Exploring the Internal Patterns in the Design of Ultrawideband Microwave Absorbers

Microwave absorbers have been developed by various manufacturing technologies, such as injection molding and machining, in which their design parameters are mainly the external shape of the absorber and the dielectric properties of the material. Here, we use additive manufacturing to design and build absorbers with complex internal patterns. With this new design flexibility, absorbers with internal patterns, when compared with their solid versions, maintained their absorption performance. The absorbers were initially designed and optimized by simulations, built by a three-dimensional printer, and experimentally measured. As a proof of concept, we built absorbers with fractal-type open internal patterns, using filaments with a high loss factor. In the experimental characterization with various angles of incidence, the absorbers with internal fractals showed attenuations greater than 20 dB at frequencies below 15 GHz and significantly better attenuations above 15 GHz, over 30 dB. The results demonstrated that fractal absorbers can attenuate 99% or more of the incident radiation over a wide frequency range, showing that internal patterns could be used as an additional design parameter.