## 5 Conclusions  
A high-gain, circularly polarized X-band microstrip patch antenna designed for CubeSat applications is presented in this paper. The gain enhancement is achieved by applying a 16-element ring of electromagnetic band-gap structures surrounding the center radiator. The right-hand circular polarization is formed by etching two square slots symmetrically along the right diagonal line of the center radiator. The antenna is simulated and tested together with 3U CubeSat Platforms to evaluate the potential interference of the satellite platform with the antenna performance. The measured input reflection coefficient, far-field antenna pattern, axial ratio and 3 dB axial ratio bandwidth agreed well with the simulation results. The antenna gain is around 11.72 dBi and the spatial axial ratio is about 1.4 dB at the target frequency of 8.483 GHz, and the 3 dB ARBW is approximately 250 MHz. All these measured results satisfied our minimum antenna design requirements. With this EBG MPA design, we can boost the antenna gain more than two times (3.5 dB) without improving the total height of the antenna structure, and use only one layer of an EBG, thus maintaining the advantage of the low profile of the microstrip patch antenna. Furthermore, the measurements showed that the effect of the satellite structure model to the antenna radiation efficiency is negligible. The low profile and simple design of this antenna make it suitable for current CubeSat platforms. Our future work will focus on increasing the gain more by further studying different EBG and metamaterial topologies, while keeping the simplicity and robustness of the antenna structure.  
Conceptualization, L.P.T. and D.N.; methodology, L.P.T.; software, L.P.T. and M.H.; validation, L.P.T. and D.N.; data curation, L.P.T.; writing--original draft presentation, L.P.T.; writing--reviewing and editing, D.N. and M.H.; visualization, L.P.T.; supervision, D.N.; project administration, D.N.; funding acquisition, D.N. All authors have read and agreed to the published version of the manuscript.  
This work was supported in part by the Foundation for Advancement of Industry Science and Technology (FAIS) Research and Development Grant and JSPS KAKENHI Grant Number 24K17455.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref. No.** & **Center Freq.** & **Antenna Size** & **Max. Gain** & **Polarization** & **Remarks** \\ \hline
[11] & 7 & 60 \(\times\) 45 & \
\begin{tabular}{c} 11.78 \\ (directivity) \\ \end{tabular} & LP &
\begin{tabular}{c} - Only simulation result of the directivity, not the realized gain. \\ - The height is not mentioned. However, the 2 EBG superstrates makes the structure too \\ high to apply to CubeSats that follow Cal \\ Poly’s CDS. \\ \end{tabular} \\ \hline
[12] & 9.9 & 60 \(\times\) 60 \(\times\) 3.2 & 9.77 & LP &
\begin{tabular}{c} - Complicated design with mushroom-like \\ EBG as the middle layer. \\ - The airgap between layers can significantly affect the antenna performance. \\ \end{tabular} \\ \hline
[21] & 10.67 & 50 \(\times\) 35 & 7.7 & LP & \
\begin{tabular}{c} - The gain is not so high. \\ - No measured results. Only simulation. \\ - The height is not mentioned. \\ \end{tabular} \\ \hline Our work & 8.48 & 91.3 \(\times\) 91.3 \(\times\) 1.6 & 11.72 & CP &
\begin{tabular}{c} - Simple design. \\ - No feed network needed. \\ - Highly compatible with CubeSat platforms. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 4: _Cont._