Wait, I know that: The near-field zone of an antenna is defined from the ratio of its aperture size to wavelength.
But I have 2 problems with this definition.
1) This is true for an aperture antenna, but what is the aperture size for another kind of antenna (i.e. patch) ?
2) In order to compute the far-field from the near-field, it is necessary the use of a probe, so is correct that the distance between the antenna under test and the probe is less than that ratio but I don't want that there is a strong coupling between these antennas. So, what is the common distance to use ?