A communication device, comprising: an antenna structure; and a multilayer circuit board, comprising at least a first plane, a second plane and a third plane, wherein one of the first plane, the second plane and the third plane has a ground plane, and the ground plane is in proximity to a clearance region of the multilayer circuit board, and the clearance region is configured to accommodate the antenna structure, wherein the antenna structure comprises: a first metal portion, with a first end and a second end, said first metal portion coupled through a feeding portion to a signal source; and a second metal portion, comprising a linear part and a loop structure, wherein a first end of said linear part is coupled to the second end of the first metal portion, and a second end of said linear part is coupled to the loop structure, said loop structure comprising at least a first line segment and a second line segment, wherein the first line segment and the second line segment are respectively disposed on any two planes of the first plane, the second plane and the third plane, and the first line segment is coupled through at least two conductive vias to the second line segment so as to form the loop structure, and the loop structure is substantially perpendicular to the ground plane; wherein the clearance region is an open aperture of the ground plane; wherein the antenna structure further comprises a shorting portion, wherein the second end of the first metal portion is coupled through the linear part of the second metal portion and through the first line segment and the conductive vias to the second line segment; characterized in that: the first end of the first metal portion is connected through the shorting portion to the ground plane; and the first metal portion, the linear part of the second metal portion, the first line segment, and the ground plane lie on the same plane. an antenna structure; and a multilayer circuit board, comprising at least a first plane, a second plane and a third plane, wherein one of the first plane, the second plane and the third plane has a ground plane, and the ground plane is in proximity to a clearance region of the multilayer circuit board, and the clearance region is configured to accommodate the antenna structure, wherein the antenna structure comprises: a first metal portion, with a first end and a second end, said first metal portion coupled through a feeding portion to a signal source; and a second metal portion, comprising a linear part and a loop structure, wherein a first end of said linear part is coupled to the second end of the first metal portion, and a second end of said linear part is coupled to the loop structure, said loop structure comprising at least a first line segment and a second line segment, wherein the first line segment and the second line segment are respectively disposed on any two planes of the first plane, the second plane and the third plane, and the first line segment is coupled through at least two conductive vias to the second line segment so as to form the loop structure, and the loop structure is substantially perpendicular to the ground plane; wherein the clearance region is an open aperture of the ground plane; wherein the antenna structure further comprises a shorting portion, wherein the second end of the first metal portion is coupled through the linear part of the second metal portion and through the first line segment and the conductive vias to the second line segment; a first metal portion, with a first end and a second end, said first metal portion coupled through a feeding portion to a signal source; and a second metal portion, comprising a linear part and a loop structure, wherein a first end of said linear part is coupled to the second end of the first metal portion, and a second end of said linear part is coupled to the loop structure, said loop structure comprising at least a first line segment and a second line segment, wherein the first line segment and the second line segment are respectively disposed on any two planes of the first plane, the second plane and the third plane, and the first line segment is coupled through at least two conductive vias to the second line segment so as to form the loop structure, and the loop structure is substantially perpendicular to the ground plane; wherein the clearance region is an open aperture of the ground plane; wherein the antenna structure further comprises a shorting portion, wherein the second end of the first metal portion is coupled through the linear part of the second metal portion and through the first line segment and the conductive vias to the second line segment; the first end of the first metal portion is connected through the shorting portion to the ground plane; and the first metal portion, the linear part of the second metal portion, the first line segment, and the ground plane lie on the same plane.