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Table 9. Test Port Input (Group Delay)
a
Description Supplemental Information (typ.)
Aperture (selectable) (frequency span)/(number of points -1)
Maximum Aperture
20% of frequency span
Range
0.5 x (1/minimum aperture)
Maximum Delay
Limited to measuring no more than 180° of phase
change within the minimum aperture.)
Accuracy
See graph below. Char.
The following graph shows characteristic group delay accuracy with full 2-port calibration and a 10 Hz IF
bandwidth. Insertion loss is assumed to be < 2 dB and electrical length to be ten meters.
For any S
ij
Group Delay measurement, S
ii
= 0, S
ij
= 1, S
ji
= 0, S
kl
= 0 for all kl ≠ ij
NOTE: The following graph also applies to the “C” model of the analyzer.
In general, the following formula can be used to determine the accuracy, in seconds, of specific group delay
measurement:
±Phase Accuracy (deg)/[360 × Aperture (Hz)]
Depending on the aperture and device length, the phase accuracy used is either incremental phase accuracy or
worst-case phase accuracy.
a
Group delay is computed by measuring the phase change within a specified frequency step (determined by the frequency span and the
number of points per sweep).
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