HP 70427A User Manual page 110

Millimeter Phase Noise Measurement - User Control
Tune Voltage: select the instrument that will be tuned, unless the
downconverter is being tuned. If the downconverter is being tuned,
select one of the sources. With phase noise using a phase-lock-loop
selected as the measurement type, the software requires that something
be designated as the tuned device. However, downconverter is not one of
the available choices in A.02 or earlier software. This only affects the
connection diagram and does not change the measurement or the results.
Step 9 - Start a new measurement
Connect the sources when the software pauses at the connection diagram.
Set the reference source output as follows:
Frequency: ..................................................Same as downconverter's IF
Amplitude: ............................................................................... +16 dBm
Step 10 - Adjust mixer bias if necessary
If mixer bias was enabled in step 4, adjust the mixer bias current for
maximum signal level from the harmonic mixer as measured at the
downconverter's IF output.
1. Connect a spectrum analyzer to monitor the downconverter's IF.
a. Connect a spectrum analyzer to monitor the downconverter's RF
ANALYZER output.
b. Press the
Amplitudes
c. Press the
VIEW IN | IF| -
2. Set the downconverter's IF gain to 0 dB. This is to insure that the IF
amplifier won't be driven into compression.
a. Press the
Amplitudes
b. Press the
more 1 of 2
c. Press the
IF GAIN
d. Enter 0 with the numeric keypad.
e. Press the softkey.
dB
3. If the DUT's output power is adjustable, set it for a harmonic mixer
input level that is just below the point where the signal starts being
compressed (as measured by the RF spectrum analyzer).
4. Adjust mixer bias for a maximum IF signal measured by the
spectrum analyzer.
a. Press the softkey.
Freqs
b. Press the
MIXER BIAS
softkey.
softkey until IF is underlined.
softkey.
softkey.
softkey.
softkey.
HP 70427A/HP 70428A User's Guide 3-11
Downconverter Operation