User`s guide

User’s and Service Guide 25
87050A Option K24 Operation
Calibrating the Test System
After the test set has warmed up for at least two hours, you should calibrate before making
any measurements. Refer to your network analyzer user’s guide to determine the type of
calibration appropriate for the measurements you will be making.
You must calibrate each measurement path separately and store the calibration as an
instrument state in the network analyzer. Refer to your network analyzer user’s guide for
information on how to calibrate and store instrument states.
Refer to Figure 11. In this example setup the following tests will be made:
• Return loss on the DUT input and 2 output ports (A and B)
• Insertion loss (or gain) between the DUT input and port A
• Insertion loss (or gain) between the DUT input and port B
Figure 11 Calibrating the Test System
For the best accuracy, you should perform a full two-port calibration between test set ports
1 and 2, and again between ports 1 and 3. As mentioned before, you must save the
calibrations as instrument states. See your analyzer user’s guide for information on
calibrations and saving instrument states.
CAUTION When performing a full two-port calibration and making subsequent
measurements, you must use the transfer switch internal to the 8720D to
change the RF signal path direction. Do not use the test set to change the RF
signal path direction when you are using a full two-port calibration. Doing so
will render the calibration invalid.