Noncontact measurement of complex permittivity based on the principle of mid-range wireless power transfer

The measurement of complex permittivity of materials is of significant importance in scientific research and industrial applications. In this paper, we introduce the strongly coupled magnetic resonance previously used in high-efficiency midrange wireless power transfer to the noncontact measurement of the complex permittivity of materials. Theoretical analysis, full-wave simulation, and experimental measurements will show that the introduced high- Q-factor resonance can be used to effectively improve both the measurement sensitivity and the impedance matching to the instrument, avoiding the major weaknesses of the traditional magnetic induction method. The measurement setup can be easily calibrated for both solid and liquid materials and can provide the flexibility in noncontact measurement at a variable distance. We expect a wide range of applications to emerge from this novel approach.