Method And Circuit For Providing RF Isolation Of A Power Source From An Antenna And An RFID Device Employing Such A Circuit

• US 20090308936A1
• Filed: 04/16/2009
• Published: 12/17/2009
• Est. Priority Date: 10/17/2006
• Status: Active Grant

• Current Assignee: PowerID Ltd.
• Original Assignee: PowerID Ltd.
• Inventors: LAVEE, Doron, NITZAN, Zvi, ALMOG, Benyamin
• Granted Patent: US 8,162,230 B2
• Time in Patent Office: Days
• US Class Current: 235/492
• 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: 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 1/52 Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure absorbing means H01Q17/00

Abstract

An RFID device including:

• • electronic circuitry suitable for an RFID device comprising a radio frequency section;
  • an antenna;
  • a battery which provides the device with power; and
  • at least one quarter wavelength transmission line coupled between the battery and one or both of the electronic circuitry and the antenna.

Claims

1. An RFID device comprising:

(a) electronic circuitry suitable for an RFID device comprising a radio frequency section;

(b) an antenna;

(c) a battery which provides the device with power; and

(d) at least one quarter wavelength transmission line coupled between the battery and one or both of the electronic circuitry and the antenna.

2. A device according to claim 1, wherein said circuitry is mounted on a substrate.

3. The RFID device according to claim 2, wherein the transmission line is formed by one or more of a printing, a laminating, a depositing, a defusing or a placement process on the substrate or on an auxiliary substrate that is mounted on or proximate to the substrate of the device.

4. The RFID device according to claim 3, wherein the printing process of RF isolation is integrated with the printing process of the antenna and other conductors on the substrate of the RFID device.

5. The RFID device according to claim 1, wherein the circuitry includes RF isolation between two terminals thereof that receive power from said battery.

6. The RFID device according to claim 1, wherein the transmission line is formed of two parallel conductors that couple power from said battery to said one circuitry.

7. The RFID device according to claim 1, wherein the transmission line is formed of a single conductor used to couple power from said battery to said one circuitry, said conductor folded to form two parallel and shorted lines of the transmission line.

8. The RFID device according to claim 1, wherein the antenna is a high impedance antenna.

9. The RFID device according to claim 1, wherein the battery is a low-impedance battery.

10. The RFID device according to claim 1, wherein the at least one quarter wavelength transmission line is folded.

11. The RFID device according to claim 1, wherein the at least one quarter wavelength transmission line comprises at least one shorted quarter wavelength transmission line section.

12. The RFID device according to claim 11, wherein the RFID device includes only a single shorted quarter wavelength transmission line sections.

13. The RFID device according to claim 11, wherein said at least one quarter wavelength transmission line comprises two shorted quarter wavelength transmission line sections and wherein each of the two shorted quarter wavelength transmission line sections isolates one terminal of the battery to one terminal of the electronic circuitry.

14. The RFID device according to claim 1, wherein the electronic circuitry is a dedicated RFID ASIC.

15. The RFID device according to claim 1, wherein the circuitry includes a port connected to the antenna and the battery, which port is connected to said transmission line.

16. The RFID device according to claim 1, wherein the transmission line at least partly blocks RF leaks inside the circuitry from causing battery loading.

17. The RFID device according to claim 1, wherein said transmission line interconnects said battery to said antenna.

18. The RFID device according to claim 1, wherein the RFID device is a battery assisted passive RFID device or an active RFID device.

19. The RFID device according to claim 1, wherein the transmission line is formed from at least one conductor connecting said battery to said circuitry or said antenna.

20. The RFID device according to claim 1, wherein the transmission line is realized without adding components or assembly acts to said RFID device over a same device with same components and without a transmission line.

21. The RFID device according to claim 1, wherein the RFID device consists essentially of said antenna, said battery, said circuitry and said transmission line.

22. The RFID device according to claim 1, wherein the transmission line comprises an odd multiple of wavelength of the RFID device in effective length.

23. The RFID device according to claim 1, wherein the transmission line is wrapped, at least in part.

24. The RFID device according to claim 1, wherein said transmission line is a transmission line formed of two conductors, a first conductor which connects a terminal of said battery to said circuitry and a second conductor which connects a second terminal of said battery to said antenna and thereby to said circuitry.

25. The RFID device according to claim 24, wherein said transmission line is folded to form at least three sections and wherein said antenna is a dipole-type antenna.

26. The RFID device according to claim 1, wherein said transmission line is a shorted transmission line formed of a single conductor folded so two sections thereof are parallel and form a shorted transmission line two conductors, said single conductor connecting a terminal of said battery to said circuitry and also comprising a second conductor which connects a second terminal of said battery to said antenna and thereby to said circuitry.

27. The RFID device according to claim 26, wherein said second conductor is also formed into a shorted transmission line.

28. A method of RF isolating a power source in an RFID device, comprising connecting a power source to one or both of electronic circuitry and an antenna via at least one quarter wavelength transmission line.

29. The method according to claim 28, including printing or otherwise depositing a transmission line and a battery serving at least partially as said power source on a same or different substrate of the device.

30. The method according to claim 28, including compensating for an RF interaction between the circuitry, battery and antenna by said transmission line.

31. A method of RFID device design, comprising:

(a) providing an RFID circuit without separable RF isolation elements; and

(b) selecting a battery having an internal resistance high enough to avoid degradation of more than 4 dB in a circuit using the battery.