R&S
®
ZVA / R&S
®
ZVB / R&S
®
ZVT System Overview
Calibration Overview
Operating Manual 1145.1084.12 – 30 56
The match standard is used to derive the directivity error.
A full one-port calibration is more accurate than a normalization but is only applicable for reflection
measurements.
One-Path Two-Port Calibration
A one-path two-port calibration combines a 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 a second load port. 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 reflection 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 term.
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 needed, and if the DUT is well matched, especially at the load port. It is also the best
calibration method for test setups with unidirectional signal flow, e.g. a pulsed measurement using an
external generator.
TOSM Calibration
A TOSM (Through – Open – Short – Match) calibration requires the same standards as the one-path two-
port calibration, however, all measurements are performed in the forward 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 both source ports.
The transmission tracking is determined for each direction.
TOSM is a multi-port calibration type (number of ports: n = 2, 3, ...). The number of required standard
measurements and of error terms increases as shown in the following table.
Number of connected standards (complete TOSM
model)
Number of standard
measurements
4 * 3
+2 * (3 + 2 + 1) = 24
An open, through and match measurement is required at each port; in addition, a through must be
measured between any combination of ports and in both directions. Therefore the number N of standard
connections for an n-port TOSM calibration is equal to
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