Concepts and Features
R&S
®
ZNA
214
User Manual 1178.6462.02 ─ 12
●
In a phase imbalance sweep, the analyzer changes the phase offset between the
physical ports within a configurable range.
Imbalance Compensation of a Waves
Since the mixed-mode S-parameters of a linear balanced DUT depend only on the
DUT itself, they will be independent of the amplitude or phase imbalance of the stimu-
lus signal. For example, S
dd21
of a differential amplifier in phase imbalance sweep will
not reveal the amplitude reduction of the differential output signal caused by unequal
lengths of the balanced input line conductors. This length asymmetry corresponds to a
phase imbalance increasing over frequency. In order to see the effect of such a phase
or amplitude imbalance, modified S-parameters are required. The modification is done
in such a way that if e.g. the imbalance of port 1 is swept, the imbalance of the a wave
of port 1 is compensated before the S-parameters are calculated.
The effect of the compensation is a constant amplitude of the differential or common
mode stimulus wave of port 1 over the imbalance sweep range. This reflects the situa-
tion of the user applying a stimulus signal of known nominal amplitude to the DUT, but
getting at the output only the amplified differential contents in this signal, which
depends on the imbalance. Usually, S-parameters of balanced devices measured with
active imbalance compensation will exhibit a maximum or minimum at zero imbalance.
The imbalance compensation is not only performed for mixed-mode S-parameters, but
also for the imbalance-swept a wave itself when it is selected as a measured quantity,
as well as for ratios including that wave.
5.7.5.3
True Differential Mode on Frequency-Converting DUTs
True differential mode can be combined with
frequency-converting measurement
. For this type of measurements, a consistent calibration is particularly impor-
tant.
5.7.5.4
True Differential Mode with Frequency Converters
If the
is combined with true differential mode, the analyzer
generates a true differential or common mode stimulus signal at a calibrated reference
plane which is located after two frequency converter ports. To achieve this, two fre-
quency converters with independent sources are combined to form a balanced con-
verter port. The frequency converters must provide the RF drive signal simultaneously
so that a third, independent LO signal is required.
Optional Extensions and Accessories
