# Near Field Aperture

This option defines an ideal receiving antenna with a near field aperture (single or multiple surfaces).

## Parameters:

Feko Solver (*.efe/*.hfe) file
Read the field values from .efe/.hfe format files calculated by Feko. The files should contain values describing a single face. The field data files are requested with the DA card.
CST near field scan (CST NFS)
Read the field values from CST NFS format files.
Sigrity (*.nfd) input file
Read the field values from a .nfd file.
Orbit/Satimo (*.mfxml) measurement file
Read the field values from a .mfxml file.
ASCII text file
Read the field values from an ASCII file.
The file data follows in the (*.pre) input file
The field values are specified in the .pre file. The format of this file is described in the AR card.
This option is selected when a new near field aperture is defined which is added to previously defined apertures. The receiving power for the multiple near field apertures is not computed.
Add to existing apertures and compute receiving power
This option is selected if a single near field aperture or the last of multiple near field apertures is defined. All defined near field apertures defined before and including this one are taken into consideration and the receiving power is computed.
Include only the scattered part of the field
When this item is checked, only the scattered part of the field is considered for calculation. Otherwise the total field, the sum of the scattered and source contributions, are considered for calculation.
...aperture
Select a planar, cylindrical or spherical aperture.
Also sample along edges
Check this option to extend the samples up to the edges of the aperture. When it is unchecked, the samples will be offset from the edges of the aperture.
S1, S2 and S3
These text boxes are for input points (see the DP card) that define the orientation of the aperture. The figure on the dialog will depict the orientation.
For a planar aperture the input points define the position of the origin and the direction of the ${\stackrel{^}{u}}_{2}$ and ${\stackrel{^}{u}}_{3}$ directions respectively. (The field data is assumed to vary first along the ${\stackrel{^}{u}}_{2}$ direction.)
Note: The normal n is determined by S1, S2 and S3 and should correspond to the primary direction of power flow as seen when the aperture is in transmit mode. If S1, S2 and S3 are not carefully defined, it may result in negative received power.
For cylindrical and spherical apertures S1, S2 and S3 define the origin and the direction of the local Z axis and X axis respectively. All angles are relative to these axes and are obtained from the .efe and .hfe files, but the origin is determined from S1, S2 and S3.
E-field file name
The input file name from which the electric field data must be read. This may be either an .efe file or a text file (with units V/m).
H-field file name
The input file name from which the magnetic field data must be read. This may be either an .hfe file or a text file (with units A/m).
Start from point number
The number of the first field point to be used for the aperture. If set to 1, field values are read from the start of the file, for larger values the first point number-1 values (.efe and .hfe files) or lines (text files) are ignored. This may be used, for example, if the data file contains the field values for more than one frequency. This corresponds to the line number if all non-data lines are stripped from the file. The Start from point number field is not used if the field data is obtained from the .pre input file
Number of points along
These two text boxes specify the number of field points along each of the two axes of the aperture.
Aperture orientation
Define the aperture orientation by specifying the reference points (S1, S2 and S3) in relation to the aperture.
S1, S2 and S3
Define the orientation of the aperture.
Directory
The directory where the CST near field scan (NFS) files are located.
File name
The input file name from which the Sigrity (.nfd) or Orbit/Satimo (.mfxml) files are read.
Use data block number
Use the data from the nth data block in the Cartesian boundary .efe/hfe file(s), CST near field scan (CST NFS) files, Sigrity (.nfd) file or Orbit/Satimo (.mfxml) measurement file.