## 5 Conclusions  
This paper proposes an ultra-wideband CM noise suppression filter using a magnified coupled DGS. We appropriately designed the resonant frequency using an asynchronously tuned coupled resonant circuit. In the frequency domain, the measurements demonstrated that the \(\mathrm{S_{dd21}}\) from DC to 12.35 GHz was measured within the \(-3\) dB definition and that  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & [17] & [18] & [19] & [20] & **This Work** \\ \hline Physical size & \multirow{2}{*}{\(10\times 10\)} & \multirow{2}{*}{—} & \multirow{2}{*}{9.2 \(\times 19\)} & \multirow{2}{*}{\(7\times 7\)} & \multirow{2}{*}{\(5.04\times 5.2\)} \\ (mm \(\times\) mm) & & & & \\ Electrical size & \multirow{2}{*}{—} & \multirow{2}{*}{0.22 \(\times\) 0.46} & \multirow{2}{*}{0.305 \(\times\) 0.305} & \multirow{2}{*}{0.292 \(\times\) 0.301} \\ (\(\lambda_{g}\times\lambda_{g}\)) & & & & \\ Area & \multirow{2}{*}{—} & \multirow{2}{*}{\(174.8\) mm\({}^{2}\)/} & \multirow{2}{*}{49 mm\({}^{2}\)/} & \multirow{2}{*}{26.21 mm\({}^{2}\)/} \\ \(\mathrm{S_{cc21}}\) \(\mathrm{<-10\) dB} & & & & \\ (GHz) & \multirow{2}{*}{3–13} & \multirow{2}{*}{2.4–3.15} & \multirow{2}{*}{1.9–7.3} & \multirow{2}{*}{3.7–10.8} & \multirow{2}{*}{2.9–16.2} \\ FBW & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 6: Detailed comparison with related DGSs.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & [20] & **This Work** \\ \hline Reference Board & \(170\) mV & \(138\) mV \\ \hline Filter Board & \(98.6\) mV & \(52\) mV \\ \hline Suppression Ratio & \(42\%\) & \(62.3\%\) \\ \hline \hline \end{tabular}
\end{table}
Table 7: Comparison of the noise magnitude.  
the CM noise could be reduced by more than \(-10\) dB from 2.9 to 16.2 GHz. In addition, the FBW of the stopband reached 139.3%. In the time domain, the measurement of the CM noise magnitude was reduced by 62.3%.  
Although most high-speed interfaces use stripline routing, we could still place the proposed filter near the connector. The proposed filter is characterized by having two simple geometry structures, no additional components, the most compact size on the PCB, and a considerable FBW. As far as we know, this is the first filter to achieve CM noise suppression exceeding 130% FBW in ultra-wideband. Finally, the proposed filter can be widely implemented to reduce the electromagnetic interference in RF and wireless communication applications with Wi-Fi 5 and 6E. In addition, it can be used in satellite and microwave telecommunication applications with the C and X bands, as part of the Ku band.  
Conceptualization, D.-B.L.; methodology, M.-H.W.; software, M.-H.W.; validation, T.A.; formal analysis, A.A.P.; investigation, T.A.; resources, D.-B.L.; data curation, A.A.P.; writing--original draft preparation, M.-H.W.; writing--review and editing, D.-B.L., T.A. and A.A.P.; visualization, M.-H.W.; supervision, D.-B.L.; project administration, D.-B.L.; funding acquisition, D.-B.L. All authors have read and agreed to the published version of the manuscript.  
Not applicable.  
No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
The authors would like to thank [PERSON], Department of Electronic Engineering, National Taipei University of Technology, Taiwan, R.O.C., for providing the idea of defected ground structure in this research.  
The authors declare no conflict of interest.