Ref Level
Sets the reference level. It shows the max. power/level value displayed in the current
graticule. The reference level for S11 measurement is a fixed value 0 dBm and it
cannot be modified.
Aperture Step Width
The aperture step width k determines the value
for group delay . VNA can
measure S-parameters through the following formula. Frequency step , aperture
step width .
Group delay is obtained through differentiation calculation based on the phase of
S11 or S21 , then obtain the result by weight method through the factor
.
Wherein, indicates the aperture. The measurement accuracy of
group delay is determined by the aperture that you use. If it is too large, it will
affect the details; if it is too small, it will produce more noises. There is no standard
rule for aperture selection, and you can only rely on experience in choosing it.
Remarks:
S11 and S21 share the same aperture step width.
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