Segmentation of a dielectric resonator enables one to control its spurious property. When a dielectric plate is divided into some planar pieces, the effective permittivity does not change appreciably along the divided plane, while it decreases quite an amount perpendicular to it. This anisotropy is useful for shifting the resonant frequencies of unwanted modes of a dielectric resonator. Since its eigen modes have their own electric field distribution, segmentation of a resonator along the electric line of force of a certain mode will not affect its resonant frequency. When the type of segmentation is changed, we can select the wanted mode, and thus control the resonant frequencies of the unwanted modes. Calculated results with an EM field simulator and experimental results of controlling the resonant frequency are shown for divided dielectric resonators.

Unloaded Q of a dielectric image resonator is discussed based on the electromagnetic field distribution. It is shown that a partial air gap and a dielectric sheet with low permittivity between the dielectric resonator and the shield case reduce both the dielectric loss and the conductor loss. Especially, reduction of the conductor loss is significant, since the magnetic field distribution moves from the conductor to the upper part of resonator. A half-cut image resonator with an air gap and dielectric spacer is simulated and measured. The unloaded Q of the dielectric resonator with low dielectric loss is improved by about two times from that of original image resonator.

Unloaded Q of an image-type dielectric resonator is studied with the simulation and experiment. It is shown that a gap between the dielectric resonator and the shield case reduces both the dielectric loss and conductor loss. The gap moves the electric and magnetic field distributions in the different directions, so that the two losses are reduced. A half-cut image-type resonator with a dielectric spacer inserted into the gap is measured to verify the concept. The unloaded Q is improved by about two times from that without a gap. The proposed structure gives a new packaging method of a dielectric resonator.