Tunable FBARs: Frequency tuning mechanisms

Tolerances of the fabrication process, the layout design, the process design, and the physical environment of operation may affect the resonance frequency of thin-film bulk acoustic wave resonators (FBAR). Consequences are poor stability, increased phase noise, and performance degradation at the system level. This paper reviews a variety of frequency tuning mechanisms and techniques intended for frequency control in FBARs. Techniques are classified among fabrication, post-fabrication and during-operation frequency compensation.