An Aperiodic Subwavelength Dipole Structure for Enhancing Near-Field Wireless Power Transfer

In this letter, a sparse, aperiodic subwavelength dipole structure (ASDS) is proposed for enhancing wireless power transfer in the near field (NF). The ASDS can have applications in areas such as wireless charging of small electronics, imaging, and proximity sensing. The working principle is inspired by a shifted-beam NF focusing method for similar antenna structures, as well as previous examples of using loaded metawire arrays for far field beamforming. The ASDS is simulated for distances between 1
$\lambda$
and 3
$\lambda$
at 2.4 GHz in the industrial, scientific, and medical band. All dipole elements are parasitically excited by a single source dipole at the center. The design is numerically optimized by adjusting the dipoles' lengths and relative position; a figure of merit is proposed to quantify overall performance. Significant improvement in power transfer efficiency is obtained, compared to reference examples such as a uniformly excited array. The simplicity of the proposed ASDS also makes it advantageous, as no feed networks, multiple excitations, or active components are required.