Development of Engineered Magnetic Materials for Antenna Applications by Kevin Buell A dissertation submitted in partial ful¯llment of the requirements for the degree of Doctor of Philosophy (Electrical Engineering) in The University of Michigan 2005 Doctoral Committee: Professor Kamal Sarabandi, Chair Professor John W. Halloran Professor Anthony W. England Associate Professor Amir Mortazawi °c Kevin Buell 2005 All Rights Reserved To my father whose accomplishments have made my successes possible. ii ACKNOWLEDGEMENTS The secret to creativity is knowing how to hide your sources. Albert Einstein Personally, I prefer recognizing here those to whom my success is more rightfully attributed. First, and most importantly- I must acknowledge my mother, who taught me to believe in myself. Thank you, Mom. I would like to acknowledge the support, guidance and encouragement provided by Ronald Guttman, the professor for my undergraduate microwave engineering course at Rensselaer Polytechnic Institute (RPI) and the reason I chose this ¯eld of study. Doctor Guttman was a teacher, a mentor, and a friend. Of course, I also must acknowledge the support and guidance of my doctoral com- mittee; Kamal Sarabandi, John Halloran, Anthony England, and Amir Mortazawi. Of particularly outstanding value has been the guidance of my Kamal Sarabandi, my committee chairman. Doctor Sarabandi is truly a genius of the ¯rst order and perhaps the most intelli- gent person I have ever met. Many times during my doctoral studies I have felt like a child playing in the shadow of a giant. This gentle giant has sheltered me and guided me through numerous technological mine ¯elds, using the trip to teach me and help me develop my own understanding of Electromagnetics in particular and research in a broader sense. For this I am immeasurably grateful. iii Originally it was intended for Doctor Hossein Mosallaei to be a member of my thesis committee. As he has left the University of Michigan to accept a teaching position at Northeastern University, he is no longer o±cially a member of my com- mittee. Nonetheless, he should be recognized as having served as a virtual co-advisor for the last years of my research. It was work supervised by Doctor Sarabandi and Doctor Mosallaei for which I have twice been recognized with the IEEE Antennas and Propagation Society Best Student Paper award in 2003 and 2005, the only student ever so honored. I could not have done it without him. I have been extremely fortunate to receive generous ¯nancial support from numer- ous sources. First, I would also acknowledge the ¯nancial support of the University of Michigan and the National Science Foundation for the joint fellowship which initiated and sustained my doctoral studies for the majority of my graduate career. The second major source of support which I wish to recognize is the Motorola corporation whose fellowship funded me for the 2001-2002 academic year. Finally, the Intel Foundation PhD Fellowship has generously funded the ¯nal year of my Doctoral research dur- ing the 2004-2005 academic year and perhaps as importantly has provided me with mentoring by the Intel CTO. iv TABLE OF CONTENTS DEDICATION .................................. ii ACKNOWLEDGEMENTS . iii LIST OF TABLES . viii LIST OF FIGURES ............................... ix CHAPTERS 1 Introduction . 1 1.1 Overview . 1 1.2 Background . 2 1.3 Method . 5 1.4 Applications of Magneto-Dielectrics . 7 1.4.1 Elements of Research; Material Development, Charac- terization, and Application . 20 1.5 Chapter Outline . 21 1.5.1 Chapter 1: Introduction . 21 1.5.2 Chapter 2: Natural Magnetic Materials . 21 1.5.3 Chapter 3: Metamaterials . 22 1.5.4 Chapter 4: Material Characterization . 22 1.5.5 Chapter 5: A miniaturized Patch Antenna on Magnetic Metamaterial Substrate . 24 1.5.6 Chapter 6: Patch Antenna over Reactive Impedance Surface . 25 1.5.7 Chapter 7: Electromagnetic MetaMaterial Insulator . 25 1.5.8 Chapter 8: Metamaterial Insulator enabled Superdi- rective Array . 26 1.5.9 Chapter 9: Conclusion . 26 2 Natural Magnetic Materials . 27 2.1 Chapter Introduction . 27 2.2 Understanding Natural Magnets . 28 2.3 New Advances in Natural Magnets . 34 v 2.3.1 Application of Impedance Matched Materials . 34 2.3.2 Z-Phase Hexaferrite . 42 2.4 Chapter Conclusions . 42 3 Metamaterials . 44 3.1 Chapter Introduction . 44 3.2 Meta-Materials Background . 45 3.2.1 The split ring resonator for permeability (¹r) . 45 3.2.2 The metallic dipole for permittivity (²r) . 48 3.2.3 Left-Handed Medium and the Negative Index of Re- fraction . 48 3.3 Embedded Circuit Spiral Resonator Metamaterial . 50 3.3.1 Bene¯ts of Magnetic Materials . 51 3.3.2 Embedded Circuit Meta-Materials . 54 3.3.3 E®ective Medium Operation . 56 3.3.4 Equivalent Circuit Model . 57 3.4 Chapter Conclusions . 73 4 Material Characterization . 74 4.1 Chapter Introduction . 74 4.2 Waveguide Characterization Toolkit . 75 4.2.1 E®ectiveness of the waveguide characterization toolkit 80 4.3 Resonant Cavity Method . 81 4.3.1 Frequency Extended Perturbation Technique . 85 4.3.2 Hybrid Perturbation Technique . 92 4.4 A comment on Measuring Anisotropic materials . 103 4.5 Chapter Conclusions . 105 5 A miniaturized Patch Antenna on Magnetic Metamaterial Substrate 107 5.1 Chapter Introduction . 107 5.2 Metamaterial Design and Fabrication . 108 5.3 Metamaterial Performance . 110 5.3.1 Antenna Performance . 114 5.4 Chapter Conclusions . 121 6 Patch Antenna Over Reactive Impedance Surface . 123 6.1 Chapter Introduction . 123 6.2 Motivation . 124 6.3 Patch Antenna over the RIS Substrate . 124 6.4 Fabrication . 134 6.5 Measurement . 134 6.6 Chapter Conclusions . 136 7 Electromagnetic MetaMaterial Insulator . 138 7.1 Chapter Introduction . 138 vi 7.1.1 Preview of Metamaterial Insulators . 138 7.2 Theory of Metamaterial Insulators . 139 7.3 Theoretical Isolation Performance . 142 7.4 Metamaterial Insulator Design, Fabrication, and Measurement 146 7.5 Improving Isolation Bandwidth . 148 7.6 Chapter Conclusions . 149 8 Metamaterial Insulator Enabled Superdirective Array . 152 8.1 Chapter Introduction . 152 8.2 Motivation and Background . 153 8.2.1 Superdirectivity . 154 8.2.2 Patch Coupling . 155 8.2.3 Sensitivity Factor . 155 8.2.4 Scan Blindness . 157 8.3 Design for Superdirective Beam-Forming . 158 8.3.1 Single Element . 158 8.3.2 Linear Array . 159 8.4 Array Measurement . 163 8.4.1 Comment on the choice of excitation coe±cients . 164 8.5 Limits of Superdirectivity . 165 8.5.1 E±ciency . 165 8.6 Chapter Conclusions . 167 9 Conclusion . 169 9.1 Summary of Results . 169 9.2 Future Work . 172 9.3 Closing Thoughts . 172 APPENDIX .................................... 173 BIBLIOGRAPHY ................................ 177 vii LIST OF TABLES Table 2.1 Diamagnetic Materials . 30 2.2 Paramagnetic Materials . 30 2.3 Ferromagnetic Materials . 31 2.4 AntiFerromagnetic Materials . 32 2.5 Impedance Matched Material Embedded Four-Point Antenna . 42 4.1 Teflon Measurement . 80 4.2 Measured Permittivity and Permeability of Materials . 103 4.3 Measured Loss Factors of Aluminum-Oxide . 103 5.1 Antenna Parameters . 117 5.2 Miniaturization and E±ciency . 117 viii LIST OF FIGURES Figure 1.1 Incomplete magnetic spin cancelation in magnetite (F e3O4) resulting in a net magnetism . 6 1.2 Probe Fed Microstrip Patch Antenna on a High Permittivity Substrate ²r = 25:0 tan±e=0.001. 8 1.3 The Impedance bandwidth of probe Fed Microstrip Patch Antenna on a High Permittivity Substrate ²r = 25:0 is 0.64% and exhibits a low (´=77%) e±ciency. 8 1.4 Radiation Pattern of antenna in Figure 1.2. Notice that the pattern is highly symmetric in E and H planes. 9 1.5 Probe Fed Microstrip Patch Antenna on an Impedance Matched Magneto- Dielectric Substrate ²r = ¹r = 5:0 tan±e = tan±m=0.001. 12 1.6 The Impedance bandwidth of probe Fed Microstrip Patch Antenna on an Impedance Matched Magneto-Dielectric Substrate ²r = ¹r = 5:0 is 7.94% and exhibits a high (´=99%) e±ciency. 13 1.7 Radiation Pattern of antenna in Figure 1.5. 13 1.8 High Permittivity Dielectric Resonator Antenna (Lx=Ly=0.15¸0=26.67mm, Lz=0.091¸0=6.67mm) ²r = 25:0, ¹r = 1:0 tan±e=0.001,tan±m=0. 14 1.9 The Impedance bandwidth of probe Fed High Permittivity DRA ²r = 25:0 is 2.75% and exhibits a low (´=77%) e±ciency. 15 1.10 Radiation Pattern of DRA in Figure 1.8. 15 1.11 Magneto-Dielectric Resonator Antenna (Lx=Ly=0.15¸0=26.67mm, Lz=0.091¸0 =6.67mm) ²r = 5:0, ¹r = 5:0 tan±e=tan±m=0.001 . 16 1.12 The Impedance bandwidth of probe Magneto-Delectric Resonator An- tenna (²r = 5:0,¹u = 5:0) is 12.08% . 16 1.13 Radiation Pattern of MDRA in Figure 1.11. 17 1.14 A 'woodpile' structure of permeable (²r=1,¹r=16) and dielectric (²r=16,¹r=1) materials stacked in alternation to achieve an electromagnetic band- gap phenomenon. 18 1.15 Transmission through a dielectric-air woodpile, a permeable-air wood- pile, and a dielectric-permeable woodpile. 19 ix 2.1 The permeability of natural materials is caused by either the orbital or electron spin magnetic moment. Of the two, the electronic spin magnetic moment is much stronger and when present and uncanceled is the source of observable magnetic properties. 29 2.2 The Spin Magnetic Moment of Diamagnetic materials with no applied ¯eld and in the presence of an externally applied magnetic ¯eld. 30 2.3 The Spin Magnetic Moment of Paramagnetic materials in with no ap- plied ¯eld and in the presence of an externally applied magnetic ¯eld.