APPLICATION OF PLANE-WAVES FOR ACCURATE MEASUREMENT OF MICROWAVE-SCATTERING FROM GEOPHYSICAL SURFACES

We utilized the concept of a compact antenna range to obtain plane-wav e illumination to accurately measure scattering properties of simulate d sea ice,We also made simultaneous measurements using conventional an tennas. Measured scattering coefficients obtained with the plane-wave system at 10 GHz decreased by about 35 dB when the incidence angle inc reased from 0 degrees to 10 degrees. Scattering coefficients derived f rom data collected with the radar system at 13.5 GHz using conventiona l far-field antennas decreased by about 20 dB over the same angular re gion. This demonstrates that the far-held properties of a widebeam ant enna are inadequate for measuring the angular scattering response of s mooth surfaces. We believe that application of the compact antenna ran ge concept for scattering measurements has a wide range of application s and is the solution to the long-standing problem of how to directly measure scattering consisting of coherent and incoherent components.