7-10
Operating Concepts
Output Power
NOTE After measurement calibration, you can change the p ower within a range and
still maintain nearly full accuracy. In some cases better accuracy can be
achieved by changing the power within a range. It can be useful to set
different power levels for calibration and measurement to minimize the
effects of sampler compression or noise floor.
If you decide to switch power ranges, the calibration accuracy is degraded and
accuracy is no longer specified. However, the analyzer leaves the correction
on.
The annotation C∆ will be displayed whenever you change the power after
calibration.
Power Coupling Options There are two methods you can use to couple and uncouple power levels with the analyzer:
• channel coupling
• port coupli ng
By uncoupling the channel powers, you effectively have two separate sources. Uncoupling
the test ports allows you to have different power levels on each port.
Channel coupling
toggles between coupled and uncoupled channel power. With the
channel power coupled, the power levels are the same on each channel. With the channel
power uncoupled, you can set different power levels for each channel. For the channel
power to be uncoupled, the other channel stimulus functions must also be uncoupled
().
Test port coupling
toggles between coupled and uncoupled test ports. With the test
ports coupled, the power level is the same at each port. With the ports uncoupled, you can
set a different power level at each port. This can be useful, for example, if you want to
simultaneously perform a gain and reverse isolation measurement on a high-gain
amplifier using the dual channel mode to display the results. In this case, you would want
the power in the forward direction (S21) much lower than the power in the reverse
direction (S12).
CH PWR [COUPLED]
COUPLED CH OFF
PORT PWR [COUPLED]