System for powering and reading RFID tags
View Patent ↗A system for tracking items using passive RFID tags utilizes separate data and power frequencies. Within an area in which the items are located, one or more data readers are provided but many more separate power modules are distributed through the space, for powering up the tags. With the power nodes distributed, the tags are powered from a relatively short distance, enabling the tags to transmit through a greater distance. One or more of the readers can include a power-node control which sends an RF signal to control on/off status of specific power nodes within the area, so that power nodes can be activated zone by zone, to thereby permit the reader to determine location by zone of products as their RFID tags are read.
1. A system for identifying and tracking movable products bearing RFID tags using a reader receiving data signals transmitted on a data frequency by tags on a multiplicity of such products, the tags being powered by received RF energy on a power frequency, comprising:
a product-containing area within which the multiplicity of products are located, the products each having an RFID tag,
one or more readers within the product-containing area to receive transmitted data from the RFID tags on the data frequency, and
a plurality of power nodes within the area, the power nodes being independently powered, separate from and spaced from the readers and the tags and spaced apart within the area, each power node when activated sending an RF signal on the power frequency powering up RFID tags within a transmit distance of the power node,
whereby tags are powered up to be read from positions generally more distant from a particular reader than possible if a powering signal were sent by the particular reader itself.
2. The system of claim 1 , wherein said transmit distance of the power nodes is less than the reading distance of the one or more readers.
3. The system of claim 2 , wherein a coding gain scheme is used within the RFID tag data transmission so that the distance read by the reader can be increased without increasing the RFID tag's transmitted power.
4. The system of claim 1 , wherein the number of power nodes in the area is greater than the number of readers.
5. The system of claim 4 , wherein the number of power nodes in the area is more than twice the number of readers in the area.
6. The system of claim 1 , wherein at least one reader within the area includes a power-node control which sends an RF signal to control on/off status of specific power nodes within the area, and the area being divided into zones, with power nodes activated by zones selectively, permitting the reader to determine location by zone of products as their RFID tags are read.
7. The system of claim 1 , wherein the RFID tags transmit using UWB.
8. The system of claim 7 , the reader having means for receiving strength indication to determine the distance of a read RFID tag from the reader.
9. The system of claim 7 , wherein some of the RFID tags transmit on a different transmission frequency from other ones of the RFID tags, the frequencies being set at the time of manufacturing.
10. The system of claim 7 , wherein the transmitted signal from the tags is Pulse Position Modulated (PPM).
11. The system of claim 7 , wherein the transmitted data contains a pre-amble and a post-amble to determine where the transmitted data starts and stops.
12. The system of claim 1 , the reader having means for receive strength indication to determine the distance of a read RFID tag from the reader.
13. The system of claim 12 , wherein at least two readers are in or adjacent to the product-containing area, enabling triangulation to locate a tag's position.
14. The system of claim 1 , including three readers in or adjacent to the product-containing area, the three readers being in communication and noting the time of arrival of a transmitted signal from a particular tag, so that differences in arrival time among the three readers can be used to determine a unique position for the tag.
15. The system of claim 1 , wherein the data frequency is different from the power frequency.