Cellphone addicts rejoice; new technology developed by engineers could make phone batteries last approximately 30 percent longer on a single charge. The circuitry, which the team has patented, converts some of a phone’s radio signals into direct current (DC) power that is then used to charge its battery.
The technology weighs very little and can be integrated into a cellphone case. “When we communicate with a cell tower or Wi-Fi router, so much energy goes to waste,” said Chi-Chih Chen, a research associate professor of electrical and computer engineering. “We recycle some of that wasted energy back into the battery.”
Why the device is different
Ray Floyd, an electrical engineer and ENGINEERING.com contributor who was not involved with the research, says similar devices already exist. “The use of RF energy to power units is not new, as it has been used in the RFID industry for many years, as tags capture the RF energy and use it to transmit back to the origin as a data string of information,” he explained. “[This new technology uses] a similar operation, and should prove to be a boon for cell phone users, once the application is developed and installed into the cell phones.”
According to Robert Lee, an Ohio State professor of electrical and computer engineering who worked on the project, his technology differs from other devices. “These other devices are trying to harvest little bits of energy from the air,” he said. “Our technology is based on harvesting energy directly from the source. They can capture microwatts or even nanowatts (millionths or billionths of a watt), but cellphones need milliwatts (thousandths of a watt) or higher.”
Recapturing cellphone signals
Lee adds that an overwhelming majority of cellphone signals don’t end up reaching a destination, becoming lost. He says some of those signals can be recaptured. “No one can charge a cellphone from the air, but we can reduce power consumption by retrieving some of those lost milliwatts,” he explained. “Think of it as a battery extender rather than a charger.”
Lee has been researching small antennas for many years. He says it’s crucial to design a circuit that quickly identifies useful signals – including when the antenna is in motion.
Removing the information from the RF carrier
The key to the system is the ability to remove the information (audio signal) from the RF carrier, then use the RF carrier as a feed for the battery booster’s rectifier. The researchers say this process has no impact on voice quality or data transmission.
Their device identifies which radio signals are being wasted and how much it can consume without impacting phone function. It can only work when a phone is transmitting (i.e. when a user is texting, chatting on the phone or consuming data).
“If you’re just playing a game offline, it won’t help you,” Chen said.
Chen and his team have formed a company to further develop the technology. The device is expected to cost about $100.