GUI Reference
R&S
®
ZNB/ZNBT
474
User Manual 1173.9163.02 ─ 38
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.
Calculation of Δf and ΔΦ
With n sweep steps the delay at sweep point no. m is calculated as follows:
●
If n is even (n = 2k), then Δf (m) = f (m+k) – f (m–k) and ΔΦ(m) = ΔΦ (m+k) – ΔΦ
(m–k).
●
If n is odd (n = 2k+1), then Δf (m) = f (m+k) – f (m–k–1) and ΔΦ (m) = ΔΦ (m+k) –
ΔΦ (m–k–1).
The calculated phase difference (and thus the group delay) is always assigned to the
frequency point no. m. For linear sweeps and odd numbers of aperture steps, the cen-
ter of the aperture range is [f (m+k) + f (m–k–1)] / 2 = f (m–1/2), i.e. half a frequency
step size below the sweep point f (m). This is why toggling from even to odd numbers
of aperture steps and back can virtually shift the group delay curve towards higher/
lower frequencies. It is recommended, to use even numbers of aperture steps, espe-
cially for large frequency step sizes.
Format Softtool
