## 7 Conclusions  
This article presents a low-profile broadband antenna covering the Ka-band for millimeter-wave IoT applications. Its circular ring-shaped structure with equilateral triangles provides a path for surface current to complete its loop with the differential phase, thereby generating circular polarization. The CMA analysis showed how the summation  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Ref.** & **Dim. in \(\boldsymbol{\lambda}\)** & \begin{tabular}{c} **Dim. in** \\ **mm2** \\ \end{tabular} & **Ant Type** & \begin{tabular}{c} **Res. in** \\ **GHz** \\ \end{tabular} & \
\begin{tabular}{c} **BW in** \\ **GHz** \\ \end{tabular} &
\begin{tabular}{c} **AR in** \\ **GHz** \\ \end{tabular} & **Gain** & **Pol.** & **LM** \\ \hline
[13] & 0.62 \(\times\) 0.45 & 6.8 \(\times\) 5 & Parasitic patch & 27 & 21–28.5 & – & 4 & LP & No \\ \hline
[14] & \(1.1\times 1.1\) & \(12\times 12\) &
\begin{tabular}{c} Patch + \\ Metasurface \\ \end{tabular} & 27 & 24.25–29.5 & 25.9–28.2 & 7 & RHCP/LHCP & No \\ \hline
[28] & 1.03 \(\times\) 1.03 & \(11\times 11\) & Metasurface & 28 & 26.2–30.8 & – & 6.5–10.1 & LP & No \\ \hline
[29] & 0.65 \(\times\) 0.7 & 3.25 \(\times\) 3.5 & Patch & 60 & 55–64 & – & 4 & LP & No \\ \hline
[30] & 0.8 \(\times\) 0.8 & 4 \(\times\) 4 & Patch & 60 & 58–90 & – & 5–6.7 & LP & No \\ \hline
[31] & 0.47 \(\times\) 0.28 & 5 \(\times\) 3 & Patch & 28 & 26–30 & – & 3.7–4.7 & LP & No \\ \hline
[32] & 1.12 \(\times\) 1.12 & 12 \(\times\) 12 & Monopole & 28 & 26–29 & – & 4.8 & LP & No \\ \hline
[33] & 2.1 \(\times\) 1.4 & 22.5 \(\times\) 15 & Patch dipole & 28 & 25.6–29.5 & – & 1 & LP & No \\ \hline
[34] & 2.33 \(\times\) 2.33 & 25 \(\times\) 25 & Period stub-loaded & 28 & 27.5–32.5 & 25.3–32.7 & NA & CP & No \\ \hline Prop. & 0.56 \(\times\) 0.56 & 6 \(\times\) 6 & Patch & 28 & 23–42 & 36–40.2 & 4–6.2 & RHCP/LHCP & Yes \\ \hline \hline \end{tabular} Note: Dim.—dimensions, Ant—antenna, Res.—resonance, BW—bandwidth, AR—axial ratio, LM—link margin.  
\end{table}
Table 1: Performance comparison with other designs.  
Figure 17: Link margin estimation of the proposed antenna for IoT indoor scenarios for **(a)** Case I and (b) Case II.  
of orthogonal modes leads to CP. The antenna was verified for IoT application in indoor scenarios, and the results showed a satisfactory link margin of 10 dB to a distance of 75 m with a data rate of 10 Gbps. Further, the gain of the antenna can be enhanced with array techniques. Also, its data rate can be improved with MIMO antennas. Therefore, the proposed antenna is suitable for mmWave applications.  
Conceptualization, P.S.B.G., T.A. and J.A.; methodology, P.S.B.G., T.A. and J.A.; software, P.S.B.G. and G.S.G.D.; validation, P.R.M., T.A., S.P.G., S.P. and J.A.; formal analysis, P.S.B.G., S.P. and J.A.; writing--original draft, P.S.B.G.; writing--review and editing, P.S.B.G., P.R.M., T.A., G.S.G.D., S.P.G., S.P. and J.A.; visualization, P.S.B.G., P.R.M., T.A., G.S.G.D., S.P.G., and J.A.; supervision, T.A. and J.A. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
Author [PERSON] was employed by the company Ignion, Barcelona, Spain. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.