Development of extraction techniques for dielectric constant from free-space measured S-parameters between 50 and 170 GHz

This paper is a comprehensive study on Newton–Raphson technique used in millimeter wave frequencies for material characterization. Various algorithms are used for extracting the complex permittivity of a material from measured S-parameters. Efficiency of the methods depends on the initial guess and the accuracy of measured S-parameters for each thickness and frequency band. In this paper, we suggest the initial-value estimation method that helps to estimate a proper value for starting the algorithm. Moreover, an alternative extraction process is modelled that does not require new measured S-parameters or extracting process for each frequency band and thickness with a composed database. The estimation process is conducted partially as V (50–75 GHz), W (75–110 GHz), and D (110–170 GHz) frequency bands.