General equations for the design and evaluation of a stack of two bulk acoustic wave resonators (original) (raw)
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The selection of a proper metal electrode, piezoelectric layer, optimization of coupling coefficient and Q value of film bulk acoustic resonators (FBAR) are the key issues in the design and performance enhancement of a FBAR based bandpass filters. The optimum effective coupling coefficient is determined by studying the effect of various metal electrodes and by varying the thickness ratio of electrode and piezoelectric layer. In this paper, we present the optimum performance analysis of film bulk acoustic resonator in terms of effective coupling coefficient and spurious resonances. The optimum effective coupling coefficient of 7.1% is obtained with tungsten electrode with thickness ratio of 0.1. The spurious resonances have been minimized by different frame-like FBAR structures and simulated using COMSOL Multiphysics design tool. The boundary frame FBAR shows the best balance of performance by effectively suppressing the spurious resonances along with no reduction in effective coupling coefficient. These optimized film bulk acoustic wave resonators can be utilized for the implementation of high performance bandpass filters.