Measurements of Dispersive and Complex Permittivity Using a Deep-Subwavelength Plasmonic Skyrmion Resonator

A novel method is proposed to measure dispersion and complex permittivity using densely and equally spaced skyrmion modes in a deep-subwavelength spoof localized surface plasmon (SLSP) resonator. The SLSP resonator is ultra-compact, with an electrical size of λ0/89 or λg/27 (λ0is the free-space wavelength and λgis the guided wavelength inside the substrate at the fundamental resonance frequency). Fifteen plasmonic skyrmion resonances are utilized during the measurement. The resonance frequency and the quality factor (Q-factor) are related to the dielectric constant and loss tangent of the material under test (MUT). Through fifteen densely and equally spaced skyrmion modes, the variation trends of the measured dielectric constant and loss tangent of the MUT can be visually observed in a wide frequency band from 0.3 GHz to 10 GHz, reflecting the dispersion characteristics of the MUT. Experimental results demonstrate that the proposed method can effectively measure both solid and liquid materials, with average errors of 3.80% and 4.89% for the dielectric constant and loss tangent, respectively. The proposed method combines a broad working bandwidth and high accuracy for the dispersion and complex permittivity measurements in the microwave frequency.