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6-2 ET User’s Guide
Calibrating for Increased Measurement Accuracy
Introduction
Introduction
This chapter first explains measurement calibration in the section titled
“Measurement Calibration Overview.” The sections following the
overview provide instructions for choosing, performing, saving, and
checking measurement calibrations.
Each example measurement in Chapter 3, “Making Measurements,”
provides an example calibration for the particular type of measurement.
Measurement Calibration Overview
Measurement calibration is a process that improves measurement
accuracy by using error correction arrays to compensate for systematic
measurement errors. Measurement calibration is also called cal,
accuracy enhancement, and error correction. Measurement errors are
classified as random, drift, and systematic errors. Random errors, such
as noise and connector repeatability, are non-repeatable and not
correctable by measurement calibration. Drift errors, such as frequency
and temperature drift, occur after a calibration has been performed and
can only be removed by doing another calibration.
Systematic errors, such as tracking and mismatch, are the most
significant errors in most RF measurements. Fortunately, systematic
errors are repeatable and for the most part correctable, though small
residual errors may remain. In brief, systematic errors are correctable.
Repeatable systematic errors are due to the frequency response of the
receivers, leakage between the signal paths, and signal reflections due to
mismatch in the test setup.