Surface acoustic wave multi-mode filter

摘要

PROBLEM TO BE SOLVED: To provide a multiplex surface acoustic wave (SAW) mode filter with which the band of passage characteristics can be widened, satisfactory out-of-band attenuation characteristics can be provided and balanced input/output constitution can be provided as well. ;SOLUTION: A 1st SAW resonator composed of an IDT electrode 12a and reflectors 12b and 12c and a 3rd SAW resonator composed of an IDT electrode 14a and reflectors 14b and 14c are parallelly formed on a voltage substrate 11, and a cyclic structure strip line electrode string 13a is formed between both the resonators. Acoustic coupling is performed by proximately arranging these three elements. The cyclic structure strip line electrode string 13a is grounded through the reflectors 12b, 12c, 14b and 14c and mutually adjacent bus bar electrodes are made electrically independent.;COPYRIGHT: (C)1997,JPO