User`s guide

Absolute Measurement Fundamentals 5
Agilent E5505A User’s Guide 113
Using a Signal Generator
When using a signal generator as a reference source, it is important that the
generator’s noise characteristics are adequate for measuring your device.
Tuning Requirements
Often the reference source you select also serves as the VCO source for the PLL
measurement. (The VCO source can be either the DUT or the reference source.)
To configure a PLL measurement, you need to know the following tuning
information about the VCO source you are using.
• Tuning Constant (Hz/V) (within a factor of 2)
• Tuning Voltage Range (V)
• Center Voltage of Tuning Range (V)
• Input Resistance of Tuning Port (
Ω )
The primary consideration when evaluating a potential VCO source for your
measurement is whether it provides the test system with sufficient capture
and drift tracking ranges to maintain lock throughout the measurement. To
make this determination, you must estimate what the drift range of the
sources you are using will be over the measurement period (thirty minutes
maximum). (Details on the relationship between the capture and drift tracking
ranges and the tuning range of the VCO source are provided in Table 12. This
information helps you evaluate your VCO source based on the estimated drift
of your sources.)
Table 12 lists the tuning parameters for several VCO options.
Table 12 Tuning Characteristics of Various VCO Source Options
VCO Source Carrier
Freq.
Tuning Constant
(Hz/V)
Center
Voltage
(V)
Voltage Tuning
Range (
± V)
Input
Resistance
(
Ω)
Tuning
Calibration
Method
Agilent 8662/3A
EFC
DCFM
υ
0
5 E – 9 x υ
0
FM Deviation
0
0
10
10
1E + 6
1 k (8662)
600 (8663)
Measure
Calculate
Calculate
Agilent 8642A/B FM Deviation 0 10 600 Calculate
Agilent 8644B FM Deviation 0 10 600 Calculate