Discussion and Conclusions
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Various types of resonator for measuring the dielectric properties of microwave ceramics were reviewed. The shielded dielectric resonator was discussed in more detail and modelled analytically using Maxwell’s equations. The radial mode matching method was successfully implemented and used to model an example dielectric resonator demonstrating efficiency and accuracy. Computer-controlled cryogenic apparatus was developed for measuring the resonant frequency and Q-factor of dielectric resonators containing samples of MgO, LaAlO\(_3\), TiO\(_2\) and Al\(_2\)O\(_3\). Temperature measurements between 10 K and room temperature were taken and processed using the radial mode matching to produce accurate values of the relative permittivity and loss tangent. Anisotropy in the relative permittivity was tackled by measuring different resonant modes, close in frequency, with different polarizations.