Surface Impedance Modulation of FSS Composite Absorber for RCS Reduction at Normal and Grazing Incidence

The demands for surface impedance vary when it comes to traveling wave diffraction and specular reflection suppression in absorbing structures across a broad frequency range. To address these conflicting requirements, a composite structure of frequency selective surface and area coated honeycomb (FSS-ACH) structure is developed herein via surface impedance modulation. This structure enables effective suppression of both types of scattering. Simulation results show that the proposed absorber achieves a monostatic radar cross section (RCS) reduction of more than −10 dB at normal incidence within the frequency range of 2–10 GHz. In addition, the first traveling wave lobe is reduced by more than 10 dB for TM polarization at grazing incidence. To validate the proposed design method, samples were fabricated and measured in an anechoic chamber. The obtained measurement outcomes closely corresponded with the simulated results, thus providing solid confirmation of the efficacy of the proposed design approach.