Design and simulation of coupled-resonator filters using periodically slotted electrodes on FBARs [Correspondence]

Abstract

This paper discusses the use of periodically slotted top electrodes in the film bulk acoustic resonator (FBAR) structure for the realization of wideband coupled-resonator filters (CRFs), where evanescent modes in the periodic structure are used for the coupling between adjacent electrodes. First, wave propagation in this structure is investigated. Finite element analysis is performed for the Mo/ZnO/Mo structure. The result suggests that lateral wave propagation is controlled by the Bragg reflection, and that transverse modes can be suppressed when the structure is properly designed. Next, a CRF is designed. It is shown that wideband CRFs are realizable when the period, thickness, and width of slotted electrodes are properly set.

Ultra-wideband longitudinally coupled-resonator filters on lithium niobate using periodically slotted SiO2 as an acoustic coupler

“…The authors showed that transverse modes experiencing propagation toward the crystal x direction can be suppressed by the use of free side boundaries (±x surfaces) in LN-based TSFBARs. 15,16,32) Thus, here we discuss only the plate wave propagation toward the y direction [see Fig. 1(a)].…”

Influence of displacement and patterning of phase shifters for piston mode operation of temperature compensated surface acoustic wave resonators on SiO2/LiNbO3 structure

“…[8][9][10][11][12] In SAW devices, one of the most important design challenges is the suppression of transverse mode resonances. Various suppression techniques [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] have been proposed such as selective removal of SiO 2 , [17][18][19][20][21][22] bending resonator structure, 23) and piston mode design. [24][25][26][27][28] For the piston mode operation, phase shifters such as hammer head and metal dots are placed on electrodes near the aperture edges of interdigital transducer (IDT).…”

Wideband double-mode bulk acoustic wave resonator filters on lithium niobate using periodically slotted electrodes

“…Liu, et al, proposed use of periodically slotted top electrodes for AlN-based TCRFs to increase the lateral coupling, and demonstrated their applicability to wideband TCRFs. 31) The authors applied this configuration to a LNbased TSBAR, and showed that a fractional bandwidth higher than 24% is achievable. 32) This paper is an extension of Ref.…”