Agilent Technologies 8753ES Option 011 Service Manual page 284

Accessories Troubleshooting
Inspect the Error Terms
If you detect problems using error term analysis, use the following approach to isolate the
fault:
1. Check the cable by examining the load match and transmission tracking terms. If those
terms are incorrect, go to
2. Verify the calibration kit devices:
• Loads: If the directivity error term looks good, the load and the test port are good. If
directivity looks bad, connect the same load on the other test port and measure its
directivity. If the second port looks bad, as if the problem had shifted with the load,
replace the load. If the second port looks good, as if the load had not been the
problem, troubleshoot the first port.
• Shorts and opens: If the source match and reflection tracking terms look good, the
shorts and the opens are good. If these terms look bad while the rest of the terms
look good, proceed to
Cable Test
The load match error term is a good indicator of cable problems. You can further verify a
faulty cable by measuring the reflection of the cable. Perform an S11 1-port calibration
directly at port 1 (no cables). Then connect the suspect cable to port 1 and terminate the
open end in 50 ohms.
Figure 9-1 shows the return loss trace of a good (left side) and faulty cable. Note that the
important characteristic of a cable trace is its level (the good cable trace is much lower) not
its regularity. Refer to the cable manual for return loss specifications.
Figure 9-1 Typical Return Loss Traces of Good and Poor Cables
9-6
"Cable Test" on page
"Verify Shorts and Opens" on page
9-6.
9-7.
Chapter 9