## 4 Discussion  
Due to silicon's higher conductivity, this may adversely affect the radiation performance of the antenna, especially in typical six-metal-layer CMOS processes. Such process structures can lead to a decrease in antenna efficiency due to the coupling effects between the antenna and the silicon substrate, as well as the conductivity of the substrate, causing energy losses. In this work, a wideband Vivaldi antenna suitable for the 100 GHz frequency band is proposed. Vivaldi antennas are renowned for their superior wideband characteristics, high efficiency, and travelling wave properties with stable radiation patterns, making them highly suitable for high-frequency applications. The Vivaldi antenna in this paper employs an array structure that not only enhances the antenna's directivity of the antenna but  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**References** & **Antenna Type** & \({}^{\star}\)**FBW (GHz)** & **Size (mm\({}^{2}\))** & **Process** \\ \hline \multirow{3}{*}{[5]} & Monolithically Integrated antennas & 77–87 & \multirow{3}{*}{\(1.296\times 1.508\)} & 0.13 \(\mathrm{\SIUnitSymbolMicro m}\) SiGe \\  & & & & BiCMOS \\ \hline \multirow{3}{*}{[6]} & \multirow{3}{*}{(SNIR) antenna} & \multirow{3}{*}{\(57.24\)–\(65.88\)} & \multirow{3}{*}{\(\mathrm{N}/\mathrm{A}\)} & Switching the directive beams of the arrays \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \hline \multirow{3}{*}{[17]} & Trough-polymer Via technology & \multirow{3}{*}{\(120\)–\(124.3\)} & \multirow{3}{*}{\(0.94\times 1.45\)} & SiGe BiCMOS \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \hline \multirow{3}{*}{[19]} & Yagi antenna & \multirow{3}{*}{\(57.6\)–\(67\)} & \multirow{3}{*}{\(0.74\times 1.14\)} & Glass substrate \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \hline \hline \end{tabular} \({}^{\star}\)FBW = fractional bandwidth.  
\end{table}
Table 2: Comparison with Other Antennas.  
Figure 21: Measurement setup.  
also extends the scanning angles and bandwidth through the array design. The proposed CMOS Vivaldi antenna achieves a wide bandwidth of 16.93 GHz within the frequency range of 85.47-102.40 GHz, accounting for 17.7% of the entire band. The overall volume of the antenna is tightly controlled within a compact space of 1.2 \(\times\) 1.2 mm. With a peak gain of \(-\)4 dBi, this represents a significant achievement considering the antenna's size, especially given its operation in the high-frequency millimetre-wave band. This antenna finds wide-ranging applications in wireless communications, particularly in future 5G/6G high-frequency communications, satellite communication, long-range radar sensing, and other millimetre-wave applications.  
Conceptualization, M.-A.C.; methodology, M.-A.C.; software, M.-A.C.; validation, M.-A.C., C.-W.T. and K.-C.T.; formal analysis, M.-A.C.; investigation, M.-A.C.; resources, M.-A.C.; data curation, M.-A.C.; writing--original draft preparation, M.-A.C.; writing--review and editing, M.-A.C. and C.-W.T.; visualization, M.-A.C.; supervision, M.-A.C.; project administration, M.-A.C.; funding acquisition, M.-A.C. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Data Availability StatementData is contained within the article. The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding authors.  
The authors declare no conflicts of interest.