Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 130 / 813

Screen Elements R&S
®
ZVA/ZVB/ZVT
1145.1084.12 3.20 E-1
The formulas also hold for real results, which are treated as complex values with zero imaginary part
(y = 0).
Trace Format Description Formula
dB Mag Magnitude of z in dB |z| = sqrt ( x 2 + y 2 )
dB Mag(z) = 20 * log|z| dB
Lin Mag Magnitude of z, unconverted |z| = sqrt ( x 2 + y 2 )
Phase Phase of z
φ
(z) = arctan (y/x)
Real Real part of z Re(z) = x
Imag Imaginary part of z Im(z) = y
SWR (Voltage) Standing Wave Ratio SWR = (1 + |z|) / (1 – |z|)
Delay Group delay, neg. derivative of the phase response
– d
φ
(z) / d
ω
(
ω
= 2
π
* f)
An extended range of formats and conversion formulas is available for markers. To convert any
point on a trace, create a marker and select the appropriate marker format. Marker and trace formats
can be selected independently.
Polar Diagrams
Polar diagrams show the measured data (response values) in the complex plane with a horizontal real
axis and a vertical imaginary axis. The grid lines correspond to points of equal magnitude and phase.
•
The magnitude of the response values corresponds to their distance from the center. Values with
the same magnitude are located on circles.
•
The phase of the response values is given by the angle from the positive horizontal axis . Values
with the same phase on straight lines originating at the center.
The following example shows a polar diagram with a marker used to display a pair of stimulus and
response values.
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.