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6
Absolute Measurement Fundamentals
Selecting a Reference
Using a Signal
Generator
Tuning
Requirements
Table 6-2
Tuning Characteristics of Various VCO Source Options
VCO Source
Carrier
Freq.
Agilent 8662/3A
υ
EFC
0
DCFM
Agilent 8642A/B
Agilent 8644B
6-10
E5500 Phase Noise Measurement System Version A.02.00
If only one device is available in addition to the UUT, you can
perform the Phase Noise Using a Phase Locked Loop Measurement
using these two devices and know that the noise level of each of the
devices is at least as good as the measured results. (The measured
results will represent the sum of the noise of both devices.)
When using a signal generator as a reference source, it is important
that the generator's noise characteristics are adequate for measuring
your device.
Often the reference source you select will also serve as the VCO
source for the PLL measurement. (The VCO source can be either the
unit-under-test (UUT) or the reference source.) To configure a PLL
measurement, you will need to know the following tuning
information about the VCO source you are using.
G
Tuning Constant (Hz/V) (within a factor of 2)
G
Tuning Voltage Range (V)
G
Center Voltage of Tuning Range (V)
G
Input Resistance of Tuning Port (ohms)
The primary consideration when evaluating a potential VCO source
for your measurement is whether it will provide 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
information will help you evaluate your VCO source based on the
estimated drift of your sources.)
Table 6-2
lists the tuning parameters for several VCO options.
Tuning Constant
Center
(Hz/V)
Voltage
(V)
5 E – 9 x υ
0
0
FM Deviation
0
FM Deviation
0
FM Deviation
0
Table
Voltage Tuning
Input
±
Range (
V)
Resistance
Ω)
(
10
1E + 6
10
1 k (8662)
600 (8663)
10
600
10
600
Document Part No. E5500-90024 Ed. 1.0
6-2. This
Tuning
Calibration
Method
Measure
Calculate
Calculate
Calculate
Calculate
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