Compact SMD packaged tunable filter based on substrate integrated coaxial resonators

A surface mountable tunable SIW filter based on coupled coaxial resonators is presented in this paper. A CPW vertical transition is designed in order to provide input/output access to the device. Biasing components are also integrated in the same substrate and accessed through castellated via holes. The proposed filter presents a very compact size and constant fractional bandwidth. Measured results including the effect of the vertical transition show low insertion losses while keeping a constant fractional bandwidth along the tuning range.