A cylindrical cavity resonator for material measurements with coupled resonant modes for sensing and position offset compensation of the dielectric specimen

A cylindrical cavity resonator is separated into two resonating sections by loading it with a metal sheet in the middle of the cavity. The metal sheet of finite thickness contains a circular aperture to support symmetric and asymmetric modes in the cavity. The pair of two modes can be simultaneously employed for sensing dielectric characteristics of rod-shaped specimen passing from top to bottom through the cylindrical cavity. In conventional cavities employed for sensing dielectric rods or tubes, a single resonance TM₀₁₀ mode may result in unwanted detuning of the frequency. The unwanted shift in resonance frequency is caused due to nonuniform electric field distribution, where the total volume of the sensing region is a large fraction of the overall cavity volume. Unlike the conventional design, the main advantage of coupled cavity arrangement is to distinguish the position offset of the dielectric specimen within the sensing region of the nonuniform electric field. The asymmetric mode functions are similar to the conventional TM₀₁₀, whereas the symmetric mode provides for the proximity detection of the dielectric specimen towards the edges.