Yujia Peng

Date of Award

2016

Document Type

Open Access Dissertation

Department

Electrical Engineering

Sub-Department

College of Engineering and Computing

First Advisor

Guoan Wang

Abstract

There is an increasing demand for reliable sensor system capable of remote sensing and measuring interesting data. Although large communication range can be achieved, active wireless communication systems are still suboptimal in longtime applications due to their harmful battery supply. Inductively coupled passive devices, with the advantages in safe long-term implanting, structural simplicity, small fabrication footprint and low-cost production, are preferred in chronic monitoring, but little work has been done to optimize the performance of these systems, especially under some design constraints.

The model and optimization of an inductively coupled wireless pressure sensor system is presented in this dissertation. With MEMS and semiconductor technology, the pressure sensor is designed as a miniaturized LC resonant circuit operating in 402MHz within a small footprint of 3.2 mm by 3.2 mm. An optimization approach is conducted to analyze inductive as well as pressure sensitivity. With mutually dependent geometrical parameters and performance related RF characteristics considered in the full optimization of the system, the applied design of this experiment method can reduce the large number of combined groups of values in fractional simulations with a focus on a few performance related factors. The second task of this research is to improve the limited working range of the sensing system. A half-active wireless communication system is studied as an alternative solution to this problem. Wireless power harvesting circuits and auxiliarydata-acquisition circuits are integrated in the system for long distance communication. However, physical size of system also becomes large with the added circuits. The challenges of designing compact wireless communication system are proposed to be solved in this dissertation.

With the requirements of multi-band and multi-function in wireless communication systems with improved performance and reduced size, development of tunable miniaturized RF components are a promising solution to fulfill the trend. Many technologies have been investigated and applied to develop tunable devices including MEMS and semiconductor varactors, ferroelectric capacitors, and magnetically tunable inductors with ferromagnetic materials, etc. However, the tunability of reported devices using the above technologies is directly dependent on the individual design configurations, which limits the design flexibility and broader application. A unique solution is to design arbitrary tunable RF components using an engineered substrate with an embedded patterned permalloy (Py) thin film which was developed for the first time in this dissertation. With high and current-dependent permeability, an engineered substrate embedded with Py thin film is a promising and flexible approach to design compact frequency-agile RF devices. Py thin film is patterned into slim bars on an engineered substrate to improve its ferromagnetic resonant frequency (FMR) for RF and mmwave applications. Miniaturized RF components are first developed with the proposed engineered magneto-dielectric substrate in this dissertation. Permeability tunable smart substrate was also developed by integrating an array of DC bias lines to provide a tuning path of Py patterns. The design principles and factors affecting the characteristics of the engineered substrate have been fully analyzed. Design efficacy of the developed tunable substrate has been demonstrated with implemented components including a patch antenna, a phase shifter, a bandpass filter, and a three-port bandpass filtering balun. The proposed engineered substrate is feasible in implementing arbitrary RF and microwave devices with improved tuning capability and design flexibility.

Rights

© 2016, Yujia Peng

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