Concepts and features
R&S
®
ZNB/ZNBT
167
User Manual 1173.9163.02 ─ 62
This calibration type requires a Short, an Open and a Match standard to be connected
to a single test port plus a Through standard between this calibrated source port and
the other load ports. The four standard measurements are used to derive the following
error terms:
●
The Short and Open standards are used to derive the source match and the reflec-
tion tracking error terms at the source port.
●
The Match standard is used to derive the directivity error at the source port.
●
The Through standard provides the transmission tracking error terms.
For calibration of two ports, a one-path two-port calibration requires only four standards
to be connected (instead of 7 for a full two-port TOSM calibration). It is suitable when
only the forward (e.g. S
11
and S
21
) or reverse S-parameters (e.g. S
22
and S
12
) are nee-
ded, and if the DUT is well matched, especially at the load port.
A one-path two-port calibration is also the best calibration method for test setups with
unidirectional signal flow.
4.5.1.4
TOSM and UOSM calibration
TOSM
A TOSM (Through – Open – Short – Match) calibration requires the same standards as
the one path two ports calibration, however, all measurements are performed in the for-
ward and reverse direction. TOSM is also referred to as SOLT (Short – Open – Load =
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
Calibration
