Permittivity Measurements in Millimeter Range of PTFE Foams

This letter presents the results of permittivity measurements on a series of Polytetrafluoroethylene (PTFE) foams with different porosities. The difference in porosity greatly influences the dielectric properties of these materials. The aim of this letter is to explore the relationship between the permittivity and porosity. Nondestructive permittivity measurements were done using a complementary split-ring resonator (at 35 GHz) and verified using a free-space transmission method (at 60 GHz). The permittivity correlates linearly with the foams porosity.