Multiplexer and wireless receiver

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 f1 and an attenuation pole at a frequency of fa1;
• 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 f2 and attenuation poles at frequencies of fa2 and fb2 higher than fa2,
• a third band-pass filter for a third channel, which is formed in a microstrip line on a dielectric substrate and has a third branching characteristic having a center frequency of f3 and attenuation poles at frequencies of fa3 and fb3 higher than fa3;
• and
• a fourth band-pass filter for a fourth channel, which is formed in a microstrip line on a dielectric substrate and has a fourth branching characteristic having a center frequency of f4 and an attenuation pole at a frequency of fa4;
• an input portion;
• and
• a delay circuit directly connected to the input portion;
• wherein the following relationships (1) to (15) are satisfied:
• f1<f2 (1)
• f1<fa1 (2);
• fa2<f2 (3);
• f2−fa1<(f2−f1)/2 (4);
• fa2−f1<(f2−f1)/2 (5);
• f2<f3 (6);
• f2<fb2 (7);
• fa3<f3 (8);
• f3−fb2<(f3−f2)/2 (9);
• fa3−f2<(f3−f2)/2 (10);
• f3<f4 (11);
• f3<fb3 (12);
• fa4<f4 (13);
• f4−fb3<(f4−f3)/2 (14);
• and
• fa4−f3<(f4−f3)/2 (15),
• wherein the second branching characteristic exhibits −20 dB or less at the frequency of fa1 and the first branching characteristic exhibits −20 dB or less at the frequency of fa2,
• wherein the third branching characteristic exhibits −20 dB or less at the frequency of fb2 and the second branching characteristic exhibits −20 dB or less at the frequency of fa3,
• wherein the fourth branching characteristic exhibits −20 dB or less at the frequency of fb3 and the third branching characteristic exhibits −20 dB or less at the frequency of fa4, and
• wherein one of the first to fourth band-pass filters is directly connected to the delay circuit.

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 f1 and an attenuation pole at a frequency of fa1;
• 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 f2 and attenuation poles at frequencies of fa2 and fb2 higher than fa2,
• a third band-pass filter for a third channel, which is formed in a microstrip line on a dielectric substrate and has a third branching characteristic having a center frequency of f3 and attenuation poles at frequencies of fa3 and fb3 higher than fa3;
• and
• a fourth band-pass filter for a fourth channel, which is formed in a microstrip line on a dielectric substrate and has a fourth branching characteristic having a center frequency of f4 and an attenuation pole at a frequency of fa4;
• an input portion;
• and
• a fifth and sixth delay circuit, each directly connected to the input portion;
• and
• a first to fourth delay circuit, each directly connected to the first to fourth band-pass filters,
• wherein the following relationships (1) to (15) are satisfied:
• f1<f2 (1);
• f1<fa1 (2);
• fa2<f2 (3);
• f2−fa1<(f2−f1)/2 (4);
• fa2−f1<(f2−f1)/2 (5);
• f2<f3 (6);
• f2<fb2 (7);
• fa3<f3 (8);
• f3−fb2<(f3−f2)/2 (9);
• fa3−f2<(f3−f2)/2 (10);
• f3<f4 (11);
• f3<fb3 (12);
• fa4<f4 (13);
• f4−fb3<(f4−f3)/2 (14);
• and
• fa4−f3<(f4−f3)/2 (15),
• wherein the second branching characteristic exhibits −20 dB or less at the frequency of fa1 and the first branching characteristic exhibits −20 dB or less at the frequency of fa2,
• wherein the third branching characteristic exhibits −20 dB or less at the frequency of fb2 and the second branching characteristic exhibits −20 dB or less at the frequency of fa3,
• wherein the fourth branching characteristic exhibits −20 dB or less at the frequency of fb3 and the third branching characteristic exhibits −20 dB or less at the frequency of fa4, and
• wherein each of the first to fourth delay circuits is connected to the input portion through either the fifth or sixth delay circuit.