Tuning techniques for a slot antenna

• US 6,642,897 B2
• Filed: 04/18/2002
• Issued: 11/04/2003
• Est. Priority Date: 03/25/2000
• Status: Expired

• Current Assignee: Mineral Lassen LLC (Intellectual Ventures LLC)
• Original Assignee: Marconi Communications, Inc. (Marconi Holdings Company Limited)
• Inventors: Forster, Ian J., Horrell, Peter Robert George
• Primary Examiner(s): NGUYEN, HOANG V
• Application Number:
  US10/125,786
• Publication Number:
  US 20030058180A1
• Time in Patent Office: 565 Days
• Field of Search: 343/767, 343/746, 340/539, 340/540, 340/825, 340/572
• US Class Current: 343/767
• CPC Class Codes: B65D 2203/10 Transponders
• CPC Class Codes: B65D 25/205 Means for the attachment of labels, cards, coupons or the like; cards or coupons for the other types of rigid or semi-rigid containers B65D25/36 takes precedence
• CPC Class Codes: G06K 19/041 Constructional details G06K19/06 takes precedence
• 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: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• 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 1/44 using equipment having another main function to serve additionally as an antenna , e.g. means for giving an antenna an aesthetic aspectH01Q1/27 - H01Q1/34 take precedence
• CPC Class Codes: H01Q 13/10 Resonant slot antennas
• CPC Class Codes: H01Q 13/12 Longitudinally slotted cylinder antennas; Equivalent structures
• CPC Class Codes: H01Q 13/18 the slot being backed by, or formed in boundary wall of, a resonant cavity longitudinally slotted cylinder H01Q13/12 ; Open cavity antennas

Abstract

A wireless communication device and method for identifying a container, or communication information about a container, using a slot in the container as an antenna. The device includes a wireless communication device for transmitting information regarding the container. The container includes an outer wall forming a rim and a slot between the rim edge and the outer wall that is circular and continues without boundaries. The wireless communication device is coupled to the slot to provide the slot antenna for communications. An impedance matching network is additionally provided to make the operating frequency of the slot substantially the same as the operating frequency of the wireless communication device. Alternatively, shorting posts may be placed in the slot to define boundaries of the slot to match the operating frequency of the slot to the operating frequency of the antenna. Variable impedance matching is provided between the wireless communication device and the slot.

Claims

1. A device for identifying a container having a slot, comprising:

a wireless communication device mounted on the container to communicate remotely information associated with the container;

a slot antenna formed by electronically associating said wireless communication device to the slot; and

a variable reactance element including sub-elements whose proximity changes as a function of changes in a width associated with the slot, thereby changing reactance characteristics of said slot antenna.

2. The device of claim 1, wherein said variable reactance element is a variable capacitor.

3. The device of claim 2, wherein said variable capacitor'"'"'s capacitance increases as the width associated with the slot decreases.

4. The device of claim 2, wherein the variable capacitor'"'"'s capacitance decreases as the width associated with the slot decreases.

5. The device of claim 2, wherein said variable capacitor includes two parallel plates positioned on flanges.

6. The device of claim 1, wherein said variable reactance element is a variable inductor.

7. The device of claim 6, wherein said variable inductor includes a helical coil having loops, said loops comprising said sub-elements.

8. The device of claim 6, wherein the variable inductor'"'"'s inductance increases as the width associated with the slot decreases.

9. The device of claim 6, wherein the variable inductor'"'"'s inductance decreases as the width associated with the slot decreases.

10. The device of claim 1, wherein the slot is formed from a rim edge and an outer wall.

11. The device of claim 10, wherein said variable reactance element comprises a clip positioned between said rim edge and said outer wall.

12. A system for identifying a container, comprising:

a container having a slot;

a wireless communication device mounted on the container to communicate remotely information associated with the container;

a slot antenna formed by electronically associating said wireless communication device to said slot, said slot antenna having a variable impedance as a function of a width associated with the slot; and

an impedance matching network including a variable reactance element associated with said wireless communication device, said impedance matching network matching impedances between said slot antenna and said wireless communication device.

13. The system of claim 12, wherein said variable reactance element comprises a variable capacitor.

14. The system of claim 13, wherein said variable capacitor increases capacitance as said width decreases.

15. The system of claim 13, wherein said variable capacitor decreases capacitance as said width decreases.

16. The system of claim 12, wherein said variable reactance element comprises a variable inductor.

17. The system of claim 16, wherein said variable inductor increases inductance as said width decreases.

18. The system of claim 16, wherein said variable inductor decreases inductance as said width decreases.

19. A method of monitoring a container comprising:

associating a wireless communication device with the container;

moving the container through at least one interrogation point containing an interrogation reader;

communicating monitoring information associated with the container between said wireless communication device and said interrogation reader through a slot antenna formed by a slot within the container; and

matching impedances between said slot antenna and said wireless communication device with an impedance matching network.

20. The method of claim 19, wherein matching impedances comprises varying a variable reactance element within said impedance matching network.

21. The method of claim 20, wherein varying a variable reactance element comprises varying a variable capacitor.

22. The method of claim 21, wherein varying a variable capacitor comprises compressing two parallel plates as a width associated with said slot decreases.

23. The method of claim 21, wherein varying a variable capacitor comprises moving two parallel plates from substantially overlapped positions to positions where said parallel plates have less overlapping areas as a width associated with said slot decreases.

24. The method of claim 20, wherein varying a variable reactance element comprises varying a variable inductor.

25. The method of claim 24, wherein varying a variable inductor comprises compressing a helical coil, as a width associated with said slot decreases.

26. The method of claim 24, wherein varying a variable inductor comprises spreading a helical coil, as a width associated with said slot decreases.

27. The method of claim 19, wherein matching impedances comprises varying at least one variable reactance element within said impedance matching network.

28. The method of claim 19, wherein matching impedances comprises varying a plurality of variable reactance elements within said impedance matching network.