Keysight Technologies N5221A

Keysight N5221A/22A Service Guide 8-9
General Purpose Maintenance Procedures
Error Terms
Directivity (E
DF
and E
DR
)
E
DF
and E
DR
are the uncorrected forward and reverse directivity error terms of
the system. The directivity error of the test port is determined by measuring the
S
11
and S
22
reflection of the calibration kit load. The load has a much better
return loss specification than does the uncorrected test port. Therefore, any
power detected from this measurement is assumed to be from directivity error.
The measurements most affected by directivity errors are measurements of low
reflection devices.
Typical Cause of Failure
The calibration kit load is the most common cause of directivity specification
failure.
If the load has been gaged and its performance independently verified, suspect
the analyzer test port coupler.
To troubleshoot, refer to “Checking the Signal Separation Group” on
page 4-39.
Source Match (E
SF
and E
SR
)
E
SF
and E
SR
are the forward and reverse uncorrected source match terms of
the driven port. They are obtained by measuring the reflection (S
11
, S
22
) of an
open, and a short that are connected directly to the ports. Source match is a
measure of the match of the coupler, as well as the match between all
components from the source to the output port.
The measurements most affected by source match errors are reflection and
transmission measurements of highly reflective DUTs.
Typical Cause of Failure
The calibration kit open or short is the most common cause of source match
specification failure.
If the open or short performance has been independently verified, then suspect
the analyzer switch splitter, step attenuator, or coupler.
To troubleshoot, refer to “Checking the Signal Separation Group” on
page 4-39.
Load Match (E
LF
and E
LR
)
Load match is a measure of the impedance match of the test port that
terminates the output of a 2-port device. The match of test port cables is
included in this response. Load match error terms are characterized by
measuring the S
11
and S
22
responses of a “thru” configuration during the
calibration procedure.