Near field Goal

Optimise the near fields that are solved as part of the Feko model.

On the Request tab, in the Optimisation group, click the

Add goal function icon. From the drop down list, select

Near field goal.

The Focus is identified based on the label of a Near fields request in CADFEKO or of an FE card in EDITFEKO.

The following focus types can be optimised:

Electric field: The electric field part of the near field is considered.
Magnetic field: The magnetic field part of the near field is considered.
Electric flux density (normalised): The Electric flux density (normalised) considers the electric field scaled by the relative permittivity of the medium where the near field is calculated. These are normalised quantities, with the electric flux densities scaled by the permittivity of free space. The normalisation prevents the goal function from having values that are small enough for the optimiser to consider them to be zero.
Magnetic flux density (normalised): The Magnetic flux density (normalised) considers the magnetic field scaled by the relative permeability of the medium where the near field is calculated. These are normalised quantities, with the magnetic flux densities scaled by the permeability of free space. The normalisation prevents the goal function from having values that are small enough for the optimiser to consider them to be zero.

Note: If the focus type attempts to access a part of the near field output request that was not requested (for example only electric fields requested but optimisation is for magnetic fields) then an error will be returned during the evaluation of the goal in the first optimisation iteration.

Coordinate System

The coordinate system in which the directional component of the near field is required must be selected. The available coordinate systems are Cartesian, Cylindrical(X)/(Y)/(Z), Spherical and Conical. This coordinate system selection defines the options available in the Directional component drop-down list.

Note: The coordinate system chosen here differs from the coordinate system chosen as part of the near field computation request.

The coordinate system choice in the near field goal is related to the near field component of interest, while the coordinate system chosen in the near field output request dialog is related to the positioning of the sample points for the near field calculation. This distinction makes it possible to consider the near field component in any direction independently of the physical placement of the near field sampling points.

Directional Component

The options available in the Directional component drop-down list depends on the choice of Coordinate system, but are independent of the near field request sampling point positions.

Radial or X/Y/Z/Phi/Theta-directed: In the chosen Coordinate system, the field in any of the 3 coordinate directions may be requested. Each individual component of the electric or magnetic near field is a complex quantity, and the selection of a specific field component requires that there be at least one general processing step which indicates the selection of one of the complex components.
Combined: In addition to the individual components in the coordinate directions, the Combined near field value may be requested. This value is computed by combining all 3 directional components of the field at each point as follows (shown for Cartesian components):
(1) $E_{combined} = \sqrt{{| F_{x} |}^{2} + {| F_{y} |}^{2} + {| F_{z} |}^{2}}$; The choice of Coordinate system has no effect on the value of the Combined component. The combined field is always a non-complex value (or an array of non-complex values) and it is therefore not required that any further processing is performed.