Technical data

24 User’s and Service Guide
87050A Option K22 Calibrating the Test System
Calibrating the Test System
After the test set has warmed up for at least two hours, you should calibrate the
instrument 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 will need to 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.
In the example setup shown in Figure 10, the following tests will be made:
• Return loss on the DUT's input and 2 output ports (A and B)
• Insertion loss (or gain) between the DUT's input and port A
• Insertion loss (or gain) between the DUT's input and port B
Figure 10 Calibrating the Test System
For the best accuracy, you should perform a full 2-port calibration between ports 1 and 3 on
the test set, and again between ports 1 and 5. As mentioned before, you need to 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 2-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 2-port calibration. Doing so
will render the calibration invalid.