Date of Award

Fall 2004

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

First Advisor

Josse, Fabien

Second Advisor

Jeutter, Dean

Third Advisor

Hossenlopp, Jeanne

Abstract

With the increase in sensor applications to include such things as the liquid detection of bio/chemical warfare agents and environmental testing and monitoring, there is a need for real-time, rapid, and direct detection in liquid environments. Therefore, the primary goal of this work is to extend the use of the guided SH-SAW sensor from a laboratory setting, by making the measurement system portable. The radio frequency (RF) circuit consists of a two port, independent, measurement system for both amplitude and phase detection for a guided SH-SAW sensor. The amplitude is measured by comparing a reference signal to a sensing signal. This is done with the use of a phase shifter, difference amplifier and an envelope detector. The amplitude output is a DC value of the difference between the two signals. The phase is also measured by comparing a reference signal and a sensing signal. The phase detector has a DC output proportional to the phase difference between the two signals. The conclusions suggest that it is possible to construct a RF circuit that is portable, accurate, and can make real-time measurements of a guided SH-SAW device for chemical detection in liquid environments. The designed circuit's reproducibility and repeatability matched the vector network analyzer results within a 95% confidence interval for each of the three trials when detecting ethylbenzene and xylene at concentrations of 10 to 60 ppm. Consequently, the goal of using the circuit to monitor and detect chemicals in a liquid environment is possible.

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