Communication by Means of Modulated Johnson Noise
Low-power wireless communication, such as backscatter, has played a critical role in enabling very low-power, battery-free sensing. Compared to conventional wireless communication methods, backscatter communication is orders of magnitude less power-consuming because the transmitting device (or tag) does not need to generate a carrier signal and instead reflects and absorbs an existing signal in order to modulate information bits. This existing signal can be a generated RF source (e.g., RFID) or an ambient RF source (e.g., TV or FM broadcast signal). While it has been demonstrated that these techniques can be used to enable battery-free sensing, they have been sparsely adopted. The primary constraint with existing backscatter communication solutions is their dependence on a nearby RF source.
In this work, we demonstrate that is possible to wirelessly transmit information bits without the use of a generated or ambient RF source. Instead, we use Johnson (thermal) noise to modulate information bits. By selectively connecting and disconnecting an unpowered resistor to an antenna, data can be modulated and wirelessly transmitted.