76 Keysight N9927-90001 User’s Guide
TDR (Time Domain Reflectometry) - Option 215
TDR Measurement Settings
—Press Sweep 3
—Then TDR Sweep
— Choose one of the following:
— Auto
Low pass frequency settings are calculated based on the
current number of points. The Stop Frequency and Resolution
settings can be changed to any value.
——To set Stop Frequency, press Meas 4
, then Settings, then
scroll to Auto: Max Freq.
——To set Resolution, press Sweep 3
, then Resolution.
— Cable
Provides a higher resolution measurement. Use when
under-sampling is suspected. The Stop Frequency is limited to 500
MHz maximum. The Resolution is fixed to 1601.
Frequency Mode
All TDR measurements are made with frequency settings and, using Inverse
Fourier Transform (IFT), the time and distance to faults are calculated.
How to set Frequency Mode
With a TDR measurement present,
—Press Meas Setup 4
—Then Freq Mode
— Choose one of the following:
— Lowpass
The frequency range of a TDR measurement is set
automatically based on the Start and Stop Distances. Use Lowpass
mode when the DUT is a cable ONLY.
— Bandpass
This setting changes the measurement to DTF. Bandpass
is NOT ALLOWED with TDR because the DC component is required
for TDR measurements.
Because of its greater measurement accuracy, Cable is the default setting
in CPU1 units with firmware A.08.18 and greater and CPU2 units with
firmware A.09.57 and greater. Refer to “Preferences” on page 515.
The start and stop frequencies for the measurement are always annotated
on the screen below the start and stop distances.
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