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4
Expanding Your Measurement Experience
Zero beating sources... The center frequencies of the sources are now
adjusted, if necessary, to position the beatnote within the 5% range. The
adjustment is made with the tune voltage applied to the VCO source set at its
nominal or center position.
Measuring the VCO Tuning Constant... The tuning sensitivity (Hz/V) of the VCO
source is now precisely determined by measuring the beatnote frequency at
four tune voltage settings across the tuning range of the VCO source. Linearity
across the tuning range is also verified
Measuring the Phase Detector Constant... The transfer characteristics (V/rad)
of the test set's phase detector are now determined for the specific center
frequency and power level of the sources being measured.
Measuring PLL suppression... The required correction data is created to
compensate for the phase noise suppression which occurs within the
bandwidth of the phase lock loop created for this measurement. The computer
displays the PLL suppression curve and associated measurement values.
Sweep segments
When the system begins measuring noise, it places the noise graph on its
display. As you watch the graph, you see the system plot its measurement
results in frequency segments.
The system measures the noise level across its frequency offset range by
averaging the noise within smaller frequency segments. This technique enables
the system to optimize measurement speed while providing you with the
measurement resolution needed for most test applications.
When the measurement is complete, refer to
Measurement Results" for help in evaluating your measurement results. (If the
test system has problems completing the measurement, it informs you by a
message on the computer display.
Checking the beatnote
While the Connect Diagram is still displayed, Agilent recommends that you use
an oscilloscope (connected to the Monitor port on the test set) or a counter to
check the beatnote being created between the reference source and your DUT.
The objective of checking the beatnote is to ensure that the center frequencies
of the two sources are close enough in frequency to create a beatnote that is
within the Capture Range of the system.
The phase lock loop (PLL) Capture Range is 5% of the peak tuning range of the
VCO source you are using. (The peak tuning range for your VCO can be
estimated by multiplying the VCO tuning constant by the tune range of VCO.
90
Chapter
14, "Evaluating Your
Agilent E5505A User's Guide
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