Patched-Wall Quasistatic Cavity Resonators for 3-D Wireless Power Transfer

Abstract

Traditional wireless power transfer (WPT) systems are largely limited to 1-D charging pads or 2-D charging surfaces and therefore do not support a truly ubiquitous device-powering experience. Although room-scale WPT based on multimode quasistatic cavity resonance (QSCR) has demonstrated full-volume coverage by leveraging multiple resonant modes, existing high-coverage implementations require obstructive internal conductive structures, such as a central pole. This letter presents a new structure, termed the patched-wall QSCR, that eliminates such internal obstructions while preserving full-volume coverage. By using conductive wall segments interconnected by capacitors, the proposed structure supports two complementary resonant modes that cover both the peripheral and central regions without obstructions within the charging volume. Electromagnetic simulations show that, by selectively exciting these two resonant modes, the proposed structure achieves a minimum power-transfer efficiency of 48.1% across the evaluated 54 m^3 charging volume while preserving an unobstructed interior space.

Figures (6)

• Figure 1: Simulated surface-current distributions and magnetic-field patterns of the proposed patched-wall quasistatic cavity resonator for the two supported modes: (a) current distribution of the pole-independent (PI) mode, (b) current distribution of the surface-Helmholtz (SH) mode, (c) magnetic-field magnitude for the PI mode, and (d) magnetic-field magnitude for the SH mode. The PI mode concentrates magnetic flux near the periphery of the cavity, whereas the SH mode produces a strong central field without requiring an internal conductive pole.
• Figure 2: Geometry and tunability of the proposed patched-wall resonator. (a) Resonator structure, dimensions, and qualitative current-loop paths associated with the SH and PI modes. (b) Resonant frequency versus capacitance for the two supported modes. (c) Resonant frequency versus geometric parameters $p_{\mathrm{ctr}}$ and $p_{\mathrm{cor}}$. (d) Simulated quality factor versus $p_{\mathrm{ctr}}$ and $p_{\mathrm{cor}}$ for the SH and PI modes. These results show that the operating frequencies can be tuned through both lumped capacitance and structural geometry while maintaining high quality factors.
• Figure 3: Selective mode excitation in the proposed resonator. (a) Drive coil geometry and the coordinate system used for excitation. (b) Real part of the input impedance as a function of frequency for various drive coil locations. The results demonstrate that varying the drive coil position and operating frequency allows for the selective excitation of the PI and SH modes.
• Figure 4: Simulated wireless power transfer efficiency distributions for the proposed patched-wall resonator with $p_{\mathrm{cor}} = p_{\mathrm{ctr}} = 0.6$. (a)--(c) Efficiency on the $z=0$ plane for SH mode, PI mode, and dual-mode operation, respectively. (d)--(f) Efficiency on the $x=0$ plane for SH mode, PI mode, and dual-mode operation, respectively. Dual-mode excitation combines the complementary coverage of the two resonant modes and suppresses low-efficiency regions throughout the charging volume.
• Figure 5: Coverage statistics of the simulated power-transfer efficiency as the geometric parameters are varied. The rows correspond to SH-mode, PI-mode, and dual-mode operation, while the columns show the minimum, 10th percentile (P10), median, and 90th percentile (P90) efficiencies within the evaluated volume. The maps summarize how the geometric parameters $p_{\mathrm{cor}}$ and $p_{\mathrm{ctr}}$ influence volumetric coverage.