Symmetric coplanar waveguide sensor loaded with interdigital capacitor for permittivity characterization

Abstract

This article presents the developing of interdigital capacitor (IDC) based symmetric coplanar waveguide (CPW) sensor to characterize the complex permittivity of unknown dielectric sheets. The symmetric structure is realized by using two identical 3 dB CPW dividers where each branch is loaded with an IDC unit. The proposed method is designed using three, five, and seven fingers of the IDC unit, and the measurement sensitivity is analyzed accordingly. The permittivity of tested samples is extracted by the genetic algorithm. To validate the robust sensing performance of the proposed method, simulation and experimental tests are performed and analyzed, and the accuracy is compared with published values. The proposed method gives the maximum error of 3.42%. With the feature of high-sensitivity, the proposed sensor can be used as an excellent candidate for determining the permittivity of materials in microwave frequencies.