Abstract: An example transmitter comprises a housing with a top surface that allows for placement of a ring device to be wirelessly charged by the transmitter, the ring device is a device that is capable of receiving a power from the transmitter. An antenna, placed inside of the housing and disposed below the top surface, configured to transmit radio frequency (“RF”) waves to the ring device, where a radiator of the antenna has a circular shape that is positioned coplanar with the inner surface of the housing and the radiator has a certain thickness that is defined by an inner radiator diameter and an outer radiator diameter; and the inner radiator diameter of the radiator is substantially equal to the first inner ring diameter of the smallest ring device, and the outer radiator diameter of the radiator is substantially equal to the first outer ring diameter of the largest ring device.

Abstract: A wireless-power transmitter including an antenna including a plurality of power-transfer points. The antenna is configured to operate in multiple modes. The multiple modes include a standby mode and a single receiver power-transfer mode. The standby mode provides a signal to the antenna at predetermined time intervals. The signal causes the antenna to transmit electromagnetic energy that is below a threshold amount, and produce an electric field that is substantially equally distributed at each of the power-transfer points. The single receiver power-transfer mode is activated upon a wireless power-receiver coupling with one of the plurality of power-transfer points such that (i) a portion of the electric field is greater at the one of the plurality of the power-transfer points than at any other of the power-transfer points, and (ii) electromagnetic energy is transferred from the antenna to the wireless power-receiver at the one of the plurality of the power-transfer points.