Pulsed power method for increased read range for a radio frequency identification reader

• US 6,707,376 B1
• Filed: 08/09/2002
• Issued: 03/16/2004
• Est. Priority Date: 08/09/2002
• Status: Expired due to Term

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Patterson, Hubert A., Lazo, Philip A.
• Primary Examiner(s): Lee, Benjamin C.
• Assistant Examiner(s): TANG, SON M
• Application Number:
  US10/216,576
• Publication Number:
  US 20040036575A1
• Time in Patent Office: 585 Days
• Field of Search: 340/572.1, 340/572.4, 340/10.1, 340/10.2, 340/10.3, 340/10.34
• US Class Current: 340/10.3
• 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 7/10019 resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. collision between the communication channels used by wireless communication devices, where the solution is not particularly adapted for RFIDs or the like, H04W74/08
• CPC Class Codes: G06K 7/10217 parameter settings controlling the transmission power of the interrogator

Abstract

A method to power a radio frequency identification (RFID) reader to increase multi-tag reading capability and increase the reading range of a passive tag without maximizing the continuous transmitted power level is provided. The RFID reader transmits a pulsed interrogation signal until an RFID tag response is received, and then switches to a continuous and pulsed power scheme. The continuous power emitted maintains the power supplied to the RFID tags so the tags will not reset due to loss of power. The pulsed signal permits reading the tags at longer ranges, especially when there is a plurality of tags in the area.

Claims

1. A method for transmitting a radio frequency identification interrogation signal for increasing a radio frequency identification tag reading range, comprising:

transmitting a pulsed radio frequency identification interrogation signal;

receiving a response signal from a radio frequency identification tag;

after receiving said response signal, transmitting said pulsed radio frequency identification interrogation signal and a continuous radio frequency identification interrogation signal simultaneously; and

,

after not receiving a response signal from another radio frequency identification tag, transmitting only said pulsed radio frequency identification interrogation signal.

2. The method of claim 1 further comprising, after receiving said response signal, reading data associated with said radio frequency identification tag;

and, turning said radio frequency identification tag off wherein said radio frequency identification tag does not emit a response signal.

3. The method of claim 2 further comprising, prior to transmitting only said pulsed radio frequency identification interrogation signal after not receiving a response signal from another radio frequency identification tag, turning all radio frequency identification tags on.

4. The method of claim 2 further comprising, prior to transmitting only said pulsed radio frequency identification interrogation signal after not receiving a response signal from another radio frequency identification tag, turning a preselected radio frequency identification tag on.

5. The method of claim 1 wherein transmitting the pulsed radio frequency identification interrogation signal comprises transmitting a pulsed radio frequency identification interrogation signal at a level of up to about 4-watts at a 15% duty cycle measured over about 200 msec.

6. The method of claim 5 wherein transmitting the pulsed radio frequency identification interrogation signal and the continuous radio frequency identification interrogation signal comprises transmitting said pulsed radio frequency identification interrogation signal and a continuous radio frequency identification interrogation signal at a level of up to about 500 mwatts.