frequency agile antenna integrated with band pass...

i

FREQUENCY AGILE ANTENNA INTEGRATED WITH BAND PASS

FILTER

AHMAD MARWAN BIN MOHAMAD DAHLAN

UNIVERSITI TEKNOLOGI MALAYSIA

ii

FREQUENCY AGILE ANTENNA INTEGRATED WITH BAND PASS FILTER

AHMAD MARWAN BIN MOHAMAD DAHLAN

A thesis is submitted in fulfilment of the

requirements for the award of the degree of

Master of Engineering (Electrical)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

OCTOBER 2013

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To my beloved parents Mohamad Dahlan Omar and Norlida Nordin,

my lovely wife and daughter

and finally my cherished siblings.

iv

ACKNOWLEDGEMENT

In the Name of ALLAH The Most Benevolent, The Most Merciful

Alhamdulillah, praise be to ALLAH s.w.t to Whom we seek help and

guidance and under His benevolence we exist and without His help this project could

not have been accomplished.

I would like to express my deepest appreciation and gratitude to my supervisor, Dr

Muhammad Ramlee bin Kamarudin, for all the support, guidance and time he given

to me during my research. I am most thankful to my family members especially my

parents and fiancé for their nonstop encouragement. Not to be forgotten my fellow

researches in wireless technology, Norsiha, Rajaei, Musyidul Izdam, Arsany, Zairil,

Faizal and Amirudin for the knowledge and help they share. Not to be forgotten

all Wireless Communication Centre (WCC, FKE UTM) members (staffs and

research students) for their readiness to lend a hand in time of need. Finally, thank

you to all who has contributed to this research directly and indirectly.

v

ABSTRACT

In the era of wireless communication, new problem arises when user’s

attention increases together with new development of wireless applications. The

limited frequency spectrum, which allows only one application to operate at the same

time and frequency, has created resource issue for the wireless communication

industry. Hence, new frequency agile technologies such as Software Define Radio

and Cognitive Radio systems are being developed. One of the requirements of this

type of application is an antenna system that is able to change its operating frequency

as instructed by the back end system. This research explores the possibility of

integrating band pass filters to manipulate the operating frequency of a broadband

antenna. RF diode, inductors and capacitors are used as switching mechanism to

actively change the operating frequency. Based on the spectrum allocation in

Malaysia, frequency range from 1GHz to 6GHz was chosen due to the allocation of

many types of communication applications such as mobile applications, unlicensed

band and satellite communication. A proof of concept was done for active switching

at 1.3GHz and 2GHz of the antenna prototype. Another structure was fabricated to

implement frequency reconfigurability operation at 1.3GHz, 2GHz, 3GHz, 4GHz,

5GHz and 6GHz using copper strips instead of active elements. Simulated and

measured results showed good agreement for 1.3GHz – 2GHz active switching

prototype while 1.3GHz – 6GHz copper strip prototype shows minor shifts and

degradation at high frequencies in measured result. From the data collected in this

research, band pass filter integrated antenna shows high potential to be used as

frequency agile antenna with active switching capability. The results from simulation

and measurement of fabricated structures are analyzed and discussed in detail in this

thesis. This research contributes to the development of frequency agile antenna

design for future frequency agile application.

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ABSTRAK

Pada zaman perhubungan tanpa wayar, wujud permasalahan baru apabila

teknologi tanpa wayar terus mendapat perhatian pengguna dan pelbagai aplikasi baru

yang sedang dibangunkan. Jalur frekuensi yang terhad membolehkan hanya satu

aplikasi beroperasi pada waktu dan frekuensi yang sama telah menghasilkan isu

sumber dalam industri perhubungan tanpa wayar. Maka, teknologi frekuensi tangkas

baru sedang dibangunkan contohnya Software Defined Radio dan juga Cognitive

Radio. Salah satu keperluan teknologi seperti ini adalah sistem antena yang mampu

mengubah frekuensi operasinya seperti yang diarahkan oleh sistem belakang.

Penyelidikan ini meneroka kebarangkalian untuk mengawal frekuensi operasi sebuah

antena jalur lebar dengan mengintegrasikan penapis lulus jalur. Diod frekuensi radio

(RF), peraruh dan kapasitor digunakan untuk mengawal frekuensi operasi secara

aktif. Berdasarkan peruntukan spektrum di Malaysia, julat frekuensi dari 1GHz

hingga 6GHz telah dipilih kerana kebanyakan aplikasi komunikasi berada dalam

julat ini seperti komunikasi bergerak, jalur tanpa lesen dan komunikasi satelit. Satu

bukti konsep telah dijalankan bagi membuktikan keupayaan suis aktif pada operasi

1.3GHz dan 2GHz. Sebuah struktur prototaip lain telah difabrikasi untuk operasi

1.3GHz, 2GHz, 3GHz, 4GHz, 5GHz dan 6GHz dengan menggunakan jalur tembaga

berbanding penggunaan unsur-unsur aktif. Keputusan dari simulasi dan yang diukur

menunjukkan persetujuan yang baik bagi prototaip operasi 1.3GHz – 2GHz

manakala bagi operasi 1.3GHz – 6GHz, perubahan kecil dan kemerosotan dapat

diperhatikan di frekuensi tinggi pada keputusan yang diukur. Dari data yang

dikumpul dalam penyelidikan ini, antena yang diintegrasi dengan penapis lulus jalur

menunjukkan potensi yang tinggi untuk digunakan sebagai antena tangkas jalur

dengan keupayaan pensuisan aktif. Keputusan yang diperoleh dari simulasi dan

pengukuran struktur yang telah difabrikasi dianalisa dan dibincangkan dengan

terperinci di dalam tesis ini. Penyelidikan ini menyumbang dalam perkembangan

rekaan antena tangkas frekuensi untuk aplikasi tangkas frekuensi masa hadapan.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xvi

LIST OF ABBREVIATIONS xvii

LIST OF APPENDIX xviii

1 INTRODUCTION 1

1.1 Background 1

1.2 Problem Statement 3

1.3 Objectives 4

1.4 Scope of Work 4

1.4.1 Literature Review 5

1.4.2 Structure Design, Modification,

Simulation and Optimization

5

1.4.3 Antenna Fabrication 5

1.4.4 Structure Testing and Measurement 6

1.5 Thesis Outline 6

viii

2 THEORY AND LITERATURE REVIEW 7

2.1 Antenna 7

2.1.1 Basics 8

2.1.2 Types of Antenna 11

2.1.3 Performance Enhancement on Printed

Antennas

13

2.2 Microwave Filter 14

2.2.1 Printed Band Pass Filter 16

2.3 Reconfigurable Antenna 19

2.3.1 Frequency Reconfigurable Antenna 19

2.4 Frequency Agile Applications 21

2.5 Related Work in Frequency Reconfigurable

Antenna and Filter

22

2.5.1 Two Port Frequency Reconfigurable

Antenna For Cognitive Radio

22

2.5.2 A Dual Port Wide-Narrowband

Antenna for Cognitive Radio

24

2.5.3 Implementation of UWB Antenna with

Bandpass Filter using Microstrip-to-

CPW

26

2.5.4 Electronically Switchable Dual-Band

Microstrip Interdigital Bandpass Filter

for Multistandard Communication

Application

29

3 METHODOLOGY 31

3.1 Introduction 31

3.2 Design Specifications 33

3.3 Considerations and Limitations 33

3.4 Materials and Components 34

3.5 Procedures 35

3.5.1 Simulation 35

3.5.2 Fabrication 35

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3.5.3 Measurement 37

4 ANTENNA AND BAND PASS FILTER 39

4.1 Introduction 39

4.2 Antenna Design 40

4.2.1 Glass-Shaped Printed Monopole 40

4.2.2 U-Shaped Printed Monopole 41

4.2.3 Shorted Circular Patch Printed

Monopole with Steps

42

4.3 Antenna Performance and DIscussion 44

4.4 Filter Design 47

4.4.1 1.3GHz and 2GHz Interdigital Band

Pass Filter

48

4.4.2 3GHz and 4GHz Interdigital Band

Pass Filter

50

4.4.3 5GHz and 6GHz Interdigital Band

Pass Filter

51

4.5 Interdigital Filters Results and Discussions 52

5 ANTENNA INTEGRATED WITH BAND PASS

FILTER

56

5.1 Introduction 56

5.2 Antenna Integrated with Band Pass Filter 57

5.3 Antenna Integrated with Band Pass Filter

Results and Discussions

62

5.3.1 Return Loss Analysis 62

5.3.2 Radiation Pattern Analysis 68

5.3.3 Surface Current Plot 70

6 CONCLUSION AND RECOMMENDATIONS 73

6.1 Conclusion 73

6.2 Recommendation for future research 75

x

REFERENCES 76

Appendix A: Diode Biasing Circuit 79

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Summary, advantages and room for improvement 24

2.2 Summary, advantages and room for improvement for

dual port dual antenna design

26


antenna integrated with fixed BPF

28


frequency reconfigurable interdigital band pass filter

31

4.1 Parameters for the 1.3GHz and 2GHz filter 49

4.2 Parameters for the 3GHz and 4GHz filter 51

4.3 Parameters for the 5GHz and 6GHz filters 52

5.1 Wavelengths at specific frequencies 58

5.2 List of activated switches for each frequency 61

5.3 Simulated gain of finalized structure 70

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Return loss versus frequency graph 9

2.2 E-Plane radiation pattern 10

2.3 H-Plane radiation pattern 10

2.4 3D plot of radiation pattern 11

2.5 Conventional shapes of patch antennas 12

2.6 Basic structure of monopole (a,b) and dipole (c) antenna 12

2.7 Parabolic dish antenna for satellite communication 12

2.8 A circular printed monopole with slots and steps. (a)

antenna structure (b) surface current distribution at

4GHz (c) surface current distribution at 6GHz (d)

surface current distribution at 9GHz [12]

14

2.9 Types of filter 15

2.10 Low pass filter configurations. (a) T-Network (b) π-

Network

16

2.11 High pass filter configurations. (a) T-Network (b) π-

Network

16

2.12 General configuration of end-coupled microstrip

bandpass filter

17

2.13 General structure of parallel-coupled microstrip band

pass filter

17

2.14 General configuration of interdigital bandpass filter 18

2.15 A design of frequency retuneable square ring patch

antenna

20

2.16 Dual band reconfigurable CPW patch antenna with

MEMs

20

2.17 Antenna and filter design 23

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2.18 Transmission loss with varying slot gap width 23

2.19 Narrow band return loss 23

2.20 Very wide band return loss 24

2.21 Dual port and dual antenna design 25

2.22 Return Loss of Dual port and Dual Antenna Design: a)

UWB Antenna, b) Narrow Band Antenna

25

2.23 Overall structure of antenna integrated with fixed BPF 27

2.24 Components of antenna integrated with fixed BPF: a) UWB antenna, b) BPF with band reject

27

2.25 Return loss of antenna integrated with fixed BPF: a)

UWB antenna, b) BPF with band reject, c) simulated

and measured results for whole structure

28

2.26 “Near Frequency” reconfigurable interdigital BPF: a)

filter design, b) return loss while switch is “ON” and

“OFF” state

30

2.27 “Far Frequency” reconfigurable interdigital BPF: a)

filter design, b) return loss while switch is “ON” and

“OFF” state

30

3.1 Flow chart of the overall project activities part 1 32

3.2 Structure of FR4 Board 34

3.3 UV Mask using transparency 36

3.4 UV exposure device 36

3.5 Developing image on FR4 board 36

3.6 Removing unwanted part of copper layer 37

3.7 Agilent E5071C-2K5 2-port VNA 38

4.1 Glass-shaped printed monopole antenna 41

4.2 U-shaped printed monopole antenna 42

4.3 Shorted circular printed monopole antenna: a) front

side, b) back side

44

4.4 Simulated Return Loss (dB) versus frequency (GHz) for

Glass-Shaped, U-Shape and Shorted-Circular patch

printed monopole

45

4.5 Simulated and measured Return Loss (dB) versus 46

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frequency (GHz) for Shorted-Circular patch printed monopole

4.6 Simulated radiation pattern 3D plot at 2GHz: a) Glass-

Shape Antenna, b) U-Shape Antenna, c) Shorted-

Circular Patch Antenna

47

4.7 1.3GHz and 2GHz frequency reconfigurable interdigital

filter design

49

4.8 1.3GHz and 2GHz frequency reconfigurable interdigital

filter parameters

50

4.9 3GHz and 4GHz frequency reconfigurable interdigital

filter design: a) 3GHz, b) 4GHz

51

4.10 Basic structure of interdigital filter for 5GHz and 6GHz

operation

52

4.11 Simulated and measured Return Loss (dB) versus

frequency (GHz) for Filter A with diode “On”

53


frequency (GHz) for Filter A with diode “Off”

53


frequency (GHz) for Filter B, Filter C and Filter D

55

5.1 Block diagram of final structure 57

5.2 Top layer of finalized structure with transmission line

dimensions

59

5.3 Top layer of integrated structure with switch numbering 60

5.4 Bottom layer of integrated structure 60

5.5 Integrated structure prototype: a) Top layer, b) Bottom

layer

61

5.6 Simulated Return Loss versus frequency for antenna

integrated with band pass filter

62

5.7 Measured Return Loss versus frequency for antenna

integrated with band pass filter

63

5.8 Simulated and measured return loss versus frequency of

finalized structure at 1.3GHz

64



64

xv



65



65



66



66

5.14 Simulated radiation pattern for finalized structure: a)

1.3GHz, b) 2.0GHz, c) 3.0GHz, d) 4.0GHz, e) 5.0GHz,

f) 6.0GHz

69

5.15 Simulated surface current for integrated structure at

1.3GHz

70


2GHz

71


3GHz

71


4GHz

71


5GHz

72


6GHz

72

xvi

LIST OF SYMBOLS

ε eff - Effective Dielectric Constant

ε r - Dielectric Constant

h - Substrate Thickness

W - Width

L - Length

f r - Resonant Frequency

υ0 - Free-space Velocity of Light; 3 x 108

ΔL - Length extension

λo - Wavelength

fH - Higher Operating Frequency

fL - Lower Operating Frequency

a - Radius of sphere

𝜂𝑎 - Efficiency of ESA

Rr - Radiation Resistance

Rm - Material Loss Resistance

ηs - efficiency of system

ηm - efficiency of matching network

Tx - Transmitter

Rx - Receiver

xvii

LIST OF ABBREVIATIONS

CR - Cognitive Radio

SDR - Software Defined Radio

GHz - Giga Hertz

ISM - Industrial Scientific Medical

GSM - Global System for Mobile Communications

TV - Television

FR4 - Flame Retardant 4

MHz - Mega Hertz

RF - Radio Frequency

BW - Bandwidth

3D - Three Dimensional

CPW - Co-planar Waveguide

SMA - SubMiniature version A

IF - Interdigital Filter

UWB - Ultra Wide Band

dB - Decibel

LPF - Low Pass Filter

BPF - Band Pass Filter

HPF - High Pass Filter

BSF - Band Stop Filter

CST - Computer Simulation Technology

VNA - Vector Network Analyzer

MEMs - Microelectromechanical Systems

UMTS - Universal Mobile Telecommunications System

LTE - Long Term Evolution

xviii

LIST OF APPENDIX

APPENDIX TITLE PAGE

A Diode Biasing Circuit 79

CHAPTER 1

INTRODUCTION

Research background, problem statement, objective of the research, scopes of

the project and thesis outline is presented in this chapter.

1.1 Background

The emergence of reconfigurable antennas has enabled wireless

communication industry to expand wireless technology and system complexity.

Reconfigurability in frequency has enable multi operating frequency while antenna

with beam steering capability able to focus the antenna coverage towards desired

location. Cognitive Radio (CR) and Software Defined Radio (SDR) are two

examples that uses multiple operating frequency [1-2]. The purpose of these

technologies is to increase the utilization of the available frequency spectrum hence

enabling the network to have larger capacity.

Generally, the spectrum can be classified into two categories, the license and

unlicensed band. The unlicensed band or the ISM band (Industrial, Science and

2

Medical) which is 2.4 GHz and 5.8 GHz are usually used by various short range

wireless consumer products such as WiFi, Bluetooth, wireless mouse, keyboard and

other wireless user interface [3]. The free ISM band suffers from high spectrum

occupancy due to the number of users that would create interference even though

various techniques such as frequency hopping and code division multiple access

have been applied.

On the other hand, the licensed band could only be use by the company that

pays for the certain frequency range. Example of such band is the GSM band, TV

band, armature radio band and Satellite bands [3]. These bands are not usually being

utilized all time. In some cases, the bands would be used periodically and in some

scenario, the band would be occupied only once a year in a small area.

Currently, CR has gained attention from researchers around the world to

develop the system as it is hoped to be the solution to spectrum insufficiency

problem. There are no standards presently set for CR but some of the researchers are

focusing on the TV band while others set their own operating frequency range [4]. In

Malaysia, the Multimedia and Communication Commission (MCMC) has allocated

1GHz to 6GHz of the spectrum to applications such as mobile communication,

satellite communication and ISM [3]. Some of these applications will not always use

the frequency allocated for them or their coverage are small. It is suitable for

unlicensed applications such as SDR and CR to temporary occupy the licensed band.

Hence, the frequency range from 1GHz to 6GHz was chosen as the frequency range

for this research.

One of the most important components in a wireless system is the antenna. A

good antenna ensures the coverage area specification is met as well as the signal

power and quality. For frequency agile application, new types of antenna need to be

designed since the concept of dynamic operating frequency in this system requires

the antenna to operate at broad bandwidth for scanning process as well as narrow

bandwidth for the data transfer process [5].

3

In this research, a broadband antenna were designed from conventional

circular patch antenna by implementing bandwidth enhancing techniques such as

shorting pin, slot and steps. The designed broadband antenna will be integrated with

filters to limit and control the operating frequency. A proof of concept was done by

integrating the broadband antenna with a dual frequency band pass filter operating at

1.3GHz and 2GHz. RF diodes were used as switches to manipulate the filter stub

length for narrow band operation. Another structure was also fabricated to

incorporate four band pass filter for narrow band operation at 1.3GHz, 2GHz, 3GHz,

4GHz, 5GHz and 6GHz. Copper strips were used instead of RF diodes for the second

structure. However, by integrating multiple filters to the antenna, the overall

structure will be larger and the complexity in fabrication will also increase.

1.2 Problem Statement

Spectrum is a scarce recourse in wireless communication world. Nowadays,

most of the available spectrum has been assigned to specific applications, the only

free band to be used by general consumer is the ISM bands. A lot of application such

as Bluetooth and WiFi that operates in small coverage areas share the ISM bands. In

some areas such as highly populated cities, the number of ISM band users is high

which would cause interference between the users. This fact calls for a solution to

avoid further disturbance in the wireless service as more users will use the services

each coming day.

Antennas need to be designed for each application so that it could deliver the

signal to its best. Moreover, compact antenna is highly desirable in modern society

where everything is preferred to be mobile, small and light weighted. For frequency

agile applications, the antenna should not only meet the expectation of normal

antennas, it should also be able to reconfigure its operating frequency on demand by

the back end system. Additional requirement for CR system is the antenna should

4

also be able to operate at broad bandwidth so that it could detect “holes” in the

spectrum. The antenna and system development of Cognitive Radio (CR) are still

in early stage. Some prototype antenna designs published in papers, conferences and

journals can be use as reference in designing future antennas for CR.

1.3 Objective

• To design a frequency reconfigurable antenna for frequency agile

applications.

• To design band pass filters to be integrated with a broadband antenna that

will limit and determine the operating frequency of the antenna.

• To analyze the performance of the structure designed in terms of bandwidth,

operating frequency, return loss and gain.

1.4 Scopes of Work

This research involves four scope of work, which begins with literature

review, followed by structure design process, fabrication and measurement.

5

1.4.1 Literature Review

Some reviews from previous works that have been done on the design of

reconfigurable antenna specifically for CR.

1.4.2 Structure Design, Modification, Simulation and Optimization

Several structures of antenna integrated with filters were designed which are

reconfigurable, compact and suitable for frequency agile application. The structure of

the antennas will be planar on the FR4 dielectric substrate. The design will include

an antenna simulations and optimizations using CST Design Studio.

1.4.3 Antenna Fabrication

The designed and simulated antennas were fabricated on the dielectric

material (FR4 substrate). Implementation of RF diodes and SMA connectors will be

conducted in this stage.

6

1.4.4 Structure Testing and Measurement

The fabricated structures were measured at different frequencies ranging

from 1GHz to 6GHz. The return loss of the reconfigurable antenna will be measured

at all possible configuration. The measured and simulated results will be compared

for further optimization purpose until a finalized design is obtained.

1.5 Thesis Outline

The thesis consists of seven chapters starting with introduction which

explains the background, problem statement, scope of work and objectives of this

research. In Chapter 2, fundamental theories on antenna and filter design are

explained as well as review on previous researches that are related to this research.

The methodology, considerations and limitations involved in this research are

discussed in Chapter 3. Chapter 4 explains the design of the antenna and filter

prototypes in detail which includes all measurements and functions. Results obtained

from simulation and measurement for antenna and filter designed are also analyzed

this chapter. Chapter 5 explains about the design of integrated structure. The

simulated and measured results of the integrated structure are discussed as well as

comparison on performance between stand alone structure and integrated structure.

Discussions are focused on return loss as this affects the operating frequency.

Conclusion of the research and recommendations on future research are stated in

Chapter 6.

76

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77

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21. F.Mahe, G.Tanne, E.Rius, C.Person, S.Toutain, F.Biron, L.Billonnet, B.Jarry and P. Guillon, ‘Electronically Switchable Dual-Band Microstrip Interdigital Bandpass Filter for Multistandard Communication Applications’, Microwave Conference 2000.

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