2-19
8753ET Specifications and Characteristics
Instrument Specifications
Table 2-17 General Information
8753ET General Information
Description Specification Supplemental Information
Group Delay
a
Aperture (selectable) (frequency span)/(number of
points − 1)
Maximum Aperture 20% of frequency span
Range 1/2 × (1/minimum aperture)
Maximum Delay Limited to measuring no more
than 180° of phase change
within the minimum aperture.
Accuracy See graph. Char.
The following graph shows group delay accuracy with 7-mm 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.
In general, the following formula can be used to determine the accuracy, in seconds, of specific
group delay measurement:
±Relative Phase Accuracy
b
(deg)/[360 × Aperture (Hz)]
Depending on the aperture and device length, the phase accuracy used is either phase dynamic
accuracy specification or worst case transmission uncertainty phase specification.
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).
b. Relative phase accuracy is an unspecified parameter. For very narrow apertures with
short devices under test RF systematic error terms can be assumed constant. As aperture
and/or device electrical length increase RF systematic errors become increasingly
important, eventually relative phase accuracy is the same as absolute phase accuracy.
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