Technical data

85108L System Manual
Operation
High Power Measurements
3-36
View the Normalized Parameters
Use these traces to normalize the corrected data to the new levels after the attenuation is changed.
This example uses normalization only for S21 and S12. To view the corrected parameters:
1. Press
DISPLAY, DISPLAY: DATA.
2. Press
S11 and view the S11 measurement.
3. Press
S22 and view the S22 measurement.
4. Press
S21 and view the S21 measurement. If the thru is connected, the transmission coefficient
should be 1
∠0°.
5. Press
S12 SELECT DEFAULTS, DEFAULT to MEMORY:2
View the S12 measurement. If the thru is connected, the transmission coefficient should be
1
∠0°.
Normalization is turned off for the S11 and S22 measurements, then the appropriate memory is
selected and normalization is turned on to view S21 and S12.
Since these are accurate, repeatable attenuators, this sequence may be effective in your application.
If it is necessary to change other parts of the test setup, especially components connected to the test
ports or connected between the rear panel links, this procedure may require additional steps to
adequately compensate for the changes.
Selecting the Appropriate Measurement Calibration
Selecting appropriate measurement calibration signal levels available for calibration and for
measurement may also influence the decision of which error model to use for the measurement.
If appropriate signal levels can be achieved for all parameters during calibration and measurement,
the 8510 2-Port accuracy enhancement error model, either the 8510 Full 2-Port or TRL 2-Port,
provides best accuracy by providing best characterization and removal of the systematic errors in
the test setup. If the device is noninsertable, the 8510 adapter removal calibration procedure can be
implemented using the Full 2-Port and/or the TRL 2-Port calibration.
However, there are applications in which the 2-Port error model cannot be used. There are others in
which better results are produced using other calibration techniques described later. These are the
reasons that 2-Port correction cannot be used effectively:
• Very low signal levels of the S22 and S12 measurement will probably reduce the accuracy of the
S11 and S21 measurements.
Using 2-Port correction, the values of all four parameters are used to find the corrected value for
the displayed parameter. If, for example, the reverse parameters are not representative of their
actual values due to insufficient signal levels, then their contribution to the accuracy
enhancement algorithm will cause errors. This leads to noisy, nonrepeatable data for the other
parameters, even if their measured data is representative.
• Equipment external to the test set must be switched depending on the parameter being
measured.
There is no means of automatically switching equipment external to the test set depending on
the S-parameter being measured.
Using 2-Port correction, all four S-parameters are automatically selected in sequence, and there
is no signal available to indicate which parameter is being measured. If dynamic range
considerations make it necessary to change the test set configuration for measurement of
different parameters, the automatic switching used in the 2-Port error model cannot be used.