Can you give IEEE paper refrence?
The classic gain-transfer method assumes a uniform plane wave incident over the apertures of the gain-transfer standard (typically a standard-gain horn) as well as the antenna under test. Variations in the incident field over the quiet zone of an antenna test range can produce large errors in the estimated gain of the antenna under test. These errors can be significant, especially when there is a large difference in aperture dimensions between the antenna under test and the standard-gain horn.