## 4 Experiment Results and Discussion
The simulated and measured sidelobe levels for the z-x plane were \(-\)21.3 dB and \(-\)17.83 dB, respectively, for the 4 \(\times\) 1 patch array antenna using a tapered power distribution, and the measured sidelobe level increased by 3.47 dB. For the 4 \(\times\) 1 patch array antenna using a tapered power distribution appended with two metallic plates, the simulated and measured sidelobe levels for the z-x plane were \(-\)26.65 dB and \(-\)33.66 dB, respectively, and the sidelobe level decreased by 7.01 dB. For the y-z plane, the simulated and measured sidelobe levels were \(-\)15.04 dB and \(-\)16.17 dB, respectively, and the sidelobe level decreased by 1.13 dB. Note that the sidelobe levels for both the y-z and z-x planes were decreased by appending the two metallic plates. Table 1 compares the dimensions and performance of the proposed 4 \(\times\) 1 patch array antenna using a tapered power distribution appended with two metallic plates with other antennas in the literature. Electrical dimensions of the antennas were calculated using the freespace wavelength of the center frequency for the antennas. We can see that the volume of the proposed antenna is the smallest among the antennas in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**References**} & \multirow{2}{*}{**Antenna Type**} & \multicolumn{2}{c}{**Physical**} & **Electrical** & **Bandwidth (GHz)** & **Maximum** \\  & & **Dimensions (mm\({}^{3}\))** & **Dimensions (\(\boldsymbol{\lambda_{0}}^{3}\))** & **for VSWR \textless{} 2** & **Gain (dBi)** \\ \hline
[19] & Patch antenna + & 65 \(\times\) 60 \(\times\) 49 & 5.18 \(\times\) 4.78 \(\times\) 3.90 & 23.35–24.45 & 15.2 \\  & Hemispherical lens & & (96.57 \(\boldsymbol{\lambda_{0}}^{3}\)) & (f\({}_{\text{c}}\) = 23.9) & 15.2 \\  & Waveguide antenna + & & 10.09 \(\times\) 10.09 \(\times\) 3.63 & 28.0–40.0 & 25.7 \\  & Planar graded index lens & & (369.56 \(\boldsymbol{\lambda_{0}}^{3}\)) & (f\({}_{\text{c}}\) = 34.0) & 25.7 \\
[24] & 27 \(\times\) 1 slot array antenna + & 260 \(\times\) 74 \(\times\) 54 & 22.33 \(\times\) 6.36 \(\times\) 4.64 & 24.94–26.60 & 30.5 \\  & Two wing reflectors & & (658.97 \(\boldsymbol{\lambda_{0}}^{3}\)) & (f\({}_{\text{c}}\) = 25.77) & \\
[28] & 2 \(\times\) 1 series-fed patch & & 50 \(\times\) 30 \(\times\) 10 & 10.79 \(\times\) 6.48 \(\times\) 2.16 & 62.5–67.0 & 20.1 \\  & array antenna + PRS & & (151.03 \(\boldsymbol{\lambda_{0}}^{3}\)) & (f\({}_{\text{c}}\) = 64.75) & 20.1 \\ This Work & 4 \(\times\) 1 patch array antenna + Two metallic plates & & 30 \(\times\) 46.2 \(\times\) 47 & 2.40 \(\times\) 3.70 \(\times\) 3.77 & 23.35–24.45 & 16.8 \\  & & & (33.48 \(\boldsymbol{\lambda_{0}}^{3}\)) & (f\({}_{\text{c}}\) = 24.045) & 16.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of dimensions and performance of the proposed antenna with other antennas in the literature. Figure 10: Performance comparison of the fabricated antennas: (**a**) input reflection coefficients, (**b**) realized gain, (**c**) y-z plane radiation patterns at 24.125 GHz for the 4 \(\times\) 1 array antenna using uniform power distribution, (**d**) z-x plane radiation patterns at 24.125 GHz for the 4 \(\times\) 1 array antenna using uniform power distribution, (**e**) y-z plane radiation patterns at 24.125 GHz for the 4 \(\times\) 1 array antenna using tapered power distribution, (**f**) z-x plane radiation patterns at 24.125 GHz for the 4 \(\times\) 1 array antenna using tapered power distribution, (**g**) y-z plane radiation patterns at 24.125 GHz for the 4 \(\times\) 1 array antenna using tapered power distribution appended with two metallic plates, and (**h**) z-x plane radiation patterns at 24.125 GHz for the 4 \(\times\) 1 array antenna using tapered power distribution appended with two metallic plates.