Measurement error analysis in the determination of microwave dielectric properties using cavity reflection method

Using the cavity reflection method for the determination of the resonant frequency and the Q-value of a dielectric resonator, the effect of test cavity dimensions on the measured results was examined. Samples of different permittivities and sizes were measured in six different test cavities. A reduction of measured Q-value and a shift of resonance frequency towards higher values when analyzing a TE018 dielectric resonator mode positioned below the TM010 test cavity mode was noticed. For measurements above the TM010 mode reliable identification of the TE018 mode was obtained by previous calculation of the test cavity modes. For this purpose a simple empirical calculation procedure was developed which allows calculation of the resonant frequencies of test cavities with dielectrics inserted. The error of the calculation for TM010 and TE111 modes is lower than ± 1%, and slightly higher for other modes.