Electromagnetic and thermal analyses of radiometer calibration targets

A novel approach for the analysis of millimeter-wave radiometer calibration target performance is presented. Analysis of wedge-profile targets is facilitated by performing both an electromagnetic and thermal analysis of the target. The scattered, transmitted, and internal fields of the wedge target, illuminated in the principal direction by a plane wave, are analyzed using the coupled-wave algorithm. From a knowledge of these fields, the wedge trough-to-tip absorptivity profile is computed. The two-dimensional temperature distribution for a heated wedge is then determined from a solution to the steady-state heat equation. Using the absorptivity and temperature profiles, the radiative transfer equation is solved to obtain the thermal emission from the wedge calibration target. Significant effects resulting from the inhomogeneous temperature distribution are quantified. Motivation for this investigation derives from a need to analyze the performance of microwave and millimeter-wave targets and develop wideband target design criteria