[time-nuts] GPSDO simulation tool
Charles Steinmetz
csteinmetz at yandex.com
Sun Mar 23 16:45:34 EDT 2014
Jim wrote:
>Is a higher degree loop possible while maintaining stability?
Sure. PLL control loops (and other feedback loops) are often
designed out to fourth and fifth order. Very simply put, the
requirement is that the loop must have a reasonable phase margin at
the frequency where the gain reaches unity. For multiple open-loop
poles (where this condition would not be met), the usual solution is
to "give back" all but one pole by cancelling them with
high-frequency zeroes. All of this can give useful improvements in
loop gain at low- to mid-frequencies, at the cost of increased
complexity and greater sensitivity to component tolerances.
Best regards,
Charles
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