Large antenna measurement in fresnel region using direct far-field measurement system

The reflector for the satellite communications or the array antenna with a few hundred radiating elements has the huge aperture dimension, and its far-field range satisfying D
far
= 2L
²
/λ is usually out of the its own anechoic chamber, where, L is the aperture diameter, and λ is free-space wavelength. For example, the far-field distance of the antenna of L=20 λ operating at 10 GHz is 24 m. Some antennas cannot be measured in Anechoic chamber because its far-field distance is a few km.