HP 85106D, Manual

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HP 85106D mm-Wave System 4-19
Service and Troubleshooting
Check Unratioed Power Levels
Check Unratioed Power Levels
This procedure allows you to check the output power level of each
sampler/mixer assembly, individually, and each associated IF amplifier.
The typical power level display (S11 as an example) is a ratio (in this case,
b
1
/a
1
). The network analyzer automatically applies power and phase locks to
a predefined port or ports to make the selected measurement. Ratioed
measurements provide useful data but they can mask certain malfunctions.
Assume, for example, that you need to measure the S-parameter at a specific
power level of a device. If the test set has a 20 dB power hole due to a faulty
RF input connector, that deficiency would be invisible (ratioed out) in a
ratioed measurement, however the data would be incorrect. It would not
have been taken at the specified power level. Similarly, troubleshooting
system faults using the ratioed measurement mode can be deceptive.
The solution is to separately test each channel and check the power in
unratioed mode. To do so requires specifying which port receives the driven
power, and which channel is phaselocked.
The following procedure includes steps to redefine parameters as required.
The power levels given are approximate. The assemblies that are parts of the
signal path of each channel are illustrated in Figure 4-7. Knowing which
assemblies are common to two, or all four channels, is a powerful
troubleshooting tool.
Figure 4-7 Simplified Signal Path of Unratioed Power Test