Alignment and illumination issues in scaled THz RCS measurements

Radar cross section (RCS) measurements are widely employed for the target identification of objects such as aircraft. The RCS of large, complex geometries is usually determined in a well defined, scaled experimental setup. In such a setup, the measuring frequency equates the frequency of interest multiplied by the scaling factor of the model. For high scaling factors, frequencies well above 100 GHz result so that conventional microwave equipment reaches its technological limits. In this paper, we discuss the use of a fiber coupled terahertz time domain spectroscopy system for angle dependent RCS measurements. Several measurements on simple objects like metal plates with corresponding simulations are performed. We also investigate how angular misalignment and displacement of the scatterer effects the measurement results. Moreover, we discuss the influence of non planar incident wavefronts and compare experimentally obtained data to simulations using an enhanced physical optics model.