Patent ID: 7026890

Claim:
A duplexer comprising a ladder filter and a multimode filter that are formed on an identical surface of a predetermined substrate, a first comb-like electrode of the ladder filter and a second comb-like electrode of the multimode filter having an identical layer structure with an equal film thickness, the first comb-like electrode and the second comb-like electrode being formed with single-layer films mainly containing aluminum, the relationship among the film thickness h, in meters, of the first comb-like electrode and the second comb-like electrode, the center frequency f 1 , in Hertz, of the frequency band of the ladder filter, and the center frequency f 2 , in Hertz, of the frequency band of the multimode filter, being expressed as: 300 ≦h×f 1 ≦480 300 ≦h×f 2 ≦430.