Advisor(s)

Vincent G. Harris

Contributor(s)

Carmine Vittoria, Patanjali V. Parimi

Date of Award

2009

Date Accepted

12-2009

Degree Grantor

Northeastern University

Degree Level

Ph.D.

Department or Academic Unit

College of Engineering, Department of Electrical and Computer Engineering

Keywords

electrical engineering, ferrite, metamaterial, microwave, negative index, tunable

Disciplines

Electrical and Computer Engineering

Abstract

Metamaterials possessing simultaneous negative permittivity and permeability, and hence negative refractive index, have created intense interest since the beginning of this century in fundamental physics, material science, and microwave and optical engineering. The mainstream approach of realizing these properties is to combine metallic plasmonic wires and magnetic ring resonators. These metallic metamaterials can be adapted for different frequency ranges by design of device elements in proportion to targeted wavelengths. However, because the magnetic resonant properties is defined strictly by geometric parameters of the ring structures, these metamaterials suffer from narrow bandwidth and are not at all tunable. Alternatively, ferrite materials show a broad band of negative permeability near the ferromagnetic/ferrimagnetic resonance that can be tuned by a magnetic field in frequency. So there are great opportunities of realizing broad band and tunable negative index metamaterials (NIMs) using ferrites.

This research explores the negative permeability property of ferrite materials and the negative permittivity property of plasmonic metal wires concomitant in frequency to realize tunable negative index metamaterials (TNIMs). Further, these ferrite-based TNIMs were applied to demonstrate microwave devices. Different ferrite materials, including poly and single crystalline yttrium iron garnet (YIG) and scandium doped barium hexaferrite were utilized. Broadband, low loss and tunable NIMs were realized in X-, K-, and Q-band respectively. The minimum insertion loss is ~ 5.7 dB/cm and the maximum dynamic bandwidth is ~ 5 GHz for the K-band waveguide TNIM, ~ 5 dB/cm and ~ 3 GHz for the X-band microstrip TNIM, and -25 dB/cm and ~ 3 GHz for the Q-band waveguide TNIM. Continuous and rapid phase tunability of 160 degree/kOe was realized at 24 GHz for the K-band TNIM, and 70 degree/kOe at 9 GHz for the microstrip TNIM. Large phase tuning was also found in the Q-band TNIM using a hexaferrite. But the insertion loss needs to be reduced for it to be practical.

These demonstrations are the first to implement TNIMs in microwave device applications.

Document Type

Dissertation

Rights Information

copyright 2009

Rights Holder

Peng He


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