The Pennsylvania State University The Graduate School College of Engineering NOVEL CIRCULAR RING PHASED ARRAY ANTENNA DESIGN A Thesis in Electrical Engineering by Kunj Desai  2014 Kunj Desai Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science December 2014 The thesis of Kunj Desai was reviewed and approved* by the following: James K. Breakall Professor of Electrical Engineering Thesis Advisor Julio Urbina Associate Professor of Electrical Engineering Kultegin Aydin Professor of Electrical Engineering Head of the Department *Signatures are on file in the Graduate School iii ABSTRACT The aim of this thesis was to develop a novel design for a phased array antenna especially considering a circular geometry at 50 MHz, while an Optimized Wideband Antenna Yagi (OWA Yagi) was used as an antenna array element. Examples of successful simulation results have been shown which include optimization of element spacing and radiation pattern analysis. For radar systems, this design gives a better way to implement the antenna array via a series of simulations. The electromagnetic solver FEKO and the Phased Array Toolbox of MATLAB from Mathworks have been used extensively to generate, optimize, and validate the results as per expectation. Along with this novel technique, this thesis also provides the background of the FEKO code and the newly developed MATLAB Phased Array Toolbox. A separate section has been allocated to display the results of FEKO and MATLAB. Analytic discussion of the results is provided after the graphical display of the modeling and simulation, where the effect of array element spacing on the overall gain and radiation pattern is discussed. To minimize the effect of mutual coupling between antenna array elements, triangular lattices are incorporated. The approximate cost of each Yagi has also been given. At the end of the thesis, a brief summary of this current work and the future tasks are discussed. iv TABLE OF CONTENTS List of Figures .......................................................................................................................... vi List of Tables ........................................................................................................................... x Acknowledgements .................................................................................................................. xi Chapter 1 Introduction ............................................................................................................. 1 1.1 Background ................................................................................................................ 2 1.1.1 EAR (Equatorial Atmosphere Radar) Indonesia-2001 .................................... 3 1.1.2 MU (Middle and Upper Atmosphere) Radar, Japan-1984 .............................. 7 1.2 Antenna Array Basics ................................................................................................ 10 1.2.1 Different types of phased arrays ...................................................................... 10 1.2.2 Applications of Phased Arrays ........................................................................ 11 1.2.3 Basic Array Concept ....................................................................................... 11 1.2.4 Properties Liner arrays .................................................................................... 16 1.3 Problem Statement ..................................................................................................... 20 1.4 Scope of the Study ..................................................................................................... 20 Chapter 2 Numerical Analysis Techniques ............................................................................. 22 2.1 Array Factor for Circular Array ................................................................................. 22 2.2 MATLAB Phased Array Tool Box ............................................................................ 24 2.2.1 Key Features .................................................................................................... 25 2.2.2 Phased Array Design and Analysis ................................................................. 25 2.3 FEKO ......................................................................................................................... 32 2.3.1 What is FEKO? ............................................................................................... 33 2.3.2 FEKO GUI Features ........................................................................................ 34 2.3.3 Excitations ....................................................................................................... 34 2.3.4 Post-Processing Features ................................................................................. 34 2.3.5 Numerical Methods Used in FEKO and Antenna Analysis ............................ 35 2.4 Methods of Moments (MoM) ..................................................................................... 40 Chapter 3 Antenna Modelling and Results ............................................................................. 42 3.1 Optimized Wideband Antenna (OWA) Yagi Design ................................................. 42 3.2 Analysis and Discussion ............................................................................................ 48 3.2.1 Mutual coupling .............................................................................................. 48 3.2.2 Discussion on phased array deployment based on triangular lattice in FEKO................................................................................................................ 49 3.3 FEKO Results ............................................................................................................ 55 3.3.1 Element spacing 0.7 λ ..................................................................................... 56 3.3.2 Element spacing 0.75 λ ................................................................................... 62 3.3.3 Element spacing 0.8 λ ..................................................................................... 68 3.3.4 Element spacing 0.9 λ ..................................................................................... 75 3.3.5 Element spacing 1.0 λ ..................................................................................... 83 3.4 MATLAB Array Modelling Results .......................................................................... 92 v Chapter 4 Conclusions ............................................................................................................ 104 4.1 Result Discussion and Summary ................................................................................ 104 4.2 Future Work ............................................................................................................... 106 REFERENCES ........................................................................................................................ 108 APPENDIX A- FEKO additional information ........................................................................ 110 APPENDIX B- MATLAB additional information .................................................................. 111 vi LIST OF FIGURES Figure 1-1. Basic radar system ................................................................................................. 2 Figure 1-2. Schematic block diagram of the Equatorial Atmosphere Radar (EAR) system .... 4 Figure 1-3. (a) A view of EAR, (b) Three-element Yagi antennas are shown, each with a transmitter-receiver module (TR modules) mounted, near the ground, on the pole...... 5 Figure 1-4. The EAR antenna array, each dot represents the location of a three-element Yagi antenna and TR module. .......................................................................................... 7 Figure 1-5. Geometry of a two-element array positioned along the z-axis: (a) Two infinite dipoles, (b) Far field observation ..................................................................................... 13 Figure 1-6. Element, array factor, and total field patterns of a two-element array of infinitesimal horizontal dipoles with identical phase excitation (d=λ/4 with no phase separation) ........................................................................................................................ 13 Figure 1-7. Three-dimensional amplitude patterns for broadside, and broadside/end-fire arrays, (a) broadside pattern (b) endfire pattern ............................................................... 15 Figure 1-8. Display of phased array response characteristics vs direction, showing multiple antennas combined to enhance radiation and shape pattern .............................. 17 Figure 1-9. Effect on properties of linear array by changing, (a) number of elements (b) separating distance (c) separation distance in endfire case (d) array type from broadside to endfire .......................................................................................................... 19 Figure 2-1. The array factor calculation for circular planar array ............................................ 23 Figure 2-2. Few array geometries available in MATLAB toolbox .......................................... 27 Figure 2-3. 3D beam pattern for a 10 x 10 uniform rectangular array ..................................... 28 Figure 2-4. MATLAB phased array toolbox user interface ..................................................... 29 Figure 2-5. MATLAB phased array toolbox user interface ..................................................... 30 Figure 2-6. MATLAB phased array toolbox result display ..................................................... 31 Figure 2-7. Linear microstrip array with squinted main beam................................................. 37 Figure 2-8. Microstrip array with squinted beam: a) Periodic boundary analysis of large array_unit cell, b) Periodic boundary analysis of large arrays_3D radiation pattern of array ................................................................................................................................. 38 Figure 2-9. Radiation pattern of a microstrip patch array antenna .......................................... 38 vii Figure 2-10. Characterization of a horn-fed reflector antenna ................................................. 39 Figure 3-1. Optimized Wideband Antenna Yagi simulation model ........................................ 44 Figure 3-2. Realistic model of OWA Yagi .............................................................................. 44 Figure 3-3. Optimized Wideband Antenna (OWA) Yagi optimized for minimum radiation towards the ground, minimum VSWR, and maximum gain from 49 to 51 MHz ................................................................................................................................. 45 Figure 3-4. VSWR of OWA Yagi in Free Space ..................................................................... 45 Figure 3-5. VSWR of the OWA Yagi over average ground which is exact the same as in free space.......................................................................................................................... 46 Figure 3-6. Pattern of OWA Yagi over average ground with the same gain as in free space ................................................................................................................................. 47 Figure 3-7. Array lattice configuration: (a) triangular lattice (b) square lattice ....................... 49 Figure 3-8. Graphical derivation of phase shift ....................................................................... 51 Figure 3-10. Deployment of phased array (zoomed graphical view) ....................................... 53 Figure 3-11. Deployment of phased array (zoomed graphical view) ....................................... 53 Figure 3-12. 3D Pattern Plot – X-axis with beam steering to θ=30° (0.7λ) ............................. 56 Figure 3-13. 3D Polar Plot – X-axis with beam steering to θ=30° (0.7λ) ................................ 57 Figure 3-14. 3D Pattern Plot – Y-axis with beam steering to θ=30° (0.7λ) ............................. 58 Figure 3-15. 3D Polar Plot – Y-axis with beam steering to θ=30° (0.7λ) ................................ 59 Figure 3-16. 3D Pattern Plot – with beam steering to θ=0° (0.7λ) .......................................... 60 Figure 3-17. 3D Polar Plot – X-axis with beam steering to θ=0° (0.7λ) .................................. 61 Figure 3-18. 3D Pattern Plot – with beam steering to θ=0° (0.75λ) ........................................ 62 Figure 3-19. 3D Polar Plot – X-axis with beam steering to θ=0° (0.75λ) ................................ 63 Figure 3-20. 3D Pattern Plot – Y-axis with beam steering to θ=30° (0.75λ) ........................... 64 Figure 3-21. 3D Polar Plot – Y-axis with beam steering to θ=30° (0.75λ) .............................. 65 Figure 3-22. 3D Pattern Plot – X-axis with beam steering to θ=30° (0.75λ) ........................... 66 Figure 3-23. 3D Polar Plot – X-axis with beam steering to θ=30° (0.75λ) .............................. 67 viii Figure 3-24. 3D Pattern Plot – X-axis with beam steering to θ=30° (0.8λ) ............................. 68 Figure 3-25. 3D Pattern Plot –Top down view- X-axis with beam steering to θ=30° (0.8λ) .. 69 Figure 3-26. 3D Polar Plot – X-axis with beam steering to θ=30° (0.8λ) ................................ 70 Figure 3-27. 3D Pattern Plot – Y-axis with beam steering to θ=30° (0.8λ) ............................. 71 Figure 3-28. 3D Polar Plot – Y-axis with beam steering to θ=30° (0.8λ) ................................ 72 Figure 3-29. 3D Pattern Plot – X-axis with beam steering to θ=0° (0.8λ) ............................... 73 Figure 3-30. 3D Polar Plot – X-axis with beam steering to θ=0° (0.8λ) .................................. 74 Figure 3-31. 3D Pattern Plot – X-axis with beam steering to θ=30° (0.9λ) ............................. 75 Figure 3-32. 3D Pattern Plot – top down view - X-axis with beam steering to θ=30° (0.9λ) ................................................................................................................................ 76 Figure 3-33. 3D Polar Plot – X-axis with beam steering to θ=30° (0.9λ) ................................ 77 Figure 3-34. 3D Pattern Plot – with beam steering to θ=0° (0.9λ) .......................................... 78 Figure 3-35. 3D Polar Plot – X-axis with beam steering to θ=00° (0.9λ) ................................ 79 Figure 3-36. 3D Pattern Plot – Y-axis with beam steering to θ=30° (0.9λ) ............................. 80 Figure 3-37. 3D Pattern Plot – top down view – Y-axis with beam steering to θ=30° (0.9λ) ................................................................................................................................ 81 Figure 3-38. 3D Polar Plot – Y-axis with beam steering to θ=30° (0.9λ) ................................ 82 Figure 3-39. 3D Pattern Plot – X-axis with beam steering to θ=30° (1.0λ) ............................. 83 Figure 3-40. 3D Pattern Plot – top down view - X-axis with beam steering to θ=30° (1.0λ) ................................................................................................................................ 84 Figure 3-41. 3D Pattern Plot – another view - X-axis with beam steering to θ=30° (1.0λ) ..... 85 Figure 3-42. 3D Polar Plot – X-axis with beam steering to θ=30° (1.0λ) ................................ 86 Figure 3-43. 3D Pattern Plot – Beam steering to θ=0° (1.0λ) .................................................. 87 Figure 3-44. 3D Polar Plot – Beam steering to θ=0° (1.0λ) ..................................................... 88 Figure 3-45. 3D Pattern Plot – Y-axis with beam steering to θ=30° (1.0λ) ............................. 89 Figure 3-46. 3D Pattern Plot – top down view - Y-axis with beam steering to θ=30° (1.0λ) ................................................................................................................................ 90 ix Figure 3-47. 3D Polar Plot – Y-axis with beam steering to θ=30° (1.0λ) ................................ 91 Figure 3-48. 6 by 6 planar 1λ spacing rectangular lattice array with beam slewed 30 degrees from the zenith .................................................................................................... 93 Figure 3-49. 6 by 6 planar 1λ spacing rectangular lattice array with beam slewed 30 degrees from the zenith (top-down view) ........................................................................ 93 Figure 3-50. 6 by 6 planar 1λ spacing rectangular lattice array with beam slewed 30 degrees from the zenith (u-v space) ................................................................................. 94 Figure 3-51. 7 by 8 planar 1λ spacing triangular lattice array with beam slewed 30 degrees from the zenith in Y-axis .................................................................................... 94 Figure 3-52. 7 by 8 planar 1.0λ spacing triangular lattice array with beam slewed 30 degrees from the zenith in the Y-axis (u-v space) ............................................................ 95 Figure 3-53. 7 by 8 planar 1λ spacing triangular lattice array with beam slewed 30 degrees from the zenith in the X-axis (top-down view) ................................................... 96 Figure 3-54. 7 by 8 planar 1λ spacing triangular lattice array with beam slewed 30 degrees from the zenith in the X-axis (u-v space) ............................................................ 96 Figure 3-55. Circular aperture configuration with a triangular lattice between the 473 elements total ................................................................................................................... 97 Figure 3-56. Circular aperture triangular lattice array with 0.7λ spacing with the beam slewed 30 degrees from the zenith and 473 elements total .............................................. 98 Figure 3-57. Circular aperture triangular lattice array with 0.75λ spacing with the beam slewed 30 degrees from the zenith and 473 elements total .............................................. 99 Figure 3-58. Circular aperture triangular lattice array with 0.8λ spacing with the beam slewed 30 degrees from the zenith and 473 elements total .............................................. 100 Figure 3-59. Circular aperture triangular lattice array with 0.9λ spacing with the beam slewed 30 degrees from the zenith and 473 elements total .............................................. 101 Figure 3-60. Circular aperture triangular lattice array with 1.0λ spacing with the beam slewed 30 degrees from the zenith and 473 elements total .............................................. 102 x LIST OF TABLES Table 1-1. EAR specifications ................................................................................................. 6 Table 1-2. MU Radar specification .......................................................................................... 9 Table 2-1. FEKO and its diverse application ........................................................................... 33 Table 3-1. Results for Linear phased array (OWA-Yagi) ........................................................ 54 Table 3-2. Results for Linear phased array (OWA-Yagi) ........................................................ 55