We're used to receiving data wirelessly, over Wi-Fi, Bluetooth or cellular networks – our smartphones simply wouldn't work without it. Wireless power is also starting to make its way into devices, but it's being held back by a short range. Now, researchers from North Carolina State University (NCSU) have developed a system that can combine the two, wirelessly transmitting both data and power simultaneously from a distance.
Wireless charging systems use coils to generate electromagnetic fields that can transfer power into another coil built into a phone or other device. Many major phones nowadays have the option for wireless charging, but it usually requires the phone to be placed on top of a pad. Systems in development at institutions like Disney Research and Duke University are working towards extending that short charging range, but the NCSU project went one step further.
"Recent work by several researchers have extended wireless power to 'mid-range' which can supply power at inches to feet of separation," says David Ricketts, senior author of the new study. "While encouraging, most of the wireless power systems have only focused on the power problem – not the data that needs to accompany any of our smart devices today. Addressing those data needs is what sets our work apart here."
The team says that combining power and data transfer into a single system can reduce the cost, weight and complexity of a device. But there's a bandwidth problem: to minimize the amount of power that's lost in transit, the antennas need to transmit in a narrow bandwidth, which isn't ideal for transmitting data.
To overcome that, the NCSU team developed a system that took advantage of both wide and narrow bandwidths. The antennas that transmit power do so at narrow bandwidths, but that doesn't stop the rest of the system making use of a wider band to beam data to a device at the same time. To bolster the data transfer rates and signal quality, the team adapted some common data-rate enhancement techniques like channel equalization.
"People thought that efficient wireless power transfer requires the use of narrow bandwidth transmitters and receivers, and that this therefore limited data transfer," says Ricketts. "We've shown that you can configure a wide-bandwidth system with narrow-bandwidth components, giving you the best of both worlds."
To test the efficiency of their system, the researchers placed the transmitter and receiver 16 cm (6.3 in) apart, then beamed either just power or both power and data together. Combining the two, the system only had minimal drops in efficiency: when simultaneously beaming 3 W of power and 3.39 MB of data per second, the system was only 2.3 percent less efficient than transmitting power alone. When transferring 2 W of power, adding data only made the system 1.3 percent less efficient.
"Our system is comparable in power transfer efficiency to similar wireless power transfer devices, and shows that you can design a wireless power link system that retains almost all of its efficiency while streaming a movie on Netflix," says Ricketts.
The research was published in the journal IEEE Antennas and Wireless Propagation Letters.
Source: North Carolina State University
