[time-nuts] 10MHz to 32MHz?
Dr Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sat Apr 21 19:31:45 EDT 2007
John Miles wrote:
> One solution: double the 10 MHz twice to get 40 MHz, divide by 5 with any
> handy 74HC or 74F counter to get 8 MHz, and mix that with the 40 MHz signal
> to get 32 MHz and 48 MHz. Basic LC filtering should be adequate in the
> 10->40 MHz multiplier and the 32 MHz output sections.
> Another solution: drive an AD9852 DDS with the 10 MHz, and pick a
> clock-multiplier setting that gives the best SFDR near 32 MHz. That only
> requires two chips, but one of them would have to be a microcontroller.
> -- john, KE5FX
1) Divide the 10MHz by 5 with a synchronous counter configured for a 2:3
(or 3:2) mark spacer ratio for the 2 MHz signal.
2) Isolate the 16th harmonic with a bandpass filter
With a 2:3 mark space ratio the 5th, 10th, 15th harmonics of 2MHz will
have zero amplitude.
This leaves only the fundamental plus the 2nd, 3rd, 4th... 14th, 17th,
... harmonics to filter out.
However the amplitude of the 16th harmonic will only be about 1/16 of
that of the fundamental.
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