# A Compact Printed Monopole Antenna for WiMAX/WLAN and UWB Applications
## 3 Current Distribution and Parameter Analysis  
Figure 8a-c present the simulation results of the surface current distribution of the antenna at 2.45, 4.95, and 5.80 GHz, respectively. At 2.45 GHz, a strong current distribution was observed at the tip of the triangular radiating patch, the right end of the M structure, and the bottom of the inverted F structure, which mainly affected the low-frequency resonant frequency of the antenna. The surface current distribution at 4.95 GHz revealed a strong current at the bottom of the feeder and at the bottom of the triangle. At 5.80 GHz, the current was distributed over the feeder as well as at several other locations. This figure clearly demonstrates the main influencing factors of the resonant frequency of the corresponding points. We were therefore able to adjust the corresponding frequency depending on the main distribution of the current to change the resonant frequency. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Name** & **Freq** & **Ang** & **Mag** & **Rx** & **VSWR** \\ \hline M1 & 2.45 & \(-\)49.9679 & 0.0862 & 1.1072 \(-\) 0.1473i & 1.1887 \\ M2 & 4.95 & 156.7160 & 0.0344 & 0.9385 + 0.0255i & 1.0712 \\ M3 & 5.80 & 155.2614 & 0.0236 & 0.9578 + 0.0189i & 1.0484 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Smith chart value of the proposed antenna. Figure 6: Input impedance curve of the proposed antenna. Figure 7: Smith chart of simulated antenna matched to 50 \(\Omega\). Figures 9-12 depict the simulated reflection loss effect for different values of L\({}_{6}\), L\({}_{5}\), L\({}_{7}\), and L\({}_{g}\). The effect of the length of one arm of the upper-surface radiating patch on the return loss parameter of the antenna is shown in Figure 9. The length of L\({}_{6}\) had a significant effect on the 4.95-GHz resonant frequency of the antenna. As the size of L\({}_{6}\) increased from 11.6 to 12 mm, a slight offset occurred at all three resonance points and the matching of the antenna deteriorated. Therefore, the optimal solution was achieved when L\({}_{6}\) was 11.8 mm. The results of the analysis of the length of the inverted F structure are presented in Figure 10. The effect of this parameter on the three frequencies was large, and when L\({}_{5}\) increased from 7.3 mm to 7.5 mm, the resonant frequency first increased and then decreased. The match to 5.80 GHz gradually deteriorated, and the matching characteristic of 4.95 GHz was exactly opposite that at 5.80 GHz. Finally, the optimal value of L\({}_{6}\) was 7.4 mm to ensure function in the Bluetooth band of 2.4 GHz. Figure 11 presents the length analysis results for the bottom edge parameters of the triangle. With increasing L\({}_{7}\), the three resonant frequency points all show a slight offset. Therefore, this parameter can be used to fine-tune the resonant frequency of the antenna. The matching effect in the high-frequency and low-frequency bands did not change greatly. The selection of 7 mm for L\({}_{7}\) satisfied the requirements of the antenna better. Figure 12 shows that the width L\({}_{g}\) of the antenna ground plane mainly affected the matching problem of the antenna. It had a great influence on the medium and high frequencies. The low resonant frequency of the antenna also had a substantial effect, and an optimal value for L\({}_{g}\) of 10 mm was selected. Figure 8: Surface current distribution (V/m) of the proposed antenna at (a) 2.45 GHz, (b) 4.95 GHz, and (c) 5.80 GHz.