Development of Microwave Attenuator Based on Magnetic Composites and Frequency Selective Surface (FSS) in the X-Band Using FEKO

The development of a magnetic composite based on a silicone matrix containing carbonyl iron (CI), combined with the Frequency Selective Surface (FSS) for radiation-attenuating material (RAM) applications in the X-band (8.2–12.4 GHz), is presented in this work. Four FSS geometries were investigated: square, circular, triangular, and hexagonal. The electromagnetic properties, namely relative electrical permittivity and magnetic permeability, were characterized using a vector network analyzer employing both waveguide and free-space measurement techniques. The attenuation performance was evaluated through reflection loss (RL) measurements and numerically simulated using FEKO software. The stability of the attenuation performance was also assessed for different wave incidence angles (0° to 45°), demonstrating a robust average peak attenuation of −32.1 dB at 11.18 GHz, with optimal resonance values reaching as low as −60.34 dB at an incidence angle of 30°, in good agreement with the simulation results. The results indicate that the capacitive and inductive behavior associated with FSS geometries plays a key role in tailoring the electromagnetic response, demonstrating the effectiveness of FSS-based magnetic composites for controlled attenuation performance.