Far Field Pattern

This option defines an ideal receiving antenna with an impressed radiation pattern.

Figure 1. The RA - Receiving antenna dialog.


Request name
The name of the request.
Load field data from
Feko Solver (*.ffe) file
Read the radiation pattern from an .ffe format file, created with DA and FF cards.
CST far field scan (*.ffs)
Read the radiation pattern from a CST far field scan.
The field data follows in the (*.pre) input file
The radiation pattern is specified in the .pre file following the RA card (the format of this file is described in the AR card). With this option FOR loops can be used to generate patterns from known functions.
Use last pattern defined at previous RA card
When using multiple RA cards (different receiving antennas in the same model) then it is quite common that the shape of the pattern is identical. If this is the case it is allowed to load the pattern just once and at subsequent RA cards to check this option. Then the last defined pattern will be used and memory can be saved (no need to store it again). Note that it is still possible to set the receiving antenna position and orientation individually.
external data file
Read the radiation pattern from an ASCII file (the format of this file is described in the AR card).
Include only the scattered part of the field
Consider only the scattered part of the field. If unchecked, the total field, that is the sum of the scattered and source contributions, are considered for calculation.
Position (coordinate)
In this group the X, Y and Z coordinates of the receiving point (the position where the antenna is placed) are entered in metres. This value is affected by the scale factor of the SF card if used.
Rotation about the axes
In this group the angles with which the imported pattern is rotated around the X, Y and Z axes are entered in degrees. These fields are referred to as α x , α y and α z in the rest of this discussion.
File name
The name of the .ffe, .ffs or ASCII input file.
Use all data blocks
Import all data blocks from the specified .ffe or .ffs file. The data is interpolated for use at the operating frequency.
Use only specified data block number
Use the data from the nth frequency block in the specified .ffe or .ffs file.
Use specified start point and range
Select a specific far field pattern in a .ffe or external file.
Start from point number
This parameter is only relevant when the data is read from a .ffe or an external file, and gives the line number of the first line to read from the input file. If the data must be read from the beginning of the file, the value in this field should be set equal to 1. This parameter is used when the .ffe file contains more than one pattern. For example, if the file contains the pattern at various frequencies, the correct pattern can be selected by setting this field to the appropriate value for each frequency. If the .ffe file is of a newer format and contains header data in addition to the data blocks, the point number refers to the actual point number excluding blank lines, comment lines and header lines.
Number of ϑ points
The number of ϑ angles in the pattern.
Number of φ points
The number of φ angles in the pattern.

The definition of the radiation pattern and the various different input formats supported for the RA card are identical to those of an impressed transmitting antenna (AR card). The Feko Examples Guide has more examples.

The ideal receiving antenna is considered to be decoupled from the model (that is the currents and charges are unchanged by including this antenna in the model) and should ideally be in the far field of radiating structures (so that incident plane wave approximations apply and the radial field component is small). Feko has internal checks to ensure these assumptions are valid.

Feko computes the power received by this ideal antenna assuming a perfect match, that is a complex conjugate load.

The relative phase of the received signal is also printed to the .out file, which indicates the relative phase of either the voltage or the current through the termination impedance (which is an ideal complex conjugate load). When using arrays of identical receiving antennas, then this relative phase information can be used to obtain the signal phase offsets of the various array elements (required for instance in the design of the feed network).