Ultra wideband pulse propagation in dispersive biological tissue : a computational, statistical and experimental study
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The performance of implantable devices in biological media requires consistent coupling between the antenna and the surrounding environment. Electromagnetic losses in biological tissues can degrade antenna performance. This performance loss compounds within biological material due to reflections and dispersions caused by the high variations in dielectric properties from host to host. Variation could be caused by multiple molecular-level interactions that are expressed at the macro level through variations in the complex relative dielectric permittivities of biological tissues. Different concentrations of conducting ions or water content in the tissue could lead to large variations in conductivity and permittivity across tissues. To quantify the effects of these variations in dielectric tissue properties, multiple simulations are performed in which the dielectric properties of tissues are varied ±25% to approximate these molecular changes on the macro scale. These results are compiled into a meta-model using Polynomial Chaos Expansion and Kriging methods to create a computationally efficient statistical model for examining the varying behavior. After examining this behavior, an implantable electric-field probe is calibrated to quantify how changes in the dielectric properties of biological tissue affect the propagation of ultra-wideband electromagnetic pulses. By shielding a monopole antenna with a dielectric sheath, the antenna can exhibit more consistent capacitive coupling to the environment, improving measurements of local electric-field effects in different media. The methods developed herein for calibrating this probe can be applied to implantable antennas to achieve more consistent performance across diverse environmental conditions.
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Introduction -- Background & literature review -- Computational methods & results -- Experimental methods & results -- Conclusions & future work
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Ph.D. (Doctor of Philosophy)