May I know what kind of problem would cause phase shifting in a PLL output? The output of the PLL always shift with respect to the Local oscillator signal
The amount of phase shift varies a with time...though the output frequency remains constant....
does not sound like the constant phase shift you have mentioned
"constant" can only mean "nearly constant" because - as a result of feedback action - the phase shift must swing around the target of 90 deg by a small amount which depends on the loop gain.
Therefore my question: How large is the unwanted phase shift ? Constant or not ?