Properties of Tunable Filters with Ferroelectric Capacitors

Abstract

The range of a tunability of the filter with ferroelectric capacitor is determined by the commutation quality factor (CQF), which takes into account both the tunability of the capacitor under biasing voltage and the loss factor. For effective tuning, the CQF should be high enough (more than 1000). The main goal of the tunable filter synthesis is to provide non-degrading filter performance while tuning, and particularly to keep the same fractional bandwidth. Two different approaches to the tunable filter design are suggested and discussed: the image parameter method and insertion loss method. For both methods the filter structure is suggested and analyzed.

Keywords:

• Tunable Filter
• Commutation Quality Factor
• Ferroelectric Planar Capacitor