The WLAN Band-Notching of Ultra WideBand Antennas

TABLE OF CONTENTS

List of Figures

List of Tables

Abstract

Chapter 1 Introduction
1.1 Overview
1.2 Problem Statement
1.3 Objective
1.4 Methodology
1.5 Compilation of Book

Chapter 2 Ultra WideBand Technology
2.1 Introduction to Antennae
2.2 Parameters of Antennae
2.3 Types of Antennae
2.3.1 Wire Antenna
2.3.2 Aperture Antenna
2.3.3 Array Antenna
2.3.4 Lens Antenna
2.3.5 Reflector Antenna
2.3.6 Microstrip Patch Antenna
2.4 Principles of UWB Technology
2.4.1 General Overview
2.4.2 Introduction to Ultra Wideband Antennae
2.4.3 Working of UWB Technology
2.4.4 Advantages of Ultra WideBand Technology
2.4.5 Disadvantages of Ultra WideBand Technology
2.5 Existing UWB Antennae with Band Notch Designs

Chapter 3 Co-Planar Waveguide-Fed UWB Antenna with 5GHz WLAN Band Notch Characteristics
3.1 Introduction
3.2 Design of the Proposed CPW-Fed Antenna
3.2.1 Ultra WideBand (Without U-Shape Slot)
3.2.2 Ultra WideBand Antenna with WLAN Notch
3.3 Simulated Results of the Proposed Antenna
3.3.1 VSWR with WLAN Notch
3.3.2 Return Loss with WLAN Notch
3.3.3 Radiation Patterns
3.3.4 Current Distribution
3.3.5 Gain vs. Frequency Plot
3.4 Measured Results of the Proposed Antenna

Chapter 4 Transmission Line-Fed UWB Antenna with 5GHz WLAN Band Notch using Partial Ground Plane
4.1 Introduction
4.2 Design of the Proposed TX Line-Fed Antenna with Partial Ground Plane
4.2.1 Ultra WideBand without U-Shape Slot
4.2.2 Ultra WideBand with WLAN Notch
4.3 Simulated Results of the Proposed Antenna
4.3.1 VSWR with WLAN Notch
4.3.2 Return Loss with WLAN Notch
4.3.3 Radiation Patterns
4.3.4 Current Distribution
4.3.5 Gain vs. Frequency Plot
4.4 Measured Results of the Proposed Antenna

Chapter 5 Transmission Line-Fed Slotted Ground Plane UWB Antenna with 4.9GHz and 5GHz WLAN Band Notch Characteristics
5.1 Introduction
5.2 Design of the Proposed TX Line-Fed Antenna with Slotted Ground Plane
5.2.1 Ultra WideBand (Without U-Shape Slot)
5.2.2 Ultra WideBand With WLAN Notch
5.3 Simulated Results of the Proposed Antenna
5.3.1 VSWR with WLAN Notch
5.3.2 Return Loss with WLAN Notch
5.3.3 Radiation Patterns
5.3.4 Current Distribution
5.3.5 Gain vs. Frequency Plot
5.4 Measured Results of the Proposed Antenna

Chapter 6 UWB Applications
6.1 Introduction
6.2 UWB in Communications and Sensors
6.2.1 Low Data Rate
6.2.2 High Data Rate
6.2.3 Home Network Appliances
6.3 UWB Technology in WBAN
6.4 Position Location and Tracking
6.5 Radars

Chapter 7 Conclusion and Future Work
7.1 Conclusion
7.2 Future Work

Appendix A Antenna Parameters

Appendix B Microstrip Patch Antenna

Appendix C Techniques to Design Antenna

Bibliography

Acknowledgement

First praise is to Allah, the Almighty, on whom ultimately we depend for sustenance and guidance. It would not have been possible to write this thesis without the help and support of the kind people around me, to only some of whom it is possible to give particular mention here

This thesis would not have been possible without the help, support and patience of my supervisor, Sir Syed Muzahir Abbas. His vast experience and deep understanding of the subject proved to be immense help to me, and also his profound view-points and extraordinary motivation enlightened me in many ways. I just hope my thinking and working attitude has been shaped according to such outstanding qualities

I am indebted to Sir Laeeq Riaz’s support and guidance throughout the completion of this project, not to mention his advice and unsurpassed knowledge about Radio Frequencies and Antenna Design

The good advice, support and friendship of Sir Zeeshan Qamar has been invaluable on both an academic and personal level for which I am extremely grateful. I intend to show gratitude to Dr. Hans G. Schantz, Chief Scientist, Q-Track Corporation United States of America, for his help regarding the antenna designs and pin-pointing the simulation errors that I came across every time I found myself stuck in the task

I would like to acknowledge the academic and technical support of COMSATS Institute of Information Technology (CIIT), Islamabad and its staff who provided necessary support for this research. The library facilities, laboratory facilities and the computer facilities of the University have been indispensable

I would like to thank my family who has given their unequivocal support throughout, as always, for which my mere expression of thanks likewise does not suffice. Last but not the least I am indebted to the support we received from my dear friends especially Ms. Gul Perwasha without whom this project could not have reached the completion stage

Zeeshan Ahmed

List of Figures

Figure 2.1 A helix antenna [28]

Figure 2.2 A typical horn antenna [29]

Figure 2.3 YagiUda Array antenna [30]

Figure 2.4 A lens antenna [31]

Figure 2.5 A corner reflector antenna [32]

Figure 2.6 Microstrip patch antenna [33]

Figure 2.7 UWB Spectrum [34]

Figure 2.8 Narrow band and wideband signals

Figure 2.9 Working of UWB [38]

Figure 2.10 (a) UWB and old wireless technology (b) magnitude vs. time graph [38]

Figure 2.11 Design of the antenna

Figure 2.12 VSWR vs. frequency graph

Figure 2.13 VSWR at varied lengths

Figure 2.14 measured and simulated VSWR

Figure 2.15 Design of antenna

Figure 2.16 VSWR of the proposed antenna

Figure 2.17 Gain of proposed antenna

Figure 2.18 (a) Top view (b) side view

Figure 2.19 Return Loss of antenna

Figure 2.20 Return Loss of antenna

Figure 2.21 simulated and measured return loss

Figure 2.22 Design of antenna (a) front view (b) back view

Figure 2.23 VSWR at varied lengths

Figure 2.24 VSWR w.r.t side shifts

Figure 2.25 VSWR at varied widths

Figure 2.26 VSWR w.r.t down shifts

Figure 2.27 Dual band notch design

Figure 2.28 VSWR measured vs. simulated graph

Figure 2.29 Antenna Design (a) front (b) back view

Figure 2.30 Gain of proposed design

Figure 3.1 Layout of the antenna Stage 1

Figure 3.2 VSWR vs. Frequency at Stage 1

Figure 3.3 Layout of the antenna Stage 2

Figure 3.4 VSWR vs. Frequency at Stage 2

Figure 3.5 Layout of the antenna Stage 3

Figure 3.6 VSWR vs. Frequency at Stage 3

Figure 3.7 Layout of the antenna Stage 4

Figure 3.8 VSWR vs. Frequency at Stage 4

Figure 3.9 Layout of the antenna Stage 5

Figure 3.10 VSWR vs. Frequency at Stage 5

Figure 3.11 Layout of the antenna Stage 6

Figure 3.12 VSWR vs. Frequency at Stage 6

Figure 3.13 Layout of the antenna Stage 7

Figure 3.14 VSWR vs. Frequency at Stage 7

Figure 3.15 Layout of the antenna Stage 8

Figure 3.16 VSWR vs. Frequency at Stage 8

Figure 3.17 Layout of the antenna Stage 9

Figure 3.18 VSWR vs. Frequency at Stage 9

Figure 3.19 VSWR vs. Frequency at Stage 10

Figure 3.20 VSWR vs. Frequency graph varying ‘d’

Figure 3.21 VSWR vs. Frequency graph varying ‘g’

Figure 3.22 Proposed UWB antenna with band-notch slot

Figure 3.23 VSWR vs. Frequency graph varying Ln

Figure 3.24 VSWR vs. Frequency graph varying Wn

Figure 3.25 Simulated VSWR vs. Frequency graph of the proposed antenna with U-shape slot

Figure 3.26 Simulated Return Loss vs. Frequency graph of the proposed antenna with U-shape slot

Figure 3.27 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.0GHz

Figure 3.28 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.5GHz

Figure 3.29 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 4.0GHz

Figure 3.30 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5.0GHz

Figure 3.31 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5.5GHz

Figure 3.32 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 6.0GHz

Figure 3.33 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 7.0GHz

Figure 3.34 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 8.0GHz

Figure 3.35 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 9.0GHz

Figure 3.36 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.0GHz

Figure 3.37 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.5GHz

Figure 3.38 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 4.0GHz

Figure 3.39 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.0GHz

Figure 3.40 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.5GHz

Figure 3.41 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 6.0GHz

Figure 3.42 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 7.0GHz

Figure 3.43 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 8.0GHz

Figure 3.44 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 9.0GHz

Figure 3.45 3D plot of Radiation pattern for 3.5GHz

Figure 3.46 3D plot of Radiation pattern for 5.0GHz

Figure 3.47 3D plot of Radiation pattern for 5.5GHz

Figure 3.48 3D plot of Radiation pattern for 6.0GHz

Figure 3.49 3D plot of Radiation pattern for 7.0GHz

Figure 3.50 3D plot of Radiation pattern for 8.0GHz

Figure 3.51 Simulated Current Distribution at (a) 4GHz (b) 5.5GHz (c) 7.5GHz (d) 10GHz

Figure 3.52 Gain of the proposed antenna with and without band-notch characteristic

Figure 3.53 Prototype of the Proposed Antenna

Figure 3.54 Measured VSWR vs. Frequency plot of the proposed antenna with U-shape slot

Figure 4.1 Layout of the antenna Stage 1 (a) Front side (b) Back side

Figure 4.2 VSWR vs. Frequency at Stage 1

Figure 4.3 Layout of the antenna Stage 2 (a) Front side (b) Back Side

Figure 4.4 VSWR vs. Frequency at Stage 2

Figure 4.5 Layout of the antenna Stage 3 (a) Front side (b) Back side

Figure 4.6 VSWR vs. Frequency at Stage 3

Figure 4.7 Layout of the antenna Stage 4 (a) Front side (b) Back side

Figure 4.8 VSWR vs. Frequency at Stage 4

Figure 4.9 Layout of the antenna Stage 5 (a) Front side (b) Back side

Figure 4.10 VSWR vs. Frequency at Stage 5

Figure 4.11 Layout of the antenna Stage 6 (a) Front side (b) Back side

Figure 4.12 VSWR vs. Frequency at Stage 6

Figure 4.13 Layout of the antenna Stage 7 (a) Front side (b) Back side

Figure 4.14 VSWR vs. Frequency at Stage 7

Figure 4.15 Layout of the antenna Stage 8 (a) Front side (b) Back side

Figure 4.16 VSWR vs. Frequency at Stage 8

Figure 4.17 Layout of the antenna Stage 9 (a) Front side (b) Back side

Figure 4.18 VSWR vs. Frequency at Stage 9

Figure 4.19 VSWR vs. Frequency at Stage 10

Figure 4.20 VSWR vs. Frequency graph varying ‘Lg’

Figure 4.21 Proposed TX Line-fed UWB antenna with band-notch slot and DGS (a) Front side (b) Back side

Figure 4.22 VSWR vs. Frequency graph of TX Line-fed UWB antenna with WLAN band notch feature varying ‘Lu’

Figure 4.23 VSWR vs. Frequency graph of TX Line-fed UWB antenna with WLAN band notch feature varying ‘Wu’

Figure 4.24 VSWR vs. Frequency graph of TX Line-fed UWB antenna with WLAN band notch feature with and without using DGS

Figure 4.25 VSWR vs. Frequency graph of TX Line-fed UWB antenna with WLAN band notch

Figure 4.26 Return Loss vs. Frequency graph of TX Line-fed UWB antenna with band notch

Figure 4.27 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.0GHz

Figure 4.28 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.5GHz

Figure 4.29 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 4.0GHz

Figure 4.30 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5GHz

Figure 4.31 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5.5GHz

Figure 4.32 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 6GHz

Figure 4.33 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 7GHz

Figure 4.34 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 8GHz

Figure 4.35 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 10GHz

Figure 4.36 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.0GHz

Figure 4.37 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.5GHz

Figure 4.38 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 4.0GHz

Figure 4.39 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.0GHz

Figure 4.40 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.5GHz

Figure 4.41 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 6.0GHz

Figure 4.42 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 7.0GHz

Figure 4.43 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 8.0GHz

Figure 4.44 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 10.0GHz

Figure 4.45 3D plot of Radiation pattern for 3.5GHz

Figure 4.46 3D plot of Radiation pattern for 5.0GHz

Figure 4.47 3D plot of Radiation pattern for 5.5GHz

Figure 4.48 3D plot of Radiation pattern for 6.0GHz

Figure 4.49 3D plot of Radiation pattern for 7.0GHz

Figure 4.50 3D plot of Radiation pattern for 8.0GHz

Figure 4.51 Simulated Current Distribution at (a) 4GHz (b) 5.5GHz (c) 7.5GHz (d) 10GHz

Figure 4.52 Gain of the proposed antenna with and without band-notch characteristic

Figure 4.53 Prototype of the Proposed Antenna

Figure 4.54 Measured VSWR vs. Frequency plot of the proposed antenna with U-shape slot

Figure 5.1 Layout of the antenna Stage 1 (a) Front side (b) Back side

Figure 5.2 VSWR vs. Frequency at Stage 1

Figure 5.3 Layout of the antenna Stage 2 (a) Front side (b) Back side

Figure 5.4 VSWR vs. Frequency at Stage 2

Figure 5.5 Layout of the antenna Stage 3 (a) Front side (b) Back side

Figure 5.6 VSWR vs. Frequency at Stage 3

Figure 5.7 Layout of the antenna Stage 4 (a) Front side (b) Back side

Figure 5.8 VSWR vs. Frequency at Stage 4

Figure 5.9 Layout of the antenna Stage 5 (a) Front side (b) Back side

Figure 5.10 VSWR vs. Frequency at Stage 5

Figure 5.11 Layout of the antenna Stage 6 (a) Front side (b) Back side

Figure 5.12 VSWR vs. Frequency at Stage 6

Figure 5.13 Layout of the antenna Stage 7 (a) Front side (b) Back side

Figure 5.14 VSWR vs. Frequency at Stage 7

Figure 5.15 Layout of the antenna Stage 8 (a) Front side (b) Back side

Figure 5.16 VSWR vs. Frequency at Stage 8

Figure 5.17 Layout of the antenna Stage 9 (a) Front side (b) Back side

Figure 5.18 VSWR vs. Frequency at Stage 9

Figure 5.19 VSWR vs. Frequency graph varying ‘Lg’

Figure 5.20 VSWR vs. Frequency graph varying ‘Ws’

Figure 5.21 Proposed UWB antenna with band-notch slot (a) Front view (b) Back view

Figure 5.22 VSWR vs. Frequency graph varying Ln

Figure 5.23 VSWR vs. Frequency graph varying Wn

Figure 5.24 Simulated VSWR vs. Frequency graph of the proposed antenna with U-shape slot

Figure 5.25 Simulated Return Loss vs. Frequency graph of the proposed antenna with U-shape slot

Figure 5.26 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.0GHz

Figure 5.27 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.5GHz

Figure 5.28 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 4.0GHz

Figure 5.29 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5GHz

Figure 5.30 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5.5GHz

Figure 5.31 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 6GHz

Figure 5.32 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 7.0GHz

Figure 5.33 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 8.0GHz

Figure 5.34 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 10.0GHz

Figure 5.35 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.0GHz

Figure 5.36 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.5GHz

Figure 5.37 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 4.0GHz

Figure 5.38 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.0GHz

Figure 5.39 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.5GHz

Figure 5.40 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 6.0GHz

Figure 5.41 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 7.0GHz

Figure 5.42 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 8.0GHz

Figure 5.43 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at10.0GHz

Figure 5.44 3D plot of Radiation pattern for 3.5GHz

Figure 5.45 3D plot of Radiation pattern for 5.0GHz

Figure 5.46 3D plot of Radiation pattern for 5.5GHz

Figure 5.47 3D plot of Radiation pattern for 6.0GHz

Figure 5.48 3D plot of Radiation pattern for 7.0GHz

Figure 5.49 3D plot of Radiation pattern for 8.0GHz

Figure 5.50 Simulated Current Distribution at (a) 4GHz (b) 5.5GHz (c) 7.5GHz (d) 10GHz

Figure 5.51 Gain of the proposed antenna with and without band-notch characteristic

Figure 5.52 Prototype of the Proposed Antenna (a) Front view (b) Back view

Figure 5.53 Measured VSWR vs. Frequency plot of the proposed antenna with U-shape slot

Figure A.1 Beamwidth [35]

Figure A.2 Half power beamwidth [36]

Figure A.3 (a) 3d and (b) 2D radiation pattern

Figure A.4 Radiation pattern of an antenna showing main, back and side lobes [37]

Figure A.5 Return Loss graph

Figure A.6 Radiation Mechanism

Figure B.1 Micro Strip Patch Antenna

Figure B.2 Microstrip line feed [39]

Figure B.3 Quarter wavelength T.L feed [40]

Figure B.4 Probe Feed [40]

Figure B.5 Coupled Feed [40]

Figure B.6 Aperture Feed [40]

LIST OF TABLES

Table 3.1 Design Parameters of the proposed antenna

Table 3.2 Computed Parameters before and after implementing band-notch

Table 4.1 Design Parameters of the proposed antenna

Table 4.2 Computed Parameters of the proposed antenna

Table 5.1 Design Parameters of the proposed antenna

Table 5.2 Computed Parameters before and after implementing band-notch

Table 7.1 Comparison between proposed and existing antennae

Abstract

Since the commencement of human civilization, humankind attempts to communicate with each other. It is the process of communication, namely the sharing of information, emotions and feelings that has made the mankind the sterling creation of God. It all started with gestures of hands and sounds produced by the vocal cords and gradually evolved into wired and wireless communication now

The orthodox wireless systems were long-range narrowband systems, but in order to use the available spectrum, now, UWB (Ultra-Wideband) short-range systems are being used which consume low power and built using low-priced digital components. The Microstrip Antennae are designed to implement UWB systems, because they show effective results for broadband antennae. Ultra-wideband (UWB) antennae are by far the most essential elements for UWB systems. With the launch of the 3.1GHz to 10.6GHz band, applications for short-range and high-bandwidth portable gadgets are major research areas in UWB systems. Consequently, the acknowledgment of UWB antennas in printed-circuit systems within comparatively small substrate areas is of major significance.

In this report three staircase UWB antennae with WLAN band notch characteristic, each having different ground planes, are presented. These include a Co-Planar Waveguide-fed antenna, a Transmission Line-fed antenna with partial ground plane having a Defected Ground Structure (DGS) and a Transmission Line-fed antenna with slotted ground plane. All the band-notched antennae have rejection characteristics at 5 GHz WLAN band (5.15GHz to 5.35GHz and 5.725GHz to 5.825 GHz) while the antenna with slotted ground plane rejects the 4.9GHZ WLAN band (4.94GHz to 4.99GHz) as well. In all the three antennae the WLAN band is notched by embedding a U-shaped slot in the transmission line.

The proposed antennae are carefully designed, simulated and tested in order to fulfill the UWB antennae’s pre-defined criteria. The Simulated and Measured results are found to be in good agreement which show the validity of the suggested designs.

Chapter 1 Introduction

The following chapter describes the significance of the undertaken project i.e. to design UWB antennae with Wireless Local Area Network (WLAN) band notch characteristic. This chapter also describes the objectives of proposed antennae along with the methodology adopted to obtain required results.

1.1 Overview

According to IEEE “antenna is a device for radiating and receiving electromagnetic waves”. Now a day wireless communication has significant importance and antenna is one of the most important and best means of wireless communication. Small size and compact antenna with high gain and accuracy is the present day demand. There are many types of antenna, but micro strip patch antennas are most popular and common among all types because they are small in size and have low profile and, top of all, easy to fabricate. Along with the advantages there are some disadvantages of micro strip patch antennas like they have narrow bandwidth but at the present time several techniques and methods are introduced to enhance bandwidth.

Ultra Wideband antennas have many applications. Some of them include satellite communication, radar imaging. Ultra wide band antennas have broad spectrum and are for unlicensed applications.

1.2 Problem Statement

Ultra Wideband technology is used for broad spectrum, less power and short range communication. UWB transmits in such a way that it does not interfere with conventional narrowband and carrier wave used in same frequency band. In 2002, for UWB applications FCC allocated free license band from 3.1GHz to 10.6GHz, since then demand of UWB antennas is increasing day by day for high data rate applications.

In antenna design UWB has had a significant role. In Ultra wide band antenna design the most important and challenging step is to achieve wide bandwidth with high gain and radiation efficiency which is difficult to achieve on microstrip patch antenna yet there are techniques which can be applied in order to obtain desired outcome.

1.3 Objective

In this project, Ultra Wideband antennae using co-planar waveguide, transmission line-fed with partial ground and transmission line-fed with slotted ground plane are proposed. The project includes the design of the antennae with their simulated and fabricated results.

- To propose and design antennae for ultra wide band applications.
- Antennae should cover UWB range from 3.1 to 10.6GHz.
- The size of the antennae should be small; it will make them suitable for applications which demand miniaturized antenna structure.
- For bandwidth enhancement staircase scheme is adopted.
- 4.9GHz and 5GHz frequency bands should be notched in order to avoid interference with WLAN systems.

1.4 Methodology

In order to get CPW-fed and Transmission Line-fed antennae suitable for UWB applications, firstly, the required UWB range (3.1GHz to 10.6GHz) is achieved by using staircase design. Results show that there is increase in bandwidth by addition of each area step. In order to avoid interference with other frequency bands, the WLAN band is notched from 5GHz to 6GHz in CPW-fed and transmission line-fed partial ground plane antennae whereas the slotted ground plane notches the 4.9GHz frequency band as well. Notch is obtained by embedding U-shaped slot in feed line whereas Defected Ground Structure (DGS) in the Transmission Line-fed partial ground plane enhances the band notch characteristics of the antenna.

1.5 Compilation of Book

The book is divided into 7 parts:

Chapter 2 includes introduction to UWB technology (its principles and working), introduction to antennae, its types and fundamental parameters like radiation pattern, gain, directivity etc. and in the end a literature review on existing UWB antennae.

Chapter 3 presents designing technique and simulated and measured results of the proposed CPW-fed staircase antenna. The results include 2D and 3D radiation patterns for different frequencies, VSWR, current distribution and gain plots.

Chapter 4 presents designing technique and simulated and measured results of the proposed Transmission Line-fed staircase antenna with Defected Ground Structure in partial Ground Plane. The results include 2D and 3D radiation patterns for different frequencies, VSWR, current distribution and gain plots.

Chapter 5 presents designing technique and simulated and measured results of the proposed Transmission Line-fed staircase antenna with Slotted Ground Plane. The results include 2D and 3D radiation patterns for different frequencies, VSWR, current distribution and gain plots.

Chapter 6 describes the practical uses and applications of the proposed CPW fed Ultra Wideband antenna.

Chapter 7 concludes the project work and helps to explore the subject in future.

Chapter 2 Ultra WideBand Technology

Zeeshan Ahmed, Gul Perwasha

This chapter starts with defining antenna and its parameters. It also includes the history and working of Ultra WideBand (UWB) antennae along with the literature survey of the existing antennae. Antenna parameters are discussed in detail in the Appendix A of the report.

2.1 Introduction to Antennae

Antennae are usually metallic device (as a rod or wire) for radiating or receiving radio waves. According to IEEE, an antenna is defined as “the part of a transmitting or receiving system that is designed to radiate or receive device electromagnetic waves” [2]. An antenna is said to be a device used for transmitting and receiving radio wave signals through a certain medium.

2.2 Parameters of Antennae

While designing the antenna, its overall performance relies upon numerous parameters which are necessary to realize. An antenna is dependent on various parameters which are as follows:

- Beam width
- Radiation resistance
- Bandwidth
- Radiation pattern
- Return loss
- Gain
- Directivity
- Q-factor
- Voltage standing wave ratio (VSWR)
- Efficiency

Details of antenna parameters are described in Appendix A.

2.3 Types of Antennae

Based on the size, construction and the operating frequency, antennae can be classified into several types. Following are the types of antennae:

- Wire antenna
- Aperture antenna
- Array antenna
- Reflector antenna
- Lens antenna
- Micro-strip patch antenna

2.3.1 Wire Antenna

Wire antenna can be categorized as straight wire (monopoles and dipoles), loop wire (circular, sphere, rectangular, ellipse) and helix antenna. These are used in automobiles, buildings, ships, aircrafts, spacecrafts etc. In the situations where there are low frequencies, wire antenna suits best [1].

illustration not visible in this excerpt

Figure 2.1 A helix antenna [28]

2.3.2 Aperture Antenna

The aperture antenna has an aperture through which electromagnetic waves are transmitted and received. Aperture antennae can be categorized as waveguide (rectangular) and horn (conical, pyramidal). These antennae have high frequency and can be made prone to environmental issues by covering with a dielectric. Aperture antennae are found in aircraft applications usually.

illustration not visible in this excerpt

Figure 2.2 A typical horn antenna [29]

2.3.3 Array Antenna

Array antenna is the placement of radiating elements in such a way that these elements give maximum radiation in desired direction when added up and minimum in the other receiver. There are several types of array antennae such as Yagi-Uda Array, Aperture Array and Slotted microstrip array [1].

illustration not visible in this excerpt

Figure 2.3 YagiUda Array antenna [30]

2.3.4 Lens Antenna

Lenses chiefly serve the purpose of adjusting the line of sight of incident divergent energy to avoid it from dispersing in unwanted directions which tend to lead to unwanted results. This antenna uses a microwave lens, which is identical to an optical lens to align the spherical wave fronts. Lens antennae are deemed according to their material from, which they are categorized, or their geometrical form.

illustration not visible in this excerpt

Figure 2.4 A lens antenna [31]

2.3.5 Reflector Antenna

These antennae serve the purpose of long communication. They are high frequency operated antennae. Blockage is produced by the antenna feeding in the antenna field of view that causes efficiency losses due to light shrinking. As a result of shadowing, diffraction lobes are produced in the antenna pattern [8]. Reflector antennae include parabolic reflector and corner reflector.

illustration not visible in this excerpt

Figure 2.5 A corner reflector antenna [32]

2.3.6 Microstrip Patch Antenna

Microstrip patch antenna is composed of metallic patch on a substrate that is grounded. The patch of the microstrip may have numerous geometric shapes (rectangular, circular,square, ellipse). They are light weight, easy to fabricate and are economical [1].

illustration not visible in this excerpt

Figure 2.6 Microstrip patch antenna [33]

Details of microstrip patch antenna are discussed in Appendix B.

2.4 Principles of UWB Technology

2.4.1 General Overview

Taking into account the term "Ultra WideBand" (UWB) as a comparatively new term to illustrate an innovative technology, which was brought into consideration in the early 1960’s. It was referred to as an "impulse", “carrier-free”, or "base-band" technology in the orthodox description. Like a short pulse, the main idea is to generate, transmit and receive a very brief duration impulse of radio frequency (RF) energy. The pulse generally lasts a few tens of picoseconds to some nanoseconds. These pulses depict one to only a few cycles of an RF carrier wave; therefore, as for resultant waveforms, highly broadband signals can be obtained. Generally, it is challenging to figure out the real RF center frequency for a very short pulse; therefore, the phrase "carrier-free" arrives [9]. A few milliwatts is the total of the power delivered, which usually generates very low spectral power densities when coupled with the spectral spread. The Federal Communication Commission (FCC) bounds that the emission limits should not be greater than -41.3 dBm/MHz or 75 nW/MHz between 3.1GHz and 10.6 GHz. The total power in this range is only 0.5 mW. These spectral power densities settle well underneath a receiver noise level [10]. Standard UWB signals are presented which include major frequency spectra [11].

2.4.2 Introduction to Ultra Wideband Antennae

An antenna is a device that can also be deemed as an impedance transformer in between an input impedance and free space. A conventional radio broadcast antenna for amplitude modulation (AM) can be viewed as UWB antenna. The fractional bandwidth of an AM broadcast antenna is about 100 percent as it handles a frequency range of 535kHz to 1705kHz. On the contrary, the AM receivers are built and tuned in such a way that they receive distinctive narrowband channels of 10kHz bandwidth. This is because of the modulation scheme. Consequently, the fractional bandwidth is only 0.6 to 1.9 percent [12]. It is this fractional bandwidth over which the antenna has to operate in amplitude coherence.

Conventionally, UWB antennae operate, generally, in a multi-narrowband scheme. Nevertheless, the modern UWB antennae must be capable enough to transmit and receive a single coherent signal that handles the whole operating bandwidth. Furthermore, a UWB antenna is expected to receive or transmit all desired frequencies in the same time. As a result, across the operating bandwidth, the radiation patterns and impedance matching should be unvaried [12].

Ideally, a UWB antenna has zero dispersion and a fixed phase center. In actual UWB antennae, finite dispersion can be compensated only if the waveform is foreseeable. Log-periodic antenna can be counted among the examples of a dispersive antenna. The log-periodic antenna employs its small-scale parts to radiate the high frequency range whilst its large-scale parts are dedicated to radiate low frequencies. This antenna produces a dispersive signal. In addition, numerous waveforms will be produced beside different azimuth angles.

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Figure 2.7 UWB Spectrum [34]

Ultra wideband antennae can be brought into use for Indoor environment applications having short-range communications for high data rates or Outdoor environment applications which have long-range communications but for very low data rates.

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Figure 2.8 Narrow band and wideband signals

2.4.3 Working of UWB Technology

The UWB technology sends small digital pulses which are of very short duration (intervals of 10 pico-seconds) through a large number of frequency channels simultaneously.

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Figure 2.9 Working of UWB [38]

There are numerous ways in which the signal used in UWB can be generated. One of them could be through using the sources of narrowband pulses and letting them through from a bandpass filter. This is one of the orthodox methods. Figure 2.10 (a) shows the relationship between the modern concepts of UWB and the roots of first wireless communications though it does not show the full working of the UWB system.

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Figure 2.10 (a) UWB and old wireless technology (b) magnitude vs. time graph [38]

2.4.4 Advantages of Ultra WideBand Technology

Ultra wideband has emerged as a very promising technology with numerous features. Some of them are listed as follows:

- Due to their short time pulse span, UWB waveforms have relatively large bandwidths. For instance, fairly high data rate performance can be offered by UWB pulses in communications in multi-user network applications. Even for applications related to radars, very good range resolution and accurate distance and placement measurement abilities can be attained by the same pulses [9].
- Short span waveforms have comparatively fine immunity to multi-path cancellation effects as noticed in handheld cell phones and indoor environments. Multi-path cancellation effect happens when a high power reflected wave eliminates the direct path signal. Usually the reflected wave turns up out of phase when compared with the direct path signal. As a result, the receiver receives a reduced amplitude response. In the UWB signal, no cancellation occurs due to its very short pulse feature. This is because the direct path passes before the reflected signal turns up. For that reason the handheld wireless devices are, specifically, best suited for UWB technology to put into action [9].
- Very short pulse duration, in the time domain, is equivalent to very large bandwidth in the frequency. Energy density, due to the large bandwidth, can be quite low. This low energy density can be converted into even low probability of detection (LPD) RF signature. This LPD signature is of use in several military applications like covert communication and radars etc. Furthermore, minimal interference to proximity systems as well as minimal RF health hazards are produced by LPD signature. Due to its low energy density and pseudo-random (PR) characteristics of transmitted signal, UWB signal is noise-like. Consequently, this feature enables the UWB system to refrain from interference to existing radio systems. As said earlier, these characteristics are of high importance to, both, military as well as commercial applications [9][13].
- Low design complexity and low cost are the best features of the UWB systems. These advantages come up from the baseband nature of the signal transmission. Short time domain pulses are capable of propagating even without needing an extra RF mixing process when compared with traditional radio systems. This leads to the less complex nature of the design structure. Additionally, UWB systems can be made very close to “all-digital” with minimal RF or microwave electronics leading to minimum cost of the system [9][14].

2.4.5 Disadvantages of Ultra WideBand Technology

Engineering is all about tradeoffs. No single technology exists in this universe which, alone, is good for everything. Likewise, UWB has numerous advantages but still it is, unfortunately, among those technologies which have certain disadvantages too. The disadvantages are listed as under:

- Interference with GPS (Global Positioning satellite) is one the disadvantages observed with the UWB technology. GPS, at the moment, have more than 10 million users and its basic applications are used for public safety such as aircraft flight and approach guidance etc. UWB brings up a problem to GPS since their frequencies overlap and GPS signal is highly sensitive to interference.
- The output power of the UWB systems is limited due to its overlapping frequency bandwidth with other radio systems. Usually the power cannot be transmitted for above one kilometer range with high gain antenna and for the regular antenna, the limit decreases to ten to twenty meters.
- As UWB is relatively a new technology, therefore, setting up the UWB systems worldwide would disturb the economic balances of the regions. Moreover, the existing cable setups will be counted among obsolete equipment and the investors will have to invest a relatively huge sum to deploy the new technology.

2.5 Existing UWB Antennae with Band Notch Designs

2.5.1 Compact Printed Ultra WideBand Monopole Antenna with Dual Band Notch Characteristic [15]

- A microstrip fed planar UWB antenna with compact size of 35×14mm2, having dual band notch characteristics is proposed.
- The bands are notched by embedding an E-slot in radiation patch and U-slot in feeding line. By adjusting the corresponding slot both the notched bands can be controlled.
- The result shows that the proposed antenna has two band stop filters at 3.49GHz–4.12GHz and 5.66GHz–6.43GHz, respectively. Furthermore, two sharp decrements are observed in gain plot which clearly shows the presence of band stop filters.

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Figure 2.11 Design of the antenna

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Figure 2.12 VSWR vs. frequency graph

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Figure 2.13 VSWR at varied lengths

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Figure 2.14 measured and simulated VSWR

2.5.2 Bandwidth Enhancement of a Wide Slot UWB Antenna with Notch Band Characteristics

- A CPW-fed monopole antenna of size 28x21x1.6mm3 is presented with dual band notch characteristics to avoid interference in UWB frequency range.
- The wide bandwidth is achieved by embedding L-shaped slots in CPW ground and by etching rectangular slot band stop filter is obtained.
- Radiation pattern of the proposed antenna is omni-directional in H-plane and quasi omni-directional in E-plane.
- The notch characteristics are obtained at 5GHz-6GHz for HIPERLAN/2 and IEEE 802.11 a (5.1 GHz-5.9GHz) and C-band (4.4GHz-5.0GHz).
- The result of the presented antenna shows that the antenna not only has dual band notch characteristics but also has good radiation pattern and wide bandwidth.

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Figure 2.15 Design of antenna

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Figure 2.17 Gain of proposed antenna

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Figure 2.16 VSWR of the proposed antenna

2.5.3 Band Notch Characteristics Using Ground Stubs For Compact UWB Antenna [16]

- A planar monopole UWB antenna is designed by using pair of ground stubs to achieve single notch band characteristics.
- The proposed antenna has wide bandwidth from 2.7GHz to 12GHz with respect to the return loss which is less than -10 dB.
- The average peak gain of antenna is around 3.15 dBi and has omni directional radiation pattern.
- Single band notch characteristics are successfully achieved according to obtained results, which prove that ground stubs work efficiently in order to get single notch characteristics.
- The features of proposed antenna are suitable for applications in wireless devices.

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Figure 2.19 Return Loss of antenna

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Figure 2.18 (a) Top view (b) side view

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Figure 2.20 Return Loss of antenna

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Figure 2.21 simulated and measured return loss

2.5.4 UWB Antenna with Single or Dual Band Notches for Lower WLAN Band and Upper WLAN Band [19]

- UWB antenna is proposed to overcome interference problem due to near-by existing communication systems within UWB frequency range.
- The two antennae having band notch characteristics are presented. The first one is proposed with single band notch and second is for dual band notch function.

2.5.4.1 Single Band Notch

- The fork shaped UWB antenna with one separated strip is proposed. The length and width of a strip behaves as an inductor while the distance between strip and radiator acts like a capacitor and the coupling between the strip and radiator performs the function of stop filter.

- The frequency range covered by presented antenna is from 3 to 12 GHz and band is rejected from 4.98 to 6.03 GHz.
- The results show that the proposed antenna has omni-directional radiation pattern and provides a good notch for lower WLAN band.

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Figure 2.22 Design of antenna (a) front view (b) back view

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Figure 2.24 VSWR w.r.t side shifts

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Figure 2.23 VSWR at varied lengths

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Figure 2.26 VSWR w.r.t down shifts

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Figure 2.25 VSWR at varied widths

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2.5.4.2 Dual Band Notch

- To obtain dual band notch characteristics the shape of the main radiator is kept same while one more strip is added on the radiator so that both the strips acts as two band stop filters at different frequencies.
- The antenna covers bandwidth from 3GHz to 12GHz and has almost omni-directional radiation pattern.
- The result shows that the proposed dual band-notch UWB antenna has goods impedance matching and provides a good band notch for the lower WLAN (5.15GHz-5.35GHz) band and the upper WLAN (5.725-5.825 GHz) band.

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Figure 2.27 Dual band notch design

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Figure 2.28 VSWR measured vs. simulated graph

2.5.5 Combining Two Methods to Enhance Band-Notch Characteristics of Ultra WideBand Antenna [17]

- A planar microstrip-fed monopole antenna with truncated ground plane is proposed in this research paper.
- To enhance band notch characteristics of presented antenna two conventional stop band methods are combined.
- The notch is obtained by attaching a parasitic strip under the substrate and cutting an inverted U-shaped slot on the patch.
- With the compact size of 16x30x1.6mm3 , the proposed antenna has good impedance matching from 3.1GHz to 10.6GHz except at the frequency band for Hyper-LAN II applications.
- Figure 2.30 shows the gain of proposed antenna and it is observed that antenna does not radiate at stop band.
- The designed planar microstrip-fed monopole antenna has omni-directional radiation pattern which is attractive for UWB applications.

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Figure 2.30 Gain of proposed design

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Figure 2.29 Antenna Design (a) front (b) back view

Chapter 3 Co-Planar Waveguide-Fed UWB Antenna with 5GHz WLAN Band Notch Characteristic

Zeeshan Ahmed, Faiz K. Lodhi

In this chapter the parametric analysis of the proposed Co-Planar Waveguide (CPW)-fed antenna with 5GHz WLAN notch band is presented. This chapter also includes the results of gain plots, current distribution, 2D and 3D radiation patterns of the proposed antenna as well as the simulated and measured results of VSWR of proposed antenna.

3.1 Introduction

This report presents a CPW-fed planar monopole micro-strip patch antenna which is designed to achieve Ultra WideBand (UWB) with WLAN band notch. The Ultra WideBand ranges from 3.10GHz to 10.6GHz with a bandwidth of 7.5GHz. The 5GHz WLAN band covers the frequency range from 5.15GHz to 5.35GHz and from 5.725GHz to 5.825GHz. Our main emphasis is to achieve the UWB and reject the 5GHz WLAN frequency band which is reported to interfere with other frequency bands.

The substrate used for simulating and fabricating this antenna is FR-4 with relative permittivity and dielectric loss tangent of 4.4 and 0.02, respectively. The size of the substrate is compact with dimensions of 40x30mm2 having height of 1.6mm. The feeding technique used to design the antenna is the Co-planar Waveguide (CPW) feeding. To achieve good impedance matching with the load we require 50Ω input impedance for which the length and width of the transmission line are kept to be 14mm and 3mm, respectively. The material used for the radiating patch and the transmission line is copper which acts as perfect conductor.

3.2 Design of the Proposed CPW-Fed Antenna

The proposed CPW-fed UWB antenna with WLAN band-notch characteristic consist of a rectangular patch with 7 vertically symmetric staircase ‘Area’ rectangles. The staircase rectangles made possible the achieving of the Ultra Wideband. A U-shaped slot is then embedded into the transmission line of the antenna which efficiently rejects the entire WLAN band. The design of antenna is broken down to several stages which explain the technique used to achieve the desired results.

3.2.1 Ultra WideBand (Without U-Shape Slot)

In the first place the antenna is designed to achieve the Ultra Wideband. FR-4 is chosen as the substrate of the antenna with dimensions and height of 40x30mm2 and 1.6mm, respectively. These dimensions will remain constant throughout the designing procedure of the antenna.

3.2.1.1 Stage 1: 15x15mm2 Patch

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Figure 3.1 Layout of the antenna Stage 1

Figure 3.1 shows the design of the rectangular radiating patch with dimensions of 15x15mm2. The length and width of the transmission line are kept to be 14mm and 2.5mm, respectively. The CPW-ground on either side of the transmission line are equal in size with both having the dimensions of 12.8x13.2mm2. The simulated results of the VSWR of the antenna are shown in Figure 3.2. From the Figure it can be seen that the antenna is not operating in the entire UWB band and from 7.5GHz to 8.7GHz the VSWR>2 which is not a desirable result.

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Figure 3.2 VSWR vs. Frequency at Stage 1

3.2.1.2 Stage 2: 15x29.4mm2 Patch

Figure 3.3 shows the change in the width of the radiating patch with all other dimensions exactly similar to that of Stage 1. The width of the radiating patch is increased to 29.4mm from 15mm. The results of the VSWR are shown in Figure 3.4. With the increase in width, the entire UWB is rejected and not even a single frequency is operating as the whole band lies in the region where VSWR>2.

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Figure 3.3 Layout of the antenna Stage 2

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Figure 3.4 VSWR vs. Frequency at Stage 2

3.2.1.3 Stage 3: Staircase ‘Area 1’

Figure 3.5 shows the addition of the staircase ‘Area’ rectangle to the bottom end of the radiating patch. The rectangle is added in a vertically symmetric way such that it makes a staircase step. The dimensions of ‘Area 1’ are kept to be 1.5x8.4mm2. The results of the VSWR plot are shown in Figure 3.6. From the VSWR plot it can be seen that the antenna is operating from 3GHz to 4.5GHz and the rest of the UWB has VSWR greater than 2.

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Figure 3.5 Layout of the antenna Stage 3

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Figure 3.6 VSWR vs. Frequency at Stage 3

3.2.1.4 Stage 4: Staircase ‘Area 2’

Figure 3.7 shows the addition of another staircase rectangle in the radiating patch. ‘Area 2’ has the dimensions of 1.5x12.4mm2. The effect of adding ‘Area 2’ can be noticed in the VSWR in Figure 3.8. The addition of ‘Area 2’ has shown some promising results as the antenna is now operating between 3GHz to 5.5GHz in the UWB range.

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Figure 3.7 Layout of the antenna Stage 4

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Figure 3.8 VSWR vs. Frequency at Stage 4

3.2.1.5 Stage 5: Staircase ‘Area 3’

After the addition of ‘Area 2’, positive changes in achieving the UWB were noticed. This lead to adding another staircase rectangle ‘Area 3’ with dimensions of 1.5x15.4mm2 as shown in Figure 3.9. With the addition of ‘Area 3’, the proposed antenna is noticed to be operating from 3GHz to 5.5GHz and from 7.25GHz to 9.30GHz as shown in Figure 3.10.

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Figure 3.9 Layout of the antenna Stage 5

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Figure 3.10 VSWR vs. Frequency at Stage 5

3.2.1.6 Stage 6: Staircase ‘Area 4’

Figure 3.11 shows the addition of ‘Area 4’ as another staircase rectangle with dimensions of 1.5x18.4mm2. From Figure 3.12 it can be seen that no significant changes in the bandwidth of the antenna are observed and the antenna is still operating in the same range as it was with the addition of ‘Area 3’ to the radiating patch.

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Figure 3.11 Layout of the antenna Stage 6

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Figure 3.12 VSWR vs. Frequency at Stage 6

3.2.1.7 Stage 7: STAIRCASE ‘AREA 5’

In the stage 7 of the design procedure, another staircase rectangle is added to the radiating patch of the antenna. This rectangle is referred to as ‘Area 5’ as shown in Figure 3.13. The dimensions of ‘Area 5’ are 1.5x21.4mm2. From Figure 3.14 it can be seen that the addition of this rectangle in the design procedure has brought some drastic changes in operating bandwidth of the antenna. The antenna is now operating over the whole UWB with an exception of 6.35GHz to 6.80GHz where VSWR>2.

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Figure 3.13 Layout of the antenna Stage 7

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Figure 3.14 VSWR vs. Frequency at Stage 7

3.2.1.8 Stage 8: Staircase ‘Area 6’

Figure 3.15 shows the addition of ‘Area 6’ to the radiating patch of the antenna. The addition of ‘Area 6’ with dimensions of 1.5x24.4mm2 didn’t produce any significant changes to the bandwidth of the antenna and the antenna is still not operating between 6GHz to 7GHz band of the UWB as shown in Figure 3.16.

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Figure 3.15 Layout of the antenna Stage 8

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Figure 3.16 VSWR vs. Frequency at Stage 8

3.2.1.9 Stage 9: Staircase ‘Area 7’

In the stage 9 of the design procedure, another staircase ‘Area’ rectangle is added to the patch of the antenna. Figure 3.17 shows the design of the antenna after adding the ‘Area 7’ with dimensions of 1.5x27.0mm2. The addition of ‘Area7’ proves to be the final amendment made in the radiating patch of the antenna as the proposed antenna has now achieved UWB which can be seen in Figure 3.18. From the Figure it can be seen that the proposed antenna is now operating from 2.88GHz to 13.74GHz which covers the entire UWB range from 3.10Ghz to 10.6GHz.

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Figure 3.17 Layout of the antenna Stage 9

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Figure 3.18 VSWR vs. Frequency at Stage 9

3.2.1.10 Stage 10: Polishing Results

The next step before the WLAN notch is implemented is to change the dimensions of Transmission Line and the CPW-Grounds on either side of the transmission line. The width of the Transmission Line is now increased to 3.0mm from 2.5mm and the width of the CPW-Ground is reduced to 13.0mm from 13.2mm. The VSWR results produced from these changes are shown in Figure 3.19. From the Figure it can be seen that these changes have helped to increase the bandwidth of the antenna. The antenna is now operating between 2.688GHz to 17.506GHz providing a huge fractional bandwidth of more than 146%.

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Figure 3.19 VSWR vs. Frequency at Stage 10

3.2.1.11 Effect of Varying ‘d’ on Bandwidth

The separation distance between the radiating patch of the antenna and the CPW-Ground ‘d’ is altered and its effects on bandwidth are noticed. The results of VSWR are shown in Figure 3.20. It is deduced that a minute change in ‘d’ effects the bandwidth significantly. As the separation distance between the ground and the patch increases, the impedance bandwidth starts to reduce and at d=1.0mm, the antenna is not operating from 6.542GHz to 9.356GHz which, indeed, is not a desirable result. With the increase in ‘d’ from 1.2mm to 1.4mm, it is observed that, even though the antenna is operating in the UWB range, the results are hap-hazard and the antenna covers less bandwidth when compared with d=1.2mm. Therefore, the optimum results are observed when d=1.2mm.

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Figure 3.20 VSWR vs. Frequency graph varying ‘d’

3.2.1.12 Effect of Varying ‘g’ on Bandwidth

The effects of varying the gap-width between the CPW-Ground and the Transmission Line ‘g’ are studied carefully. Figure 3.21 shows the VSWR results of ‘g’ at variable distances. From the Figure it can be seen that when g=0.6mm and 0.7mm, the UWB is not achieved but when g=0.5mm, optimum results are obtained.

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Figure 3.21 VSWR vs. Frequency graph varying ‘g’

3.2.2 Ultra WideBand Antenna with WLAN Notch

After achieving the Ultra WideBand frequency range the next step is to notch the WLAN band i.e. from 5.15GHz to 5.35GHz and from 5.725GHz to 5.825GHz. To reject this frequency range, a U-shaped slot is subtracted from the transmission line which ensures the rejection of the WLAN frequency band. The U-shaped slot is added at 3.5mm from the bottom end of the transmission line. Figure 3.22 shows the proposed antenna with U-shaped slot for WLAN band-notch. The line width ‘Wn’ and the base-width ‘Wd’ of the U-shape slot are kept to be 0.6mm and 2.2mm, respectively. Several dimensions of the U-shaped slot are varied in order to obtain the optimum results.

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Figure 3.22 Proposed UWB antenna with band-notch slot

Table 3.1 shows the design parameters of the proposed antenna which describes the details of the values of each parameter used in designing the UWB antenna with WLAN band-notch characteristic.

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Table 3.1 Design Parameters of the proposed antenna

3.2.2.1 Effect of Varying ‘Ln’

Figure 3.23 shows the VSWR graphs of the proposed antenna by varying the slot length parameter Ln and fixing the other parameters. It is observed that with Ln=8.1mm, the desired band is rejected. In the case where Ln= 7.9mm, the lower band of the WLAN, i.e. 5.15GHz, is not notched. On the other hand when Ln=8.3mm the upper band of the desired range is not rejected. Therefore, Ln=8.1mm is taken for further study.

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Figure 3.23 VSWR vs. Frequency graph varying Ln

3.2.2.2 Effect of Varying ‘Wn’

In Figure 3.24, the results of the VSWR versus frequency plot when ‘Wn’ is varied are shown. From the graph it can be observed that the optimum results are achieved when Wn=0.6mm. With Wn=0.5mm and 0.7mm, the lower band of the WLAN band is not notched. Therefore, Wn=0.6mm is taken for further study.

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Figure 3.24 VSWR vs. Frequency graph varying Wn

3.3 Simulated Results of the Proposed Antenna

3.3.1 VSWR with WLAN Notch

The simulated results of the VSWR of the proposed antenna are shown in Figure 3.25. From the Figure it is observed that the antenna has two resonant modes i.e. from 2.844GHz to 5.008GHz and from 5.940GHz to 13.928GHz. From 5.010GHz to 5.938GHz the VSWR>2 which verifies the successful rejection of the unwanted WLAN band.

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Figure 3.25 Simulated VSWR vs. Frequency graph of the proposed antenna with U-shape slot

3.3.2 Return Loss with WLAN Notch

The simulated results of the Return Loss (S11 Parameter) of the proposed antenna are shown in Figure 3.26. From the Figure it is observed that the proposed antenna is operating from 2.882GHz to 4.958GHz and from 5.962GHz to 13.896GHz. From 4.960GHz to 5.960GHz the S11>-10dB which proves that the antenna is not operating in the WLAN band.

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Figure 3.26 Simulated Return Loss vs. Frequency graph of the proposed antenna with U-shape slot

3.3.3 Radiation Patterns

3.3.3.1 2-D Plots of Radiation Pattern

The radiation patterns of the proposed UWB antenna with WLAN band-notch characteristic are shown below. The radiation patterns are simulated at 3GHz, 3.5GHz, 4GHz, 5GHz, 5.5GHz, 6GHz, 7GHz, 8GHz and 9GHz for Eθ and Eφ planes, respectively.

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Figure 3.27 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.0GHz

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Figure 3.28 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 3.5GHz

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Figure 3.29 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 4.0GHz

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Figure 3.30 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5.0GHz

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Figure 3.31 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 5.5GHz

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Figure 3.32 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 6.0GHz

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Figure 3.33 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 7.0GHz

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Figure 3.34 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 8.0GHz

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Figure 3.35 Radiation pattern of UWB antenna with WLAN notch for Eθ rotation at 9.0GHz

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Figure 3.36 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.0GHz

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Figure 3.37 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 3.5GHz

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Figure 3.38 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 4.0GHz

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Figure 3.39 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.0GHz

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Figure 3.40 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 5.5GHz

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Figure 3.41 Radiation pattern of UWB antenna with WLAN notch for Eφ rotation at 6.0GHz

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