A study on tunable bulk acoustic wave macro resonators

Reconfigurable radio frequency (RF) frontend has been one of the critical improvements needed to realize future mobile communications (5th Generation and beyond). Making the RF filters and duplexers tunable to simplify RF frontend is an approach to realize reconfigurable RF. Tunable resonators and filters that meet critical RF performance requirements are becoming more desirable. In this paper, we present a comprehensive study on conventional RF and micro-electromechanical systems (MEMS) based tunable filter implementations. Acoustic wave based resonators and filters and current research on bulk acoustic wave (BAW) tunable filters are described. Present tunable BAW filters are found having either low tuning range or fixed frequency shifts. There is an opportunity to extend current tuning principle to achieve better discrete levels of tuning range for practical tunable filter implementation.