Over many years, RF-MEMS have been a hot topic in research at the technology and device level. In particular, various kinds of mechanical Si-MEMS resonators and piezoelectric BAW (bulk acoustic wave) resonators have been developed. The BAW technology has made its way to commercial products for passive RF filters, in particular for duplexers in RF transceiver front ends for cellular communications. Beyond their use in filters, micromachined resonators can also be used in conjunction with active devices in innovative circuits and architectures. Possible applications are active tunable RF front-end filters, frequency synthesizers for LO generation, or temperature-compensated MEMS resonators for frequency/time reference potentially replacing the long-time used quartz crystal
