# `Radiation Pattern`

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 A radiation pattern defines the variation of the power radiated by an antenna as a function of the direction away from the antenna. This power variation as a function of the arrival angle is observed in the antenna's far field. As an example, consider the 3-dimensional radiation pattern in Figure 1, plotted in decibels (dB) . Figure 1. Example radiation pattern for an Antenna (generated with FEKO software). This is an example of a donut shaped or toroidal radiation pattern. In this case, along the z-axis, which would correspond to the radiation directly overhead the antenna, there is very little power transmitted. In the x-y plane (perpendicular to the z-axis), the radiation is maximum. These plots are useful for visualizing which directions the antenna radiates. Typically, because it is simpler, the radiation patterns are plotted in 2-d. In this case, the patterns are given as "slices" through the 3d plane. The same pattern in Figure 1 is plotted in Figure 2. Standard spherical coordinates are used, where is the angle measured off the z-axis, and is the angle measured counterclockwise off the x-axis.