Patent ID: 7613434

Claim:
A multiplexer comprising: a first band-pass filter for a first channel, which is formed in a microstrip line on a dielectric substrate and has a first branching characteristic having a center frequency of f 1 and an attenuation pole at a frequency of fa 1 ; and a second band-pass filter for a second channel, which is formed in a microstrip line on a dielectric substrate and has a second branching characteristic having a center frequency of f 2 and an attenuation pole at a frequency of fa 2 , wherein the following relationships (1) to (5) are satisfied: f1<f2 (1); f1<fa1 (2); fa2<f2 (3); f 2− fa 1<( f 2− f 1)/2 (4); and fa 2− f 1<( f 2− f 1)/2 (5), and wherein the second branching characteristic exhibits −20 dB or less at the frequency of fa 1 and the first branching characteristic exhibits −20 dB or less at the frequency of fa 2 .