Distributed Antenna Array With Centralized Data Hub For Determining Presence And Location Of RF Tags

• US 20080258876A1
• Filed: 05/06/2008
• Published: 10/23/2008
• Est. Priority Date: 11/05/2004
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: GOLIATH Solutions LLC (Osa Acquisition, LLC)
• Inventors: Overhultz, Gary L., Mead, Robert W., Harman, Gordon E.
• Granted Patent: US 8,070,065 B2
• Time in Patent Office: Days
• US Class Current: 340/10.2
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil

Abstract

A distributed antenna array with a centralized data hub for determining the presence and location of RF tags has been disclosed. This antenna array centralizes electronics and distributes the RF to zones in a facility to greatly reduce the expense of recurring components for monitoring RF tags. A single BRT/hub with multiple antennas attached to transmit and receive ports is used to cover an entire facility. Large facilities are covered by a small number of the BRT/hub combinations. The BRT/hub has transmit antennas coupled thereto, preferably by co-axial cable, that transmit signals to a portion or all of the RF tags and all or a portion of them modulate and reflect the RF signal to a particular receiving antenna. The receiving antenna then returns the RF signal with tag data to the BRT/hub, preferably by co-axial cable. Also disclosed is an RF backscatter tag that cleanly switches a resonant aperture antenna on and off, thereby greatly increasing the mark-to-space ratio of the backscatter data. This enables tags to be detected by the BRT at much greater distances.

Claims

1. A distributed antenna array system with a centralized data reader/transmitter for determining presence and location of RF tags comprising:

at least one designated area in a facility;

a plurality of sub-areas in each of the designated areas;

a plurality of RF tags to be dispersed in each sub-area, each of the tags being associated with a particular object in the sub-area;

a single backscatter reader/transmitter (BRT) in each designated area; and

a distributed antenna array in the facility comprising;

at least one transmitting antenna electronically coupled to the single BRT and positioned to illuminate at least a portion of the plurality of the RF tags in each designated sub-area with a carrier signal containing;

a single RF signal receiving antenna in each sub-area; and

each of the single RF signal antenna in each sub-area receiving data from each of the RF tags in the sub-area that have been illuminated by the at least one BRT transmitting antenna and transferring the received tag data to the single hub.

2. The system of claim 1 wherein:

the selected facility is a product sale facility; and

the particular object associated with a tag is a product display, sign, merchandising or advertising material (“

Display”

).

3. The system of claim 1 wherein the system determines that the Display is present in a sub-area in the facility where a person may see or interact with the Display.

4. The system of claim 1 wherein the system determines that the Display is properly installed in a particular location in the sub-area.

5. The system of claim 4 wherein the system determines that the Display is present in the particular location for an appropriate period of time.

6. The system of claim 1 wherein the RF tag is carried by a person in the facility to enable market testing through the use of data collected concerning the Displays in the particular locations visited by the person and the time spent in each particular location.

7. The system of claim 1 wherein the at least one transmitting antenna is a quadrafiler helix antenna having a shaped beam with low gain on axis and high gain to the sides.

8. The system of claim 1 wherein:

each transmitting antenna is connected to the single backscatter reader/transmitter by a coaxial cable; and

each transmitter antenna contains a high power amplifier to recover coaxial cable signal attenuation and a band-pass filter at the proper frequency to reduce noise and/or harmonics.

9. The system of claim 1 wherein the distributed antenna array comprises:

a plurality of transmitting antennae, each of the transmitting antennae being located in or near the designated area to transmit communication signals to at least a portion of the RF tags located in at least some of the sub-areas.

10. The system of claim 1 further comprising:

a plurality of designated areas in the facility;

a single BRT/hub (“

Spider”

) for illuminating at least a portion of the RF tags in each designated area; and

a plurality of Spiders for receiving response signals from at least a portion of the illuminated RF tags and coupling the response signals to the single master BRT/hub that transmits the data to a server that processes data.

11. The system of claim 1 wherein each RF tag comprises:

an antenna system with a resonant aperture; and

a switch coupled to one or more elements of the antenna system to cleanly connect and disconnect selected portions of one or more elements of the antenna system to greatly increase the mark-to-space ratio of the backscatter data.

12. The system of claim 1 wherein each RF tag comprises:

an antenna with two ¼

λ

antenna elements;

a switch coupled to one of the ¼

λ

antenna element for selectively closing and connecting both antenna elements together to form a ½

λ

antenna that reflects the BRT carrier signal and for opening to create two ¼

λ

antenna elements that absorb at least some of the BRT carrier signal; and

a backscatter frequency generator coupled to the switch for selectively opening and closing the switch.

13. A method of determining presence and location of RF tags using a distributed antenna array with a centralized data hub comprising the steps of:

selecting at least one designated area in a particular facility;

selecting a plurality of sub-areas in each of the designated areas;

placing a plurality of RF tags in each sub-area, each of the tags being associated with a particular object in the sub-area;

placing a reader/transmitter in each designated area; and

forming a distributed antenna array comprising the steps of;

positioning at least one transmitting antenna in or near the designated area to illuminate at least a portion of the plurality of the RF tags in the sub-areas with communication data;

the transmitting antenna being electronically coupled to the single reader/transmitter; and

placing a single RF signal receiving antenna in each sub-area; and

receiving data from each of the RF tags in each sub-area that has been illuminated by at least one transmitting antenna with the single RF signal receiving antenna and transferring the received data to the single hub for data transmission to a server for processing.