Contactless detection of state parameter fluctuations of gaseous media based on an mm-wave FMCW radar

In this contribution, we present an approach on the fluctuation detection of gaseous media concerning their state parameter, i.e., concentration, pressure, and temperature. Dielectric mixing equations that link the gas permittivity with the gas concentration and pressure are introduced and discussed. Furthermore, we prove the small temperature influence on the gas permittivity, because of the obvious temperature-pressure dependence of gaseous media. To verify the suggested gas permittivity theory, a pressure-resistant test container was constructed and built up. By means of a highly precise millimeter-wave radar system, we performed numerous test series on different gases for various investigations.