Permittivity measurements using a coaxial-line conical-tip probe

A conical-tip probe for the measurement of permittivity is presented which retains many of the advantages of the normal-plane probe including ease of sample preparation and moderate sample volume requirement, but which is mechanically better suited than monopole probes for the measurement of a wide range of biological materials since it does not promote free moisture regions resulting from cell rupture. The probe input admittance is found by modelling the probe as a short partially-sheathed monopole in free space and then a well-known antenna scaling theorem is used to determine the admittance and hence permittivity in the dielectric medium