Extraction of Permittivity and Permeability for Ferrites and Flexible Magnetodielectric Materials Using a Genetic Algorithm

A hybrid approach, based on the two-dimensional finite-element method (2-D-FEM) and a genetic algorithm (GA) optimization, is used to extract relative permittivity and permeability of ferrites and flexible magnetodielectric composite materials over wide frequency bands. S-parameters of a material under test (MUT) placed into a coaxial fixture are measured by a vector network analyzer and simulated using the 2-D-FEM code. The GA optimization procedure is then used to minimize the discrepancies between the measured and simulated S-parameters by iteratively searching the possible best permittivity and permeability. Multiterm Debye models of wideband complex permittivity and permeability are employed here for a frequency-dispersive MUT. This greatly reduces the number of unknowns in the GA optimization. The proposed method is tested with PTFE and a virtual magnetic material.