Miniaturization of Folded Slot Antennas Through Inductive
Total Page：16
File Type：pdf, Size：1020Kb
MINIATURIZATION OF FOLDED SLOT ANTENNAS THROUGH INDUCTIVE LOADING AND THIN FILM PACKAGING by DAVID A. KARNICK Submitted for the partial fulfillment of requirements for the degree of Master of Science Thesis Adviser: Dr. Christian A. Zorman Department of Electrical Engineering and Computer Science CASE WESTERN RESERVE UNIVERSITY May, 2011 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis of David Karnick candidate for the Master of Science degree*. Christian A Zorman (chair of the committee) Francis Merat Phillip Feng 1/13/11 *We also certify that written approval has been obtained for any proprietary material contained therein. Table of Contents List of Tables ..................................................................................................................... iv List of Figures ..................................................................................................................... v Acknowledgements .......................................................................................................... viii Abstract .............................................................................................................................. ix 1 Introduction ................................................................................................................. 1 1.1 Motivation and Background ................................................................................. 1 1.1.1 Miniaturization of RF Devices through Reactive Loading ........................... 1 1.1.2 Packaging Techniques for RF Devices ......................................................... 5 1.2 Goals..................................................................................................................... 7 2 The Wilkinson Power Divider ..................................................................................... 9 2.1 Inductive Load .................................................................................................... 10 3 Folded Slot Antenna .................................................................................................. 15 3.1 Physical Definitions ........................................................................................... 15 4 Inductive Loading on the FSA................................................................................... 17 4.1 Models and Simulation....................................................................................... 17 4.2 Fabrication .......................................................................................................... 21 4.2.1 Materials ..................................................................................................... 22 4.2.2 Milling Process ........................................................................................... 22 4.2.3 Photolithography Process............................................................................ 26 i 4.2.4 Mounting of Components ........................................................................... 29 4.3 Measurements ..................................................................................................... 30 4.4 Integrated Component Model ............................................................................. 33 5 Capacitive Loading on the FSA................................................................................. 41 5.1 Top-Mounted Capacitors .................................................................................... 41 5.2 Integrated Capacitor Model ................................................................................ 43 6 Inductive and Capacitive Loading in Combination ................................................... 47 6.1 Series vs. Parallel Combination ......................................................................... 47 6.1.1 Parallel Combination .................................................................................. 47 6.1.2 Series Combination ..................................................................................... 48 6.2 LC Fabrication .................................................................................................... 52 6.2.1 Milling Process ........................................................................................... 52 6.2.2 Photolithography Process............................................................................ 52 6.2.3 Mounting of Components ........................................................................... 53 6.3 Measured Results ............................................................................................... 54 7 Sputtered Silicon Carbide as a Packaging Material ................................................... 58 7.1 Wafer Fabrication ............................................................................................... 58 7.1.1 Evaporation of Metals ................................................................................. 59 7.1.2 Sputtering of Silicon Carbide ...................................................................... 59 7.1.3 Etching ........................................................................................................ 60 ii 7.1.4 Patterning .................................................................................................... 60 7.2 Chemical Resistance Tests ................................................................................. 61 7.2.1 Results ......................................................................................................... 63 7.3 Dielectric Constant ............................................................................................. 68 7.4 LC Resonator...................................................................................................... 69 8 Conclusions and Recommendations .......................................................................... 71 APPENDICES .................................................................................................................. 76 APPENDIX A: Mathematica Script for Wilkinson Calculations ................................. 77 Bibliography ..................................................................................................................... 80 iii List of Tables Table 1: Dimensions for FSA with mounted inductors .................................................... 18 Table 2: Milled CPW dimensions for FSA with inductors ............................................... 25 Table 3: Chemically-etched CPW dimensions for FSA with inductors ........................... 28 Table 4: Milled CPW dimensions for FSA with inductors and capacitors ....................... 52 Table 5: Chemically-etched CPW dimensions for FSA with inductors and capacitors ... 53 Table 6: Etch test matrix ................................................................................................... 62 Table 7: Average changes per sample by etch test ........................................................... 67 iv List of Figures Figure 1.1: Two approaches to transmission-line length reduction [1] .............................. 2 Figure 1.2: Magnetic current distribution on a half wavelength and inductively [4] ......... 3 Figure 1.3: (a) Simulated and (b) measured |S11| for antennas without and with capacitors [5] ........................................................................................................................................ 4 Figure 1.4: Effect of loaded capacitor on resonant frequencies of slot antennas [6] .......... 5 Figure 2.1: Schematic for Wilkinson power divider ........................................................... 9 Figure 2.2: Modified Wilkinson schematic with added capacitors................................... 10 Figure 2.3: Modified Wilkinson power divider with added inductors .............................. 11 Figure 2.4: Modified transmission line impedance vs. line length (in wavelengths) ....... 14 Figure 2.5: Load inductance vs. line length (in wavelengths) .......................................... 14 Figure 3.1: Schematic of unloaded folded slot antenna .................................................... 15 Figure 3.2: Radiation pattern of basic FSA ...................................................................... 16 Figure 4.1: Folded slot antenna with side-mounted inductors .......................................... 17 Figure 4.2: S11 vs. Frequency for simulated side-mounted inductors ............................. 19 Figure 4.3: Folded slot antenna with top-mounted inductor ............................................. 20 Figure 4.4: S11 vs. Frequency for simulated top-mounted inductor ................................ 21 Figure 4.5: Contrasted image of mill depth inconsistencies on side slot .......................... 24 Figure 4.6: Contrasted image of mill depth inconsistencies at top of CPW (left side)..... 24 Figure 4.7: Image of mill depth inconsistencies at top of CPW, higher zoom ................. 25 Figure 4.8: Photolithography process [19]........................................................................ 27 Figure 4.9: Images of FSAs created with (a) milling process and (b) photolithography .. 29 Figure 4.10: Image of FSA with mounted inductors ........................................................ 30 v Figure 4.11: S11 vs. Frequency for milled FSAs with side-mount inductors................... 31 Figure 4.12: S11 vs. Frequency for FSAs with side-mounted inductors created using photolithography