In this paper, we present a novel ultra-fast system for continuously monitoring the electrical parameters of a microwave cavity resonator, which can be used to assess the complex dielectric constant of a time-variant material sample within the resonator. The resonator is excited near a selected resonance mode by a digitally generated multisine signal. A receiver system using a Fast Fourier Transform (FFT), with a frequency bin spacing matched to that of the multisine signal, evaluates the resonator response for a number of frequency points in parallel. Using standard numerical curve fitting methods, the resonance frequency, resonance transmission gain and quality factor of the resonator are computed from the sampled frequency response. The complex dielectric constant of a material sample in the resonator can be calculated using these electrical parameters.
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