Rohde&Schwarz R&S®ZVL Application Sheets Application Sheet

&S ZVL Distance-to-Fault Measurements

R

Preparing a Distance-to-Fault Measurement

Distance-to-Fault Measurements

With option ZVL-K2, “Distance-to-Fault”, the analyzer can locate faults and
discontinuities on cables and transmission lines. The faults produce spikes on the
trace; the x-axis shows the distance from the calibrated reference plane. Most
conveniently the reference plane is set to the analyzer test port PORT 2.

Preparing a Distance-to-Fault Measurement

Consider two RG141A cables of different length. The first cable can be connected to
PORT 2 of the analyzer using a suitable adapter. The second cable is connected to the
first cable using a second adapter and either left open or terminated with a matched
load. The first cable contains a fault which is to be located by the network analyzer.
The lengths of the cables and adapters are shown below.

To prepare the distance-to-fault measurement, first perform a full one-port calibration
at PORT 2:

1. Press the “Preset” key to restore standard analyzer settings, in particular a linear
frequency sweep with a relatively wide sweep range and a sufficiently large
number of points.

2. Click “Trace – Meas – Distance-to-Fault” to switch on the distance-to-fault
measurement, display the distance scale and select S22 as measured quantity.

3. Click “Trace – Meas – Distance-to-Fault – Full One-Port P2 Cal...” to open the
calibration wizard and perform a full one-port calibration at the analyzer test port.
Proceed as described in the analyzer’s help system, connecting the required
Open, Short, and Match standards directly to PORT 2.

4. Click “Cable Type” to open the “Cable Type” dialog. In the list of cables, select your
cable type (RG 141A). Press “OK” to close the dialog.

5. Adjust the “Stop Distance” to 3 m, according to the dimensions of your cables
(approx. twice the total length in order to view multiple reflections).

6. Observe the measurement result in the diagram area (see “Analysis of Distance­to-Fault Results” below). If desired, vary the diagram scale (“Trace – Scale...”).

AS 1ZKD-6 – 01, M. Jetter, 12/2007 1

&S ZVL Distance-to-Fault Measurements

R

Analysis of Distance-to-Fault Results

ifferent cable types

D

If the second cable is of different type, you can still correctly locate the fault on the first
cable using the described settings. If your cable type is not in the list, you can easily
add your own cable type with arbitrary properties.

Analysis of Distance-to-Fault Results

The position of the spikes indicating faults and discontinuities is most easily monitored
using markers which are placed onto the peaks of the trace (“Trace – Marker – Marker
Search – Peak Search >”). With a matched termination at the end of the second cable,
the following result is obtained:

The spikes can be interpreted as follows:

C “Mkr 1” shows the position of the first adapter between the analyzer port and the

first cable.

C “Mkr 2” shows the position of the fault in the first cable.
C “Mkr 3” shows the position of the second adapter between the first and the second

cable, causing a reflection at either side. The distance between the two maxima of
this spike corresponds to the length of the adapter.

C “Mkr 4” shows the reflection at the end of the second cable due to a small residual

mismatch.

With an open second cable, the result looks a little more complex:

AS 1ZKD-6 – 01, M. Jetter, 12/2007 2