RADIOFREQUENCY IDENTIFICATION DEVICE (RFID) AFFIXED TO AN OBJECT TO IDENTIFIED

• US 20080018476A1
• Filed: 07/13/2007
• Published: 01/24/2008
• Est. Priority Date: 07/21/2006
• Status: Active Grant

• Current Assignee: Ask S.A. (Paragon Group Limited)
• Original Assignee: Ask S.A. (Paragon Group Limited)
• Inventors: GRASSET, Yannick
• Granted Patent: US 7,671,748 B2
• Time in Patent Office: Days
• US Class Current: 340/572.7
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• 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

A radiofrequency identification device (RFID) featuring an antenna (10) connected to a chip designed to be affixed to an object to be identified by a remote reader transmitting to the identification device electromagnetic signals received by the antenna and containing the data allowing the identification as well as the supply voltage (VDC) of the device, the antenna transmitting in return to said reader signals provided by the chip by retromodulation by means of a switch (22) in the chip whose open or closed position defines the digital identification data transmitted by the device. The chip features a variable impedance (30) connected in series with the switch to the terminals of the antenna and a means for detecting (32) the supply voltage to adjust the impedance value so that this supply voltage is always greater than a predetermined value (V_threshold) below which the device can no longer transmit digital identification data.

Claims

1. A radiofrequency identification device (RFID) featuring an antenna (10) connected to a chip (12) designed to be affixed to an object to be identified by a remote reader transmitting to the identification device electromagnetic signals received by said antenna and containing the data allowing the identification as well as the supply voltage (V_DC) of said device, said antenna transmitting in return to said reader signals provided by said chip by retromodulation by means of a switch (22) in said chip whose open or closed position defines the digital identification data transmitted by said device;

said device being characterized in that said chip features a variable impedance (30) connected in series with said switch to the terminals of said antenna and a means for detection (32) of said supply voltage to adjust said impedance value so that this supply voltage is always greater than a predetermined value (Vthreshold) below which the device can no longer transmit said digital identification data.

2. The device according to claim 1, in which said chip (12) features a reservoir capacitance (18) supplying said supply voltage (V_DC) at its terminals.

3. The device according to claim 2, in which said means of detection of said supply voltage (V_DC) is an analog comparator (40) whose output (42) controls the value of said variable impedance (30) in response to the difference between the value of said supply voltage and a predetermined voltage value V_REF.

4. The device according to claim 2, in which said variable impedance consists of several impedances in parallel with a predetermined value each in series with a switch whose open or closed position defines the digital identification data transmitted by said device and in which said means of detection of said supply voltage (V_DC) is a digital comparator (44) whose outputs (C₁, C₂, . . . C_N) respectively control the closing of one of said switches in series with said impedances of predetermined value.