Balun structure

A balun structure, comprising:

• a substrate;
• a first coil structure having a spiral shape and on the substrate, the first coil structure including:
• a first single-layer coil, and
• at least one first laminated coil connected to the first single-layer coil,
• wherein the first single-layer coil is surrounded by the at least one first laminated coil;
• and
• a second coil structure having a spiral shape and on the substrate, the second coil structure including:
• a second single-layer coil, a projection of the second single-layer coil on a surface of the substrate overlaps a projection of the first single-layer coil on the surface of the substrate, and
• at least one second laminated coil connected to the second single-layer coil,
• wherein a number of the at least one second laminated coil is larger than or equal to a number of the at least one first laminated coil, and the at least one second laminated coil is arranged alternately with the at least one first laminated coil or the first single-layer coil in a plane parallel to the surface of the substrate.