3-D-Printed Doubly-Curved Multilayer Tri-Band Frequency Selective Surface

Advances in computational design methods have enabled the development of increasingly sophisticated frequency selective surfaces (FSSs). However, manufacturing these complex designs on doubly-curved shapes remains challenging. In this work, we design, fabricate, and experimentally validate an additively manufactured, doubly-curved, multimaterial, and multilayer FSS subreflector for L passband and Ku and Ka stopband frequencies. By employing this subreflector in a Cassegrain antenna configuration, broadband satellites operating in the Ku-Ka-bands can gain access to L-band frequencies without the need for separate antenna systems. To achieve the desired tri-band frequency response, the FSS elements are first synthesized using periodic level set functions with a target passband from 1 to 6 GHz and stopbands from 17.7 to 20.2 and 27.5 to 30.0 GHz. Then, a planar FSS sample is 3-D-printed using fused filament fabrication (FFF) for the dielectric layers and direct ink write (DIW) with silver nanoparticle ink for the conductive layers. Sample testing in a free space focused beam indicates good agreement with the simulation results. Next, spatially variant lattices (SVLs) are employed to map the synthesized elements onto a hyperbolic surface and advanced, nonplanar 3-D-printing techniques are implemented to manufacture the doubly-curved FSS subreflector. These techniques greatly improve surface quality and enable the printing of multiple layers of continuous conductive patterns on curved surfaces. To demonstrate the performance of the subreflector, it is tested in a Cassegrain antenna system on a compact range with experimental results showing fair agreement with simulation results. Overall, these findings demonstrate the potential for advanced additive manufacturing (AM) to produce high-performance, conformal FSS structures for next-generation radome and spectral filtering applications.