Tunable Film Bulk Acoustic Resonators and Filters with Integrated Biasing Resistors

In wireless communications, many radio frequency bands are used. For each frequency band, there are two frequencies one for transmit and the other for receive. As the band widths are small and separation between adjacent bands is also small, many band pass filters with different band pass frequencies are required for each communication unit such as mobile handset. The present invention provides frequency tunable film bulk acoustic resonators (FBAR) with different structures. Thin film biasing resistors are integrated into the FBAR structure for DC biasing and RF isolation. A plurality of the present tunable FBARs are connected to form microwave filters with tunable bandpass frequencies and oscillators with selectable resonating frequencies by varying DC biasing voltages to the resonators.