THESIS
2016
ix, 147 pages : illustrations ; 30 cm
Abstract
Electromagnetic metamaterial is composites consisting of sub-wavelength structures
designed to exhibit particular responses to an incident electromagnetic wave. In general, the
electromagnetic metamaterial is at wavelength scale or sub-wavelength scale and these
metameterial are applicable for high frequencies applications which fall into range from 10 GHz
to 20 GHz. The application of metamaterial for sub-GHz application is little discussed in the past
decades. In this thesis, by incorporating novel structures (like 3D SRR (split ring resonator)) and
new loading materials (like ferrite composite film), the unit cell size of metamaterial has been
successfully scaled down. Small-scale unit cell allows electromagnetic metamaterial to have far
greater flexibility in various applica...[
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Electromagnetic metamaterial is composites consisting of sub-wavelength structures
designed to exhibit particular responses to an incident electromagnetic wave. In general, the
electromagnetic metamaterial is at wavelength scale or sub-wavelength scale and these
metameterial are applicable for high frequencies applications which fall into range from 10 GHz
to 20 GHz. The application of metamaterial for sub-GHz application is little discussed in the past
decades. In this thesis, by incorporating novel structures (like 3D SRR (split ring resonator)) and
new loading materials (like ferrite composite film), the unit cell size of metamaterial has been
successfully scaled down. Small-scale unit cell allows electromagnetic metamaterial to have far
greater flexibility in various applications. This thesis describes the design, mechanism and
development of low profile, low frequency metamaterial for sub-GHz microwave applications.
To offer a better understanding of electromagnetic metamaterial, we firstly examines those
traditional types of electromagnetic metamaterial including: electromagnetic band gap (“EBG”),
frequency selective surface (“FSS”), and negative index material (“NIM”). Based on review on
traditional designs, we described several novel metamaterial designs, among which we
demonstrated a mushroom-like metamaterial, a novel 3D split ring resonator (“3D SRR”) design,
and ferrite composite film loaded metamaterial. Both analytical and numerical simulation models
are used to analyze this innovative metamaterial. The simulation and preliminary measurement
results demonstrate the metamaterial developed in this thesis can significantly reduce the
resonant frequency of metamaterial. In the meantime, these novel structures also demonstrate the
reduced the size of unit cells.
Then, the bulk material property of the metamaterial is retrieved from the unit cell. The
retrieval methodology is introduced, which is an effective medium model for the metamaterial.
The bulk material properties could be retrieved from the scattered parameters, S11 and S21. The
retrieved material property clearly shows that the metamaterial exhibit both negative permittivity
and permeability at certain frequency, which means the refraction index at these frequencies is
negative. The bulk material simulation shows that the metamaterial could be used as
electromagnetic flat lens.
By incorporating this structure, low profile sub-GHz metamaterial is completely achievable
for various real life applications. The second half of this thesis demonstrates the vast applications
of these metamaterial, especially for sub-GHz microwave applications such as RFID (Radio
Frequency Identification). Four kinds of metamaterials are used for this application, the
mushroom-like metamaterial as a reflector, the single unit cell metamaterial as a RFID tag, the
3D SRR (Split Ring Resonator) as a flat lens, and the metamaterial surface antenna. These
measurement results showed that the incorporation of metamaterial could significantly improve
the performance of RFID device in various applications including some problematic
deployments such as in metallic environment.
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