DUPLEXER UTILIZING SURFACE ACOUSTIC WAVE FILTERS, ESPECIALLY FORMING SAW FILTERS SIMULTANEOUSLY ON ONE SUBSTRATE

摘要

PURPOSE: A duplexer utilizing surface acoustic wave filters is provided to maintain a good state of a filter characteristic even if a transmission filter and a reception filter are formed on an identical substrate. CONSTITUTION: A duplexer includes two surface acoustic wave filters. The surface acoustic wave filters are formed on one substrate. At least one of the surface acoustic wave filters is a ladder filter(110a) . A positional difference between centers in a surface acoustic wave propagating direction of two adjacent comb-like electrodes among comb-like electrodes for forming serial-arm resonators of the ladder filter is equal to or smaller than a fourth of the length in the surface acoustic wave propagating direction of the comb-like electrode having the larger number of pairs of electrode fingers of two adjacent comb-like electrodes.