HP 85108, Системное руководство

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Controlling the A ttenuators. Set the step attenuators as follows.
Press 4 STIMULUS MENU 5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
POWER MENU
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
ATTENUATOR PORT: 1 or
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
ATTENUATOR PORT: 2 .
Use the knob, STEP k eys, or n umeric en try to set the attenuator from 0 dB to 90 dB in 10
dB steps. F amiliarize y ourself with op eration of the step attenuators b y measuring the user
parameters.
Measure User P arameters and Set A ttenuators. In order to maintain sp ecied p erformance,
the IF signal lev els are less than 010 dBm as measured b y the user parameters. Connect an
appropriate device at P ort 1 or P ort 2 for eac h measuremen t, turn on a measuremen t marker,
then measure the user parameters in order to v erify the IF signal lev els as follo ws.
1.
Press 4
P ARAMETER MENU
5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNN
USER 1 a1 and observ e the IF signal lev el in the LOG MA G
format.
2. Press
NNNNNNNNNNNNNNNNNNNNNNNNNNNNN
USER 4 b1 and observ e the IF signal lev el. If either a1 or b1 is greater than 010
dBm at an y p oint in the trace, increase the A TTENUA TOR POR T: 1 v alue.
3.
Press
NNNNNNNNNNNNNNNNNNNNNNNNNNNNN
USER 3 a2 .
4.
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
REDEFINE PARAMETER
NNNNNNNNNNNNNNNNN
DRIVE
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
DRIVE: PORT 2 .
Observ e the IF signal lev el.
5.
Press
NNNNNNNNNNNNNNNNNNNNNNNNNNNNN
USER 2 b2 and observ e the IF signal lev el. This sho ws the lev el with the signal
applied to P ort 1. If either a2 or b2 is greater than 010 dBm at an y p oint in the trace,
increase the
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
ATTENUATOR PORT: 2 v alue.
In some applications it may b e necessary to measure the signal at b2 with the signal
applied to P ort 2. F or this measuremen t:
6.
Press
NNNNNNNNNNNNNNNNNNNNNNNNNNNNN
USER 2 b2 .
7.
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
REDEFINE PARAMETER
NNNNNNNNNNNNNNNNN
DRIVE
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
DRIVE: PORT 2 .
Observ e the IF signal lev el.
Before calibration, measure these user parameters with the calibration standards, then with
the device under test connected and op erating.
Generally , set the attenuators to obtain the maximum p ossible mixer input signal lev el
(less than 010 dBm) with the device connected and op erating. This will pro vide the b est
signal-to-noise ratio for the measuremen t. Then remov e the device and p erform measuremen t
calibration. F or b est accuracy , do not c hange either attenuator b et w een calibration and
measuremen t.
Changing Signal P ath After Calibration
If an y attenuator or other external equipmen t is c hanged after calibration, the measuremen t
results cannot b e sp ecied except b y y our o wn estimation of the error con tribution of
the c hange. F or example, when the p ort attenuation is c hanged with correction On, the
CAUTION: CORRECTION MAY BE INVALID is display ed. The op erator m ust judge whether the
error is tolerable in the particular application and ho w to comp ensate for the c hange.
The only reason to c hange the in ternal attenuators or external equipmen t b et w een calibration
and measuremen t is to maximize the lev els under b oth conditions, th us minimizing
uncertain t y due to noise. Many factors will en ter in to the decision of whether it is more
Operation 3-33