# Analysis of 3D Printed Dielectric Resonator Antenna Arrays for Millimeter-Wave 5G Applications
## 4 Discussion and Conclusions  
A comparison of different techniques for manufacturing DRAs was conducted, as shown in Table 1. Compared with conventional methods using dielectric ceramics and other additive manufacturing (AM) techniques, the applied FDM 3D printing technique emerges as a promising option. It offers a range of flexible material choices with variable electrical properties, making it highly adaptable to diverse applications. This approach presents several key advantages, including low cost, high resolution, rapid prototyping capabilities, and straightforward processing. These benefits enhance its viability for fabricating DRAs across different frequency bands, from microwave to mmWave. Additionally, as shown in Table 1, FDM does not provide the same high resolution as SLA. However, despite this, FDM's cost-effectiveness, material versatility, scalability, and ease of use make it an indispensable technology in the field of additive manufacturing. For applications where speed, practicality, and affordability are crucial, FDM is often the preferred choice, solidifying its continued importance in both research and industrial applications. Several DRA samples, including both cylindrical and cuboid geometries, were fabricated using FDM for operation at microwave and mmWave frequencies. The measured results and surface profiles confirm the feasibility of the FDM technique in manufacturing DRAs for modern 5G mmWave and beyond communication systems. Cylindrical DRAs, with their smoother surfaces and more consistent shape, exhibited fewer precision errors compared to cuboid DRAs, which showed challenges in achieving sharp edges and corners due to the inherent limitations of the FDM process. These challenges, while not critical at microwave frequencies, become more pronounced at higher mmWave frequencies, where small dimensional inaccuracies can significantly impact performance. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** & [3,4] & [33] & [34] & [35] & **This Work** \\ \hline \multirow{2}{*}{**Technique/Material**} & \multirow{2}{*}{Dielectric ceramic} & FDM/ & \multirow{2}{*}{
\begin{tabular}{c} FDM/ \\ PLA, polyamide, \\ SLA/ resin \\ \end{tabular} } & FDM/3D printing & Micro-SLA/ & FDM/ \\  & & & \multicolumn{1}{c}{filament} & photopolymer resin & 3D printing filament \\ \hline
**Working Frequency** & Variable & 3.5 GHz & 1.575 GHz & 3.5 GHz & 13 GHz, 26 GHz \\ \hline
**Permittivity** & \textgreater{}20 & 6.41 & 15 & 2.7 & 10 \\ \hline
**Flexible\textgreater{},7** & \multirow{2}{*}{No} & \multirow{2}{*}{No} & \multirow{2}{*}{Not given} & \multirow{2}{*}{No} & Yes \\ \(\varepsilon_{r}\)**Range** & & & & & 2–12 \\ \hline
**Resolution** & N.A. & 0.2 mm & 0.15 mm & 25 \(\upmu\)m & 0.2 mm \\ \hline
**Surface Roughness** & N.A. & 100 \(\upmu\)m & N.A. & 200 \(\upmu\)m & \textless{}150 \(\upmu\)m \\ \hline
**Rapid Prototyping** & No & Yes & Yes & Yes \\ \hline
**Fabrication Steps** & Multiple & Single & Single & Single & Single \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison with other techniques in producing DRAs. Figure 23: Side view of the FDM 3D-printed cuboid DRA element (**a**) before, and (**b**) after refining. It is important to note that the precision of the printed DRAs, including dimensional tolerances and surface smoothness, becomes a critical factor when operating at higher mmWave frequencies. These slight deviations in geometry may restrict the application of FDM-printed DRAs in the upper mmWave bands. To address this, feedback from the fabrication process can be integrated into simulations, enabling a more consistent design and development process. By iterating between simulation and fabrication, it is possible to optimize the DRA design for specific applications, ensuring that the printed DRAs meet the necessary performance requirements despite the limitations of the 3D printing technique. As the goal of this work was to assess the direct printing of the DRA for potential immediate use, no post-processing was applied.