FBAR filters at GHz frequencies

Film bulk acoustic resonator (FBAR) technology, which is used for the design and fabrication of microwave filters, is discussed. Filters are presented which exhibit a combination of low loss, small size, and frequency and bandwidth not attainable by any other type of device. Using a piezoelectric film of zinc oxide as a high Q crystal resonator along with passive components an integrable, high performance bandpass filter is formed. The range of center frequencies achievable is roughly 1 to 5 GHz using current resonator designs. The technique features potentially low cost (since the filters are fabricated by batch processing), and, perhaps most intriguing, the capability of being combined with more complex functions (such as a complete radar receiver) as part of a larger mask set. Other advantages such as moderate power handling capability, good temperature stability, and high dynamic range are discussed