Rohde & Schwarz ZVL series - Page 202

R&S ZVL GUI Reference
Trace Menu
Operating Manual 1303.6580.32-06
187
Use the MMEMory... commands to store or re-load all cable specifications including the user-defined
ones to/from a separate directory.
Remote control:
CALCulate:TRANsform:DTFault:DEFine
CALCula
te:TRANsform:DTFault:SELect
CALCulate:TRANsform:DTFault:DELete
MMEMory:LOAD:CABLe
MMEMory:SAVE:CABLe
Attenuation Factors for Cables
The measured cables are assumed to be homogenuous so that the attenuation per length unit is constant.
This means that the attenuation can be expressed in units of dB/m or dB/ft, depending on the Distance
Unit selected in the System Configuration dialog. Due to the skin effect and various other factors, the
attenuation is generally frequency-dependent.
The Attenuation dialog defines the frequency dependence of the cable attenuation. A click on an entry in
the Attenuation column of the Available Cable Types dialog opens this dialog.
For user-defined cables, the Frequency and Attenuation columns in the dialog are editable. The frequency
dependence can be defined in two alternative ways:
• Single reference frequency
If the cable attenuation is specified at a single frequency, the R&S ZVL calculates the attenuation
factor at the center frequency of the sweep range, assuming that Attenuation (f
const
) / Attenuation
(f
center
) = sqrt (f
const
/ f
center
). This frequency dependence accounts for the impact of the skin effect.
The impulse response trace is corrected with the calculated attenuation factor Attenuation (f
center
).
• Frequency list
If the cable attenuation is specified at several frequency points, the R&S ZVL calculates the
attenuation factor f
center
at the center frequency of the sweep range by linear interpolation. If f
center
is
outside the specified frequency range, then the frequency dependence is linearly extrapolated,
using the two first or the last two specified frequency points.
The impulse response trace is corrected with the calculated attenuation factor Attenuation (f
center
).
It is recommended to specify the cable attenuation as accurately as possible. The correction due to the
attenuation factor is proportional to the measured distance between the fault and the reference plane: The
larger the distance, the larger the correction.