Patent ID: 7479846

Claim:
A duplexer comprising: a transmission filter and a reception filter that are connected to a common terminal, each of the transmission filter and the reception filter being composed of acoustic wave resonators formed on single substrates, respectively, or both of the transmission filter and the reception filter being composed of acoustic wave resonators formed on a single substrate; and a reactance circuit that is connected to at least one of the transmission filter and the reception filter, the reactance circuit including an insulating substrate, a plurality of lumped-constant inductors, and at least one capacitor, the plurality of lumped-constant inductors and the at least one capacitor being formed directly on a surface of the insulating substrate so that patterned conductive materials of the lumped-constant inductors formed by spiral coils are directly formed on the surface of the insulating substrate, the lumped-constant inductors formed by spiral coils facing only a non-grounded opposite surface of the insulating substrate, a chip having the transmission filter and the reception filter or chips respectively having the transmission filter and the reception filter and the insulating substrate being provided on another substrate.