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Entry  Sat Jan 22 02:11:09 2011, kiwamu, Update, Green Locking, some more progress 
    Reply  Sat Jan 22 02:23:26 2011, Koji, Update, Green Locking, some more progress 
Message ID: 4190     Entry time: Sat Jan 22 02:23:26 2011     In reply to: 4189
Author: Koji 
Type: Update 
Category: Green Locking 
Subject: some more progress 

What is the point to use the error instead of the feedback? It does not make sense to me.

If the cable is flaky why we don't solder it on the circuit? Why we don't put a buffer just after the test point?

It does not make sense to obtain the error signal in order to estimate the freeruning noise without the precise loop characterization.
(i.e. THE FEEDBACK LOOP TRINITY: Spectrum, Openloop, Calibration)

RA: I agree that feedback would be better because we could use it without much calibration. But the only difference between the "error signal" and the "feedback signal" in this case is a 1.6:40 pole:zero stage with DC gain of 0 dB. So we can't actually use either one without calibration and the gain between these two places is almost the same so they are both equally bad for the SNR of the measurement. I think that Suresh and Kiwamu are diligently reading about PLLs and will have a more quantitative result on Monday afternoon.

 

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