In this experiment, one can measure the dielectric properties of the sample material using Cavity Perturbation Tecnique. This technique is applicable for low loss samples and the volume of the sample inserted should be very small in comparison to the volume of the empty cavity as shown in the figure below.

    

S₂₁ vs frequency plots

When a sample is inserted in the cavity there is shift in the resonant frequency (f_r) and the quality factor (Q) of the cavity. With the change in these parameters, dielctric conatant ε^'_r and loss facor ε^"_r of the material can be calculated.

    

    Q_o is the quality factor of empty cavity
    Q_s is the quality factor of sample material inserted in the cavity
    f_c is the resonant frequency of empty cavity
    f_s is the resonant frequency of the sample inserted in the cavity resonator