Measurements to estimate the relative permittivity and loss tangent of thin, low-loss materials

A thin layer of Kapton-, Kevlar-, or Tedlar-type materials is sometimes used in the construction of A-sandwich radomes to provide additional mechanical support to the outer skins of the radome, for example. The electrical properties (relative permittivity and loss tangent) of such materials are not always known beforehand at the frequency of interest. It is desirable that they be known in order to predict the likely RF response of the overall sandwich, assuming that electrical properties elsewhere are known. A simple S₁₂ transmission measurement can be carried out to provide measured data that can be used to good effect in a very simple formula (developed hereunder) to provide a useful working estimate for the electrical properties of such additional layers.