GUI reference
R&S
®
ZND
270
User Manual 1173.9557.02 ─ 61
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 4.3.8, "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, related settings"
Remote command:
GDELay
Aperture Points
Defines an aperture Δf for the (group) "Delay" calculation. The value is entered as
number of sweep steps (= number of sweep points - 1).
For background information, see
Chapter 4.3.8, "Delay, aperture, electrical length"
Properties:
The delay at each sweep point is computed as:
where the aperture Δf is a finite frequency interval around the sweep point f
0
and the
analyzer measures the corresponding phase change ΔΦ, which is calculated via a lin-
ear regression algorithm over the frequency points of the aperture.
Application:
The aperture must be adjusted to the conditions of the measurement. A
small aperture increases the noise in the group delay; a large aperture tends to mini-
mize the effects of noise and phase uncertainty, but at the expense of frequency reso-
lution. Phase distortions (i.e. deviations from linear phase) which are narrower in fre-
quency than the aperture tend to be smeared over and cannot be measured.
Remote command:
CALCulate<Chn>:GDAPerture:SCOunt
Format softtool
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