Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 133 / 813

R&S
®
ZVA/ZVB/ZVT Screen Elements
1145.1084.12 3.23 E-1
Circles of equal
resistance
Arcs of equal
reactance
Open-circuited
load (Z = infinity)
Short-circuited
load (Z = 0)
Matching
impedance (Z = Z
0
)
Examples for special points in the Smith chart:
•
The magnitude of the reflection coefficient of an open circuit (Z = infinity, I = 0) is one, its phase is
zero.
•
The magnitude of the reflection coefficient of a short circuit (Z = 0, U = 0) is one, its phase is –
180
0
.
Inverted Smith Chart
The inverted Smith chart is a circular diagram that maps the complex reflection coefficients S
ii
to
normalized admittance values. In contrast to the polar diagram, the scaling of the diagram is not linear.
The grid lines correspond to points of constant conductance and susceptance.
•
Points with the same conductance are located on circles.
•
Points with the same susceptance produce arcs.
The following example shows an inverted Smith chart with a marker used to display the stimulus value,
the complex admittance Y = G + j B and the equivalent inductance L (see marker format description in
the help system).
A comparison of the inverted Smith chart with the Smith chart and the polar diagram reveals
many similarities between the different representations. In fact the shape of a trace does not change at
all if the display format is switched from
Polar to Inverted Smith or Smith – the analyzer simply replaces
the underlying grid and the default marker format.
Inverted Smith chart construction
The inverted Smith chart is point-symmetric to the Smith chart: