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Changing the PTR
The Tuning
Qualifications
Document Part No. E5500-90024Ed. 1.0
The peak tuning range (PTR) for the phase lock loop measurement is
set by the tune range entered for the VCO and the VCO's tuning
constant. (If the calibration technique is set to measure the VCO
tuning constant, the measured value will be used to determine the
system's PTR.)
PTR= VCO Tuning Constant X Voltage Tuning Range
From the PTR, the phase noise software derives the capture and drift
tracking Ranges for the measurement. These ranges set the frequency
stability requirements for the sources being used.
The PTR also determines the phase lock loop (PLL) bandwidth for
the measurement. An important attribute of the PLL bandwidth is
that it suppresses the close-in noise which would otherwise prevent
the system from locking the loop.
Changing the PTR is accomplished by changing the tune range of VCO
value or the VCO tuning constant value or both. There are several
ways this can be done. However, when considering these or any other
options for changing the PTR, it is important to remember that the
VCO source must always meet the following tuning qualifications.
G
The tuning response of the VCO source must always remain
monotonic.
G
The VCO source's output level must remain constant across its
tuning range.
E5500 Phase Noise Measurement System Version A.02.00
Absolute Measurement Fundamentals
Changing the PTR
6
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