US Patent 8991712 Coupling in and to RFID smart cards

A data carrier such as a smart card comprising an antenna module (AM) and a booster antenna (BA). The booster antenna (BA) has an outer winding (OW) and an inner winding (IW), each of which has an inner end (IE) and an outer end (OE). A coupler coil (CC) is provided, connecting the outer end (OE, b) of the outer winding (OW) and the inner end (IE, e) of the inner winding (IW). The inner end (IE, a) of the outer winding (OW) and the outer end (OE, f) of the inner winding (IW) are left un-connected (free floating). The coupler coil (CC) may have a clockwise (CW) or counter-clockwise (CCW) sense which is the same as or opposite to the sense (CW or CCW) of the outer and inner windings. Various configurations of booster antennas (BA) are disclosed.