Surface acoustic wave filter device with symmetrical electrode arrangement

摘要

A surface acoustic wave filter device includes a substrate which includes quartz or the like piezoelectric material having a small temperature coefficient. The substrate has a surface which is formed with interdigital-type unidirectional transducers on input and output sides, each having a positive electrode and a negative electrode. The positive electrodes and the negative electrodes of each of the input side and output side transducers have electrode fingers which are arranged so as to transduce a harmonic wave of a selected order which is higher relative to a fundamental surface acoustic wave.