THE FLORIDA STATE UNIVERSITY COLLEGE OF ENGINEERING DESIGN OF A COMPACT MICROSTRIP PATCH ANTENNA FOR USE IN WIRELESS/CELLULAR DEVICES.

Transcription

1 THE FLORIDA STATE UNIVERSITY COLLEGE OF ENGINEERING DESIGN OF A COMPACT MICROSTRIP PATCH ANTENNA FOR USE IN WIRELESS/CELLULAR DEVICES By: Punit S. Nakar A Thesis submitted to the Department of Electrical And Computer Engineering in partial fulfillment of the requirements for the degree of Master of Science Degree awarded: Spring semester, 2004

2 The members of the committee approve the thesis of Punit S. Nakar defended on March 4, Dr. Frank Gross, Professor Directing Thesis Dr. Krishna Arora, Committee member Dr. Rodney Roberts, Committee member Approved: Dr. Reginald Perry, Chair, Department of Electrical and Computer Engineering Dr. C.J. Chen, Dean, FAMU-FSU College of Engineering The Office of Graduate Studies has verified and approved the above named committee members. ii

3 To my family iii

4 ACKNOWLEDGEMENTS I wish to express sincere gratitude to my supervisor Dr. Frank B. Gross for providing me an opportunity to work in the Sensor Systems Research Lab. His invaluable guidance and support have added a great deal to the substance of this thesis, and taught me an enormous amount in the process. Dr. Gross patiently went over the drafts suggesting numerous improvements and constantly motivated me in my work. I must also thank my committee members Dr. Krishna Arora and Dr. Rodney Roberts for encouraging my academic and research efforts. A special thanks to Dr. Roberts for allowing me access to his research laboratory for carrying out some simulations for this thesis. Besides professors, my friends here at FSU have also given me crucial assistance and fruitful suggestions in my research and academic coursework. I would like to thank them as well for the relaxing discussions I had with them. Last but not least, a very big thank you to my beloved family and my future wife-to-be for their support, love and constant encouragement they have bestowed upon me. Without their support, I would never have gotten so far. iv

5 TABLE OF CONTENTS List of Tables..vi List of Figures... vii Abstract x 1. Background of Wireless Communications Cellular Systems The past Cellular Systems The present Cellular Systems Vision of the future Inside a Cellular Phone Antenna Fundamentals Introduction How an Antenna radiates Near and Far field regions Far field radiation from wires Antenna performance parameters Types of Antennas Microstrip Patch Antenna Introduction Advantages and Disadvantages Feed Techniques Methods of Analysis Microstrip Patch Antenna Design and Results Design Specifications Design Procedure Simulation Setup and Results Conclusions REFERENCES BIOGRAPHICAL SKETCH v

6 LIST OF TABLES 1. Table 3.1 Comparing the different feed techniques Table 4.1 Effect of feed location on center frequency, return loss and bandwidth...53 vi

7 LIST OF FIGURES 1. Figure 1.1 Frequency Reuse pattern Figure 1.2 Cell structure for PCS Figure 1.3 The future vision.4 4. Figure 1.4 User at home, in car, at office, at business trip Figure 1.5 Internal components of a NOKIA cellular phone Figure 1.6 Cellular handset used with the AMPS system Figure 1.7 Cellular handsets used in the past few years Figure 2.1 Radiation from an antenna Figure 2.2 Field regions around an antenna Figure 2.3 Spherical co-ordinate system for a Hertzian dipole Figure 2.4 Radiation pattern of a generic directional antenna Figure 2.5 Equivalent circuit of transmitting antenna Figure 2.6 A linearly (vertically) polarized wave Figure 2.7 Commonly used polarization schemes Figure 2.8 Measuring bandwidth from the plot of the reflection coefficient Figure 2.9 Half wave dipole.23 vii

8 17. Figure 2.10 Radiation pattern for Half wave dipole Figure 2.11 Monopole Antenna Figure 2.12 Radiation pattern for the Monopole Antenna Figure 2.13 Loop Antenna Figure 2.14 Radiation Pattern of Small and Large Loop Antenna Figure 2.15 Helix Antenna Figure 2.16 Radiation Pattern of Helix Antenna Figure 2.17 Types of Horn Antenna Figure 3.1 Structure of a Microstrip Patch Antenna Figure 3.2 Common shapes of microstrip patch elements Figure 3.3 Microstrip Line Feed Figure 3.4 Probe fed Rectangular Microstrip Patch Antenna Figure 3.5 Aperture-coupled feed Figure 3.6 Proximity-coupled Feed Figure 3.7 Microstrip Line Figure 3.8 Electric Field Lines Figure 3.9 Microstrip Patch Antenna Figure 3.10 Top View of Antenna Figure 3.11 Side View of Antenna Figure 3.12 Charge distribution and current density creation on the microstrip patch Figure 4.1 Top view of Microstrip Patch Antenna Figure 4.2 Microstrip patch antenna designed using IE3D Figure 4.3 Return loss for feed located at different locations.. 54 viii

9 40. Figure 4.4 Return loss for feed located at (4, 0) Figure 4.5 Elevation Pattern for φ = 0 and φ = 90 degrees Figure 4.6a 3D view of radiation pattern looking along the Y axis in the XZ plane Figure 4.6b 3D view of radiation pattern looking along the Z axis in the XY plane Figure 4.7a 3D view of radiation pattern for cellular phone orientation in the YZ plane Figure 4.7b 3D view of radiation pattern for cellular phone orientation in the XZ plane...57 ix

10 ABSTRACT The cellular industry came into existence 25 years ago and as of today, there are approximately 150 million subscribers worldwide. The cellular industry generates $30 billion in annual revenues and is one of the fastest growing industries. The cellular handsets being used in the 1980s were bulky and heavy. Advancements in VLSI technology have enabled size reduction for the various microprocessors and signal processing chips being used in cellular phones. Another method for reducing handset size is by using more compact antennas. The aim of this thesis is to design such a compact antenna for use in wireless/cellular devices. A Microstrip Patch Antenna consists of a dielectric substrate on one side of a patch, with a ground plane on the other side. Due to its advantages such as low weight and volume, low profile planar configuration, low fabrication costs and capability to integrate with microwave integrated circuits (MICs), the microstrip patch antenna is very well suited for applications such as cellular phones, pagers, missile systems, and satellite communications systems. A compact microstrip patch antenna is designed for use in a cellular phone at 1.9 GHz. The results obtained provide a workable antenna design for incorporation in a cellular phone. x