Method of transporting radio frequency power to energize radio frequency identification transponders

• US 5,850,181 A
• Filed: 04/03/1996
• Issued: 12/15/1998
• Est. Priority Date: 04/03/1996
• Status: Expired due to Term

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Martinez, Rene Dominic, Zai, Li-Cheng Richard, Heinrich, Harley Kent, Sousa, Paul Jorge
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US08/626,820
• Time in Patent Office: 986 Days
• Field of Search: 340/572, 340/825.54, 340/825.69, 340/693, 342/42, 342/44, 342/51, 375/202
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• 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

Abstract

An apparatus and a method of transporting energy from a base station to energize a remote RF transponder having an energy store is described, comprising transporting power in pulses of frequencies chosen from a randomly ordered list of frequencies, wherein the time between pulses when little power is transmitted is less than the time taken for the remote transponder to deplete the energy store.

Claims

1. A method of transporting Radio Frequency (RF) energy to an RF transponder (RF tag, the RF tag comprising at least one tag antenna, a rectifying circuit connected to the tag antenna for receiving energy from the tag antenna, a tag energy store for storing the energy received from the rectifying circuit, tag electronics, and means for delivering energy from the tag energy store to the tag electronics, comprising the steps of:

(a) transporting for a first time RF electromagnetic wave energy from a base station having a base station antenna to the RF tag, the RF energy having a first frequency f₁ ;

then

(b) ceasing to transport RF energy during an off time t_o, where the off time t_o is less than a time where the RF tag loses one or more functions; and

then

(c) transporting for a second time RF electromagnetic wave energy from the base station to the RF tag, the RF energy having a second frequency f₂ different from the first frequency f₁, the tag antenna and the rectifying circuit of the RF tag being adapted for receiving power at frequencies f₁ and f₂.

2. The method of claim 1, wherein the off time t_o is greater than a time when a sideband of f₁ is generated, the sideband of f₁ having a frequency and power forbidden by government regulation.

3. The method of claim 1, wherein steps a to c are repeated with different frequencies f₁ and f₂.

4. The method of claim 3, wherein steps a to c are repeated a large number of times with a large plurality of different frequencies chosen in order from a randomly ordered list of different frequencies.

5. The method of claim 4, where the off time t_o is less than 400 milliseconds.

6. The method of claim 5, where the off time t_o is less than 400 microseconds.

7. The method of claim 6, where the off time t_o is less than 50 microseconds.

8. The method of claim 1, wherein the RF tag further comprises:

and independent source of energy; and

a switching means responsive to the RF energy transported to the tag adapted to connect the independent source of energy to the tag electronics when RF energy is transported to the tag.

9. The method of claim 8, wherein the switching means is controlled by a tag decision means responsive to the RF energy transported to the tag.

10. A method of transporting Radio Frequency (RF) energy to an RF transponder (RF tag, the RF tag comprising at least one tag antenna, a rectifying circuit connected to the tag antenna for receiving energy from the tag antenna, a tag energy store for storing the energy received from the rectifying circuit, tag electronics, and means for delivering energy from the tag energy store to the tag electronics, comprising the steps of:

a) determining a list of a large plurality of different frequencies;

b) transporting RF electromagnetic wave energy for a first time from a base station to the remote RF tag at a first frequency chosen from the list of large plurality of different frequencies;

c) ceasing to transport RF energy during an off time t_o, where the off time is less than a time where the tag loses one or more functions;

d) repeating steps b) and c) using frequencies chosen in order from the list.

11. The method of claim 10, wherein the list is a list of frequencies in pseudo random order.

12. The method of claim 11, wherein the tag antenna and the rectifying circuit of the remote RF tag are adapted to receive energy transmitted at each frequency of the list of frequencies in pseudo random order.

13. A base station for transporting Radio Frequency (RF) energy to an RF tag, the RF tag comprising at least one tag antenna, a rectifying circuit connected to the tag antenna for receiving energy from the tag antenna, a tag energy store for storing the energy received from the rectifying circuit, tag electronics, and means for delivering energy from the tag energy store to the tag electronics, comprising:

an RF generator for sending RF signal;

an RF amplifier/modulator for receiving the RF signal and for sending RF power to antenna; and

a computer, the computer controlling the RF generator to change from a first frequency f₁ to a second frequency f₂, the computer controlling the RF amplifier/modulator to reduce power sent to the antenna during the entire time the RF generator is changing from f₁ to f₂, where the time during which the power is reduced is less than the time where the RF tag energy store is depleted so that the tag electronics do not function.

14. The base station of claim 13, wherein the RF generator comprises:

a first RF generator for generating the frequency f₁ ;

a second RF generator for generating the frequency f₂ ; and

and RF switch, wherein the computer controls the RF switch to switch the input of the RF amplifier/modulator from the output of the first RF generator to the output of the second RF generator.

15. The bases station of claim 13, where the time during which the power is reduced is greater than a time when a sideband of f₁ is generated, the sideband of f₁ having a frequency and power forbidden by government regulation.

16. The base station of claim 13, where the time during which the power is reduced is less than 400 milliseconds.

17. The base station of claim 16, where the time during which the power is reduced is less than 400 microseconds.

18. The base station of claim 17, where the time during which the power is reduced is less than 50 microseconds.

19. A system for transporting RF energy from a base station to one or more remote RF tags, comprising:

an RF tag comprising at least one tag antenna, a rectifying circuit connected to the tag antenna for receiving energy from the tag antenna, a tag energy store for storing the energy received from the rectifying circuit, tag electronics, and means for delivering energy from the tag energy store to the tag electronics; and

a base station comprising an RF generator, and RF amplifier/modulator for sending RF power to an antenna; and

a computer, the computer controlling the RF generator to change from a first frequency f₁ to a second frequency f₂, the computer controlling the RF amplifier /modulator to reduce power sent to the antenna during the entire time the RF generator is changing from f₁ to f₂, where the time during which the power is reduced is less than the time where the RF tag loses one or more functions.

20. The system of claim 19, where the RF generator comprises:

a first RF generator for generating the frequency f₁ ;

a second RF generator for generating the frequency f₂ ;

an RF switch, wherein the computer controls the RF switch to switch the input of the RF amplifier/modulator from the output of the first RF generator to the output of the second RF generator.

21. The system of claim 19, where the time during which the power is reduced is greater than a time when a sideband of f₁ is generated, the sideband of f₁ having a frequency and power forbidden by government regulation.

22. The system of claim 19, where the time during which the power is reduced is less than 400 milliseconds.

23. The system of claim 22, where the time during which the power is reduced is less than 400 microseconds.

24. The system of claim 23, where the time during which the power is reduced is less than 50 microseconds.

25. The system of claim 19, where the RF generator comprises:

a first RF generator for generating the frequency f₁ ;

a second RF generator for generating the frequency f₂ ; and

an RF switch, wherein the computer controls the RF switch to switch the input of the RF amplifier/modulator from the output of the first RF generator to the output of the second RF generator.

26. A base station for transporting Radio Frequency (RF) energy to an RF tag, the RF tag comprising at least one tag antenna, a rectifying circuit connected to the tag antenna for receiving energy from the tag antenna, a tag energy store for storing the energy received from the rectifying circuit, tag electronics, and means for delivering energy from the tag energy store to the tag electronics, comprising:

an RF generator for sending an RF signal, where the RF generator comprises a first RF generator for generating a frequency f₁, a second RF generator for generating a frequency f₂, and an RF switch;

an RF amplifier/modulator for receiving the RF signal and for sending RF power to an antenna;

and

a computer, the computer controlling the RF generator to change from the first frequency f₁ to the second frequency f₂ controlling the RF switch to switch the input of the RF amplifier/modulator from the output of the first RF generator to the output of the second RF generator, the computer controlling the RF amplifier/modulator to reduce power sent to the antenna during the entire time the RF generator is changing from f₁ to f₂, where the time during which the power is reduced less than the time where the RF tag loses one or more functions.

27. A bases station for transporting Radio Frequency (RF) energy to an RF tag, the RF tag comprising at least one tag antenna, a rectifying circuit connected to the tag antenna for receiving energy from the tag antenna, a tag energy store for storing the energy received from the rectifying circuit, tag electronics, and means for delivering energy from the tag energy store to the tag electronics, comprising:

an RF generator for sending RF signal;

an RF amplifier/modulator for receiving the RF signal and for sending RF power to an antenna;

and

a computer, the computer controlling the RF generator to change from a first frequency f₁ to a second frequency f₂, the computer controlling the RF amplifier/modulator to reduce power sent to the antenna during the entire time the RF generator is changing from f₁ to f₂, where the time during which the power is reduced is less than the time where RF tag loses one or more functions and the time during which the power is reduced is greater than a time when a sideband of f₁ is generated, the sideband of f₁ having a frequency and power forbidden by government regulation.

28. A base station for transporting Radio Frequency (RF) energy to an RF tag, the RF tag comprising at least one tag antenna, a rectifying circuit connected to the tag antenna for receiving energy from the tag antenna, a tag energy store for storing the energy received from the rectifying circuit, tag electronics, and means for delivering energy from the tag energy store to the tag electronics, comprising:

an RF generator for sending an RF signal;

an RF amplifier/modulator for receiving the RF signal for sending RF power to an antenna;

and

a computer, the computer controlling the RF generator to change from a first frequency f₁ to a second frequency f₂, the computer controlling the RF amplifier/modulator to reduce power sent to the antenna during the entire time the RF generator is changing from f₁ to f₂, where the time during which the power is reduced is less than the time where the RF tag loses one or more functions and the time during which the power is reduced is less than 400 milliseconds.

29. The base station of claim 28, where the time during which the power is reduced is less than 400 microseconds.

30. The base station of claim 29, where the time during which the power is reduced is less than 50 microseconds.