Design and Analysis of Microstrip Patch Antenna Arrays
Ahmed Fatthi Alsager
This thesis comprises 30 ECTS credits and is a compulsory part in the Master of Science with a Major in Electrical Engineering– Communication and Signal processing. Thesis No. 1/2011
Design and Analysis of Microstrip Patch Antenna Arrays
Ahmed Fatthi Alsager, [email protected]
Master thesis
Subject Category: Electrical Engineering– Communication and Signal processing
University College of Borås School of Engineering SE‐501 90 BORÅS Telephone +46 033 435 4640
Examiner: Samir Al‐mulla, Samir.al‐[email protected]
Supervisor: Samir Al‐mulla
Supervisor, address: University College of Borås
SE‐501 90 BORÅS
Date: 2011 January
Keywords: Antenna, Microstrip Antenna, Array
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To My Parents
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ACKNOWLEGEMENTS
I would like to express my sincere gratitude to the School of Engineering in the University of Borås for the effective contribution in carrying out this thesis.
My deepest appreciation is due to my teacher and supervisor Dr. Samir Al-Mulla.
I would like also to thank Mr. Tomas Södergren for the assistance and support he offered to me.
I would like to mention the significant help I have got from:
Holders Technology
Cogra Pro AB
Technical Research Institute of Sweden SP
I am very grateful to them for supplying the materials, manufacturing the antennas, and testing them.
My heartiest thanks and deepest appreciation is due to my parents, my wife, and my brothers and sisters for standing beside me, encouraging and supporting me all the time I have been working on this thesis.
Thanks to all those who assisted me in all terms and helped me to bring out this work.
Ahmed Fatthi Alsager
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ABSTRACT
The performance and advantages of microstrip patch antennas such as low weight, low profile, and low cost made them the perfect choice for communication systems engineers. They have the capability to integrate with microwave circuits and therefore they are very well suited for applications such as cell devices, WLAN applications, navigation systems and many others
In this thesis; a compact rectangular patch antennas are designed and tested for GPS devices at 1.57542 GHz, and for a satellite TV signal at 11.843 GHz and 11.919 GHz. The final part of this work has been concentrated on studying an array antenna with two and four elements. The antennas of the design examples of this work has been manufactured and tested in laboratory.
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Table of contents
Acknowledgments 4
Abstract 5
1 Chapter One: Introduction to Antennas 8 1.1. Introduction 1.2. Simple Dipole Antenna 1.3. Radiation Pattern 1.4. Directional Antennas 1.5. Microwave Antennas 1. Parabolic Reflector 2. Horn Antenna 2 Chapter Two: Microstrip Antenna 16 2.1. Introduction 2.2. Types of Patch Antennas 2.3. Feeding Methods 2.3.1 Microstrip Line Feed 2.3.2 Coaxial Feed (Coplanar Feed) 2.3.3 Proximity Coupling 2.3.4 Aperture Coupling 3 Chapter Three: Methods of Analysis 22 3.1 Transmission Line Method 3.2 Cavity Method 3.3 The Ground Plane 4 Chapter Four: Antenna Parameters 30 4.1 Radiation Pattern 4.2 Efficiency and Quality Factor 4.3 Directivity and Gain 4.4 Impedance Matching 4.5 Return Loss 4.6 Polarization 5 Chapter Five: Design Method 39 5.1 Design Methods
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5.2 Example one: GPS antenna Scattering parameters 5.3 Example Two: Satellite TV Signal 6 Chapter Six: Array Antenna 65 6.1 Introduction 6.2 Two Element Array 6.3 Linear Array 6.4 Example 3: Microstrip Array Antenna
Appendix A: 77
Appendix B: 78
References 79
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1. Chapter One: Introduction to Antennas 1.1. Introduction
Antennas are key components of any wireless system [1, and 10]. An antenna is a device that transmits and/or receives electromagnetic waves. Most antennas are resonant devices, which operate efficiently over a relatively narrow frequency band. An antenna must be tuned to the same frequency band that the radio system to which it is connected operates in, otherwise reception and/or transmission will be impaired. The receiving antenna as a part in the system is responsible of turning the electromagnetic waves into its original form (electrical signal in wire). The properties of the transmitting and receiving antennas are fully represented by Maxwell’s equations (equations (4.31) to (4.34)). The dipole antenna was the first type of antenna to be ever used and the simplest one to study and understand, it is a strait wire fed from the centre. To tune the wire to be effective to transmit and receive electromagnetic waves, the length of it should be half the wavelength of the operating frequency. For example for a frequency of 300MHz with a wavelength 1 metre, 0.5 metre antenna is required.
Figure (1.1) Equivalent electric and magnetic surface current densities of a dipole antenna
1.2. Simple Dipole Antenna
To understand the function of the antenna we consider the antenna to be enclosed by a surface volume and radiate in homogenous space (free space). It can be replaced by an electromagnetic source of two current densities (figure (1.1)):
If is the Electric current density