## 3 Research Results  
The resulting design is a microstrip patch antenna array with N = 16 elements distributed in a 4 \(\times\) 4 topology. The current distribution on the antenna array surface in the E-field is presented in Figure 8a. The current flows completely through the FN and reaches each corner of the antennas. Figure 8b depicts a 3D radiation pattern simulation in CST Studio Suite(r) of the array assembled on a CubeSat structure made of plastic. It can be seen that the radiation pattern is in the broadside direction, which ensures that the radiation will not be wasted in unwanted directions and concentrates it in the center of the array. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Parameters** & **L** & **W** & **L1** & **L2** & **L3** & **L4** & **L5** & **L6** \\ \hline Values (mm) & 100 & 100 & 27.5 & 0.8 & 6.0174 & 0.995 & 26.7 & 0.8 \\ Values (\(\lambda\)) & 1.1666 & 1.1666 & 0.3208 & 0.0093 & 0.0702 & 0.0116 & 0.3115 & 0.0093 \\ \hline
**Parameters** & **L7** & **LA** & **LB** & **LC** & **LD** & **W1** & **W2** & **W3** \\ \hline Values (mm) & 2.4 & 2.003 & 11.5 & 16 & 8 & 1.255 & 22.6917 & 0.935 \\ Values (\(\lambda\)) & 0.028 & 0.0233 & 0.1341 & 0.1866 & 0.0933 & 0.0146 & 0.2647 & 0.0109 \\ \hline
**Parameters** & **W4** & **W5** & **W6** & **W7** & **WA** & **WB** & **WC** & \\ \hline Values (mm) & 3.315 & 0.65 & 12.6483 & 2.4 & 7.8371 & 15.674 & 3.3038 & \\ Values (\(\lambda\)) & 0.0386 & 0.0075 & 0.1475 & 0.028 & 0.0914 & 0.1828 & 0.0385 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Array dimensions. Figure 7: Final antenna array design. Finally, the antenna array was manufactured. Figure 9 shows the prototype that was fabricated and tested in the laboratory. The proposed antenna array was tested using a Keysight PNA-L N5230A vector network analyzer and an ETS Lindgren anechoic chamber, as shown in Figure 9d. Subsequently, a comparative analysis of its performance was carried out. Figure 10 presents the performance of the array in terms of the reflection coefficient and the radiation pattern at 3.5 GHz. The reflection coefficient of the simulated array is under \(-10\) dB from 3.505 to 3.528 GHz. Otherwise, the measured reflection coefficient is under \(-10\) dB from  
Figure 8: Antenna array design simulation in CST Studio Suite®: (**a**) current distribution at 3.5 GHz; (**b**) 3D radiation pattern simulation. Figure 9: Antenna array prototype: (**a**) top view, (**b**) bottom view, (**c**) prototype assembled on CubeSat, and (**d**) anechoic chamber measurement environment. 3.46 GHz to 3.54 GHz, as illustrated in Figure 10a. The purpose of our application case is to operate within the 5G low-frequency band for CubeSat from 3.3 to 4.2 GHz. The welding paste and a solid hold between the SMA connector and the feed line were not included in the simulation. This causes a variation between the simulated and measured reflection coefficient due to technical manufacturing details, which is attributed mainly to fabrication tolerances and discontinuities between the feed line and the SMA junction. Nevertheless, it should be noted that the remarkable relevance of this design is its operation in the established 5G frequency in a low profile. Additionally, Figure 10b shows a comparison of the normalized radiation patterns in the main cut of \(\varphi=0^{\circ}\). In this comparison, we include the radiation pattern of the array simulated in CST Studio Suite(r) and the measured pattern. The simulated gain of the array mounted on the CubeSat structure was 10.03 dBi, and the measured gain was 8.03 dBi. Finally, Table 5 lists a comparison of the proposed design with the elements and arrays reported in the literature for CubeSats or the low-frequency band for 5G applications. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Ref. ** & **Design** & **Frequency** & **Bandwidth** & **Size** & **Material** & **Gain** & **Ports** & **Applications** & **CubeSat** \\ \hline \multirow{4}{*}{[30]} & \multirow{4}{*}{Phased array antenna.