Increasing The Pll Bandwidth - Keysight Technologies N5511A User Manual

Absolute Measurement Fundamentals
Minimizing Injection Locking

Increasing the PLL Bandwidth

If the injection locking bandwidth is less or equal to the PLL bandwidth, it may
be possible to increase the PLL bandwidth sufficiently to complete the
measurement. The PLL bandwidth is increased by increasing the peak tuning
range (PTR) for the measurement.
The PTR for the measurement is set by the tuning characteristics of the VCO source you are
using.
increase in the PTR. For information on the limitations of increasing the PTR, refer to
the PTR"
To estimate the PTR needed to prevent injection locking from causing the
system to lose lock:
1. Determine the injection locking bandwidth. Tune the beat note toward
2. Multiply the injection locking bandwidth by 2 to determine the minimum
3. Locate the required PLL bandwidth in
N5511A Phase Noise Test System User's Guide
Figure 5-16 shows that increasing the PLL bandwidth can require a substantially larger
in this section.
0 Hz using the procedure described in the Checking the beat note section
of each phase lock loop measurement example in this chapter. When the
injection locking occurs, the beat note disappears. The injection locking
bandwidth is the frequency of the beat note just prior to where the
injection locking occurs as the beat note is tuned toward 0 Hz.
PLL bandwidth required to prevent the injection locking from causing the
system to lose lock. (To prevent accuracy degradation, it may be
necessary to increase the PLL bandwidth to 4 X the injection locking
bandwidth. The computer informs you during the measurement if the
possibility of accuracy degradation exists.)
required for the measurement. (For details on increasing the PTR, refer to
"Changing the PTR" in this section.
Figure 5-16 to determine the PTR
"Changing
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