Ant-sized radios for the IoT

US-based engineers have developed an ant-sized radio that gathers all the power it needs from the same electromagnetic waves that carry signals to its receiving antenna.

This tiny wireless chip, designed to compute, execute and relay commands, is developed by engineers at Stanford University in collaboration with researchers at the University of California. “The next exponential growth in connectivity will be connecting objects together and giving us remote control through the web,” said Amin Arbabian, an assistant professor of electrical engineering.

Much of the infrastructure required to control sensors and devices remotely already exists - we have the internet to carry commands around the globe, and computers and smartphones to issue the commands. What is missing is a wireless controller cheap enough to be installed on any gadget, anywhere.

“In the past, when people thought about miniaturising radios, they thought about it in terms of shrinking the size of the components,” said Arbabian. But Arbabian’s approach to dramatically reducing size and cost was different. Everything hinged on squeezing all the electronics found in, say, the typical Bluetooth device down into a single, ant-sized silicon chip.

This approach to miniaturisation would have another benefit - dramatically reducing power consumption, because a single chip draws so much less power than conventional radios. In fact, if Arbabian’s radio chip needed a battery - which it does not - a single AAA contains enough power to run it for more than a century. But to build this tiny device, every function in the radio had to be re-engineered.

The antenna

The antenna had to be small - one tenth the size of a Wi-Fi antenna - and operate at the incredibly fast rate of 24 billion cycles per second. Standard transistors could not easily process signals that oscillate that fast. So Arbabian’s team had to improve basic circuit and electronic design. Many other such tweaks were needed but in the end Arbabian managed to put all the necessary components into one chip: a receiving antenna that also scavenges energy from incoming electromagnetic waves; a transmitting antenna to broadcast replies and relay signals over short distances; and a central processor to interpret and execute instructions. No external components are needed.

Based on his designs, the French semiconductor manufacturer STMicroelectronics fabricated 100 of these radios on a chip. Arbabian has used these prototypes to prove that the devices work; they can receive signals, harvest energy from incoming radio signals and carry out commands and relay instructions. Now Arbabian envisions networks of these radio chips deployed every metre or so throughout a house (they would have to be set close to one another because high-frequency signals do not travel far).

He thinks this technology can provide the web of connectivity and control between the global internet and smart household devices. “Cheap, tiny, self-powered radio controllers are an essential requirement for the Internet of Things,” said Arbabian, who has created a webpage to share some ideas on what he calls battery-less radios.