Patent ID: 7973449

Claim:
A transducer for surface acoustic waves, comprising: a carrier substrate arranged on a piezoelectric crystal, a first electrode and a second electrode, wherein the electrodes are arranged contactlessly to each other on the surface of the carrier substrate, and wherein each of the electrodes comprises a bar electrode having a plurality of electrode fingers, and the bar electrode of the first electrode extends parallel or substantially parallel to the bar electrode of the second electrode, and a plurality of fingers extends perpendicular or substantially perpendicular to the bar electrodes, wherein a plurality of fingers of the first electrode and a plurality of fingers of the second electrode interdigitate each other, wherein each of the electrodes comprises a plurality of electrode fingers, each of the plurality of fingers having a centre axis being parallel to the respective longitudinal axis and being spaced apart from the centre axis of an adjacent finger of the same electrode by a distance that equals the ratio of the velocity of the surface acoustic wave and the cut-off frequency of the transducer, and the electrode fingers of both electrodes define a plurality of cells each consisting of two fingers, wherein a plurality of said cells consists of a first finger having a first width and second finger having a second width, wherein the first finger of a cell and the second finger of the cell are connected to electrode bars of different electrodes, and the first width is different to the second width, and the ratio of second width to the first width is adapted such that the distance between a centre of excitation and a centre of reflection of one cell amounts between 0.115 and 0.135 or between −0.135 and −0.115 or between 0.365 and 0.385 or between −0.385 and −0.365 of the ratio of the velocity of the surface acoustic wave and the cut-off frequency of the transducer.