A symmetrical planar spiral coil-based wireless power transfer system with embedded split-ring resonator

Wireless Power Transfer (WPT) via Magnetic Resonant Coupling (MRC) has emerged as a promising technology for contactless energy delivery, especially for Internet of Things (IoT) and mobile devices. Planar capacitor-loaded Printed Spiral Coils (PSCs) have been widely adopted due to their manufacturability, compactness, and cost effectiveness. However, limited power transfer efficiency continues to hinder their broader adoption. In this work, we present a symmetrical MRC-WPT system using identical PSCs fabricated on FR-4 substrates, each measuring 100 mm × 100 mm × 1.6 mm and resonating at 13.33 MHz within the ISM band. To improve magnetic coupling and impedance matching, a split-ring resonator (SRR) is integrated at the centre of the PSCs. Experimental results demonstrate that the proposed SRR-enhanced system achieves a peak efficiency of 46.13%, representing an approximate 3.8% relative improvement over the 44.45% efficiency of the conventional PSC system. While the improvement in peak efficiency is relatively modest, it demonstrates the potential of SRR integration to enhance near-field power transfer performance. It is also to be noted that, the SRR-enhanced system also demonstrates greater tolerance to coil misalignment and separation discrepancies, contributing to improved robustness in practical deployment scenarios. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.