Accession Number : ADP007740

Title :   Measurement of Cavity Perturbation to Determine the Microwave Absorption of a Sphere in a Single Mode Resonator,

Corporate Author : CALIFORNIA INST OF TECH PASADENA KARMAN LAB OF FLUID MECHANICS AND JET PROPUL SION

Personal Author(s) : Watkins, J. L. ; Hagenlocher, C. O. ; Barmatz, M.

Report Date : 27 APR 1992

Pagination or Media Count : 9

Abstract : Experiments have been conducted on materials in a single mode microwave resonator to test predictions of a new theory of microwave absorption by a lossy dielectric sphere. Two different experiments are reported here. An analysis of cavity perturbation for verifying the new absorption model revealed a limitation of a standard form of cavity perturbation theory and led to a modification which generalized its application. The first experiment tested the validity of the modified theory. The cavity perturbations of a nylon sphere were used to calculate the complex permittivity using the standard perturbation theory and the modified form. These permittivity values were compared to that determined from cavity perturbation using a thin nylon rod where the standard and modified forms agree. The results show that the modification is necessary to correctly apply perturbation theory to spherical samples. The second experiment confirmed the theoretical prediction that under certain sample conditions the power absorbed by a sphere in a resonant cavity can be maximum at a location in the cavity where the empty cavity electric field intensity is a minimum. The prediction was checked by comparing the measured power absorbed by a nylon sphere and a-graphite sphere as a function of position in a single mode resonator under identical conditions.

Descriptors :   *CAVITY RESONATORS, *MICROWAVES, ABSORPTION, CAVITIES, DIELECTRICS, ELECTRIC FIELDS, FIELD INTENSITY, FUNCTIONS, GRAPHITE, INTENSITY, LIMITATIONS, MATERIALS, MODELS, MODIFICATION, NYLON, PERTURBATION THEORY, PERTURBATIONS, POWER, PREDICTIONS, RESONATORS, RODS, SPHERES, STANDARDS, TEST AND EVALUATION, PROCESSING, SPACE BASED, THERMOPHYSICAL PROPERTIES, MICROWAVE OVENS, HEATING, SYMPOSIA.

Subject Categories : Radiofrequency Wave Propagation
      Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE