PURPOSE: To suppress the higher inharmonious spurious responses of both vertical and horizontal modes and also to improve the Q for a surface acoustic wave resonator by applying the weighting to an interdigital electrode transducer so as to set the number of all electrode fingers, the number less than 1/5 logarithm or the cross width of the electrode fingers of a logarithm at zero.
CONSTITUTION: A cutting point where the weighting is set at zero for a logarithmic number of electrode fingers provided at both end parts of an interdigital transducer 2 is set at the same cutting point as the outermost one of those weighted electrode fingers crossing each other. Otherwise a cutting point can be set on an extended line of one of both sides of a rhomb. In other words, the rhombic weighting is applied to the middle part reaching both ends from the center part of an IDT electrode of a Love wave type surface acoustic wave resonator where only the IDT 2 is formed on a piezoelectric substrate 1. Then the weighting of a logarithmic number of electrode fingers or several electrode fingers is set at zero at both end parts of the IDT 2. Thus the surface wave energy radiated to both outer sides of the IDT 2 can be minimized and the Q is improved.
ISHII AKINORI
SHIMIZU HIROSHI
SHIMIZU IKUKO