Agilent Technologies HP 8642A/B Specifiche Scaricare il pdf (Pagina 206)

Degradations of >4 dB, the PTR and Assumed Pole are adjusted when

the Theoretical Loop Suppression is fit to the smoothed measured Loop

Suppression. In these cases, the system will not display the adjusted PTR.

Any time the PTR must be adjusted by more than 1 dB (as indicated by an

Accuracy Specification Degradation of greater than 0 dB) it is an indication

that the Phase Detector Constant or the VCO Tuning Constant will be in

error at frequency offsets near the PLL BW, or that the PLL BW is being

affected by some other problem such as injection locking.

Assumed Pole: This is the frequency of the Assumed Pole required to

adjust the Theoretical Loop Suppression to match the smoothed measured

Loop Suppression. The Assumed Pole frequency will normally be much

greater than the PLL BW.

If the Assumed Pole is adjusted to a frequency of less than 10 X PLL BW,

peaking in the PLL Suppression is indicated. For PLL BWs less than

20 kHz, an Assumed Pole of less than 10 x PLL BW indicates a delay or

phase shift in the VCO Tune Port. Ibr PLL BWs greater than 20 kHz, the

Assumed Pole may be adjusted to less than 10 x PLL BW to account for

phase shifts in the HP 11848A.

Dev. Under Test: This indicates the device defined as the DUT for the

measurement, and how it is being controlled. The DUT cannot be one of

the sources listed in the System Configuration Table. You may, however,

select one of the HP 11848A internal sources as the DUT.

Reference Source: This indicates the device defined as the Reference

Source for the measurement, whether or not it is the VCO, and how it is

being controlled.

Ext. Timebase: This indicates whether or not an External Time Base is

being used, and whether it is the VCO for the measurement. (Note that

the HP 11848A 10 MHz A and 10 MHz B internal sources can only be

operated under system control.)

Param Summary 3-11

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Agilent Technologies HP 8642A/B Specifiche Pagina 206