Characterization of dielectric materials with a modified DIRECT algorithm

© 2016 European Association of Antennas and Propagation. An alternative technique is presented for the determination of the electrical properties of dielectric materials. Two dielectric elements are placed inside a rectangular waveguide and complex scattering parameters are used to extract their relative permittivity values. The technique is based on the modification of the DIRECT algorithm to cope with cost functions with large number of minima. To improve the reliability of the algorithm, a multimode analysis has also been introduced. Results demonstrate that considerable improvement in the prediction of the dielectric materials is obtained when the new algorithms are used.