Watch-sized four-port dual-band MIMO antennas

In this paper, a compact four-port dual-band antenna system which operates at 2.10GHz and 4.45GHz is described. The four antenna elements are located on the edges of a square ground plane with a side length of 30mm, which corresponds to 0.21λ_o at 2.10GHz. The proposed antenna volume resembles an iPod shuffle in size, which is suitable for smart watch applications.