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15
Advanced Software Features
PLL gain change
PLL gain change is the amount in dB by which the theoretical gain of the PLL
must be adjusted to best match the smoothed measured loop suppression. The
parameters of the theoretical loop suppression that are modified are Peak
Tune Range (basically open loop gain) and Assumed Pole (for example a pole
on the VCO tune port that may cause peaking).
Maximum error
Maximum Error is the largest difference between the smoothed measured loop
suppression and the adjusted theoretical loop suppression in the frequency
range plotted for the smoothed measured loop suppression.
The frequency of the assumed pole is normally much greater than the Closed
PLL BW and there is no loop peaking. If the smoothed measured PLL
suppression shows peaking, the assumed pole is shifted down in frequency to
simulate the extra phase shift that caused the peaking. If the peaking is really
due to a single pole at a frequency near the Closed PLL BW, the adjusted
theoretical loop suppression and smoothed measured loop suppression will
show a good match and the maximum error will be small.
Accuracy degradation
Accuracy specification degradation is determined by taking the larger of
Maximum Error and magnitude of PLL Gain Change and then subtracting
1 dB.
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Agilent E5505A User's Guide
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