Electromagnetic absorbers operating within the X band play a critical role in reducing wave reflection, improving impedance matching, and enhancing the performance of radar systems In this study, a three-layer structure consisting of a surface Graphene/Epoxy layer, a porous CNT/Epoxy core, and an aluminum backing plate with a total thickness of 7 mm was designed and evaluated using a dual approach framework: numerical simulation in COMSOL Multiphysics and analytical modeling based on classical electromagnetic theories.

The numerical results indicate that the reflection loss reaches approximately −18.8 dB (corresponding to 98% absorption) around 9 GHz, whereas the analytical model predicts a peak value of −21 dB at the same frequency. Both methods show closely matched trends within the 8–12 GHz band, with deviations becoming more pronounced at the band edges and remaining below 10% near the resonance region. Impedance analysis reveals that minimizing the mismatch between the real part of the effective impedance and the free space value is the primary factor responsible for the reduced reflection at resonance. Furthermore, the geometric sensitivity analysis shows that increasing the thickness of the surface layer shifts the absorption peak toward approximately 8.5 GHz, while increasing the core thickness moves it toward around 9.5 GHz. These findings demonstrate that precise control over the geometry, thickness, and material parameters of each layer enables effective tuning of the frequency response and optimization of the absorber’s performance.