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6
Absolute Measurement Fundamentals
Changing the PTR
6-16
E5500 Phase Noise Measurement System Version A.02.00
As long as these qualifications are met, and the software does not
indicate any difficulty in establishing its calibration criteria, an
increase in PTR will not degrade the system's measurement
accuracy.
The following methods may be considered for increasing or
decreasing the PTR.
Voltage-Controlled-Oscillators
1
Select a different VCO source that has the tuning capabilities
needed for the measurement.
2
Increase the tune range of the VCO source.
CAUTION:
Be careful not to exceed the input voltage limitations of the Tune
Port on the VCO source.
NOTE: Increasing the tune range of the VCO is only valid as long as
the VCO source is able to continuously meet the previously
mentioned tuning qualifications.
Signal Generators
1
If you are using a signal generator with a calibrated 1 Vpk DC FM
Input (such as the Agilent 8640B, 8642A/B, 8656B, or 8662/3),
the Voltage tuning Range can be increased to 10 V as long as you
select Computed from the expected T. Constant in the Calibration
Process display. These signal generators continue to meet all of
the previously mentioned tuning qualifications across a 10V
tuning range.
2
Increase the signal generator's frequency deviation setting and
set the software to measure the new tuning constant or enter the
increased deviation if it is known. (Note that increasing the
deviation setting often increases the source's noise level as well.)
3
If you are using a synthesizer with Electronic-Frequency-Control
(EFC) capability such as the Agilent 8662A or Agilent 8663A, it is
possible to increase the tuning range of these sources using a
VCO as an external time base. When a compatible VCO source is
connected to the EXT INPUT on the Agilent 8662/3, the tuning
capability of the VCO source is transferred to the synthesizer.
Document Part No. E5500-90024 Ed. 1.0
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