A Primer On Antenna Near-Field And Far-Field For The Practical Engineer

For conformance and compliance, electromagnetic compatibility (EMC) and antenna performance testing, it is crucial to know the nuances of electromagnetic (EM) radiation from an antenna at given distances from the antenna aperture. This is important because the EM signal from an antenna behaves differently at various distances from the antenna, and if not properly accounted for, can result in substantial measurement errors. This is because there are three main regions where the EM radiation behaves differently as a function of distances away from an antenna: the reactive near-field, the radiating near-field/Fresnel Region and the far-field/Fraunhofer Region.