Round robin test on a cavity resonance method to measure complex permittivity of dielectric plates at microwave frequency

A round robin test on a cavity resonance method was performed by seven groups in Japan, where a cylindrical cavity is cut into two halves at the middle of its length and a dielectric plate sample is placed between these two halves. On the basis of the rigorous analysis by the Ritz-Galerkin method to take account of fringing field in the plate region outside diameter of the cavity, the relative permittivity epsiv´ and loss tangent tandelta are determined accurately from measured resonant frequency and unloaded Q for the TE₀₁₁ mode. The measured results are presented for epsiv´, tandelta, temperature coefficient of relative permittivity TCepsiv, and that of loss tangent TCtandelta. Measurement accuracies estimated by considering the measurement error in each group and the amount of scatter in measured values among these groups are 0.3% for epsiv´ and 4% for tandelta of 10^-4 and 20% for 10^-6. The measurement resolution of TCepsiv and TCtandelta are estimated to be 1 ppm/K and 0.04 %/K for (Zr,Sn)TiO₄ ceramics with TCepsiv=-10.0 ppm/K and TCtandelta=0.24%/K. The measurement error Deltaepsiv´/epsiv´ by the cavity resonance method is about half of ones by the dielectric rod resonance method. This high measurement accuracy and resolution are acceptable for most practical applications to microwave planar circuits