# Super-Wideband Monopole Printed Antenna with Half-Elliptical-Shaped Patch
## 3 Results and Discussion  
### S-Parameters  
The proposed SWB monopole antenna is analyzed in terms of the reflection coefficient (S\({}_{11}\)), as shown in Figures 2 and 3.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **Dimension** & **Parameters** & **Dimension** \\ \hline Ws & 200 & R2 & 20 \\ Ls & 220 & R3 & 15 \\ Wf & 4.8 & W1 & 3 \\ Lf & 50 & L1 & 35 \\ D & 177 & Lg & 49 \\ R1 & 140 & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Dimensions of proposed SWB antenna in mm.  
Figure 3: Simulated reflection coefficient of various L1 values.  
Figure 2: Simulated reflection coefficient of Steps 1–4.  
Figure 2 demonstrates the reflection coefficient (S\({}_{11}\)) of the proposed SWB antenna for all steps. In Step 1, a patch with values of R1 = 100 mm and R2 = 60 mm and with a rectangular defected ground plane of Lg = 49 mm was used; the circle-like patch caused many ripples throughout the span of the frequency, which caused the S\({}_{11}\) value to be higher than \(-10\) dB. Step 2 involved bending the edge of the defected ground plane with a radius R3 = 15 mm; this bending technique reduced the rippling throughout the span of the frequency, and both Step 1 and Step 2 had the same lowest \(-10\) dB frequency shift at 0.56 GHz. Step 3 involved changing the patch from a circle-like shape to an elliptical-shaped patch and increasing the R1 value (R1 = 140 mm) and reducing the R2 value (R2 = 20 mm); this elliptical configuration achieved the same S\({}_{11}\) ripple as in Step 2, but the lowest \(-10\) dB frequency shift from 0.56 GHz to 0.54 GHz. Steps 1, 2, and 3 all have the same issue, which is that in the frequency range from 1 to 1.5 GHz, there are frequencies that have an S\({}_{11}\) value higher than \(-10\) dB, which caused the antenna to have a low bandwidth and bandwidth ratio. This issue can be solved by introducing a triangle inset on the defected ground plane (Step 4), which shifts the lowest \(-10\) dB frequency back to 0.5 GHz, and achieving a super-wideband characteristic from 0.5 GHz to over 40 GHz with a bandwidth of over 39.5 GHz and a bandwidth ratio of over 80.  
Figure 3 demonstrates the reflection coefficient of the proposed SWB antenna with a variation in the ground triangular inset length (L1). At L1 = 5 mm, this exhibits a working frequency of 0.536-1.03 GHz and 1.18-40 GHz where there are frequencies above \(-10\) dB in the range of 1.03-1.18 GHz, which causes a small bandwidth ratio value. At L1 = 15 mm, this enhances the S\({}_{11}\) performance at the range of 1.03-1.18 GHz, which now means the antenna has a working frequency from 0.53 to 40 GHz. At L1 = 15 mm, this shifts the lower frequency from 0.53 GHz to 0.525 GHz. This shift in the lower working frequencies is caused by the increment of L1, wherein at L1 = 35 mm, the lowest working frequency of the proposed antenna is 0.5 GHz. Table 2 summarizes the electrical characteristics for the various L1 values including the bandwidth and bandwidth ratio, which are computed using Equations (5) and (6).  
\[Bandwidth=f_{H}-f_{L} \tag{5}\]  
\[Bandwidth\ Ratio=\frac{f_{H}}{f_{L}} \tag{6}\]  
where \(f_{H}\) is the highest working frequency, which is 40 GHz, and \(f_{L}\) is the lowest working frequency of the proposed antenna.