My question about these regenerative filters is that while I know F1 + F2 = Fin I'm still wondering how stable it is and how you know your divider will not do something like 10.0001 + 15.9999 = 26.000 for a few hours and then drift over to 9.9999 + 16.0001 = 26.000. In other words I can see how the filter keeps the sum locked to the 26.000 reference but I don't see how it keeps the 10Mhz component stable.
On Sun, Apr 17, 2011 at 3:16 AM, Magnus Danielson <[email protected]> wrote: > On 04/16/2011 10:50 PM, Bruce Griffiths wrote: >> >> Bruce Griffiths wrote: >>> >>> Oz-in-DFW wrote: >>>> >>>> On 4/9/2011 11:29 AM, Greg Broburg wrote: >>>>> >>>>> <deletia> >>>>> >>>>> I expect that I am missing something obvious here >>>>> a little nudge may help. >>>>> >>>>> Regards; >>>>> >>>>> Greg >>>>> >>>> What you are missing is that the concept only applies to small integer >>>> (2 or 3) division ratios and won't work as speculated here. It's sort >>>> of (long stretch here) like injection locking in reverse. If you want >>>> I'll try and post some links to papers later. >>>> >>> Nonsense, its already been done for much larger ratios and they need >>> not be integers. >>> Try simulating it. >>> >>> Bruce >>> >> One counter example to the simplistic statement about the operating mode >> of a regenerative divider being restricted to division by small integers >> only, is that such analysis appears to preclude the possibility of using >> a regenerative divider to produce a frequency comb. Unfortunately a >> regenerative divider has already been used to produce a low noise >> frequency comb where the comb frequency spacing is f/n(where f is the >> input frequency and n is an integer). Its possible to extract a >> frequency that is a rational fraction (m/n where m and n are integers) >> of the input frequency from such a regenerative frequency comb. Thus >> there is at least one method of using a regenerative divider to produce >> a 10MHz signal from a 26MHz signal. > > As I recall it, in the generalized regenerate divider where two frequencies > is filtered these match up > > http://tf.nist.gov/general/pdf/1800.pdf > > The two frequencies f1 and f2 has the sum of the input. This has the > side-consequence that > > f1 = fin - f2 > f2 = fin - f1 > > which is also the conversion steps that the phase will experience over two > turns around the loop. For synchronous operation the aggregate phase becomes > 0 degrees (modulus 360 degrees). > > Considering that fin = 26 MHz and f1 = 10 MHz we can conclude that f2 needs > to be 16 MHz. > > As for avoiding asynchronous operations the above NIST articles gives some > addtional hints on page 3, among which keeping the loop short is among the > important onces, essentially that the electrical delay length doesn't > support many modes. Keeping all traces on a normal PCB for 10 MHz and 26 MHz > should avoid that issue completely. > > This would form a 5f/13 - 8f/13 system since 2 MHz is the common frequency > for all of these. Keeping phase solutions unique for 2 MHz separation should > not be too hard. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- ===== Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
