R&S ZVL GUI Reference
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Operating Manual 1303.6580.32-06
195
Y = F
requency/angular velocity in radians/s
f
= Frequency in Hz
In practice, the analyzer calculates an approximation to the derivative of the phase response, taking a
small frequency interval Qf and determining the corresponding phase change Qa. The delay is thus
computed as:
The aperture Qf must be adjusted to the conditions of the measurement.
If the delay is constant over the considered frequency range (non-dispersive DUT, e.g. a cable), then `
g
and `
g,meas
are identical and
where Qt is the propagation time of the wave across the DUT, which often can be expressed in terms of its
mechanical length L
mech
, the permittivity ], and the velocity of light c. The product of L
mech
.
sqrt(N) is termed
the electrical length of the DUT and is always larger or equal than the mechanical length (] > 1 for all
dielectrics and ] = 1 for the vacuum).
Application: Transmission measurements, especially with the purpose of investigating deviations from
linear phase response and phase distortions. To obtain the delay a frequency sweep must be active.
The cables connecting the analyzer test ports to the DUT introduce an unwanted delay, which often
can be assumed to be constant. Use the Zero Delay at Marker function, define a numeric length Offset or
use the Auto Length function to mathematically 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.
Remote control:
CALCulate<Chn>:FORMat GDELay
Aperture
Sets a delay aperture for the delay calculation. The aperture Qf is entered as an integer number of
Aperture Steps:
The analyzer calculates the aperture from the sweep points of the current frequency sweep.
Properties: The delay at each sweep point is computed as:
where the aperture Qf is a finite frequency interval around the sweep point f
o
and the analyzer measures
the corresponding phase change Qa.
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