Advances in non-planar electromagnetic prototyping

Abstract

The advent of metamaterials has introduced new ways to manipulate how electromagnetic waves reflect, refract and radiate in systems where the range of available material properties now includes negative permittivity, permeability, and refractive index. While analytical and numerical tools are equipped to analyze the complex configurations of materials and geometry that constitute many proposed devices, realizations have been limited in part due to fabrication. The fabrication processes used to construct the majority of metamaterial media are optimized to produce 2D products, including printed circuit board and microfabrication techniques, making the transition from two dimensional proof-of-concept to three dimensional prototype challenging. In the last decade, several reports have documented the use of additive manufacturing to fabricate 3D electromagnetic devices, including gradient index lenses at both microwave and optical frequencies, and radio frequency lenses that attain resolution beyond the diffraction limit. Though primarily used for facsimile display models, additive manufacturing is uniquely capable of addressing the needs of 3D electromagnetic designs which incorporate non-planar geometries and material inhomogeneity. The application of additive manufacturing to functional electromagnetic devices, however, is still uncommon, as the simultaneous layering of conductive and insulating materials remains complicated. To further advance the start of the art, we report our application of additive manufacturing in conjunction with other fabrication tools to fabricate several electromagnetics devices. The first involved the design of an artificial magnetic conducting substrate to enhance UHF RFID tags in close proximity to metal surfaces, which normally detune antennas and destructively interfere with any transmitted waves. The substrate incorporates 3D metamaterial unit cells, the fabrication and assembly of which were enabled by additive manufacturing. Additive manufacturing was then used to fabricate lightweight, self-supporting interconnected metamaterial structures. These structures exhibited minimal losses, making them ideal for a plano-concave microwave lens capable of focusing at 10GHz with the highest gain measured for a metamaterial lens to date. Other achievements include the fabrication of frequency selective surfaces and antenna elements conformal to non-planar surfaces. Though many challenges remain to be overcome, it is clear that additive manufacturing has significant potential to contribute to the study and fabrication of electromagnetic elements.