Cross-domain (Analog/Digital) Group Delay and Phase Measurement

Created on 2010-02-05 00:32:00

Question:

How can I use an APx analyzer to measure group delay and phase shift through an A/D or D/A converter?

Answer:

This may be done using the Continuous Sweep measurement. The group delay and phase are measured at the analyzer, using the generator as a reference. Because you may independently configure the generator outputs and analyzer inputs as digital or analog, cross-domain measurements can easily be performed. Group delay may be observed using the Impulse Response or Group Delay views, and phase may be seen in the Phase view (with the reference set to Absolute Phase).

When you want to measure phase between adjacent channels, use the Interchannel Phase measurement or the Continuous Sweep measurement's Phase view (with the reference set to Channel One).

Impulse Response view from the Continuous Sweep measurement in APx. The cursor marks the group delay through an A/D converter.

Group Delay view from the Continuous Sweep measurement in APx. The cursor marks the group delay through an A/D converter. Note the increase at low frequencies due to AC coupling in the ADC.