Uniaxial Metamaterials For Microwave Far-Field Collimating Lenses

Open Access
Author:
Turpin, Jeremiah Paul
Graduate Program:
Electrical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Douglas Henry Werner, Thesis Advisor
Keywords:
  • split-ring resonator
  • crossed-dipole antenna
  • metamaterials
Abstract:
The ability to control and manipulate nature and natural phenomena for the solution of practical problems and invention of new tools and technologies has long been a goal of science and engineering. The development of metamaterials exemplifies this pursuit; metamaterial devices, such as materials with a negative index of refraction (NIM) where light `travels' backwards or low-index media where the effective phase velocity exceeds the speed of light, allow interactions with electromagnetic fields in ways unavailable to devices constructed from conventional materials. These properties are used to improve the operation of existing systems and also allow the creation of entirely new optical and electromagnetic devices. Thin slabs composed of negative-index materials, for example, can be used as near-field imaging lenses that can resolve details in the structure being imaged that are smaller than a wavelength in the medium. Metamaterials research is being performed for all regions of the electromagnetic spectrum, from applications in the LF to Microwave, IR, and optical devices. Metamaterials are useful for the improvement of antenna and radiation characteristics, with the capability to exert precise control over the behavior of the electromagnetic field within a region. This thesis describes the development of a microwave metamaterial for the implementation of a far-field collimating flat lens for use with a crossed-dipole antenna. The lens must be constructed from a material with an index of refraction that is nearly zero, a property that does not exist in natural materials. Thus, a metamaterial is required. The design and selection of appropriate unit cell structures are described, along with descriptions of unit cells that were tested and found to be inadequate. Like most microwave metamaterials, the lens uses printed circuit board (PCB) technology for straightforward fabrication and implementation. The final metamaterial design was simulated as a finite lens to confirm correct operation; the metamaterial lens improves the gain of the original crossed-dipole antenna by 6dB, without excessive return loss or absorption loss in the lens.