Concepts and Features
R&S
®
ZNC
95
User Manual 1173.9557.02 ─ 13
Calculation of loss parameters
The loss is assumed to be given in terms of the DC loss Loss
DC
, the reference frequency
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
ter 3.6.1.2, "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.
The resulting offset parameters are displayed in the "CHANNEL > EFFSET EMBED >
Offset" tab.
Auto Length and Loss for logical ports
The "Auto Length and Loss" function can be used for balanced port configurations as
well. If the active test port is a 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.
3.6.1.5
Fixture Compensation
Fixture compensation is an automated length offset and loss compensation for test fix-
tures with up to four ports (for 4-port analyzers). The analyzer performs a one-port reflec-
tion measurement at each port, assuming the inner contacts of the test fixtures to be
terminated with an open or short circuit.
Fixture compensation complements a previous system error correction and replaces a
possible manual length offset and loss correction. For maximum accuracy, it is recom-
mendable to place the reference plane as close as possible towards the outer test fixture
connectors using a full n-port calibration. The fixture compensation is then carried out in
a second step, it only has to compensate for the effect of the test fixture connections.
The following features can further improve the accuracy of the fixture compensation:
●
"Direct Compensation" provides a frequency-dependent transmission factor (instead
of a global electrical length and loss).
●
"Open and Short" causes the analyzer to calculate the correction data from two sub-
sequent sweeps. The results are averaged in order to compensate for errors due to
non-ideal terminations.
Offset Parameters and Embedding