Tunable microwave filters using ferroelectric materials

A new design approach for a microstrip tunable filter on a two-layered substrate with BSTO thin films is suggested. The coupling factor of a ferroelectric capacitor connected to the microstrip resonators of the filter is considered to make possible the design of the filter with constant pass band width while tuning. Results of the filter characteristic simulation and measurement are presented. Tunable coplanar resonator on single crystal STO disk is also considered.