It is possible to power a device with radio waves - the most basic crystal radio just drives a speaker using the acquired radio signal. In 1945 the USSR “gifted” a concealed listening device (The Thing) to the US ambassador which worked this way - it was only “on” when an external radio was transmitting the correct frequency, making it very hard to detect. RFID tags also work the same - they don’t require batteries because the chip is activated when the tag’s antenna gets hit by the radio from the scanner.
This is only practical for very low-power devices, because transmitting high-power radio waves is dangerous.
Maybe, but then you run into difficulty with antenna size. An RFID chip uses a tiny antenna but it’s only expected to work within a range of about 1cm. To make the listening device I linked above work with a radio source in another room required an antenna 23cm long.
I doubt you could ever transmit enough power to drive a display this way, at least not safely because the output from the transmitter would have to be orders of magnitude higher, and the circuitry on the receiving end would have to be bulkier as a consequence or risk overheating.
Ah, no. Electromagnetic induction and electromagnetic radiation are related but different - induction doesn’t produce radiation (radio) waves that would travel longer distances.
It is possible to power a device with radio waves - the most basic crystal radio just drives a speaker using the acquired radio signal. In 1945 the USSR “gifted” a concealed listening device (The Thing) to the US ambassador which worked this way - it was only “on” when an external radio was transmitting the correct frequency, making it very hard to detect. RFID tags also work the same - they don’t require batteries because the chip is activated when the tag’s antenna gets hit by the radio from the scanner.
This is only practical for very low-power devices, because transmitting high-power radio waves is dangerous.
It would likely be sufficient for things like smart wearables, though. Maybe even smart watches
Maybe, but then you run into difficulty with antenna size. An RFID chip uses a tiny antenna but it’s only expected to work within a range of about 1cm. To make the listening device I linked above work with a radio source in another room required an antenna 23cm long.
I doubt you could ever transmit enough power to drive a display this way, at least not safely because the output from the transmitter would have to be orders of magnitude higher, and the circuitry on the receiving end would have to be bulkier as a consequence or risk overheating.