On the zf measurement of microwave dielectric ceramics

As a key parameter of microwave dielectric ceramics, the temperature coefficient of resonant frequency ( z f ) determines the temperature stability of microwave dielectric ceramics and relevant microwave devices. The z f of a microwave dielectric ceramic is typically calculated from the measured resonant frequencies of the system, consisting of the ceramic sample plus other dielectric elements, at two temperatures -60 - 70 degrees C apart. This measurement process assumes that z f is a constant; however, it is generally temperature-dependent based on both theoretical and experimental results. Furthermore, the as-measured z f is actually the z f of the dielectric resonator system , which is different from that of the sample itself. In this paper, these two overlooked problems during z f measurement are discussed in detail, and suggestions are given to avoid their possible misleading consequences and thus ensure the reliability of z f measurements.