Determining Expected System Performance
Use the uncertainty equations, dynamic accuracy calculations in this appendix, and tables of
system performance values from the “Specifications and Measurement Uncertainties” chapter
in the
HP
87533
User’s
tiide
to calculate the expected system performance. The following
pages explain how to determine the residual errors of a particular system and combine them
to obtain total error-corrected residual uncertainty values, using worksheets provided. The
uncertainty graphs in the user’s guide are examples of the results that can be calculated using
this information.
Procedures
Use the measurement uncertainty worksheet to calculate the residual uncertainty in
transmission and reflection measurements. Determine the linear values of the residual error
terms and the nominal linear S-parameter data of the device under test as described below
and enter these values in the worksheets Then use the instructions and equations in the
worksheets to combine the residual errors for total system uncertainty performance. The
resulting total measurement uncertainty values have a confidence factor of 99.9%.
S-parameter
Values.
Convert the S-parameters of the test device to their absolute linear
terms.
Noise Floor and Crosstalk.
If a full
2-port
calibration is performed, the residual crosstalk
term can be ignored. Connect an impedance-matched load to each of the test ports and
measure
S21
or
S12.
Use the statistic function to measure the mean value of the trace. Use
this value plus one standard deviation as the noise floor value of your system.
Dynamic Accuracy.
Determine the absolute linear magnitude dynamic accuracy from the
dynamic accuracy graph on the previous page.
Other Error
‘l&ms.
Depending on the connector type in your system, refer to residual error
specifications in the “Specifications and Measurement Uncertainties” chapter in the
HP
87533
User’s
Guide,
and the “Characteristic values
‘Iable”
in this chapter to find the absolute linear
magnitude of the remaining error terms.
Combining Error
‘lbrms. Combine the above terms using the reflection or transmission
uncertainty equation in the worksheets.
Determining System Measurement Uncertainties
B-7
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