UWB MICROSTRIP PATCH ANTENNA WITH FLOWER SHAPED …€¦ · ii BONAFIDE CERTIFICATE Certified that...
Transcript of UWB MICROSTRIP PATCH ANTENNA WITH FLOWER SHAPED …€¦ · ii BONAFIDE CERTIFICATE Certified that...
UWB MICROSTRIP PATCH ANTENNA
WITH FLOWER SHAPED PATCH AND
CAVITY STRUCTURE
A PROJECT REPORT
Submitted by
SOORYA R
Register No: 14MCO023
in partial fulfillment for the requirement of award of the degree
of
MASTER OF ENGINEERING
in
COMMUNICATION SYSTEMS
Department of Electronics and Communication Engineering
KUMARAGURU COLLEGE OF TECHNOLOGY
(An autonomous institution affiliated to Anna University, Chennai)
COIMBATORE-641049
ANNA UNIVERSITY: CHENNAI 600 025
APRIL 2016
ii
BONAFIDE CERTIFICATE
Certified that this project report titled “UWB MICROSTRIP PATCH ANTENNA WITH
FLOWER SHAPED PATCH AND CAVITY STRUCTURE” is the bonafide work of
SOORYA.R [Reg. No. 14MCO023] who carried out the research under my supervision.
Certified further, that to the best of my knowledge the work reported herein does not form
part of any other project or dissertation on the basis of which a degree or award was conferred
on an earlier occasion on this or any other candidate.
HHHH
The Candidate with Register No. 14MCO023 was examined by us in the
project viva –voice examination held on............................
INTERNAL EXAMINER EXTERNAL EXAMINER
SIGNATURE
Prof.K.Ramprakash
PROJECT SUPERVISOR
Department of ECE
Kumaraguru College of Technology
Coimbatore-641 049
SIGNATURE
Dr. A.VASUKI
HEAD OF THE DEPARTMENT
Department of ECE
Kumaraguru College of Technology
Coimbatore-641 049
iii
ACKNOWLEDGEMENT
First, I would like to express my praise and gratitude to the Lord, who has
showered his grace and blessings enabling me to complete this project in an excellent
manner.
I express my sincere thanks to the management of Kumaraguru College of
Technology and Joint Correspondent Shri Shankar Vanavarayar for his kind support
and for providing necessary facilities to carry out the work.
I would like to express my sincere thanks to our beloved Principal
Dr.R.S.Kumar Ph.D., Kumaraguru College of Technology, who encouraged me with
his valuable thoughts.
I would like to thank Dr.A.Vasuki Ph.D., Head of the Department, Electronics
and Communication Engineering, for her kind support and for providing necessary
facilities to carry out the project work.
In particular, I wish to thank with everlasting gratitude to the Project Coordinator
Dr.M.Alagumeenaakshi Ph.D., Asst. Professor-III, Department of Electronics and
Communication Engineering, throughout the course of this project work.
I am greatly privileged to express my heartfelt thanks to my project guide
Mr.K.Ramprakash, Department of Electronics and Communication Engineering, for
her expert counselling and guidance to make this project to a great deal of success and
I wish to convey my deep sense of gratitude to all teaching and non-teaching staff of
ECE Department for their help and cooperation.
Finally, I thank my parents and my family members for giving me the moral
support and abundant blessings in all of my activities and my dear friends who helped
me to endure my difficult times with their unfailing support and warm wishes.
iv
ABSTRACT
Ultra-Wideband antennas ranging from 3.1 to 10.6 GHz ,have gained increasing
attention mainly because of the high data transmission rates, well beyond those possible
with currently available technologies such as 802.11a, b, g, Wi-Max, etc. A UWB
antenna with dual polarization is designed and simulated using ANSYS HFSS
simulation software and its performance was analyzed. The proposed structure of the
antenna is designed with a hexagon shape and a flower shaped patch and their results
are compared to know the best among the two shapes. It is found that Flower shaped
patch structure gives better results and the structure consists of a flower shaped patch
with two ports and four capacitively coupled feeds. The four feeds are formed from two
shapes : Trapezoidal shape and Triangular shape which forms a vertical patch and a
horizontal patch respectively . The feeds excite a square radiating patch as they are
placed at the center of the antenna structure. The feeds are connected to the microstrip
lines, which are printed on the dielectric substrate (FR4), via holes. Two tapered baluns
are used for getting differential feeds and for exciting the entire antenna structure to
improve the gain and also to achieve high isolation between the two ports. Port 1
provides Horizontal Polarization and Port 2 provides Vertical Polarization. The return
loss measured for the dual polarized antenna with the hexagon shape is -10.7dB, the
measured VSWR is 1.8 and the measured antenna gain value is 0.784dB. The return
loss measured for the dual polarized antenna with the Flower shaped patch is -20.04dB,
the measured VSWR is 1.2 and the measured antenna gain value is 1.8485dB.A Cavity
structure is then introduced into the flower shaped patch design for the sake of
improvement in gain of the proposed design and the results are analyzed. It is found that
gain of 2.1989dB is got from the cavity structure. The main characteristic of UWB
Antennas is the ability to provide Polarization Diversity, which enhances the channel
capacity significantly. This makes them more attractive than the usual antennas with
linear polarization.
iv
TABLE OF CONTENTS
CHAPTER
NO.
TITLE PAGE
NO.
ABSTRACT iv
LIST OF FIGURES x
LIST OF TABLES xiii
LIST OF ABBREVIATIONS xiv
1 INTRODUCTION 1
1.1 ULTRA-WIDEBAND TECHNOLOGY 1
1.2 TYPES OF UWB ANTENNAS 2
1.3 WHY UWB OVER NARROWBAND SYSTEMS? 4
1.3.1 Narrowband Systems 4
1.3.2 UWB Systems 4
1.3.3 Shannon’s Formula 5
1.4 APPLICATIONS OF UWB 6
1.5 UWB CHARACTERISTICS 6
1.6 ADVANTAGES OF UWB 6
1.7 DISADVANTAGES OF UWB 7
2 LITERATURE SURVEY 8
3 ANTENNAS AND THEIR BASIC TERMINOLOGIES 12
3.1 TERMINOLOGIES 12
3.1.1 Radiation Pattern 12
3.1.2 Field Regions 13
3.1.3 Directivity 13
3.1.4 Gain 13
3.1.5 Antenna Polarization 14
3.1.6 Antenna Bandwidth 14
3.2 MICROSTRIP PATCH ANTENNA 15
3.2.1 Advantages 15
3.2.2 Disadvantages 16
3.3 FEEDING TECHNIQUES 16
3.3.1 Microstrip line Feeding 17
3.3.2 Coaxial probe feed 17
3.3.3 Proximity coupled feed 18
3.3.4 Aperture coupled feed 19
4 SINGLE & DUAL POLARIZED MICROSTRIP PATCH
ANTENNA DESIGN
20
4.1 SINGLE POLARIZATION OF UWB ANTENNA 20
4.1.1 Polarization of Antenna 20
4.1.2 Simulated Design in HFSS 22
4.2 DUAL POLARIZATION OF ANTENNAS 25
4.2.1 Polarization Diversity 25
4.2.2 Dual Polarization Techniques 25
4.3 DESIGN OF DUAL POLARIZED PATCH ANTENNA 26
4.3.1 Existing Design 27
4.3.2 Simulated Design using HFSS 27
4.4 MODIFICATIONS ON DUAL POLARIZED PATCH
ANTENNA
29
4.4.1 Proposed antenna geometry with Hexagon shape 29
4.4.2 Proposed antenna geometry with Flower Patch 30
4.4.3 Flower shaped patch with cavity structure 32
5 SIMULATION RESULTS 34
5.1 HFSS 34
5.2 RETURN LOSS 35
5.2.1 Single Polarized Antenna Return Loss 35
5.2.2 Dual Polarized Antenna Return Loss 36
5.2.3 Return Loss of UWB Dual Polarized Antenna with
Hexagon shaped patch
36
5.2.4 Return Loss of UWB Dual Polarized Antenna with Flower
shaped patch
37
5.3 VSWR 37
5.3.1 Single Polarized Antenna VSWR 38
5.3.2 Dual Polarized Antenna VSWR 38
5.3.3 VSWR of UWB Dual Polarized Antenna with Hexagon
shaped patch
39
5.3.4 VSWR of UWB Dual Polarized Antenna with Flower
shaped patch
39
5.4 GAIN 40
5.4.1 Single Polarized Antenna Gain 40
5.4.2 Dual Polarized Antenna Gain 41
a) Horizontal Polarization 41
b) Vertical Polarization 41
5.4.3 Gain of UWB Dual Polarized Antenna with Hexagon
Shaped patch
42
5.4.4 Gain of UWB Dual Polarized Antenna with Flower shaped
patch
42
5.4.5 Cavity-backed UWB Dual Polarized Antenna with Flower
Shaped patch Gain
43
5.5 3D PLOT 43
5.5.1 Single Polarization 43
5.5.2 Dual Polarization 44
5.5.3 3D Polar Plot of Hexagon patch UWB Dual Polarized
Antenna
44
5.5.4 3D Polar Plot of Flower shaped Patch UWB Dual
Polarized Antenna
45
6 CONCLUSION AND FUTURE WORK 46
REFERENCES 47
LIST OF PUBLICATIONS 50
x
LIST OF FIGURES
FIGURE
NO.
CAPTION PAGE
NO.
1.1 Log periodic antenna 2
1.2 Biconical antenna 2
1.3 Horn antenna 3
1.4 Omni-directional and Directional antennas 3
1.5 Narrow Systems 4
1.6 UWB Systems 5
3.1 Microstrip Patch Antenna 15
3.2 Microstrip Line feed 17
3.3 Co-axial Probe feed 18
3.4 Proximity Coupled feed 18
3.5 Aperture Coupled feed 19
4.1 Single Polarized Microstrip Patch UWB Antenna 21
4.2 Simulated Single Polarized Antenna Structure 22
4.3 Design Evolution from the basic monopole to the
UWB Antenna
23
4.4 Dual polarized Microstrip Patch Antenna Structure 27
4.5 Simulated Design of Dual Polarized Microstrip Patch
Antenna
27
4.6 Simulated Design of Hexagon shape Patch Dual
Polarized Microstrip Patch Antenna
29
4.7 Simulated Design of Flower shaped Patch Dual
Polarized Microstrip Patch Antenna – Top view
30
xi
4.8 Simulated Design of Flower shaped Patch Dual
Polarized Microstrip Patch Antenna – Side view
31
4.9 Internal connection of the four capacitively coupled
feeds
31
4.10 Simulated Design of Cavity-Backed Flower shaped
Patch Dual Polarized Microstrip Patch Antenna – Top
view
32
4.11 Simulated Design of Cavity-Backed Flower shaped
Patch Dual Polarized Microstrip Patch Antenna –
Side view
33
5.1 Single Polarized Antenna Return loss 35
5.2 Dual Polarized Antenna Return loss 36
5.3 Hexagon Patch –UWB Dual Polarized Antenna
Return loss
36
5.4 Flower shaped Patch –UWB Dual Polarized Antenna
Return loss
37
5.5 Single Polarized Antenna VSWR 38
5.6 Dual Polarized Antenna VSWR 38
5.7 Hexagon patch- UWB Dual Polarized Antenna
VSWR
39
5.8 Flower shaped Patch - UWB Dual Polarized Antenna
VSWR
39
5.9 Single Polarized Antenna Gain 40
5.10 Dual Polarized Antenna Gain
a) Horizontal polarization
b) Vertical polarization
41
5.11 Hexagon patch – UWB Dual Polarized Antenna Gain 42
xii
5.12 Flower shaped patch – UWB Dual Polarized Antenna
Gain
42
5.13 Cavity-backed UWB Dual-Polarized antenna with
flower shaped patch gain
43
5.14 3D Polar Plot for Single Polarized Antenna 43
5.15 3D Polar Plot for Dual Polarized Antenna 44
5.16 3D Polar Plot for Hexagon patch UWB Dual-
Polarized Antenna
44
5.17 3D Polar Plot for Flower shaped patch UWB Dual-
Polarized Antenna
45
xiii
LIST OF TABLES
TABLE NO.
CAPTION PAGE NO.
4.1 Single Polarized Antenna Parameters 24
4.2 Design Parameters of Dual- Polarized Microstrip Patch
Antenna
28
4.3 Dimensions of the Proposed Antenna 30
4.4 Comparison of Hexagon and Flower shape Patch 46
xiv
LIST OF ABBREVIATIONS
UWB Ultra-Wide Band
HFSS High Frequency Structure Simulator
FR4 Flame retardant
VSWR Voltage Standing Wave Ratio
RF Radio Frequency
FCC Federal Communication Commission
PSD Power Spectral Density
SNR Signal to Noise Ratio
FDTD Finite Difference Time Domain
GSM Global System for Mobile
communication
UMTS Universal Mobile Telecommunications System
1
CHAPTER 1
INTRODUCTION
1.1 ULTRA-WIDEBAND TECHNOLOGY
Ultra-wideband (UWB) communication is a wireless technology for
transmitting large amounts of digital data over a wide frequency spectrum using short
pulses at very low power densities. UWB helps in freeing people from wires by
providing wireless connection of multiple devices for transmission of video, audio and
other high bandwidth data. UWB commonly refers to a system that either has a large
absolute bandwidth of more than 500MHz.UWB technology received a major boost
especially in 2002 since the US Federal Communication Commission (FCC)
permitted the authorization of using the unlicensed frequency band starting from 3.1
to 10.6 GHz for commercial communication applications. Ultra-wideband
communications is fundamentally different from all other communication techniques
because it employs extremely narrow RF pulses to communicate between transmitters
and receivers. Utilizing short-duration pulses as the building blocks for
communications directly generates a very wide bandwidth and offers several
advantages, such as large throughput, covertness, robustness to jamming, and
coexistence with current radio services.
The major step in the development of UWB technology for wireless
communications is the UWB antenna. UWB antennas have been in active commercial
use for decades. UWB antennas provide impedance transformation and gain in the
desired direction across the operating band of 3.1 to 10.6 GHz. UWB antennas are
highly efficient in radiating electromagnetic energy due to the fact that the transmit
power of a UWB system is very low (-41.3dBm/MHz).A wide variety of antennas are
suitable for use in ultra-wideband applications.
2
1.2 TYPES OF UWB ANTENNAS
UWB antennas can be classified into four main categories:
1. Frequency dependent antennas: These antennas are larger in size and can be used
only if waveform dispersion across the field of view may be tolerated. They can
be operated in the 3.1 to 10.6 GHz frequency band but are not recommended for
indoor wireless communication applications, mobiles, portable devices, etc. Log
periodic antennas are the best example for this kind of antennas.
Fig.1.1 Log periodic antenna
2. Small-element antennas: These are small, Omni-directional antennas having low
gain, wide field of view and small antenna size and mainly used for commercial
applications . Example of this types of antennas are bi-conical antennas.
Fig.1.2 Biconical antenna
3
3. Horn antenna : These are electromagnetic funnels that concentrate energy in a
specific direction .These antennas have large gain ,and narrow beam and are
bulkier than the small-element antennas.
Fig.1.3 Horn antenna
4. Reflector antennas : These antennas are high gain antennas that radiate energy in a
particular direction. They are relatively large but easy to adjust by manipulating the
antenna feed. Hertz’s parabolic cylinder reflector antenna is an example of this kind of
antenna.
Fig.1.4 Omni-directional and Directional antennas
4
1.3 WHY UWB OVER NARROWBAND SYSTEMS?
Ultra-wideband (UWB) technology offers a promising solution to the RF
spectrum drought by allowing new services to coexist with current radio systems with
minimal or no interference.
1.3.1 NARROWBAND SYSTEMS
Traditional narrowband communications systems modulate continuous
waveform RF signals with a specific carrier frequency to transmit and receive
information. A continuous waveform has a well-defined signal energy in a narrow
frequency band but makes it very vulnerable to detection and interception.
Fig.1.5 represents a narrowband signal in the time and frequency domain.
Fig.1.5 Narrowband Systems in a) time domain b) frequency domain
1.3.2 UWB SYSTEMS
UWB systems use carrier less, short-duration pulses with a very low duty cycle
for transmission and reception of the information. A simple definition for duty cycle is
the ratio of the time that a pulse is present to the total transmission time. Figure 1–3
and Equation 1–1 represent the definition of duty cycle.
Duty Cycle =𝑇𝑜𝑛
𝑇𝑜𝑛+𝑇𝑜𝑓𝑓 (1.1)
Low duty cycle offers a very low average transmission power in UWB
communications systems. The average transmission power of a UWB system is on the
order of microwatts, which is a thousand times less than the transmission power of a
5
cell phone. UWB devices require low transmit power due to this control over the duty
cycle, which directly translates to longer battery life for handheld equipment. Since
frequency is inversely related to time, the short-duration UWB pulses spread their
energy across a wide range of frequencies with very low power spectral density
(PSD).
Fig 1.6 illustrates UWB pulses in time and frequency domains.
Fig.1.6 UWB Systems in a) time domain b) frequency domain
1.3.3 SHANNON’S FORMULA
The greatest advantage of UWB is evident from the famous Shannon formula
for the capacity of a band-limited channel in Gaussian noise :
C= W log (1 + 𝑆
𝑁 ) bits/second (1.2)
Shannon’s formula gives how many bits of information per second can be
transmitted without error over a channel with a bandwidth of W Hz when the average
signal power is limited to S watt and the signal is exposed to an additive, white
(uncorrelated) noise of power N with Gaussian probability distribution.
The essential elements of “Shannon’s formula” are:
1) The channel bandwidth sets a limit to how fast symbols can be transmitted over the
channel.
2) The signal-to-noise ratio (S/N) determines how much information each symbol can
represent. The signal and noise power levels are measured at the receiver end of the
channel. Thus, the power level is a function of both transmitted power and the
attenuation of the signal over the transmission medium (channel). Shannon’s equation
6
shows that increasing channel capacity requires linear increases in bandwidth while
similar capacity increases would require exponential increases in power.
1.4 APPLICATIONS OF UWB:
1. Home network application
2. Position location and tracking
3. Used in Radars for military applications.
1.5 UWB CHARACTERISTICS:
UWB has a number of features which make it attractive for consumer
communications applications. In particular, UWB systems
(i) have potentially low complexity and low cost;
(ii) have a noise-like signal spectrum;
(iii) are resistant to severe multipath and jamming;
(iv) have very good time-domain resolution allowing for location and tracking
applications.
1.6 ADVANTAGES OF UWB:
1. UWB has an ultra- wide frequency bandwidth due to which it can achieve huge
capacity as high as hundreds of Mbps or even several Gbps.
2. UWB system delivers high performance in multipath channels.
3. UWB systems operate at extremely low power transmission levels.
4. UWB provides highly secure and reliable communication due to the low
energy density.
5. UWB can work with low SNR’s (works in noisy environments) and provides
resistance to jamming.
1.7 DISADVANTAGES OF UWB
1. Due to the low transmission power, information can travel only short distances.
2. Detecting the desired user’s information is more challenging than in the
narrowband communication due to multiple-access interference.
7
CHAPTER 2
LITERATURE SURVEY
[1] STUDY OF PRINTED ELLIPTICAL/CIRCULAR SLOT ANTENNAS
FOR ULTRAWIDEBAND APPLICATIONS
This paper presents two novel designs of planar elliptical slot antennas exhibit
an ultra- wideband characteristic when printed on a dielectric substrate and fed by
either tapered microstrip line or coplanar waveguide. In both designs, a U-shaped
tuning stub is introduced to enhance the coupling between the slot and the feed line so
as to broaden the operating bandwidth of the antenna. It is also found that these
antennas are nearly omnidirectional over a majority fraction of the bandwidth. The
slot dimension, the distance and the slant angle are the most important design
parameters that determine the antenna performance. These features and their small
sizes make them attractive for future UWB applications.
[2] A BRIEF HISTORY OF UWB ANTENNAS
This paper provides an historical overview of ultra-wideband antennas
presenting key advances at the root of modern designs. Ultra-Wideband has its roots
in the original “spark-gap” transmitters that pioneered radio technology. The past
century witnessed the development of an incredibly wide variety of UWB antennas.
This paper highlights a few particularly noteworthy UWB antennas as a starting point
for further explorations.
8
[3] DUAL-POLARIZED MAGNETO-ELECTRIC DIPOLE WITH
DIELECTRIC LOADING
A dual-polarized magneto-electric dipole loaded with dielectric substrate is
presented .The antenna consists of shorted-circuited patches, planar dipoles and is fed
by four probes. A method for reducing the size of the magneto-electric dipole by
loading the antenna with dielectric material of permittivity 2.65 is presented in this
paper. Both electric and magnetic dipoles are excited to achieve wide bandwidth and
good performance over the frequency band.
[4] DUAL-POLARIZED SLOT-COUPLED PLANAR ANTENNA WITH
WIDE BANDWIDTH
A new dual-polarized slot-coupled microstrip patch antenna is presented which
achieves high-isolation low cross-polarization levels and a wide bandwidth. The
coupling slot is an H-shaped slot. To achieve a wide bandwidth, stacked microstrip
patches with an air layer in between are used. The theoretical analysis is based on the
finite-difference time-domain (FDTD) method. First, to understand the effects of
various parameters on the antenna characteristics, a parametric study on the input
impedance of the antenna with a single input port is presented. Based on the results, a
dual-polarized microstrip antenna is designed.
[5] WIDEBAND DUAL-POLARIZED MICROSTRIP PATCH EXCITED
BY HOOK SHAPED PROBES
A new design of a wideband dually-polarized shorted microstrip patch antenna
coupled to hook shaped probes is presented. The antenna is designed to operate
around 4 GHz. The use of shorted microstrip patch antenna coupled to a hook shaped
probe feeding technique for wideband dual polarized microstrip patch antenna with
high isolation is proposed in this paper. The mechanisms of the shorted dual polarized
microstrip patch antenna provide wider bandwidth than full size microstrip patch
antennas with high decoupling between two input ports.
9
[6] DESIGN OF DUAL-POLARIZED L-PROBE PATCH ANTENNA
ARRAYS WITH HIGH ISOLATION
An experimental study of a dual-polarized L-probe patch antenna is presented.
A “dual-feed” technique is introduced to achieve high isolation between two input
ports. The problem of high input-port coupling in a dual-polarized patch antenna
consisting of vertical metallic probes is solved in this paper. Two methods for
improving the isolation between two adjacent elements of an antenna array have also
been investigated, including the introduction of slots in the ground plane and the use
of vertical metallic walls surrounding the patches.
[7] DUAL-POLARIZED WIDE-BAND APERTURE STACKED PATCH
ANTENNAS
The antenna is based upon an aperture stacked patch layout and incorporates a
simple dual-layered feeding technique to achieve dual-polarized radiation. The design
and develop of a dual polarized broadband printed antenna capable of operation over a
50% impedance bandwidth and high gain is presented in this paper. The solution for
this problem utilizes a dual polar, broadband reflector patch below the feed/antenna
ground plane which improves the front-to-back ratio (FBR) of the element to more
than 20 dB across the band of interest, a key aspect for sectorized cellular base
stations and an issue with most aperture solutions.
[8] A HIGH-ISOLATION, WIDEBAND AND DUAL-LINEAR
POLARIZATION PATCH ANTENNA
The design of a dual-polarization stacked patch antenna to be used in GSM-
UMTS base station arrays is presented. The major advantage of this set up is the
isolation between the two polarization ports of the same element in the antenna
operating bandwidth. A small, compact and single-fed CP stacked patch is presented
10
to cover all GPS bands. A key feature of this design is the integrated branch-line
hybrid, which achieves CP excitation for the stacked patches.
[9] POLARIZATION DIVERSITY IN ULTRA-WIDEBAND IMAGING
SYSTEMS
This paper presents an Ultra-Wideband (UWB) indoor imaging system with
dual-orthogonal polarized antennas. Both the measurement setup and the algorithm
implemented for data processing are introduced. Importance is given to the
polarization diversity, through which additional properties of objects such as form,
surface structure and orientation are investigated. The measured results show, that the
detection capability of a UWB indoor imaging system can be improved by exploiting
polarization diversity scheme. The resulting microwave image provides a more
extensive information about the form, orientation and dimensions of the target, in
comparison to single polarized systems.
[10] WIDEBAND DUAL-POLARIZED PATCH ANTENNA WITH
BROADBAND BALUNS
The use of a pair of novel 180° broadband microstrip baluns as a means of
achieving improved isolation and better cross-polarization suppression over a wider
bandwidth is proposed in this paper. The proposed 180° broadband balun delivers
both equal amplitude power division and consistent 180° phase shifting over a
wideband. For the dual-polarized quadruple L-probe square patch antenna, the use of
the proposed 180° broadband balun pair, in place of the conventional 180°
narrowband balun pair, allowed for improved input port isolation over a wider
frequency range, and reduced H-plane cross-polarization levels.
11
CHAPTER 3
ANTENNAS AND THEIR BASIC TERMINOLOGIES
The wireless systems have become an essential part of human life and almost
all the electrical and electronic equipment which we use, work with wireless
technologies. An antenna is an essential element of the wireless system. An Antenna
is an impedance matching between free space and guiding device. It is an electrical
device which transmits the electromagnetic waves into the space by converting the
electric power given at the input into the radio waves and at the receiver side the
antenna intercepts these radio waves and converts them back into the electrical power.
There are so many systems that uses antenna such as remote controlled television,
cellular phones, satellite communications, spacecraft, radars, wireless phones and
wireless computer networks. Day by day new wireless devices are introducing which
increase the demand of compact antennas.
3.1 TERMINOLOGIES
3.1.1 Radiation Pattern
Radiation pattern of an antenna is graphical representation of radiated power at as
fix distance from the antenna as a function of azimuth and elevation angle. The
antenna pattern shows how the power is distributed in the space.
There are three different types of antenna patterns:
a. Omnidirectional Antennas :
Omnidirectional antenna can be referred as an antenna has radiation pattern
uniform and equally distributed in one plane generally referred to horizontal
planes.
12
b. Directional Antennas:
Directional antennas concentrate their radiation in a particular direction. They
are also known as Beam Antenna.
c. Isotropic radiator:
An Isotropic antenna has the radiations distributed uniformly in all direction.
An isotropic antenna radiates all the power given.
3.1.2 Field Regions
The field regions can be categorized in Far field region and Near Field
(Fresnel) Region. Far field region is the region beyond the Fraunhofer distance called
Fraunhofer region.
R= 2𝐷2
𝜆 (3.1)
where R= distance from antenna
D= larger dimension of antenna
𝜆 =wavelength in free space.
3.1.3 Directivity
Directivity of an antenna shows that how much the antenna is able to radiate in
a particular given direction.
Directivity =𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑟𝑎𝑖𝑎𝑡𝑖𝑜𝑛 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 (3.2)
3.1.4 Gain
Antenna Gain is also referred as Power gain or simply Gain. This combines of
antenna efficiency and directivity. For a transmitting antenna it shows how efficiently
13
antenna is able to radiate the given power into space in a particular direction. While in
case of receiving antenna it shows how well the antenna is to convert the received
electromagnetic waves into electrical power.
3.1.5 Antenna Polarization
Polarization of an antenna is polarization of the electromagnetic waves radiated
from the antenna. Polarization on a wave is the orientation or path traces by the
electric field vector as a function of time. Polarization can be categorized in three
parts :
a. Linear polarization
b. Circular polarization
c. Elliptical polarization.
If the electric field vector of the wave at a given point in space follows a linear
path then the polarization is linear. Linear polarization is of two types Vertical and
Horizontal. In case of circular and elliptical polarization electric field vector follows a
circular and elliptical path. They can be Left hand polarized, if the electric field vector
tracking the path by making clockwise rotation and Right hand polarized, if the vector
tracking the path by making anti clockwise rotation.
3.1.6 Antenna Bandwidth
Antenna bandwidth is another important parameter of antenna can be described
as the range of frequencies over which antenna fulfil some desired characteristics.
The impedance bandwidth is the range of frequencies over which the input impedance
of antenna is perfectly matched to the characteristic impedance of the feeding
transmission line.
14
3.2 MICROSTRIP PATCH ANTENNA:
There is an increase in demand for microstrip antennas with improved
performance for wireless communication applications are widely used for this purpose
because of their planer structure, low profile, light weight moderate efficiency and
ease of integration with active device.
Fig.3.1 Microstrip Patch Antenna
The relative permittivity and height of the microstrip patch antenna ranges between :
2.2 ≤ εr ≥ 12 (3.3)
0.003λo ≤ h ≥ 0.05λo (3.4)
3.2.1 Advantages
Inexpensive and easy to fabricate.
Can be planted easily on any surface.
Can easily get reconfigurable characteristics.
Can easily design antenna with desired polarization.
Mechanically robust, Resistant against vibration and shock.
Suitable to microwave integrated circuits (MICs).
15
For high gain and directivity Array of antennas can be easily formed.
3.2.2 Disadvantages
High quality factor.
Cross polarization.
Poor polarization efficiency.
Suffers from spurious feed radiation.
Narrow impedance bandwidth (5% to 10% without any technique)
High Dielectric and conductor losses.
Sensitive to environment conditions like temperature and humidity.
Suffers from surface wave when high dielectric constant material is used.
Low gain and power handling capability.
3.3 FEEDING TECHNIQUES
Microstrip line
Coaxial probe
Proximity coupling
Aperture coupling
16
3.3.1 Microstrip line Feeding:
Fig 3.2 Microstrip Line feed
Radiating patch is directly fed by the microstrip feed line and has a narrow
width as compare to patch. This feeding technique is simple to fabricate and can be
every easily made compatible with the impedance matching techniques.
Disadvantages are this feed suffers from spurious feed radiation and surface wave
losses and also has low bandwidth.
3.3.2 Coaxial probe feed
One of the widely used feeding technique for microstrip antenna. In this type of
feeding,core of the coaxial cable is directly connected to the patch using the soldering
and the outer cable is connected to the ground. Core conductor is inserted in the
substrate via a hole. The main advantage of this feeding is that we can directly feed or
connect the inner conductor to the feed point where the input impedance is equal to
the characteristic impedance of the feed line.
17
Fig 3.3 Co-axial Probe feed
3.3.3 Proximity coupled feed
Two types of dielectric substrates are used in this type of feeding. Microstrip
line is not directly connected to patch and left open ended and is sandwiched between
the substrates. Energy from feed line is coupled electromagnetic to the radiating patch.
This type of feeding has largest bandwidth as compared to others. It is easy to model
and has low spurious feed radiation however its fabrication is more difficult because
the exact alignment of feedline is required.
Fig 3.4 Proximity Coupled feed
18
3.3.4 Aperture coupled feed
This feeding also uses two type of substrate ground plane is placed between
them and microstrip line is used generally to feed which is placed below the lower
substrate. the energy is electromagnetically coupled to the patch through an aperture
or slot made in the ground plane.
Fig 3.5 Aperture Coupled feed
19
CHAPTER -4
SINGLE & DUAL POLARIZED MICROSTRIP PATCH
ANTENNA DESIGN
4.1 SINGLE POLARIZATION OF UWB ANTENNA
4.1.1 Polarization of Antenna
The polarization of an antenna refers to the orientation of the electric field for
the maximum radiation. If an antenna produces an electric field which is parallel to
Earth (ground) , then it is considered to be Horizontally Polarized and if the antenna
produces an electric field perpendicular to ground ,then it is said to be Vertically
Polarized. To achieve maximum range, both the transmitter and receiver antennas
should be oriented with the same polarization.
The transmission characteristics of both polarizations are very similar at
microwave frequencies. However, the effects of obstacles and reflections within the
microwave link degrades the system performance in horizontal polarization than in
vertical polarization and thus vertical polarization tends to be the first polarization of
choice.
Microwave antennas will generally be either single polarized or dual polarized.
A single polarized antenna is one that responds only to one orientation of polarization,
either horizontal or vertical. Radio waves that are received or transmitted by a single
polarized antenna will be either horizontal or vertical polarized. The rotation of a
single waveguide port at the customer interface, orients the polarization in the desired
direction.
20
Configuration of the proposed single-polarized UWB antenna with capacitively
coupled feed is shown in the Fig 4.1 a), b) and c).
Fig 4.1 Single Polarized Microstrip Patch UWB Antenna a) Configuration of the
antenna b) Dimensions of the entire antenna setup c) Dimensions of a Single Feed
21
Simulated design of the above structure in ANSYS HFSS simulation software is
shown below.
4.1.2 SIMULATED DESIGN IN HFSS
Fig 4.2 Simulated Single Polarized Antenna structure using HFSS.
The square radiating patch with a side length of W is supported by a Rohacell
foam of relative permittivity 𝜀 and thickness Η, and capacitively excited by two
identical feeds which are symmetrically located with respect to the center of the
antenna. Each feed consists of two portions, i.e., the vertical part is an isosceles
trapezoidal patch and the horizontal part is an isosceles triangular patch. The
horizontal and vertical patches share the same length ℓ1. The square ground plane
with a size of 60mm x 60 mm is printed on the top layer of an FR4 substrate and two
identical microstrip lines with a length of ℓ and a width of 𝒲 are on the other side.
The characteristic impedance of the microstrip line is designed to be 50Ω. A Rohacell
foam with thickness of 𝒽1 is inserted between the ground plane and the bottom side
of the capacitively coupled feed. It will have little effect after removing the foam
layer. The outer ends of the two microstrip lines are connected to the capacitively
coupled feeds by two via through via holes which are embedded in the ground plane.
Good impedance matching across a wide frequency range can be obtained by selecting
proper dimensions of the capacitively coupled feeds.
22
To understand the basic operating principle of the antenna, Figs. 4.3 (a) to (d) show
the detailed design evolution from a basic monopole to the proposed UWB antenna.
Fig 4.3 Design Evolution from the basic monopole to the UWB antenna- (a) to (d).
A basic monopole which is composed of a trapezoidal patch and a triangular
patch vertically mounted above a ground plane as shown in Fig. 4.3(a). This antenna
can operate over a wide frequency band and the height of the antenna is about a
quarter-wavelength at the lowest operating frequency
𝑓𝑙2(𝑑) = 𝑐
4 𝑥 (𝑠+𝐻2) (4.1)
where c is the speed of light in free space
𝑓𝑙2(𝑑) is the lowest operating frequency
s= height of the triangular patch
H2=height of the trapezoidal patch.
In order to achieve directional pattern and reduce the overall height of the
antenna, the vertical triangular patch is bent to be parallel to the ground plane, as
shown in Fig.4.3(b). This has shortened the height from 23 to 10 mm which
corresponds to a reduction of 56.5%.The final stage of the design process is to
introduce a parasitic patch to achieve good impedance matching over the UWB band,
as shown in Fig4.3(d)
23
The following formulas are employed to predict the lowest operating frequency
𝑓𝑙2(𝑑) of the patch antenna in Fig4.3(d)
𝑓𝑙2(𝑑) =𝑐
2(𝑊+2 ∆𝑊) √𝜀𝑟 (4.2)
∆𝑊 = 0.412 (𝜀𝑟+0.3)(
𝑊
𝐻𝑡 +0.264)
(𝜀𝑟−0.258)(𝑊
𝐻𝑡+0.813)
𝐻𝑡 (4.3)
Ht=H1+H2 + h1 (4.4)
The following are the parameters used in designing of the single polarized
microstrip patch antenna .
Table 4.1 Single Polarized Antenna parameters
Parameters Values
𝜀 1.03
Η 3mm
ℓ1 18mm
ℓ 12.7mm
𝒲 1.5mm
𝒽1 1mm
S 13mm
H1 10mm
fl2(d) 3.2 Ghz
24
4.2 DUAL POLARIZATION OF ANTENNAS
Many wireless service providers have adopted the usage of polarization
diversity and frequency diversity schemes in place of space diversity approach to take
advantage of the limited frequency spectra available for communication. Compact
microstrip antennas capable of dual polarized radiation are very suitable for
applications in wireless communication systems that demand frequency reuse and
polarization diversity.
A dual polarized antenna responds to both horizontally and vertically polarized
radio waves simultaneously. The use of both polarizations in this way increases the
traffic handling capacity of the system. For example, one transmitter/receiver
combination can be set on vertical polarization, while a second independent
transmitter/receiver combination can be set on horizontal polarization.
4.2.1 Polarization Diversity
Polarization diversity has become of real interest in the recent times. The main
reason for this is that this method does not require any extra bandwidth or physical
separations between the antennas. With polarization diversity, only one dual-polarized
antenna is used, However, the two polarizations must be orthogonal, for example,
horizontal/vertical. The method is based on the fact that two orthogonal polarizations
provide almost uncorrelated signals in a scattering environment.
4.2.2 Dual Polarization Techniques
A single-layer patch antenna usually operates over a limited frequency range
only which can't satisfy the bandwidth requirements for UWB applications.
Consequently, several techniques have been proposed in the literature to extend the
bandwidth of dual-polarized patch antennas. For example, one typical technique is the
use of various probe-fed mechanisms, such as printed -shaped probe, L-shaped probe,
stacked patches with capacitive-probe feed , proximity feed and aperture-coupled feed
.Alternatively, the bandwidth can be increased by embedding slots in the patch. Other
techniques include the hybrid feed technique such as L-shaped probe & aperture-
25
coupled feed, gap-coupled feed & aperture-coupled feed, and meandered strip &
aperture-coupled feed, and employing electromagnetic-fed method. Recently,
broadband dual-polarized magneto-electric dipole antennas with differential-feed have
been proposed.Hybrid feed patch antennas can achieve high isolation and low cross-
polarization while two ports may have different radiation characteristics.
4.3 DESIGN OF DUAL POLARIZED PATCH ANTENNA
A dual-polarized UWB antenna with dual orthogonal linear polarization can be
realized by adding another pair of capacitively coupled feeds. The added feeds are
also connected to two identical L-shaped microstrip lines with a length of 34.45 mm.
four identical capacitively coupled feeds are placed symmetrically with respect to the
center of the antenna and used to excite a single square radiating patch.
The four feeds are connected to four microstrip lines by vias through via holes in the
ground plane. The microstrip lines have the same width and printed on the bottom
layer of the grounded FR4 substrate as shown in Fig.4.4 In order to realize a
differential feed, two baluns are soldered to the two pair of microstrip lines
respectively, with port 1 for achieving horizontal polarization and port 2 for achieving
vertical polarization.
Differential-feed technique has been utilized in dual-polarized patch antennas
as it can enhance the port isolation and reduce cross-polarization levels.The
performance of the tapered balun has been investigated and it is found that the tapered
balun is appropriate for feeding the proposed UWB Antenna since it suffers from
sufficient insertion loss and VSWR suitable for UWB applications.
26
4.3.1 EXISTING DESIGN
Fig 4.4 Dual polarized Microstrip Patch Antenna Structure
Simulated result of the above structure in ANSYS HFSS is show below.
4.3.2 SIMULATED DESIGN USING HFSS
Fig 4.5 Simulated Design of Dual Polarized Microstrip Patch Antenna
27
The following are the design parameters used in the design of Dual Polarized
Microstrip patch Antenna.
Table 4.2 Design Parameters of Dual-Polarized Microstrip Patch Antenna
PARAMETERS VALUES
W 27mm
HI 3mm
H2 9mm
𝒽1 1mm
𝒽2 0.8mm
𝑠 6mm
ℓ1 18mm
ℓ2 7mm
ℓ 12.7mm
𝒲 = 𝒲1 1.5mm
L 15mm
𝒲2 3.1mm
28
4.4 MODIFICATIONS ON DUAL POLARIZED PATCH ANTENNA
Different shapes are tried for the Patch in the Dual-Polarized Antenna structure
such as :
1. Hexagon shape
2. Flower shape
The above two shapes are drawn using ANSYS HFSS and their results are plotted. A
comparison table is also made for the three shapes which shows the values for Return
Loss, VSWR and S-parameter. It is finally seen that the Flower shaped patch gives us
the better results. Finally a Cavity-backed structure is made for the Flower shaped
patch Dual-Polarized Antenna for the sake of improvement in the gain of the antenna.
4.4.1 PROPOSED ANTENNA GEOMETRY WITH HEXAGON SHAPE
The proposed antenna is designed using a Hexagon shaped antenna structure
with the similar dimensions to that of the flower patch antenna and their results are
plotted. The results of the hexagon shape are then compared with those got with the
flower patch antenna at the end of this paper in Table II.The proposed antenna
structure using a hexagon shape is shown below:
Fig 4.6 Simulated Design of Hexagon shape Patch Dual Polarized Microstrip Patch
Antenna
29
4.4.2 PROPOSED ANTENNA GEOMETRY WITH FLOWER PATCH
A dual polarized UWB Antenna is designed .The configuration of the dual-
polarized antenna is shown in Figure 1. The antenna structure consists of a radiating
patch of square shape supported by Rohacell foam of thickness H mm and relative
permittivity of 1.03. The patch is excited by four capacitively coupled feeds of
height H1 mm, which are connected to the four microstrip lines. The microstrip
lines are printed on the FR4 substrate of 0.8 mm thickness and permittivity
4.55.Another Rohacell foam of thickness H3 mm is inserted between the ground and
the four feeds. The four feeds are formed from a Trapezoidal shape and Triangular
shape which form a vertical patch and a horizontal patch respectively .Two baluns
are used for achieving both Horizontal Polarization in Port 1 and Vertical
Polarization in Port 2.The dimensions of the Dual-polarized antenna is shown
below:
Table 4.3 Dimensions of the proposed antenna
W H H H1 H2 H3
27mm 3mm 60mm 9mm 1mm 1mm
Fig 4.7 and 4.8 shows the Top and Side view of the proposed Dual-Polarized UWB antenna.
Fig 4.7 Simulated Design of Flower shaped Patch Dual Polarized Microstrip Patch
Antenna – Top view
30
Fig 4.8 Simulated Design of Flower shaped Patch Dual Polarized Microstrip Patch
Antenna – Side view
The internal connection of the four capacitively coupled feeds is shown in the
below diagram.
Fig 4.9 Internal connection of the four capacitively coupled feeds
H2
H1
Two feeds
interconnected
Other two feeds
interconnected
31
4.4.3 FLOWER SHAPED PATCH WITH CAVITY STRUCTURE
In order to increase the gain of the antenna , a Cavity- Backed structure is
introduced into the Flower shaped Patch Dual-Polarized UWB Antenna.The inverted
pyramid structure has a volume of Ct x Ct x Ch mm3 where Ch represents the height
of the cavity and the length of the top and bottom sides of the cavity is denoted by Ct
and Cb.The cavity backed UWB antenna has the similar dimensions as that of the
Flower shaped Patch antenna.From the Literature review ,it is seen that by increasing
the height of the antenna ,gain is increased at higher frequencies.Several values are
tried for Ct, Cb ,and Ch and it is found that the final optimized values for the needed
improvement in gain are Ct- 90mm, Cb-40mm and Ch-23mm.
A cavity structure is introduced into the flower shaped patch design and its
results were analyzed. Cavity structure is employed to increase the gain performance
of the flower shaped design. The dimension of the cavity structure is 90mm x 90mm x
23mm.Flower shaped Dual-polarized antenna along with the cavity structure is shown
below:
Fig 4.10 Simulated Design of Cavity-Backed Flower shaped Patch Dual Polarized
Microstrip Patch Antenna – Top view
32
Fig 4.11 Simulated Design of Cavity-Backed Flower shaped Patch Dual Polarized
Microstrip Patch Antenna – Side view
23 mm
33
CHAPTER-5
SIMULATION RESULTS
5.1 HFSS
ANSYS HFSS is the simulation tool used in this project.
As the reference-standard simulation tool for 3-D full-wave electromagnetic-
field simulation, HFSS is essential for designing high-frequency and/or high-speed
components used in modern electronics devices.
HFSS addresses the entire range of EM problems, including losses due to
reflection, attenuation, radiation and coupling.
The power behind HFSS lies in the mathematics of the finite element method
(FEM) and the integral, proven automatic adaptive meshing technique. This provides
a mesh that is conformal to the 3-D structure and appropriate for the electromagnetic
problem which we solve.
HFSS results yield information critical to your engineering designs. Typical
results include scattering parameters (S, Y, Z), visualization of 3-D electromagnetic
fields (transient or steady-state), transmission-path losses, reflection losses due to
impedance mismatches, parasitic coupling, and near- and far-field antenna patterns.
The following steps are followed to get a simulation for any design in HFSS:
1. Design Process
2. Solution Type
3. Parametric Model (Geometry/Materials)
a) Boundaries
b) Excitations
4. Analysis (Solution setup & Frequency setup)
a) Mesh Refinement
34
b) Check for convergence
5. Results ( 2D Report fields).
The three main parameters concerned with the antenna designed in the project are :
Gain
Return Loss
VSWR
5.2 RETURN LOSS
S-Parameters desribe the input-output relationship between ports in an
electrical system.As in my antenna design,if we have two ports ( Port 1 and Port 2)
,then S12 represents the power transferred from Port 2 to Port1 and S21 represents the
power transferred from Port 1 to Port 2.
5.2.1 SINGLE POLARIZED ANTENNA RETURN LOSS
Fig. 5.1 Single Polarized Antenna Return loss
35
5.2.2 DUAL POLARIZED ANTENNA RETURN LOSS
Fig 5.2 Dual Polarized Antenna Return loss
5.2.3 RETURN LOSS OF UWB DUAL POLARIZED ANTENNA WITH
HEXAGON SHAPED PATCH
Fig 5.3 Hexagon Patch –UWB Dual Polarized Antenna Return loss
1.00 2.00 3.00 4.00 5.00 6.00Freq [GHz]
-35.00
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
Y1
HFSSDesign1XY Plot 1 ANSOFT
m2
Curve Info
dB(S(1,1))Setup1 : Sw eep
dB(S(1,1))_1Setup1 : Sw eep
Name X Y
m2 3.2000 -10.8161
36
5.2.4 RETURN LOSS OF UWB DUAL POLARIZED ANTENNA
WITH FLOWER SHAPED PATCH
Fig 5.4 Flower shaped Patch –UWB Dual Polarized Antenna Return loss
5.3 VSWR
Voltage Standing Wave Ratio is a function of reflection coefficient which
describes the power reflected from the antenna.If the reflection coefficient is given by
,then VSWR is given by
37
5.3.1 SINGLE POLARIZED ANTENNA VSWR
Fig.5.5 Single Polarized Antenna VSWR
5.3.2 DUAL POLARIZED ANTENNA VSWR
Fig.5.6 Dual Polarized Antenna VSWR
38
5.3.3 VSWR OF UWB DUAL POLARIZED ANTENNA WITH HEXAGON
SHAPED PATCH
Fig.5.7 Hexagon patch- UWB Dual Polarized Antenna VSWR
5.3.4 VSWR OF UWB DUAL POLARIZED ANTENNA WITH FLOWER
SHAPED PATCH
Fig.5.8 Flower shaped Patch - UWB Dual Polarized Antenna VSWR
1.00 2.00 3.00 4.00 5.00 6.00Freq [GHz]
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
VS
WR
(1
)
HFSSDesign1XY Plot 2 ANSOFT
m1
Curve Info
VSWR(1)Setup1 : Sw eep
Name X Y
m1 3.2000 1.8085
39
5.4 GAIN
The term antenna gain describes how much power is transmitted in the direction of
peak radiation to that of an isotropic source.
5.4.1 SINGLE POLARIZED ANTENNA GAIN
Fig 5.9 Single Polarized Antenna Gain
40
5.4.2 DUAL POLARIZED ANTENNA GAIN
5.4.2 a) HORIZONTAL POLARIZATION
5.4.2 b) VERTICAL POLARIZATION
Fig 5.10 Dual Polarized Antenna Gain a) Horizontal polarization b) Vertical
polarization
41
5.4.3 GAIN OF UWB DUAL POLARIZED ANTENNA WITH
HEXAGON SHAPED PATCH
Fig 5.11 Hexagon patch – UWB Dual Polarized Antenna Gain
5.4.4 GAIN OF UWB DUAL POLARIZED ANTENNA WITH FLOWER
SHAPED PATCH
Fig 5.12 Flower shaped patch – UWB Dual Polarized Antenna Gain
-11.50
-8.00
-4.50
-1.00
90
60
30
0
-30
-60
-90
-120
-150
-180
150
120
HFSSDesign1Radiation Pattern 1 ANSOFT
m1
Curve Info
dB(GainTotal)Setup1 : LastAdaptiveFreq='3.1GHz' Phi='0deg'
Name Theta Ang Mag
m1 0.0000 0.0000 0.7874
42
5.4.5 CAVITY-BACKED UWB DUAL POLARIZED ANTENNA WITH
FLOWER SHAPED PATCH GAIN
Fig 5.13 Cavity-backed UWB Dual-Polarized antenna with flower shaped patch gain
5.5 3D PLOT
5.5.1 SINGLE POLARIZATION
Fig 5.14 3D Polar Plot for Single Polarized Antenna
43
5.5.2 DUAL POLARIZATION
Fig 5.15 3D Polar Plot for Dual Polarized Antenna
5.5.3 3D POLAR PLOT OF HEXAGON PATCH UWB DUAL
POLARIZED ANTENNA
Fig 5.16 3D Polar Plot for Hexagon patch UWB Dual-Polarized Antenna
44
5.5.4 3D POLAR PLOT OF FLOWER SHAPED PATCH UWB DUAL
POLARIZED ANTENNA
Fig 5.17 3D Polar Plot for Flower shaped patch UWB Dual-Polarized Antenna
45
CHAPTER -6
CONCLUSION AND FUTURE WORK
A UWB antenna with dual polarization is designed and simulated using
ANSYS HFSS simulation software and its performance was analyzed. A novel single
polarized antenna was first designed and simulated. The antenna design consists of a
radiating patch, two capacitively coupled feeds and a dielectric substrate. The
measured return loss for single polarized antenna was found to be -20dB, the
measured VSWR was found to be 1.2 and the antenna gain is found to be of
30dBm.Based on the analysis of single polarized antenna, a dual-polarized UWB
antenna with dual orthogonal linear polarization was realized. The proposed structure
of the Dual-Polarized antenna is designed with a hexagon shape and a flower shaped
patch and their results are compared to know the best among the two shapes as shown
in the table below:
Table 4.4 Comparison of Hexagon and Flower shape Patch
Design Gain Return Loss VSWR
Proposed UWB
Antenna with
Hexagon shape
0.784 dB -10.8161 1.8085
Proposed UWB
Antenna with
Hexagon shape
1.8485 dB -20.04 1.2
It is found that Flower shaped patch structure gives better results and the
structure consists of a flower shaped patch with two ports and four capacitively
coupled feeds. Antenna structure consists of a square patch, two ports and four
capacitively coupled feeds by adding another pair of capacitively coupled feed. Each
feed is formed from a vertical isosceles trapezoidal patch and a horizontal isosceles
triangular patch. Four coupled feeds are placed at the center of the antenna and excites
a square radiating patch. The feeds are connected to the microstrip lines, which are
printed on the dielectric substrate, via holes. Two tapered baluns are used to realize a
46
differential feed and excite the entire antenna structure to improve the gain and to get
high isolation between the two ports. Port 1 provides Horizontal Polarization and Port
2 provides Vertical Polarization. The return loss measured for the dual polarized
antenna is -10 dB, the measured VSWR is 2 and the measured antenna gain value is
25dBm. The return loss measured for the dual polarized antenna with the hexagon
shape is -10.7dB, the measured VSWR is 1.8 and the measured antenna gain value is
0.784dB. The return loss measured for the dual polarized antenna with the Flower
shaped patch is -20.04dB, the measured VSWR is 1.2 and the measured antenna gain
value is 1.8485dB.A Cavity structure is then introduced into the flower shaped patch
design for the sake of improvement in gain of the proposed design and the results are
analyzed. It is found that gain of 2.1989dB is got from the cavity structure.
The UWB Antenna designed here can be designed using different substrate
materials for improvement of results such as:
1. RT Duroid
2. Gallium Arsenide
The UWB Antenna designed can be connected with the UWB Receiver and the
important parameters of the receiver such as SNR, BER and bandwidth enhancement
can be estimated and be used for the real time applications.
47
REFERENCES
[1] Fuguo Zhu, Steven Gao,Anthony T.S Ho,Raed A. Abd- Alhameed,Chan
H.See,Tim W.C. Brown,Jianzhou Li,Gao Wei,Jiadong Xu , “Ultra-wideband Dual
Polarized Patch Antenna with Four Capacitively Coupled Feeds” IEEE
TRANSACTIONS ON ANTENNAS AND PROPAGATION,VOL.62,NO.5,MAY
2014.
[2] P. Li, J. Liang, and X. D. Chen, “Study of printed elliptical/circular slot
antennas for ultrawideband applications,” IEEE TRANSACTIONS ON
ANTENNAS AND PROPAGATION, VOL. 54, NO. 6, PP. 1670–1675, 2006.
[3] L. Siu, H. Wong, and K. M. Luk, “A dual-polarized magneto-electric dipole
with dielectric loading,” IEEE TRANSACTIONS ON ANTENNAS AND
PROPAGATION, VOL. 57, NO. 7, PP. 616–623, 2009.
[4] S. Gao, L. W. Li, M. S. Leong, and T. S. Yeo, “Dual-polarized slot-coupled
planar antenna with wide bandwidth,” IEEE TRANSACTIONS ON ANTENNAS
AND PROPAGATION, VOL. 51, NO. 3, PP. 441–448, 2003.
[5] [6] K. S. Ryu and A. A. Kishk, “Wideband dual-polarized microstrip patch
excited by hook shaped probe,” IEEE TRANSACTIONS ON ANTENNAS AND
PROPAGATION, VOL. 56, NO. 12, PP. 3645–3649, Dec. 2008.
[6] H. Wong, K. L. Lau, and K. M. Luk, “Design of dual-polarized L-probe patch
antenna arrays with high isolation,” IEEE TRANSACTIONS ON ANTENNAS
AND PROPAGATION, VOL. 52, NO. 1, PP. 45–52, Jan. 2004.
48
[7] K. Ghorbani and R. B. Waterhouse, “Dual polarized wide-band aperture
stacked patch antennas,” IEEE TRANSACTIONS ON ANTENNAS AND
PROPAGATION, VOL. 52, NO. 8, PP. 2171–2174, 2004.
[8] H. G. Schantz, “A brief history of UWB antennas,” IEEE A&E SYSTEMS AND
MAGAZINES, VOL. 19, NO. 4, PP. 22–26, 2004.
[9] S. G. Zhou, P. K. Tan, and T. H. Chio, “Low-profile, wideband dual-polarized
antenna with high isolation and low cross polarization,” IEEE ANTENNAS AND
WIRELESS PROPAGATION LETTERS., VOL. 11, PP. 1032–1035, 2012.
[10] J. J. Xie, Y. Z. Yin, J. H. Wang, and X. L. Liu, “Wideband dual-polarized
electromagnetic-fed patch antenna with high isolation and low cross-
polarisation,” IEEE ELECTRONIC LETTERS, VOL. 49, NO. 3, PP. 171–173,
2013.
49
LIST OF PUBLICATIONS
Conferences
Presented a paper titled “Flower shaped UWB Microstrip Patch antenna with
Cavity” in International conference on Communication and Security (ICCS
2016) on 17, 18 and 19th March 2016 at Pondicherry Engineering College,
Pondicherry.
Presented a paper titled “UWB Microstrip Patch Antenna with Flower shaped
Patch and Cavity Structure” in IEEE International Conference on Wireless
Communications, Signal Processing and Networking (WiSPNET 2016) on
23,24th and 25th March 2016 at SSN College of Engineering, Chennai,
Tamilnadu.