Commutation Quality Factor as a Working Tool for Optimization of Microwave Ferroelectric Devices

The commutation quality factor (CQF) is suggested as a generalized criterion of the material tunability and its loss factor. The figure of merit of a switchable device is uniquely determined by the CQF. From this point of view the CQF is used as a working tool for optimization of the microwave devices. A comparison between analog and digital ferroelectric phase shifter was performed using the CQF as a criterion. Theoretically was predicted that a digital phase shifter based on lumped tunable ferroelectric capacitors can be designed with minimal achievable insertion loss. As an example, the 180 reflection type phase shifter is discussed.