The Elevation Azimuth Cuts Antenna file contains an elevation profile cut and, optionally an azimuth profile cut, from a gain pattern. STK will attempt to create a 3D pattern by combining the profiles and interpolating the data.
Azimuth is measured off the antenna boresight (Z axis) in the Y-Z plane, and elevation is measured off the antenna boresight in the Z-X plane. A point (Elevation =0, Azimuth = 0) in the data file is taken as the antenna's mechanical boresight value. It does not have to be the maximum gain value of the gain pattern.
If the elevation or the azimuth data is restricted to the front hemisphere of the gain pattern, you must specify the gain cut data from -x1 to +x2 degrees across the boresight. An example is when the azimuth is -90 degrees to +90 degrees, or the elevation is -10 degrees to +40 degrees. When data is available for a full-circle cut (for example, 0 to 360 degrees, or -180 degrees to +180 degrees), you must provide both end points (in other words, points at both 0 and 360 degrees, or ponts at -180 and +180 degrees) for proper interpolation of the data.
In the case where only an elevation profile cut is available, STK will substitute an analytical gain profile in the azimuth direction. Both elevation and azimuth profile data must be measured at the beam’s maximum gain point. Elevation cuts are required, while the azimuth cuts are desired but STK can generate them if need be.
You can specify an antenna that uses a rectangular coordinate system.
The Elevation Azimuth Cuts data file format supports multibeam data input. In areas where beam patterns overlap, gain is additive on a linear scale. For beams that do not overlap, the max beam elevation angle should be slightly less (on the order of 1.0e-6 deg) than the low angle of the next higher beam.
Antenna keywords apply to all the beams in the file.
Beam keywords apply to individual beams.
| Antenna Keyword | Description |
|---|---|
| ElevationAzimuthCuts v1 |
Enter the data format and version of the data format. This keyword is required and must be the first line in the file. |
| AngleUnits | Specify either Degrees or Radians. If you do not, the default units are in degrees. After this keyword, all angle data is expected in the unit you specify; STK changes it to radians for internal use. |
| GainValuesLinearScale | You may specify the “beam” gain values in a linear scale. By default, STK expects the gain values in dBs. |
| GainInterpolationLinearScale | By default, STK interpolates gain values in a dB scale. Use this to have STK interpolate gain values in a linear scale. STK uses 1D linear interpolation to interpolate the data between the gain samples, and it does not attempt extrapolation outside the data limits. You can specify that no data values be used, as described below for the beam level keyword NoGainDataValue. |
| AntennaDiameter | Specify the size of the antenna diameter or the broadside size of a rectangular dish in meters. |
| 3dBBeamwidth | Enter the antenna’s main-lobe 3dB beam width in degrees or radians, as specified by the AngleUnits keyword. |
| BacklobeGain |
Provide the gain values to be used while STK is computing beyond +- 90 degrees in elevation and azimuth. STK substitutes Backlobe gain values in the case when elevation and/or azimuth cut data does not extend to ± 180 degrees. STK applies these values to the back hemisphere of the antenna pattern (i.e., azimuth or elevation values greater than 90 degrees). The gain values are specified in dB. The default value is -50 dB. |
| NumberOfElevationBeams | Specify the number of elevation beams provided in the data file. The required value is 1 or a greater integer. |
| PatternData |
This keyword signifies that the antenna beam(s) profile data follows. You may provide the beams in any order. However, it is a good practice to stack beams from low elevation to high elevation. |
| Beam Keyword | Description |
| Beam |
This is the beam number. The following keywords define the data profile for this particular numbered beam. |
| AzimuthCutType {UserAzimuthCutData | Sinc | Parabolic | SquareHorn | CosineAperture | CosineSquaredAperture | CosineSquaredPedestalAperture} |
Confirms that azimuth profile cut data is available for this beam and is provided with the elevation profile cut data. If you omit this keyword, STK substitutes an analytical azimuth profile cut. This is computed internally by STK. The default algorithm is a Sinc pattern. Type values are:
|
| GainDataNormalized | This tells STK that the beam gain values are normalized for the maximum gain. The file then contains the maximum gain as 0.0 dB. |
| BeamMaxGainValue | Specify the maximum gain value for this beam in dB. The default value is 40 dB. |
| NoGainDataValue |
This is the gain data value, in dB, for STK to use outside the available data limits. The data is not extrapolated. STK substitutes this value for the missing beam data in the front hemisphere of the antenna pattern (i.e., azimuth or elevation values less than 90 degrees off the boresight). The default value is -40 dB. |
| BeamSwitchAngleLow |
Specify the beam elevation lower limit value (in angle units) when this beam is switched to active. This may be useful when an antenna system has stacked or overlapping beams. The default value is -180 degrees. |
| BeamSwitchAngleHi |
Specify the beam elevation upper limit value (in angle units) when this beam is switched to active. This may be useful when an antenna system has stacked or overlapping beams. The default value is +180 degrees. |
| NumberOfElevationData | Specify the number of “elevation gain” pair values for this elevation profile data array. The values may either continue on one line or be on two or more lines. Elevation/Azimuth Cuts and Elevation Cuts sample files are below. |
| NumberOfAzimuthData |
Specify the number of “azimuth gain” pair values for this azimuth profile data array. The values may either be on one line or on two or more lines. Whenever the AzimuthCutType keyword is UserAzimuthCutData for a beam, you must provide the azimuth profile cut data. Elevation/Azimuth Cuts and Elevation Cuts sample files are below. |
Sample files
If you include data for multiple beams in the Elevation Azimuth Cuts Antenna file, you must put the azimuth data (if available) along with the elevation data for the respective beam, as shown in the Elevation/Azimuth Cuts sample format.
You can include or omit azimuth data for each beam, on a beam by beam basis, by specifying the AzimuthCutType keyword.
Elevation/Azimuth Cuts for one beam file sample format
ElevationAzimuthCuts v1 AngleUnits Degrees AntennaDiameter 4.5 3dBBeamwidth 1.5 BacklobeGainValue -30.0 NumberOfElevationBeams 1 PatternData Beam 1 GainDataNormalized AzimuthCutType UserAzimuthCutData BeamMaxGainValue 36.5 NoGainDataValue -50.0 BeamSwitchAngleLow -5.0 BeamSwitchAngleHi 53.0 NumberOfElevationData 13 -5.0 -20.0 0.0 -6.0 2.7 0.0 5.0 -4.0 10.0 -6.4 20.0 -8.0 30.0 -8.9 36.0 -12.0 41.0 -16.0 44.5 -20.0 46.8 -24.0 50.0 -28.0 53.0 -32.0 NumberOfAzimuthData 901 -90.000 -35.75751437 -89.800 -35.75732440 -89.600 -35.75676176 -89.400 -35.75584831 -89.200 -35.75462044 -89.000 -35.75312909 -88.800 -35.75143974 -88.600 -35.74963236 -88.400 -35.74780144 -88.200 -35.74605595 -88.000 -35.74451934 -87.800 -35.74332959 -87.600 -35.74263918 -87.400 -35.74261518 -87.200 -35.74343936 -87.000 -35.74530823 -86.800 -35.74843327 -86.600 -35.75304111 -86.400 -35.75937382 -86.200 -35.76768921 . . . 89.000 -35.75312909 89.200 -35.75462044 89.400 -35.75584831 89.600 -35.75676176 89.800 -35.75732440 90.000 -35.75751437
Elevation Cuts for one beam file sample format
ElevationAzimuthCuts v1 AngleUnits Degrees AntennaDiameter 4.5 3dBBeamwidth 1.5 BacklobeGainValue -30.0 NumberOfElevationBeams 1 PatternData Beam 1 GainDataNormalized BeamMaxGainValue 36.5 NoGainDataValue -50.0 BeamSwitchAngleLow -5.0 BeamSwitchAngleHi 53.0 NumberOfElevationData 13 -5.0 -20.0 0.0 -6.0 2.7 0.0 5.0 -4.0 10.0 -6.4 20.0 -8.0 30.0 -8.9 36.0 -12.0 41.0 -16.0 44.5 -20.0 46.8 -24.0 50.0 -28.0 53.0 -32.0