A Self-Gap-Correction Method for Accurate Permittivity Measurement Using the Hybrid Optimization Algorithm

Abstract

A novel self-gap-correction method for accurately measuring the broadband permittivity of materials based on the transmission/reflection theory is proposed. This method relaxes the fully filled assumption of the test specimens and realizes the self-correction of air-gap effect without requiring its exact size. It is based on a reliable quantitative relationship between the “true” permittivity and the gap size. A combination strategy of the electromagnetic finite-element simulation and a hybrid optimization algorithm is employed to rapidly extract the “true” values of the gap size and permittivity. This is accomplished by minimizing the errors between the measured and the simulated scattering parameters. Furthermore, combining the advantages of the genetic algorithms (GAs) and the gradient-descent method, the hybrid optimization technique has a high computational efficiency with only one optimization variable. The high accuracy and practical suitability of the proposed method are validated through experimental tests on different materials. A good agreement is achieved between the extracted values of gap size and permittivity with the ideal “true” results. Moreover, its computation time is almost one-half less than that of the conventional pure GA method.