Direct modeling of Close-range Brightness Temperature Transfer from Anisothermal Calibration Targets

Based on a formerly reported direct modelling methodology for thermal radiation reception by antenna in close range, this work investigates the near-field brightness temperature (BT) transfer process from calibration target to antenna and particularly concerns the cases of targets with temperature distributions. Specifically, the coated pyramids array and horn antennas are considered, and the focused temperature profiles include constant temperature, linear difference, and tip loss. The scenarios are numerically simulated and solved by 2-D finite difference time domain algorithm (FDTD). Results show that the temperature magnitude weigh the overall level of transmitted BT, but not the main affecting factor compared with antenna observation distance and main-beam efficiency. Also, the physical temperature deviation between pyramid tip and reference decreases in received BT results. This work shows the capability of the proposed methodology to deal with the situation of anisothermal calibration targets, and its potential to provide reference for practical applications when expanded to 3-D.