Passive Transponder and an Item with a Passive Transponder

• US 20090272814A1
• Filed: 05/05/2009
• Published: 11/05/2009
• Est. Priority Date: 05/05/2008
• Status: Abandoned Application

• Current Assignee: Recco Systems AB
• Original Assignee: Recco Systems AB
• Inventors: Forssen, Karl-Gosta, Granhed, Magnus
• Application Number:
  US12/435,469
• Publication Number:
  US 20090272814A1
• Time in Patent Office: Days
• US Class Current: 235/492
• CPC Class Codes: G06K 19/067 Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components

Abstract

A passive transponder includes an antenna having two electrically conductive parts; a diode connected to the antenna; and a transmission line connected to the antenna and to the diode. The transmission line is adapted to match the impedance of the diode to an impedance of the antenna. The passive transponder, when hit by radio frequency (RF) power of a first frequency f₁, retransmits RF power of a harmonic frequency f_h. Each electrically conductive part of the antenna includes a flexible conductive thread having a first end and a second end, and the diode is connected to a first end of the flexible conductive thread. An item, such as a fabric or adhesive label, includes at least one passive transponder.

Claims

1. A passive transponder, comprising:

an antenna having two electrically conductive parts, wherein each electrically conductive part of the antenna comprises a flexible conductive thread having a first end and a second end;

a diode electrically connected to a first end of the flexible conductive thread of the antenna; and

a transmission line connected to the antenna and to the diode, wherein the transmission line is adapted to match the impedance of the diode to an impedance of the antenna; and

the passive transponder, when hit by radio frequency (RF) power of a first frequency f₁, retransmits RF power of a harmonic frequency f_h.

2. The passive transponder of claim 1, wherein each electrically conductive part is provided with at least one thin flexible narrow foil strip electrically connected to the second end of the flexible conductive thread.

3. The passive transponder of claim 1, wherein each electrically conductive part is provided with at least one additional flexible conductive thread electrically connected to a point on the flexible conductive thread situated between the first end and the second end of the flexible conductive thread.

4. The passive transponder of claim 1, wherein the flexible conductive threads are insulated metal wires.

5. The passive transponder of claim 1, wherein the flexible conductive threads are configured to be integrated into a fabric.

6. The passive transponder of claim 5, wherein the transmission line is a conductive thread configured to be integrated into the fabric.

7. The passive transponder of claim 1, wherein the harmonic frequency f_h is twice the first frequency f₁.

8. The passive transponder of claim 1, wherein the passive transponder is enclosed in a dielectric material to reduce an influence of surroundings of the passive transponder on a near field of the antenna.

9. The passive transponder of claim 8, wherein the dielectric material is a biocompatible material.

10. The passive transponder of claim 1, further comprising an adhesive layer.

11. An item including at least one passive transponder according to claim 1.

12. The item of claim 11, wherein the item is a flexible sheet of material, and the at least one passive transponder is attached to a surface of the flexible sheet of material.

13. The item of claim 11, wherein the item is an adhesive label.

14. The item of claim 11, wherein the item is a fabric.

15. The item of claim 14, wherein the fabric is absorbent and adapted to be used for absorbing fluids.

16. The item of claim 14, wherein the at least one passive transponder is embedded in the fabric.

17. The item of claim 16, wherein each passive transponder is arranged at an edge of the fabric.

18. The item of claim 14, wherein the at least one passive transponder is integrated in the fabric.

19. The item of claim 18, wherein the transmission line and the antenna of each passive transponder include conductive threads arranged within the fabric.

20. The item of claim 14, wherein the passive transponder is coated with a flexible biocompatible material.

21. The item of claim 14, wherein the fabric is formed into an arbitrary shape.

22. The item of claim 14, wherein the fabric is formed into a shape of a compress or a tamponade.