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Decay Method for Measuring Complex Dielectric Constants During Microwave Processing

Published online by Cambridge University Press:  15 February 2011

O. Iny  and
M. Barmatz
O. Iny
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109
M. Barmatz
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109
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Abstract

We have developed a fast in-situ method for measuring the quality factor, Q, and resonant frequency, fr, for an isolated microwave resonant mode. The mode resonant frequency was continuously monitored using a phase modulation frequency tracking technique. The quality factor was determined by periodically switching off the microwave power and fitting the decay curve to an exponential. The cavity perturbation method was used with small spherical samples (ka « 1). Combining the Q and fr data with a non-contact measurement of the sample temperature permits the calculation of the temperature dependence of the real (ε′) and imaginary (ε″) dielectric constants. Because of the speed of this technique (≈1 μSce), it can be used during processing to continuously measure the dielectric constants of the material without perturbing the sample temperature. Measurements were performed using isolated TM010 and TEI11 cylindrical cavity modes. Care was taken to minimize the perturbing effects of the sample support. The accuracy of the frequency tracker was verified at room temperature from measurements on several alumina spherical samples. The decay technique was also verified from measurements on several small spherical nylon samples.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 347: Symposium O – Microwave Processing of Materials IV , 1994 , 241
Copyright
Copyright © Materials Research Society 1994

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References

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