Your phone can become a RFID reader, scientists promise

New technology developed by engineers at the University of California San Diego allows users to know which items in their fridge are expiring by using a chip integrated into product packaging and a software update on their phone. The phone identifies objects based on signals the chip emits from specific frequencies, such as Bluetooth or WiFi. In an industrial setting, a smartphone equipped with the software update could be used as an RFID reader. This technology harnesses breakthroughs in backscatter communication, which uses signals already generated by a smartphone and redirects them back in a format the phone can understand. The technique uses 1000 less power than state-of-the-art to generate WiFi signals, allowing for very low-power communication between components of the Internet of Things and hardware, such as WiFi or Bluetooth transceivers, for applications such as on-body sensors or asset trackers.

The custom chip is the size of a grain of sand and costs only a few pennies to manufacture, and it needs so little power that it can be entirely powered by LTE signals, a technique called RF energy harvesting. The chip turns Bluetooth transmissions into WiFi signals, which can then be detected by a smartphone with that specific software update. The team presented their work at the IEEE International Solid-State Circuits Conference in San Francisco on Feb. 20, 2023.

The technology enables wireless communication and battery-less operation coming from a single mobile device, which has never been achieved before. The broader promise of the technology is the development of devices that do not need batteries because they can harvest power from LTE signals instead. This would lead to devices that are significantly less expensive and can last up to several decades. “E-waste, especially batteries, is one of the biggest problems the planet is facing, after climate change,” said Dinesh Bharadia, a professor in the UC San Diego Department of Electrical and Computer Engineering and one of the paper’s senior authors.

The researchers achieved this breakthrough by harvesting power from LTE smartphone signals and buffering this power onto an energy storage capacitor. This activates a receiver that detects Bluetooth signals, which are then modified into reflected WiFi signals. The software update is a bit sequence that turns the Bluetooth signal into something that can be more easily turned into a WiFi signal. Most lower power wireless communications require custom protocols, but the device developed by the researchers relies on common communication protocols, such as Bluetooth, WiFi and LTE.

The device has a range of one meter, but adding a battery would boost the tag’s range to tens of meters, at the cost of increasing the price. The device, which is half a square inch in size, costs just a few cents to manufacture. The team hopes to integrate the technology in other research projects to demonstrate its capabilities and commercialize the device, either through a startup or an industry partner.