Ladder-type piezoelectric filter

摘要

A ladder-type piezoelectric filter includes two parallel resonators adapted to vibrate in a square type vibration mode, each of which has a substantially square shape, and two series resonators adapted to vibrate in a square type vibration mode, each of which has a substantially square shape and has a corner cut portion located at each of four corners. The parallel and series resonators have substantially equal distances between respective opposite side edges thereof and are made from materials having the same frequency constant. The parallel and series resonators are housed within a housing and are aligned at approximate centers thereof.