Antenna system including simultaneous phase aiding and phase canceling elements

• US 20050162276A1
• Filed: 05/27/2004
• Published: 07/28/2005
• Est. Priority Date: 06/16/2003
• Status: Active Grant

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Semsormatic Electronics Corporation
• Inventors: Balch, Brent F., O'Connell, John, Spalding, Tom, Hurd, William H.
• Granted Patent: US 7,023,346 B2
• Time in Patent Office: Days
• US Class Current: 340/572.700
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes precedence
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 7/04 Screened antennas H01Q7/02, H01Q7/06 take precedence
• CPC Class Codes: H01Q 7/06 with core of ferromagnetic material H01Q7/02 takes precedence

Abstract

A system for minimizing the effect of null zones in an interrogation zone of a marker detection system. The system includes a reference antenna system configured to produce a first reference electromagnetic field during a first time period. The antenna system also includes a phase canceling antenna system configured to produce a second electromagnetic field substantially in phase with the reference electromagnetic field during the first time period and a third electromagnetic field substantially out of phase with the reference electromagnetic field during the first time period. The phasing of the first field or the second and third fields may be continuously switched while the phase of the other is held constant. A method of spatially shifting null zones in an interrogation zone of a marker detection system is also provided.

Claims

1. An antenna system comprising:

a reference antenna system configured to produce a first reference electromagnetic field during a first time period; and

a phase canceling antenna system configured to produce a second electromagnetic field substantially in phase with said first reference electromagnetic field during said first time period while also producing a third electromagnetic field substantially out of phase with said first reference electromagnetic field during said first time period.

2. The antenna system of claim 1, wherein said reference antenna system is configured to produce said first reference electromagnetic field during a second time period, and wherein said phase canceling antenna system is configured to produce a fourth electromagnetic field during said second time period, said fourth electromagnetic field being substantially out of phase with said first reference electromagnetic field, and wherein said phase canceling antenna is configured to produce a fifth electromagnetic field during said second time period, said fifth electromagnetic field being substantially in phase with said first reference electromagnetic field.

3. The antenna system of claim 2, wherein said phase canceling antenna system is configured to said second and third electromagnetic fields alternately with said fourth and fifth electromagnetic fields.

4. The antenna system of claim 1, wherein said phase canceling antenna system is configured to produce said second and third electromagnetic fields during a second time period, and wherein said reference antenna system is configured to produce a second reference electromagnetic field during said second time period, said second reference electromagnetic field being substantially out of phase with said second electromagnetic field and substantially in phase with said third electromagnetic field.

5. The antenna system of claim 4, wherein said reference antenna system is configured to alternately produce said first and second reference electromagnetic fields.

6. The antenna system of claim 1, wherein said reference antenna system comprises a reference loop antenna for producing said first reference electromagnetic field, and wherein said phase canceling antenna system comprises a first phase canceling loop antenna and a second phase canceling loop antenna, said first loop antenna configured to produce said second electromagnetic field and said second loop antenna configured to produce said third electromagnetic field.

7. The antenna system of claim 6, wherein said reference loop antenna and said first and second phase canceling loop antennas lie substantially in a common plane.

8. The antenna system of claim 6, wherein said reference loop antenna defines a reference aperture and wherein said first phase canceling loop antenna and said second phase canceling loop antenna are disposed at least partially in said reference aperture.

9. The antenna system of claim 6, wherein said reference loop antenna is disposed between said first phase canceling loop antenna and said second phase canceling loop antenna.

10. The antenna system of claim 6, wherein said first phase canceling loop antenna and said second phase canceling loop antenna are symmetrically disposed about a centerline axis of said reference loop antenna, said centerline axis bisecting said reference loop antenna.

11. The antenna system of claim 1, wherein said reference antenna system comprises a reference magnetic core antenna for producing said first reference electromagnetic field, and wherein said phase canceling antenna system comprises a first phase canceling magnetic core antenna for producing said second electromagnetic field and a second phase canceling magnetic core antenna for producing said third electromagnetic field.

12. The antenna system of claim 11, wherein said reference magnetic core antenna is configured to produce said first reference electromagnetic field during a second time period, and wherein said first phase canceling magnetic core antenna is configured to produce a fourth electromagnetic field during said second time period, said fourth electromagnetic field being substantially out of phase with said first reference electromagnetic field, and wherein said second phase canceling magnetic core antenna is configured to produce a fifth electromagnetic field during said second time period, said fifth electromagnetic field being substantially in phase with said first reference electromagnetic field.

13. The antenna system of claim 12, wherein said phase canceling antenna system is configured to produce said second and third electromagnetic fields alternately with said fourth and fifth electromagnetic fields.

14. The antenna system of claim 11, wherein said phase canceling antenna system is configured to produce said second and third electromagnetic fields during a second time period, and wherein said reference magnetic core antenna is configured to produce a second reference electromagnetic field during said second time period, said second reference electromagnetic field being substantially out of phase with said second electromagnetic field and substantially in phase with said third electromagnetic field.

15. The antenna system of claim 14, wherein said reference antenna system is configured to alternately produce said first and second reference electromagnetic fields.

16. The antenna system of claim 1, said system further comprising:

at least one controller configured to provide a first excitation signal and a second excitation signal during said first time period;

said reference antenna system being responsive to said first excitation signal to produce said first electromagnetic field; and

said phase canceling antenna system being responsive to said second excitation signal to produce said second electromagnetic field and said third electromagnetic field.

17. An antenna system comprising:

at least one controller configured to provide a first excitation signal and a second excitation signal;

a reference antenna responsive to said first excitation signal to produce a first electromagnetic field; and

a phase canceling antenna system responsive to said second excitation signal to produce a second electromagnetic field substantially in phase with said first reference electromagnetic field while also producing a third electromagnetic field substantially out of phase with said first reference electromagnetic field,

said controller being configured to periodically reverse a polarity of one of said first excitation signal and said second excitation signal while maintaining a polarity of the other of said first excitation signal and said second excitation signal.

18. The antenna system of claim 17, wherein said reference antenna comprises a reference loop antenna for producing said first reference electromagnetic field, and wherein said phase canceling antenna system comprises a first phase canceling loop antenna and a second phase canceling loop antenna, said first loop antenna configured to produce said second electromagnetic field and said second loop antenna configured to produce said third electromagnetic field.

19. The antenna system of claim 18, wherein said reference loop antenna and said first and second phase canceling loop antennas lie substantially in a common plane.

20. The antenna system of claim 18, wherein said reference loop antenna defines a reference aperture and wherein said first phase canceling loop antenna and said second phase canceling loop antenna are disposed at least partially in said reference aperture.

21. The antenna system of claim 18, wherein said reference loop antenna is disposed between said first phase canceling loop antenna and said second phase canceling loop antenna.

22. The antenna system of claim 18, wherein said first phase canceling loop antenna and said second phase canceling loop antenna are symmetrically disposed about a centerline axis of said reference loop antenna, said centerline axis bisecting said reference loop antenna.

23. The antenna system of claim 17, wherein said reference antenna system comprises a reference magnetic core antenna for producing said first reference electromagnetic field, and wherein said phase canceling antenna system comprises a first phase canceling magnetic core antenna for producing said second electromagnetic field and a second phase canceling magnetic core antenna for producing said third electromagnetic field.

24. A method of spatially shifting null zones in an interrogation zone of a marker detection system, said method comprising:

producing first, second, and third electromagnetic fields, one of said second and third electromagnetic fields being substantially in phase with said first electromagnetic field and the other of said second and third electromagnetic fields being substantially out of phase with said first electromagnetic field; and

reversing the phase of one of said first magnetic field and said second and third electromagnetic fields while maintaining the phase of the other one of said first magnetic field and said second and third electromagnetic fields.

25. A method according to claim 24, wherein said reversing the phase of one of said first magnetic field and said second and third electromagnetic fields is performed periodically

26. A method according to claim 24,

wherein said first electromagnetic field is produced by driving a reference antenna with at least one reference antenna excitation signal, and said second and third electromagnetic fields are produced by driving at least one phase canceling antenna with at least one phase canceling antenna excitation signal;

and

wherein said reversing the phase of one of said first magnetic field and said second and third electromagnetic fields is performed by reversing the polarity of one of said reference antenna excitation signal and said phase canceling antenna excitations signal, respectively.

27. A method of spatially shifting null zones in an interrogation zone of a marker detection system, said method comprising:

producing a first reference electromagnetic field during a first time period;

producing a second electromagnetic field substantially in phase with said first reference electromagnetic field during said first time period; and

producing a third electromagnetic field substantially out of phase with said first reference electromagnetic field during said first time period.

28. The method of claim 27, said method further comprising:

producing said first reference electromagnetic field during a second time period;

producing a fourth electromagnetic field substantially out of phase with said first reference electromagnetic field during said second time period; and

producing a fifth electromagnetic field substantially in phase with said first reference electromagnetic field during said second time period.

29. The method of claim 27, said method further comprising:

producing said second electromagnetic field during a second time period;

producing said third electromagnetic field during a second time period; and

producing a second reference electromagnetic field during said second time period, said second reference electromagnetic field being substantially out of phase with said second electromagnetic field and substantially in phase with said third electromagnetic field during said second time period.