High-sensitivity structure for the measurement of complex permittivity based on SIW

In this study, a substrate integrated waveguide (SIW) combined with complementary split-ring resonator (CSRR) structure is proposed for high-sensitivity measurement of complex permittivity of low loss material at 2.45 GHz. The simulated results demonstrated that the small changes can be sensed through loading the CSRR structure on both sides of SIW. Then, the experiments are performed on various dielectric samples to validate the proposed structure by measuring the particulate samples with different moisture contents and solution samples in different mixed volume ratio. The measured results show that the sensitivity of the proposed SIW with CSRR structure is always higher than the structure without CSRR. Furthermore, neural network based on actual experimental scattering parameters is used for obtaining the permittivity of samples under test. The experimental values agree well with the theoretical values, and the relative errors of e ′ and e ′ ′ are <5 and 10%.