Reflection loss field visualization of curved RAS based on scanning free-space measurement and curvature compensation using perfect electric conductor

Abstract

Electromagnetic properties of radar absorbing structures (RASs) are highly affected by their curvatures. Therefore, novel full-field curvature compensation methods in the reflection loss evaluation of curved RASs are proposed. These methods are commonly based on the scanning free-space measurement (SFM), whose curvature compensation method is based on the measurement of the actual perfect electric conductor (PEC) or the PEC reflection loss function-based prediction, which allows the analysis of the original reflection loss of a curved RAS. In the first method, an actual PEC specimen with the same shape as the RAS to be evaluated is used, and the full-field reflection loss of the PEC is obtained by the SFM. As a measure, when the PEC specimen is not available, the second method using the PEC reflection loss function-based prediction is also proposed to obtain the full-field reflection loss of the PEC. This method can predict the reflection loss map of the PEC quickly by defining the PEC reflection loss function according to the curvature and incident angle using the data from measurement. To determine the PEC reflection loss function, it is necessary to secure the reflection loss maps of the PEC specimens with constant curvatures as database, which is also prepared easily by the SFM. Therefore, once they are measured, it can be applied to RASs with various curvatures based on simple compensation. The database for the PEC reflection loss maps with various constant curvatures is ready in the SFM system, and this curvature compensation method can be performed in real time during the scanning. The two methods are validated by comparing each other in double-curvature and airfoil-shaped RASs.