Acoustic surface wave transducer and filter built around this transducer

摘要

An acoustic surface wave interdigital transducer comprises a main and auxiliary rows of electrodes arranged on a piezoelectric substrate. The main row of electrodes comprises a first group of electrodes galvanically connected to a first contact area and a second group of electrodes parallel to the electrodes of the first group and disposed therebetween so that there are formed overlapping portions having the same length. The auxiliary row of electrodes comprises a third group of electrodes galvanically coupled to the second contact area and a fourth group of electrodes parallel to the electrodes of the third group connected directly to the corresponding electrodes of the second group of the main row and disposed between the electrodes of the third group so as to form overlapping portions of electrodes of both groups, said portions having a variable length. The electrodes of the second group of the main row are connected to the second contact area through capacitances. The distances between the longitudinal axes of the adjacent electrodes of the third and fourth groups of the auxiliary row differ from the distances between the longitudinal axes of the electrodes of the first and second groups of the main row. An acoustic surface wave filter built around the above described acoustic surface wave transducer.