## 6 Conclusions  
Two technologies for IoT devices have been compared: antenna booster technology and FPC antennas. The off-PCB FPC antenna presents similar efficiency to the antenna booster. However, off-PCB is not the typical situation but on-PCB. In this scenario, the performance drastically deteriorates when placing the FPC antenna in the device.  
The FPC antenna has been evaluated at several heights above the ground plane of a PCB from 2.4 mm up to 20 mm presenting in all cases worse efficiency values than the embedded booster antenna at both frequency regions 698-960 MHz and 1710-2690 MHz. When comparing the FPC antenna over the ground plane of the PCB at the same height (2.4 mm) as the antenna booster, total efficiency is 15.5 dB, 11.4 dB, and 18.1 dB more for the antenna booster at the low-frequency region for the small, medium, and large PCB, respectively. For the high-frequency region, the total efficiency is 4.8 dB, 6.2 dB, and 7.8 dB more for the antenna booster for the small, medium, and large PCB, respectively.  
The FPC antenna also presents dependent behaviour on its position on the PCB, where total efficiency can change 10 dB. This situation is irrelevant for the embedded antenna booster since the position is fixed on the PCB and automatically mounted following a pick and place assembly process due to its SMD nature.  
Based on these results, FPC antennas, like the one presented in this paper, are large, and when placed above the ground plane of the device, the efficiency drastically drops. A further negative impact on the overall FPC performance can be expected when batteries are placed in the device since they are covered with a conductive material and thus decrease the distance between the FPC and the conductive part of the battery. However, this falls outside the scope of this study. Additionally, the performance is unpredictable since it depends on the ability of the human being to mount the antenna on the PCB of the device. On the contrary, embedded antenna boosters are convenient for designing IoT devices due to their small size, multiband behaviour, off-the-shelf nature, cost competitiveness, and compatibility with the pick and place assembly process, ensuring stability when mass-producing devices with embedded antennas.  
In summary, when leaving the antenna selection for IoT devices to the end of the design cycle, by just putting a UFL connector on the PCB in the initial design stages, the  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Potential Bandwidth (\%, SWR = 3)** & **900 MHz** & **2200 MHz** \\ \hline Off-PCB & 30.5\% & 50.3\% \\ On-PCB & 1.2\% & 1.3\% \\ \hline \hline \end{tabular}
\end{table}
Table 8: Potential bandwidth for the FPC antenna for off-PCB and on-PCB.  
risks of not being able to get acceptable performance increase materially, and the design effort of selecting and tuning an antenna booster are easily recovered given the price difference and manufacturing cost savings.  
Conceptualization, J.A., C.P. and A.A.; Data curation, A.F.; Writing--original draft, J.A.; Writing--review & editing, J.A. and J.G. All authors contributed to the conception and development of the results. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors declare no conflict of interest.