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ACKNOWLEDGEMENTS

It would be a great pleasure to write a few words, which would although not suffice as the

acknowledgement of this long cherished effort, but in the absence of which this work would

necessarily be incomplete. So these words of acknowledgement come as a small gesture of

gratitude towards all those people, without whom the successful completion of this project would

not have been possible.

Firstly I owe my profound gratitude to my supervisor Dr. Mithilesh Kumar (Asso. Prof.) for

their valuable guidance, supervision, constant support and encouragement which have made me

as a constant oasis of ideas and passion in science which exceptionally inspire and enrich my

knowledge to complete this dissertation work.

I would like to express deep gratitude towards Dr. Rajeev Gupta (Prof. and Head, Electronics

Engineering Deptt. UCE, Kota). He is like a beam of light for us. His kind guidance showed us

the path of life and is unforgettable.

Also special Thanks and due regards extends to Dr. R. S. Meena, Mr. Pankaj Shukla (Asso.

Prof.), Dr. Girish Parmar and Mr. Deepak Bhatia (Asst. Prof. at UCE, RTU, Kota) for they

extended towards their valuable guidance, indispensable help and inspiration at times. In

appreciation I offer them my sincere gratitude.

I would like to convey my special thanks to Mr. S. P. Chakraborty, C.A.R.E. IIT Delhi for his

untiring technical support. Without his positive attitude and moral support, the project would

have not been completed in time.

Last but not least we would like to thank the Department of Electronics Engineering, UCE Kota

for providing us with the facilities at lab, my beloved family and all my friends and the almighty

god for his blessings. It would have been impossible for me to complete the work without their

valuable guidance & prompt cooperation.

Date Ghanshyam Singh



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ABSTRACT

Planar antennas are extensively used in various wireless and mobile applications. The continuous

growth and commercial interest in wireless communications, especially in personal and mobile

communication systems significantly increases the demand for low cost, compact size, multiple

bands and high performance antennas, which are the key components, used in any

communication systems. The reduction of the antenna’s size, the multiplicity of bands, the ease

of designing the antenna (simple structure) and the need for flexible specifications such as

independent control, is very important in the design of new antennas.

Reconfigurable antennas have more advantages in terms of increasing the antenna capabilities by

tuning or switching its performances. Therefore, the needs to design compact size, simple

structure, low profile, multiple bands antennas are required.

The ability of reconfigurable antennas to tune resonances, change polarization and modify their

radiation patterns, made their development imperative in modern telecommunication systems.

Their agility and diversity created new horizons for different types of applications especially in

cognitive radio, multiple input multiple output systems, satellites and many other applications.

Reconfigurable antennas satisfy the requirements for increased functionality, such as direction

finding, beam steering, radar, control and command, within a confined volume.

Since their rise in the last decade, reconfigurable antennas have made use of many

reconfiguration techniques. The most common techniques utilized revolved around switching

mechanisms. By combining low-loss, high-isolation switches such as MEMS or PIN diode

switches with compatible antenna elements, we can physically reconfigure antennas and their

feed structures providing frequency and polarization diversity. Other techniques such as the

incorporation of variable capacitors, varactors and physical structure alteration surfaced recently

to overcome many problems faced in using switches and their biasing.

Firstly in this work basic conventional microstrip rectangular and circular antenna structures are

designed with the help of standard designing procedures.



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After the conventional structure designing, a novel frequency reconfigurable antenna design and

development is proposed for wireless devices. In the first proposed design, a rectangular patch

antenna with square slot using two PIN diodes at the centre frequency 10 GHz was designed and

simulated frequency reconfiguration is achieved in the frequency range of 10-10.5 GHz and the

measured results shows the same effect in the frequency range of 10.216-10.552 GHz. The

frequency reconfiguration is carried out by switching the diodes on/off states.

After that this same technique is used for the frequency reconfiguration of the circular patch

antenna. In the second proposed design, a circular patch antenna with circular slot using two PIN

diodes at the centre frequency 10 GHz was designed and simulated frequency reconfiguration is

achieved in the frequency range of 9.69-10.2 GHz and the measured results shows the same

effect in the frequency range of 10.33-11.01 GHz.

In the fabricated structure of proposed geometry the diodes are replaced by microstrip line for

on-state as an ideal case. The antenna is designed on FR4 substrate (= 4.54) of thickness (h)

1.6 mm. The proposed structure was simulated by using the electromagnetic (EM) simulation

software. The optimized structure was fabricated using microwave integrated circuit (MIC)

techniques on same substrate. The return loss was measured using the Vector Network Analyzer.

The simulated and measured return loss shows the close agreement.



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LIST OF FIGURES

Figure No. Figure Name Page No.

1.1 Flow chart of the process involved in this project 7

3.1 Basic wave travelling model of s-parameters. 17

3.2 Basic conventional rectangular microstrip patch Antenna structure 20

3.3 Return loss at 10.1 GHz resonance frequency 20

3.4 Insertion loss at 10.1 GHz resonance frequency 21

3.5 Comparison of return loss and insertion loss 21

3.6 E-Field radiation pattern for conventional rectangular patch 22

3.7 H-Field radiation pattern for conventional rectangular patch 22

3.8 Basic conventional circular microstrip patch Antenna structure 24




3.12 E-Field radiation pattern for conventional circular patch 26

3.13 H-Field radiation pattern for conventional circular patch 26

4.1 When both diodes (D1 & D2) are in OFF-state 30





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4.5 E-Field radiation pattern when both diodes (D1 & D2) are in OFF-state

32

4.6 H-Field radiation pattern when both diodes (D1 & D2) are in OFF-

state

32

4.7 When one diode (D1) is in ON-state 33

4.8 Return loss at 10.3GHz resonance frequency 34

4.9 Insertion loss at 10.3GHz resonance frequency 34


4.11 E-Field radiation pattern when one diode (D1) is in ON-state 35

4.12 H-Field radiation pattern when one diode (D1) is in ON-state 36

4.13 When both diodes (D1 & D2) are in ON-state 37




4.17 E-Field radiation pattern when both diodes (D1 & D2) are in ON-state 39

4.18 H-Field radiation pattern when both diodes (D1 & D2) are in ON-state 39

4.19 Fabricated structure when diodes (D1 & D2) are in OFF-state 41

4.20 Measured result when diodes (D1 & D2) are in OFF-state 42



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4.21 Simulated and measured return loss for case-I 42

4.22 Fabricated structures when one diode (D1) is in ON-state 43

4.23 Measured result when one diode (D1) is in ON-state 43

4.24 Simulated and measured Return loss for case-II 44

4.25 Fabricated structures when diodes (D1 & D2) are in ON-state 44

4.26 Measured result when diodes (D1 & D2) are in ON-state 45

4.27 Simulated and measured return loss for case-III 45

4.28 Comparison of simulated return losses 46

4.29 Comparison of measured return losses 47

5.1 When both diodes (D1 & D2) are in OFF-state 50




5.5 E-Field radiation pattern when both diodes (D1 & D2) are in OFF-

state

52

5.6 H-Field radiation pattern when both diodes (D1 & D2) are in OFF-

state

52

5.7 When one diode (D1) is in ON-state 53




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5.11 E-Field radiation pattern when one diode (D1) is in ON-state 55

5.12 H-Field radiation pattern when one diode (D1) is in ON-state 56

5.13 When both diodes (D1 & D2) are in ON-state 57




5.17 E-Field radiation pattern when both diodes (D1 & D2) are in ON-state 59

5.18 H-Field radiation pattern when both diodes (D1 & D2) are in ON-state 59

5.19 Fabricated structure when diodes (D1 & D2) are in OFF-state 60

5.20 Measured result when diodes (D1 & D2) are in OFF-state 61

5.21 Measured and simulated return losses for case-I 61

5.22 Fabricated structures when one diode (D1) is in ON-state 62

5.23 Measured result when one diode (D1) is in ON-state 62

5.24 Measured and simulated return loss for case-II 63

5.25 Fabricated structures when diodes (D1 & D2) are in ON-state 63

5.26 Measured result when diodes (D1 & D2) are in ON-state 64



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5.27 Measured and simulated return losses for case-III 64

5.28 Comparison of simulated return losses 65

5.29 Comparison of measured return losses 66



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LIST OF SYMBOLS

S. No. Symbols Description

1 - Dielectric Constant of Substrate

2 - Wavelength

3 L - Length of Patch Element

4 W - Width of Patch Element

5 c - Speed of Light

6 h - Height of Dielectric Substrate

7 t - Thickness of Patch Element

8 - Free Space Wavelength

9 - Effective Dielectric Constant

10 - Length Extension of Patch

11 - Characteristic Impedance

12 d - Distance of the Port-excitation from the Patch

13 - Incident Power

14 - Reflected Power

15 - Quarter Wave Line Impedance

16 - Antenna Impedance



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LIST OF ACRONYMS

S. No. Acronyms Description

1 MEMS - Micro-electro-mechanical system

2 MIC - Microwave Integrated Circuits

3 MIMO - Multiple input multiple output

4 GSM - Global System Mobile

5 DCS - Distributed Control System

6 PCS - Personal Communication System

7 UMTS - Universal Mobile Telecommunication System

8 LAN - Local Area Network

9 CAD - Computer Aided Design

10 RF - Radio Frequency

11 RHCP - Right Hand Circular Polarization

12 LHCP - Left Hand Circular Polarization

13 PIFA - Planner Inverted F-Antenna

14 PCB - Printed Circuit Board

15 QDL - Quantum Dot Laser

16 OPOMEX - One Port Multiply Excited

17 GA - Genetic Algorithm



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S. No.

18

Acronyms

VSWR -

Description

Voltage Standing Wave Ratio

19 HPBW - Half Power Beam Width

20 IEEE - Institute of Electrical & Electronics Engineers

21 TEM - Transverse Electric-Magnetic

22 3D - Three-Dimensional

23 VNA - Vector Network Analyzer

24 RCS - Radar Cross Section



xiii

CONTENTS

CERTIFICATE i

ACKNOWLEDGEMENTS ii

ABSTRACT iii

LIST OF FIGURES v

LIST OF SYMBOLS x

LIST OF ACRONYMS xi

CHAPTER 1: INTRODUCTION TO RECONFIGURABLE ANTENNAS 1-8

1.1 Introduction 1

1.2 Reconfigurable Antennas Classifications and Categories 1

1.3 Reconfigurable Antennas Functional Mechanism 2

1.4 Reconfigurable Antennas Applications 3

1.5 Microstrip Patch Antenna 4

1.6 Advantages of Microstrip Patch Antenna 4

1.7 Scope of Work 5

1.8 Problem Statement 5

1.9 Methodology of the Project 6

1.10 Project Implementation Strategy 6

1.11 Dissertation Overview 8

CHAPTER 2: LITERTATURE REVIEW 9-14

2.1 Introduction 9



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2.2 Reconfigurable Antennas using Switches 9

2.3 Reconfigurable Antennas using Capacitors or Varactors 11

2.4 Reconfigurable Antennas using Physical Angular Alteration 11

2.5 Reconfigurable Antennas using Different Biasing Networks 12

2.6 Reconfigurable Antenna array 12

2.7 Antennas using Reconfigurable Feeding Networks 12

2.8 Biasing of Switches in Reconfigurable Antenna Structures 13

2.8.1 The Biasing of RF MEMS 13

2.8.2 Biasing of p-i-n and Schottky diodes 14

CHAPTER 3: DESIGN OF CONVENTIONAL MICROSTRIP

PATCH ANTENNA 15-26

3.1 Introduction 15

3.2 Design of Conventional Rectangular Patch Antenna 15

3.2.1 The Design Specifications 15

3.2.2 The S-parameters 17

3.2.3 Radiation Pattern 18

3.2.4 Simulated Structure and Results 19

3.3 Basic Conventional Circular Microstrip Patch Antenna 23

3.3.1 Quarter Wave Transformer 23

3.3.2 Simulated Structure and Results 23



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CHAPTER 4: FREQUENCY RECONFIGURABLE RACTANGULAR

PATCH ANTENNA DESIGN 27-47

4.1 Introduction 27

4.2 Frequency Reconfigurable Rectangular Patch Antenna Structure 28

4.3 Simulated Structures and Results 29

4.3.1 Case-I When Both Diodes (D1 & D2) are in OFF-State 29

4.3.2 Case-II When One Diode (D1) is in ON-State 33

4.3.3 Case-III When Both Diodes (D1 & D2) are in ON-State 36

4.4 Fabricated Structures and Results 40

4.4.1 Fabrication Procedure for Microstrip Patch Antenna 40

4.4.2 Case-I When Both Diodes (D1and D2) are in OFF-State 41


4.4.4 Case-III When Both Diodes (D1 & D2) are in ON- State 44

4.5 Comparison of Simulated and Measured Return Losses for three cases 46

CHAPTER 5: FREQUENCY RECONFIGURABLE CIRCULAR

PATCH ANTENNA DESIGN 48-66

5.1 Introduction 48

5.2 Reconfigurable Circular Microstrip Patch Antenna Structure 48

5.3 Simulated Structures and Results for Circular Patch Antenna 49

5.3.1 Case-I When Both Diodes (D1 & D2) are in OFF-State 49




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5.3.3 Case-III When Both Diodes (D1 & D2) are in ON-State 56

5.4 Fabricated Structures and Results of Circular Patch 60

5.4.1 Case-I When Both Diodes (D1 and D2) are in OFF-State 60


5.4.3 Case-III When Both Diodes (D1 & D2) are in ON- State 63

5.5 Comparison of Simulated and Measured Return Losses for three cases 65

CHAPTER 6: CONCLUSIONS AND FUTURE WORK 67

REFERENCES 69

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