EP0670558A2
Expired / Lapsed
EP
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Modulated backscatter wireless communication system having an extended range
Assignee: NCR International Inc
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Filing: 1995-02-22
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Granted: —
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Expires: 2015-02-22
Abstract
Abstract A modulated backscatter communication system (e.g., an Electronic Shelf Label (ESL) system) includes a central node (10) (e.g., a ceiling node) and one or more remote nodes (20-40) (e.g., ESL tags). The central node (10) transmits a downlink radio signal (16) which is reflectively modulated at a remote node (20) to produce a modulated reflected radio signal (17). At the remote node (20), a precise-frequency subcarrier signal (26,27) is modulated (24) with an uplink information signal (25) to produce a modulated signal which is used to produce (22) the modulated reflected radio signal (17). At the central node, the modulated reflected radio signal is received (12), detected and narrowband filtered (13,19) to obtain the modulated subcarrier signal which is then demodulated to obtain the uplink information signal (25), with great immunity to close to carrier downlink radio noise and fluorescent light backscatter interference.
Inventors
- 👤 James Gifford Evans
- 👤 Giovanni Vannucci
- 👤 Anthony R. Shober
- 👤 Stephen A. Wilkus
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 19:48
CPC Classifications
G; G06; G06K; G06K7/00; G06K7/10; G06K7/10009; G06K7/10019; G06K7/10069; G01; G01S; G01S13/00; G01S13/74; G01S13/82; G01S13/825; G06K7/0008; G01S13/88
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
133 words
A radio communication system CHARACTERIZED BY a transceiver node including means for transmitting a radio signal, and means for generating a precise-frequency sub-carrier signal, having a frequency which lies between two 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, means for receiving and detecting said reflected radio signal to obtain said modulated subcarrier signal, narrowband filter means including a digital signal processor for filtering said modulated subcarrier signal, and means for demodulating the modulated subcarrier signal, said demodulating means having a receive bandwidth which is less than the AC line frequency to obtain said information signal.
Claim 2
Dependent Claim
25 words
The system of claim 1 wherein said receiving means includes a homodyne receiver for detecting said reflected radio signal to obtain said modulated subcarrier signal.
Claim 3
Dependent Claim
21 words
The system of claim 1 wherein said modulating means modulates one of a plurality of subcarrier frequencies which are inputted thereto.
Claim 4
Dependent Claim
19 words
The system of claim 1 wherein said demodulating means includes a comb filter for filtering said modulated subcarrier signal.
Claim 5
Dependent Claim
21 words
The system of claim 1 wherein said demodulating means includes a digital signal processing means for filtering said modulated subcarrier signal.
Claim 6
Dependent Claim
21 words
The system of claim 1 wherein the receiving means detects the signal strength at a frequency where no subcarrier is present.
Claim 7
Dependent Claim
96 words
A radio communication apparatus CHARACTERIZED BY 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 multiples of an AC power-supply-line frequency, narrowband filter means including a digital signal processor 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, said demodulating means having a receive bandwidth which is less than the AC line frequency.
Claim 8
Dependent Claim
13 words
The apparatus of claim 7 wherein said receiving means includes a homodyne receiver.
Claim 9
Dependent Claim
20 words
The apparatus of claim 7 wherein said demodulating means includes a comb filter for filtering said received reflected radio signal.
Claim 10
Dependent Claim
26 words
The system of claim 4 or the apparatus of claim 9 wherein said comb filter is adapted to demodulate and detect more than one sideband frequency.
Claim 11
Dependent Claim
28 words
The system of claim 5 or the apparatus of claim 7 wherein said digital signal processing means is adapted to demodulate and detect more than one sideband frequency.
Claim 12
Dependent Claim
66 words
A radio communication apparatus CHARACTERIZED BY means for generating a precise-frequency subcarrier signal having a frequency which lies between two multiples of an AC power-supply-line frequency, means for modulating said subcarrier signal with an information signal to produce a modulated signal, and means for varying a reflection of a received single-frequency radio signal in response to said modulated signal to produce a modulated reflected radio signal.
Claim 13
Dependent Claim
20 words
The system of claim 1 or the apparatus of claim 12 wherein said generating means includes a crystal oscillator .
Claim 14
Dependent Claim
24 words
The system of claim 1 or the apparatus of claim 12 wherein said modulating means generates a modulated signal having one or more sidebands.
Claim 15
Dependent Claim
26 words
The system or the apparatus of claim 13 further including a counter means for counting down a crystal oscillator frequency to generate the precise-frequency subcarrier signal.
Claim 16
Dependent Claim
25 words
The system or the apparatus of claim 13 further including a multiplier means for multiplying a crystal oscillator frequency to generate the precise-frequency subcarrier signal.
Claim 17
Dependent Claim
24 words
The system or the apparatus of claim 13 further including a frequency synthesizer to generate the precise-frequency subcarrier signal from a crystal oscillator frequency.
Claim 18
Dependent Claim
26 words
The system or the apparatus of claim 13 further including both multiplier and counter means to generate the precise-frequency subcarrier signal from a crystal oscillator frequency.
Claim 19
Dependent Claim
22 words
The system of claim 1 or the apparatus of claim 12 wherein said generating means generates more than one such subcarrier signal.
References Cited (Backward Citations)
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