Polarimetric scattering properties of natural targets at 80 GHz

Although a large volume of data describing the properties of the scattering matrices of natural targets has been presented in the literature, the vast majority of these data were measured at frequencies under 10 GHz, very little polarimetric data has been presented at millimetric wavelengths. Interest in the scattering properties of terrain in this band has been stimulated by the interest in collision avoidance radars for use on motor vehicles. These will operate at 77 GHz. Measurements of the scattering matrices of a variety of natural targets are described, and an overview of the principal scattering properties is given. A simple parameter referred to as the cross polar ratio (CPR) is then introduced and shown to characterise the scattering matrices measured of tree canopies. A discussion of the depression angle dependency of the scattering matrix of grass is then presented