Battery-Free Cellphone Harvests Power from Ambient Radio Signals, Light

A team of computer scientists and electrical engineers at the University of Washington has invented a cellphone that requires no batteries and harvests power from either ambient radio signals or light.

“We’ve built what we believe is the first functioning cellphone that consumes almost zero power,” said co-author Dr. Shyam Gollakota, from the Paul G. Allen School of Computer Science & Engineering at the University of Washington.

“To achieve the really, really low power consumption that you need to run a phone by harvesting energy from the environment, we had to fundamentally rethink how these devices are designed.”

Dr. Gollakota and co-authors eliminated a power-hungry step in most modern cellular transmissions — converting analog signals that convey sound into digital data that a phone can understand.

This process consumes so much energy that it’s been impossible to design a phone that can rely on ambient power sources.

Instead, the battery-free cellphone takes advantage of tiny vibrations in a phone’s microphone or speaker that occur when a person is talking into a phone or listening to a call.

An antenna connected to those components converts that motion into changes in standard analog radio signal emitted by a cellular base station.

This process essentially encodes speech patterns in reflected radio signals in a way that uses almost no power.

To transmit speech, the phone uses vibrations from the device’s microphone to encode speech patterns in the reflected signals.

To receive speech, it converts encoded radio signals into sound vibrations that that are picked up by the phone’s speaker.

In the prototype device, the user presses a button to switch between these two ‘transmitting’ and ‘listening’ modes.

“The cellphone is the device we depend on most today. So if there were one device you’d want to be able to use without batteries, it is the cellphone,” said senior author Professor Joshua Smith, from the Allen School and the Department of Electrical Engineering at the University of Washington.

“The proof of concept we’ve developed is exciting today, and we think it could impact everyday devices in the future.”

Credit: https://www.reddit.com/r/Futurology/comments/6oucme/batteryfree_cellphone_harvests_power_from_ambient/?st=J5FI85SF&sh=a3d6d295