METHODS AND SYSTEMS OF CHANGING ANTENNA POLARIZATION

• US 20080266192A1
• Filed: 04/26/2007
• Published: 10/30/2008
• Est. Priority Date: 04/26/2007
• Status: Active Grant

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Tuttle, John R.
• Granted Patent: US 7,825,867 B2
• Time in Patent Office: Days
• US Class Current: 343/756
• 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 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• 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

Methods and systems of changing antenna polarization. At least some of the illustrative embodiments are systems comprising an antenna having a first feed point and a second feed point, an antenna communication circuit, and a switch assembly that selectively couples the antenna communication circuit to the first feed point, and that selectively couples the antenna communication circuit to the second feed point. The feed point (or group of feed points) is selected, for example, based on polarization of an electromagnetic wave to be radiated from or received by the antenna.

Claims

1. A system comprising:

an antenna having a first feed point and a second feed point;

an antenna communication circuit;

a switch assembly that selectively couples the antenna communication circuit to the first feed point, and that selectively couples the antenna communication circuit to the second feed point.

2. The system according to claim 1 further comprising:

wherein the antenna communication circuit is configured to produce an antenna feed signal;

wherein the antenna radiates an electromagnetic wave having a first polarization when the antenna feed signal is applied to the first feed point to the exclusion of the second feed point; and

wherein the antenna radiates an electromagnetic wave having a second polarization different than the first polarization when the antenna feed signal is applied to the second feed point.

3. The system according to claim 2 wherein first polarization is one or more selected from the group consisting of:

vertical polarization;

horizontal polarization;

right-circular polarization;

or left circular polarization.

4. The system according to claim 1 further comprising:

wherein the antenna communication circuit is configured to selectively tune and de-tune the antenna;

wherein the antenna transmits an electromagnetic wave having a first polarization when the antenna is selectively tuned and de-tuned is with respect to the first feed point to the exclusion of the second feed point; and

wherein the antenna transmits an electromagnetic wave having a second polarization different than the first polarization when the antenna is selectively tuned and de-tuned is with respect to the second feed point.

5. The system according to claim 1 further comprising:

wherein the antenna is configured to produce an electrical signal proportional to electromagnetic radiation incident upon the antenna;

wherein when the electrical signal is conducted between the first feed point and the antenna communication circuit, the electrical signal is predominantly proportional to electromagnetic radiation incident on the antenna having a first polarization; and

wherein when the electrical signal is conducted between the second feed point and the antenna communication circuit, the electrical signal is predominantly proportional to electromagnetic radiation incident on the antenna having a second polarization.

6. The system according to claim 5 wherein first polarization is one or more selected from the group consisting of:

vertical polarization;

horizontal polarization;

right-circular polarization;

or left circular polarization.

7. The system according to claim 1 wherein the switch assembly further comprises a mechanical switch whose switch positions are changed by physical manipulation.

8. The system according to claim 1 wherein the switch assembly further comprises an electrically controlled switch.

9. The system according to claim 8 wherein switch assembly is one or more selected from the group consisting of:

solenoid operated relay;

field effect transistor;

junction transistor; and

silicon controlled rectifier pair.

10. The system according to claim 1 wherein the antenna communication circuit controls the switch position of each of the first and second switches.

11. The system according to claim 1 wherein the antenna further comprises:

an antenna element that defines a perimeter; and

a ground plane, the radiative patch suspended over the ground plane;

wherein the first and second feed points are one or more selected from the group consisting of;

within the perimeter; and

disposed on the perimeter.

12. The system according to claim 11 the antenna further comprising a dielectric material disposed between the radiative element and the ground plane.

13. The system according to claim 1 wherein the antenna communication circuit is one or more selected from the group consisting of:

a radio frequency identification (RFID) reader; and

a RFID circuit within an RFID tag.

14. A method comprising:

transmitting an electromagnetic wave with a first polarization by applying a time-varying electrical signal to a first feed point of an antenna; and

transmitting an electromagnetic wave with a second polarization different from the first polarization, the transmitting the second electromagnetic wave by applying a time-varying electrical signal to a second feed point of the antenna and not the first feed point.

15. The method according to claim 14 wherein transmitting the electromagnetic wave with the first polarization further comprises applying a time-varying electrical signal to the first feed point and not the second feed point.

16. The method according to claim 14 wherein transmitting the electromagnetic wave with the first polarization further comprises coupling the time-varying electrical signal to the first feed point by way of a switch assembly.

17. The method according to claim 14 wherein transmitting the electromagnetic wave with the first polarization further comprises coupling the time-varying electrical signal to the first feed point by way of one or more selected from the group consisting of:

a mechanical switch;

a solenoid operated relay;

a field effect transistor;

a junction transistors; and

a silicon controlled rectifier pair.

18. The method according to claim 14 wherein transmitting the electromagnetic wave with the first polarization further comprises transmitting an interrogating signal to a radio frequency identification (RFID) tag.

19. The method according to claim 14 wherein transmitting the electromagnetic wave with the first polarization further comprises transmitting a response to an interrogating signal, the response from a radio frequency identification (RFID) tag.

20. The method according to claim 14 further comprising:

wherein transmitting the electromagnetic wave with the first polarization further comprises transmitting from an antenna element of a patch antenna, the first feed point within an area defined by the antenna element; and

wherein transmitting the electromagnetic wave with the second polarization further comprises transmitting from the antenna element of the patch antenna, the second feed point within the area defined by the antenna element.

21. The method according to claim 14 wherein transmitting the electromagnetic wave with the first polarization further comprises transmitting the electromagnetic wave with the first polarization being one or more selected from the group consisting of:

vertical polarization;

horizontal polarization;

right-circular polarization; and

left-circular polarization.

22. A system comprising:

a reading antenna having a first feed point associated with a first polarization of the reading antenna, and the reading antenna having a second feed point associated with a second polarization of the reading antenna;

a radio frequency identification (RFID) reader circuit;

a switch assembly that selectively couples the RFID reader circuit to the first feed point; and

that selectively couples the RFID reader circuit to the second feed point.

23. The system to claim 22 further comprising:

wherein the RFID reader circuit is configured to generate an interrogation signal;

and

wherein when the interrogation signal is applied to the reading antenna through the first feed point the reading antenna produces electromagnetic radiation with the first polarization; and

wherein when the interrogation signal is applied to the reading antenna through the second feed point the reading antenna produces electromagnetic radiation with the second polarization.

24. The system according to claim 23 wherein when the interrogation signal is applied to the first feed point, the interrogation signal is not applied to the second feed point.

25. The system according to claim 24 wherein when the interrogation signal is applied to the second feed point, the interrogation signal is not applied the first feed point.

26. The system according to claim 22 further comprising:

wherein the RFID reader circuit is configured to receive an electrical signal from the reading antenna, the electrical signal proportional to electromagnetic radiation incident upon the reading antenna; and

wherein when the electrical signal is received through first feed point, the electrical signal is predominantly proportional to electromagnetic radiation incident on the reading antenna having the first polarization; and

wherein when the electrical signal is received through second feed point, the electrical signal is predominantly proportional to electromagnetic radiation incident on the reading antenna having the second polarization.

27. The system according to claim 22 wherein the RFID reader circuit controls the switch position of each of the first and second switches.

28. A radio frequency identification (RFID) tag comprising:

a tag antenna;

a RFID circuit;

a switch assembly that selectively couples the RFID circuit to a first feed point of the tag antenna, and than selectively couples the RFID circuit to a second feed point of the tag antenna;

wherein the first feed point is associated with a first polarization of the tag antenna, and the second feed point is associated with a second polarization of the tag antenna different than the first polarization.

29. The RFID tag to claim 28 further comprising:

wherein the RFID circuit is configured to generate responsive signal, the responsive signal responsive to an interrogation of the RFID tag; and

wherein when the responsive signal is applied to the tag antenna by way of the first feed point the tag antenna produces electromagnetic radiation with the first polarization; and

wherein when the responsive signal is applied to the tag antenna through the second feed point the tag antenna produces electromagnetic radiation with the second polarization.

30. The RFID tag according to claim 29 wherein when the responsive signal is applied to the first feed point, the responsive signal is not applied to the second feed point.

31. The RFID tag according to claim 30 wherein when the responsive signal is applied to the second feed point, the responsive signal is not applied the first feed point.

32. The system according to claim 28 further comprising:

wherein RFID circuit is configured to selectively tune and de-tune the tag antenna;

wherein the tag antenna transmits an electromagnetic wave having a first polarization when the antenna is selectively tuned and de-tuned is with respect to the first feed point to the exclusion of the second feed point; and

wherein the tag antenna transmits an electromagnetic wave having a second polarization different than the first polarization when the tag antenna is selectively tuned and de-tuned is with respect to the second feed point.

33. The RFID tag according to claim 28 further comprising:

wherein the RFID tag is configured to receive an interrogating signal from the tag antenna, the interrogating signal proportional to interrogating electromagnetic radiation incident upon the tag antenna; and

wherein when the interrogating signal is received by way of first feed point, the interrogating signal is predominantly proportional to interrogating electromagnetic radiation incident on the tag antenna having the first polarization; and

wherein when the interrogating signal is received by way of the second feed point, the interrogating signal is predominantly proportional to electromagnetic radiation incident on the tag antenna having the second polarization.

34. The RFID tag according to claim 28 wherein the RFID reader circuit controls the switch position of each of the first and second switches.

35. A system comprising:

an antenna having a feed point, a first ground point and a second ground point;

an antenna communication circuit coupled to the feed point;

a switch assembly that selectively couples the first point to a ground, and that selectively couples the second ground point to the ground.

36. The system according to claim 35 further comprising:

wherein the antenna radiates an electromagnetic wave having a first polarization when the switch assembly couples the first ground point to the ground; and

wherein the antenna radiates an electromagnetic wave having a second polarization different than the first polarization when the switch assembly couples the second ground point to the ground.

37. The system according to claim 35 further comprising:

wherein the antenna is configured to produce an electrical signal conducted between the feed point and the antenna communication circuit when an electromagnetic radiation is incident upon the antenna;

wherein when the first ground point is coupled to the ground, the electrical signal is predominantly proportional to electromagnetic radiation incident on the antenna having a first polarization; and

wherein when the second ground point is coupled to the ground, the electrical signal is predominantly proportional to electromagnetic radiation incident on the antenna having a second polarization.

38. The system according to claim 35 wherein the antenna communication circuit is one or more selected from the group consisting of:

a radio frequency identification (RFID) reader; and

a RFID circuit within an RFID tag.

39. A method comprising:

applying a time varying electrical signal to a feed point of an antenna;

transmitting from the antenna an electromagnetic wave with a first polarization by coupling a first ground point of the antenna to ground; and

transmitting from the antenna an electromagnetic wave with a second polarization different from the first polarization, the transmitting the second electromagnetic wave by coupling a second ground point of the antenna to ground.

40. The method according to claim 39 wherein transmitting the electromagnetic wave with the first polarization further comprises coupling the first ground point, but not the second ground point, to ground.

41. The method according to claim 39 wherein transmitting the electromagnetic wave with the first polarization further comprises one or more selected from the group consisting of:

transmitting an interrogating signal to a radio frequency identification (RFID) tag; and

transmitting a response to an interrogating signal, the response from a radio frequency identification (RFID) tag.