## Abbreviations  
The following abbreviations are used in this manuscript:  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Ref.** & **Feed Structure** & **Antenna Type** & **Gain (dBi)** & **Size (mm)** & **Polarization** & **10 dB BW (\%)** \\ \hline
[8] & Coaxial line & Vertical slot & 11.8 & 94.6 \(\times\) 94.6 \(\times\) 61.9 & CP & 15 \\
[14] & Coaxial line & Diagonal slot & \(-5\) & \(\mathcal{O}\)63.9 \(\times\) 165.1 & CP & 4 and 6 \\
[16] & Coaxial line & Vertical slot & 5 & \(\mathcal{O}\)32 \(\times\) 236.2 & CP & 16.4 \\
[17] & Coaxial line & Coaxial slot & 8.4 & \(\mathcal{O}\)32 \(\times\) 1060 & CP & No date \\
[18] & Coaxial probe & Waveguide & 0 & \(\mathcal{O}\)23.5 \(\times\) 39.9 & CP & 1.8 \\ This work & Coaxial line & Cross slot & 4.1 & \(\mathcal{O}\)44 \(\times\) 262 & CP & 14.6 \\ \hline \end{tabular}
\end{table}
Table 2: Comparison of characteristics of several antennas.  
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