Multiplexer

A multiplexer, comprising:

• a first circuit board comprising a first metal layer, a first substrate layer, and a second metal layer sequentially stacked along a first direction;
• a second circuit board comprising a third metal layer, a second substrate layer, and a fourth metal layer sequentially stacked along the first direction;
• and
• a third circuit board comprising a fifth metal layer, a third substrate layer, and a sixth metal layer sequentially stacked along the first direction,
• wherein the second metal layer and the third metal layer have same wiring structure, and the second metal layer is connected to the third metal layer to form at least one first signal transmission path structure and at least one filter structure,
• wherein the fourth metal layer and the fifth metal layer have same wiring structure, and the fourth metal layer is connected to the fifth metal layer to form at least one second signal transmission path structure,
• wherein signal coupling between the at least one first signal transmission path structure and the at least one filter structure is performed in a non-contact manner, and signal coupling between the at least one filter structure and the at least one second signal transmission path structure is performed in the non-contact manner.