Polarization Losses
STK uses a Poincaré Sphere representation of polarization states. To calculate the loss due to polarization mismatch, the angle between the transmitter's and receiver's vertical references in the plane perpendicular to the line of sight is computed. This angle is then used to rotate the Poincaré sphere representation of the transmitter in the receiver's coordinate system. The resultant loss is the square of the cosine of twice the angle between the two polarization states.
For further information, see Kraus, John D., Antennas, 2nd ed., New York: McGraw-Hill (1988).
Relationship to System Noise Temperature
When polarization is selected on a link, the antenna and system noise temperature values are halved before being used in a link performance. The parameters thus affected are:
- Tsun
- Tearth
- Train
- Tatmos
- Tcosmic
- Tother
These parameters are used by Tequivalent.
Relationship to Parent Body Attitude
You should bear in mind that polarization orientation is a direct function of the attitude of the antenna's parent body. When parent body attitude changes, the polarization alignment between the receiver and the transmitter may change, and these changes will impact g/T and subsequent link performance values such as C/N, Eb/No, BER, etc.