FREE-SPACE, BROAD-BAND MEASUREMENTS OF HIGH-TEMPERATURE, COMPLEX DIELECTRIC-PROPERTIES AT MICROWAVE-FREQUENCIES

A free-space microwave measurements system is used for the high-temperature measurement of dielectric constants and loss tangents of homogeneous materials and is applicable to composite materials as well. The system is capable of operating in the 5.85-40 GHz frequency range and ambient to 850-degrees-C temperature range. A computer is used to control and coordinate furnace temperature, network analyzer functions, and data storage. Dielectric constants and loss tangents of the materials are calculated from the measured values of S21. The measurement system including the high temperature furnace and the calibration technique are described. Dielectric constants and loss tangents are presented for fused quartz and boron nitride grade HP in the frequency range 13.0-17.4 GHz and the temperature range is from ambient to 850-degrees-C.