Quality evaluation of tunable microwave filters on ferroelectric capacitors

The tuning efficiency of microstrip filters that use ferroelectric capacitors as control elements depends on the properties of the capacitors and the filter’s resonators. The properties of these components are included if the quality criterion of a tunable filter is defined as the ratio of the center frequency tuning bandwidth to the passband of the filter. A quality criterion suggested in this work allows one to estimate the limiting characteristics of tunable filters.