Modulated backscatter wireless communication system having an extended range

An electronic shelf label system employing a first electronic shelf label (ESL) to convey item information of a first item and a second ESL to convey item information of a second item comprising:

• a central node including a transmitter for transmitting a first continuous-wave signal at frequency f1, to the first ESL, and for transmitting a second continuous-wave signal at frequency f1, to the second ESL;
• the first ESL for varying a reflection of the first continuous-wave signal to produce a first modulated reflected radio signal at frequencies f1±f2;
• the second ESL for varying a reflection of the second continuous-wave signal to produce a second modulated reflected radio signal at frequencies f1±f3;
• and
• the central node further including a receiver for receiving the first reflected radio signal and the second reflected radio signal.

An electronic shelf label system employing an electronic shelf label (ESL) to convey item information of an item:

• a central node including a transmitter for transmitting a continuous-wave signal at frequency f1 to the ESL;
• the ESL for varying a reflection of the continuous-wave signal to produce a first modulated reflected radio signal at frequencies f1±f2, said ESL further for varying a reflection of the continuous-wave signal to produce a second modulated reflected radio signal at frequencies f1±f3;
• and
• the central node further including a receiver for receiving the first reflected radio signal and the second reflected radio signal.

An electronic shelf label (ESL) communication method comprising the steps of:

• transmitting a radio signal at a frequency f1 from a central node to an ESL;
• varying a reflection of the radio signal in response to a modulated subcarrier to produce a modulated reflected radio signal at frequencies f1±f2 by the ESL;
• and
• receiving the reflected radio signal by the central node.