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Coherent Signals

Question asked by lockeba on Jul 24, 2013
Latest reply on Jul 25, 2013 by KennyG

In the attached tutorial, I see the quote below:


In fact, the only time the DDS output is an exact integer division of its system clocking frequency is when the

division factor is a power of two, 2N. Only then will the input clock and the output frequency be “phase-locked” or synchronized.”


Which made me wonder…what’s the difference between phase locked and coherent? 


I want to convince myself that if I put the reference clock on an Oscope and the output clock on an Oscope, the two may have different frequencies, but will not be drifting with respect to each other regardless of the frequency the DDS is synthesizing.  They will both appear stationary on the Oscope.  Is that true???