| CPC H03H 9/6483 (2013.01) [H03H 9/145 (2013.01); H03H 9/725 (2013.01)] | 12 Claims |
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1. An acoustic wave element comprising:
a piezoelectric substrate;
an interdigital transducer (IDT) electrode on the piezoelectric substrate and including a plurality of comb-shaped electrodes; and
a reflector adjacent to the IDT electrode in an acoustic wave propagation direction; wherein
the comb-shaped electrodes include a plurality of comb-shaped electrode fingers extending in a direction intersecting the acoustic wave propagation direction;
the reflector includes a plurality of reflecting-electrode fingers extending in a direction intersecting the acoustic wave propagation direction;
when, in the a plurality of electrode fingers included in the IDT electrode and the reflector, a center-to-center distance between ones of the electrode fingers adjacent to each other in the acoustic wave propagation direction is defined as an electrode-finger pitch:
an electrode-finger pitch of the plurality of reflecting-electrode fingers is greater than an electrode-finger pitch of the plurality of comb-shaped electrode fingers; and
a center-to-center distance in the acoustic wave propagation direction between a reflecting-electrode finger closest to the IDT electrode of the plurality of reflecting-electrode fingers and a comb-shaped electrode finger closest to the reflector of the plurality of comb-shaped electrode fingers is equal to or less than about 0.9 times the electrode-finger pitch of the plurality of reflecting-electrode fingers;
when a reflecting-electrode finger counted from one of the reflecting-electrode fingers which is closest to the IDT electrode in a direction away from the IDT electrode is designated as a k-th reflecting-electrode finger in order, where k is an integer equal to or greater than 1;
one of the reflecting-electrode fingers farthest from the IDT electrode is defined as an (n+1)-th reflecting-electrode finger, where n is an integer greater than k;
an electrode-finger pitch between the k-th reflecting-electrode finger and a (k+1)-th reflecting-electrode finger is defined as a k-th electrode-finger pitch; and
a value of electrode-finger pitches from a first electrode-finger pitch to the k-th electrode-finger pitch is less than a value of electrode-finger pitches from the (k+1)-th electrode-finger pitch to an n-th electrode-finger pitch.
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