Embedded antenna device for electronic communication device

A built-in antenna device for an electronic device for communication, the antenna device comprising:

• a substrate comprising a grounding region and a non-grounding region;
• an antenna radiator disposed in the non-grounding region of the substrate and connected to a feeding portion;
• and
• a transmission line branching from the antenna radiator and disposed in vicinity of the grounding region to have a predetermined length and a predetermined width,
• wherein the transmission line operates as an additional grounding body,
• wherein the transmission line provides capacitive reactance to the antenna radiator,
• wherein the predetermined length and predetermined width of the transmission line and a gap between the transmission line and the grounding region are configured to produce a coupling between the transmission line and the grounding region in at least one predetermined frequency range, and
• wherein the gap between the transmission line and the grounding region is determined as a value to suppress radiating from the transmission line and thereby to prevent the transmission line from operating as a radiator.