VNA concepts and features
R&S
®
ZNL/ZNLE
281
User Manual 1178.5966.02 ─ 19
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 9.6.1.2, "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.
he resulting offset parameters are displayed in the [Offset Embed] > "Offset" softtool
tab.
Auto Length and Loss for balanced ports
The "Auto Length and Loss" function can be used for balanced port configurations as
well. If the active test port is a balanced (logical) port, then the same offset parameters
must be assigned to both physical ports that are combined to form the logical port. If
different offset parameters have been assigned to the physical ports before, they are
both corrected by the same amount.
9.6.1.5
Fixture Compensation
"Fixture Compensation" is an automated length offset and loss compensation for test
fixtures. The analyzer performs a one-port reflection measurement at each port,
assuming the inner contacts of the test fixtures to be terminated with an open or short
circuit.
Offset parameters and de-/embedding
