In wireless energy transmission systems, resonators with planar geometries have been used in the power transmitter and receiver units to facilitate the transfer of energy. Such planar resonators have geometries that span a substantially flat surface with no dimensional measurement on an axis orthogonal to the flat surface, or where dimensions on an axis along the flat surface are orders of magnitude greater than a dimension on an axis orthogonal to the flat surface. Transmission of power between the transmitter and receiver units relies on inductively or magnetically coupling the respective planar resonators. When the planar transmitter resonator carries an electrical current driven by an external power source, magnetic flux is generally generated in a direction perpendicular to the plane of the transmitter resonator. A planar receiver resonator is then placed within a vicinity of the planar transmitter resonator and is oriented parallel to the planar transmitter resonator such that the planar receiver resonator is able to effectively intercept the magnetic flux generated by the transmitter resonator to produce an electrical current in the receiver unit.
The use of planar resonators is an effective approach for closely coupled wireless power transmission systems to transfer energy between two stationary objects that are in close proximity. For example, in charging pad applications, a planar transmitter resonator is embedded in a charging pad that is placed on a desk. When an electronic device, such as a cellular phone, is equipped with a planar receiver resonator, and is placed on the charging pad, the two planar resonators are orientated parallel to each other along the planes of the resonators. In this parallel orientation, energy can be effectively transferred from the planar transmitter resonator embedded in the charging pad to the planar receiver resonator in the electronic device to charge the electronic device. Because the electronic device is not expected to move on its own, the two planar resonators remain oriented parallel to each other to continuously charge the electronic device until the electronic device is removed from the charging pad.