Sources of wireless power — such as wireless cellphone charging pads — require near-physical contact with the pad, limiting the usefulness of a truly wireless power source. Recent work has extended wireless power to mid-range, which can supply power at inches to feet of separation. Most of these wireless power systems have only focused on the power problem, not the data that needs to accompany smart devices.
A system was developed that can simultaneously deliver watts of power and transmit data at rates high enough to stream video over the same wireless connection. By integrating power and high-speed data, a true single wireless connection can be achieved.
Wireless power transfer technologies use magnetic fields to transmit power through the air. To minimize the power lost in generating these magnetic fields, antennas are used that operate in a narrow bandwidth — particularly if the transmitter and receiver are inches or feet apart from each other. Because using a narrow-bandwidth antenna limits data transfer, devices incorporating wireless power transfer have normally also incorporated separate radios for data transmission. And having separate systems for data and power transmission increases the cost, weight, and complexity of the relevant device.
While high-efficiency power transfer, especially at longer distances, does require very narrow-band antennas, the system bandwidth can actually be much wider. The new system configures a wide-bandwidth system with narrow-bandwidth components. With this wider bandwidth, the wireless power transfer link acts as a communication link, adapting data-rate enhancement techniques, such as channel equalization, to further improve data rate and data signal quality.
The system was tested with and without data transfer. When transferring almost 3 watts of power — more than enough to power a tablet during video playback — the system was only 2.3 percent less efficient when also transmitting 3.39 megabytes of data per second. At 2 watts of power, the difference in efficiency was only 1.3 percent. The tests were conducted with the transmitter and receiver 16 centimeters (6.3 inches) apart, demonstrating the ability of the system to operate in longer-distance wireless power links.