Local dielectric measurement by waveguide-type microscopic aperture probe

For dielectric constant measurement of areas smaller than the wavelength, this paper proposes a method of employing waveguide-type microscopic aperture probe. The probe is made of WR-15 waveguide with one end shielded with metal plate of 0.3mm, on which a 0.5mm-dia or a 0.1mm-dia aperture is made. The dielectric constant is derived from the slope of phase difference swept over 50-70 GHz between the cases of free-space transmission with and without the dielectrics. In order to evaluate the system, the dielectric constant of Teflon has been measured by three cases of using the probes of 0.5 mm-dia and 0.1 mm-dia, and two V-band corrugated horns. The results show good agreement.