Keysight N9923A, Руководство пользователя, Страница: 69 / 276

Keysight N9923-90001 User’s Guide
69
Time Domain – Option 010
Time Domain (Transform) Settings
Network Analyzer Windows Frequency Span and TDR Window
Selection for Step Rise Time (Approximated)
The following table shows the approximated relationship between the
frequency span and the window selection for impulse width and step rise time.
Refer to
Figure 4-1 on page 69
.
Figure 4-1 Network Analyzer TDR Rise Time
Line Loss and Velocity Factor
By default, the FieldFox does NOT correct Time Domain measurements to
account for the inherent loss of a cable. However, to make more accurate
measurements, Line Loss and Velocity Factor should be considered.
About Velocity Factor and Line Loss
— Velocity Factor is a property of the physical material of a cable. A VF of 1.0
corresponds to the speed of light in a vacuum, or the fastest VF possible. A
polyethylene dielectric cable has VF = 0.66 and a cable with PTFE dielectric
has VF = 0.7.
— Line Loss is specified in dB/m (or ft). In addition to the length of the cable,
loss is also directly proportional to the frequency of the signal that passes
through the cable.
The following is an example showing how Line Loss works:
Window Low-pass step
(10% to 90%)
Low-pass impulse Bandpass impulse
Minimum 0.45/ f span 0.60 / f span 1.20 / f span
Medium 0.99 / f span 0.98 / f span 1.95 / f span
Maximum 1.48 / f span 1.39 / f span 2.77 / f span