Rohde & Schwarz ZNB20, User Manual

Page: 159 / 1332

Concepts and Features
R&S
®
ZNB/ZNBT
144 User Manual 1173.9163.02 ─ 38
= Match – Through) calibration. The four standards are used to derive 6 error terms for
each signal direction:
●
In addition to the source match and reflection tracking error terms provided by the
one-path two-port calibration, TOSM also provides the load match.
●
The directivity error is determined at all source ports.
●
The transmission tracking is determined for each direction.
TOSM calibration is provided for arbitrary n-port measurements (n>1). The number of
required standard measurements and of error terms increases as shown in the follow-
ing table.
Number of ports Number of standards
to be connected Number of standard
measurements
Number of error terms
*)
2 2 * 3
+1 = 7
2 * 3
+2 * 1 = 8
2 * 3
+ 2 * 2 = 10
3 3 * 3
+ 2 + 1 = 12
3 * 3
+2 * (2 + 1) = 15
3 * 3
+ 2 * 2 * 3 = 21
4 4 * 3
+3 + 2 + 1 = 18
4 * 3
+2 * (3 + 2 + 1) = 24
4 * 3
+ 2 * 2 * 6 = 36
*) No isolation terms are available.
An Open, Through and Match measurement is required at each port; in addition, for a
full TOSM, a Through must be measured for every directed port pair. Therefore the
total number of standard measurements for an n-port TOSM calibration is
3n + n (n-1)
= n (n+2) . However, this number can be significantly decreased without losing too
much precision (see Chapter 4.5.1.11, "Full n-Port Calibration with Reduced Number of
Through Connections" , on page 150)
The analyzer automatically performs each through measurement in both directions, so
the number of connected standards is smaller than the number of measurements.
Manual TOSM calibration supports Complementary Isolation Measurement (optional).
UOSM: TOSM with unknown Through
The analyzer can perform a TOSM calibration with any 2-port network serving as
through connection, provided that it fulfills the reciprocity condition S
21
= S
12
. The modi-
fied TOSM calibration is referred to as UOSM (Unknown through – Open – Short –
Match) calibration. It can be selected as follows:
●
If different connector types are assigned to the test ports, the analyzer automati-
cally replaces TOSM by UOSM.
[The network analyzer supports different connector types at its test ports in order to
measure DUTs with different port connectors; see also
Chapter 4.5.1.5, "Adapter
Removal" , on page 145. ]
●
If the same connector types are used but an appropriate Through standard is not
defined, the analyzer also replaces TOSM by UOSM.
Calibration