Complex permittivity extraction using a space-mapping technique

Electromagnetic (EM) simulation is playing an increasingly important role in the product design cycle. Reliable electromagnetic modelling of passive RF and microwave components requires an accurate broadband specification of the material properties that are used in the EM field simulator, and the availability of such information is almost always limited. This article describes a robust low-cost solution for a broadband extraction of the complex permittivity of dielectric substrates using a modified ring resonator technique. The frequency dispersive profile of the complex permittivity is obtained by comparing 3D EM full-wave simulated and measured data. A space-mapping technique is used for fitting the dispersive data to an n-th order Debye model in order to make the whole process time-efficient. Since only the transmission coefficient magnitude is required, the extraction process is insensitive to manufacturing tolerances. The technique is demonstrated for ROGERS RO4350B soft substrate within frequency range 0-20 GHz.