Directional coupler

A directional coupler comprising:

• a multilayer body including a plurality of stacked dielectric layers;
• a main line including a first main line portion and a second main line portion which are connected in series to each other in this order and that is provided in the multilayer body;
• and
• a sub-line including a first sub-line portion and a second sub-line portion which are connected in series to each other in this order, the first sub-line portion being electromagnetically coupled to the first main line portion, the second sub-line portion being electromagnetically coupled to the second main line portion, and the sub-line being provided on one side in a stacking direction with respect to the main line in the multilayer body;
• wherein
• the second main line portion is provided on a dielectric layer that is different from a dielectric layer on which the first main line portion is provided and/or the second sub-line portion is provided on a dielectric layer that is different from a dielectric layer on which the first sub-line portion is provided;
• the main line includes the first main line portion, the second main line portion, and a third main line portion that are connected in series to each other in this order;
• the sub-line includes the first sub-line portion, the second sub-line portion, and a third sub-line portion that are connected in series to each other in this order, the third sub-line portion being electromagnetically coupled to the third main line portion;
• the second main line portion is provided on a dielectric layer that is different from a dielectric layer on which the third main line portion is provided and/or the second sub-line portion is provided on a dielectric layer that is different from a dielectric layer on which the third sub-line portion is provided;
• the first main line portion has a shape which inner-circumferentially extends in a specific direction from an upstream end towards a downstream end;
• the third main line portion has a shape which inner-circumferentially extends in a direction opposite the specific direction from an upstream end towards a downstream end;
• and
• the second main line portion electrically connects the downstream end of the first main line portion with the upstream end of the third main line portion.