Mobile device and manufacturing method thereof

A mobile device, comprising:

• a first circuit board, comprising a system ground plane;
• a metal frame, at least comprising a first portion, wherein the first portion is electrically coupled to the system ground plane and a feeding point, and wherein an antenna structure is formed by the first portion and the feeding point;
• an electronic component;
• a second circuit board, electrically coupled to the electronic component, wherein the electronic component and the second circuit board are adjacent to the first portion;
• and
• an RF (Radio Frequency) module, electrically coupled to the feeding point, so as to excite the antenna structure,
• wherein the first portion is excited to generate a low-frequency band, and
• wherein a length of the first portion is equal to 0.5 wavelength of the low-frequency band.