[time-nuts] Square to sine wave symmetrical conversion

[Charles Steinmetz]

Bob wrote:

>In tis case the question is "do you *need* low harmonics in the oscillator
>stage to get low phase noise?"

Note that there are actually two questions.  One is WRT the phase 
noise of the oscillator itself, and the other WRT the phase noise of 
a system that integrates the oscillator.  In particular, even 
harmonics in the oscillator proper generate additional phase noise in 
the system when the signal is AC-coupled and/or DC-restored, and when 
it is fed to a zero-cross detector or other circuit that is sensitive 
to the symmetry of the waveform.

NIST published a paper on this.[1]  There is other research 
describing and quantifying the phenomenon, as well.

Best regards,

Charles


[1]  "The Effect of Harmonic Distortion on Phase errors in Frequency 
Distribution and Synthesis," Walls and 
Ascarrunz  <http://tf.nist.gov/timefreq/general/pdf/1437.pdf>