Polarization Calibration: Difference between revisions
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:<math> Stokes Q = XX^* - YY^* </math> | :<math> Stokes Q = XX^* - YY^* </math> | ||
:<math> Stokes U = XY^* - YX^* </math> | :<math> Stokes U = XY^* - YX^* </math> | ||
:<math> P_{linear} = \sqrt{U^2 + Q^2} | :<math> P_{linear} = \sqrt{U^2 + Q^2} </math> | ||
:<math> \theta = \frac{1}{2}\atan{\frac{U}{Q}} | |||
== Polarization Mixing Correction == | == Polarization Mixing Correction == | ||
Due to relative feed rotation between az-al mounted antennas and equatorial mounted antennas | Due to relative feed rotation between az-al mounted antennas and equatorial mounted antennas |
Revision as of 20:00, 24 September 2016
Linear to Circular Conversion
At EOVSA’s linear feeds, in the electric field the linear polarization, X and Y, relates to RCP and LCP (R and L) as:
In terms of autocorrelation powers, we have the 4 polarization products XX*, YY*, XY* and YX*, where the * denotes complex conjugation. The quantities RR* and LL* are then
One problem is that there is generally a non-zero delay in Y with respect to X. This creates phase slopes in XY* and YX* from which we can determine the delay very accurately. As a check,
For completeness:
- <math> \theta = \frac{1}{2}\atan{\frac{U}{Q}}
Polarization Mixing Correction
Due to relative feed rotation between az-al mounted antennas and equatorial mounted antennas