Patent ID: 7760048
Filing Date: 2010-07-20
Classification: H03H

Abstract:
1. An elastic wave filter comprising: two longitudinally coupled resonator type elastic wave filter elements, each longitudinally coupled resonator type elastic wave filter element including three IDTs arranged on a piezoelectric substrate in a transmitting direction of an elastic wave; wherein two of the three IDTs of one longitudinally coupled resonator type elastic wave filter element are cascade connected to two of the three IDTs of the other longitudinally coupled resonator type elastic wave filter element; each respective IDT of the three IDTs includes a narrow pitch electrode finger portion at each end portion of the respective IDT that is disposed adjacent to a neighboring one of the three IDTs, the narrow pitch electrode finger portion having a pitch that is smaller than a pitch of a remaining portion of the respective IDT; and in at least one of the longitudinally coupled resonator type elastic wave filter elements, the electrode fingers disposed in the remaining portion of at least one of the IDTs that are cascade connected are arranged at a pitch that is smaller than a pitch of the electrode fingers disposed in the remaining portion of a remaining IDT that is not cascade connected, such that a frequency of a conductance peak in said at least one of the cascade connected IDTs is higher than a frequency of a conductance peak in the remaining IDT.