Split-Post Dielectric Resonator (SPDR)
Split-Post Dielectric Resonators (SPDR) ensure a high precision and are suitable for dielectric measurements with low losses through the change of the resonance frequency and quality factor when they are empty (filled with air) and filled with a test material. An image of a cut of such a resonator is shown here. Both dielectrics (in green) allow the formation of the electromagnetic fields to be concentrated inside their radius and to be continuous in the separation of both resonator halves. For the measurement, the TE010 mode is used for the rotation symmetry of its electric field, which only has a Phi-Component.
For the measurement of material properties in a higher frequency spectrum a so called 'Open Resonator' is available. A gaussian quasi-optical beam is formed with a concave mirror, which is later reflected by a planar mirror. The resulting standing wave is used for the measurement of flat samples placed on the planar mirror. Thanks to its high quality factor it is possible to measure a broad range of low losses materials.