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									Table of Contents




1. Introduction.............................................................................................. 1
2. Survey of Helical Antennas...................................................................... 4
  2.1 Introduction............................................................................................................ 4
  2.2 Modes of Operation................................................................................................ 5
     2.2.1 Transmission Modes ........................................................................................ 5
     2.2.2 Radiation Modes .............................................................................................. 5
       2.2.2.1 Normal mode ............................................................................................. 7
       2.2.2.2 Axial mode ................................................................................................ 7
  2.3 Analysis of Helix ................................................................................................... 9
     2.3.1 Normal-Mode Helix ......................................................................................... 9
     2.3.2 Axial-Mode Helix .......................................................................................... 10
     2.3.3 Empirical Relations for Radiation Properties of Axial-Mode Helix................. 13
     2.3.4 Optimum Performance of Helix...................................................................... 15
  2.4 Modified Helices.................................................................................................. 21
     2.4.1 Helical Antenna with Tapered End................................................................. 21
     2.4.2 Printed Resonant Quadrifilar Helix................................................................. 21
     2.4.3 Stub-Loaded Helix ......................................................................................... 21
     2.4.4 Monopole-Helix Antenna............................................................................... 22
3. Spherical Helices ....................................................................................26
  3.1 Geometry and Parameters of the Spherical Helix.................................................. 26
     3.1.1 Full Spherical and Truncated Geometries ....................................................... 28
     3.1.2 Hemispherical Helix....................................................................................... 29
  3.2 Basic Radiation Properties of Spherical Helix ...................................................... 31



Table of Contents                                                                                                            iv
     3.2.1 Radiation Pattern............................................................................................ 31
     3.2.2 Polarization.................................................................................................... 32
     3.2.3 Bandwidth...................................................................................................... 32
     3.2.4 Input Impedance............................................................................................. 32
4. Numerical Analysis of Spherical Helical Antennas .................................33
  4.1 Electromagnetic Surface Patch Code.................................................................... 33
  4.2 Calculation of Directivity and Axial Ratio............................................................ 34
     4.2.1 Directivity...................................................................................................... 34
     4.2.2 Axial Ratio..................................................................................................... 35
  4.3 Numerical Analysis of Spherical Helices.............................................................. 36
     4.3.1 Spherical and Truncated Spherical Helices..................................................... 36
     4.3.1.1 Truncated Spherical Helices with N = 10 .................................................... 37
     4.3.1.2 Truncated spherical Helices with N = 4 and N = 7 .................................... 37
     4.3.2 Double Spherical Helix .................................................................................. 43
  4.4 Hemispherical Helix............................................................................................. 47
     4.4.1Optimum Design............................................................................................. 47
     4.4.2 Radiation Properties ....................................................................................... 49
     4.4.3 Frequency Scaling.......................................................................................... 53
5. Experimental Results ..............................................................................57
  5.1 Fabrication of Prototype Spherical Helices ........................................................... 57
  5.2 Measurement Results ........................................................................................... 58
     5.2.1 Measurement of the Double Spherical Helix................................................... 59
     5.2.2 Measurement of the 4.5-Turn Hemispherical Helix ........................................ 59
  5.3 Measurement of Axial Ratio................................................................................. 62
6. Concluding Remarks and Recommendations for Future Work................64
  6.1 Summary of Results ............................................................................................. 64
  6.2 Recommemdations for Future Work..................................................................... 66
References ..................................................................................................67
Appendix A. Subroutine WGEOM for the Double Spherical Helix.............69
Appendix B. Subroutine WGEOM for the Hemispherical Helix .................73


Table of Contents                                                                                                            v
Appendix C. Computed Radiation Patterns and Axial Ratios for the
                     Hemispherical Helix.............................................................76
Appendix D. Measured Far-Field Patterns of Hemispherical Helix.............85
Vita.............................................................................................................94




Table of Contents                                                                                                vi

								
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