Film bulk acoustic wave resonator and filter technology

Film bulk acoustic resonators (FBARs) are monolithically integrable with semiconductor devices, leading to small-size and low-cost, high-Q RF circuit elements with wide applications in the electronic warfare, radar, and communications areas. The authors review recent developments in film resonators and the miniature monolithic filters based on these resonators. It is noted that FBAR development has progressed from VHF frequency to UHF frequency operation and FBARs have been combined not only in a hybrid fashion but also integrated monolithically with active circuit elements to form filters and oscillators. While most of the devices operate up to 1 GHz, FBARs that show resonances up to 5 GHz have recently been developed.<>