Functions Available by Loading phase_centre_utility

The methods (or functions) available include the two phase centre calculations, a method to translate a far field to a new origin and a method to normalise (set zero phase reference) the phase of the far field.

phase_centre_m1

Description:
The first method calculates the phase centre at any point within the far field request. The result is the phase centre in the particular direction, but since the radiation pattern is not an isotropic radiator, the value is not the phase centre in other directions.
Arguments:
  • Far field: The far field result that will be analysed.
  • Far field component function: This function must calculate and return the far field component to be analysed. It could be as simple as a function that returns one of the components (θ or ϕ) or it could calculate and return a circularly polarised field component.
  • [Optional] Frequency index: The first frequency is analysed by default.
  • [Optional] Theta index: The centre index is analysed by default.
  • [Optional] Phi index: The centre index is analysed by default.
Return:
A table containing the location (three coordinates) of the phase centre (global coordinate system).

phase_centre_m2

Description:
The second method tries to minimise the maximum phase deviation over the entire viewing angle. It can be time-consuming, since it calculates the phase centre in a volume and then selects the point that resulted in the least phase deviation. The speed can be improved considerably by rather performing an iterative search, each time reducing the size of the volume, but also the spacing between sampling points.
Arguments:
  • Far field: The far field result that will be analysed.
  • Far field component function: This function must calculate and return the far field component to be analysed. It could be as simple as a function that returns one of the components (θ or ϕ) or it could calculate and return a circularly polarised field component.
  • [Optional] Side length of search volume: The side length of the cube volume that will be analysed. A side length of one wavelength is used by default. It is recommended to supply this value since the number of points should also be supplied (next parameter).
  • [Optional] Number of points per dimension: By default, only a single point will be analysed and it is recommended to supply a value for the number of points. A value of 10 is often used.
  • [Optional] Frequency index: The first frequency is analysed by default.
Return:
A table containing the location (three coordinates) of the phase centre (global coordinate system).

move_far_field_origin

Description:
This method moves the far field origin to a new coordinate and also adjusts the phase of each far field component accordingly.
Arguments:
  • Far field: The far field result that will be analysed.
  • New origin: A table containing the three coordinates of a the new global origin.
  • [Optional] Original/old origin: A table containing the three coordinates of the current global origin. When this parameter is not supplied, it will be read from the metadata of the far field result object.
Return:
A far field result object is returned that is located at the new origin.

normalise_ff_phase

Description:
The far field phase for a specified component at a single point is calculated and then the phase is subtracted. This allows the phase of different far fields to be compared easily.
Arguments:
  • Far field: The far field result that will be analysed.
  • Far field component function: This function must calculate and return the far field component to be analysed. It could be as simple as a function that returns one of the components (θ or ϕ), or it could calculate and return a circularly polarised field component.
  • [Optional] Frequency index: The first frequency is analysed by default.
  • [Optional] Theta index: The centre index is analysed by default.
  • [Optional] Phi index: The centre index is analysed by default.
Return:
A far field result object is returned with the adjusted phase.