Measurements of Dielectric Materials of High Anisotropy Ratio With TM0n0 Cavity

Low-loss dielectric laminates that are routinely used in manufacturing of printed circuit boards (PCBs) are known to be anisotropic. The out-of-plane component of the dielectric permittivity have been so far determined using one of several available methods. The approach based on the
$\text{TM}_{0n0}$
cavity and a relatively simple characteristic equation previously presented in the literature is known to be accurate when thin and semi- isotropic samples are measured. However, its accuracy suffers for thick samples of large permittivity and high anisotropy ratio. In this paper we present a novel post-processing routine that allows us to extract material properties also for such problematic cases. The approach is based on an anisotropic model based on the Radial Mode Matching (RMM) method and accounts for major sources of errors that usually affect the accuracy of such measurements. To the best of our knowledge, no similar approach have been reported so far.