# Far Fields

View the quantities and properties that are available for a far field request.

On the Home tab, in the Add results group, click the Far Field Source icon.

Table 1. Properties for far field requests.
Quantity Properties
Electric field Total
Gain Theta
Realised gain Phi
Directivity Ludwig III (Co)
Radar cross section (RCS) Ludwig III (Cross)
LHC
RHC
Axial ratio Minor / Major
Major / Minor
Handedness

The options available for far fields:

Total
The total value independent of the polarisation.
Theta
The vertical (or $\theta$ ) component.
Phi
The horizontal (or $\varphi$ ) component.
Ludwig III (Co)
The reference polarisation as defined by Ludwig for conventional measurement configurations. An antenna that is Z directed implied for which the reference polarisation is intended along the $\varphi ={90}^{\circ }$ cut.
(1) $LII{I}_{Co}\left(\theta ,\varphi \right)=E\left(\theta ,\varphi \right)\cdot \left[\mathrm{sin}\left(\varphi \right){\stackrel{^}{i}}_{\theta }+\mathrm{cos}\left(\varphi \right){\stackrel{^}{i}}_{\varphi }\right]$
Ludwig III (Cross)

The cross polarisation as defined by Ludwig for conventional measurement configurations. An antenna that is Z directed implied for which the reference polarisation is intended along the $\varphi ={0}^{\circ }$ .

(2) $LII{I}_{Cross}\left(\theta ,\varphi \right)=E\left(\theta ,\varphi \right)\cdot \left[\mathrm{cos}\left(\varphi \right){\stackrel{^}{i}}_{\theta }-\mathrm{sin}\left(\varphi \right){\stackrel{^}{i}}_{\varphi }\right]$

Conventions for the Ludwig coordinate system are defined by the following parameters:
$\theta$ and $\varphi$
Rotational angles in the spherical coordinate system as defined in Feko.
${\stackrel{⌢}{i}}_{\theta }$
Directional unit vector in the $\theta$ direction.
LHC
The left hand circularly polarised component. The polarisation vector rotates counter clockwise when viewed from a fixed position in the direction of propagation.
RHC
The left hand circularly polarised component. The polarisation vector rotates counter clockwise when viewed from a fixed position in the direction of propagation.
Z (+45°)
When viewed in the direction of propagation, the $\theta$ unit vector points downwards and the $\varphi ={90}^{\circ }$ unit vector to the left. The Z-polarisation vector is then
(3) ${\stackrel{^}{i}}_{Z}=\frac{\left({\stackrel{^}{i}}_{\theta }+{\stackrel{^}{i}}_{\varphi }\right)}{\sqrt{2}}$
which lies along an axis rotated +45 degrees from horizontal (in a counter clockwise direction) — coinciding with the direction of the diagonal line of the Z.
S (-45°)
The S-polarisation unit vector is
(4) ${\stackrel{^}{i}}_{S}=\frac{\left({\stackrel{^}{i}}_{\theta }+{\stackrel{^}{i}}_{\varphi }\right)}{\sqrt{2}}$
which rotated by -45° from horizontal and lies in the direction approximated by the diagonal of the S.
Minor/Major
Displays the magnitude of the axial ratio using the axes specification, Minor/Major.
Major/Minor
Displays the magnitude of the axial ratio using the axes specification, Major/Minor.
Handedness
Displays the sign information for axial ratio on a sphere using different colours for left hand rotating, linear and right rotating fields.