Modulated backscatter wireless communication system having an extended range
First Claim
1. A radio communication system comprisinga transceiver node includingmeans for transmitting a radio signal, anda subsystem circuit includingmeans for generating a precise-frequency subcarrier signal, having a frequency which lies between two integer multiples of an AC power-supply-line frequency,means for modulating said subcarrier signal with an information signal to produce a modulated subcarrier signal,means for varying a reflection of said radio signal in response to said modulated subcarrier signal to produce a modulated reflected radio signal,the transceiver node further includingmeans for receiving and detecting said reflected radio signal to obtain said modulated subcarrier signal,narrowband filter means, including a digital signal and having a bandwidth this is less than the AC line frequency, for filtering said modulated subcarrier signal, andmeans for demodulating the modulated subcarrier signal to obtain said information signal.
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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.
68 Citations
20 Claims
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1. A radio communication system comprising
a transceiver node including means for transmitting a radio signal, and a subsystem circuit including means for generating a precise-frequency subcarrier signal, having a frequency which lies between two integer multiples of an AC power-supply-line frequency, means for modulating said subcarrier signal with an information signal to produce a modulated subcarrier signal, means for varying a reflection of said radio signal in response to said modulated subcarrier signal to produce a modulated reflected radio signal, the transceiver node further including means for receiving and detecting said reflected radio signal to obtain said modulated subcarrier signal, narrowband filter means, including a digital signal and having a bandwidth this is less than the AC line frequency, for filtering said modulated subcarrier signal, and means for demodulating the modulated subcarrier signal to obtain said information signal.
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16. A radio communication apparatus comprising
means for transmitting a radio signal, means for receiving a reflected modulated version of said radio signal, said modulated radio signal modulated with an information-modulated subcarrier signal having a frequency which lies between two integer multiples of an AC power-supply-line frequency, narrowband filter means, including a digital signal processor and having a receive bandwidth which is less than the AC line frequency, for filtering said received modulated radio signal to obtain said information-modulated subcarrier signal, and means for demodulating said information-modulated subcarrier signal to obtain an information signal therefrom.
Specification