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Title:Modeling and design of near-field antennas with periodic structures
Author(s):Zeng, Yunjia
Director of Research:Jin, Jianming
Doctoral Committee Chair(s):Jin, Jianming
Doctoral Committee Member(s):Bernhard, Jennifer; Schutt-Ainé, José; Gong, Songbin
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Numerical method
Periodic structures
Near field
Magnetic field
Dispersion analysis
Equivalent circuit
Loop antenna
Artificial magnetic conductor
Radio frequency identification
Ultrahigh frequency
Directional antenna
Antenna array
Parasitic array
Abstract:In this dissertation, the one- and two-dimensional periodic structures are modelled and adopted in the design of near-field antennas. First, the discontinuous Galerkin time-domain (DGTD) method is applied to model the scattering from periodic structures. The modelling of dispersive media is incorporated into a three-dimensional DGTD scheme, which is capable of studying plasmonic periodic structures at optical frequencies. Various numerical examples are presented to demonstrate the applications of the proposed algorithm. Second, a new methodology for modelling and characterization of one-dimensional periodic structures with nonstraight geometries is developed. The one-dimensional zero-phase-shift line (ZPSL) is analyzed to obtain its dispersion characteristics. Equivalent circuit models are proposed to characterize the ZPSL structures. A design guideline is developed and demonstrated to enlarge the interrogation zone of a ZPSL loop antenna for near-field wireless systems. Third, the full dispersion characteristics, including phase and attenuation constants, of the ZPSL are analyzed in a loop configuration. Based on the dispersion characteristics, a periodic ZPSL loop antenna with uniformly distributed unit cells is studied, and a nonperiodic ZPSL loop antenna with nonuniformly arranged unit cells is designed for an improved near-field performance. Fourth, a low-profile directional ZPSL loop antenna is proposed by placing an artificial magnetic conductor (AMC) reflector behind a ZPSL grid-loop antenna. The grid-loop configuration is designed such that an enhanced magnetic field distribution can be realized on the electrically large ZPSL loop antenna with a simple feeding network. The AMC reflector with four-arm spiral unit cells is included to achieve a directional field distribution as well as to further increase the magnetic field intensity. Fifth, two low-profile ZPSL loop antennas are proposed to achieve a directional magnetic near-field distribution. The current distributions on the antennas are studied to realize the desired near-field pattern. Besides the directional distribution, both the antennas exhibit enhanced magnetic field intensities in the forward direction. All of the antennas are exemplified as a reader antenna for ultra-high frequency (UHF) near-field radio frequency identification (RFID) systems.
Issue Date:2017-07-09
Rights Information:Copyright 2017 Yunjia Zeng
Date Available in IDEALS:2017-09-29
Date Deposited:2017-08

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