Far fields are the asymptotic form the fields when R → ∞ or k<sub>0</sub>R >> 1. Under these assumptions, the fields propagate outward as transverse electromagnetic (TEM) waves:
<math> \mathbf{H_{ff}} = \frac{1}{\eta_0} \mathbf{ \hat{k} \cross \mathbf{times E_{ff}} </math>
Far fields are typically computed in the spherical coordinate system as functions of the elevation and azimuth observation angles θ and φ.