Anisotropic Permittivity Measurement of Materials by the Oblique-Incidence Method

An oblique-incidence measurement method based on the free-space method is proposed for measuring the permittivity of anisotropic materials in the frequency band from 6 to 18 GHz. The oblique-incidence method is calibrated over the full frequency band using the line-network-network (LNN) method. The entire measurement process uses only one sample to measure the permittivity of each anisotropic material under test (MUT) in different principal axis directions. The validity and accuracy of the proposed oblique-incidence measurement method for anisotropic dielectric materials are verified by simulation and measurement results of polytetrafluoroethylene (PTFE) and the honeycomb material.