Design of a Small Array Antenna with an Extended Cavity Structure for Wireless Power Transmission

This paper proposes a design of a small array antenna with an extended cavity structure for wireless power transmission. The proposed array element consists of a square radiating loop, which is designed to resonate at 5.8 GHz, and an extended cavity structure to reduce the mutual coupling between adjacent elements. We derive the optimal element number in a limited space by considering the input power for each element, fabrication cost, and aperture efficiency of the system. To verify the suitability of the proposed a small array with an extended cavity structure, a 2 × 2 downscaled array antenna is fabricated and measured in a full anechoic chamber. The results confirm that the proposed antenna element with an extended cavity structure is suitable for wireless power transmission systems; the proposed array has a transmission efficiency of about 1% at a distance of 2 m when the array is applied to both transmitting and receiving antennas.