Concepts and Features
R&S
®
ZNB/ZNBT
108
User Manual 1173.9163.02 ─ 53
Diagram Representation
When a Cartesian trace is assigned to a diagram, the stimulus variable appears on the
horizontal axis (x-axis), the response values appear on the vertical axis (y-axis).
Graph Scaling
●
Except for the "Log Mag" format, the y-axis scale is always linear.
●
The x-axis scaling depends on the sweep type of the channel to which the trace is
assigned:
–
For sweep types "Lin Freq", "Power", "CW Mode" and "Time" it is scaled line-
arly.
–
For sweep type "Log Freq", it is scaled logarithmically.
The resulting linear or lin-log grid is plotted with the formatted trace.
The following examples show "dB Mag" Cartesian traces for the same measured quan-
tity and sweep range, but with "Lin Freq" and "Log Freq" sweep types.
Figure 5-3: S11 trace in dB Mag format: sweep type Lin Freq (top) and Log Freq (bottom)
Conversion of Complex to Real Quantities
Among the measured quantities the R&S
ZNB/ZNBT supports, only "Stability" factors,
"Power Sensor" results, and "DC" values are real. All other results measured quantities
complex.
The following table shows how "real" response values are calculated from complex
measurement values z = x + j y (where x, y, z are functions of the sweep variable). The
formulas also hold for real measurement values (y = 0).
Trace Format
Description
Formula
"dB Mag"
Magnitude of z in dB
dB Mag(z) = 20 * log|z| dB
"Phase"
Phase of z
φ (z) = arctan (y/x)
"SWR"
(Voltage) Standing Wave Ratio
SWR = (1 + |z|) / (1 – |z|)
Screen Elements
