This thesis investigates how electromagnetic waves interact with radar absorbing material (RAM) panels, with a focus on how controlled geometric modifications (defects) influence microwave reflectivity since real-world panels are rarely perfectly flat. The study examines the relationship between material geometry and electromagnetic response at radar frequencies using three-dimensional (3D) printed electrical conductive samples with systematically introduced geometrical defects. 

Measurements were performed using the Naval Research Laboratory (NRL) arch method, which enables near field, non-contact evaluation of reflection characteristics over a broad frequency range. The samples were fabricated using 3D printing, which allowed for the control of geometric parameters such as size and patterns. Reflection data were collected for four different sample series and analyzed using both frequency data and statistical estimations. The measured results show that variations in surface geometry affect the resonant frequency and reflection magnitude compared to a planar reference sample. In several cases, increased geometric complexity leads to shifts to lower frequencies in resonant behavior and changes in absorption performance. 

To quantify these effects, polynomial regression analysis of resonance shifts and confidence intervals was applied based on Student’s t-distribution. The results show that different sample series behave with different levels of consistency. Sample series 1 and 2, which have step size in concave and convex geometries as the parameter that varies, follow trends that match the fitted model well and agree with the uncertainty ranges. Sample series 3 and 4, which have a checkerboard pattern that varies, show more variation in the data and do not follow a clear relationship between geometry and response.