A Switchable Magnetic Low-index Metamaterial for use in a Dynamically Reconfigurable Beam-scanning Lens Antenna with a Single Feed

Open Access
Author:
Turpin, Jeremiah Paul
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
October 01, 2014
Committee Members:
  • Douglas Henry Werner, Dissertation Advisor
  • Douglas Henry Werner, Committee Chair
  • Pingjuan Li Werner, Committee Member
  • Victor P Pasko, Committee Member
  • Douglas Edward Wolfe, Committee Member
Keywords:
  • electromagnetics
  • antennas
  • reconfigurable pattern antennas
  • metamaterial
  • Transformation Optics
Abstract:
Metamaterials and Transformation Optics (TO) have been used to design and implement many novel electromagnetic devices that can achieve effects not possible using conventional materials. Compact high-gain antennas are one of the more popular and successful emerging applications for the new TO and metamaterial design approaches. This dissertation details an extension of uniaxial near-zero index metamaterial lenses through the incorporation of a tunable or reconfigurable metamaterial as a replacement for the static metamaterial of the original antenna. A design is presented for a beam-scanning TO lens that allows an arbitrary number of beams at controlled magnitudes to be dynamically synthesized from a single omnidirectional source, unlike the equivalent antenna constructed using an array. A cylindrical slab of zero-index magnetic metamaterial controls the radiation pattern by altering the effective shape of the lens through switching of selected regions 'off' to emulate free-space conditions. A design for a switchable metamaterial is presented that allows for digital control over its bulk properties, from near-zero-index to near-free-space at the targeted operational frequency. Extensive modeling and simulations were performed for the design of the lens and metamaterial and during the analysis of measurement results. Initial prototypes of the tunable metamaterial were fabricated and characterized to confirm the original measurements, and the design updated to incorporate the measured data. These measurements were performed using custom test fixtures manufactured specifically for this project. Finally, a simplified prototype lens was manufactured and characterized in an anechoic as a proof-of-concept for the design. This dissertation presents the lens and metamaterial specifications, as well as the design process and considerations that were determined for practical tunable and reconfigurable metamaterials. Although the focus is on the particular example of the beam-scanning reconfigurable antenna, the analysis and modeling methods presented here are applicable to any reconfigurable metamaterial application.