Matching circuit, matching circuit element, and communication device

A matching circuit element comprising:

• a multilayer body including a plurality of insulation base materials including an insulation base material in or on which a coil conductor pattern is provided;
• wherein
• a first input/output terminal, a second input/output terminal, a ground terminal, and a capacitor connection terminal are provided on an outer surface of the multilayer body;
• a first coil, a second coil, and a third coil are defined by the coil conductor pattern in the multilayer body;
• the first coil is connected in series between the first input/output terminal and the second input/output terminal;
• the second coil is connected in shunt between the ground terminal and an input/output line between the first input/output terminal and the second input/output terminal;
• the first coil, the second coil, and the third coil share a common winding axis;
• the first coil is sandwiched between the second coil and the third coil in a direction of the common winding axis;
• the first coil and the second coil are magnetically coupled to each other;
• the third coil is magnetically coupled to at least one of the first coil and the second coil;
• one end of the first coil is connected to the first input/output terminal, and another end of the first coil is connected to the second input/output terminal;
• one end of the second coil is connected to the second input/output terminal, and another end of the second coil is connected to the ground terminal;
• and
• one end of the third coil is connected to the ground terminal, and another end of the third coil is connected to the capacitor connection terminal.

A communication device comprising:

• a communication circuit, an antenna, and a matching circuit connected between the communication circuit and the antenna;
• wherein
• the matching circuit includes:
• a first input/output port, a second input/output port, a first coil, a second coil, a third coil, and a capacitor;
• the first coil is connected in series between the first input/output port and the second input/output port;
• the second coil is connected in shunt between a ground and a connection between the first coil and the second input/output port;
• the first coil and the second coil are magnetically coupled to each other;
• the third coil is magnetically coupled to at least one of the first coil and the second coil;
• and
• the capacitor is connected to the third coil, and a closed circuit including the capacitor and the third coil is provided.

A communication device comprising:

• an amplification circuit, an antenna, and a matching circuit connected between the amplification circuit and the antenna;
• wherein
• the matching circuit includes:
• a first input/output port, a second input/output port, a first coil, a second coil, a third coil, and a capacitor;
• the first coil is connected in series between the first input/output port and the second input/output port;
• the second coil is connected in shunt between a ground and a connection between the first coil and the second input/output port;
• the first coil and the second coil are magnetically coupled to each other;
• the third coil is magnetically coupled to at least one of the first coil and the second coil;
• and
• the capacitor is connected to the third coil, and a closed circuit including the capacitor and the third coil is provided.