Agilent Technologies N5230A, Руководство по обслуживанию, Страница: 50 / 262

3-20 Service Guide N5230-90014
Tests and Adjustments PNA Series Microwave Network Analyzers
System Verification N5230A
Measurement Uncertainty
Measurement uncertainty is defined as the sum of:
• the residual systematic (repeatable) errors, and
• the random (non-repeatable) errors
in the measurement system after calibration.
The systematic errors are:
• directivity,
• source match,
• load match,
• reflection and transmission frequency tracking, and
• isolation (crosstalk).
The random errors include:
• noise,
• drift,
• connector repeatability, and
• test cable stability.
A complete description of system errors and how they affect measurements is provided in
the analyzer’s on-line embedded help.
Any measurement result is the vector sum of the actual test device response plus all error
terms. The precise effect of each error term depends on its magnitude and phase
relationship to the actual test device response. When the phase of an error response is not
known, phase is assumed to be worst-case (
−
180
°
to +180
°
). Random errors such as noise
and connector repeatability are generally combined in a root-sum-of-the-squares (RSS)
manner.