Peterson, Vance Howard

There is an increasing market demand for quartz crystals
which exhibit minimal activity dip or frequency anomalies
over a predefined temperature range. Characterization of
the frequency vs temperature (f-T) activity dip profiles of
these tight tolerance crystals is best carried out using a
system which has been expressly designed for such a purpose.
Frequency measurement accuracy and reliable temperature
control must be established in the system, along with its
being compatible with a computer controlled production or
engineering enviornment. This thesis will present design
and implementation details for a system with the
aformentioned objective of enabling the generation of
accurate crystal activity dip data. The system will provide
the user with up-to-date facilities for meeting the
temperature testing requirements of tight tolerance
crystals.

The research addressed refers to a study on the electromagnetic performance aspects of body-worn radio units operating in the presence of scatterers in close proximity, using analytical, numerical, and experimental methods. The application potentials of such methods include evaluating the integrity of radio units such as cell phones. Consistent with the scope of the study above, considered in this research are specific details on analytical and numerical modeling of the effects of a nearby conducting cylindrical object on the electromagnetic field near a human-model phantom. Calculations are performed using the Finite Difference Time Domain (FDTD) method. Considered are various separations of the body wearing the test radio unit from the proximal object and polarization of the incident wave. An anechoic chamber and the test setup used for the measurement of EM field amplitudes near a saline-water phantom are described. Within the anechoic chamber, a small shielded loop is used as a field measurement probe and is positioned near the test phantom. The field probe orientation was in the vertical plane for characterizing the prevailing electromagnetic field intensity. This study indicates that variations in the field amplitude near the phantom occur, which are responsive to phantom rotation and measurement distance from the phantom. The electromagnetic field amplitude decreases rapidly with increasing distance between the probe and the surface of the phantom. The analysis is also extended to examine the electromagnetic field distribution in the gap between a human body phantom model and a nearby conducting cylinder. An appropriate three-dimensional FDTD method is presented and applied to a near-field problem of analyzing the influence of proximal conductive objects on fields near a phantom wearing an RF unit.