NFC Tag Emulation Mode with Constant Magnetic Field

• US 20150079902A1
• Filed: 04/23/2013
• Published: 03/19/2015
• Est. Priority Date: 05/07/2012
• Status: Active Grant

• Current Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Original Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Inventors: Dhayni, Achraf
• Granted Patent: US 9,379,784 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10237 the reader and the record carrier being capable of selectively switching between reader and record carrier appearance, e.g. in near field communication [NFC] devices where the NFC device may function as an RFID reader or as an RFID tag
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

It is proposed a method for performing electromagnetic induction communication consisting in transmitting modulation data to a first communication device (RD) from a second communication device (TED), said method comprising:—Coupling a first antenna (AR) of a the first communication device (RD) and a second antenna of the second communication device (TED),—Generating a magnetic field by supplying a first current (i1) through this first antenna,—Modulating the magnetic field according to the modulation data; Wherein the first current (i1) is regulated so as to be substantially constant, by introducing a regulating current (iR) which is function of the magnetic field, and wherein the first communication device (RD) determines the modulation data (TXMOD) from the regulating current (iR).

Claims

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

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

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

8. A method according to claim 1, wherein said regulating current is copied by a current mirror so as to provide a copied regulating current.

9. A 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 adapted 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 it 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 adapted to determine a regulating current as a function of said magnetic field, and an injection element adapted to inject said regulating current so as said first current is constant, and said regulation element being further adapted to determine said modulation data from said regulation current.

11. 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.