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. 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, it is required that the gain cut data be specified from -x1 to +x2 degrees across the boresight. For example, the azimuth is -90 degrees to +90 degrees and/or the elevation is -10 degrees to +40 degrees. When the data is available for a full circle cut (e.g., 0 to 360 degrees, or -180 degrees to +180 degrees) you must provide both end points (i.e., 0 and 360 points, or -180 and +180 points) 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. It is required that both elevation and azimuth profile data be measured at the beam’s maximum gain point. Please note that elevation cuts are required while the azimuth cuts are desired and may be substituted internally by STK.
This antenna uses a rectangular coordinate system.
The Elevation Azimuth Cuts data file format supports multi-beam data input. In areas where beam patterns overlap, gain is additive. For non-overlapping beams, 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 |
Indicates the data format and version of the data format. This keyword is required and must be the first line in the file. |
| AngleUnits | Degrees or Radians. Default units are in degrees. After this keyword, all angle data is expected in degrees or radians, and changed to radians for internal use. |
| GainValuesLinearScale | The “beam” gain values may be specified in linear scale. By default, the gain values are expected in dBs. |
| GainInterpolationLinearScale | Gain values may be interpolated in linear scale. By default, gain values are interpolated in dB scale. STK uses 1D linear interpolation to interpolate the data in between the gain samples. No extrapolation is attempted outside the data limits. You can specify that no data values to be used, as described below for the beam level keyword NoGainDataValue. |
| AntennaDiameter | The size of the antenna diameter or the broadside size of a rectangular dish specified in meters. |
| 3dBBeamwidth | The antenna’s main-lobe 3dB beam-width in degrees or radians as specified by the AngleUnits keyword. |
| BacklobeGain |
Provides the gain values to be used while STK is computing beyond +- 90 degrees in elevation and azimuth. Backlobe gain values are substituted in case the elevation and/or azimuth cut data does not extend to ± 180 degrees. These values are applied to the back hemisphere of the antenna pattern (i.e., azimuth or elevation values are more than 90 degrees). The gain values are specified in dB. The default value is -50 dB. |
| NumberOfElevationBeams | Number of elevation beams provided in the data file. The required value is from 1 to n. |
| PatternData |
Signifies that the antenna beam(s) profile data follows. The beams may be provided in any order. However, it is a good practice to stack beams from the low elevation to high elevation. |
| Beam Keyword | Description |
| Beam |
Beam number. The following keywords define the data profile for a particular numbered beam. |
| AzimuthCutType {UserAzimuthCutData | Sinc | Parabolic | SquareHorn | CosineAperture | CosineSquaredAperture | CosineSquaredPedestalAperture} |
Confirms that an azimuth profile cut data is available for this beam and is provided with the elevation profile cut data. If this keyword is omitted, STK substitutes an analytical azimuth profile cut. This is computed internally by STK. The default algorithm is a Sinc pattern. Type values are:
|
| GainDataNormalized | Beam gain values are normalized with respect to the maximum gain. The file contains the maximum gain as 0.0 dB value. |
| BeamMaxGainValue | Maximum gain value for this beam in dB. The default value is 40 dB. |
| NoGainDataValue |
Gain data value, in dB, to be used outside the available data limits. The data is not extrapolated. This value is substituted for the missing beam data in the front hemisphere of the antenna pattern (i.e., azimuth or elevation values are less than 90 degrees off the boresight). The default value is -40 dB. |
| BeamSwitchAngleLow |
Beam elevation lower limit value (in angle units), when this beam is switched to active. This may be useful when an antenna system has multiple stacked or overlapping beams. Default value is -180 degrees. |
| BeamSwitchAngleHi |
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 multiple stacked or overlapping beams. Default value is +180 degrees. |
| NumberOfElevationData | The number of “elevation gain” pair values for this elevation profile data array. The values may be continued on one line or on multiple lines. Elevation/Azimuth Cuts and Elevation Cuts sample files are below. |
| NumberOfAzimuthData |
The number of “azimuth gain” pair values for this azimuth profile data array. The values may be continued on a line or on multiple lines. Whenever the AzimuthCutType keyword is UserAzimuthCutData for a beam, the azimuth profile cut data is expected and must be provided. 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
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