# Additive Manufactured Waveguide for E-Band Using Ceramic Materials
## 4 Conclusions  
This contribution introduced a novel additive manufacturing approach for waveguide interconnects in mmWave-range. Using ceramic materials as a base body, introducing non-radiating slots in the waveguide sidewalls and applying a customized metallization process  
Figure 11: Measured normalized propagation constant of the fabricated WR12 waveguides compared to a test port adaptor.  
Figure 10: Measured attenuation coefficient \(\alpha\) of the fabricated WR12 waveguides compared to a test port adaptor.  
enables the fabrication of temperature- and chemical-resistant high-frequency devices. The proposed manufacturing process utilizes a standard desktop-grade DLP printer and allows a cost-efficient rapid-prototyping process. To the best of the authors' knowledge, in this work the first ceramic-based slotted waveguide fabricated by AM was shown.  
The ceramic filled resin and the manufactured WR12 waveguide were characterized. In our measurements, the ceramic filled resin showed a shear-thinning behavior which enabled good printability. The printed waveguides were optically characterized by a surface and a scanning electron microscope and featured a surface roughness of \(R_{\text{q,c}}=2.43\) um. In the electrical characterization, an attenuation coefficient of 30-60 dB/m within the E-Band was achieved. This relatively large attenuation coefficient, compared to conventionally manufactured waveguides, is due to the high surface roughness of the ceramic body as well as its geometric inhomogeneities. If these disadvantages are redressed, there is a novel additive manufacturing process for high-frequency applications where polymer-based substrates cannot be used due to thermal limitations.  
Therefore, our future work will go towards using ceramic powders with smaller particle diameter, using professional SLA-printers for ceramics and optimization of the sintering process regarding minimal spatial warping.  
Conceptualization, F.H., K.L. and G.G.; methodology, F.H., T.B. and K.L.; software, T.B., A.H. and K.L.; validation, F.H., T.B., A.H., K.L. and M.S.; formal analysis, F.H., T.B., L.W., K.L. and G.G.; investigation, F.H., T.B. and K.L.; resources, F.H., L.W., N.T., K.L. and M.S.; data curation, F.H., T.B. and K.L.; writing--original draft preparation, F.H., L.W. and K.L.; writing--review and editing, F.H., T.B., L.W., A.H., K.L., M.S., N.T. and G.G.; visualization, F.H.; supervision, F.H. and K.L.; project administration, M.S., K.L. and G.G.; funding acquisition, M.S., K.L. and G.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the EXIST Transfer of Research Program of the German Federal Ministry for Economic Affairs and Energy, grant number 03 EGSFQBY244.  
Not applicable.  
The data presented in this study are available on request from the authors.  
The authors would like to thank Ferro Corporation, Mayfield Heights, Ohio, U.S.A. and Ute Bollert, Department Elektrotechnik-Elektronik-Informationstechnik, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Germany for providing the samples and technical assistance.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} AM & Additive manufacturing \\ CAD & Computer-aided design \\ DLP & Digital light processing \\ FDM & Fused deposition modeling \\ mmWave & Millimeter-wave \\ PCB & Printed circuit board \\ SEM & Scanning electron microscope \\ SLA & Stereolithography \\ SWA & Slotted waveguide array \\ UV & Ultraviolet \\ VNA & Vector network analyzer \\ \end{tabular}