Laminated Miniaturized Low-Frequency Metamaterial Block for Near-Field Wireless Power Transmission Applications

We present a miniaturized and laminated metamaterial (MM) block, which is formed using an extremely compact stacked unit cell consisting of a double-layer spiral connected in series with a chip capacitor, with a lateral size on the order of 1/20 000 of the operating wavelength. The unit cell enables the construction of an MM sample with an operating frequency as low as 325 kHz, provided a 1.8-nF capacitor, and the stacking compactness is configured as 1.05. A resistor-inductor-capacitor (RLC) circuit simulation method is proposed to extract the relative permeability of the low-frequency MM block with 3-D layout, which eliminates the wave-port configuration and 2-D boundary limitations. Experiments confirm that the proposed MM block has enhanced resonant strength at lower resonant frequencies. Efficiency measurements performed for a wireless power transmission (WPT) prototype reveal a 34.5% enhancement of the power transmission efficiency (PTE) at a 120-mm working distance using the fabricated MM sample, which is nearly three times that of the original prototype. In addition, the anti-misalignment performance of the coils is tested at a 100-mm distance, revealing an enhanced misalignment tolerance of 58.3% using the MM sample when the target PTE is set to 80% that of the alignment case. This excellent performance and compact size make the proposed laminated MM block extremely attractive for many low-frequency WPT applications with limited dimensions, such as telemetry systems for rotating machineries.