[[NeoScan]] systems can be used as an essential tool for characterization, test and evaluation of antennas and phased array systems. It is a well-established fact that once you have an accurate estimate of the aperture fields, you can compute the far-field radiation patterns of an antenna with reasonable accuracy. This fact is based on the equivalence principle and the Huygens theory in electromagnetics. Time domain electromagnetic simulation tools such as [[EM.Tempo]] use a near-to-far-field transformation based on this principle to compute the far-zone fields of any radiating structure. In general, by far fields we mean the electric fields evaluated in the far zone of a physical structure, which satisfies the following condition:
:<math>r << \frac{2D^2}{\lambda_0}</math>
where r is the distance between the observation and source points, λ<sub>0</sub> is the free space wavelength and D is the largest dimension of the radiating structure.