High Tc superconductor re-entrant cavity filter structures

Microwave cavity filters are widely used in high frequency communication systems for high quality factor signal filtering. However, their large size makes it inconvenient for them to be used at lower operating frequencies especially in the 1-4 GHz frequency range of most of the present day commercial wireless applications. In order to improve their performance and to reduce their overall size, superconducting cavity filters were designed and simulated. Cylindrical and re-entrant cavity filters were fabricated, using seeded melt grown yttrium barium copper oxide high temperature superconductors. The resonant characteristics of these filters were measured, verifying the concept that small, high Q, cavity filters can be made for wireless applications.