Patent ID: 6580340
Filing Date: 2003-06-17
Classification: H03H

Abstract:
A piezoelectric filter comprising:at least two first piezoelectric elements adapted to vibrate in a square type vibration mode, having a substantially square shape, and defining at least two parallel resonators; at least two second piezoelectric elements adapted to vibrate in a square type vibration mode and defining at least two series resonators, the at least two second piezoelectric elements being made from a material having a frequency constant that is substantially equal to that of a material from which said at least two first piezoelectric elements is made, each of the at least two second piezoelectric elements having a substantially square shape such that a distance between opposite side edges thereof is substantially equal to that of said at least two first piezoelectric elements and such that each of a plurality of nodal portions located at an approximate central portion of a side edge of each of the at least two second piezoelectric elements is cut, each of said at least two second piezoelectric elements having at least one partial electrode provided at a central portion of a major surface thereof; and a housing containing the at least two first and at least two second piezoelectric elements, wherein the at least two first and at least two second piezoelectric elements are aligned in the housing relative to respective centers of the at least two first and at least two second piezoelectric elements.