Robust design of compact microwave absorbers and waveguide matched loads based on DC-conductive 3D-printable filament

The design concept of effective microwave absorbers and compact matched loads based on 3D-printable lossy nanocarbon-based composites with filler content above the percolation threshold is proposed. The DC-conductive (σ _DC = 0.39 S m^-1) 3D-printable filament based on poly(lactic) acid filled with 12 wt.% of multiwalled carbon nanotubes was used. The electromagnetic properties of 3D-printed pyramidal regular structures were experimentally investigated and numerically simulated in 12-18 GHz (Ku-band) and 26-37 GHz (Ka-band) frequency ranges. Within the proposed model the structures under study were considered as graded refractive index material. The optimal geometrical parameters of designed microwave components were successfully evaluated using numerical modeling. Tested components demonstrate remarkable shielding efficiency (> 20 dB) within whole Ku- A nd Ka-bands and are suitable for practical application related to effective absorption of microwave radiation. The production of 3D-printable materials with controlled and predicted losses offers the possibility for miniaturization of 3D printed microwave components, such as absorbers and loads. The developed technique, estimating the geometrical parameters of the components vs dielectric properties of the conductive filament, could be used as a versatile platform for predesign of compact microwave devices taking into account constituent dielectric parameters of available printable materials and filaments.