Measurements of the Complex Permittivity of Low Loss Polymers at Frequency Range From 5 GHz to 50 GHz

Complex permittivity of Polytetrafluoroethylene (PTFE), Polypropylene (PP), Polyethylene (PE) and cross-linked Polystyrene (Rexolite), has been measured at frequency range from 5 GHz to 50 GHz. Measurements have been performed in two cylindrical cavities employing several quasi
$\text{TE}_{0 \mathrm{mn}}$
modes excited in samples under test. Measurement uncertainties for the real part of permittivity were
$\pm$
0.5% while for the imaginary part of permittivity in the range from
$\pm$
8% for the lowest loss materials to
$\pm$
3% for Rexolite. It has been confirmed that the real part of permittivity of all measured polymers is constant in the microwave frequency spectrum to within measurement uncertainties, while the dielectric loss tangent values vary with frequency