Measurements at 94 GHz with an imaging radar

As part of its mm-wave program the Swedish National Defence Research Institute in Linkoping has developed an imaging combined radar/radiometer system at 94 GHz to investigate the emission, absorption, and reflection properties of matter at this frequency, and to develop data handling and presentation techniques for various purposes. Radar measurements made with the 94-GHz radar with 50-ns pulse length and 0.5-deg beam width are presented. Snow-covered terrain with trees and open ground was observed from a tower between 4 and 54 deg depression angles. The normalized radar cross section has been determined for each angular resolution cell with a 70 x 50 deg section of the terrain, and is presented in image form. Various image representation types have been examined, including color coding which uses range and intensity information to give a perception of the scenery close to the visual one, and which offers the possibility of seeing strong radar reflectors. It is found that the average backscatter from snow in the observed case was stronger than for trees, and its spatial distribution exhibited some deviation from log-normal for parallel transmit and receive polarizations.