Sonnet User's Guide - Sonnet Software

Sonnet User’s Guide
S-Parameters
from em with
de-embedding.
S-parameters from em
without de-embedding
-R
-C
R
Device
Under
Test
C
Block cascaded to negate
box-wall port discontinuity
Box-wall port
discontinuity
De-embedding automatically cancels the discontinuity associated with a box-wall port.
Shifting Reference Planes
Transmission lines are required in many circuits to connect ports to the device under
test (DUT). If the length of a transmission line is more than a few degrees relative
to a wavelength, unwanted phase (and possibly loss) will be added to the S-
parameter results. If the impedance of the transmission line differs from the normalizing
impedance of the S-parameters (usually 50 ohms), an additional error in
the S-parameters results. Thus, if we are only interested in the behavior of the
DUT, any “long” transmission lines connecting the ports to the DUT should be removed
during de-embedding. The process of removing lengths of transmission
line during de-embedding is known as “shifting reference planes”.
Reference planes may be specified in the project editor for box-wall, co-calibrated,
and auto-grounded ports, but not ungrounded-internal and via ports. When em
detects a reference plane, and de-embedding is enabled, it automatically builds
and analyzes the calibration standards necessary to de-embed the port and shift the
reference plane by the specified length.
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