Modulated backscatter wireless communication system having an extended range
First Claim
1. An electronic shelf label system employing an electronic shelf label (ESL) tag to convey item information of an item comprising:
- a central node including means for transmitting a continuous-wave signal at frequency f1 to the ESL tag;
the electronic shelf label tag for conveying product information of items including means for modulating a subcarrier signal f2 with an information signal to produce a modulated subcarrier signal and means for varying a reflection of the continuous-wave signal in response to the modulated subcarrier to produce a modulated reflected radio signal at frequency f1 ±
f2 ;
the central node further including means for receiving the modulated reflected radio signal and obtaining the information signal.
2 Assignments
0 Petitions
Accused Products
Abstract
A modulated backscatter communication system (e.g., an Electronic Shelf Label (ESL) system) includes a central node (e.g., a ceiling node) and one or more remote nodes (e.g., ESL tags). The central node transmits a downlink radio signal which is reflectively modulated at a remote node to produce a modulated reflected radio signal. At the remote node, a precise-frequency subcarrier signal is modulated with an uplink information signal to produce a modulated signal which is used to produce the modulated reflected radio signal. At the central node, the modulated reflected radio signal is received, detected and narrowband filtered to obtain the modulated subcarrier signal which is then demodulated to obtain the uplink information signal, with great immunity to close to carrier downlink radio noise and fluorescent light backscatter interference.
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Citations
33 Claims
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1. An electronic shelf label system employing an electronic shelf label (ESL) tag to convey item information of an item comprising:
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a central node including means for transmitting a continuous-wave signal at frequency f1 to the ESL tag; the electronic shelf label tag for conveying product information of items including means for modulating a subcarrier signal f2 with an information signal to produce a modulated subcarrier signal and means for varying a reflection of the continuous-wave signal in response to the modulated subcarrier to produce a modulated reflected radio signal at frequency f1 ±
f2 ;the central node further including means for receiving the modulated reflected radio signal and obtaining the information signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An electronic shelf label system employing an electronic shelf label (ESL) tag to convey item information of an item comprising:
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a central node including a transmitter for transmitting a continuous-wave signal at frequency to the ESL tag; the electronic shelf label tag for conveying product information of items including a generator for generating; a first reflected radio signal at frequency f1 ±
f2 which has been modulated using a frequency subcarrier signal f2 which has been modulated with a first information signal, wherein the first reflected radio signal is generated by varying a reflection of the continuous-wave signal at frequency f1 ;a second reflected radio signal at frequency f1 ±
f3 which has been modulated using a frequency subcarrier signal f3 which has been modulated with a second information signal, wherein the second reflected radio signal is generated by varying a reflection of the continuous-wave signal at frequency f1 ;the central node further including a receiver for receiving the first reflected radio signal and the second reflected radio signal and obtaining the first information signal and the second information signal.
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12. A modulated backscatter electronic shelf label communication system employing an electronic shelf label (ESL) tag to convey item information of an item:
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a central node including a transmitter for transmitting a radio signal; an electronic shelf label located on a shelf including; a generator for generating a subcarrier signal; a modulator for modulating said subcarrier signal with an information signal to produce a modulated subcarrier signal; a reflector for varying a reflection of said radio signal in response to said modulated subcarrier signal to produce a modulated radio signal; a display which displays the item information of the item; the central node further including; a receiver for receiving and detecting said reflected radio signal to obtain said modulated subcarrier signal; a narrowband filter, including a digital signal, for filtering said modulated subcarrier signal; a demodulator for demodulating the modulated subcarrier signal to obtain said information signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method of communicating to an electronic shelf label (ESL) tag comprising the steps of:
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transmitting a radio signal at a frequency f1 from a central node to the ESL tag; modulating a subcarrier signal f2 with an information signal by the ESL tag; varying a reflection of the radio signal in response to the modulated subcarrier to produce a modulated reflected radio signal at frequency f1 ±
f2 by the ESL tag; andreceiving the modulated reflected radio signal by the central node and obtaining the information signal.
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Specification