david wrote:
Given that slew rate is so critical, why do we distribute sine waves and perform the zero-crossing detection at every target instrument?
Magnus made some good points in response to your question. To elaborate a bit: it is much easier to provide a friendly transmission environment for a sine wave (single frequency), and sine waves are less sensitive to imperfections in the transmission environment (impedance discontinuities and mismatches, noise ingress, etc.). Reflections in the transmission environment will put funny steps in what started life as clean square waves or pulses, and differential phase shifts will also mis-shape square waves or pulses. This can even be a problem with sine waves -- see, for example, the NIST paper on the timing effects of distortion in sine wave sources for an example of the sensitivity of sine wave systems to harmonics (Walls and Ascarrunz, The Effect of Harmonic Distortion on Phase Errors in Frequency Distribution and Synthesis) -- but it is much worse with square waves or pulses.
Sine wave systems are also much less prone to radiating noise. Anyone who operates one or more frequency standards as well as sensitive RF receivers can testify that sine waves are much less of a hassle.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
