Why And When To Calibrate; Definitions - Keysight N9912A User Manual

Calibration for NA, CAT, and VVM Modes

Why and When to Calibrate

Why and When to Calibrate
There are well-defined and understood systematic errors that are measured
and calculated during the calibration process. These errors are caused by
leakage signals inside the FieldFox, by the frequency response of the FieldFox
receivers, and by reflections inside the FieldFox that interact with the DUT.
After calibration, these errors are removed from subsequent measurements.
To maintain highest measurement accuracy, perform a new calibration when
any of the following changes occur:
— When any of the following measurement settings change: Frequency
Range, Power Level, and Resolution. Therefore, make these measurement
settings before calibrating. Increased Averaging and higher Resolution
cause slower sweeps and slower calibration times. Learn about
Interpolation and Questionable Accuracy in
— When the FieldFox temperature changes more than about 10°F (5°C). Learn
more in
— When the connection to the DUT changes, requiring a different jumper
cable or adapter.

Definitions

DUT (Device Under Test) The cable, antenna, transmission line, or anything
else that is connected to the FieldFox that is to be measured.
Calibration Standards - OPEN, SHORT, LOAD, and THRU
— OPEN, SHORT, and LOAD are calibration standards. These are precision
components that are used during calibration and to terminate a DUT during
some measurements. When an RF signal 'hits' these components, the
signals are reflected in a predictable manner.
Calibration Reference Plane is the point at which cal standards are connected
during a calibration. This can be either the FieldFox RF OUT connector, or at
the end of a jumper cable or adapter.
7- 2
"How to monitor the internal FieldFox temperature:" on page
— SHORT and OPEN standards both cause 100% of an RF signal to be
reflected. The difference between these two standards is what
happens to the phase of the reflected signal, which is beyond the
scope of this discussion. Although an OPEN standard is a precision
component, simply leaving nothing connected at the end of a cable
can be a reasonable substitute for an OPEN.
— A LOAD standard absorbs almost ALL of the incident signal and very
little signal is reflected back to the source.
page 7-7.
Keysight N9912-90001 User's Guide
2-4.