Trace Settings; Line Loss And Velocity Factor; Data Chain - Keysight N9923A FieldFox User Manual

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
The following is an example showing how Line Loss works:
The DUT is a 100 meter transmission cable. The Line Loss value is .1 dB/meter. This
means that a signal traveling ONE WAY through the cable will lose 10 dB of power
(100 m * .1dB/m). Because the FieldFox performs this measurement with 1 port, the
test signal travels down the cable and then back, for a total loss of 20 dB.
For the purpose of illustrating this point, connect an OPEN to the end of the cable –
a maximum-sized fault - for 100% reflection of the 300 MHz test signal.
Without compensation for the loss of the cable, a –20 dB response would be visible
at 100 meters, which is the OPEN at the end of the DUT. This is from 10 dB of loss
through the cable in each direction.
With compensation for the loss using the manufacturer's specification, the FieldFox
compensates the trace as though the signal traveling through 100 meters was
increased by +20 dB. Therefore the response will show 0 dB for 100% reflection.

Data Chain

This setting, available only on the Table Settings, reverts to the default when the
FieldFox is Preset. Choose from the following:
 Standard – The normal FieldFox data processing chain. Transform calculations are
 8510 – The data processing chain used by the Keysight 8510 network analyzer.

Trace Settings

The following two settings apply to specific traces.
40
1. Window
2. Percent
3. Kaiser Beta
4. Impulse
Width
Velocity Factor is a property of the physical material of a cable. A VF of 1.0
o
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
o
is also directly proportional to the frequency of the signal that passes through
the cable.
performed AFTER error correction and trace math.
Transform calculations are performed BEFORE error correction and trace math.
Learn more at the FieldFox Supplemental Online Help website:
http://na.support.keysight.com/fieldfox/help/FieldFox.htm
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FieldFox User's Guide