Antenna device

An antenna device, comprising:

• a dual-band crossed-dipole antenna, comprising four radiators each extending from an axis toward a plane and comprising a first radiating element and a second radiating element for respectively transmitting or receiving radio signals of a first band and a second band, wherein a plane where each radiator is located is perpendicular to a plane where a neighboring radiator is located;
• and
• a reflecting board, disposed on a side of the dual-band crossed-dipole antenna;
• wherein a first projection result generated by projecting the reflecting board along the central axis on a reference plane is substantially a square, and a second projection result generated by projecting the dual-band crossed-dipole antenna along the central axis on the reference plane is substantially corresponding to two diagonals of the square, wherein the reference plane is perpendicular to the central axis;
• wherein a center frequency of the first band is higher than a center frequency of the second band, a diagonal length of the square of the first projection result is greater than 0.6 times of a signal wavelength corresponding to the first band and smaller than 0.35 times of a signal wavelength corresponding to the second band, a nearest distance between the reflecting board and any first radiating element of the four radiators is between 0.15 to 0.25 times of the signal wavelength corresponding to the first band, and the dual-band crossed-dipole antenna is substantially directional in the first band and omnidirectional in the second band.