TUNABLE MICROSTRIP FILTERS USING SELECTIVELY ETCHED FERROELECTRIC THIN-FILM VARACTORS FOR COUPLING

ABSTRACT

We report on the use of patterned ferroelectric films to fabricate proof of concept tunable one-pole microstrip filters with excellent transmission and mismatch/reflection properties at frequencies up to 24 GHz. By controlling the electric field distribution within the coupling region between the resonator and input/output lines, sufficiently high loaded and unloaded Q values are maintained so as to be useful for microstrip filter design, with low mismatch loss. In the 23–24 GHz region, the filter was tunable over a 100 MHz range, the loaded and unloaded Q values were 29 and 68, respectively, and the reflection losses were below −16 dB, which demonstrates the suitability of these films for practical microwave applications.

This article not subject to US copyright law.Received September 27, 2009; in final form January 9, 2010.