Recently, wireless charging via magnetic resonance coupling has gained attention because it has the potential of efficient midrange wireless charging. Here, functions such as sensing at the transmitter and wireless communication from the target are the essential elements to realize a standard wireless charging system. Currently, the sensing and communication protocol of the hardware (i.e., the high-frequency power source and antenna configuration) compatible with wireless charging is gaining attention in terms of its cost and space reduction due to the use of common components for multiple functions. However, this protocol has the problem of narrow effective areas due to the fact that the sensing range depends on the fixed Q factor of the antenna. To overcome this problem, the concept of wide-area sensing based on a Q controllable antenna is proposed, and the effectiveness is verified through a theoretical analysis and an experiment. As a result, it is clarified that the effective area can be expanded up to a ratio of the distance g between the transmitting and receiving antennas to the inner diameter d of the antenna g/d = 5.0. (C) 2017 Wiley Periodicals, Inc.