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We present the design and characterization of fully additively manufactured (AM) SubMiniature version A (SMA) connectors for use up to 18 GHz. Three-dimensional printed connectors can be directly integrated into the radio-frequency (RF) circuit without post-process bonding and can be fabricated into unusual shapes. The flexibility this affords in the manufacturing process offers significant advantages, especially for applications that need to meet strict size and volume constraints. To that end, we describe modifications to the traditional SMA design that better enable AM fabrication. A variety of different connector geometries were printed and fully characterized both electromagnetically and mechanically. Experimental measurements up to 18 GHz demonstrated good RF performance with low insertion losses (< 0.5 dB). Mechanical testing showed that the printed connectors could withstand up to 4.5 kg of direct force for extended periods of time without damage to the printed threads or other connector parts. Additionally, the printed connectors demonstrated good RF performance after repeated use. [ABSTRACT FROM AUTHOR]

We demonstrate a new method for realizing modified Luneburg lens antennas with nearly continuously graded permittivity profiles in three‐dimensions. The method used a quasi‐conformal transformation optics (QCTO) approach to modify the geometry and permittivity of a spherical Luneburg lens to have a flat surface for convenient integration of antenna feeds. The modified lens was then fabricated using Fused Deposition Modeling (FDM) printing with an effective media approach that employs space‐filling curves. The method was validated by designing and fabricating a modified Luneburg lens antenna designed to operate in the Ka‐band. The antenna performance of the sample was measured experimentally and shown to compare well to predicted results using full wave simulations. The device was able to achieve a reasonably high degree of beam steering (ie, −55° to +55°) over the entire Ka‐band. We believe this new approach provides a cost‐effective and scalable means of realizing practical passive beam steering lenses that operate over a broad range of frequencies. [ABSTRACT FROM AUTHOR]

We demonstrate a new method for realizing Luneburg lens antennas with nearly continuously graded permittivity profiles in three dimensions. The method combines fused filament fabrication, a nearly ubiquitous additive manufacturing technique, with an effective media approach that employs space-filling curves. We experimentally validate our design methodology by fabricating and characterizing two Luneburg lenses designed to operate at separate frequency bands (26–40 GHz and 70–110 GHz) with antenna gains of 20 and 24 dBi, respectively. The results demonstrate good agreement with rigorous electromagnetic simulations. We also demonstrate the ability to passively beam steer over a wideband of operation (26–40 GHz and 70–110 GHz) with less than 0.5% power loss due to dielectric material losses within the Luneburg lens. [ABSTRACT FROM AUTHOR]

Additive manufacturing features “direct” and “layer-by-layer” fabrication and has significantly facilitated the microstructural design and fabrication of a wide range of highly complex parts. To enable the application of additive manufacturing in major industries and composites, it is necessary to evaluate the microstructural features of additively manufactured parts. Among the various advanced characterization techniques, X-ray micro-computed tomography (μ-CT) showed unique advantages as a high resolution, nondestructive and 3D visualization and measurement technique for material characterization. In the research reported in this article, we have fabricated an array of multi-directional preforms and composites and have characterized their microstructural features via X-ray μ-CT. First, a solid specimen as well as 3D orthogonal and 3D braided preforms have been fabricated using fused filament fabrication (FFF) and inspected with X-ray μ-CT. Then, the fabricated preforms have been infused with silicone matrix and the multi-directional preforms and composites have been tested in compression at different strain levels, to reveal their damage evolution under compressive loading. The preliminary effort made in this research demonstrates the feasibility of characterizing microstructure of additively manufactured parts via X-ray μ-CT technique and enables an investigation of the microstructural features and damage evolution of multi-directional preforms and composites. [ABSTRACT FROM AUTHOR]

We describe the additive manufacturing results pertaining to a multi-function antenna aperture. The antenna consists of customized high dielectric and low loss feedstocks as the enabling technology. The 3D printed prototype shows agreement with simulation while providing excellent performance. [ABSTRACT FROM AUTHOR]