User`s guide

Agilent Technologies E5500 Phase Noise Measurement System 8-7
Residual Measurement Fundamentals
Calibrating the Measurement
The attenuation of the source noise is a function of the carrier offset
frequency, and the delay time
(τ ) and is equal to:
b. The source should also have a good broadband phase noise floor
because at sufficiently large carrier offsets it will tend to decorrelate
when measuring components with large delays. At , source
noise is rejected completely. the first null in noise can be used to
determine the delay difference. At , source noise shows
up unattenuated. At lower offsets, source noise is attenuated at
20 dB per decade rate at.1 of , source noise is attenuated 20 dB.
Examples of sources which best meet these requirements are the
Agilent/HP 8644B and Agilent/HP 8642A/B.
The source used for making residual phase noise measurements must be low
in AM noise because source AM noise can cause AM to
ΦM conversion in
the UUT
.
Mixer-type phase detectors only provide about 20 to 30 dB of rejection to
AM noise in a
ΦM noise measurement so the AM noise can appear in the
phase noise plot
.
2. It is very important that all components in the test setup be well shielded
from RFI. Unwanted RF coupling between components will make a
measurement setup very vulnerable to external electric fields around it.
The result may well be a setup going out of quadrature simply by people
moving around in the test setup area and altering surrounding electric
fields. A loss of quadrature stops the measurement.
3. When making low-level measurements, the best results will be obtained
from uncluttered setups. Soft foam rubber is very useful for isolating the
UUT and other phase-sensitive components from mechanically-induced
phase noise. The mechanical shock of bumping the test set or kicking
the table will often knock a sensitive residual phase noise measurement
out of quadrature.
f
1
τ
---
=
f
1
2
πτ
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=
1
2
πτ
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