Why is CNF (phi direction only) & SNF angular data density driven by MRE and not probe radial distance?
This is a very important concept that many customers misunderstand. CNF and SNF data sampling density is driven by the NF phase behaviour of the AUT radiating field. The MRE (maximum radial extent) defines a surface, centered on the coordinate system origin that encloses all radiating parts of the AUT. It therefore bounds the phase behaviour of what we are trying to measure and defines the worst case sampling density. As long as the NF probe is further than the MRE (which it always is since probe radial distance is > MRE) the phase behaviour measured will be the same, regardless if the NF probe is at MRE + 3 lambda or at infinity. It is important to realize that for a SNF system (not a CNF system, since it contains one linear scanning axis) it is only our desire to minimize chamber size and maximize RF power that drives us to move the NF probe closer to the AUT. From a SNF theory perspective we can have the NF probe on the moon and the measurement will require the same angular sampling
