Rohde & Schwarz R&S ZVA 8 - Polar Diagrams

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) / dω (ω = 2π * 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.