RFID transceiver sensitivity focusing system
Shielding of a particular material and geometry is interposed between a radio frequency identification (“RFID”) antenna transceiver and a zone to be monitored by the antenna. The shielding has an aperture therein that to some extent defines a degree of focusing of the radio frequency (“RF”) field associated with the antenna. RFID tags having appropriate RFID circuitry are only detected by the antenna when they pass within the focused RF field. The shielding is formed of a thin metalized plastic material, such as film used in forming anti-static material for storage of sensitive electronics. One particular formulation is primarily polyethylene film with an aluminum coating or layer thereon.
1. A system for focusing sensitivity of an RFID transceiver, the system comprising in combination:
an RFID transceiver antenna;
said RFID transceiver antenna adapted to be located proximate to but spaced from a monitoring zone;
said RFID transceiver antenna adapted to establish an RF field within the monitoring zone;
shielding interposed between said antenna and the monitoring zone;
an aperture formed in said shielding;
said shielding formed at least partially of thin plastic anti-static film;
wherein said antenna includes a body with a lower surface oriented in a substantially horizontal plane, both said body of said antenna and said shielding oriented to overlie said monitoring zone; and
wherein said shielding includes at least two separate sheets oriented parallel with each other and spaced from each other by a distance at least as great as a width of said aperture, said separate sheets oriented non-horizontally.
2. The system of claim 1 wherein said plastic film includes polyethylene.
3. The system of claim 2 wherein said plastic film includes a majority polyethylene.
4. The system of claim 3 wherein said plastic film includes aluminum therein.
5. The system of claim 4 wherein said plastic film includes between ten percent and thirty-five percent polyethylene terephthalate.
6. The system of claim 5 wherein said plastic film includes less than one percent aluminum.
7. The system of claim 6 wherein said plastic film is a laminate structure including a polyethylene layer and a polyethylene terephthalate layer and with an adhesive bonding said polyethylene layer to said polyethylene terephthalate layer.
8. The system of claim 1 wherein said thin plastic anti-static film is metalized plastic film.
9. The system of claim 8 wherein said metalized plastic film includes a majority polyethylene.
10. The system of claim 8 wherein said metalized plastic film includes polyethylene terephthalate.
11. The system of claim 8 wherein said metalized plastic film includes less than one percent metal.
12. The system of claim 1 wherein said shielding is located within an enclosure along with said antenna.
13. The system of claim 12 wherein said shielding is oriented substantially in a plane, with said plane substantially perpendicular to a line extending from said antenna to a center of said monitoring zone.
14. The system of claim 1 wherein said shielding is located in a substantially horizontal plane.
15. The system of claim 1 wherein said shielding includes four separate sheets with each of said sheets oriented within a separate vertical plane and with each of said four sheets surrounding a border of said aperture, and with each of said sheets located adjacent two other sheets.
16. An RFID transceiver antenna featuring a focused RF field pattern, comprising in combination:
an antenna body;
shielding proximate to but spaced from said body;
an aperture in said shielding;
said shielding formed at least partially of anti-static film;
wherein said shielding is formed of thin metalized plastic;
wherein said film includes polyethylene terephthalate;
wherein said film includes both polyethylene and polyethylene terephthalate, with more polyethylene than polyethylene terephthalate; and
wherein said film is a laminate including at least two layers with a first layer formed primarily of polyethylene and a second layer formed primarily of polyethylene terephthalate.
17. The antenna of claim 16 wherein said film is greater than fifty percent polyethylene.
18. The antenna of claim 16 wherein said film includes aluminum therein.