Temperature Coefficient Measurement of Microwave Dielectric Materials Using Closed Cavity Method

The closed cavity method is proposed to measure the frequency temperature coefficient (tau(f)) of a dielectric resonator. The tau(f) polynomial, which is linear combination of the temperature coefficient of relative dielectric constant and the linear expansion coefficient of the dielectric and cavity, is given. The coefficients of tau(f) polynomial are discussed in detail. The intrinsic temperature coefficient of resonant frequency (tau(f0)) is introduced to improve the measurement precision. Resonators made of BaO-TiO2-Sm2O3 and (Zr0.8Ti0.2) TiO4 ceramics with Teflon and alumina as supports were measured. The results show that the tau(f) values of the same resonator with above supports are different, and the measured variation between them is more than 3 ppm/degrees C. Using the concept of tau(f0), the variation is less than 2 ppm/degrees C.