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Evaluation of the temperature dependence of dielectric properties using probe-backside reflection method at millimeter-wave frequencies

In this study, we demonstrate the temperature dependence of the dielectric properties of Al2O3 and Ba2Ti9O20 ceramics, using a probe-backside reflection (PBR) method, at frequencies range up to 320 GHz. The impact of transmission loss on the dielectric properties was first eliminated from the measured S-parameter values using the original S-parameter values of a transmission line. Although the temperature coefficient of dielectric permittivity was uncertain owing to limitations in the measurement repeatability of the PBR method, those of loss tangents of Al2O3 and Ba2Ti9O20 ceramics were calculated as 2.8 × 10−5 K−1 and 1.1 × 10−4 K−1, respectively, for frequencies up to 125 GHz. Furthermore, the temperature coefficient of the dielectric permittivity of Al2O3 was calculated as 691 ppm K−1 at 255 GHz, while those of the dielectric loss tangent at 235 GHz and 275 GHz was calculated as 1.2 × 10−5 K−1 and 1.5 × 10−5 K−1, respectively.