Frequency hopping method for RFID tag

• US 20050179521A1
• Filed: 02/12/2004
• Published: 08/18/2005
• Est. Priority Date: 02/12/2004
• Status: Abandoned Application

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Inventors: Pillai, Vijay, Martinez, Rene D., Ramamurthy, Shashi
• Application Number:
  US10/779,320
• Publication Number:
  US 20050179521A1
• Time in Patent Office: Days
• US Class Current: 340/10.340
• 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 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: H04B 1/713 using frequency hopping

Abstract

Radio frequency (RF) power is sent out by a base station to radio frequency identification transponders (RFID tags) for a first time at a first frequency. The frequency is changed to a second frequency, and the RF power sent out for a second time substantially different from the first time.

Claims

1. A method, comprising:

sending power to at least one radio frequency (RF) identification (RFID) transponder (tag) by;

a) sending power P_j for a first time t_j to the tag at a first frequency ƒ

_j chosen from a list of N frequencies ƒ

₁ . . . ƒ

_j, ƒ

_j+1 . . . ƒ

_N; and

then

b) sending power P_j+1 for a time t_j+1 to the tag at a second frequency ƒ

_j+1 chosen from the list of N frequencies, wherein t_j and t_j+1 are substantially different times, and wherein the time between sending power P_j and P_j+1 is less than a time t₀ in which the tag loses a particular tag function if no power is sent to the tag.

2. The method of claim 1, wherein t_j+1 is chosen to be long enough that all tags in operative communication with the base station at frequency ƒ

_j+1 have identifed themselves.

3. The method of claim 1, wherein the sending of power P_j+1 is stopped after a time t_j+1 when no further tags identify themselves.

4. The method of claim 1, wherein P_j and P_j+1 are substantially different powers.

5. The method of claim 4, wherein P_j+1 is substantially reduced from P_j when t_j is too short a time for all tags in operative communication with the base station to identified themselves.

6. The method of claim 1, wherein |t_j+1−

t_j|>

0.05 (t_j+t_j+1).

7. The method of claim 6, wherein |t_j+1−

t_j|>

0.1 (t_j+t_j+1).

8. The method of claim 7, wherein |t_j+1−

t_j|>

0.3 (t_j+t_j+1).

9. The method of claim 1, wherein P_j is a function of time.

10. The method of claim 9, wherein P_j is a monotonically increasing function of time.

11. The method of claim 10, wherein P_j is increased when no further tags identify themselves.