A Systematic Design Method for Band-Pass Filters Composed of Film Bulk Acoustic Resonators

We propose a systematic method to design band-pass filters composed of film bulk acoustic resonators (FBARs), for wireless communication. FBARs have demonstrated excellent performance due to their compact size, low loss, power endurance and IC compatibility. Modifying the traditional Butterworth theory, the ladder-type band-pass filters can be composed of FBARs to satisfy various filter specifications including impedance, center frequency and bandwidth. The filter design parameters are considered using the thickness and area of the composed FBARs, which are used to replace the conventional series and parallel LC resonators. This design philosophy can also be applied to other kinds of band-pass filters. An FBAR's filter is designed and manufactured to demonstrate our approach.