
Vivaldi Antenna ........................................................................................ 60

Figure 3.4

Comparison of simulated gain versus frequency of Simple Notch Vivaldi
and Bilateral Vivaldi. ................................................................................ 61

Figure 3.5

Simulated radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz ............... 62

Figure 3.6

Designs parameters of (a) Rod (b) Rectangular (c) Corrugated (d) Circular
shapes dielectric inserted into the aperture of the Bilateral Vivaldi. ......... 67

Figure 3.7

Simulated reflection coefficients of various shapes of dielectric inserted in
the aperture of the Bilateral Vivaldi. ......................................................... 68

Figure 3.8

The E-field of bilateral Vivaldi with a rod shape dielectric ........................ 69

Figure 3.9

The E-field of bilateral Vivaldi with a rectangular shape dielectric ........... 70

Figure 3.10 The E-field of bilateral Vivaldi with a corrugated shape dielectric ............ 71
Figure 3.11 The E-field of bilateral Vivaldi with a circular shape dielectric .................. 72
Figure 3.12 Simulated results of gain versus frequency of Corrugated and Circular
Dielectric shape. ...................................................................................... 73
Figure 3.13 Simulated reflection coefficients of bilateral without dielectric and Bilateral
with dielectric Vivaldi. ............................................................................... 74
Figure 3.14 Simulated results of gain versus frequency of Bilateral without and with
dielectric Vivaldi. ...................................................................................... 75
Figure 3.15 Simulated radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz ............... 76
viii

Figure 3.16 Simulated results of gain versus frequency of Simple Notch and Bilateral
with Dielectric Vivaldi. .............................................................................. 77
Figure 3.17 As fabricated bilateral Vivaldi prior to deposition of Cu layer and assembly.
................................................................................................................. 80
Figure 3.18 Fabricated Bilateral Vivaldi after blanket copper coating on both sides of
the structures…………………………………………………………………..81

Figure 3.19 Fabricated Bilateral Vivaldi coated with copper plus the circular dielectric
with the coaxial cable place in the antenna.............................................. 82
Figure 3.20 Simulated and Measured of 3D printed Bilateral Vivaldi without dielectric
component. .............................................................................................. 84
Figure 3.21 Simulated and Measured of 3D printed Bilateral Vivaldi with dielectric
component. .............................................................................................. 85
Figure 3.22 Simulated and Measured of 3D printed Bilateral Vivaldi without dielectric
component. .............................................................................................. 88
Figure 3.23 Simulated and Measured gain of 3D printed Bilateral Vivaldi with dielectric
component. Simulations are carried out for dielectric component with and
without loss tangent. ................................................................................ 89
Figure 3.24 Measured radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz ............... 90
Figure 3.25 Fabricated 3D cylindrical dielectric components ...................................... 95
Figure 3.26 Dielectric structure used in loading the antenna element......................... 95
Figure 3.27 Measured reflection coefficients of a monopole loaded with different
diameter dielectric rings (5mm, 9mm and 13mm) dielectric pieces.. ....... 96

ix

Figure 3.28 Measured reflection coefficients of a monopole loaded with bi-layer
dielectric rings for different diameters (5mm, 9mm and 13mm) dielectric
pieces.. .................................................................................................... 97
Figure 3.29 Reference structure for a 3D folded antenna ......................................... 100
Figure 3.30 First Configuration of 3D folded antenna with additional of 3D printed
blocks..................................................................................................... 101
Figure 3.31 Second Configuration of 3D folded antenna with additional of 3D printed
blocks..................................................................................................... 102
Figure 3.32 Third Configuration of 3D folded antenna with additional of 3D printed
blocks..................................................................................................... 103
Figure 3.33 Simulated reflection coefficients of 3D folded antennas ........................ 104
Figure 3.34 3D patch antenna design (a) 3D view (b) Top view and (c) Side view ... 106
Figure 3.35 Fabricated 3D patch antenna design (a) 3D view (b) Top view and (c) Side
view........................................................................................................ 107
Figure 3.36 Simulated and Measured of 3D printed patch antenna for reflection
coefficient............................................................................................... 108

x

CHAPTER 1
Literature Review
1.1

Introduction and Background

Components with three-dimensional (3D) structure have gained significant interest in
recent years. As the technology progresses rapidly, the electronic industry has become
one of the main users of 3D component as an integral part of the system or sub-system.
The competitiveness of the market to manufacture quality products, catering to
individual costumers and at the same time provide dense functionality are the main
driving forces leading to interest in this field. This allows the development of
multifunctional, compact, miniaturize and light weight devices to be created in order to
satisfy the need of the market either for high end technology applications or low cost
electronics (e.g, single use RFID technologies). This need and challenge has led to a
significant advancement in 3D manufacturing technology for a range of applications. In
particular, the advances have been made to design and fabricate 3D physical
1

prototypes rapidly. To date, major emphasis has been to design structures to provide
mechanical properties. However, this technology has advanced significantly that 3D
fabricated structures can now be adapted to carry out electrical functionality. In
particular, 3D technology holds significant potential in the design of antenna structures
that provide improved performance as complex 3D structures unimaginable can be
easily fabricated. This chapter first gives a brief background on 3D printing and its
potential application in the design of electronic circuit components. In particular, the
benefits and challenges associated with the adoption of 3D printing of antenna
structures.

2

1.2

Introduction to 3D Printing
Technology

Before 3D printing technology existed, thousands of years back humans created 3D
objects by all sorts of methods. The original purpose of 3D object was to design sharp
objects or pattern material that will be used for hunting and daily usage for survival.
Material that was largely used to create 3D object is called hammerstone which is
shown in Figure 1.1 [1]. The hammerstone is a hammer like tool that was used to chip
away stone and bone to create different 3D objects or tools and the method is called
flint knapping [2]-[3]. Such material that was to produce arrowhead, axes and prehistoric
knife for hunting while plates and cup for dinnerware. This technique evolved over time
and is familiarly called sculpturing. The development of sculpturing evolved to a more
sophisticated form which began to use a combination of different materials and tools.
The Greeks used chisel to sculpture 3D object as special human body structure out of
ceramic and stone while clay was used to design pottery which is usually molded by
hand. This technique requires expertise to design complex structure and shape. As
centuries passed, the approaches and tools to sculpture 3D objects have evolved to the
atomic level. Now humans have a vast range of tools (albeit some are expensive) and
materials that can be utilized to grow structures whereby the location of every atom
inside a structure can be precisely controlled. To achieve this level of precision on a
routine basis still requires significant advancement in technology. One area that has
advanced significantly and is easily assemble is the sculpturing of objects using robotics
coupled with thin layer film deposition, etching or molding in a precise area location.

3

Furthermore, the base structure onto which this molding takes places does not have to
be planar.
The modern method of creating 3D objects is by using computers to control
sawing, turning, drilling and milling machines [4]-[8]. The subtraction process uses
blocks of material and carves away until the desired shape is achieved. Figure 1.2
shows an illustration of a subtraction process. The conventional methods have many
disadvantages based on the expensive tools required and the loss of material wasted in
the process. Beside subtraction methods, there are other conventional methods such as
formative methods as a process for creating 3D objects. One of the processes that uses
a formative method is an injection molding technique [9]-[12]. 3D objects are created by
injecting a liquid material in into a mold under pressure where it fills all the voids and
spaces. The material then hardens inside the mold which is then removed from the
mold, see illustration in Figure 1.3. For low batch fabrication, this process is very time
consuming and expensive in term of the equipment and material used. The major cost
factor is the design and fabrication of the mold structure.
Over the past few decades, people have become more aware of the capability of
3D printing technologies often referred to as additive manufacturing. Some have
dubbed 3D printing technology to be the next big innovation of this generation. 3D
printing methods are a technique of producing a physical model of an object from a
digital model. The ability to do so is by creating layer by layer material in the additive
process. Layering of many thin films builds up which in the end becomes a 3D object.
This technology is similar to having a paper printer on every office desk. This ability
allows for rapid prototyping of an object with limitless design, and the control to design

4

and fabricate is given to individual users. This technique eliminates many factors such
as using excessive and expensive machinery or the use of adhesive material that is
used to combine the parts and even reduce the waste material.

5

Figure 1.1

Hammerstone used in prehistoric time where the bottom three was made
by modern archeology while the top three stone was found in Lizard Man
Village, Arizona [1].

6

SUBSTRACTION
PROCESS

Figure 1.2

Illustration of a material that involve in subtraction process.

7

Molding structure
is design.

Injection filling into
the molding

Injection pressure
phase and cooling

3D objects

Figure 1.3

Simple illustration of 3D object design by using injection molding method.

8

1.3

History of 3D Printing Technology

3D printing technology was first introduced in the 1980’s for rapid prototyping. The main
goal of the technology was to build a prototype of an object in order to test the concept
of the product that will be manufactured after preliminary tests. The first report of the
concept was introduced by Hideo Kodama of Nagoya Municipal Industrial Research
Institutes. He was using photopolymer to create rapid prototypes and published a paper
under the title, “Automatic method for fabricating a three-dimensional plastic model with
photo-hardening polymer,” in 1981 and the schematic of the process is shown in Figure
1.4 [13]-[14].

The method uses a layer by layer technique and exposes the

photopolymer area with UV light source to cure the polymer resulting in a 3D object.
Further elaborating on the method, Charles W. Hull produced a method called laser
lithography or better known as Stereolithography (SLA) in 1984 and the schematic of
the process is shown in Figure 1.5 [15]-[16]. This technique uses a computer to deposit
a polymer and instantaneously exposes the polymer to a source of UV light. The
materials form an adhesive layer on each other allowing them to stick and form the
desirable object or design. He was the first to patent this 3D printing process, and was
given the credit as the first inventor of 3D printing devices.

The technologies

progressed rapidly, leading to many different methods for producing 3D printed objects.
These methods include digital light processing (DLP), Laser Sintering or Laser Melting,
Fused Deposition Model (FDM), Freeform Fabrication (FFF), Binder Jetting, Material
Jetting, Selective Deposition Lamination (SDL) and Electron Beam Melting (EBM) 3D
printing [16]-[23].

9

With all the capability presented by 3D printing, manufacturing industries have
taken 3D printing to a new level. The first objective of 3D printing was merely creating a
prototype of an object in order to test the functionality. However, 3D printing is now
creating objects that can be used as end products. Any idea imaginable in a solid shape
object that can be drawn or designed in a computer can be transformed in to a physical
structure by merely using 3D printing machines. This technology has opened up a vast
spectrum of applications in all sorts of fields. Many fields have taken advantage of the
capability of 3D printing in order to improve and innovate in their respective fields.

10

Figure 1.4

Schematic sketches of three types of apparatus constructed in the present
work [13].

11

Figure 1.5

Stereolithography apparatus.

12

1.4

Applications of 3D Printing
Technology

The medical field is one of the fields that are taking advantage of the potential of 3D
printing. Custom made devices to aid patients are being made using 3D printing such as
prosthetic limbs and hearing aids. As 3D printing has evolved, the uses in the medical
field have also evolved. 3D printings technology are now used for replicating bones,
parts of the body such as ears, skull and even reproducing tissue and organ can be
seen in Figure 1.6 [24]-[26]. The main challenge in medical field is to create body parts
as close as possible to the natural structure. In one example, a research paper shows
the construction of recreating artificial aortic valve using 3D printing technology. As we
know recreating human parts is very complex [27]. The way the paper shows is that the
used 3D printing technology using material made out of polymer based call polyethylene glycol-diacrylate with hydrogels supplemented with alginate. They successfully
fabricated anatomical scaffolds which resembles the mechanical function of aortic valve.
This paper showed that 3D printing can be done by using different polymer which is
able to interact safely with the cells and produce a functional aortic valve can be seen in
Figure 1.7 [27].
Other than the medical fields, the automotive sector is one of the earliest users
of 3D printing. Automotive industry requires manufacturing individual parts of the car
and then assembling them together in an assembly line. Sometimes improvement must
be made in order to upgrade the car to improve their quality. 3D printing was employed
to make custom parts, to make prototypes and make replacement parts [28]-[30]. One
of the new innovations of 3D printing in automotive is creating the whole car using 3D
13

printing. The first 3D printed car was made by Local Motors, see Figure 1.8. The
constructed 3D printed car is considered as the new manufacturing method and will be
the way of manufacturing cars and parts in the future [31]. Significant advancements in
3D printing technology are still needed to be able to print metal and plastic parts
simultaneously.
As stated earlier, plastic was the main source of 3D printing material. The
technology is now expanding into printing different materials (e.g., metals, ceramics,
etc.). One of the most interesting materials used in 3D printing is edible food substance.
The conventional way of creating 3D printed chocolates was by using a cast technique,
where the chocolates in a liquid form were poured into the cast and left to be solidified.
But with 3D printing technology, the creation of 3D printed chocolates can be simplified
and the vast design can be made. This has open up new applications of 3D printing
technology in the sector by providing easy customizable 3D printing chocolates and the
example can be seen in Figure 1.9 which showcase a chocolate with a face like shape
was develop by a group of researcher from University of Exeter [32]. The concept was
the same in creating plastic 3D printed object where layer by layer of chocolate was
stack onto of each other to create the 3D objects. Based on this development, further
research was done to create 3D printing edible food. Different type of food that was
able to be done using 3D printing is cookies, mash potato waffles, candy and sugar
frosting [33]-[35].
One of the more shocking uses of this technology is the creation of weaponry.
The ability of creating weapons using 3D printing was demonstrated by a company
called Solid Concept. They were capable of manufacturing a functional rifle using a 3D

14

printer [36]-[38]. Fashion designers have been well known for the expertise in designing
unique and complex design structure. High skill set is required to shape and mold
accessories in the desirable shape. The modern designer uses 3D printing technology
to promote futuristic style that might be the new way of designing clothes. This allows
the more creativity in designing because complex shape and design can be easily
manufactured.

Some of the design is shown in Figure 1.11 to shows 3D printed

capability to create clothing and accessories [39].

15

Figure 1.6

(a)
(a)

Figure 1.7

Example of 3D printing technology capabilities in medical field [24]-[26].

(b)

3D printed (a) structure of aortic valve and (b) combination of 3D printed
aortic valve with hydrogels binding [27].

16

Figure 1.8

World’s First 3-D printed car [31].

Figure 1.9

3D printed custom made chocolate [32].

17

Figure 1.10 3D printed gun component made from ABS plastic [38].

Figure 1.11 Necklace and shoes are some of the custom fashion elements that can be
made using 3D printed technology [39].

18

1.5

Electronic Applications

The main focus of this thesis is to show the applicability of 3D printing for the fabrication
of electronic components; in particular, antenna elements. Over the last few decades,
there has been growing interest in the fabrication of 3D components that allows new
functionality and high density integration. Hand-held electronic devices nowadays have
become ultra-compact, miniaturize, light-weight and having multi-functionality in the
systems. In a typical electronic system, the components are fabricated separately from
the housing of the system. However, with recent advances in 3D printing these two can
be readily be integrated together leading to the design of high density and complex
systems.
The research on the development of compact and miniaturized electronic devices
has long been developed. More than 30 years of research have been done to fabricate
circuitry to a smaller level scale. In order to obtain such small scale devices a technique
called microfabrication technology is commonly used [40]. Microfabrication technology
consists of several processes in order to fabricate devices. The process uses
lithography process, deposition of materials, pattering of the desire pattern and the
etching process which is shown in Figure 1.12. Each process has their own techniques
that changes depend of the desire application for the devices. With the advantage of
making smaller devices using microfabrciation, applications in integrated circuitry,
microfluidic, microsensors and microelemechanical systems (MEMs) was developed
[41]-[44]. This allows compact and miniaturizing of devices to be done. However, there
is a lot of limitation in using this technique such as the precision is based on the
technical ability of the person fabricating and the technology used in the fabrication
19

process as well as the time needed for fabrication takes a longer time [45]. In this case
in does not allows the ability to fabricate the whole devices as the enclosure of the
circuitry is done independently.
From weight point of view, different types of materials have been synthesized to
give components a more feather like weight. One of the most popular materials used in
devices nowadays is graphene. Graphene is a thin carbon layer that has many benefits
properties such as the strength and durability of the material as well as the light weight
aspect [46]-[47]. Graphene has been use in devices for the capability of integrating
circuitry in order to enhance the performance and the efficiency of device as well as
being used as an enclosure or shielding from electromagnetic waves [48]-[51] .
However, the disadvantage of graphene is that it is very expensive due to the limitation
in production of high quality material [52]. Furthermore, it does not give the ability to
integrate multiple systems in a graphene form devices.
On the other hand, little have been done in designing multifunctional electronic
devices that have the ability to multitask by incorporating all the functions into one
package. The conventional way of designing multifunctional electronic devices is by
building the component separately and assembling it to form the whole device which will
take longer to produce and consumes more space.
The main goal of multifunctional electronic devices is to give a more affordable
cost, trim down the manufacturing time, and simpler way to manufacture, compactness,
combining the functionality into one, light weight and also maintaining the capability to
operate well. There are several ways that has been developed to do so. One of the new
technologies is 3D integration. 3D integration is a system where layer by layer of active

20

devices are stack and interconnect with one another [53]. The main advantage of this
technique is the ability to minimize the work space area by stacking the components by
using vias in the z direction (vertical). Significant research is being carried out and
tremendous progress has been made in 3D integration such as 3D packaging
technology, monolithic 3D integration circuits and wafer to wafer 3D integration circuits
[54]-[56]. However, several disadvantages arise due to the risk of having defect during
fabrication, the accuracy depends on the sophistication of the machinery especially
alignment, the complexity in designing and also the overall cost of manufacturing [57][58].
As an alternative, electrical engineering community has adapted the concept of
3D printing because of its simplicity, rapid prototyping, and the ability of print many
types of materials at low temperatures on a host of substrates. These manufacturing
methods have led to creating new devices and applications.

Initially, 3D printing

machines were used to merely generate enclosures and packaging elements for
electronic devices. The conventional way of packaging electronic devices requires the
use of molding material or using metal sheets or plastic to provide an enclosure and
protection. However, the expensive molds have to be redesigned every time there is a
change in package design or custom designs are necessary. Recently, 3D printing has
drastically changed this concept. Companies now have the ability to manufacture
packages in all sorts of shape and sizes depending on their needs as well as reducing
the time and manufacturing cost.
Other usage of 3D printing is by integrating circuit designs on to packaging such
as a substrate or any form of surface that can be printed on [59]-[61]. The conventional

21

way of fabricating electromagnetic structure on a substrates requires careful procedure
which include the photoresist application, exposure and developing of photoresist to UV
light and lastly the etching of photoresist [62]. This leads to the rise in cost and time
spent in fabricating and not to mention the fabrication must be done in a controlled
environment due to the sensitivity of the photoresist. Along with these previous
requirements there is a need to use potentially hazardous chemicals. An alternative way
is by using 3D printing techniques to print the structure directly on to the circuit board or
other suitable substrates can be illustrated in Figure 1.13. This application is useful for
building circuitry on a compact space such as in aerospace, communication such as cell
phone and electronics sensors [63]-[66].
A new implementation of 3D printing within electrical engineering is its use to
develop new methods of fabricating antennas. The conventional way of fabricating a 3D
antenna depends of the configuration of the antenna. For example a horn antenna is
made by cutting out template of coppers or other conductive material and constructing
them it in a specific dimension needed for the specific application. The template sheet is
then joined together by soldering the pieces. The front end of the antenna is then
combined together with the waveguide to form a horn antenna. Another way of
fabrication involves subtracting the 3D antenna from a bulk of metal to the desired
shape of the antenna. Both of the conventional techniques require sophisticated
machinery which increases the cost of production and material waste. As an example,
horn antennas have been fabricated using 3D printing technology. Theses antennas
show the performance and the functionality to be as close as the standard horn antenna
that is produced using conventional labor intensive machining processes [67]. Other

22

type of antenna that used 3D printing method for fabricating is electrically small
spherical wire antenna. This 3D printed antenna shows the capability of having similar
characteristic with a well-known folded spherical helix antenna [68]. Both antennas are
shown in Figure 1.14. Although these early results have shown the benefit of using 3D
printing in place of conventional fabrication approaches, there is significant potential in
using 3D printing to design novel antenna structures. New structures that can improve
antenna performance and also new designs that would be difficult to achieve using
conventional fabrication approaches are possible through 3D printing. The next section
outlines the objective and motivation of this thesis work.

23

Figure 1.12 Microfabrication process flow.

24

Figure 1.13 3D printed signal conditioning circuit and Electronic circuit mechanically
designed into substrate [61].

Figure 1.14 3D printed horns and spherical wire antenna [67]-[68].

25

1.6

Motivation and Objectives

In recent years, the interest towards wireless communication has become a topic of
significant interest due to growing wireless applications. Antennas are an essential part
of these wireless systems. Antenna designs are complex and they need to meet
requirement for functionality or application, bandwidth, gain, efficiency, coupled with
need to meet high reliability and low cost manufacturing. Various techniques have been
applied in the fabrication of antennas. However, very little work has been reported in
open literature on the design and fabrication of antennas utilizing 3D printing technology.
The main focus of this thesis is to develop an alternative way to fabricated microwave
antennas using low cost processes. In particular, the goal of this thesis is to design and
demonstrate 3D printed wide band microwave antennas.
A Vivaldi antenna design was chosen in order to prove the concept that wide
band high frequency operating antenna can be fabricated using 3D printing technology.
Furthermore, Vivaldi antenna has high gain, symmetrical radiation pattern as well as
excellent directivity due to the end-fire nature of the antenna. Also, Vivaldi can be
designed to have a 3D physical structure which can be used to improve its performance.
One of the major challenges with 3D printing is that a separate feed is required to excite
the antenna that cannot be directly printed. Thus, a novel feed technique was devised
for the antenna designs of this work. In this work, first a simple Vivaldi antenna was
designed and fabricated and then improved based on the flexibility provided by 3D
fabrication. This includes the physical structure as well as the ability to combine
localized metal and dielectric regions within an antenna to achieve novel designs.

26

Apart from Vivaldi antennas, other antennas are also studied in this thesis work.
This includes a patch antenna and a reconfigurable monopole antenna. The 3D printed
dielectric is studied as a substrate for the patch antenna. 3D fabricated dielectric loading
elements are also studied to change the resonant frequency of the monopole antenna.
Additionally, a reconfigurable Lego like antenna will be presented in this thesis. This
antenna demonstrates the concept of an interchangeable antenna element through the
use of a combination of dielectric and metallic granules (Lego like blocks). This thesis
presents both simulation results and measured results and these results are discussed
in detail.

27

1.7

Thesis Layout

As a proof of concept, Chapter 2 will show the capability of building Vivaldi antenna
using 3D printing technology. The performance of the antenna is based on the antenna
parameters such as frequency operation (bandwidth), voltage standing wave ratio
(VSWR), radiation pattern, beamwidth and gain of the antenna. This chapter shows that
the performance of the Vivaldi antenna can be improved compared to conventional
designs
In chapter 3, the concept of integrating a dielectric focusing element in Vivaldi
antennas is introduced that can readily be fabricated using 3D printing. It shows that 3D
printing readily allows integration of complex 3D dielectric and metallic parts which
provides additional flexibility in antenna design. This chapter shows new Vivaldi antenna
designs with enhanced performance. Also, novel antenna designs are presented that
shows that tunable antennas can be designed using 3D printing.
Lastly, chapter 4 concludes the work of this thesis and also gives a brief outline
of potential future work that can be carried out in the area of antenna designs using 3D
printing technology.

28

CHAPTER 2
3D Printed Vivaldi Antenna
2.1

Introduction

Antennas have become an essential component in modern day electronics for a variety
of applications including wireless communications, wireless sensors, RFIDs, military
radar, and biomedical imaging [69]-[70]. A number of antenna parameters are important
for these applications, such as antenna size, bandwidth, gain, and cost. Antenna
bandwidth is of particular interest in a variety of applications. There are several types of
well-known wideband antennas, such as horn, biconical, helical, and sleeve antennas
[71]. There is also a significant effort in the research community to develop novel
wideband antennas. In particular, much work has been done in the development of
ultra-wideband antennas (UWB). UWB antennas are defined as any antenna with a
bandwidth greater than at least 30 % of its center frequency [72]. However, due to
29

recent FCC regulations allowing the transmission of low power signals from 3.1 to 10.6
GHz, there has been a particular interest in developing antennas with enough
bandwidth to cover the entire range [73].
While antenna bandwidth is of particular interest for many communication
systems, the gain of the antenna is equally important. Designing an antenna which
combines a wide operating bandwidth with high-gain that is also compact in size, lowcost, and simple to fabricate is a challenge. One such antenna that combines many of
these parameters is the Vivaldi antenna.
The Vivaldi antenna was first introduced by B.J. Gibson in [74] as an alternative
wideband antenna. A traditional Vivaldi antenna contains an exponential tapered slot,
and acts like end-fire travelling wave antenna. Based on its end-fire characteristic, the
Vivaldi antenna has a high-gain, consistent radiation pattern over a large frequency
range. Theoretically, a Vivaldi antenna can have infinite bandwidth; however, in [75] a
traditional type Vivaldi antenna is shown to operate over a frequency bandwidth of
approximately 4.9 GHz with center frequency of 2.45 GHz. When designing and
fabricating a Vivaldi antenna, several methods have been suggested, the most common
of which is a planar structure fabricated on a dielectric substrate [76]-[78]. While these
methods produce a high-gain and wideband Vivaldi antenna, they can be difficult to
feed and difficult to fabricate. Recently, 3D printed manufacturing processes have
become very popular in the research community due to their ability to build precise
geometric models of complex designs [79]-[81]. 3D printing also shows much promise in
antenna design, as the fabrication process will be much faster, simpler, and very low
cost. Additionally, the rigidity and flexibility of the structure allow a reliable antenna to be
30

built. However, most 3D printed antennas in the current literature are printed directly
from metal, as opposed to using a dielectric host structure [82]-[83]. Here, two highgains, wideband Vivaldi antennas are made from a metalized-polymer 3D printed
material. The first Vivaldi antenna consists of a simple slot-line design with a radiating
cavity. The second antenna introduces a corrugated slot with a partially covered cavity,
which is shown to increase the gain and bandwidth of the antenna. The antennas are
designed using the commercial FEM solver HFSS and assumed made entirely of
copper. Each design is 3D printed with a VeroWhite (ABS, Acrylonitrile butadiene
styrene) plastic-polymer, and metalized with a thin layer of copper (1m). The antennas
are fed with a simple 50 coaxial cable through a slot that is printed in the design. Finally,
the reflection coefficient and radiation parameters of each of the antennas are
measured, showing a low reflection coefficient and high gain over a wide frequency
band. The simulated and measured results show that these antennas will find
application in low-cost UWB communication systems.

31

2.2

Antenna Design and Simulation

In this section, the design and simulation of the 3D printed Vivaldi antennas is
presented. First, a conventional slot-line Vivaldi is introduced, followed by a modified
corrugated structure. Solid copper is used to model the antennas, as it is assumed that
the thickness of the copper will be negligible in the performance of the antenna. ANSYS
HFSS is used to simulate the reflection coefficient and radiation patterns of the
antennas.
For the initial slotline Vivaldi antenna, certain design parameters are important in
deciding the performances of the antenna. The impedance of the antenna is dictated by
the radius of the cavity which acts as a quarter-wave matching circuit in conjunction with
the slotline. The tapering of the slot also acts as a smooth impedance transition
between the 50 feed and the free space wave impedance. The physical dimension of
the slotline Vivaldi antenna is shown in Figure 2.1. The relevant dimensions of the
antenna are as follows: the width (W) is 37 mm, length (L) is 107 mm and the thickness
(T) is 4.5 mm. The diameter (D) of the cavity is 22.1 mm and the slotline gap (S) is
equal to 1.1mm. Finally, the position distance of the coaxial cable to the cavity (P) is
1.17 mm which is the optimize position. Figure 2.2 shows the reflection coefficient and
also the voltage standing wave ratio (VSWR). In the graph it shows that the S11 has a
large bandwidth from 3.39 to 19.55 GHz. However there was a discontinuity between
4.33 GHz until 4.72 GHz. It may be resulted in an impedance mismatch. The next
Figure 2.3 shows the gain versus frequencies. While the slotline Vivaldi antenna
provides a high-gain and very large bandwidth, the reflection coefficient can sometimes
dip below an acceptable level intermittently throughout its frequency range.
32

One possible solution is to introduce corrugated edges into slotline of the Vivaldi
antennas. The tapered slotline improves the impedance matching at the discontinuous
frequencies, increasing the overall bandwidth. The regions where the discontinuities
earlier in the simple notch Vivaldi have been better impedance match due to the
addition of the corrugated elements. The corrugated edges act as a longer path
resulting in a bigger aperture causing a better S11 at lower frequencies [84]. In addition,
this design introduces a partially covered cavity which decreases the back-lobe of the
radiation pattern increasing the overall gain of the antenna. The geometry of this design
is shown in Figure 2.4, with a spacing gap (G) of 1mm, and corrugation periodicity (M)
of 4mm, and cover spacing (C) of 18mm. The reflection coefficient was simulated to
shows the changes that were due to the corrugated element shown in Figure 2.5. The
maximum gain of both antennas as a function of frequency is shown in Figure 2.6. In
both cases, the maximum gain occurs in the E-plane. As expected, the gain of the
corrugated Vivaldi antenna is increased, especially in the lower frequency regime.
However, both antennas have a very high gain over a large frequency range. The
comparison was made between the simple notch Vivaldi and Corrugated Vivaldi for
reflection coefficient and gain versus frequency are shown in Figure 2.7 and Figure 2.8
respectively.
In order to ensure the approximation of using solid copper to simulate the
antennas is a valid assumption, the unmodified slotline antenna is simulated entirely
made of copper and with a lossy-dielectric covered in a thin layer of copper. The
dielectric used in the case has a εr = 3.0 and a tan δ = .02. The copper thickness for the
dielectric case is modeled as 1.0 µm thick. Figure 2.9 shows the maximum gain of the

33

antenna versus frequency for both cases. As expected, there is very little difference in
the gain for both cases.

34

Figure 2.1

Design Parameters of the Simple Notch Vivaldi.

35

0

9

S11
VSWR

-5

8

-10

7

-15
-20
5
-25
4
-30
3

-35
-40

2

-45

1
0

Figure 2.2

5

10
Frequency, GHz

15

Simulated S11 and VSWR for Simple Notch Vivaldi.

36

20

VSWR

|S11| (dB)

6

14
12
10
8

Gain (dB)

6
4
Simulated
2
0
0
-2

5

10
Frequency (GHz)

15

-4
-6
-8

Figure 2.3

Simulated Gains versus Frequency of Simple Notch Vivaldi.

37

20

Figure 2.4

Design Parameters of the Corrugated Vivaldi.

38

0

9

-5

8

-10

7

|S11| (dB)

6

-20
5

-25
S11

4

-30
VSWR
3

-35
-40

2

-45

1

0

5

10

15

Frequency (dB)

Figure 2.5

Simulated S11 and VSWR for Corrugated Vivaldi.

39

20

VSWR

-15

14
12
10
8

Gain (dB)

6
4
Simulated

2
0
0
-2

5

10

15

Frequency (GHz)

-4
-6
-8

Figure 2.6

Simulated Gains versus Frequency of Corrugated Vivaldi.

40

20

Frequency (GHz)
0
0

5

10

15

20

-5

-10

|S11| (dB)

-15

Simple Notch Vivaldi

-20

Corrugated Vivaldi

-25

-30

-35

-40

Figure 2.7

Comparison of reflection coefficient for the Simple Notch Vivaldi and
Corrugated Vivaldi.

41

14

12

10

8

6

Gain (dB)

4

Simple Notch Vivaldi
Corrugated Vivaldi

2

0
0

2

4

6

-2

8

10

12

14

16

18

Frequency (GHz)

-4

-6

-8

Figure 2.8

Comparison of gain versus frequency for the Simple Notch Vivaldi and
Corrugated Vivaldi.

42

20

14

12

Copper

10

Dieletric

8

Gain (dB)

6

4

2

0
0

-2

2

4

6

8

10

12

14

16

18

20

Frequency (GHz)

-4

-6

-8

Figure 2.9

Comparison of simulated maximum gain with antenna made entirely with
copper and with dielectric covered with a thin copper layer.

43

2.3

Fabrication and Measurement

After each antenna is designed in HFSS, the 3D model is exported and printed using an
Objet Connex350 3D printer. This printer has a 16 µm print resolution, and can be used
with a variety of polymer-based materials. In the case of this letter, a VeroWhite plasticpolymer is used to print the antennas. Each antenna is printed in two pieces so that the
coaxial cable can be easily inserted. Both sides of the antenna are then fixed together,
and the antenna is sputtered with approximately 1µm of copper. Figure 2.10 shows the
corrugated Vivaldi antenna before and after the sputtering of thin Cu layer. The
reflection coefficient of each antenna is measured with an Agilent N5227A PNA network
analyzer. Figure 2.11 and 2.12 shows the reflection coefficient for both the slotline
Vivaldi antenna as well as its corrugated counterpart, respectively. The measured
reflection coefficients show relatively good agreement with the simulated results.
However, there is a slight shift in some of the resonant frequencies of the antennas.
This is most likely caused by the sensitivity of the feeding position of the antenna, as
well some slight deviation in the printed antenna dimensions. The bandwidth of the
antenna is however not disturbed, and as expected the corrugation in the antenna does
in fact increase the bandwidth and eliminate any points in the frequency range that were
above -10dB. The measured VSWR is also shown in Figure 2.13. A VSWR of less than
2 is shown for both antennas for a very wide range of frequencies. As mentioned above,
the VSWR of the initial slotline design does increase above 2 at some intermittent points
within the frequency spectrum. The corrugated antenna however has a VSWR that is
clearly below 2 from approximately 3.5 GHz to 18 GHz, leaving a bandwidth of 14.5
GHz. Additionally, some select radiation patterns for each antenna are measured. The
44

radiation patterns are measured using a 3D SATIMO antenna measurement system.
While each antenna works over a large frequency range, the patterns are measured at
4, 10, and 16 GHz to show the overall behavior at the low, mid, and high frequency
ranges. Figure 2.14 shows the radiation patterns of each Vivaldi antenna in both the E
(x-y) and H (y-z) planes. Based on the measured results it is obvious that the gain
increases with the operational frequency of the antenna as expected. In addition, the
beamwidth is decreased as the frequency is increased, which contributes to the
increased gain. Comparing between the two antenna designs, it is clear that the
corrugated antenna displays an increased gain with respect to the traditional slotline
Vivaldi antenna. This is expected considering the VSWR of the antenna is improved
between both designs, as well as the covered cavity. The radiation pattern shows a
slight deviation of (2 to 4) dB due to several reasons. In the system, the angles which
catch the maximum pattern and gain are difficult to obtain based on the placing of the
antenna. Secondly, the sensitivity of the connector placement for the coaxial feed can
have a large impact of the measured results. The surface roughness of the copper may
also have an impact on the results due to the non-uniformity of the sputtering. The missmatch between the measured and simulated results of the antennas becomes more
apparent in the higher frequency patterns. Overall, the measured patterns match
relatively well with the simulated results, showing the potential of 3D printed antennas
for use in UWB antenna applications.

45

Figure 2.10 3D printed Corrugated Vivaldi before (half piece) and after copper
sputtering (completely assembled structure).

46

0
-5
-10

S11 (dB)

-15
-20

-25
-30
Simulated
-35
Measured
-40
-45
0

2

4

6

8

10
12
14
Frequency (GHz)

16

18

20

Figure 2.11 Comparison of reflection coefficient between simulated and measured
simple notch Vivaldi antenna.

47

0
-5

-10

S11 (dB)

-15
-20
-25
Simulated

-30
-35

Measured

-40
-45
0

2

4

6

8

10

12

14

16

18

20

Frequency (GHz)

Figure 2.12 Comparison of reflection coefficient between simulated and measured
results for Corrugated Vivaldi antenna.

48

6

5

VSWR

Simple Notch
Vivaldi
4

Corrugated
Vivaldi

3

2

1
0

2

4

6

8

10

12

14

16

18

20

Frequency (GHz)

Figure 2.13 Comparison of measured results of simple notch and corrugated Vivaldi.

49

(a)

(b)

(c)

(d)

(e)

(f)

Figure 2.14 Measured radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz.
50

2.4

Conclusion

A new method of producing Vivaldi antennas using metalized 3D printed plasticpolymers is presented. Printing antennas with these materials provides a low-cost, fast,
and highly accurate fabrication solution. In addition, both antennas exhibit a large
maximum gain of 12 dB as well as an extremely large bandwidth of up to 14.5 GHz.
Two types of antennas are fabricated with this method using an ABS plastic covered
with a thin sputtered copper layer. The measured and simulated results are shown to
match well, displaying the potential of 3D printing in a low-cost UWB antenna design.

51

CHAPTER 3
Dielectric Loaded Antenna Designs
3.1

Introduction

One of the key advantages of 3D printing is that complex antenna geometries can be
designed and printed. It is well known that dielectric loading of antenna elements can be
used in focusing of waves. Example includes the use of dielectric lens in horn antennas
for enhanced gain. On similar lines, 3D printed structure can be utilized to enhance
antenna functionality. Here, two antenna designs are examined using 3D printed parts:
i) Dielectric loaded Vivaldi antenna and ii) frequency tuning of monopole antennas. Here,
first the base Vivaldi antenna design of the previous chapter is improved and then
coupled with dielectric medium to further improves its performance.
.

52

3.2

Dielectric Loaded Antenna

The greater than ever need to have communication devices that can be used for a
number of applications has attracted enormous attention to do research in this area.
One of the main components that are required is a proficient design of an antenna.
Antenna designs are known to be of a variety of configuration and geometries and are
in use in many applications that range from high technology in military or even wireless
devices in our daily life. A single antenna such as Vivaldi antenna can be optimized in
various ways in the configuration that can improve and modify the antenna parameters
which enable it to be used in different types of applications. The challenge of changing
the configuration or geometries requires lot of work due to the tedious fabrication
process needed to build an antenna such as the Vivaldi. However, 3D printing
technology provides an easier alternative to change the configuration or physical design
of the antenna. The previous chapter demonstrated the use of 3D printing technology in
the design of functional 3D printed Vivaldi antennas. The results showed that 3D printed
Vivaldi antenna is suited for several applications because of its broadband operational
frequencies, easy to manufacture by using 3D printing, relatively high gain and highly
directive radiation pattern. Building on the previous design, several modifications have
been made towards the 3D printed Vivaldi antenna by changing the configuration which
leads to an improvement in performance of the antenna. Apart from changing the
configuration, improving the design, another noteworthy change was made adding a
piece of dielectric which is placed in the aperture of the antenna. The concept that will

53

be shown in this chapter will highlight the integration between dielectric materials with
Vivaldi antenna that allows the improvement of the antenna parameters.

54

3.3

Bilateral 3D Printed Vivaldi Antenna

In this section, the modification of the dimension of design of the 3D printed Vivaldi
antenna is shown. The same geometries were used based on the previous 3D printed
Vivaldi antenna (Simple Notch Vivaldi) but with several modifications that has been
made to improve its performance. The first modification was made by adding bilateral
pieces that was put in place at the end of the antenna as shown in Figure 3.1. The
purpose of the design was done to improve the lower frequency region which leads to
an increase in the overall bandwidth. Design of the antenna was carried out using
ANSYS HFSS. In the simulations it was assumed that the antenna is built out of solid
copper block. In the previous chapter it was shown that by using solid copper give the
same result as using a lossy-dielectric material covered with a thin layer of copper.
The first assessment was made by changing the dimension of the bilateral pieces
that was place on the simple notch Vivaldi antenna. The simulation was made to
determine the effect of the length of the bilateral pieces towards the performance of the
Vivaldi antenna. The gain versus frequency was evaluated in Figure 3.2. The variation
of the length shows that there is a significant change that occurs by changing the
dimension. The best length was determined to be 24.75 mm. This dimension will be
used for the bilateral pieces that will be place on the simple notch Vivaldi.
The simulated result of the S-parameters (S11) in Figure 3.3 shows the
comparison made between the 3D printed simple notch antenna with 3D printed
bilateral Vivaldi antenna. The shift in the bandwidth can be seen clearly seen from the
plots. The bandwidth of the simple notch Vivaldi antenna starts to be under -10dB at
approximately 4.75GHz while the modified version which is the bilateral Vivaldi antenna
55

start at roughly 1.5GHz. Also, at higher frequencies the bilateral Vivaldi antenna shows
better performance with S11 less than -10 dB above 20GHz as compared to the simple
notch Vivaldi which stops at approximately19.5GHz. In the structure, the narrower
region is used for impedance matching at higher frequencies while the wider section
improves the impedance matching at lower frequencies. The S 11 shows the argument
for this statement.
The simulated gain versus frequency for both antennas was determined using
HFSS simulations and is shown in Figure 3.4.

The frequency that was simulated

ranges from 1 to 20 GHz. From the graph it can be seen that there is a significant
variation in performance between both the antennas. The bilateral Vivaldi antenna has
higher gain than the simple notch antenna over a certain frequency range. At lower than
12.5 GHz, the bilateral antenna has a better gain by as much as 4 dB. This shows that
the bilateral section on the Vivaldi helps to improve impedance matching at lower
frequencies. Due to the good impedance matching at lower than 12.5 GHz, the gain of
this antenna improves significantly. However, at higher than 12.5 GHz, the simple notch
Vivaldi performance much better that the bilateral Vivaldi. This can be related back to
the Figure S11 which indicates that the S11 at a certain frequency for the bilateral is
poorly matched compared to the impedance matching of the simple notch Vivaldi. The
gain of the bilateral Vivaldi suffers from the mismatch leading to the gain to reduce. This
indicates that the radiation mechanism of the Vivaldi is related to the S-parameters and
also shows that the radiation radiates based on the gap position of the Vivaldi. At lower
frequencies, the mechanism that helps the radiation is the wider gap of the antenna
while the narrower gap helps the radiation at higher frequency.

56

As noted the Vivaldi antennas have a wide bandwidth, in this case select
frequencies are simulated to indicate the radiation pattern for both antennas. 5, 10 and
15 GHz are used to represent the low, middle and high operating frequency for the
antennas. The radiation pattern is shown is Figure 3.5. Based on the observation of
radiation patterns, antennas show end-fire directivity of both antennas. The beamwidth
for bilateral Vivaldi displays a narrower beamwidth compare to simple notch Vivaldi for 5
and 10 GHz. This indicates that the gain is due to the beamwidth of the radiation energy
focusing allowing the gain to be higher. However, at 15 GHz the radiation pattern
changes for the bilateral Vivaldi with the presence of two side lobes beside the main
beam. The splitting of the main beam is the cause in the reduction of the gain. The
energy is lost to the side lobes. The side lobes may be due to the radiation coming out
of the bilateral pieces. Nevertheless, in this case the beam of the simple notch Vivaldi
still maintains the main beam and allowing the gain to increase.

57

Figure 3.1

Design parameters of the bilateral antenna.

58

12

10

8

Gain (dB)

6

4

Vary

2

0
0

2

4

6

8

10

12

-2

-4
Figure 3.2

Frequency (GHz)
Gain versus frequency based on the variation of length of the bilateral
Vivaldi.

59

Frequency (GHz)

0
0

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20

-5

|S11| (dB)

-10

-15

-20

Bilateral Vivaldi Antenna

-25

Simple Notch Vivaldi

-30

-35

Figure 3.3

Simulated reflection coefficients of Simple Notch Vivaldi and Bilateral
Vivaldi Antenna.

60

14
12
10
8

Gain (dB)

6
4

Simple Notch Vivaldi

2

Bilateral Vivaldi

0
0

2

4

6

-2

8

10

12

14

16

18

20

Frequency (GHz)

-4
-6
-8

Figure 3.4

Comparison of simulated gain versus frequency of Simple Notch Vivaldi
and Bilateral Vivaldi.

61

(a)

(b)

(c)

(d)

(e)

Figure 3.5

(f)

Simulated radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz
62

3.4

Bilateral 3D Printed Vivaldi Antenna
with 3D dielectric component

In the previous section it was shown that the bilateral section improves the performance
in the Vivaldi antenna over a select frequency region. However, the gain decreases at
higher frequencies due to mismatch of the antenna to the coax feed. In order to improve
the overall performance, a dielectric piece is placed in the aperture of the bilateral
Vivaldi antenna. The dielectric piece acts as a focusing material to guide the radiation
energy in the material so that the radiation is enhanced in the end fire direction. Also,
this allows the radiation beamwidth to be much narrower due to focusing by the
dielectric region. In this section, several dielectric shape is designed in determining
whether the configuration of plays a role in the performance of the antenna. The
dielectric is made out of the same material uses to fabricate the antenna which is acrylic
based polymer called Acrylonitrile butadiene styrene (ABS). The configuration that was
designs for the dielectric is as following: rod, rectangular, corrugated and circular shape
dielectric that can be seen in Figure 3.6.

In the simulation the permittivity of the

dielectric was 3.0.
Several simulation results were analyzed to further verify the improvement made
by the dielectric. The first simulation result shows the S-parameters (S11) of each of the
bilateral Vivaldi inserted with dielectric is shown in Figure 3.7. The S11 for the
rectangular, circular and corrugated antenna has a similar starting frequency at 2.25
GHz while the rod has slightly higher starting point. The rectangular dielectric suffers
from mismatching at the range of 8 to 10 GHz which causing a discontinuity for the
63

bandwidth. The circular and corrugated dielectric shows a similar pattern with slight
deviation which gives the best bandwidth for the bilateral Vivaldi.
Correspondingly the pattern of E-field was simulated to observe the wave
propagating in the dielectric pieces. Each antenna E-field was presented in Figure 3.83.11. Different shapes of the dielectric show an interesting wave pattern. The rod
dielectric displays that the wave does not propagate until the end of the rod. It might be
because of the energy of the propagation is insufficient to force the wave to the end.
The rectangular E-field shows that the wave propagates until the end. Conversely, the
wave shows that the wave is disperse and not focus at the end. Both corrugated and
circular dielectric shows that the wave is converging when it reached the end. The may
lead to a higher gain due to the focusing element of the dielectric structure.
By using the circular and corrugated dielectric will be further evaluated in
determining the performance of the dielectric by having the simulation result for the gain
versus frequency that is represented in Figure 3.12. The gain of both antenna shows
almost similar result in the gain. Nevertheless at a certain frequency each of the
antennas shows higher again than the other one. The overall gain over the range of
frequency shows that circular dielectric has an extra edge over the corrugated dielectric.
Based on the performance of the dielectric pieces that was inserted in the
aperture of the bilateral Vivaldi, the comparison will be made to evaluate the
performance compare to the bilateral Vivaldi without the dielectric. The assessment will
be made by comparing the S-parameters, the gain, radiation pattern and also the
beamwidth of the antenna.

64

The first comparison was made for the S-parameters of both antennas which the
bilateral Vivaldi with dielectric and with non-dielectric (air) is shown in Figure 3.13. In the
results shows that the dielectric causes the frequency to shift to a higher frequency
meaning it is not impedance match as good in the lower frequencies. The bilateral
dielectric Vivaldi antenna also suffers from the poor impedance matching at higher
frequencies. The dielectric integrated with the antenna might not be fully optimized. A
poor S11 does not mean that the overall performance of the antenna is worse. Further
evaluation will be made in showing other antenna parameters.
The second assessment was made by comparing the gain versus frequency for
both antennas which are presented in Fig 3.14. At the lower half of the frequency range
that was measured (under 12.5 GHz) shows that the gains of both antennas are more
or less. However as the frequency increases the gain of the antenna for the bilateral
Vivaldi with dielectric maintain the gain and sometimes increases while the bilateral
Vivaldi without the dielectric decreases in the gain. These shows an indication that the
dielectric insertion on to the bilateral Vivaldi helps improve the gain.
Advance valuation was made to see any sign that shows the gain improvement is
due to the dielectric. The radiation pattern for both antennas is studied and the result is
shown in Figure 3.15.

As expected the radiation pattern of both shows consistent

pattern as expected for a Vivaldi antenna. However, an interesting pattern emerges at
higher frequency. The beamwidth of the bilateral Vivaldi with the dielectric shows a
narrower radiation pattern compare to the bilateral Vivaldi without the dielectric. This
can indicate that the dielectric component in the Vivaldi help focuses the beam and
allows the directivity of the antenna to be more shaper. As the beam narrows the energy
65

of the radiation concentrate to an end fire direction making the gain increase at that
frequency. This proves that dielectric help improving the gain of the antenna.
For convenience a comparison between the simple notch Vivaldi antenna and
the bilateral Vivaldi with dielectric (circular shape) is made to show improvement in the
gain performance. The gain versus frequency is shown in Figure 3.16, the dielectric
region help improves the gain. The combination of the dielectric plus the bilateral Vivaldi
gives two advantages. The first advantage is that the performance improves in the lower
frequency is improved by having a higher gain while the second advantage is
maintaining the gain at higher frequency.

66

(b)

(a)

(c)

Figure 3.6

(d)

Designs parameters of (a) Rod (b) Rectangular (c) Corrugated (d) Circular
shapes dielectric inserted into the aperture of the Bilateral Vivaldi.

67

Frequency (GHz)

0
0

5

10

15

20

-5

|S11| (dB)

-10

-15

-20
Rod Dielectric
Rectangular Dielectric
-25
Circular Dieletric
Corrugated Dieletric

-30
Figure 3.7

Simulated reflection coefficients of various shapes of dielectric inserted in
the aperture of the Bilateral Vivaldi.

68

Figure 3.8

The E-field of bilateral Vivaldi with a rod shape dielectric.

69

Figure 3.9

The E-field of bilateral Vivaldi with a rectangular shape dielectric.

70

Figure 3.10 The E-field of bilateral Vivaldi with a corrugated shape dielectric

71

Figure 3.11 The E-field of bilateral Vivaldi with a circular shape dielectric.

72

14

12

10

Gain (dB)

8

6
Corrugated Dielectric
4
Circular Dielectric
2

0
0

5

10

15

20

25

Frequency (GHz)

-2

-4

Figure 3.12 Simulated results of gain versus frequency of Corrugated and Circular
Dielectric shape.

73

Frequency (GHz)
0
0

5

10

15

20

-5

|S11| (dB)

-10

-15

-20

Bilateral without
dielectric

-25

Bilateral with dielectric

-30

-35

Figure 3.13 Simulated reflection coefficients of bilateral without dielectric and Bilateral
with dielectric Vivaldi.

74

14

12

10

Gain (dB)

8

6
Bilateral without
dielectric

4

Bilateral with dielectric

2

0
0

5

10

15

20

Frequency (GHz)

-2

-4

Figure 3.14 Simulated results of gain versus frequency of Bilateral without and with
dielectric Vivaldi.

75

(a)

(b)

(c)

(d)

(e)

(f)

Figure 3.15 Simulated radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz.

76

15

10

5

Simple Notch Vivaldi
Bilateral with Dielectric
Vivaldi

0
0

5

10

15

20

Frequency (GHz)

-5

-10
Figure 3.16 Simulated results of gain versus frequency of Simple Notch and Bilateral
with Dielectric Vivaldi.

77

3.5

Fabrication of Bilateral 3D Printed
Vivaldi with and without Dielectric
Loading

In the previous section different Vivaldi antenna designs were simulated. Some of the
designs show significant improvement in the overall performances. The design chosen
for fabrication was the bilateral section of 24.75mm loaded with a circular shape
dielectric. As in the previous chapter, the fabrication was carried out using 3D printed
machine (Objet Connex350). The polymer material chose for fabrication is Acrylonitrile
butadiene styrene (ABS) which was found to have the lowest loss among the materials
available for fabrication. The printed bilateral antenna was coated with a thin copper
using a sputtering machine (1µm). Prior to Cu deposition, a thin layer of titanium (150Å)
was deposited to enhance adhesion between ABS layer and the copper layer. In order
to integrate coax cable into the structure, the antenna was printed in two half pieces.
Alignment pins were printed on the half structures to ensure good alignment between
the two pieces.
Figure 3.17 shows the 3D printed bilateral Vivaldi antenna prior to the deposition
of the copper conductive layer. Figure 3.18 shows the same structures after Cu blanket
deposition. Figure 3.19 shows a completely assembled Vivaldi antenna structure. A
coax cable was inserted between the two half pieces to form a connected. The center
wire of the coax cable was extended through the central gap forming a coupler. The
other end was aligned using a small hole that was printed into the structure during the
3D fabrication. The dielectric (non Cu coated structure) was inserted in the slot region.

78

This structure is also built from ABS polymer material. This structure could be easily
inserted and removed during the measurements.

79

Figure 3.17 As fabricated bilateral Vivaldi prior to deposition of Cu layer and assembly.

80

Figure 3.18 Fabricated Bilateral Vivaldi after blanket copper coating on both sides of
the structures.

81

Figure 3.19 Fabricated Bilateral Vivaldi coated with copper plus the circular dielectric
with the coaxial cable place in the antenna.

82

3.6

Measurement of Antenna Reflection
Coefficient

The reflection coefficient of the antennas was measured using a vector analyzer, Agilent
N5227A, over a frequency range of 1 GHz to 20 GHz. The measured reflection
coefficient of each antenna as well as the simulated results is presented in Figure 3.20
for the 3D printed bilateral Vivaldi without the dielectric component and Figure 3.21 for
the 3D printed bilateral Vivaldi with dielectric inserted in the aperture of the antenna.
The measured and simulated results have a similar trend with the exception of
extra strong resonances in the measured results. This is largely attributed to the feed
point. The impedance matching was determined to be sensitive to the feed location in
the slot region. In the simulations the feeding point was optimize to give the best
reflection coefficient possible; however, during fabrication it is difficult to attain a good
match as the coax is mounted manually. Another factor that can effect is the fabrication
resolution, especially the dimension of the slot region.
In the 3D printed bilateral Vivaldi with dielectric insert, Figure 3.21, extra
resonances in the measured S11 are noticeable. In this design, the dielectric is inserted
in the metalized section. In this structure, there is an air gap presented between these
structures. This air gap affects the impedance matching, especially at lower frequencies.

83

0

5

Frequency (GHz)
10

15

20

0
-5
-10
-15

|S11| (dB)

-20
-25
-30
-35
Simulated
-40
Measured

-45
-50

Figure 3.20 Simulated and Measured of 3D printed Bilateral Vivaldi without dielectric
component.

84

Frequency (GHz)
0

5

10

15

20

0

-10

|S11| (dB)

-20

-30

-40
Simulated
-50
Measured
-60

-70

Figure 3.21 Simulated and Measured of 3D printed Bilateral Vivaldi with dielectric
component.

85

3.7

Measurement of Antenna Radiation
Characteristics

The radiation characteristic of the antennas was measured using a SATIMO near-field
measurement system. The measured gain as a function of frequency is shown in
Figures 3.22 and 3.23 without and with dielectric component, respectively. These
figures also show the simulated results.
Figure 3.22 shows discrepancy in the gain versus frequency. The increase
shows similar pattern of increase of decrease of the gain. However several
disagreements were shown around 2 to 4 dB of differences due to several factors. The
first reason might be because of the dimension of the design was a bit off compare to
the design in simulation. The resolution of the printer might cause some difference in
the dimension and also some residue of the material might still be intact on the antenna.
Secondly, due the sensitiveness of the coaxial position will cause the loss in the gain.
Loss in the coaxial and the system cables may give to the fact that the gain reduces
significantly. One of the other factors that give reduction in gain is the surface
roughness of the antenna. The uneven layer of copper during the sputtering process
can cause discrepancies towards the wave to propagate can cause the gain to
decrease.
On the other hand, in Figure 3.23 shows a much more reduction in the gain. The
same cause can be said as the above statement. In addition, several factors due the
dielectric also play a role in the inconsistency in the simulation and measured. In the
simulation the dielectric that was used without any loss considered. However, when the
86

fabrication was done, it is found that the dielectric properties have the loss tangent of
0.02. That loss tangent also causes the gain to decrease. Adding to the loss, there is
gap that was found in between the dielectric and the inside of the aperture of the
antenna. Due to the gap, the radiation might leak away causing lessen in gain.
A second simulation was done to verify the effect of the loss in the dielectric was
included in Figure 3.23 as well. It shows that the measure and the simulated have a
similar pattern but a discrepancy in the gain. This shows that the loss tangent plays a
role in the reduction of the gain. However that simulation does not take account of the
other losses which was due to the position of the feeding point, differences in the
dimension simulated and fabricated, and the surface roughness.
Further analysis was done in order to see the radiation pattern of Bilateral Vivaldi
with and without the dielectric. Figure 3.24 shows the radiation pattern that was
measured using a 3D SATIMO antenna measurement system. The measurement was
done at a specific frequency as a representative of low, mid and high frequency for 5,
10 and 15 GHz. It shows that the radiation pattern of the Bilateral Vivaldi with the
dielectric shows the gain to less that the bilateral Vivaldi without the dielectric. This is
due to the loss of the dielectric properties. However an interesting indication shows that
the dielectric has a lesser beamwidth compared to the antenna without the dielectric. It
shows that the dielectric helps focusing the beam but due to the loss tangent of the
dielectric causing the gain to decrease. The ABS was used as the dielectric because it
was the lowest loss dielectric material available for 3D printing. Based on the concept
shown the used of lesser lossy material allows the dielectric to function as predicted in
the simulation. As for future research a low loss material will be used.
87

12

10

8

6

4

Simulated
Measured

2

0

2

4

6

8

10
12
Frequency (GHz)

14

16

18

Figure 3.22 Simulated and Measured gain of 3D printed Bilateral Vivaldi without
dielectric component.

88

14

Simulated
(lossless)
Simulated
(loss)

12

Measured
10

8

6

4

2

0
2

4

6

8

10

12

14

16

18

Frequency (GHz)

Figure 3.23 Simulated and Measured gain of 3D printed Bilateral Vivaldi with dielectric
component. Simulations are carried out for dielectric component with and
without loss tangent.

89

(a)

(b)

(c)

(d)

(e)

(f)

Figure 3.24 Measured radiation patterns of (a)-(b) E and H-planes at 5 GHz, (c)-(d) E
and H planes at 10 GHz and (e)-(f) E and H-planes at 15 GHz.
90

3.8

Different of Dielectric Structure for
Antenna

In the modern age, the communication has become easier with the development of
wireless communication system technology. Different wireless systems have diverse
operating frequency bands. One of the easiest solutions in having multi operation
antenna is by adding more antennas in the system. This will lead the increase of the
device’s dimensions and as well as having trouble due to the coupling of each antenna
that was mounted. Based on these problems the need of having an antenna that can
operate in different range has developed interest in the design of a tunable antenna.
The research on tunable antennas has been studied before [85]-[86]. Several methods
have been successfully demonstrated that show the capability of tuning the resonant
frequency of antenna elements. One of the ways is by using electronic tuning. The
antenna was tune by using switchable capacitive load circuit which allows the antenna
to have a wider operating bandwidth [87].
In this section, an alternative way in tuning the operating frequency was shown.
Building on the advantages of 3D printed technology, more complex structure can be
made. In this section the design of different shapes of dielectric using 3D printed which
enable the tunability of antennas. As a proof of concept, a monopole antenna was used
to show the effectiveness of dielectric loaded element to tune the frequency of the
antenna. Monopole antenna was chosen because it is considered as one of the basic
antennas that have been used for communications purposes. This is due to the fact that
a monopole antenna is a simple design and the cost of fabrication is also low. A wire

91

monopole antenna has a specific characteristic which is it has a narrow bandwidth.
Taking advantage of this characteristic, the concept of 3D printed dielectric loaded
shows the capability to tune the operating frequency.

92

3.9

Dielectric Loaded Monopole
Antennas

The operating frequency of the monopole antenna can be tuned by changing the
dielectric properties of the surrounding medium. 3D printed dielectric structures can be
utilized to surround the monopole antenna. In the 3D printing, the dielectric constant of
the medium is fixed. Thus, instead of changing the dielectric constant of the surrounding
medium the shape of the structure was utilized to achieve frequency tuning. As a proof
of concept, several cylindrical pieces were fabricated to be used in dielectric loading the
antenna elements. The dielectric loading elements were fabricated using the same
technique described in the previous chapter. Several pieces with diameter of 5mm,
9mm and 13 mm were fabricated and photos of these structures are shown in Figure
3.5. These rings were used individually or by stacking several of these pieces. Figure
3.26 shows a monopole antenna surrounded by dielectric ring.
The characterization of the antenna was done by measuring the reflection
coefficients using a network analyzer, Agilent N5722A. The first measurement was done
by just using one piece of the cylindrical dielectric loaded pieces place wrapping the
wire monopole of each dimension. The S-parameters (S11) is then shown in Figure
3.27 to see the change of frequency. The main reference is the monopole without any
dielectric loaded was also measured at 9.75 GHz. Any shifting in frequency will indicate
that the dielectric elements act as a loading material. A clear shift in frequency can be
seen when the dielectric was placed on the wire monopole. As the dimension of the

93

dielectric increases the operated frequency shifted to the right. This shows that the
permittivity of the dielectric was present allowing the shift in frequency.
Following dielectric extra pieces with the same dimension was placed on top of
each other to see the effect of any shifting in frequency can be seen in Figure 3.28. The
appearance of two resonance peaks can be seen. The first resonance peaks show that
it was shifted to the left side while the second resonance shows the frequency shifted to
the right. The shifting is due to the diameter and height of the dielectric loaded.
This proves that the 3D printed structures can be used for dielectric loading that
enables the antenna resonant frequency shift. Further investigation will be done in the
future. One aspect that will be investigated is by using 3D printed granules. The 3D
printed granules configuration will look like a Lego shape. In this case the monopole
structure will be surrounded by the 3D granules to form a geometrical shape that allows
the operation frequency to be shifted according to the desired frequency.

94

Figure 3.25 Fabricated 3D cylindrical dielectric components.

Figure 3.26 Dielectric structure used in loading the antenna element.

95

4

6

Frequency (GHz)
8
10

12

14

0

-5

-10

-15
Monopole

-20
5mm Dielectric Piece

9mm Dielectric Piece

-25

13mm Dielectric Piece

-30
Figure 3.27 Measured reflection coefficients of a monopole loaded with different
diameter dielectric rings (5mm, 9mm and 13mm) dielectric pieces.

96

4

6

8

Frequency (GHz)
10

12

14

0

-5

-10

-15
monopole
5mm on 5mm
Dielectric
9 mm on 9 mm
Dielectric

-20

-25

-30
Figure 3.28 Measured reflection coefficients of a monopole loaded with bi-layer
dielectric rings for different diameters (5mm, 9mm and 13mm) dielectric
pieces.

97

3.10

Simulated Design of Granule Antenna
aka Lego Antenna

From the above measurements it is clear that dielectric loading can be used in the
design of novel antennas with improved performance. Here, a new type of antenna
structure is demonstrated that can be physically reconfigured called granule antenna.
Antennas have become an integral part of day-to-day electronics, ranging from handheld electronics to environment sensors. There is significant interest in reconfigurable
and tunable antenna elements so that they can adapt to their environment. Frequency
of operation of an antenna element can be tuned by loading with electronic tuning
elements (e.g., varactor diodes) or by physically changing the structure of the antenna.
Here a novel reconfigurable antenna design is introduced based on
rearrangement of physical layout of the antenna structure. The physical structure of an
antenna can be subdivided into small 3D granules and these granules can be
rearranged

to

form

any

geometry

(interchangeable

antenna).

The

idea

of

interchangeable antenna comes from the idea of using Lego shape material as a
building block in the assemblymen of an antenna. Lego blocks can be stacked to create
different 3D shape objects. Similarly, small 3D printed blocks (granules) conducting
blocks can be used to form any complex 3D antenna elements to achieve desired
performance (operating frequency and radiation pattern). For example, a simple
monopole antenna can be transformed to a folded antenna just by rearranging the
granules. Thus, a new design is obtained in a short time while avoiding remanufacturing

98

of new designs. Multiple structures can be made by using different shape of Lego like
granules to create a new antenna design.
As a proof of concept, several designs of 3D folded antenna with the addition of
3D printed blocks were simulated. Figure 3.29 to Figure 3.32 shows the design of the
antenna. In the simulation, the 3D block structures were made from ABS and also
copper. Simulated result is presented in Figure 3.33 shows the reflection coefficient of
the reference, first, second and third design of 3D folded antenna including the 3D block
structures. The reason for doing this is to see the interchangeable combination needed
to change the frequency of the antenna. The reference structure of the 3D folded
antenna shows the operational frequency of 2.81 GHz. By adding the 3D block
structures, the frequency is shifted and the new operating frequencies are 1.84 GHz,
1.71 GHz and 1.61 GHz, respectively. This shows the ability to tune the resonance
frequency by using different combinations of the 3D blocks structures. Furthermore,
this approach also allows in the minituarization of the antenna element. The fabrication
was done in order to verify the simulated results. However, due to the limitations of the
3D printed machine and also the sputtering machine the elements were difficult to
fabricate. In the future, further steps will be implemented in order to prove the concept
of this 3D printed granule based antenna.

99

Figure 3.29 Reference structure for a 3D folded antenna.

100

Figure 3.30 First Configuration of 3D folded antenna with additional of 3D printed
blocks.

101

Figure 3.31 Second Configuration of 3D folded antenna with additional of 3D printed
blocks.

102

Figure 3.32 Third Configuration of 3D folded antenna with additional of 3D printed
blocks.

103

Frequency (GHz)
1

1.5

2

2.5

3

3.5

4

0

-5

-10

Reference
First Design

-15

|S11| (dB)

2nd Design
3rd Design

-20

-25

-30

-35

Figure 3.33 Simulated reflection coefficients of 3D folded antennas.

104

3.11

Simulation and Measurement of 3D
Printed Patch Antenna

Patch (Microstrip) antenna is one of the widely used antennas due to its simplicity,
lightweight, inexpensive and compatibility. The basic structure of patch antenna consists
of a dielectric substrate in the middle of the metalized ground plane located on the
bottom side while metalized radiating patch at the top shown in Figure 3.29. A 3D patch
antenna was designed and simulated using HFSS. The dimension of the design was
given as well in Figure 3.29. In the simulation show that the patch antenna operates at
5.26 GHz. Based on the simulated design, a 3D printed patch antenna was fabricated
using 3D printing technology as use in previous fabrication. The substrate use is the
same material that has been used in the past to fabricate the Vivaldi antenna which is
ABS. The patch was metalized by using a sputtering machine where a copper layer was
placed. The fabricated 3D printed patch antenna is shown in Figure 3.30. The reflection
coefficient is measured using a vector analyzer device called Agilent N5227A network
analyzer. The comparison was made between the fabricated 3D printed patch antenna
and the simulated 3D patch antenna is shown in Figure 3.31. The operational frequency
for the measured 3D printed patch antenna was 3.48 GHz. The results show very good
agreement between the simulation and the measured data. The slight difference is most
likely due to the air gap located between the ground plane and the substrate.
Collectively, the result shows that a simple patch antenna can be fabricated using 3D
printing technology.

105

(a)

PATCH
SUBSTRATE
GROUND
PLANE

(c)

(b)
21.21 mm

.
4.2 mm

2mm

16.4mm
COAXIAL
CABLE

Figure 3.34 3D patch antenna design (a) 3D view (b) Top view and (c) Side view.

106

(a)

(b)

(c)

Figure 3.35 Fabricated 3D patch antenna design (a) 3D view (b) Top view and (c) Side
view.

107

Frequency (GHz)
3

3.5

4

4.5

5

5.5

6

6.5

0

-5

|S11| (dB)

-10

Simulated

-15

Measured
-20

-25

-30
Figure 3.36 Simulated and Measured of 3D printed patch antenna for reflection
coefficient.

108

7

3.12

Conclusion

The main focus of this chapter was to design 3D printed antenna that was able to
integrate 3D printed dielectric as well. The first design of the 3D printed Vivaldi antenna
was an improvement made from the previous chapter. The addition of bilateral pieces at
the end of the Vivaldi helps improve the bandwidth and the gain of the antenna. Further
modification of the antenna by placing 3D printed dielectric component into the antenna.
The dielectric component was used as a focusing element which guided the wave and
enables the beamwidth to be narrower. However, the fabricated 3D printed dielectric
has high loss (dielectric loss tangent). This resulted in a much lesser gain and
bandwidth as compared to simulation results.
Taking advantage of the 3D printing capability, 3D printed cylindrical dielectric
was developed to load the monopole antennas. The cylindrical dielectric was placed
onto a monopole that allows the monopole operational frequency to be shifted. The
dielectric component that was used act as a loading element that allows the tunability of
the monopole antenna. Using the same concept, a 3D granule structure was designed
to act as an interchangeable structure which is used to load a folded antenna. The
interchangeable structure allows the tunability of the folded antenna as well as in its
minituarization.
A 3D patch antenna was simulated and measured to show that the substrate
dielectric can be 3D printed. Overall the patch antenna shows reasonable similarity in
the operational frequency. The discrepancies are due to the air gap located between the
substrate and the ground plane (copper plate). The air gap effectively reduced the
109

dielectric constant of the substrate and thus the frequency shifts to higher values as
seen in the measured results.

110

Chapter 4
Conclusions
In this thesis, 3D printing technology has been used as a fabrication technique to
produce a range of antenna designs. 3D printing technology has shown its practical
application to fabricate limitless shape and structure that is suited for various
applications and novel antenna designs.
In Chapter 2, the fabrication of two Vivaldi antenna designs using metalized 3D
printed plastic-polymers is presented. The printed antennas with these materials provide
a low cost, light weight and an accurate fabrication solution. In addition, both antennas
exhibit a high maximum gain of around 12 dB as well as providing a wide bandwidth,
approximately 14.5 GHz. The antennas were fabricated using an ABS polymer material
and covered with a thin layer of sputtered copper. The measured and simulated results
are shown to match well, displaying the potential of 3D printing wideband antennas.
This antenna design using 3D printing is demonstrated for the first time under this
research work.

111

Chapter 3 shows approaches to improve the Vivaldi antenna design that can
readily be fabricated using 3D printing. A bilateral piece was added in order to improve
the impedance matching of the antenna and to further improve the bandwidth. Further
improvement in performance is achieved by incorporating a dielectric component in the
aperture region of the antenna. The dielectric was used as a focusing element to guide
the radiation energy. The simulated results showed improved bandwidth and higher
gain. However, the measured results showed several discrepancies from the simulated
results. This was largely due to the large loss (high tan-delta) associated with the ABS
polymer material used in guiding the wave. The performance of the antenna can be
improved by replacing this material with a lower loss dielectric. However, this antenna
design demonstrated that 3D printing allows the integration of dielectric and metals to
form novel structures.
As a further development, the 3D printed dielectric was used to design a
reconfigurable antenna through dielectric loading. Cylindrical dielectric pieces with
different diameter were placed onto a monopole which enables the frequency of the
monopole to be shifted dictated by the size of the ring structure. Furthermore, a novel
antenna design is shown which utilizes 3D granule structures that can be physically
arranged in any configuration to reconfigure an antenna element, similar to Lego
structures. The granule structures can be made both conductive and non-conductive
and their combination allows for novel antenna designs. A simple printed patch antenna
is also demonstrated with utilizes the 3D printed ABS as a substrate material. The
measured and simulated results match very closely. The slight discrepancies noted

112

were largely due to the presence of air gap in between the ABS substrate and the
ground plane.
The work of this thesis demonstrated the applicability of 3D printing in the design
and fabrication of novel antenna structures. This technology not only allows in the
design of complex 3D structures, but also allows in the integration of conductive and
non-conductive regions that provides another degree of design flexibility. Overall, 3D
printing allows in the design of complex 3D antennas that would have been difficult to
fabricate using conventional microfabrication approaches. Thus, this technology proves
to be beneficial in the design of antenna elements and their integration in a host of
electronic platforms.

Future work
As proven, the capability of 3D printing technology shows that it is a reliable way of
fabricating antenna as well as dielectric component for the antenna. Further research
will be done to fabricate microwave component such as waveguide, horn antennas,
directional couples as well as other microwave devices. Furthermore, novel structures
having interwoven metallic and dielectric regions (e.g., dielectric loaded antennas) can
be designed which would be difficult to achieve using conventional fabrication
approaches. Further work also includes integrating less lossy material for the dielectric
components. Furthermore, the granules structure will be fabricated through 3D printing
of plastic parts followed by blanket metallization. 3D printing (or additive manufacturing)
allows in the fabrication of complex 3D parts which can be metalized through thermal
evaporation or electroless plating. A host of structures has been designed and utilized in
113

the assembly of various 3D antenna structures (e.g., monopole, patch and Yagi
antennas) and these designs will be presented in this paper. The proposed approach
allows in the design of complex antennas that can readily be assembled and tested.
This approach opens a new approach to design and test antenna elements prior to
mass manufacturing. Also, it can be adopted as an educational tool to train next
generation of antenna design engineers.

114

BIBLIOGRAPHY

115

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[3]

Patterson, Leland W., and J. B. Sollberger. "Replication and classification of
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