Date of Award

Fall 2019

Document Type

Open Access Thesis

Department

Electrical Engineering

First Advisor

Mohammod Ali

Abstract

This thesis will investigate whether and how a synthetic metal-magnetic alloy absorbs enough near-field electromagnetic (EM) radiation for heating. Although resistive elements could be used for indirect heating, a wireless radio frequency (RF) method is explored because of its advantages in its non-intrusive nature and its ability to direct or focus energy within a specific area. For our case, the RF heating process relies on the materials ability to absorb sufficient RF energy due to the induced currents. We expect there to be significant surface resistance due to the conductivity and magnetic permeability of the material and thus heat. This ratio between these unknown parameters (σ/µr) are determined to be 1x106 with surface roughness and 2.5x105 without surface roughness. When using a resonant dipole at 2.4 GHz, not all the RF energy absorbed by the material will become heat so an Efficiency Factor (EF) was created to normalize the simulated results to the experimental verification using a well-known material, graphite. The EF was determined to be 1.77% and could be used for the unknown alloy calculations, along with a Spacing Factor (SF) of 14.7% to account for the granular material. For graphite at 5/8

inch from 10 W input power antenna, the temperature rise after 5 minutes was 7.9 ℃.

Similarly, for the granular alloy the temperature rise was 4.5 ℃. A new method of further enhancing the EM energy absorption in material was developed by designing and investigating a split ring resonator (SRR) in simulations which showed the potential to increase the temperature rise in the alloy by a factor of 5.5 due to its inherently resonant nature.

Rights

© 2019, Michael Dillon Lindsay

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