Concepts and Features
R&S
®
ZNA
174
User Manual 1178.6462.02 ─ 12
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A combination of four-port and two-port networks can be applied to any pair of sin-
gle-ended ports. Moreover it is possible to combine several port pairs in an arbi-
trary order (port pair de-/embedding).
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Single-ended and/or balanced port (de-)embedding can be combined with ground
loop (de-)embedding. A ground loop models the effect of a non-ideal ground con-
nection of the DUT.
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Transformation networks can be defined by a set of S-parameters stored in a
Touchstone file or by an equivalent circuit with lumped elements.
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The same networks are available for embedding and deembedding.
5.6.2.1
Embedding a DUT
To be integrated in application circuits, high-impedance components like Surface
Acoustic Wave (SAW) filters are often combined with a matching network. To obtain
the characteristics of a component with an added matching network, both must be inte-
grated in the measurement circuit of the network analyzer.
The idea of virtual embedding is to simulate the matching network and avoid using
physical circuitry so that the analyzer ports can be directly connected to the input and
output ports of the DUT. The matching circuit is taken into account numerically. The
analyzer measures the DUT alone but provides the characteristics of the DUT, includ-
ing the desired matching circuit.
This method provides a number of advantages:
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The measurement uncertainty is not impaired by the tolerances of real test fixtures.
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There is no need to fabricate test fixtures with integrated matching circuits for each
type of DUT.
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Calibration can be performed at the DUT's ports. If necessary, (e.g. for compensat-
ing for the effect of a test fixture) it is possible to shift the calibration plane using
length offset parameters.
5.6.2.2
Deembedding a DUT
Deembedding and embedding are inverse operations: A deembedding problem is
given if an arbitrary real network connected to the DUT is to be virtually removed to
obtain the characteristics of the DUT alone. Deembedding is typically used for DUTs
which are not directly accessible because they are inseparably connected to other
components, e.g. for MMICs in a package or connectors soldered to an adapter board.
To be numerically removed, the real network must be described by a set of S-parame-
ters or by an equivalent circuit of lumped elements. Deembedding the DUT effectively
extends the calibration plane towards the DUT ports, enabling a realistic evaluation of
the DUT without the distorting network. Deembedding can be combined with length off-
set parameters; see
Chapter 5.6.1, "Offset Parameters"
The simplest case of single port deembedding can be depicted as follows:
Offset Parameters and De-/Embedding
