Metal smart card with radio-frequency antenna and method for manufacturing such a smart card
A smart card that includes a metal layer including a cavity and a junction connecting the cavity to an edge of the card, an RF chip, an RF antenna electrically connected to the RF chip by a conductive physical connection, the antenna being disposed on a non-conductive layer deposited onto the metal layer, the RF chip being disposed in the vicinity of the metal layer and including a first set of turns routed along the perimeter of the card, including at least one turn extending towards the inside of the card, and electrically connected to a second set of turns routed outside the cavity, along the edges of the cavity, the turns of the two sets of turns being disposed so that the current flows in the same direction in the two sets of turns.
1 . A smart card comprising:
a card body at least partly formed by a metal layer, said metal layer comprising a recessed area formed by a cavity and a junction connecting the cavity to a peripheral edge of the smart card;
an electronic module comprising an RF chip; and
at least one RF antenna electrically connected to the RF chip by a conductive physical connection, the antenna being disposed on a non-conductive layer deposited onto the metal layer, the RF chip being disposed in vicinity of the metal layer, the RF antenna comprising a first set of turns and a second set of turns,
the first set of turns routed along a perimeter of the card, the first set of turns comprising at least one turn extending towards an inside of the card, and being electrically connected to the second set of turns,
the second set of turns routed outside said cavity, along the edges of said cavity to surround said cavity, and
the turns of the two sets of turns disposed so that current flows in a same direction in the first set of turns and in the second set of turns.
2 . The smart card according to claim 1 , wherein eddy currents are produced under effect of an incident magnetic field experienced by the card, with the turns of the first set of turns and the turns of the second set of turns being wound so that said current and the eddy currents flow in the same direction in the second set of turns, and in phase with the incident magnetic field.
3 . The smart card according to claim 1 , wherein said electronic module is positioned in said cavity.
4 . The smart card according to claim 1 , wherein the centre of said cavity is located at the geometric centre of the smart card.
5 . The smart card according to claim 1 , wherein said cavity is round or rectangular and is centred on the centre of the smart card.
6 . The smart card according to claim 1 , wherein said cavity is round, is centred on the centre of the smart card and has a 20 mm diameter.
7 . The smart card according to claim 1 , wherein a surface of said cavity represents a surface that is substantially equal to 1.5% of a surface of the metal layer.
8 . The smart card according to claim 1 , wherein the cavity comprises a dielectric material selected from among wood or ceramic or rigid rubber.
9 . The smart card according to claim 1 , a format of which conforms to an ID1 format.
10 . A method for manufacturing a smart card from a card body at least partly formed by a metal layer, the method comprising:
forming at least one recessed area in said metal layer, the recessed area is formed by a cavity connected by a junction to a peripheral edge of the smart card;
assembling an electronic module comprising an RF chip;
depositing at least two isolating layers on either side of the metal layer; and
forming an antenna electrically connected to the RF chip by a conductive physical connection on one of said isolating layers, the antenna comprising a first set of turns and a second set of turns,
the first set of turns routed along a perimeter of the card, the first set of turns comprising at least one turn extending towards an inside of the card, and being electrically connected to the second set of turns,
the second set of turns routed outside said cavity, along the edges of said cavity to surround said cavity, and
the turns of the two sets of turns disposed so that current flows in a same direction in the first set of turns and in the second set of turns.
11 . The smart card according to claim 1 , wherein
said cavity has a 20 mm diameter,
a surface of said cavity represents a surface that is substantially equal to 1.5% of a surface of the metal layer, and
the cavity comprises a dielectric material selected from among wood or ceramic or rigid rubber.
12 . The smart card according to claim 1 , wherein
the centre of said cavity is located at the geometric centre of the smart card, and
the second set of turns surround said cavity at the geometric centre of the smart card.
13 . The smart card according to claim 1 , wherein said cavity is centred on the centre of the smart card, and
the second set of turns surround said cavity at the centre of the smart card.
14 . The smart card according to claim 1 , wherein the second set of turns surround said cavity and the RF chip.
15 . The smart card according to claim 1 , wherein said RF chip is positioned in said cavity.