Air cavities integrated with surface mount tuning components for tunable evanescent-mode resonators

This paper presents an air-filled coaxial-cavity resonator integrated with lump tuning components for tunable resonator and tunable filter applications. The tuning components are first mounted on a PCB and then inserted inside the cavity. The air cavity allows for high unloaded quality factor which significantly exceeds the Q of the tuning components and maintains a good tuning range. This paper also discusses techniques to minimize the loss due the dielectric loss tangent of PCB. As an example, we demonstrate a tunable resonator with measured Qu of 45-684 at 2.43 GHz to 3.45 GHz. Simulated and measured results show good agreement.