System Overview
R&S
®
ZVA
68
Quick Start Guide 1145.1090.62 ─ 10
Example: Reflection coefficients in polar diagrams
If the measured quantity is a complex reflection coefficient (S
11
, S
22
etc.), then the center
of the polar diagram corresponds to a perfect load Z
0
at the input test port of the DUT (no
reflection, matched input), whereas the outer circumference (|S
ii
| = 1) represents a totally
reflected signal.
Examples for definite magnitudes and phase angles:
●
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 deg.
3.2.4.4
Smith Chart
The Smith chart is a circular diagram that maps the complex reflection coefficients S
ii
to
normalized impedance values. In contrast to the polar diagram, the scaling of the diagram
is not linear. The grid lines correspond to points of constant resistance and reactance.
●
Points with the same resistance are located on circles.
●
Points with the same reactance produce arcs.
The following example shows a Smith chart with a marker used to display the stimulus
value, the complex impedance Z = R + j X and the equivalent inductance L.
Screen Elements
