VNA Concepts and Features
R&S
®
ZNL/ZNLE
220
User Manual 1178.5966.02 ─ 07
ii
ii
i
ii
S
S
Z
Z
1
1
0
The transmission parameters are calculated according to:
,
,
2
0
0
0
0
j
i
Z
Z
S
Z
Z
Z
j
i
ij
j
i
ij
The converted admittances are defined as the inverse of the impedances.
Examples:
●
Z
11
is the input impedance of a 2-port DUT that is terminated at its output with the
reference impedance Z
0
(matched-circuit impedance measured in a forward reflec-
tion measurement).
You can also read the converted impedances in a reflection coefficient measurement
from the Smith chart.
Shunt-thru Measurements
The shunt-thru method is used for measuring very low impedances. A typical applica-
tion are measurements on power distribution network (PDN) components, such as
bypass capacitors and DC-DC converters.
The R&S
ZNL/ZNLE focuses on PCB-level measurements and uses S
21
to calculate
the DUT impedance using the formula:
Z
DUT
= 1/2 · (50 Ω + Probe Tip Impedance) · S
21
/ (1-S
21
)
DUT
VNA
1
2
8.3.2.2
Z-Parameters
The Z-parameters describe the impedances of a DUT with open output ports (impe-
dance = 0). The analyzer provides the full set of Z-parameters including the transfer
impedances (i.e. the complete nxn Z-matrix for an n port DUT).
Measurement Results
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