Amendment of cavity perturbation technique for loss tangent measurement at microwave frequencies

Theoretically, the quality factor of a metal resonant cavity will be increased after introducing a lossless dielectric sample. However, this increment of quality factor is not put into the consideration of the calculation of loss tangent measurement for the conventional cavity perturbation method, widely used on the measurements of microwave dielectric properties. Therefore, the conventional resonant perturbation formulas for dielectric loss measurement should be amended. This amendment is introduced in this study and the amended formulas for loss tangent measurement are given. With the amended formulas, no standard sample is required for measurement which simplifies the measuring procedure suggested by the previous publication. In addition, the measuring error on loss tangent on the conventional formula is discussed. Experiments have shown the improvement of measurement accuracy by this modification.