Concepts and features
R&S
®
ZNA
125
User Manual 1178.6462.02 ─ 20
Amp
VNA
3
2
coupler
DUT
Redefined Physical Port 1
a wave: b
2
b wave: b
3
Source: Port 1
Redefined Physical Port 2
a wave: a
4
b wave: b
4
Source: Port 4
1
4
Figure 4-5: Two redefined ports
High Signal Power
When dealing with external signal amplification, make sure that:
●
the signals fed to the analyzer are within the allowed range
●
during calibration the calibration standards meet the requirements in terms of their
power handling capacity
Attenuator pads can be used to adapt the power levels.
4.3.2
Reference impedances
Changing the reference impedances of the analyzer ports is often referred to as
renormalization of port impedances. Renormalization means that the measurement
results measured at 50 Ω (75 Ω) are converted into results at arbitrary port impedance.
●
Renormalization of the physical port impedances affects, e.g., S-parameters and
wave quantities in "Power" representation.
●
Renormalization of the balanced port impedances affects all measured quantities
that the analyzer provides for balanced ports.
The default reference impedance of a physical port is equal to the reference impe-
dance of the connector type assigned to the port (50 Ω or 75 Ω). It can be defined as a
complex value. For balanced ports, it is possible to define separate complex reference
impedances for differential and for common mode.
The default values for the balanced port reference impedances are derived from the
default reference impedance of the physical analyzer ports (Z
0
= 50 Ω):
●
The default value for the differential mode is Z
0d
= 100 Ω = 2*Z
0
.
●
The default value for the common mode is Z
0c
= 25 Ω = Z
0
/2
Renormalization can be based on two alternative waveguide circuit theories whose
conversion formulas may yield different results if the reference impedance of at least
one test port has a non-zero imaginary part.
Measurement results
