Transponder modules, RF tagging system, method of operating a transponder module and methods of tagging an object having a conductive surface

• US 6,236,314 B1
• Filed: 09/02/1999
• Issued: 05/22/2001
• Est. Priority Date: 09/02/1999
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Khatri, Dirgha, Smith, Freddie W.
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US09/388,560
• Time in Patent Office: 628 Days
• Field of Search: 340/572.7, 340/572.1, 340/505, 340/10.1, 343/700.MS, 343/878, 343/850, 343/857, 342/51
• US Class Current: 340/572.7
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal
• 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 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07786 the antenna being of the HF type, such as a dipole
• 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: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2431 Tag circuit details
• CPC Class Codes: G08B 13/2485 Simultaneous detection of multiple EAS tags
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 9/0421 with a shorting wall or a shorting pin at one end of the element H01Q9/0414 takes precedence

Abstract

A transponder module includes a circuit board having top and bottom surfaces and an inverted-F receive antenna formed on the circuit board. The receive antenna includes a ground plane formed on one of the surfaces and an active element formed above the ground plane. The module also includes a RF engine having an input coupled to the receive antenna, an output and a power supply input. The module additionally includes a RF decoupling network having first and second ports. The first port is coupled to the output of the RF engine. The module further includes an inverted-F backscatter antenna coupled to the second port of the RF decoupling network. The backscatter antenna includes a second ground plane formed on one of the surfaces and a second active element formed above the second ground plane. A method of tagging an object having a conductive surface includes coupling a transponder module including a low profile antenna to the conductive surface such that a ground plane contained in the transponder module is adjacent the conductive surface of the object and transmitting a signal from the low profile antenna to an interrogator, the signal including information relevant to the object.

Claims

1. A transponder module comprising:

a circuit board having first and second surfaces;

a ground plane formed on the first surface;

a low profile receive antenna formed on the circuit board over the ground plane;

a RF engine having an input coupled to the receive antenna, an output and a power supply input;

a RF decoupling network having first and second ports, the first port coupled to the output of the RF engine;

a second ground plane formed on the first surface; and

a low profile backscatter antenna coupled to the second port of the RF decoupling network, the backscatter antenna formed over the second ground plane.

2. The module of claim 1, further comprising a button-type battery having a first electrode coupled to the ground plane and a second electrode coupled to the power supply input to the RF engine.

3. The module of claim 1, wherein the RF engine comprises a small outline integrated circuit.

4. The module of claim 1, wherein the ground plane and the second ground plane are separated and isolated from each other by a gap, and the RF decoupling network is spaced apart from the second ground plane adjacent the gap.

5. The module of claim 1, wherein:

the low profile receive antenna comprises an inverted-F receive antenna; and

the low profile backscatter antenna comprises an inverted-F backscatter antenna.

6. The module of claim 1, wherein the RF decoupling network comprises:

a PIN diode having first and second terminals;

a first coil having first and second terminals, the first terminal coupled to the RF engine, the second terminal coupled to the first terminal of the PIN diode and to the backscatter antenna;

a second coil having first and second terminals, the first terminal coupled to the RF engine, the second terminal coupled to the second terminal of the PIN diode; and

a capacitor having a first terminal coupled to the second terminal of the PIN diode and a second terminal coupled to the second ground plane.

7. The module of claim 1, wherein the receive antenna includes an active element that is one-fourth of a wavelength in length.

8. The module of claim 1, wherein the backscatter antenna includes an active element that is less than one-fourth of a wavelength in length.

9. A transponder module comprising:

a circuit board having top and bottom surfaces;

an inverted-F receive antenna formed on the circuit board, the receive antenna including a ground plane formed on one of the surfaces and an active element formed on another of the surfaces above the ground plane;

a RF engine having an input coupled to the receive antenna, an output and a power supply input;

a RF decoupling network having first and second ports, the first port coupled to the output of the RF engine; and

an inverted-F backscatter antenna coupled to the second port of the RF decoupling network, the backscatter antenna including a second ground plane formed on one of the surfaces and a second active element formed above the second ground plane.

10. The module of claim 9, further comprising a button-type battery having a first electrode coupled to the ground plane and a second electrode coupled to the power supply input to the RF engine.

11. The module of claim 9, wherein the RF engine comprises a small outline integrated circuit.

12. The module of claim 9, wherein the ground plane and the second ground plane are separated and isolated from each other by a gap, and the RF decoupling network is placed entirely above the second ground plane adjacent the gap.

13. The module of claim 9, wherein the ground plane and the second ground plane are electrically isolated from each other.

14. The module of claim 9, wherein the RF decoupling network comprises:

a PIN diode having first and second terminals;

a first coil having first and second terminals, the first terminal coupled to the RF engine, the second terminal coupled to the first terminal of the PIN diode and to the second active element of the backscatter antenna;

a second coil having first and second terminals, the first terminal coupled to the RF engine, the second terminal coupled to the second terminal of the PIN diode; and

a capacitor having a first terminal coupled to the second terminal of the PIN diode and a second terminal coupled to the second ground plane.

15. The module of claim 9, wherein the receive antenna active element is one-fourth of a wavelength in length.

16. The module of claim 9, wherein the backscatter antenna active element is less than one-fourth of a wavelength in length.

17. A RF tagging system comprising:

an interrogation unit for transmitting interrogation signals and receiving backscattered signals in response to the interrogation signals; and

a transponder module including;

a circuit board having top and bottom surfaces;

a first ground plane formed on one of the surfaces;

a low profile receive antenna formed on the circuit board above the first ground plane;

a RF engine having an input coupled to the receive antenna, an output and a power supply input;

a RF decoupling network having first and second ports, the first port coupled to the output of the RF engine;

a second ground plane formed on one of the surfaces; and

a low profile backscatter antenna formed on the circuit board above the second ground plane, the backscatter antenna coupled to the second port of the RF decoupling network.

18. The tagging system of claim 17, wherein the receive antenna includes an active element formed above the first ground plane.

19. The tagging system of claim 17, wherein the backscatter antenna includes an active element formed above the second ground plane.

20. The tagging system of claim 17, wherein the receive antenna includes a first active element formed above the first ground plane, and the backscatter antenna includes a second active element formed above the second ground plane.

21. The tagging system of claim 20, wherein the RF decoupling network comprises:

a PIN diode having first and second terminals;

a first coil having first and second terminals, the first terminal coupled to the RF engine, the second terminal coupled to the first terminal of the PIN diode and to the second active element of the backscatter antenna;

a second coil having first and second terminals, the first terminal coupled to the RF engine, the second terminal coupled to the second terminal of the PIN diode; and

a capacitor having a first terminal coupled to the second terminal of the PIN diode and a second terminal coupled to the second ground plane.

22. The tagging system of claim 20, wherein the first ground plane and the second ground plane are separated and isolated from each other by a gap, and the RF decoupling network is placed entirely above the second ground plane adjacent the gap.

23. The tagging system of claim 17, wherein the low profile receive and backscatter antennas each have a height above the circuit board of about five percent of the wavelength of the antennas.

24. The tagging system of claim 17 wherein the receive antenna and the backscatter antenna each comprise an inverted-F antenna.

25. A method of operating a transponder module comprising:

receiving an interrogation signal by an inverted-F antenna contained within the transponder module; and

transmitting a modulated backscattered response signal from a backscatter inverted-F antenna contained within the transponder module in response to the received interrogation signal.

26. The method of claim 25 further comprising mounting the transponder module such that a ground plane contained in the transponder module is adjacent a conductive surface of an object corresponding to the transponder module.

27. The method of claim 25 further comprising transmitting data describing an object to which the transponder module is coupled.

28. The method of claim 25 further comprising mounting the transponder module such that a ground plane contained in the transponder module is adjacent a high dielectric constant surface of an object corresponding to the transponder module.