Load Modulation in an Electromagnetic Transponder

• US 20080197973A1
• Filed: 06/03/2005
• Published: 08/21/2008
• Est. Priority Date: 06/03/2004
• Status: Abandoned Application

• Current Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Enguent, Jean-Pierre
• Application Number:
  US11/628,425
• Publication Number:
  US 20080197973A1
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: H04B 1/7097 Interference-related aspects

Abstract

The invention relates to a method for modulating data (D) to be transmitted by an electromagnetic transponder (10′) by means of at least one resistive and/or capacitive element (18) for modulating the charge of an oscillating circuit that it comprises. The invention consists of combining, by an involutive function (19), the flow of data to be transmitted with a spread spectrum sequence (c_i(t)), said sequence being selected according to a configuration message (SRFU) received from a read/write terminal (1′).

Claims

1. A method for modulating data to be transmitted by an electromagnetic transponder by means of at least one resistive and/or capacitive element of modulation of the load of an oscillating circuit that it comprises including combining, by an involutional function, the data flow to be transmitted with a spectrum spreading sequence, said sequence being selected according to a configuration message received from a read/write terminal.

2. The method of claim 1, wherein said function is an XOR.

3. The method of claim 1, wherein said spreading sequence is selected from a set of sequences all having the feature of having an average frequency in the operating range of a demodulator comprised by the terminal.

4. The method of claim 1, wherein the frequency of a remote-supply carrier from the terminal to the transponder is used as a clock for generating the spreading sequenced.

5. The method claim 1, wherein said configuration message is transmitted in a request frame transmitted in a loop by the read/write terminal.

6. The method of claim 5, wherein a transponder receiving said request responds in a frame by using a spreading sequence (c_i(t)) selected according to said binary message received from the terminal.

7. The method of claim 6, wherein the terminal stores a plurality of responses performed with different spreading sequences and sends a last request with a configuration message corresponding to the response received with the best quality.

8. The method of claim 1, wherein the spreading sequence forms a key for ciphering the transmitted data.

9. A method for demodulating a signal received from an electromagnetic transponder and containing data modulated by the method of claim 1, comprising combining the signal, by a same function, with the same spreading sequence as that having been used for the transmission.

10. An electromagnetic transponder comprising:

an oscillating circuit;

an electronic circuit comprising a transmit circuit for transmitting digitally-coded data;

at least one resistive and/or capacitive modulation circuit coupled to the oscillating circuit; and

means for combining, by an electromagnetic transponder by means of at least one resistive and/or capacitive element of modulation of the load of an oscillating circuit that it comprises combining, by an involutional function, the data flow to be transmitted with a spectrum spreading sequence, said sequence being selected according to a configuration message received from a read/write terminal

11. A terminal of communication with an electromagnetic transponder comprising:

an oscillating circuit;

an electronic circuit comprising a transmit circuit for transmitting digitally-coded data;

a modulation circuit coupled with the oscillating circuit;

a demodulator of a signal sampled from the oscillating circuit; and

means for implementing the method of

means for combining, by an electromagnetic transponder by means of at least one resistive and/or capacitive element of modulation of the load of an oscillating circuit that it comprises combining, by an involutional function, the data flow to be transmitted with a spectrum spreading sequence, said sequence being selected according to a configuration message received from a read/write terminal.