Patent ID: 9219466
Filing Date: 2015-12-22
Classification: H03H

Abstract:
1. Laterally coupled bulk acoustic wave filter comprising, a vibration layer for carrying bulk acoustic waves, electrode means comprising a first electrode coupled to the vibration layer for exciting to the vibration layer at least one longitudinal wave mode having a first frequency band and one shear wave mode having a second frequency band, and a second electrode coupled to the vibration layer for sensing the filter pass signal, the first and second electrodes being laterally arranged with respect to each other, an acoustic reflector structure in acoustic connection with the vibration layer, the reflector structure comprising a stack of acoustic impedance layers, wherein the thickness of the topmost layer of the stack closest to the vibration layer is larger than the calculatory layer thickness of a corresponding layer in a quarter-wave longitudinal reflector structure, whose reflectance is at its highest for the second frequency band, the thickness of at least one of the layers of the stack below the topmost layer is smaller than the calculatory layer thickness of a corresponding layer in a quarter-wave longitudinal reflector structure, whose reflectance is at its highest for the second frequency band.