RFID tag and method for processing RFID data

• US 7,088,246 B2
• Filed: 07/28/2003
• Issued: 08/08/2006
• Est. Priority Date: 07/30/2002
• Status: Expired due to Fees

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Fukuoka, Shinichiro
• Primary Examiner(s): SWARTHOUT, BRENT
• Application Number:
  US10/627,872
• Publication Number:
  US 20040065733A1
• Time in Patent Office: 1,107 Days
• Field of Search: 340/568.1, 340/568.6, 340/572.1, 340/572.2, 340/572.4, 340/572.5, 340/572.7, 340/825.54, 340/825.49, 340/10.31, 340/10.3, 340/10.2, 455/31.3, 380/34, 235/435, 235/385
• US Class Current: 340/572.5
• 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
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• 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 7/10029 the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot

Abstract

A collision prevention relational function is disclosed for RFID tags, which increases stability during system operations. The RFID tag includes a parallel resonance circuit having a coil, a resonance capacitor, an adjustment capacitor, a switching circuit, a rectification circuit, a smoothing capacitor, a constant-voltage circuit, a voltage detection circuit, an exclusive OR circuit, a timer circuit, a voltage detection circuit, a control circuit, an OR circuit, a latch circuit, an UID storage device, and a data modulator/demodulator. When a predetermined power supply voltage/operating voltage is obtained, an anti-collision algorithm identifies and adjusts RFID tags that experienced collision.

Claims

1. An RFID tag comprising:

a resonance circuit for receiving a power signal and a command signal;

a switching circuit, said switching circuit turning on and off the resonance circuit;

a power circuit for smoothing said power signal, said power circuit outputting a constant voltage;

a voltage monitor circuit for monitoring a rate at which the constant voltage signal rises;

a resonance capacitive switching circuit for turning on/off the switching circuit in response to an output of the voltage monitor circuit when a predetermined rise is not obtained; and

anti-collision means for outputting anti-collision data in response to a received command.

2. The RFID tag according to claim 1, wherein said resonance circuit comprises an inductance device and a plurality of capacitive devices having a resonant frequency.

3. The RFID tag according to claim 2, wherein the command signal includes a predetermined resonant frequency signal.

4. The RFID tag according to claim 3, wherein the capacitive devices comprise a fixed capacitive device and at least one or more variable capacitive devices.

5. The REID tag according to claim 4 wherein the variable capacitive devices are adjusted to make the resonance frequency of the capacitive devices approach a resonance frequency of an interrogator.

6. The RFID tag according to claim 1, wherein the voltage monitor circuit comprises:

a first voltage detection circuit for outputting a detection output when the constant voltage circuit outputs a low voltage;

a timer circuit, which receives an output of the first voltage detection circuit to output a timer signal for a predetermined period of time; and

a second voltage detection circuit for outputting a second detection output when an output of the constant voltage circuit reaches an operating voltage.

7. The RFID tag according to claim 6, wherein the switching circuit is driven to reduce the resonance frequency of the capacitive devices when an output of the second voltage detection circuit does not reach the operating voltage during a first predetermined period of time.

8. The RFID tag according to claim 7, wherein the switching circuit returns the resonance frequency to an initial state when a voltage capable of a circuit operation cannot be reached.

9. The RFID tag according to claim 7, wherein the voltage monitor circuit sequentially separates any different resonance frequencies of the variable capacitive elements during a second predetermined period of time and returns the resonance circuit to the initial state when all the resonance frequencies are separated and the operating voltage cannot be reached.