# Super-Wideband Monopole Printed Antenna with Half-Elliptical-Shaped Patch
## 3 Results and Discussion
### Measurement Results  
The proposed antenna (Figure 7) was connected by a 2.92 mm connector and measured using a Rohde & Schwarz ZNB40 vector network analyzer (VNA) (Munich, Germany) operating at frequencies up to 40 GHz. Figure 8 illustrates a comparison between the simulated and measured results.  
Figure 8: Comparison of S\({}_{11}\) results of simulation and measurements.  
Figure 6: Simulated realized gain and radiation efficiency of the proposed antenna.  
Figure 7: Fabricated antenna, front (**a**) and back (**b**).  
The simulated and measured results exhibit a discrepancy. The S\({}_{11}\) parameter (reflection coefficient) starts to increase at 10 GHz, resulting in a limited \(-10\) dB bandwidth only up to 22.5 GHz. To address the discrepancy between the simulated and measured results, the 2.92 mm connector (Figure 9) was accounted for in the simulation model to analyze its impact on the S\({}_{11}\) parameter compared to a waveguide port.  
Adding the 2.92 mm connector model to the simulation clearly shows a change in the results when compared to the simulation without it (Figure 10). The simulated \(-10\) dB bandwidth with the connector only reaches 23.5 GHz, while by using waveguide port, the \(-10\) dB bandwidth can reach up to 40 GHz. Figure 11 shows a comparison of the measurements with the simulation model that includes the 2.92 mm connector. The results agree very well up to 23.5 GHz, with a bandwidth ratio of 47. Beyond this point, the simulation shows a significant increase in the reflection coefficient, followed by another decrease at around 38 GHz.  
Figure 10: Comparison of simulated S\({}_{11}\) with and without connector model.  
Figure 9: The 2.92 mm connector is included in the simulation model (**a**) instead of the waveguide port (**b**).  
A significant difference exists in the simulation results obtained with and without the connector model, despite both simulations yielding the same characteristic impedance (Zo) of 50 \(\Omega\). To investigate the source of the differences, the surface current is analyzed across a range of frequencies.  
Anomalous surface current distributions are observed at frequencies above 23 GHz. At this frequency, in simulations without connector model, the direction of the surface current appears to propagate back towards the port rather than radiating outwards towards the antenna (Figure 11), as is the case for frequencies between 0.5 GHz and 23 GHz. Figure 11a-d shows the surface current at 29 GHz, when the phase are 90\({}^{\circ}\), 135\({}^{\circ}\), 180\({}^{\circ}\), and 235\({}^{\circ}\), respectively.  
However, when the connector model is included, the simulations show a bidirectional surface current flow in the transmission line. While some energy propagates from the antenna towards the port, additional energy also propagates from the connector towards the antenna. This phenomenon highlights the distinct energy flow difference between the two models (Figure 12). As illustrated in Figure 1, the surface current direction appears to be opposite to each other. The differences in the S\({}_{11}\) results between the simulations with and without a connector model at frequencies exceeding 23 GHz are likely attributed to the significantly altered energy flow patterns observed in this regime.  
Figure 11: Surface current at 29 GHz in different phases: (**a**) 90\({}^{\circ}\); (**b**) 135\({}^{\circ}\); (**c**) 180\({}^{\circ}\); (**d**) 235\({}^{\circ}\).