XF uses the **theta, phi coordinate system's** $\theta$ and $\phi$ values to define far zone observation points and a plane wave's incident direction. In the coordinate system, $\theta$ is defined as the angle between the positive z-axis and an observation point and has a typical range of 0 to 180 degrees. The $\phi$ angle is defined as being between the positive x-axis and the observation point projected onto the XY plane and its typical range is between 0 and 360 degrees.

Electromagnetic fields can be broken into $\hat\theta$ and $\hat\phi$ vector components at the observation point ($\theta$, $\phi$).

XF uses the **alpha, epsilon Ludwig 2 coordinate system's** $\alpha$ and $\epsilon$ values to define far zone observation points. In the coordinate system, $\alpha$ is defined as the angle between the positive z-axis and the observation point projected onto the XZ plane and has a typical range of -90 to 90 degrees. The $\epsilon$ angle is defined as being between the positive z-axis and the observation point projected onto the YZ plane and its typical range is between 0 and 360 degrees.

Electromagnetic fields can be broken into $\hat\alpha$ and $\hat\epsilon$ vector components at the observation point ($\alpha$, $\epsilon$).

XF uses the **elevation, azimuth Ludwig 2 coordinate system's** $E$ and $A$ values to define far zone observation points. In the coordinate system, $E$ is defined as the angle between the positive z-axis and the observation point projected onto the YZ plane and has a typical range of -90 to 90 degrees. The $A$ angle is defined as being between the positive z-axis and the observation point projected onto the XZ plane and its typical range is between 0 and 360 degrees.

At the observation point (E, A), electromagnetic fields can be broken into $\hat E$ and $\hat A$ vector components.