Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 149 / 813

R&S
®
ZVA/ZVB/ZVT Calibration Overview
1145.1084.12 3.39 E-1
One-Path Two-Port Calibration
A one-path two-port calibration combines a full one-port calibration with a transmission normalization,
so it 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) and 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 to be measured and the DUT is well matched, especially at the load port.
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 calibration is provided for 2-port, 3-port or 4-port measurements. The number of required
standard measurements and of error terms increases as shown in the following 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
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 measurements for an n-port TOSM calibration is equal to
. ) 2 (
! ) 2 ( ! 2
!
2 3
2
2 3
+ ⋅ =
− ⋅
⋅ + ⋅ =






⋅ + ⋅ =
n n
n
n
n
n
n N
The analyzer automatically performs each through measurement in both directions, so the number of
connected standards is smaller than the number of measurements.
TOM Calibration
A TOM (Through – Open – Match) calibration requires a low-reflection, low-loss through standard with
an electrical length that may be different from zero, an open and a match. The characteristics of all
standards must be fully known.