Dielectric loaded HTS resonators

There exists considerable experience worldwide in research and development of high Q dielectric resonators based on sapphire and conventional superconductors at liquid helium temperatures. Stable microwave loop oscillators have been built, based on high Q resonators and cryogenic microwave functional elements such as low noise semiconductor amplifiers, phase shifters and filters operating at liquid helium temperatures and more recently at 70 K. As a result of the recent availability of reliable low power cryocoolers it has become possible to design dielectric loaded resonators making use of ultralow microwave loss properties of thin films of high temperature superconductors (HTS) such as YBa₂Cu₃O_7-x