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PLL Gain Change
Maximum Error
Accuracy
Degradation
Supporting an
Embedded VXI PC:
Document Part No. E5500-90024Ed. 1.0
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 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 spec. degradation is determined by taking the larger of
Maximum Error and magnitude of PLL Gain Change and then
subtracting 1 dB.
A.02.00 also allows the use of an embedded VXI PC running
Microsoft® Windows® 2000. In this case, the VXI interface to the VXI
assets will be "VXI direct" (select within the Asset Manager
Configuration). The VISA I/O libraries must also support the
embedded PC's GPIB card.
E5500 Phase Noise Measurement System Version A.02.00
Advanced Software Features
PLL Suppression Verification Process
16
16-13
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