Keysight N9923A, User Manual, Page: 63 / 276

Keysight N9923-90001 User’s Guide
63
Time Domain – Option 010
Overview
Overview
In normal NA Mode operation, the FieldFox measures the characteristics of a
test device as a function of frequency. With Time Domain (opt 010), frequency
information is used to calculate the inverse Fourier transform and display
measurements with time on the horizontal display axis. The response values
appear separated in time, allowing a different perspective of the test device's
performance and limitations.
The graphic below compares the same cable reflection measurement data in
both the frequency and time domain. The cable has two bends. Each bend
creates a mismatch or change in the line impedance.
The frequency domain of an S11 measurement shows reflections caused by
mismatches in the cable. It is impossible to determine where the mismatches
physically occur in the cable.
The Time Domain response shows both the location and the magnitude of each
mismatch. The responses indicate that the second cable bend is the location of
a significant mismatch. This mismatch can be gated out, allowing you to view
the frequency domain response as if the mismatch were not present. Learn
more about gating in
“Gating” on page 72 .
Markers that are created on a Time Domain trace can be used to pinpoint the
distance of the mismatch from the reference plane.
For more information on Time Domain theory, see
http://literature.cdn.keysight.com/litweb/pdf/5989-5723EN.pdf