Aperture Antenna vs Patch

Hi all.

Can patch be considered as an aperture antenna. If yes and use the aperture antennas equations for calculating its directivity (D = Physical area * 4pi/ lamda^2). I get totally wrong results.

Thanks in advance

The patch antenna can NOT be considered as an aperture with the same dimension as the patch length (L) and width (W). Instead, it can be modelled as two magnetic dipoles of length (W), s separated by a distance (L) and with uniform current distribution. You can compute analytically the radiation pattern of the previous, and by averaging the field you can compute the directivity. I think directivity should be around 8dB.