Effect of Design Parameters of BAW Solidly Mounted Resonator on the Frequency Response of the Stacked Crystal Filter

Filters based on two acoustically coupled thin-film BAW resonators with a Bragg reflector are considered. The every resonator consists of the piezoelectric transducer based on aluminum nitride layer with thin-film aluminum electrodes. The Bragg reflector is total for the filter and is made of five pairs of molybdenum and aluminum layers. The results of modeling the amplitude-frequency characteristics of the stacked crystal filter based on BAW resonators having different electrode areas are presented. It is shown that with increasing the area of the resonator electrodes by 4 times the relative bandwidth (at -3 dB level) of the filter decreases by 1.8 times. Filters with a center frequency of 2.77 GHz and an insertion loss of -3.1 dB have a relative bandwidth in the range of 0.3...0.54 %. The maximum guaranteed stopband attenuation at 5 % offset is -34.7 dB.