Multiplexer, filter, and communication device

A multiplexer that performs communication in which a first antenna radiates and receives radio frequency signals of a first frequency band group and a second antenna radiates and receives radio frequency signals of a second frequency band group, the first frequency band group including a 5th generation new radio (5G NR) communication band, the multiplexer comprising:

• a common terminal connected to the first antenna;
• a first input/output terminal and a second input/output terminal;
• a first filter connected between the common terminal and the first input/output terminal, the first filter having a pass band that comprises frequencies of a first radio frequency signal of a first communication band in the first frequency band group;
• and
• a second filter connected between the common terminal and the second input/output terminal, the second filter having a pass band that comprises frequencies of a second radio frequency signal of a second communication band in the first frequency band group, the first communication band including the 5G NR communication band, and the other communication bands of the first and second frequency band group being different from the 5GNR communication band,
• wherein:
• the second frequency band group has higher frequencies than the first communication band and the second communication band has lower frequencies than the first communication band, or the second frequency band group has lower frequencies than the first communication band and the second communication band has higher frequencies than the first communication band,
• a first filter comprising:
• a first terminal and a second terminal;
• a first inductor connected between ground and a first node, the first node being on a path that connects the first terminal and the second terminal;
• a second inductor connected between the ground and a second node on the path, the second node being different than the first node, the second inductor being magnetically coupled with the first inductor;
• a first resonant circuit connected between ground and a third node on the path, the third node being located between the first node and the second node;
• and
• a second resonant circuit connected between the ground and the third node, wherein each of the first resonant circuit and the second resonant circuit is a LC series resonant circuit, wherein a frequency of a first attenuation pole of the first filter caused by the first resonant circuit and a frequency of a second attenuation pole of the first filter caused by the magnetic coupling are closer to the second communication band than to the first communication band, and the frequency of the first attenuation pole is closer to the first communication band than to the frequency of the second attenuation pole.