Microwave scattering from saline ice using plane wave illumination

Radar systems used to generate ground truth data, for the scattering properties of distributed targets are generally operated in the near zone region of the antenna. These systems usually use antennas whose illumination of the distributed target contains a wide range of incidence angles. It is desired to measure the scattering properties of targets as a function of incidence angle which requires some type of inversion of the measured results. This problem can be overcome by applying the compact range antenna concept. A parabolic reflector with an offset feed effectively propagates a plane wave of uniform phase over an area approximately equal to the diameter of the reflector and at ranges up to about .5 * D²/λ, where D is the reflector diameter and λ is the wavelength. For the first time, this antenna concept has been used to study the scattering response of smooth, snow covered and rough saline ice grown under laboratory conditions. By coupling the compact range antenna with a wide-band (2 to 18 GHz) network analyzer based radar, the authors have achieved exceptional definition of the near normal scattering response of the ice surface and subsurface. This approach is likely to have broad utility in a variety of other geophysical applications including studying the scattering response of the ocean, soils and vegetation