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Vector Network Analyzer
R&S
®
FPC
173
User Manual 1178.4130.02 ─ 07
If the cable loss is constant over a large span (for example for low center frequencies),
you can select any span.
Note that if the cable loss is greater than 20
dB, you are better off using the S21 mea-
surement, because the cable loss measurement might yield invalid results.
Measuring the cable loss
1. Connect the DUT to the R&S
FPC as shown in
Make sure not to terminate the cable.
2. Define the frequency parameters for the measurement.
For more information, see
Chapter 18.2, "Frequency Configuration"
3. Press the "Meas" key to enter the measurement menu.
4. Select the "Reflection S11" menu item to start the measurement.
5. Calibrate the cable loss measurement.
For more information, see
6. After calibration, start the actual measurement (single sweep or continuous
sweep).
18.1.4
Distance to Fault Measurement
Access
: "Meas" > "Distance-To-Fault"
The distance to fault (DTF) measurement determines the exact location of possible
faults in a transmission system. If you connect the end of the cable to the R&S
FPC,
the DTF measurement shows you the exact distance to the fault (in meter or feet),
regardless of the reason of the fault. Typical defects in a cable could be, for example, a
broken cable, partial reflections, a loose cable connector or cable corrosion.
In addition, the measurement shows the degree of the fault in dB. From this informa-
tion, you can determine the component that has the fault and its seriousness.
Cable
R&S FPC
Port 1
(RF Out)
50 Ohm
Figure 18-4: Setup of a DTF measurement
To determine the distance to a cable fault, the R&S
FPC measures the reflections of
the cable under test in the frequency domain. The R&S
FPC first determines the mag-
nitude of the reflections for a particular frequency by comparing the phase of the reflec-
ted signal and a reference signal created by the tracking generator. It then performs
inverse fast fourier transformation (IFFT) on the signal that has been received. In com-
bination with the characteristics of the cable model, the R&S
FPC is able to determine
the distance the reflections have been traveling.
Measurements and Result Displays