Experimental investigation of new inductor topologies

Date of Award

2016

Degree Name

Ph.D. in Electrical Engineering

Department

Department of Electrical and Computer Engineering

Advisor/Chair

Advisor: Guru Subramanyam

Abstract

Inductors have been investigated and used extensively in analog circuits and digital circuits over 200 years. This dissertation presents a 3D inductor which can efficiently work with a high Q variable capacitor (varactor), and two types of tunable inductors using vanadium dioxide (VO₂) as phase control material. There are three different 3D inductor models that are designed and verified using electromagnetic simulation tools, and applied in a resonator with a voltage tunable ferroelectric thin-film barium strontium titanate (BST) varactor. The resonator combining the 3D inductors and BST thin film varactor is verified for the first time. Two types of tunable inductors are designed using VO₂ thin films which exhibit metal-to-insulator (MIT) phase transition characteristics above a transition temperature. A VO₂-based integrated actuator, which has two-way displacements, is designed and used in the first tunable inductor design. The integrated actuator moves a Nickel layer, which has a high permeability (̃100), over a planar coil inductor to tune the overall inductance. Simulation results show a 27% tuning range through applied displacement variation in the simulator. The second tunable inductor design uses a VO₂ thin films as series switches in the devices. One configuration uses a short VO₂ bar as a circuit switch and the other uses VO₂ to replace the full spiral coil inductor. The total inductance of the circuit tunes when the VO₂ changes from insulating to conducting phase above the transition temperature. The experimental results show 32% inductance variation through applied temperature variation (25°C - 100°C) in the devices. The simplified fabrication process of the second tunable inductor exhibits potential for portable and adaptive communication systems. Two configurations of multi-tap inductors are also designed such that the inductance of the device changes when the probe is moved between the output ports. A strong match between the VO₂ based devices and the Au based devices reveal that we are able to produce high quality VO₂ thin films. The VO₂ thin film has never been utilized in electrical application such as inductors before this research.

Keywords

Electric inductors Design and construction, Vanadium compounds Properties, Electric resonators, Varactors, Electrical Engineering, 3D inductor, resonator, barium strontium titanate, tunable inductor, vanadium dioxide

Rights Statement

Copyright © 2016, author

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