Microwave metamaterial sensor with a high Q factor to measure complex permittivity based on cross-polarization conversion

In this paper, a solid-state complex permittivity sensor is proposed based on cross-polarization conversion in the microwave band for what we believe is done for the first time. The sensor consists of a circular split-ring resonator structure, a dielectric substrate F4B, and a metal backplate. The design realizes a 95.5% polarization conversion ratio (PCR) at 13.35 GHz with a high Q of 76.87. Anisotropy theory is used to analyze the polarization conversion characteristics. The complex permittivity sensing function is experimentally verified using two materials under test, and the experimental and simulation results are in agreement. The design has the advantages of narrow-band cross-polarization conversion, high Q-factor, and wide incidence angle, which can provide some helpful guidance in the field of metamaterials sensing.