Patent ID: 7990234
Filing Date: 2011-08-02
Classification: H03H

Abstract:
1. An elastic wave filter provided with a circuit above a piezoelectric substrate wherein the piezoelectric substrate extends in a front/rear direction from a front position to a rear position and extends in a lateral direction between a left lateral position to a right lateral position, the circuit comprising: a first series arm elastic wave resonator, a second series arm elastic wave resonator and a parallel arm elastic wave resonator connected to a common connection point; said first series arm elastic wave resonator including a first bus bar and a second bus bar opposing one another along the front/rear direction and a first IDT electrode provided between the first bus and the second bus bar; one out of said second series arm elastic wave resonator and said parallel arm elastic wave resonator being disposed adjacent the first series arm elastic wave resonator in a row extending along the lateral direction, and including a third bus bar and a fourth bus bar opposing one another along the front/rear direction and a second IDT electrode provided between the third and fourth bus bars, and at least part of the fourth bus bar being disposed at an area within a virtual extension of the second bus bar in the lateral direction; another one out of said second series arm elastic wave resonator and said parallel arm elastic wave resonator including a fifth bus bar and a sixth bus bar opposing one another along the front/rear direction, and a third IDT electrode provided between the fifth and sixth bus bars; said another one of said second series arm elastic wave resonator and said parallel arm elastic wave resonator being positioned on a rear side of the row having said first series arm elastic wave resonator and the one out of said second series arm elastic wave resonator and said parallel arm elastic wave resonator such that said third IDT extends in the lateral direction from a first IDT end to a second IDT end so as to have: said fifth bus bar extends laterally from a first fifth bus bar portion adjoining said first portion of said third IDT to a second fifth bus bar portion adjoining said second portion of said third IDT; and said fifth bus bar being formed adjoined to said second bus bar at said first fifth bus bar portion and formed adjoined to said fourth bus bar at said second fifth bus bar portion so as to bridge said second and fourth bus bars; taking a constant-K circuit composed of the series arm elastic wave resonator and the parallel arm elastic wave resonator as a base section, and connecting two or more of the base section in a ladder type; making the series arm elastic wave resonator contained in a first base section where said parallel arm elastic wave resonator is positioned on the output side, serve as said first series elastic wave resonator; and making the series arm elastic wave resonator adjacent to the first base section, and contained in a second base section where said parallel arm elastic wave resonator is positioned on the input side serve as said second series arm elastic wave resonator.