VNA GUI reference
R&S
®
ZNL/ZNLE
373
User Manual 1178.5966.02 ─ 19
Cable types are defined by their relative permittivity
εr
or, equivalently, by their velocity
factor
1/sqrt(εr)
, and a frequency-dependent attenuation table (see
The velocity factor is a measure for the velocity of an electromagnetic wave in a dielec-
tric with permittivity ε
r
, relative to its velocity in a vacuum (velocity factor < 1). It is nee-
ded to convert the propagation times into distances.
Frequency-Dependent Attenuation Table
The "Attenuation of <Cable Type>" dialog defines the frequency dependence of the
cable attenuation. The measured cables are assumed to be homogeneous so that the
attenuation per length unit is constant. This means that the attenuation can be
expressed in units of dB/m. Due to the skin effect and various other factors, the attenu-
ation is frequency-dependent.
For predefined cables, the table is read-only.
Access:
Available Cable Types... dialog
> "Attenuation" column >
...
Given the specified attenuation values the R&S
ZNL/ZNLE calculates the attenuation
factor at the center of the channel's sweep range and corrects the impulse response
trace using this attenuation factor
Attenuation (f
center
)
.
The frequency dependence can be defined in two alternative ways:
●
Single reference frequency
If the cable attenuation is specified at a single frequency
f
1
, the R&S
ZNL/ZNLE
calculates
Attenuation (f
center
)
using
Attenuation (f
1
) / Attenuation (f
center
) = sqrt (f
1
/ f
center
),
which accounts for the impact of the skin effect.
Trace softtool