Teeny-Tiny Bluetooth Transmitter Runs on Less Than 1 Milliwatt

These battery-powered and energy-harvesting millimeter-scale sensors are meant to last for years without needing replacement, but their radios can’t muster the energy needed to communicate using even the lowest energy version of Bluetooth, called Bluetooth Low Energy (BLE). An ordinary transmitter circuit requires a tunable RF oscillator to generate the frequency, a power amplifier to boost its amplitude, and an antenna to radiate the signal. As a 14-mm long loop of conductor, the antenna was considerably larger than an on-chip inductor for a millimeter-scale radio could be.

Source: spectrum.ieee.org