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N9069C Noise Figure Measurement Guide 29
Making Noise Figure Measurements
Making Frequency Converter Measurements
A system downconverter is part of the measurement system, and is present in
both the calibration setup and the measurement setup. See Figure 2-6 . During
calibration the noise performance of both the analyzer and the system
downconverter are measured. Because of this, when corrected measurements
are performed, the results then apply to the DUT only. If there are no more
frequency conversions in the DUT, ENR data for the same frequency range is
used for both calibration and measurements.
The analyzer can be used in much more complex systems, with multiple
frequency conversions between the DUT and the noise source. However, the
control of such systems is application-specific. You need to perform frequency
calculations to suit that particular system, account for the effects of any DSB
conversions, determine filter requirements, and calculate the appropriate ENR
values for calibration and the measurement.
To connect the analyzer and make your measurements:
Step Notes
1. Turn the analyzer on.
2. Press
MODE/MEAS
,
Noise Figure
,
OK,
Mode Preset
to return the analyzer to a
known state.
3. Enter the ENR values into the analyzer if
required.
See
“Entering Excess Noise Ratio (ENR) Data” on
page 64
for the procedures to do this.
4. Refer to “Setting up External LO Control”
on page 77 to set up the LO control for the
system downconverter and DUT as
required.
Note that you need to use an external LO control to control
another signal generator as the LO if the LO Freq Mode for
either DUT or the system downconverter is set to Swept.
5. Press
MEAS SETUP
,
DUT Setup &
Calibration
, and set the DUT Setup form
as required.
Refer to
“DUT Setup Form” on page 61
to see the
detailed information for each parameters in the DUT setup
form.
6. Press
MEAS SETUP
,
Avg/Hold Num
,
10
,
toggle
Averaging
to
On
.
Setting averaging here reduces jitter and provides more
accurate measurement results.
See
“Setting Averaging” on page 74
for more details.
7. Configure the measurement connection to
calibration setup as shown in
Figure 2-6
and press
MEAS SETUP
,
CALIBRATE
to
perform calibration.
8. Change the measurement connections to
the measurement setup as shown in
Figure
2-6
and make the corrected
measurements.