Technical data

85108L System Manual
Operation
High Power Measurements
3-34
Using the Port 1 and Port 2 Attenuators
Use the Port 1 and Port 2 step attenuators to adjust the signal level into the mixers and thus protect
the mixers from excessively high signal levels. Note that the attenuators do not change the Port 1 or
Port 2 signal levels.
Controlling the Attenuators
Set the step attenuators as follows:
Press
STIMULUS MENU [POWER MENU] [ATTENUATOR PORT: 1] or [ATTENUATOR PORT: 2].
Use the knob, STEP keys, or numeric entry to set the attenuator from 0 dB to 70 dB in 10 dB steps.
Familiarize yourself with operation of the step attenuators by measuring the user parameters
Measure User Parameters and Set Attenuators. In order to maintain specified performance, the IF
signal levels are less than −10 dBm as measured by the user parameters. Connect an appropriate
device at Port 1 or Port 2 for each measurement, turn on a measurement marker, then measure the
user parameters in order to verify the IF signal levels as follows:
1. Press
PARAMETER MENU, then [USER 1 a1] and observe the IF signal level in the LOG MAG
format.
2. Press
[USER 4 b1] and observe the IF signal level. If either a1 or b1 is greater than −10 dBm at
any point in the trace, increase the ATTENUATOR PORT: 1 value.
3. Press
[USER 3 a2].
4. Press
[REDEFINE PARAMETER] [DRIVE] [DRIVE: PORT 2] [REDEFINE DONE]. Observe the IF signal
level
5. Press
[USER 2 b2] and observe the IF signal level. This shows the level with the signal applied to
Port 1. If either a2 or b2 is greater than −10 dBm at any point in the trace, increase the
ATTENUATOR PORT: 2 value.
In some applications it may be necessary to measure the signal at b2 with the signal applied to
Port 2. For this measurement:
a. Press
[USER 2 b2].
b. Press
[REDEFINE PARAMETER] [DRIVE] [DRIVE: PORT 2] [REDEFINE DONE]. Observe the IF
signal level.
Before you perform a calibration, measure these user parameters with the calibration standards
connected, then with the device under test connected and operating.
Generally, set the attenuators to obtain the maximum possible mixer input signal level (less than
−10 dBm) with the device connected and operating. This will provide the best signal-to-noise ratio
for the measurement. Then remove the device and perform measurement calibration. For best
accuracy, do not change either attenuator between calibration and measurement.