No Radio Signal Needed: Modulating Thermal Noise Sends Data 7.3 Meters
Communication by means of modulated Johnson noise
Researchers have demonstrated a passive wireless communication method that modulates Johnson noise from a resistor, eliminating the need for any ambient or generated RF signal. The transmitter switches a matched resistor in and out of an antenna, achieving data rates up to 26 bps over 7.3 meters. The system operates at ultra-low power, similar to an RFID tag, and can be battery-free via solar energy harvesting. This approach enables stealthy, low-interference communication in environments without RF signals.
An interesting feature of the system is that all components of the system are at the same physical temperature, but it functions because they have different noise temperatures.
- chicken-stew
I’m away from computer so only skimmed the article until I noticed they use the ADG90x RF switch family.
IIRC that family has a single positive supply rail, and they make a nagative rail internally. The advantage is easy of implementation but you also inject some noise depending on switch position. Is this dealt with in the pub?
- mitxela
This is extremely strange. Shouldn't this be impossible by the second law of thermodynamics?
Receiving more energy when a resistor in thermal equilibrium is connected to an antenna seemingly implies that energy gets transferred from an antenna with a resistor to a an antenna without a resistor, even at thermal equilibrium.
Maybe we'll later find it's an experimental subtlety, like the faster than light neutrinos.
- pockybum522
Magic, got it.
(I am floored that this works. This is amazing.)
- analog8374
A cacophony of meaty slaps in morse-code.
- frumiousirc
> the maximum achievable throughput is 26 bps at 1.5 m and goes down to 22 bps at 4.5 m.
And when there are more than one transmitters in real world conditions instead of anechoic chamber?
It's cool and all and if this work is for it's own sake, for the sake of research, no issues. But otherwise, I struggle to think of practical use cases. I grant that my imagination may be deficient.