IE3D array radiation pattern calculation problem?

Hi, I have a question about the IE3D array radiation pattern calcuation in the PatternView.

I have tried to use a half-wavelength dipole along z-axis, the single element pattern is pretty well, with directivity about 2.2dBi (Theory shows 2.15dBi).

However, when I tried to use IE3D "array pattern calculation" in the PatternView, with two element along x-axis perpendicular to the dipole arm, with spacing half wavelength, the IE3D can get the null along this axis as theory predicts, but the maximum gain becomes about 6.0dBi at the y-axis.

But I think two antenna can increase the directivity by 3dB (10*log10(2)) only, so the confusion comes out that 6.0 dBi~=2.2 dBi+3 dB...

Although the discrepancy is only a little, but I am still wondering anyone met this problem before?

Hi, Wingji:

When you have 2 dipoles, its directivity is not just 3 dB more. It is dependent upon how you locate them. The gain in directivty can be higher or smaller than 3 dB.

Regards,

Yes, it seems I made a mistake about the directivity concept. Thanks for your notices, Jian.