Determination of the Optimal Sample Size for Measurement in a Coaxial Transmission Line

The article presents the results of measuring samples of material of various lengths. The electrodynamic parameters of the NiZn based ferrite material based on zinc nickel monoferrite were measured using a coaxial transmission line in the frequency range 8 - 12 GHz. For this group of materials, it is important to know the electrodynamic characteristics. In this regard, it is necessary to study the properties of the materials obtained in different frequency ranges. The manufacture of new materials is a laborious and complex process. It is not always possible to obtain the required amount of the required material for measurement in order to fill the entire transmission line completely. Samples of material of different lengths were made: from 0.06$\lambda$ to 1.08$\lambda$. Based on the obtained dependences, it can be seen that with increasing sample length, the obtained values begin to converge to certain values. It is shown that the length of the material sample in the coaxial transmission line, for more accurate values, should be equal to or greater than the wavelength of the middle of the frequency range.