Rohde & Schwarz FSH4, Руководство по эксплуатации

Страница: 157 / 250

R&S FSH Network Analyzer Mode
Evaluating the Results
Operating Manual 1309.6275.12 - 14 138
Electrical length
Shows the electrical length of a DUT.
The electrical length is a numerical result that displayed in addition to another
measurement format. As long as it is active, the electrical length is displayed
regardless of the currently selected format.
The electrical length is calculated from the phase delay.
f
=
2
with being the phase deviation over the entire frequency range. The electrical
length is then derived by
0
c l
=
with
0
c being the velocity of light.
By definition, the electrical length is calculated from the vacuum velocity of light and
the differential group delay (
g
). Here, the group delay is replaced by the phase delay
for two reasons:
C An electrical length needs to be specified only for non-dispersive DUTs in which
phase delay and group delay match.
C Due to the significantly wider aperture, the measurement certainty is an order of
magnitude higher in the phase delay measurement than in the group delay
measurement.
The result for the electrical length is correct only if the phase difference between two
adjacent test points does not exceed 180°.
Available for vector measurements.
Delay time
Shows the delay time of a cable.
The delay time is a numerical result that is displayed in addition to another
measurement format.
The delay time is the propagation time of the wave or the time it takes the wave to
reach its destination..
Available for the vector phase measurements.
4.4.1.1 Working with the Smith Chart
If you are displaying measurement results in a Smith chart (available for vector
reflection measurements), the R&S FSH provides several special functionality.
M Press the MEAS key.
M Press the "Measurement Format" softkey.
M Select the "Smith Chart" menu item.
The R&S FSH shows the reflection of the DUT in the Smith chart.