NFC tag emulation mode with constant magnetic field

1. A method for performing electromagnetic induction communication consisting in transmitting modulation data to a first communication device from a second communication device, said method comprising:

coupling a first antenna of said first communication device and a second antenna of said second communication device;

generating a magnetic field by supplying a first current through said first antenna; and

modulating said magnetic field according to said modulation data,

wherein said first current is regulated so as to be substantially constant, by introducing a regulating current which is a function of said magnetic field, and wherein said first communication device determines said modulation data from said regulating current.

2. The method according to claim 1 , wherein said coupling is achieved by providing said first antenna and said second antenna in the vicinity of one another.

3. The method according to claim 1 , wherein said magnetic field is modulated by modulating a second current flowing through said second antenna, said second current being dependent of said modulation data.

4. The method according to claim 3 , wherein said second current is modulated by modifying a resistance traversed by said second current according to said modulation data.

5. The method according to claim 1 , wherein said regulating current is determined by capturing the modulation of said first current.

6. The method according to claim 5 , wherein said first current is copied by a current mirror.

7. The method according to claim 6 , wherein a copy of the first current is used to control a value of the regulating current generated by a controlled current source.

8. A method for performing electromagnetic induction communication consisting in transmitting modulation data to a first communication device from a second communication device, said method comprising:

coupling a first antenna of said first communication device and a second antenna of said second communication device;

generating a magnetic field by supplying a first current through said first antenna; and

modulating said magnetic field according to said modulation data,

wherein said first current is regulated so as to be substantially constant, by introducing a regulating current which is a function of said magnetic field, and wherein said first communication device determines said modulation data from said regulating current, wherein said regulating current is copied by a current mirror so as to provide a copied regulating current.

9. The method according to claim 8 , wherein said copied regulating current is supplied to a demodulator for generating a transmitted copy of said modulation data.

10. A reader device comprising:

a first antenna configured to create an electromagnetic coupling with a second antenna of a tag emulator device, to generate a magnetic field according to a first current flowing through the first antenna, and to detect a load modulation of said magnetic field, representative of modulation data provided by said tag emulator device by modulating said first current;

a regulation element configured to determine a regulating current as a function of said magnetic field; and

an injection element configured to inject said regulating current so as said first current is constant, and to determine said modulation data from said regulation current.

11. A system comprising a reader device according to claim 10 and a tag emulator device.

12. A mobile terminal comprising a reader device according to claim 10 .