Concepts and features
R&S
®
ZNA
204
User Manual 1178.6462.02 ─ 20
been assigned to the physical ports before, they are both corrected by the same
amount.
4.6.1.4
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.
Preconditions for Auto Length and Loss, effect on measured quantities and
exceptions
"Auto Length and Loss" is enabled if the measured quantity contains the necessary
phase information as a function of the frequency, and if the interpretation of the results
is unambiguous:
●
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 and Loss" on S-parameters, wave quantities and ratios is to
eliminate a linear phase response and account for a loss as described above. Conver-
ted admittances or impedances are calculated from the corresponding "Auto Length
and Loss" corrected S-parameters. Y-parameters, Z-parameters and stability factors
are not derived from a single S-parameter, therefore "Auto Length and Loss" is dis-
abled.
Calculation of loss parameters
The loss is assumed to be given in terms of the DC loss Loss
DC
, the reference fre-
quency f
ref
, and the loss at the reference frequency Loss(f
ref
). The formula used in the
Auto Loss algorithm is similar to the formula for manual entry of the loss parameters
(see
Chapter 4.6.1.2, "Definition of loss parameters"
The result is calculated according to the following rules:
●
The reference frequency f
ref
is kept at its previously defined value (default: 1 GHz).
●
The DC loss c is zero except for wave quantities and for S-parameters and ratios
with maximum dB magnitude larger than –0.01 dB.
●
"Auto Length and Loss" for a wave quantity centers the corrected dB magnitude as
close as possible around 0 dBm.
●
"Auto Length and Loss" for S-parameters and ratios centers the corrected dB mag-
nitude as close as possible around 0 dB.
Offset parameters and de-/embedding
