Near Field / Far Field

In the last blog I said that I would talk about near and far fields. When you have a tiny antenna you radiate in all directions. Some signals are going around the antenna and others are going out from it. Depending on the construction, the electric and magnetic components fall off at different rates in different directions. . The components decrease by different amounts depending on the distance from the antenna. Some at 1/r, some at 1/r2 and another at 1/r3 . The distance from the antenna at which the various components are all equal is defined at the boundary between the near and the far field. This happens to be λ/2π. Where λ is the wavelength of the signal. The near field is often also called the reactive field because when you are in that area you are also affecting the source of the signal i.e. you react with it.

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