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Energy harvesting near the human body using finite-difference time-domain simulations
Lumnitzer, Rachel S.
Lumnitzer, Rachel S.
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2023
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Abstract
The finite-difference time-domain (FDTD) algorithm is a very useful numerical technique used to solve Maxwell's equations in either the time or frequency domain by approximating the derivatives. This work focuses on biomedical applications of the algorithm with and without dispersive media representing human tissues. The use of dispersive media requires adaptations to the FDTD algorithm since the material properties change with frequency. This is a unique challenge faced by today's 5G biomedical applications of FDTD that use human biological tissues. One of the most efficient and powerful ways to apply dispersive media such as human tissues in FDTD is with the Debye model. Once the human tissues are fully characterized accordingly using Debye, a dispersive FDTD formulation can be used to accurately assess the performance of the model.
The goal of this thesis is to characterize the Debye parameters for several human tissues up to 100 GHz and apply them to the FDTD algorithm to evaluate practical 5G biomedical applications. The applications focus on the wireless charging optimization of 5G biomedical devices using dielectric cylinders placed above the human tissues. The device would be installed, for example, on the surface of a patient's wrist. The application is explored in the 2D space as well as 3D space for the same relative model dimensions.
As a first step and quick analysis, a 2D application is developed that uses the traditional FDTD algorithm in the time domain with the dielectric properties of the human tissues. A reflector antenna is included in the 2D analysis to focus the incident wave on the tissue area. Next, a practical 3D application is developed that uses the dispersive FDTD adaptation of the algorithm with the Debye parameters of the human tissues included in the model. The results show approximately 3 to 8 dB of gain in general and at certain positions the gain can reach 10 dB with the use of the optimized dielectric cylinders placed on the first tissue layer. The resulting incident E-field is focused on the surface of the tissue layers. This thesis shows the practical advantages of using the Debye model for human tissues and how to increase the performance of 5G biomedical applications.
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