HP 8753E manual Group Delay, Deviation From Linear Phase Example Measurement

1.Follow the procedure in “Measuring Electrical Length.”

2.lb increase the scale resolution, press:

(m) ~~~~~~, md turn the front panel knob, or enter a v&e from the front pmel
keypad. .A...	....

3.To use the marker statistics to measure the maximum peak-to-peak deviation from linear phase, press:

.:::::..::::::::.:~:.::. ..:: ..:: :,.:.,.:::..;:., .,.:.

i

M a r k e r F c t n ~~.:~~~~~~ ,f!@@ ci.:,.... -1

”
STAT&	,088
i i	.‘...... i.:.:

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:

-A4/(360 * AF)

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