Concepts and Features
R&S
®
ZNC
42
User Manual 1173.9557.02 ─ 13
,
)
Im(
)
Re(
1
)
Im(
2
)
/
Im(
2
2
0
Y
Y
B
According to the two equations above, the graphical representation in an inverted Smith
chart has the following properties:
●
Real reflection coefficients are mapped to real admittances (conductances).
●
The center of the
Γ
plane (
Γ
= 0) is mapped to the reference admittance Y
0
, whereas
the circle with |
Γ
| = 1 is mapped to the imaginary axis of the Y plane.
●
The circles for the points of equal conductance are centered on the real axis and
intersect at Y = infinity. The arcs for the points of equal susceptance also belong to
circles intersecting at Y = infinity (short circuit point (–1, 0)), centered on a straight
vertical line.
Examples for special points in the inverted Smith chart:
●
The magnitude of the reflection coefficient of a short circuit (Y = infinity, U = 0) is one,
its phase is –180 deg.
●
The magnitude of the reflection coefficient of an open circuit (Y = 0, I = 0) is one, its
phase is zero.
3.2.4.6
Measured Quantities and Display Formats
The analyzer allows any combination of a display format and a measured quantity. The
following rules can help to avoid inappropriate formats and find the format that is ideally
suited to the measurement task.
●
All formats are suitable for the analysis of reflection coefficients S
ii
. The formats
"SWR", "Smith" and "Inverted Smith" lose their original meaning (standing wave ratio,
normalized impedance or admittance) if they are used for transmission S-parameters,
ratios and other quantities.
●
The complex "Impedances", "Admittances", "Z-parameters", and "Y-parameters" are
generally displayed in one of the Cartesian diagrams with linear vertical axis scale or
in a polar diagram.
●
The real "Stability Factors" are generally displayed in a linear Cartesian diagram ("Lin
Mag" or "Real"). In complex formats, real numbers represent complex numbers with
zero imaginary part.
The following table gives an overview of recommended display formats.
Screen Elements
