Characteristic Mode Analysis and Design of Metaloop Antenna for Wireless Power Transfer

An electrically-large metaloop antenna of even near-field magnetic field distribution is designed in the 2.4-GHz band for wireless power transfer (WPT). Structurally, the metaloop antenna is formed by capacitively-loaded twin-wire loop. Characteristic mode analysis (CMA) is used for revealing the operating principle of the proposed antenna from a mode perspective. It is found that by exciting multiple working modes, the proposed antenna achieves a larger area of even H-field distribution than that the current loop mode does at a distance of 10 mm above the loop plane, characterized by 1.5-dB ripple for the field component normal to the loop. Therefore, the proposed metaloop antenna can be a good candidate for wireless power transfer toward multiple receivers.