Patent ID: 7915976
Filing Date: 2011-03-29
Classification: H03H

Abstract:
1. A surface acoustic wave resonator comprising: a piezoelectric substrate; an IDT electrode provided on the piezoelectric substrate; and a pair of reflectors arranged adjacent to both ends of the IDT electrode in a surface acoustic wave propagation direction; wherein the IDT electrode includes: the IDT electrode is cross-width weighted so that the IDT electrode includes a cross width-weighted portion in which electrode finger cross widths of the IDT electrode are reduced as the cross widths are located farther away from a portion having a largest cross width and are located closer to both ends of the IDT electrode in the surface acoustic wave propagation direction; an edge of the first bus bar to which the first electrode fingers and the second dummy electrodes are connected includes an inclined portion that is inclined relative to the surface acoustic wave propagation direction so that the edge of the first bus bar is spaced a predetermined distance away from an envelope obtained by the cross width weighing; an edge of the second bus bar to which the second electrode fingers and the first dummy electrodes are connected includes an inclined portion that is inclined relative to the surface acoustic wave propagation direction so that the edge of the second bus bar is spaced a predetermined distance away from the envelope obtained by the cross width weighting; a length of an electrode finger of one of the reflectors that is adjacent to an outermost electrode of the IDT electrode is approximately equal to a sum of a length of an outermost electrode finger of the IDT electrode and a length of a dummy electrode opposed to a tip of the outermost electrode finger; and wherein a sum of numbers of electrode fingers and dummy electrodes that a straight line extending from a tip of at least one electrode finger of the IDT electrode in the surface acoustic wave propagation direction crosses before reaching one of the edge of the first bus bar and the edge of the second bus bar is represented by N, N is at least 11, and the number of electrode fingers included in one of the pair of reflectors is approximately N.