Modulated Noise Communication: Reading UHF RFID tags without a carrier.

This paper demonstrates that UHF RFID tags can be read without a carrier. More specifically, using an alternative reader design that does not emit a carrier, we show that it is possible to read an RFID tag that was designed to be read by a conventional RFID reader that does emit a carrier. Typical RFID tags are designed to modulate a carrier; it turns out that, in addition to modulating a carrier, a backscatter modulator circuit also modulates tag circuit noise, including Johnson noise; Johnson and other noise is present in a tag even if a carrier is not. Modulated Noise Communication (MNC) can be read by an alternative reader design. The reader for modulated noise communication is simpler than a conventional backscatter reader because it does not have to contend with the problem of self-jamming. The absence of a carrier means that the tag needs an alternative power source; this could be an energy harvester such as a photovoltaic cell, or could be a time-multiplexed continuous wave signal from the reader. The use of time multiplexing means that the reader would still inherit the benefits of not needing to counteract self jamming.