Resistive and capacitive modulation in an electromagnetic transponder

• US 20050122212A1
• Filed: 12/02/2004
• Published: 06/09/2005
• Est. Priority Date: 12/05/2003
• Status: Active Grant

• Current Assignee: Stmicroelectronics France (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Enguent, Jean-Pierre
• Granted Patent: US 7,880,588 B2
• Time in Patent Office: Days
• US Class Current: 340/10.100
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Abstract

The selection of at least one back-modulation element of an electromagnetic transponder from among a plurality of resistive and/or capacitive modulation elements of the load of an oscillating circuit of the transponder, including selecting the modulation element(s) according to a binary message received from a read/write terminal.

Claims

1. An electromagnetic transponder comprising:

an oscillating circuit;

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

at least one first parameterizable resistive and capacitive modulation circuit, coupled to the oscillating circuit.

2. The transponder of claim 1, wherein a rectifying circuit is coupled to the oscillating circuit to provide a D.C. supply voltage to the electronic circuit, said first modulation circuit being placed between the oscillating circuit and said rectifying circuit.

3. The transponder of claim 2, wherein a second parameterizable resistive and capacitive modulation circuit is connected between the rectifying element and the electronic circuit.

4. The transponder of claim 1, wherein each modulation circuit comprises at least one resistive or capacitive modulation element, each element being individually controllable.

5. The transponder of claim 4, wherein each modulation circuit comprises at least one capacitor and one resistor in parallel.

6. The transponder of claim 4, wherein each modulation element is controllable by a modulation signal transmitted by the electronic circuit.

7. A method for selecting at least one back-modulation element of an electromagnetic transponder from among a plurality of resistive and/or capacitive elements for modulating the load of an oscillating circuit of the transponder, comprising selecting the modulation element(s) according to a binary message received from a read/write terminal.

8. The method of claim 7, wherein said binary message is transmitted on a loop request by the read/write terminal.

9. The method of claim 8, wherein a transponder receiving said request responds by using modulation elements selected according to said binary message received from the terminal.

10. The method of claim 9, wherein the terminal stores a plurality of responses performed with different modulation elements and sends a last transmit request with a binary configuration message corresponding to the response received with the best quality.