Design of electromagnetic wave absorbers using frequency selective surfaces

Conductor-backed electromagnetic wave absorbers with periodically arranged pattern conductors on the surface layer (pattern absorbers) were designed. The pattern absorbers in this work were composed of a patterned layer acting as a frequency selective surface, such that the pattern served as a resonator together with a back reflector. Electromagnetic wave simulations predicted that the absorption characteristics of these devices could be tuned by varying the shape, alignment, and occupied area ratio of the pattern conductor so as to match the surface impedance to that of free space. Pattern absorbers with various pattern shapes were fabricated operating at 2.45 GHz and their absorption characteristics were evaluated. The experimental results were found to agree with the theoretical predictions and it was experimentally shown that a patterned electromagnetic wave absorber fabricated using a magnetic material exhibited wideband characteristics. A scaling law was also found to hold between the pattern size and absorption center frequency, which will allow the design of electromagnetic wave absorbers that can operate over a wide frequency range with excellent absorbing characteristics.