抄録
Dielectric constant of alumina was measured by free-space time-domain method in the W-band (75- 110 GHz) millimeter-wave region. By using a millimeter-wave reflection profile, the thickness of sample measured by millimeter-wave was determined from the time difference of the reflection peaks from the front and back surfaces of the sample. The refraction index was calculated from the thickness of sample measured by millimeter-wave and the apparent thickness measured by a caliper, and then the dielectric constant was calculated. Obtained values were almost the same as reported for alumina measured at low-frequency. Apparent dielectric constant rose with the increase of the sample density and equivalent dielectric constant decreased with the increase of the sample density. The slope for the former was larger than that for the later. The approximate lines coincided each other at the density of 100%.
