摘要：Dielectric resonators are key components in many microwave and millimetre wave circuits and applications, including high-Q filters and frequency-determining elements for precision frequency synthesis. Multilayered and bulk low-loss single crystal and polycrystalline dielectric structures have become very important for designing these devices. Proper design requires careful electromagnetic characterisation of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique, which has now become the standard for characterizing low-loss structures. This paper will review some of the common characterisation techniques used in the microwave to millimetre wave frequency regime.