Investigation of microwave interaction of EMC absorber material by free-spaces measurement technique

Keyword: Free-spaces measurement tecnique, S Parameters, Reflection Transmission TRL calibration, Dielectric In the study it was tried to determine the electrical properties of ferrite slab as microwave absorber at low frequency rate (DC- 100 MHz) between 5-15GHz frequency. Values which were measured and calculated were tested with nonmagnetic glass and delrin slab. Free-spaces measurement tecnique was used for all the measurements. Reflection (S11) and transmission (S21) coefficient values were read from Vectorel Network Analyzer. Dielectric properties of ferrite, glass and delrin were determined by calculating with complex S parameters. For determining the dielectric properties: 1) Measurement of reflection/transmission coefficient, 2) Measurement of multi layer transmission coefficient, 3) Measurement of different thickness slab transmission coefficient methods were used. It was fixed that the 3.rd method was used firstly in this study. In the used frequency range, multi phase transition in inevitable for b wave number, because of the similarity of thickness of the material and the wave length. For this reason a new algorithm was developed to determine the b wave number values. It was recognized that all the refraction index values taken by these three methods were congenial with each other and literature. On the other hand, it was determined that the thickness of the materials was (especially slab thickness equal l/4) more oppressive than inner properties for the total signal intensity which were reflected and transmitted. At the same time, it was recognized that ferrite acts as half transparent material between 5-15GH frequency ranges.