Design of an octagonal-shaped curved sensor antenna for dielectric characterization of liquids

In this study, an octagonal microstrip antenna with a 3D-printed curved-shaped substrate was proposed as a microwave sensor for measuring the dielectric constants of liquids. During the development of the sensor, an octagonal radiating plane was placed on the curved structure by adding an empty semi-cylindrical structure to the planar substrate. The 30 × 30 × 1 mm3 substrate was designed using PLA material with a dielectric constant of 2.41, and the conductive planes were formed using copper tape. The sensor was analyzed using full-wave electromagnetic computation software, and the reflection coefficients were obtained through simulations. Using simulation-obtained reflection coefficient data, the multi-layer perceptron (MLP) was utilized to estimate the dielectric constant. Then, the sensor was manufactured using a 3D printer, and the reflection coefficient measurements of the antenna were performed by filling the curved structure with liquids of varying characteristics. The MLP, which has an APE of 0.20 % for training and 1.52 % for testing, made predictions with an APE of 0.172 % for the simulation of the five materials considered and 1.524 % for the measurement data. It has been observed that the variable dielectric constant results in differences in the resonant frequency and amplitude. The good agreement between simulation and measurement results demonstrates that the proposed sensor can be utilized effectively for measuring the dielectric constants of liquids.