Thin-film bulk acoustic resonator
A thin-film bulk acoustic resonator (FBAR or TFBAR) is a device consisting of a piezoelectric material sandwiched between two electrodes and acoustically isolated from the surrounding medium. FBAR devices using piezoelectric films with thicknesses ranging from several micrometres down to tenth of micrometres resonate in the frequency range of roughly 100 MHz to 10 GHz. Aluminium nitride and zinc oxide are two common piezoelectric materials used in FBARs.
A common application of FBARs is radio frequency (RF) filters for use in cell phones and other wireless applications. Such filters made from a network of resonators (either in half-ladder, full-ladder, lattice or stacked topologies) and are designed to remove unwanted frequencies from being transmitted in such devices, while allowing other specific frequencies to be received and transmitted. FBAR filters can also be found in duplexers. They have partially replaced an earlier technology based on surface acoustic wave (SAW) devices, due to smaller size and increased fabrication and operating efficiencies.
FBARs can be used by microwave oscillators.
FBARs can be used in sensor applications. For instance, when a FBAR device is put under mechanical pressure its resonance frequency will shift.
FBARs can also be integrated with power amplifiers (PA) or low noise amplifiers (LNA) to form an integrated module solution such as PA-duplexer module (PAD), or LNA-filter module.
- University of Southern California explanation on the operation of FBAR's
- Avago Technology product listing for FBAR duplexers