PROPAGATION OF LINEAR FM SIGNALS IN DIELECTRIC MEDIA

When a wide band electromagnetic wave is propagating in a medium, inhomogeneous behavior of the transfer function leads to absorptive and dispersive frequency selective effects. A general space-frequency approach for analyzing constant envelope, FMCW signal propagation in dielectric material is presented. The theory is based on a general presentation of the medium susceptibility, considering the response of the medium in the frequency domain. Analytical expressions are derived for the temporal group delay and its implication on the chirp along the path of propagation. In particular the attenuation and time delay of electromagnetic signal due to clouds and fog were studied. At millimeter wavelengths, fog attenuation is a function of the fog density, extent, index of refraction of the fog medium, and wavelength.