
Table 8-1. 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 modulation
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 function of
the Peak Tuning Range (PTR) in Figure 8-2. (The PTR for the measurement is determined
by multiplying the VCO's Tuning Constant by its Voltage Tuning Range.)
N
X
c
o
m
Q_
1M
100k
10k
1k
100
10
1
-
-
-
-
-
-
"T'T"'
I 1
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f
1 !
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.1 i 10 100 1k 10k 100k 1M 10M 100M 1G
Peak Tuning Range (Hz)
* Lag/Lead Filter Number
Figure 8-2. Phase Lock Loop Bandwidth as a Function
of the Peak Tuning Range of the Measurement.
8-4 Numbered Error Messages
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