Antenna unit, antenna system and electronic device

An antenna unit, comprising a helical antenna with a three-dimensional structure,

• wherein the helical antenna is disposed on an edge region of a carrier board, and comprises at least one turn of helical coil, wherein each of the at least one turn of helical coil comprises a plurality of helical segments that are not in a same plane, and the plurality of helical segments are respectively disposed in a plurality of layers of the carrier board,
• wherein the carrier board further comprises one or more ground planes, wherein the one or more ground planes cover a middle region of the carrier board to expose the edge region of the carrier board, the one or more ground planes are electrically connected via contact holes that penetrate the carrier board along a thickness direction of the carrier board, a notch retracted toward the middle region of the carrier board is formed on the one or more ground planes near the edge region of the carrier board, and a portion of the helical antenna is disposed in the carrier board exposed by the notch.