VNA concepts and features
R&S
®
ZNL/ZNLE
225
User Manual 1178.5966.02 ─ 19
Examples for using ratios
A measurement of ratios is particularly suitable for the following test scenarios:
●
The test setup or some of its components (e.g. active components or non-recipro-
cal devices) do not allow a system error correction so that a complete S-parameter
measurement is not possible.
●
The test setup contains frequency-converting components so that the transmitted
and the received waves are at different frequencies.
●
A ratio of two arbitrary waves that is not an element of the S-matrix (e.g. a ratio of
the form a
i
/a
j
) is needed.
The notation for ratios is similar to the notation for wave quantities (see
ter 9.3.5.1, "Wave quantities"
on page 224). Given a source port k, any ratio between
wave quantities "a
i
Src Port k" and "b
j
Src Port k" can be measured.
Examples:
●
"b
2
/a
1
Src Port 1" is the ratio of the outgoing wave at DUT port 2 and the incident
wave at DUT port 1 (i.e. DUT port 1 ist stimulated). This corresponds to the forward
transmission coefficient S
21
.
●
"b
1
/a
1
Src Port 1" is the ratio of the outgoing wave at DUT port 1 and the incident
wave at DUT port 1 (i.e. DUT port 1 ist stimulated). This corresponds to the forward
reflection coefficient S
11
.
9.3.6
Unbalance-balance conversion
Unbalance-balance conversion is the simulation of one or more unbalance-balance
transformers (baluns) integrated in the measurement circuit. It converts the DUT ports
from an unbalanced state into a balanced state and virtually separates the differential
and common mode signals. The analyzer measures the unbalanced state but converts
the results and calculates mixed mode parameters, e.g. mixed mode S-parameters. No
physical transformer is needed.
To perform balanced measurements, a pair of physical analyzer ports is combined to
form a logical port. The balanced port of the DUT is directly connected to the analyzer
ports. For a two-port analyzer, a single balanced port can be defined.
Measurement results
