VNA Concepts and Features
R&S
®
ZNL/ZNLE
224
User Manual 1178.5966.02 ─ 07
Examples for using wave quantities
The wave quantities provide the power at the different receive ports of the analyzer.
This is different from an S-parameter measurement, where the absolute power of a lin-
ear device is canceled. Wave quantities are therefore suitable for the following mea-
surement tasks:
●
Analysis of nonlinearities of the DUT.
●
Use of the analyzer as a selective power meter.
The notation for wave quantities is as follows:
●
"a
i
Src Port j" denotes the wave incoming at DUT port i, when DUT port j is stimula-
ted.
a
i
is detected at the reference receiver of the VNA port connected to DUT port i.
●
"b
i
Src Port j" denotes the wave outgoing at DUT port i, when DUT port j is stimula-
ted.
b
i
is detected at the measurement receiver of the VNA port connected to DUT port
i.
In a standard forward S-parameter measurement, a
1
Src Port 1 is the incident wave
and b
1
Src Port 1 is the reflected wave at DUT port 1.
8.3.4.2
Ratios
A ratio measurement provides the complex ratio of any combination of transmitted or
received wave amplitudes. Ratios complement the S-parameter measurements, where
only ratios of the form b
i
/a
j
(ratios between outgoing and incoming waves at the DUT
ports) are considered.
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 8.3.4.1, "Wave Quantities"
on page 223). 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
.
Measurement Results
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