An RF tag comprising: - a grounding conductor; - a spacer of a material having a predetermined dielectric constant in the shape of a rectangular parallelepiped; - a first transmission line forming an electric closed loop to constitute a dipole antenna, said first transmission line arranged on a top and front surface of the spacer, and arranged along sides of a notional rectangular parallelepiped of height T, length L and width W, said notional parallelepiped defined by its bottom surface with points AHKJ and the top surface with points BGED, and having a top and bottom surface of dimensions WxL, front and back surface of dimensions WxT and side surfaces of dimensions LxT, said first transmission line having two line elements of length T extending between points AB and GH, arranged on the front surface, two further line elements of length L extending between points BD and GE, arranged on the top surface, and a line element between points DE of length W, arranged on the top surface, the line elements AB, BD, DE, EG and GH forming said closed loop, said first transmission line connected to the grounding conductor at points A and H, wherein W<2(L+T); - a first branch point C located between the points B and D; - a second branch point F located between the points G and E; - a second transmission line connected between the first branch point C and the second branch point F, and arranged geometrically in parallel with the line element between the points D and E, to constitute an inductor; - a power supply circuit connected in series and arranged between said first branch point C on the first transmission line and the point A at the grounding conductor, wherein the first and second transmission lines are arranged on the spacer, and wherein the grounding conductor is arranged on a bottom surface of the spacer and occupies at least the bottom surface defined by points AHKJ, and said first transmission line is arranged on a top surface of the spacer, and the second transmission line is arranged on the front surface of the spacer. - a grounding conductor; - a spacer of a material having a predetermined dielectric constant in the shape of a rectangular parallelepiped; - a first transmission line forming an electric closed loop to constitute a dipole antenna, said first transmission line arranged on a top and front surface of the spacer, and arranged along sides of a notional rectangular parallelepiped of height T, length L and width W, said notional parallelepiped defined by its bottom surface with points AHKJ and the top surface with points BGED, and having a top and bottom surface of dimensions WxL, front and back surface of dimensions WxT and side surfaces of dimensions LxT, said first transmission line having two line elements of length T extending between points AB and GH, arranged on the front surface, two further line elements of length L extending between points BD and GE, arranged on the top surface, and a line element between points DE of length W, arranged on the top surface, the line elements AB, BD, DE, EG and GH forming said closed loop, said first transmission line connected to the grounding conductor at points A and H, wherein W<2(L+T); - a first branch point C located between the points B and D; - a second branch point F located between the points G and E; - a second transmission line connected between the first branch point C and the second branch point F, and arranged geometrically in parallel with the line element between the points D and E, to constitute an inductor; - a power supply circuit connected in series and arranged between said first branch point C on the first transmission line and the point A at the grounding conductor,