Measuring phase noise, Measuring phase noise -35 – Agilent Technologies E4438C User Manual
Page 83
Performance Tests
Phase Noise and Residual FM (Manual Test - Option UNJ or Option 506 Only)
3- 35
Phase Noise and Residual FM
(Manual Test - Option UNJ or Option 506 Only)
The signal generator’s automated performance tests do not include a test for either phase noise or residual
FM. These tests must be done separately and the results attached to the test results obtained with the
Service Support Software. Either output a plot for each measured frequency, or the results of this test can be
recorded using the
“Agilent E4438C ESG Option UNJ Vector Signal Generator Phase Noise and Residual FM
Performance Test Record” on page 3-43
Measure phase noise and residual FM on an Agilent E5500 Series phase noise measurement system or its
equivalent, at 0.5, 1, 2, 3, and 4 GHz as applicable to the model under test.
Measuring Phase Noise
Because of the excellent phase noise performance of signal generators with Option UNJ, a special procedure
with extensive equipment is required. The recommended method is to use an Agilent E5500 Series phase
noise measurement system. This system is recommended over the older Agilent 3048 phase noise system due
to speed issues and the fact that the older system can not directly measure residual FM. Most of the rest of
this discussion refers to the Agilent E5500 Series phase noise measurement system, although the principles
apply to both.
The limitation of any measurement of phase noise is that the resulting measurement can never be better than
the phase noise of the source used to down-convert the signal. In an Agilent E5500 Series phase noise
measurement system, this source is typically either an Agilent 8644B high-performance RF signal generator
or an Agilent 8662A/8663A high-performance RF signal generator. Both have advantages and disadvantages.
The Agilent 8644B high-performance RF signal generator has better phase noise above 10 kHz from the
carrier, while the Agilent 8662A/8663A high-performance RF signal generator has better close-in phase noise,
but is worse above 10 kHz. Other sources may have different characteristics. To fully characterize a signal
generator to a high degree of accuracy, both sources may be needed.
The following sections illustrate two different measurements of the same device under test (DUT):
•
“Using an Agilent 8662A/8663A high-performance RF signal generator” on page 36
•