Setting a state of Polarization
Setting the Worst Case Transmission SoP
26
Agilent
8169A
Polarization Controller, Second Edition
Setting the Worst Case
Transmission SoP
We set the state of polarization for the worst case transmission, because
we can find this more accurately (the resolution of the power meter stays
the same, but the full scale value is lower, therefore we can be more
accurate). We also use the fact that the relationship between power of the
signal transmitted through the DUT and polarization on the surface of the
sphere can be expressed as concentric circles about the worst case (or
optimum), and that for a linear DUT the worst case and optimum are on
opposite sides of the sphere.
Figure 7 Power contours about the worst case on the poincare sphere
This means that we find the worst case position by moving around the
sphere along the equator first (that is finding the angle of longitude of the
worst case) and then the overall worst case by moving around this line of
longitude.
Figure 8 Power contours with a search path to the worst case transmission state of polar-
ization