VNA concepts and features
R&S
®
ZNL/ZNLE
280
User Manual 1178.5966.02 ─ 19
This yields the delay in one direction and should be approx. equal to the "Auto
Length" result.
The measurement results using trace formats and trace statistics functions depend on
the selected delay aperture and evaluation range. "Auto Length" is particularly accu-
rate because it uses all sweep points. For non-dispersive cables, aperture and evalua-
tion range effects are expected to vanish.
Use [Mkr] > "Set by Marker" > Zero Delay at Marker to set the delay at a special trace
point to zero.
Preconditions for Auto Length, effect on measured quantities and exceptions
"Auto Length" is enabled if the measured quantity contains the necessary phase infor-
mation as a function of frequency, and if the interpretation of the results is unambigu-
ous:
●
A frequency sweep must be active.
●
The measured quantity must be an S-parameter, ratio, wave quantity, a converted
impedance or a converted admittance.
The effect of "Auto Length" on S-parameters, wave quantities and ratios is to eliminate
a linear phase response as described above. The magnitude of the measured quantity
is not affected. Converted admittances or impedances are calculated from the corre-
sponding "Auto Length" corrected S-parameters. Y-parameters, Z-parameters and sta-
bility factors are not derived from a single S-parameter, therefore "Auto Length" is dis-
abled.
Auto Length for logical ports
The "Auto Length" function can be used for balanced port configurations as well. If the
active test port is a logical port, then the same length offset must be assigned to both
physical ports that are combined to form the logical port. If different length offsets have
been assigned to the physical ports before, they are both corrected by the same
amount.
9.6.1.4
Auto Length and Loss
The "Auto Length and Loss" function determines all offset parameters at the active
trace's receive port such that the residual group delay of the active trace (defined as
the negative derivative of the phase response) is minimized
and
the measured loss is
minimized as far as possible across a configurable frequency range.
"Auto Length and Loss" involves a two-step procedure:
●
An "Auto Length" correction modifies the phase of the measured quantity, minimiz-
ing the residual group delay. The magnitude of the measured quantity is not affec-
ted.
●
The automatic loss correction modifies the magnitude of the measured quantity,
leaving the (auto length-corrected) phase unchanged.
Offset parameters and de-/embedding
