User`s guide

Absolute Measurement Fundamentals 5
Agilent E5505A User’s Guide 107
The system’s peak tuning range is derived from the tuning characteristics of
the VCO source you are using for the measurement. Figure 71 illustrates the
relationship that typically exists between the VCO’s peak-to-peak tuning range
and the tuning range of the system.
The system’s drift tracking range is limited to a small portion of the peak
tuning range to minimize the possibility of measurement accuracy degradation
caused by non-linearity across the VCO’s tuning range.
Peak tune range (PTR)
PTR is determined using two parameters:
• VCO tuning sensitivity (Hz/Volt)
• Total voltage tuning range (Volts)
PTR = (VCO Tuning Sensitivity) X (Total Voltage Tuning Range)
PTR = (100 Hz/V) X (10 V) = 1000 Hz
As an Example:
A Peak Tuning Range of 1000 Hz provides the following ranges:
Capture Range = 0.05 X 1000 Hz = 50 Hz
Drift Tracking Range = 0.24 X 1000 Hz = 240 Hz
Tuning requirements
The peak tuning range required for your measurement depends on the
frequency stability of the two sources you are using. The signals from the two
sources are mixed in the system’s phase detector to create a beatnote. In order
for the loop to acquire lock, the center frequencies of the sources must be close
Figure 71 Capture and drift-tracking range with tuning range of VCO
Total peak-to-peak tuning range of VCO
System
peak tuning range
Drift
tracking range
Capture
range
VCO Source center frequency
24% 24%
5% 5%
E5505a_capt_drift_trk_range
26 Feb 04 rev 1