Bulk wave resonator and bulk wave filter
A bulk wave resonator comprising: a substrate ( 1 ); a layer ( 3 ) of piezoelectric material deposited on the substrate; a first electrode ( 2 ) and a second electrode ( 4 ) which are arranged on opposite surfaces of the layer ( 3 ) of piezoelectric material, the overlapping area of the first electrode ( 2 ) and second electrode ( 4 ) defining the resonance range of the bulk wave resonator, characterized in that the overlapping area in an intersecting plane parallel to at least one of the electrodes ( 2, 4 ) has an aspect ratio in the range from 1 (b/a) 100, where a is the length and b the width of the bulk wave resonator. The invention also relates to a bulk wave filter comprising such bulk wave resonators.
1 . A bulk wave resonator comprising:
a substrate ( 1 );
a layer ( 3 ) of piezoelectric material deposited on the substrate;
a first electrode ( 2 ) and a second electrode ( 4 ) which are arranged on opposite surfaces of the layer ( 3 ) of piezoelectric material, the overlapping area of the first electrode ( 2 ) and second electrode ( 4 ) defining the resonance range of the bulk wave resonator, characterized in that the overlapping area in an intersecting plane parallel to at least one of the electrodes ( 2 , 4 ) has an aspect ratio in the range from 1≦(b/a)≦100, where a is the length and b the width of the bulk wave resonator.
2 . A bulk wave resonator as claimed in claim 1 , characterized in that the aspect ratio is in the range from 1≦(b/a)≦50.
3 . A bulk wave resonator as claimed in claim 1 , characterized in that the aspect ratio is situated in the range from 2≦(b/a)≦50.
4 . A bulk wave resonator as claimed in claim 1 , characterized in that the aspect ratio is situated in the range from 2≦(b/a)≦8.
5 . A bulk wave filter comprising bulk wave resonators as claimed in claim 1 of which at least one is arranged as a series resonator (S) and at least one as a parallel resonator (P).
6 . A bulk wave filter as claimed in claim 5 , characterized in that a plurality of bulk wave resonators (S, P) are provided which are mirror symmetrically arranged in the direction of the length a of an axis (A/A) of a series resonator (S).
7 . A bulk wave filter as claimed in claim 6 , characterized in that the bond wires and flip chip bumps ( 7 ) are arranged mirror symmetrically with the axis (A/A).
8 . A bulk wave filter as claimed in claim 5 , characterized in that the interconnection of a plurality of parallel resonators (P) is effected by series-arranged bulk wave resonators.
9 . A bulk wave filter as claimed in claim 5 , characterized in that the series resonators (S) are connected so that an electrode need not be contacted (floating electrode).
10 . The use of a bulk wave filter as claimed in claim 5 in a mobile telephone, a wireless communication network or the like.