## 5 Conclusions  
We have simulated 15 kinds of palm tree antennas in the 0.5-4.5 GHz frequency with several structures, namely Regular Palm Tree-Coplanar Vivaldi Antenna (RPT-CVA), Front Cut Palm Tree (FCPT-CVA), Middle Cut Palm Tree (MCPT-CVA), Back Cut Palm Tree (BCPT-CVA), Complete Cut Palm Tree (CCPT-CVA), Left Tilt Palm Tree (LTPT-CVA), Right Tilt Palm Tree (RVTP-CVA), Hilbert Fractal Structure Palm Tree (HFSPT-CVA), Koch Fractal Structure Palm Tree (KFSPT-CVA), Exponential Slot Edge Palm Tree (ESEPT-CVA), Vertical \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref** & \begin{tabular}{c} **Element Dimension** \\ **(mm)** \\ \end{tabular} & **Ant. Type** & **Sub. Type** & \
\begin{tabular}{c} **Freq.** \\ **(GHz)** \\ \end{tabular} &
\begin{tabular}{c} **Gain** \\ **(dBi)** \\ \end{tabular} \\ \hline
[50] & \(300\times 360\) & AVA & T-ceramic & 0.5–3 & - \\
[51] & \(258\times 150\) & CVA & FR-4 & 0.5–6 & 8 \\
[52] & \(950\times 780\) & CVA & - & 0.02–0.12 & - \\
[53] & \(260\times 185\) & AVA & Taconic & 0.5–2 & - \\
[54] & \(286\times 300\) & & FR4 & 0.7–2.1 & 10.5 \\
[55] & \(450\times 600\) & AVA & Rogers 4350 & 0.3–2 & 4.4–11.5 \\
[56] & \(750\times 525\) & CVA & FR4 & 0.26–0.34 & 4.2 \\ ESEPT & \(275\times 275\) & CVA & FR4 & 0.5–4.5 & 9.7 \\ MLPT & \(275\times 438\) & CVA & FR4 & 0.5–4.5 & 13.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of the proposed antenna and related research. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ant. Type** & \begin{tabular}{c} **S11 (dB)** \\ **At 0.5 GHz** \\ \end{tabular}  & \ \begin{tabular}{c} **S21 (dB)** \\ **At 0.5 GHz** \\ \end{tabular}  & **Max Dir (dB)** & **Min SLL (dB)** & \begin{tabular}{c} **Max Beamsquit (\({}^{\circ}\))** \\ **(0.5–4.5 GHz)** \\ \end{tabular}  & **Min Beamwidth (\({}^{\circ}\))** \\ \hline RPT & \(-8.33\) & \(-13.45\) & \(12.11\) (4 GHz) & \(-11.94\) (1 GHz) & \(25.46\) (2.5 GHz) & \(3.98\) (4.5 GHz) \\ FCPT & \(-7.29\) & \(-13.73\) & \(11.58\) (2 GHz) & \(-9.73\) (1 GHz) & \(25.84\) (2.5 GHz) & \(3.78\) (4.5 GHz) \\ MCPT & \(-10.04\) & \(-15.19\) & \(12.09\) (4 GHz) & \(-9.43\) (1 GHz) & \(25.50\) (2.5 GHz) & \(4.41\) (4.45 GHz) \\ BCPT & \(-10.48\) & \(-14.06\) & \(12.10\) (4 GHz) & \(-9.9\) (1 GHz) & \(25.46\) (2.5 GHz) & \(4.27\) (4.5 GHz) \\ C  
Wave Structure Palm Tree (VWPT-CVA), Horizontal Wave Structure Palm Tree (HWPT-CVA), Regular Lens Palm Tree (RLPT-CVA), Elliptical Lens Palm Tree (ELPT-CVA) and Metamaterial Lens Palm Tree (MLPT-CVA). By giving a different structure to the antenna radiator while maintaining the same substrate width and feed parameters and the similarity of the slope of the two tapered slots, the performance of return loss, mutual scaling, beam squint, and beamwidth produce different performances. From the simulation results, it is found that HWSPT gets the best mutual scaling performance at low frequencies because it has less than \(-10\) dB mutual scaring. The maximum directivity of the RPT-CVA is \(12.108\) dBi, while the MLPT-CVA has a gain of \(16.561\) dBi at the \(4\) GHz frequency. The beam squint at all frequencies is \(0^{\circ}\) for ELPT-CVA and the lowest beamwidth is also obtained by ELPT-CVA at \(4.5\) GHz. This comparative analysis can be used as a reference for the selection of MIMO antenna design in considering the performance requirements of return loss, mutual coupling, directivity, beam squint, and beam width. From the results of the return loss measurements, there is also a match between the simulation results and antenna measurements where the antenna can work at a frequency of \(0.5\)-\(4.5\) GHz so that this antenna can be recommended for radar applications. Conceptualization, N.N. and A.M.d.O. ; methodology, E.S. ; software, N.N. and D.K. ; validation, N.N. and E.S. ; formal analysis, N.N. and M.N.M.Y. ; investigation, D.K. ; resources, E.S. ; data curation, N.N. and D.K. ; writing--original draft preparation, N.N. ; writing--review and editing, E.S. and M.N.M.Y. ; supervision, A.M.d.O. ; project administration, N.N. ; funding acquisition, N.N.