EXTENDED-CAVITY PERTURBATION TECHNIQUE TO DETERMINE THE COMPLEX PERMITTIVITY OF DIELECTRIC MATERIALS

An improved measurement technique to determine the complex dielectric properties of materials has been developed that extends the validity o f the conventional cavity perturbation technique for circular cylindri cal rod-shaped samples in circular cylindrical cavities resonating in TM(0n0) modes, The method is particularly useful for the dielectric ch aracterization of fragile, low-loss materials that are difficult to ma chine to typically required thin dimensions, The method further allows for multi-frequency measurements using higher-order radial modes and somewhat alleviates the very small cavity dimensions typically require d by the conventional perturbation technique at higher microwave frequ encies, A validity criterion for the extended method is given, Measure ments of the complex permittivity of NaCl single crystals are presente d, showing excellent agreement with theory.