# Ultra-Wideband Bandpass Filters Using Tapered Resonators
## 6 Conclusions  
In this paper, new UWB microwave bandpass filters based on exponential and linear short-circuited tapered transmission line stub resonators are analyzed and modeled. The proposed filters are then designed, simulated and fabricated to demonstrate the analytical circuit model of the tapered resonators. Significant improvements in the proposed UWB filters have been reported in the bandwidth, performance, and size reduction due to the proper integration of the tapered transmission line stubs. The operational bandwidth of the UWB filters can be pre-controlled by the tapered ratio of the filter resonators as demonstrated by the simulated and measured results. The analytically determined, simulated, and measured responses of the designed exponential and linear tapered resonator filters are in good agreement. Additionally, the fractional bandwidth of the realized UWB bandpass filter is 112.22%. The performance measures of the proposed UWB filters are summarized and compared with similar structures in Table 4.  
Conceptualization, F.R. and M.A.S.A.; methodology, F.R. and M.A.S.A.; software, F.R.; validation, F.R.; formal analysis, M.A.S.A., F.R. and S.M.S.; investigation, F.R. and S.M.S.; resources, F.R. and. M.A.S.A.; data curation, F.R.; writing--original draft preparation, F.R.; writing--review and editing, F.R., M.A.S.A. and S.M.S.; visualization, F.R. and S.M.S.S.; supervision, M.A.S.A.; project administration, F.R.; funding acquisition, F.R. All authors have read and agreed to the published version of the manuscript.  
The authors extend their appreciation to the Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia for funding this research work through the project number IF-PSAU-2021- 01/18746.  
Not applicable.  
The data that support the findings of this study are available upon reasonable request from the corresponding author.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Reference**}} & \multicolumn{1}{c}{**Passband**} & \multicolumn{1}{c}{**Bandwidth**} & \multicolumn{1}{c}{**Insertion Loss**} & \multicolumn{1}{c}{**Return Loss**} & \multicolumn{1}{c}{**Techniques**} \\  & **(GHz)** & **(GHz)** & **(dB)** & **(dB)** & **(dB)** & **Techniques** \\ \hline
[3] & 2.92–10.95 & 8.03 (107.0\%) & \(-\)0.49 & \(-\)12.0 & ICPCL \\ \hline
[15] & 3.06–10.0 & 6.94 (106.3\%) & \(-\)1.00 & \(-\)13.0 &
\begin{tabular}{c} Cascaded bandpass \\ and bandstop \\ filters \\ \end{tabular} \\ \hline
[23] & 3.05–10.62 & 7.57 (100.9\%) & \(-\)1.50 & \(-\)13.0 & MMR \\ \hline
[24] & 3.1–10.6 & 7.5 (110.0\%) & No data & \(-\)11.0 &
\begin{tabular}{c} Short-circuited \\ stubs \\ \end{tabular} \\ \hline
[25] & 2.50–7.00 & 4.5 (60.0\%) & No Data & \(-\)23.0 & CLR \\ \hline
[26] & 3.00–10.2 & 7.20 (96.0\%) & \(-\)2.00 & \(-\)14.9 & Lumped capacitors \\ \hline
[27] & 3.20–11.70 & 8.50 (114.0\%) & \(-\)1.50 & \(-\)12.0 & MMR \\ \hline
[28] & 3.12–10.69 & 7.57 (109.6\%) & \(-\)1.20 & \(-\)12.7 & MMR \\ \hline
[29] & 2.95–10.75 & 7.80 (113.9\%) & \(-\)0.60 & \(-\)14.0 & SIDGS \\ \hline
[30] & 3.21–10.77 & 7.56 (109.4\%) & \(-\)0.80 & No Data & MMR \\ \hline \multirow{3}{*}{This work} & \(k/\beta_{0}=0.250\) & 3.24–10.88 & 7.64 (108.22\%) & \(-\)1.25 & \(-\)17.5 & \multirow{3}{*}{
\begin{tabular}{c} Short-circuited \\ tapered resonators \\ \end{tabular} } \\  & \(k/\beta_{0}=0.375\) & 3.11–10.95 & 7.84 (111.52\%) & \(-\)1.00 & \(-\)17.3 & \\ \cline{1-1}  & \(k/\beta_{0}=0.500\) & 3.09–10.99 & 7.90 (112.22\%) & \(-\)0.80 & \(-\)17.0 & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Performance comparison with other UWB filter techniques.