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Title:Analysis and design of electrically small, circularly polarized cylindrical microstrip antennas
Author(s):Herting, Brian
Director of Research:Bernhard, Jennifer T.
Doctoral Committee Chair(s):Bernhard, Jennifer T.
Doctoral Committee Member(s):Cangellaris, Andreas C.; Franke, Steven J.; Gong, Songbin
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Global Positioning System (GPS)
Abstract:Small unmanned aerial system (UAS) and smart missile and munitions platforms rely on GPS for accurate position, velocity and time (PVT) information. These platforms have significant aerodynamic and space constraints that require innovative conformal GPS antenna solutions. Microstrip antennas are well suited for this type of application due to their inherently low profile package and ability to conform to the shape of a given platform. Since their inception over four decades ago, a significant body of literature has been compiled on the analysis of microstrip antennas. However, most of that research has focused on the development of analytical models and techniques for reducing the size, extending the bandwidth and achieving circular polarization for planar embodiments. Conformal microstrip antennas, on the other hand, have a much more limited body of literature spanning the last three decades. The conformal microstrip antenna literature has focused on the efficient analysis of the singly curved conformal microstrip antenna (SC-CMA), with most published results for single linear polarization and microstrip antennas that conform to cylinders with electrically large radii (i.e., kb > 1, where k is the free space propagation constant and b is the bend radius of the patch metal). This research expands the knowledge of the SC-CMA by investigating the use of a cylindrical rectangular microstrip antenna (CRMA) mounted on an electrically small radius (i.e., kb < 1) cylinder for the purpose of radiating a circularly polarized field. A full-wave 3D analysis of the CRMA TM01 (axial) and TM10 (circumferential) modes was conducted in Ansys HFSS. It was discovered that the input impedance bandwidth of the CRMA TM01 mode more than doubled, while that of the TM10 mode remained virtually unchanged, as the cylinder radius was decreased from infinite, planar, to approximately 0.15 free space wavelengths. In addition, the resonant frequency of the CRMA TM10 mode steadily increased by 3 to 5 percent, while that of the TM01 mode remained virtually unchanged, as the cylinder radius was decreased to 0.15 free space wavelengths. The performance trends of the CRMA as a function of patch metal bend radius were incorporated into the planar microstrip transmission line model (TLM) through modification of the radiating slot normalized length and width. The newly developed CRMA TLM and Ansys HFSS models were validated via measurement of a microstrip line edge fed CRMA. The input impedance bandwidth and resonant frequency of the models differed by less than 0.25% and 3.0%, respectively, from the measured results. The validated CRMA TLM and Ansys HFSS models were used to successfully design a circularly polarized CRMA GPS antenna that met most of the requirements for a small munitions application.
Issue Date:2014-05-30
Rights Information:Copyright 2014 Brian Herting
Date Available in IDEALS:2014-05-30
Date Deposited:2014-05

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