Polarization Types | Polarization Parameters
Polarization is a property of an electromagnetic wave that describes the orientation of the electric field vector with reference to the antenna's orientation. The three basic types of polarization are illustrated in the following figure:
In the illustration of linear polarization, the electrical field is polarized in the y direction in the coordinate system. In special cases of linear polarization, the electrical field is aligned vertically or horizontally with reference to the antenna. In the other two types of orientation shown, the tip of the E vector describes an ellipse and a circle, respectively, as it rotates over time. Circular polarization can be right-handed (as in the illustration) or left-handed.
STK computes the polarization match, which is a quantity between a transmitter and a receiver based on their polarization types, positions, and attitudes.
Reference: See Kraus, John D., Antennas, 2nd ed., New York: McGraw-Hill (1988), pp. 70-73.
For a simple receiver or transmitter model, you select the polarization type on the Model Specs tab. For all other receivers and transmitter models, you select the polarization type on the Antenna's Model Specs tab.
See the Technical Notes for a discussion of signal loss due to polarization mismatch.
STK Communications makes the following polarization types available:
Depending on the polarization type chosen, the following parameters are available for specification:
|Reference Axis||Applicable to the linear, vertical, horizontal, and elliptical polarization types. Specify the antenna body axis (X, Y, or Z) with respect to which the electrical field is oriented.|
|Tilt Angle||The angle between the reference axis and the electric field
If x axis is selected as the reference, positive tilt is measured from x to y in the xy plane.
If y axis is selected as the reference, positive tilt is measured from y to -x in the xy plane.
If z axis is selected as the reference, positive tilt is measured from z to x in the xz plane.
|Axial Ratio||Applicable to the elliptical polarization type, this is the ratio of the major to the minor axis of the polarization ellipse. The range is -1e+15 through -1.0 and 1.0 through 1e+15.|
Whenever STK detects a complete polarization mismatch between the transmitted signal and the received signal under ideal conditions, the Cross Polarization Leakage value is applied to model the less-than-ideal real-world performance. The value, ranging from -9999.9 dB to -0.001 dB, reflects the performance of the user's system, where -9999.9 dB represents ideal conditions (no leakage).
Note: Earlier versions of STK assume that there is no Cross Polarization Leakage.
The following figure illustrates tilt angle and axial ratio for the elliptical polarization type:
The polarization match between the transmitting and receiving object is calculated dynamically on a scale of 0 to 1, where 0 is no match and results in no received signal, and 1 is perfect (no loss).
Note: Currently, de-polarization due to rain is not supported.