System Overview
R&S
®
ZVA
69
Quick Start Guide 1145.1090.62 ─ 10
A comparison of the Smith chart, the inverted Smith chart and the polar diagram reveals
many similarities between the two representations. In fact the shape of a trace does not
change at all if the display format is switched from "Polar" to "Smith" or "Inverted
Smith" – the analyzer simply replaces the underlying grid and the default marker format.
Smith chart construction
In a Smith chart, the impedance plane is reshaped so that the area with positive resist-
ance is mapped into a unit circle.
The basic properties of the Smith chart follow from this construction:
●
The central horizontal axis corresponds to zero reactance (real impedance). The
center of the diagram represents Z/Z
0
= 1 which is the reference impedance of the
system (zero reflection). At the left and right intersection points between the horizontal
axis and the outer circle, the impedance is zero (short) and infinity (open).
●
The outer circle corresponds to zero resistance (purely imaginary impedance). Points
outside the outer circle indicate an active component.
●
The upper and lower half of the diagram correspond to positive (inductive) and neg-
ative (capacitive) reactive components of the impedance, respectively.
Screen Elements
