GPS and WiFi single ended to differential CRF filters using SiOCH as a de-coupling layer

Two filter applications, GPS and Wi-Fi, using bulk wave coupled resonator filters (BWCRF) are discussed. The device consists of two FBAR resonators stacked one on top of the other and separated by a thin de-coupling layer. We refer to this device as a De-Coupled Stacked Bulk Acoustic Resonator or DSBAR. These devices can be used as stand-alone filters or together with similar devices to create very small filters capable of single-ended to single-ended or single-ended to differential conversion. Also, due to the unique arrangement of the two FBAR one on top of the other, an impedance transformer can be made. Lastly, these devices have a very short ¿ring-down¿ time compared to ¿classic¿ FBAR filters, important for OFDM applications.