HP 3048A Operating Manual page 170

Table 3-25. Numbered Error Messages (3 of 17)
2
(cont'd)
1. Narrow Modulation Bandwidth
A noise hump on a relatively clean loop suppression curve occurs when the modu­
lation bandwidth of the VCO's tune port is not wide enough to provide adequate phase
margin for the system's phase lock loop (PLL). The VCO's modulation bandwidth (the
upper frequency limit of the VCO's tuning port) should be greater than approximately ten
times the PLL bandwidth set for the measurement. PLL bandwidth is shown as a func­
tion of the Peak Tuning Range (PTR) in Figure 3-34. (The PTR for the measurement is
determined by multiplying the VCO's Tuning Constant by its Voltage Tuning Range.)
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—TT
-
10 100 1k 10k 100k 1M 10M 100M 1G
Peak Tuning Range (Hz)
* Lag/Lead Filter Number
Figure 3-34. Phase Lock Loop Bandwidth as a Function
of the Peak Tuning Range of the Measurement.
rev.UJUL88 Signal Source Applications 3-123