Thin-film bulk-acoustic-wave (BAW) devices are used for RF selectivity in mobile communication system and other wireless applications. Currently, the conventional RF filters are getting replaced by BAW filters in all major cell phone standards. In this thesis, we study solidly mounted BAW resonators (SMR) which are the building blocks of these filters. The good selectivity offered by the BAW resonators makes them excellent components for inter-stage filters and duplexers for mobile applications.
Modelling and development of high performance thin-film BAW devices is a topic of research gaining attention from BAW specialists around the world. The quality factor of an SMR is limited by acoustic substrate losses, because the reflector stack is traditionally optimized to reflect longitudinal waves only. This thesis presents several novel design approaches for optimizing the reflector stack for dual reflection of longitudinal and shear acoustic waves in view of achieving high acoustical quality factor.