=== Computing Far-Field Characteristics in FDTD ===
Far fields are the asymptotic form the fields when R &rightarrowrarr; ∞ 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} \times E_{ff}} </math>