5 CALIBRATION AND CALIBRATION KIT
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5.1.2 Systematic Errors
The systematic measurement errors of vector network analyzers are subdivided into the
following categories according to their source:
§Directivity;
§Source match;
§Load match;
§Isolation;
§Reflection/transmission tracking.
The measurement results before the procedure of error correction has been executed are
called uncorrected.
The residual values of the measurement results after the procedure of error correction
are called effective.
5.1.2.1 Directivity Error
A directivity error (Ed) is caused by incomplete separation of the incident signal from
the reflected signal by the directional coupler in the source port. In this case part of the
incident signal energy comes to the receiver of the reflected signal. Directivity errors do
not depend on the characteristics of the DUT and usually have stronger effect in
reflection measurements.
5.1.2.2 Source Match Error
A source match error (Es) is caused by the mismatch between the source port and the
input of the DUT. In this case part of the signal reflected by the DUT reflects at the
source port and again comes into the input of the DUT. The error occurs both in
reflection measurement and in transmission measurement. Source match errors depend
on the relation between input impedance of the DUT and test port impedance when
switched as a signal source.
Source match errors have strong effect in measurements of a DUT with poor input
matching.
5.1.2.3 Load Match Error
A load match error (El) is caused by the mismatch between the receiver port and the
output of the DUT. In this case part of the signal transmitted through the DUT reflects
at the receiver port and comes to the output of the DUT. The error occurs in
transmission measurements and in reflection measurements (for a 2-port DUT). Load
match errors depend on the relation between output impedance of the DUT and test port
impedance switched as a signal receiver.
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