## 3 Coplanar Dipole Production Technology
### Technical Analysis of a 3D LDM-Printed Patch Antenna  
The surface topography was measured with a Talysurf CLI profilometer using the touch method and evaluated with the TalyMap Platinum software (version 6.2). Pictures of the surface were taken on a Tescan Mira 4 electron microscope. Figure 9 shows an analysis of the 3D LDM-printed surface. Figure 10 shows the surface morphology at different magnifications. Figure 10a shows small cracks reaching 100 um in length. Figure 10b shows a detail of the crack; we were not able to measure the depth of the crack, but we predicted that it did not extend through the entire thickness of the coating. Figure 10c shows in detail the shape of the traces left by the nozzle after printing. Figure 10d shows the  
Figure 8: Image of coplanar dipole fabricated on (**a**) FR4 material; (**b**) Arlon 25N; (**c**) 3D substrate.  
microstructure of the surface, showing that the surface is not homogeneous, as some local imperfections occur. From the results presented below, it is evident that these imperfections on the surface did not affect the function of the antenna. Figure 11 shows a detail of the printed dielectric substrate.  
Figure 10: Coplanar dipole imaging with the Olympus MVX10 microscope; (**a**) are small cracks, (**b**) is a detail of the crack, (**c**) is in detail the shape of the traces left by the nozzle after printing, (**d**) is the micro-structure of the surface.  
Figure 9: Imaging the location of a detailed analysis of a coplanar dipole using a 3D substrate.  
Another test was to determine the roughness and roughness slope of the printed metal layer. A touch sensor was used for the test. The test was carried out according to the ISO 25 178-1 standard at a length of 4 mm and cut-off of 0.8 mm, and a Gaussian filter was used for evaluation [22]. Figure 12 shows the roughness profile of the conductive material. The main test parameters are the following:  
* Roughness average \(Ra=1.15\)\(\upmu\)m;
* Mean roughness depth \(Rz=6.78\)\(\upmu\)m;
* Total height of the roughness profile \(Rt=7.86\)\(\upmu\)m;
* Arithmetic mean slope \(Rda=7.62^{\circ}\);
* Root mean square slope of the assessed profile \(Rdq=14.6^{\circ}\).  
Thanks to a detailed technical analysis of the 3D-printed patch antenna, it was found that 3D LDM printing technology has very high-quality parameters and is suitable for the production of the proposed patch antenna.  
During handling of the 3D-printed antenna, it was discovered that this antenna is very fragile. Figure 13 shows the damaged antenna after a 1 m fall to the ground. This fragile feature could be eliminated, for example, by placing the antenna into a protective housing. Future research will explore the options for strengthening this type of antenna. However, the main purpose of this 3D method is to manufacture prototypes of geometrically complex antennas, where high demands are placed on precision manufacturing. One major advantage of this 3D method is that the cost of production does not increase with the complexity of the antenna structure.  
Further research can focus on a better adaptation of the design rules using LDM technology to fully exploit the options of 3D space and to explore other options of antenna design [18], to improve the solder pad arrangement and the connectors, and to make the soldering method more suitable to this technology.  
Figure 11: Dielectric imaging with the Olympus MVX10 microscope (400\(\times\) magnified).  
Figure 12: Display of the roughness of the conductive material.