# A Wideband Metal-Only Patch Antenna for CubeSat
## 2 Antenna Configuration and Simulation Results
### Shorting Pins Investigation  
In Figure 8, the effects of shorting pins can be observed based on the surface current distribution on the top radiating F-shaped patch. As can be seen from Figure 8a, the surface current distribution dominates around shorting pin 1 and the top arm of the F-shaped patch as well as shorting pin 2. The current distribution around shorting pin 3 is also more pronounced as compared to the rest of the frequencies (e.g., 1.8 GHz, 2.1 GHz, 2.3 GHz, 2.45 GHz and 2.9 GHz) in Figure 8b-f. This highlights the effect of the three shorting pins on the first resonant frequency of 1.6 GHz. On the other hand, as depicted in Figure 8e,  
Figure 6: Variation of reflection coefficient \(\mid\)S\({}_{11}\)\(\mid\) with respect to the length L\({}_{1}\).  
Figure 7: Variation of reflection coefficient \(\mid\)S\({}_{11}\)\(\mid\) with respect to the length L\({}_{3}\).  
the surface current is highly concentrated around the middle arm of the F-shaped patch and shorting pin 2, while it weakens around shorting pin 1 and 3. This indicates that the middle arm has a greater effect on the second resonance of 2.45 GHz as compared to the shorting pins.  
Figure 9 shows the simulated \(\mid\)S\({}_{11}\mid\) with different diameter values of the shorting pins. The diameter D is varied from 2.64 mm to 5.64 mm, with 1 mm steps in the range. Other parameters are fixed. It can be seen that the pin diameter D has no effect on the resonant frequency and \(-\)10 dB bandwidth of the proposed antenna. However, the reflection coefficient \(\mid\)S\({}_{11}\mid\) improves (decreases) when D is set to 2.64 mm and 3.64 mm as compared to a diameter of 4.64 mm and 5.64 mm. We can also see that the first resonance is shifted from 2 GHz to 1.8 GHz when D is equal to 4.64 mm and 5.64 mm. The optimal diameter of the shorting pins, which provides a small \(\mid\)S\({}_{11}\mid\) at 2.45 GHz and a wideband width, was found to be 3.64 mm. Moreover, the effect of the distance (d\({}_{1}\)) between shorting pin 1 and shorting pin 2 and the distance (d\({}_{2}\)) between shorting pin 1 and shorting pin 3 on \(\mid\)S\({}_{11}\mid\) is shown in Figures 10 and 11, respectively. It is clearly shown that the distance d\({}_{1}\) has a significant effect on the resonant frequency and the matching of the antenna. As the distance d\({}_{1}\) varies from 70.4 mm to 80.4 mm, the proposed antenna achieves a wide -10 dB bandwidth of 1.26 GHz (1.57-2.83 GHz) and a small \(\mid\)S\({}_{11}\mid\) of \(-\)19 dB at a lower frequency (e.g., 1.7 GHz); however, the operating frequency is shifted to 2.58 GHz. In addition, setting d\({}_{1}\) to 70.4 mm leads to an impedance mismatching across the frequency range 1-3.5 GHz. The optimal distance between pins 1 and 2 is when d\({}_{1}\) = 88.4 mm, as it provides a wide \(-\)10 dB bandwidth of 1.08 GHz at the required operating frequency of 2.45 GHz. On the other hand, by varying the distance d\({}_{2}\) from 5.54 mm to 10.54 mm, the operating frequency remains unchanged at 2.45 GHz. The main effect observed when changing d\({}_{2}\) is on the impedance matching, which improves as the shorting pins 1 and 2 are set to 20.54 mm apart. The worst-case impedance matching is observed when d\({}_{2}\) = 5.54 mm, which gives a \(\mid\)S\({}_{11}\mid\) of \(-\)22 dB. The reflection coefficient is improved by setting d\({}_{2}\) = 20.54 mm to a value of \(-\)33 dB.  
Figure 8: Current distribution on the patch at **(a)**\(1.6\) GHz, **(b)**\(1.8\) GHz, **(c)**\(2.1\) GHz, **(d)**\(2.3\) GHz, **(e)**\(2.45\) GHz and **(f)**\(2.7\) GHz.  
Figure 11: Variation of reflection coefficient \(|S_{11}|\) with respect to the shorting pins’ positions (d\({}_{2}\)).  
Figure 10: Variation of reflection coefficient \(|S_{11}|\) with respect to the shorting pins’ positions (d\({}_{1}\)).  
Figure 9: Variation of reflection coefficient \(|S_{11}|\) with respect to the diameter (D) of the shorting pins.