Concepts and features
R&S
®
ZNA
202
User Manual 1178.6462.02 ─ 20
For a non-dispersive DUT, the delay defined above is constant over the considered fre-
quency range and equal to the negative derivative of the phase response for the fre-
quency (see mathematical relations). The length offset parameters compensate for a
constant delay, which is equivalent to a linear phase response.
4.6.1.2
Definition of loss parameters
The loss is the attenuation a wave experiences when traveling through the transmis-
sion line. In logarithmic representation, it can be modeled as the sum of a constant and
a frequency-dependent part, where the frequency dependence is due to the skin effect.
In the limit case, where the length of the transmission line is considered to be "almost
zero", the loss is considered constant:
Otherwise, if the loss at DC and one additional frequency
f
1
is known (or measured),
the loss at frequency f is approximated by:
If in addition the loss at a second frequency
f
2
is known (or measured), then the loss
can be approximated by:
In practice, the frequency-dependent part ist often dominant, so that
Loss
DC
can be set
to zero. Experimentally, the loss value at DC can be determined in a separate mea-
surement at a very low frequency (f --> 0).
4.6.1.3
Auto Length
The "Auto Length" function adds an electrical length offset to the active trace's receive
port, such that the residual delay of the active trace (defined as the negative derivative
of the phase response) is minimized across a configurable frequency range. If "Delay"
is the selected trace format, the entire trace is shifted in vertical direction and centered
on zero. In phase format, the "Auto Length" corrected trace shows the deviation from
linear phase.
Length and delay measurement, related settings
"Auto Length" is suited for length and delay measurements on transmission lines.
1. Connect a (non-dispersive) cable to a single analyzer port no. n and measure the
reflection factor S
nn
.
Offset parameters and de-/embedding