Battery-free Hall rectennas harvest energy across a wide spectrum, including 5G

https://phys.org/news/2026-03-hall-rectenna-ghz-frequency-range.html

"converting RF into DC electricity relies on diodes which do not efficiently capture high-frequency signals, overcome by instead relying on Hall effect/ high-mobility semiconductor heterostructures bypassing resistor-capacitor time constant to operate into tens of GHz... generates power entirely from even very weak ambient RF without need for batteries... small sensors for smart homes, industrial monitoring, wearables, deep space/ remote sensing, self-powered IoT/ internet of everything"