Graduation Year

2010

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Thomas Weller, Ph.D.

Keywords

Complex impedance, Reflection detector, Vector sensor, Phase mixing, Microstrip, Permittivity, Microwave, Wilkinson power divider, Vector addition

Abstract

In the field of applied electromagnetics, there is always a need to create new methods for electrical characterization of materials, systems, devices, etc. Many applications need small and/or inexpensive equipment in performing these characterizations. The current method for making measurements of electrical properties at frequencies above 300 MHz, the transmission/reflection method, has severe limitations in these areas due large size and high price of the necessary equipment for making them. Therefore, presented herein is the conceptualization, design and analysis of a complex reflection coefficient detector which is relatively small, lightweight, and inexpensive. A reflection coefficient detector is a device designed to isolate and compare a driving signal against a reflected signal. The reflection of the second signal is caused by a mismatch between the device's output impedance and a load's input impedance. By comparing the driving, or transmitted, signal and the reflected signal, the reflection coefficient at the boundary can be calculated. This coefficient can be used to calculate a load's input impedance, or a material's permittivity when combined with an attached probe's characteristics. The reflection coefficient detector presented is built using microstrip and surface mount components. This makes the device comparably cheap. Its design is based upon five Wilkinson Power Dividers which lends itself to be scaled down for implementation in on-chip, and other micro- and nano- scale systems.

The accuracy and functionality of the device will be demonstrated through the use of S-Parameters measurements and CAD simulations. Through this, it will be shown that the device is a practical form of making measurements in applications which are otherwise restricted to certain limitations. In closing, applications, alternative designs and future advancements of the complex reflection coefficient detector will be discussed.

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