Unique Permittivity Determination of Low- Loss Dielectric Materials from Transmis- Sion Measurements at Microwave Frequen- Cies

A non-resonant microwave method has been proposed for accurate complex permittivity determination of low-loss materials. The method uses two measurement data of the magnitude of transmission properties of the sample. While the first datum must correspond to a frequency point resulting in a maximum magnitude of transmission properties, the other can be any datum at a frequency different than the first datum and not far distant from the first datum. Two closed-from expressions are derived for a good initial guess using the above data. The limitations of each expression are discussed. The method has been validated by transmission measurements at X-band (8.2–12.4GHz) of a low-loss sample located into a waveguide sample holder.