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

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ANTENNAS AND PROPAGATION, VOL. 54, NO. 6, PP. 1670–1675, 2006.

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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

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AND PROPAGATION, VOL. 51, NO. 3, PP. 441–448, 2003.

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48

[7] K. Ghorbani and R. B. Waterhouse, “Dual polarized wide-band aperture

stacked patch antennas,” IEEE TRANSACTIONS ON ANTENNAS AND

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[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

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[10] J. J. Xie, Y. Z. Yin, J. H. Wang, and X. L. Liu, “Wideband dual-polarized

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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.