Miniature tunable filter

A method for forming a miniature tunable filter, comprising acts of:

• forming at least two adjacent coaxial-type resonators coupled to one another, wherein the formation of each coaxial-type resonator comprises acts of:
• forming a ceramic dielectric cavity having an exterior surface and forming a tuning rod passage extending through the ceramic dielectric cavity, wherein the exterior surface of the ceramic dielectric cavity comprises a metal coating;
• forming and inserting a mechanically tunable tuning rod having a threadless exterior surface into the rod passage of the ceramic dielectric cavity, wherein the miniature tunable filter is tuned by linearly sliding the mechanically tunable tuning rod into and out of the tuning rod passage of the ceramic dielectric cavity;
• and
• forming a low impedance coaxial section and surrounding at least a portion of the mechanically tunable tuning rod with the low impedance coaxial section to create an effective microwave short-circuit at a resonant frequency of the miniature tunable filter.