Longitudinally-coupled multi-mode piezoelectric bulk wave filter and electronic component

摘要

A longitudinally-coupled multi-mode piezoelectric bulk wave filter using the piezoelectric longitudinal effect includes a plurality of excitation electrodes extending substantially parallel to each other, a laminated piezoelectric body including a plurality of piezoelectric layers arranged between the excitation electrodes and polarized in a predetermined direction, an input electrode and output electrode disposed on a first side surface of the laminated piezoelectric body, and a ground electrode disposed on a second side surface of the laminated piezoelectric body. When an input signal is applied between the input electrode and the ground electrode, vibration modes of different orders of harmonic waves are excited and coupled so that an output signal is output between the output terminal and the ground terminal. Let T represent the dimension of the width between the opposed first and second side surfaces of the laminated piezoelectric body and D represent the distance between the adjacent excitation electrodes, and T/D is equal to or smaller than about 0.9. As a result, a longitudinally-coupled multi-mode piezoelectric bulk wave filter presenting a large out-of-band attenuation is provided.