MODIFIED PERTURBATION METHOD FOR PERMITTIVITY MEASUREMENTS AT MICROWAVE FREQUENCIES.

A method of permittivity measurement by a cavity perturbation technique is described. The cavity resonates in two modes at two different frequencies. Continuous measurement of the dielectric constant of a test sample can be performed using a low-frequency digital counter (up to 500 MHz) while the loss factor can be determined from the difference in the transmission coefficients at the two resonant frequencies. Experimental results for rectangular and circular cylindrical geometries of cavities used for permittivity monitoring at 2450 MHz are also reported.