Many travelers carrying multiple portable electronic devices share the same frustration of carrying multiple chargers. It would be great if a wireless power station can simultaneously charge many portable devices and the wireless power technology can be widely available like Wi-Fi. While long distance far-field wireless power transmission has been explored for more than a century, the cost, efficiency and safety issue have limited its commercial applications.

Near-field wireless charging using magnetic coupling at low RF, on the other hand, is better suited for consumer electronics. In recent years several near-field wireless power systems have been proposed. However many of them are similar to the electric toothbrush that can only charge one device at a fixed position. We took the challenge to achieve flexible wireless charging without fixed placement and demonstrated a few prototypes. The results can be found in our publications.

We are interested in both far-field and near-field wireless power transmission. They have different applications. Far-field wireless power transmission has a long history of development originated from space/defense applications. The key issues mentioned above has limited its commercialization. However the recent development in low power wireless sensor network might be a good application for far-field wireless power transmission. It is a potential solution to charge batteries of hundreds or thousands of low power sensors in a network. Since the power is low, efficiency is not a critical issue.

In addition to the wireless charger for portable electronics, near-field wireless power transmission using magnetic coupling can be used for charging electric vehicles. As the power level increases, high efficiency of overall system is even more critical. The optimization of system performance requires trade-off of several design parameters. The task complexity increases as the number of loads increases.