The size of the computational domain in this case is about 20λ<sub>0</sub> × 20λ<sub>0</sub> × 15λ<sub>0</sub>. Using the same mesh density of 15 cells per effective wavelength, a very large FDTD grid (636 x 632 x 443) is generated with a total of 178,064,736 cells. The FDTD simulation was run on the same ASUS laptop computer and converged after 9,275 time steps. The total simulation time was 235 minutes including both the FDTD time marching loop and computation of the high-resolution 3D far-field radiation pattern.
The figure below shows the dB-scale 3D far-field radiation pattern of the larger parabolic reflector with the pyramidal horn feed. As you can see from the figure, the value of the directivity has increases increased by about 3.5dB35dB compared to the reflector of the previous case with the smaller aperture size.Moreover, the main beam exhibits a better symmetry in the principal planes.
<table>
<tr>
<td>
[[Image:ART PARAB Fig30.png|thumb|left|640px480px| 3D far-field radiation pattern of the larger parabolic reflector with the pyramidal horn feed on a dB scale.]]
</td>
</tr>