Surface acoustic wave transducer

An interdigital surface acoustic wave transducer comprising a substrate of a material in which surface acoustic waves may be propagated and at least two rows of electrodes are laid down on the substrate, a main row of said rows comprising a first group of electrodes arranged in parallel with one another and connected electrically to a first current-conducting pad, and a second group of electrodes arranged in parallel with said electrodes of said first group, said electrodes of said first group being positioned in corresponding spaces between adjacent electrodes of the second group so that overlap regions of the electrodes of the groups are formed, said overlap regions having a constant length, said electrodes of said second group being connected to a second current-conducting pad, a second row positioned between said main row and said second current-conducting pad and comprising a first group of electrodes arranged in parallel with one another and electrically connected to said second current-conducting pad, and also comprising a second group of electrodes arranged in parallel with said electrodes of said first group in said second row and arranged between the electrodes of said first group in a manner such that at least some of the electrodes of said first and second groups of the second row form overlap regions of a variable length, said length being determined by a given impulse response of the transducer, said electrodes of said second group of said second row being coupled conductively and in a direct way to the corresponding electrodes of the second group of the main row, wherein the improvement comprises the substrate comprising at least first and second areas, the first area having and the second area having no piezoelectric properties, the main row having electrodes arranged on the first area of the substrate having piezoelectric properties, and the second row having electrodes arranged on the second area of the substrate having no piezoelectric properties.