VNA GUI Reference
R&S
®
ZNL/ZNLE
387
User Manual 1178.5966.02 ─ 07
Properties:
The Inverted Smith chart is a circular diagram obtained by mapping the
positive complex semi-plane into a unit circle. If the measured quantity is a complex
reflection coefficient S
ii
, then the unit Inverted Smith chart represents the normalized
admittance. In contrast to the polar diagram, the scaling of the diagram is not linear.
Application:
Reflection measurements, see example in
Tip:
The axis for the sweep variable is lost in Smith charts but the marker functions
easily provide the stimulus value of any measurement point. dB values for the magni-
tude and other conversions can be obtained by the "Marker Format" functions.
Remote command:
ISMith
Delay
Calculates the (group) delay from the measured quantity (typically a transmission S-
parameter) and displays it in a Cartesian diagram.
Properties:
The group delay τ
g
represents the propagation time of wave through a
device. τ
g
is a real quantity and is calculated as the negative of the derivative of its
phase response. A non-dispersive DUT shows a linear phase response, which produ-
ces a constant delay (a constant ratio of phase difference to frequency difference).
For more information, refer to
Chapter 8.3.8, "Delay, Aperture, Electrical Length"
Application:
Transmission measurements, especially with the purpose of investigating
deviations from linear phase response and phase distortions. To obtain the delay, a fre-
quency sweep must be active.
Tip:
The cables between the analyzer test ports and the DUT introduce an unwanted
delay, which often can be assumed to be constant. Use the Zero Delay at Marker func-
tion, define a numeric length "Offset" or use the "Auto Length" function to compensate
for this effect in the measurement results. To compensate for a frequency-dependent
delay in the test setup, a system error correction is required.
Note:
The delay for reflection factors corresponds to the transmission time in forward
and reverse direction; see "Length and delay measurement" in
Remote command:
GDELay
Aperture Points
Defines an aperture Δf for the (group) "Delay" calculation. The value is entered as
number of "Aperture Points" (i.e. sweep steps).
Properties:
The delay at each sweep point is computed as:
f
deg
meas
g
360
,
where the aperture Δf is a finite frequency interval around the sweep point f
0
and the
analyzer measures the corresponding phase change ΔΦ.
Format Softtool
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Allice Messtechnik GmbH
