Group Delay; Deviation From Linear Phase Example Measurement - HP 8753E User Manual

1. Follow the procedure in "Measuring Electrical Length."
2.
. . . .
3. To use the marker statistics to measure the maximum peak-to-peak deviation from linear
phase, press:
M a r k e r F c t n ~~.:~~~~~~ ,f!@@
4. Activate and adjust the electrical delay to obtain a minimum peak-to-peak value.
Note It is possible to use delta markers to measure peak-to-peak deviation in only
one portion of the trace, see "lb Calculate the Statistics of the Measurement
Data" located earlier in this Chapter.
Figure 2-36. Deviation From Linear Phase Example Measurement

Group Delay

The phase linearity of many devices is specified in terms of group or envelope delay.
The analyzer can translate this information into a related parameter, group delay. Group
delay is the transmission time through your device under test as a function of frequency.
Mathematically, it is the derivative of the phase response which can be approximated by the
following ratio:
where A4 is the difference in phase at two frequencies separated by Al? The quantity AF is
commonly called the "aperture" of the measurement. The analyzer cakxrlates group delay from
its phase response measurements.
The default aperture is the total frequency span divided by the number of points across the
display (i.e. 201 points or 0.5% of the total span in this example).
1. Continue with the same instrument settings and measurements as in the previous procedure,
"Deviation from Linear Phase."
2. 'lb view the measurement in delay format, as shown in Figure 2-37, press:
Making Measurements 243