When a signal from a transmitter sends out electromagnetic waves to free space (usually via an Antenna). The Electromagnetic field characteristics vary as a function of distance from the signal source. These fields are broadly divided into two regions, the near-field region, and the far-field region. To maximise certain characteristics of the signal, EM measurements are made in these regions and then used to model (with advanced software) future signal possibilities and antenna requirements. This is the transformations part. This is the area of applied mathematics and computational electromagnetics that sits behind advanced antenna design.