## 6 Conclusions  
The device presented in this article exhibits strong performance as a transitional component from planar technology to 3D-printed components. It demonstrates minimal signal losses, typically below 1 dB, even when considering the introduction of microstrip-to-ESIW transitions, which were incorporated solely for the purpose of VNA measurements. The device's ease of fabrication and assembly, coupled with its potential for fostering the development of fully integrated 3D structures and planar circuits, enables the seamless integration of SIC technologies with 3D printed components. Furthermore, its resilience against manufacturing errors and compatibility with a range of readily available, cost-effective 3D printers ensures repeatability. This method can also be applied to waveguide sizes across various frequency ranges. Moreover, the robustness of the soldering process prevents deformation or detachment of the device post-soldering. In the context of future advancements, this prototype serves as a foundational platform for creating more intricate  
Figure 14: Manufacturing characteristics of the 3D part. The estimated cost of copper is USD 16.23.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** & **Figure of Merit** & **Frequency Band** & **Transition** & **Complexity** \\ \hline
[9] & \(T_{1}=250\) μs, \(Q_{i}=11.2\cdot 10^{6}\) dB & 3–17 GHz & Stripline-3D QED & High \\
[29] & \(I_{L}\) (dB) = 0.83 dB, \(R_{L}\)= 21 dB & 26–40 GHz & MS-ESIW & Medium \\
[5] & \(I_{L}\) (dB) = 2 dB, \(R_{L}\)= 8 dB & \(X\) (8–12 GHz) & MPRWG-DiRWG & Very High \\
[10] & \(I_{L}\) (dB) = 0.95 dB, \(R_{L}\)= 15 dB & 33–36.7 GHz & SIW-Rectangular Waveguide & Very High \\ This work & \(I_{L}\) (dB) = 0.6 dB, \(R_{L}\)= 15 dB & \(K_{u}\) (12–18 GHz) & ESIW-3D & Low \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison performance with other transitions.  
devices and geometries previously considered unattainable using SIC manufacturing techniques. This will enable smaller-scale laboratories to manufacture these devices without the need to invest in expensive fabrication equipment or similarly costly high-performance devices. Examples of such prototypes encompass high-quality filters, dividers, couplers, and horn antennas, to name a few. While the current device boasts robustness, it remains a compelling avenue for future research to subject the device to thermal and mechanical stress conditions to further its characterisation, as well as some other improvements that are going to be considered once this prototype has been validated.  
Conceptualization, D.H., A.B., M.F., S.C., H.E. and V.E.B.; methodology, D.H. and A.B.; software, D.H. and A.B.; validation, D.H.; formal analysis, D.H.; investigation, D.H.; resources, D.H. and A.B.; data curation, D.H. and S.C.; writing--original draft preparation, D.H. and M.F.; writing--review and editing, D.H., A.B., M.F., S.C., H.E. and V.E.B.; supervision, A.B., M.F., H.E.; project administration, A.B. and V.E.B.; funding acquisition, A.B. and V.E.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Ministerio de Ciencia e Innovacion, Spanish Government, and the European Union NextGenerationEU/PRTR, through the Subprojects C44 and C41 of the Coordinated Project TED2021-129196B, under Grant MCIN/AEI/10.13039/501100011033. This work has been financed by European Social Fund + (ESF+).  
Data sharing not applicable.  
The authors declare no conflict of interest.