VNA Concepts and Features
R&S
®
ZNL/ZNLE
245
User Manual 1178.5966.02 ─ 07
standard allows you to eliminate errors due to the directivity of the internal couplers,
which improves the accuracy of reflection measurements on well-matched DUTs (high
return loss).
For reflection measurements on DUTs with low return loss, accuracy may be degraded
compared to a simple reflection normalization.
8.5.1.2
Reflection OSM Calibration
A reflection OSM (full one-port) calibration requires a Short, an Open and a Match
standard to be connected to a single test port. The three standard measurements are
used to derive all three reflection error terms:
●
The Short and Open standards are used to derive the source match and the reflec-
tion tracking error terms.
●
The Match standard is used to derive the directivity error.
A reflection OSM calibration is more accurate than a normalization but is only applica-
ble for reflection measurements.
8.5.1.3
One Path Two Ports Calibration
A one path two ports calibration combines a reflection OSM (full one-port) calibration
with a transmission normalization. The fully calibrated port is termed the node port.
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. It is also the best cali-
bration method for test setups with unidirectional signal flow, e.g. a pulsed measure-
ment using an external generator.
8.5.1.4
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 =
Calibration
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