Omnidirectional RFID antenna

• US 20020109636A1
• Filed: 01/15/2002
• Published: 08/15/2002
• Est. Priority Date: 01/16/2001
• Status: Active Grant

• Current Assignee: Destron Fearing Corporation (Merck & Co., Inc.)
• Original Assignee: Digital Angel Corporation
• Inventors: Johnson, Daniel L., Smirnov, Yuri
• Granted Patent: US 6,720,930 B2
• Time in Patent Office: Days
• US Class Current: 343/742
• CPC Class Codes: A01K 11/006 Automatic identification systems for animals, e.g. electronic devices, transponders for animals identification systems for access to feeding pens A01K1/0209; ear tags with electronic identification means A01K11/004
• 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 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes 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

Abstract

An omni-directional RFID antenna is provided for use with a remote interrogator/reader system used for identifying tagged animals. A pair of antenna coils are arranged in a crossing pattern that results in the creation of an omni or multi-directional electromagnetic field. Additionally, the crossing pattern creates out of phase null zones at quadrants within the crossing pattern of the antennae that reduces interference caused by RF noise generated from the environment. The omni-directional electromagnetic field effectively surrounds each of the null zones thereby allowing an RFID transponder to be successfully interrogated despite the orientation of the transponder as it passes through the electromagnetic field.

Claims

1. An antenna for use with a remote interrogator/reader unit used to detect information specific to each of a plurality of radio frequency transponders used for tagging animals such as livestock, said antenna comprising:

a first antenna coil arranged in a closed loop configuration and extending along a first axis;

a second antenna coil arranged in a closed loop configuration and extending along a second axis, said first coil positioned in close proximity to said second coil and oriented so that said first axis extends substantially perpendicular to said second axis forming a crossing pattern;

a housing containing said first and second coils, said housing capable of being positioned in the proximity of said transponders; and

wherein said antenna generates multi-directional electromagnetic fields when powered by said remote interrogator/reader unit, and said antenna further generates null zones within close proximity of said crossing pattern of said first and second coils, said null zones thereby reducing RF noise from the environment.

2. An antenna, as claimed in claim 1, wherein:

said generated electromagnetic fields have a total inductance of less than 400 μ

H.

3. An antenna, as claimed in claim 1, wherein:

said coils are made of approximately 22-gauge wire.

4. An antenna, as claimed in claim 1, wherein:

each coil contains about 25 windings.

5. An antenna for use with a remote interrogator/reader unit used to detect information specific to each of a plurality of radio frequency transponders attached to animals such as livestock, said antenna comprising:

a pair of cross oriented antenna coils creating out of phase areas in close proximity to the antenna coils to cancel external RF noise, said out of phase areas being further defined within four quadrants of the antenna coils, said pair of cross oriented antenna coils further creating multi-directional electromagnetic fields extending away from said coils and effective to interrogate said transponders.

6. An antenna, as claimed in claim 5, wherein:

said electromagnetic fields have a total inductance of less than 400 μ

H.

7. An antenna, as claimed in claim 5, wherein:

said coils are made of approximately 22-gauge wire.

8. An antenna, as claimed in claim 5, wherein:

each coil contains about 25 windings.

9. An antenna for use with a remote interrogator/reader unit used to detect information specific to each of a plurality of radio frequency transponders attached to animals such as livestock, said antenna comprising:

means for creating an omni-directional field of electromagnetic energy effective to interrogate said transponders;

means for creating out of phase null zones to reduce RF noise generated from the surrounding environment; and

wherein said antenna is arranged in a crossing pattern of antenna coil members.

10. An antenna, as claimed in claim 9, wherein:

said omni-directional field of electromagnetic energy has a total inductance of less than about 400 μ

H.

11. An antenna, as claimed in claim 9, wherein:

said coil members are made of approximately 22 gauge wire.

12. An antenna, as claimed in claim 9, wherein:

said coil members contain approximately 25 windings each.

13. A method of interrogating a radio frequency transponder by an antenna used within a remote interrogator/reader system, the radio frequency transponder being adapted especially for use in tagging animals such as livestock, said method comprising the steps of:

providing a first antenna coil having a closed loop configuration;

positioning a second antenna coil having a closed loop configuration such that said second coil extends substantially perpendicular to said first coil thus creating a crossing pattern between the first and second antenna coils;

exciting the antenna to create an omni-directional field of electromagnetic energy, and to create out of phase null zones at four quadrants within the crossing pattern, the null zones being effective to cancel RF noise generated from the environment; and

passing the transponder through the electromagnetic field resulting in the transponder being activated to transmit a radio frequency signal unique to the transponder.